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ʻOumuamua

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ʻOumuamua
ʻOumuamua on 28 October 2017[a]
Discovery[2][3]
Discovered byRobert Weryk using Pan-STARRS 1
Discovery siteHaleakalā Obs., Hawaii
Discovery date19 October 2017
Designations
1I/2017 U1[4]
Pronunciation/oʊˌmuːəˈmuːə/, Hawaiian: [ʔowˈmuwəˈmuwə] ⓘ
Named after
Hawaiian term for scout[4]
  • 1I
  • 1I/ʻOumuamua
  • 1I/2017 U1 (ʻOumuamua)
  • A/2017 U1[5]
  • C/2017 U1[3]
  • P10Ee5V[6]
Orbital characteristics[7]
Epoch 23 November 2017 (JD 2458080.5)
Observation arc80 days
Perihelion0.255916±0.000007 AU
−1.2723±0.0001 AU[b]
Eccentricity1.20113±0.00002
  • 26.33±0.01 km/s (interstellar)[10]
  • 5.55 AU/year
51.158°
0° 41m 12.12s / day
Inclination122.74°
24.597°
241.811°
Earth MOID
  • 0.0958 AU
  • 37.3 LD
Jupiter MOID1.454 AU
Physical characteristics
Dimensions
Tumbling (non-principal axis rotation)[18]
Reported values include:
  • 0.1 (spectral est.)[16]
  • 0.06–0.08 (spectral est.)[20]
19.7 to >27.5[10][22][c]
22.08±0.45[7]

ʻOumuamua is the first interstellar object detected passing through the Solar System.[23] Formally designated 1I/2017 U1, it was discovered by Robert Weryk using the Pan-STARRS telescope at Haleakalā Observatory, Hawaii, on 19 October 2017, approximately 40 days after it passed its closest point to the Sun on 9 September. When it was first observed, it was about 33 million km (21 million mi; 0.22 AU) from Earth (about 85 times as far away as the Moon) and already heading away from the Sun.

ʻOumuamua is a small object estimated to be between 100 and 1,000 metres (300 and 3,000 ft) long, with its width and thickness both estimated between 35 and 167 metres (115 and 548 ft).[13] It has a red color, like objects in the outer Solar System. Despite its close approach to the Sun, it showed no signs of having a coma, the usual nebula around comets formed when they pass near the Sun. Further, it exhibited non‑gravitational acceleration, potentially due to outgassing or a push from solar radiation pressure.[24][25] It has a rotation rate similar to the Solar System's asteroids, but many valid models permit it to be unusually more elongated than all but a few other natural bodies observed in the solar system. This feature raised speculation about its origin. Its light curve, assuming little systematic error, presents its motion as "tumbling" rather than "spinning", and moving sufficiently fast relative to the Sun that it is likely of extrasolar origin. Extrapolated and without further deceleration, its path cannot be captured into a solar orbit, so it will eventually leave the Solar System and continue into interstellar space. Its planetary system of origin and age are unknown.

ʻOumuamua is remarkable for its extrasolar origin, high obliqueness, and observed acceleration without an apparent coma. By July 2019, most astronomers concluded that it was a natural object, but its precise characterization is contentious given the limited time window for observation. While an unconsolidated object (rubble pile) would require ʻOumuamua to be of a density similar to rocky asteroids,[26] a small amount of internal strength similar to icy comets[27] would allow it to have a relatively low density. Proposed explanations of its origin include the remnant of a disintegrated rogue comet,[28][29] or a piece of an exoplanet rich in nitrogen ice, similar to Pluto.[30][31][32] On 22 March 2023, astronomers proposed the observed acceleration was "due to the release of entrapped molecular hydrogen that formed through energetic processing of an H2O-rich icy body",[33] consistent with 'Oumuamua being an interstellar comet, "originating as a planetesimal relic broadly similar to solar system comets".[34]

In January 2022, researchers proposed that a spacecraft launched from Earth as part of Project Lyra, could catch up to 'Oumuamua in 26 years for closer studies.[35][36]

Naming

[edit]
Hyperbolic trajectory of ʻOumuamua through the inner Solar System with the Sun at the focus.[37]

As the first known object of its type, ʻOumuamua presented a unique case for the International Astronomical Union, which assigns designations for astronomical objects. Originally classified as comet C/2017 U1, it was later reclassified as asteroid A/2017 U1 due to the absence of a coma. Once it was unambiguously identified as coming from outside the Solar System, a new designation was created: I, for Interstellar object. As the first object so identified, ʻOumuamua was designated 1I, with rules for the eligibility of objects for I-numbers and the names to be assigned to these interstellar objects yet to be codified. The object may be called 1I; 1I/2017 U1; 1I/ʻOumuamua; or 1I/2017 U1 (ʻOumuamua).[4]

The name comes from Hawaiian ʻoumuamua 'scout'[38] (from ʻou 'reach out for' and mua, reduplicated for emphasis 'first, in advance of'[4]), and reflects the way the object is like a scout or messenger sent from the distant past to reach out to humanity. It roughly translates to 'first distant messenger'.[4][39] The first character (not a diacritic) is a Hawaiian ʻokina, not an apostrophe, and is pronounced as a glottal stop; the Pan-STARRS team chose the name[40] in consultation with Ka'iu Kimura and Larry Kimura of the University of Hawaiʻi at Hilo.[41]

Before the official name was decided, Rama was suggested, the name given to an alien spacecraft discovered under similar circumstances in the 1973 science fiction novel Rendezvous with Rama by Arthur C. Clarke.[42]

Observations

[edit]

Observations and conclusions concerning ʻOumuamua's trajectory were primarily obtained with data from the Pan-STARRS1 Telescope, part of the Spaceguard Survey,[43] and the Canada–France–Hawaii Telescope (CFHT), and its composition and shape from the Very Large Telescope and the Gemini South telescope in Chile,[44] and the Keck II telescope in Hawaii. These were collected by Karen J. Meech, Robert Weryk, and their colleagues and published in Nature on 20 November 2017.[45][46] After the announcement, the space-based telescopes Hubble and Spitzer joined in the observations.[47]

ʻOumuamua had faded into the 34th magnitude by 2020.

ʻOumuamua is small and not very luminous. It was not seen in STEREO HI-1A observations near its perihelion on 9 September 2017, limiting its brightness to approximately 13.5 mag.[20] By the end of October, it had already faded to about apparent magnitude 23,[48] and in mid-December 2017, it was too faint and fast-moving to be studied by even the largest ground-based telescopes.[44]

ʻOumuamua was compared to the fictional alien spacecraft Rama due to its interstellar origin. Adding to the coincidence, both the real and the fictional objects are unusually elongated.[49] ʻOumuamua has a reddish hue and unsteady brightness, which are typical of asteroids.[50][51][52]

The SETI Institute's radio telescope, the Allen Telescope Array, examined ʻOumuamua, but detected no unusual radio emissions.[53] More detailed observations, using the Breakthrough Listen hardware and the Green Bank Telescope, were performed;[49][53][54] the data were searched for narrowband signals and none were found. Given the close proximity to this interstellar object, limits were placed to putative transmitters with the extremely low effective isotropically radiated power of 0.08 watts.[55]

Trajectory

[edit]
Seen from Earth, the apparent trajectory makes annual retrograde loops in the sky, with its origin in Lyra, temporarily moving south of the ecliptic between 2 September and 22 October 2017, and moving northward again towards its destination in Pegasus.
ʻOumuamua's hyperbolic trajectory over the Solar System.

ʻOumuamua appears to have come from roughly the direction of Vega in the constellation Lyra.[50][51][56][57] Its incoming direction of motion is 6° from the solar apex (the direction of the Sun's movement relative to local stars), the most likely direction from which objects from outside the Solar System would come.[56][58] On 26 October, two precovery observations from the Catalina Sky Survey were found dated 14 and 17 October.[59][48] A two-week observation arc had verified a strongly hyperbolic trajectory.[7][45] It has a hyperbolic excess velocity (velocity at infinity, ) of 26.33 km/s (94,800 km/h; 58,900 mph), its speed relative to the Sun when in interstellar space.[d]

ʻOumuamua speed relative to the Sun
Distance Date Velocity
km/s
2300 AU 1606 26.41[60]
1000 AU 1839 26.42
100 AU 2000 26.73
10 AU 2016 29.56
1 AU 9 August 2017 49.70[61]
Perihelion 9 September 2017 87.71[10]
1 AU 10 October 2017 49.70[e]
10 AU 2019 29.58
100 AU 2034 26.73[62]
1000 AU 2195 26.44
2300 AU 2429 26.40[63]

By mid-November, astronomers were certain that it was an interstellar object.[64] Based on observations spanning 80 days, ʻOumuamua's orbital eccentricity is 1.20, the highest ever observed[65][10] until 2I/Borisov was discovered in August 2019. An eccentricity exceeding 1.0 means an object exceeds the Sun's escape velocity, is not bound to the Solar System, and may escape to interstellar space. While an eccentricity slightly above 1.0 can be obtained by encounters with planets, as happened with the previous record holder, C/1980 E1,[65][66][f] ʻOumuamua's eccentricity is so high that it could not have been obtained through an encounter with any of the planets in the Solar System. Even undiscovered planets in the Solar System cannot account for ʻOumuamua's trajectory or boost its speed to the observed value. For these reasons, it can only be of interstellar origin.[67][68]

Animation of ʻOumuamua passing through the Solar System
Inbound velocity at 200 AU from the Sun
compared to Oort cloud objects
Object Velocity
km/s		 # of observations
and obs arc[g]
90377 Sedna 2.66[69] 483 in 11796 days
C/2010 X1 (Elenin) 2.96 2222 in 235 days
C/1980 E1 (Bowell) 2.98[70] 187 in 2514 days
C/1997 P2 (Spacewatch) 2.99 94 in 49 days
C/2012 S1 (ISON) 2.99[71] 6514 in 784 days
C/2008 J4 (McNaught) 4.87[72] 22 in 15 days[h]
1I/2017 U1 (ʻOumuamua) 26.55[73] 207 in 80 days
2I/Borisov 32.43[74] 1428 in 311 days

ʻOumuamua entered the Solar System from north of the plane of the ecliptic. The pull of the Sun's gravity caused it to speed up until it reached its maximum speed of 87.71 km/s (315,800 km/h; 196,200 mph) as it passed south of the ecliptic on 6 September, where the Sun's gravity bent its orbit in a sharp turn northward at its closest approach (perihelion) on 9 September at a distance of 0.255 AU (38,100,000 km; 23,700,000 mi) from the Sun, i.e., about 17% closer than Mercury's closest approach to the Sun.[75][10][i] It is now heading away from the Sun toward Pegasus, toward a vanishing point 66° from the direction of its approach.[j]

On the outward leg of its journey through the Solar System, ʻOumuamua passed beyond the orbit of Earth on 14 October with a closest approach distance of approximately 0.16175 AU (24,197,000 km; 15,036,000 mi) from Earth.[7] On 16 October it moved back north of the ecliptic plane and passed beyond the orbit of Mars on 1 November.[75][56][7] It passed beyond Jupiter's orbit in May 2018, beyond Saturn's orbit in January 2019, and beyond Neptune's in 2022.[75] As it leaves the Solar System it will be approximately right ascension 23'51" and declination +24°42', in Pegasus.[10] It will continue to slow down until it reaches a speed of 26.33 kilometres per second (94,800 km/h; 58,900 mph) relative to the Sun, the same speed it had before its approach to the Solar System.[10]

Non-gravitational acceleration

[edit]

On 27 June 2018, astronomers reported a non-gravitational acceleration to ʻOumuamua's trajectory, potentially consistent with a push from solar radiation pressure.[77][78] The resulting change in velocity during the period when it was near its closest approach to the Sun summed to about 17 meters per second. Initial speculation as to the cause of this acceleration pointed to the comet-like outgassing,[25] whereby volatile substances inside the object evaporate as the Sun heats its surface. Although no such tail of gasses was observed following the object,[79] researchers estimated that enough outgassing may have increased the object's speed without the gases being detectable.[80] A critical reassessment of the outgassing hypothesis argued that, instead of the observed stability of ʻOumuamua's spin, outgassing would have caused its spin to rapidly change due to its elongated shape, resulting in the object tearing apart.[8]

Indications of origin

[edit]

Accounting for Vega's proper motion, it would have taken ʻOumuamua 600,000 years to reach the Solar System from Vega.[45] But as a nearby star, Vega was not in the same part of the sky at that time.[56] Astronomers calculate that 100 years ago the object was 83.9 ± 0.090 billion km; 52.1 ± 0.056 billion mi (561 ± 0.6 AU) from the Sun and traveling at 26.33 km/s with respect to the Sun.[10] This interstellar speed is very close to the mean motion of material in the Milky Way in the neighborhood of the Sun, also known as the local standard of rest (LSR), and especially close to the mean motion of a relatively close group of red dwarf stars. This velocity profile also indicates an extrasolar origin, but appears to rule out the closest dozen stars.[81] In fact, the closeness of ʻOumuamua's velocity to the local standard of rest might mean that it has circulated the Milky Way several times and thus may have originated from an entirely different part of the galaxy.[45]

It is unknown how long the object has been traveling among the stars.[75] The Solar System is likely the first planetary system ʻOumuamua has closely encountered since being ejected from its birth star system, potentially several billion years ago.[82][45] It has been speculated that the object may have been ejected from a stellar system in one of the local kinematic associations of young stars (specifically, Carina or Columba) within a range of about 100 parsecs,[83] 45 million years ago.[84] The Carina and Columba associations are now very far in the sky from the Lyra constellation, the direction from which ʻOumuamua came when it entered the Solar System. Others have speculated that it was ejected from a white dwarf system and that its volatiles were lost when its parent star became a red giant.[85] About 1.3 million years ago the object may have passed within a distance of 0.16 parsecs (0.52 light-years) to the nearby star TYC 4742-1027-1, but its velocity is too high to have originated from that star system, and it probably just passed through the system's Oort cloud at a relative speed of about 15 km/s (34,000 mph; 54,000 km/h).[86][k] An August 2018 study using Gaia Data Release 2 updated the possible past close encounters and identified four stars—HIP 3757, HD 292249, Gaia DR2 2502921019565490176, and Gaia DR2 3666992950762141312—which ʻOumuamua passed relatively close to at moderately low velocities in the past few million years.[87] This study also identifies future close encounters of ʻOumuamua on its outgoing trajectory from the Sun.[88]

In September 2018, astronomers described several possible home star systems from which ʻOumuamua may have originated.[89][90]

In April 2020, astronomers presented a new possible scenario for the object's origin.[91][92] According to one hypothesis, ʻOumuamua could be a fragment from a tidally disrupted planet.[93][l] If true, this would make ʻOumuamua a rare object, of a type much less abundant than most extrasolar "dusty-snowball" comets or asteroids. But this scenario leads to cigar-shaped objects, whereas ʻOumuamua's lightcurve favors a disc-like shape.[11]

In May 2020, it was proposed that the object was the first observed member of a class of small H2-ice-rich bodies that form at temperatures near 3 K in the cores of giant molecular clouds. The non-gravitational acceleration and high aspect ratio shape of ʻOumuamua might be explainable on this basis.[94] However, it was later calculated that hydrogen icebergs cannot survive their journey through interstellar space.[95]

Classification

[edit]

Initially, ʻOumuamua was announced as comet C/2017 U1 (PANSTARRS) based on a strongly hyperbolic trajectory.[3] In an attempt to confirm any cometary activity, very deep stacked images were taken at the Very Large Telescope later the same day, but the object showed no presence of a coma.[m] Accordingly, the object was renamed A/2017 U1, becoming the first comet ever to be re-designated as an asteroid.[5] Once it was identified as an interstellar object, it was designated 1I/2017 U1, the first member of a new class of objects.[4] The lack of a coma limits the amount of surface ice to a few square meters, and any volatiles (if they exist) must lie below a crust at least 0.5 m (1.6 ft) thick.[16] It also indicates that the object must have formed within the frost line of its parent stellar system or have been in the inner region of that stellar system long enough for all near-surface ice to sublimate, as may be the case with damocloids.[citation needed] It is difficult to say which scenario is more likely due to the chaotic nature of small body dynamics,[citation needed] although if it formed in a similar manner to Solar System objects, its spectrum indicates that the latter scenario is true. Any meteoric activity from ʻOumuamua would have been expected to occur on 18 October 2017 coming from the constellation Sextans, but no activity was detected by the Canadian Meteor Orbit Radar.[82]

On 27 June 2018, astronomers reported that ʻOumuamua was thought to be a mildly active comet, and not an asteroid, as previously thought. This was determined by measuring a non-gravitational boost to ʻOumuamua's acceleration, consistent with comet outgassing.[25][96][80][97] However, studies submitted in October 2018 suggest that the object is neither an asteroid nor a comet,[8][9] although the object could be a remnant of a disintegrated interstellar comet (or exocomet), as suggested by astronomer Zdenek Sekanina.[28][29]

Appearance, shape and composition

[edit]

Spectra from the Hale Telescope on 25 October showed red color resembling comet nuclei or Trojans.[82] Higher signal to noise spectra recorded by the 4.2 m (14 ft) William Herschel Telescope later that day showed that the object was featureless, and colored red like Kuiper belt objects.[98] Spectra obtained with the 8.2 m (27 ft) Very Large Telescope the following night showed that behavior continued into near-infrared wavelengths.[99] Its spectrum is similar to that of D-type asteroids.[16]

Light curve from 25 to 27 October 2017 with dotted line from a model with 10:1 elongation

ʻOumuamua is not rotating around its principal axis, and its motion may be a form of tumbling.[18][100] This accounts for the various rotation periods reported, such as 8.10 hours (±0.42 hours[20] or ±0.02 hours[19]) by Bannister et al. and Bolin et al. with a lightcurve amplitude of 1.5–2.1 magnitudes,[19] whereas Meech et al. reported a rotation period of 7.3 hours and a lightcurve amplitude of 2.5 magnitudes.[101][n] Most likely, ʻOumuamua was set tumbling by a collision in its system of origin, and remains tumbling since the time scale for dissipation of this motion is very long, at least a billion years.[18][102]

Simulation of ʻOumuamua spinning and tumbling through space, and the resultant light curve. In reality, observations of ʻOumuamua detect the object as a single pixel – its shape here has been inferred from the light curve

The large variations on the light curves indicate that ʻOumuamua may be anything from a highly elongated cigar-like object, comparable to or greater than the most elongated Solar System objects,[20][19] to an extremely flat object, a pancake or oblate spheroid.[103] However, the size and shape have not been directly observed as ʻOumuamua appears as nothing more than a point source of light even in the most powerful telescopes. Neither its albedo nor its triaxial ellipsoid shape is known. If cigar-shaped, the longest-to-shortest axis ratio could be 5:1 or greater.[18] Assuming an albedo of 10% (slightly higher than typical for D-type asteroids[104]) and a 6:1 ratio, ʻOumuamua has dimensions of approximately 100 m–1,000 m × 35 m–167 m × 35 m–167 m (328 ft–3,281 ft × 115 ft–548 ft × 115 ft–548 ft)[13][14][15][16][17] with an average diameter of about 110 m (360 ft).[16][17] According to astronomer David Jewitt, the object is physically unremarkable except for its highly elongated shape.[17] Bannister et al. have suggested that it could also be a contact binary,[20] although this may not be compatible with its rapid rotation.[46] One speculation regarding its shape is that it is a result of a violent event (such as a collision or stellar explosion) that caused its ejection from its system of origin.[46] JPL News reported that ʻOumuamua "is up to one-quarter mile (400 meters) long and highly-elongated — perhaps 10 times as long as it is wide".[47][105]

Artist's impression of ʻOumuamua

A 2019 paper finds the best models as either a cigar-shape, 1:8 aspect ratio, or disc-shape, 1:6 aspect ratio, with the disc more likely since its rotation does not require a specific orientation to see the range of brightnesses observed.[106] Monte Carlo simulations based on the available orbit determination suggest that the equatorial obliquity of ʻOumuamua could be about 93 degrees, if it has a very prolate or cigar-like shape, or close to 16 degrees, if it is very oblate or disk-like.[107] A 2021 paper proposed that, if 'Oumuamua is made of nitrogen ice, the extreme shape could be a result of recent evaporation, and that when the object entered the Solar System it likely had an unremarkable 2:1 aspect ratio. The authors calculated that in this scenario, a month after perihelion, that ʻOumuamua had lost 92% of the mass it had upon entering the Solar System.[30]

Light curve observations suggest however that the object may be composed of dense metal-rich rock that has been reddened by millions of years of exposure to cosmic rays.[46][108][109] It is thought that its surface contains tholins, which are irradiated organic compounds that are more common in objects in the outer Solar System and can help determine the age of the surface.[110][111] This possibility is inferred from spectroscopic characterization and its reddish color,[110][99] and from the expected effects of interstellar radiation.[99] Despite the lack of any cometary coma when it approached the Sun, it may still contain internal ice, hidden by "an insulating mantle produced by long-term cosmic ray exposure".[99]

In November 2019, some astronomers noted that ʻOumuamua may be a "cosmic dust bunny", due to its "very lightweight and 'fluffy' conglomerate of dust and ice grains".[112][113][114] In August 2020, astronomers reported that ʻOumuamua is not likely to have been composed of frozen hydrogen, which had been proposed earlier; the compositional nature of the object continues to be unknown.[115][116]

Radio measurements

[edit]

In December 2017, astronomer Avi Loeb of Harvard University, an adviser to the Breakthrough Listen Project, cited ʻOumuamua's unusually elongated shape as one reason the Green Bank Telescope in West Virginia would listen for radio emissions from it to see if there were any unexpected signs that it might be of artificial origin,[105] although earlier limited observations by other radio telescopes such as the SETI Institute's Allen Telescope Array had produced no such results.[53] On 13 December 2017, the Green Bank Telescope observed the object for six hours across four bands of radio frequency. No radio signals from ʻOumuamua were detected in this very limited scanning range, but more observations were planned.[117][118][needs update]

Discussion

[edit]

Nitrogen ice theory

[edit]

Outgassing of nitrogen ice (N2) could explain why no outgassing was detected. Nitrogen ice the size of 'Oumuamua could survive for 500 million years in the interstellar medium and would reflect two-thirds of the Sun's light.[119] This explanation has been further supported in March 2021 when scientists presented a theory based on nitrogen ice, and further concluded that ʻOumuamua may be a piece of an exoplanet similar to the dwarf planet Pluto, an exo-Pluto as noted, from beyond our solar system.[120][30][31][32] This theory has been criticized by Loeb.[121][122] In November 2021, theoretical studies by Siraj and Loeb hypothesized that 'Oumuamua was not a nitrogen iceberg.[123][122]

Hydrogen ice theory

[edit]

It has been proposed that ʻOumuamua contains a significant amount of hydrogen ice.[124][125] This would point to it originating from the core of an interstellar molecular cloud, where conditions for the formation of this material might exist.[126] The Sun's heat would cause the hydrogen to sublime, which would in turn propel the body. The hydrogen coma formed by this process would be difficult to detect from Earth-based telescopes, as the atmosphere blocks those wavelengths.[127] Regular water-ice comets undergo this as well, however to a much lesser extent and with a visible coma. This may explain the significant non-gravitational acceleration that ʻOumuamua underwent without showing signs of coma formation. Significant mass loss caused by the sublimation would also explain the unusual cigar-like shape, comparable to how a bar of soap becomes more elongated as it is used up.

However, it was later shown that hydrogen icebergs cannot form out of small grains and that, to not evaporate during their journey in interstellar space, they would have had to have been formed about 40 million years ago, in the close neighborhood of the solar system.[128][129]

Hydrogen-laden water ice theory

[edit]

In 2023, it was proposed the observed non-gravitational acceleration and spectrum of ʻOumuamua can be best explained by hydrogen outgassing from the water ice matrix. The buildup of the hydrogen in the water ice is expected to happen in the interstellar comets, due to low-temperature water ice radiolysis by cosmic ray particles while ʻOumuamua or similar cometary body was in interstellar space.[130][33]

Hypothetical space missions

[edit]
Main article: Project Lyra

The Initiative for Interstellar Studies (i4is) launched Project Lyra to assess the feasibility of a mission to ʻOumuamua.[131] Several options for sending a spacecraft to ʻOumuamua within a time-frame of 5 to 25 years were suggested.[132][133] Different mission durations and their velocity requirements were explored with respect to the launch date, assuming direct impulsive transfer to the intercept trajectory.[citation needed]

Main article: Interstellar object § Hypothetical missions

The Space Launch System (also being looked at for "interstellar precursor missions") would be even more capable.[134][135] Such an interstellar precursor could easily pass by ʻOumuamua on its way out of the Solar System, at speeds of 63 km/s (39 mi/s).[136][137]

More advanced options of using solar, laser electric, and laser sail propulsion, based on Breakthrough Starshot technology, have also been considered. The challenge is to get to the interstellar object in a reasonable amount of time (and so at a reasonable distance from Earth), and yet be able to gain useful scientific information. To do this, decelerating the spacecraft at ʻOumuamua would be "highly desirable, due to the minimal science return from a hyper-velocity encounter".[58] If the investigative craft goes too fast, it would not be able to get into orbit or land on the object and would fly past it. The authors conclude that, although challenging, an encounter mission would be feasible using near-term technology.[58][131] Seligman and Laughlin adopt a complementary approach to the Lyra study but also conclude that such missions, though challenging to mount, are both feasible and scientifically attractive.[138]

Technosignature hypothesis

[edit]

On 26 October 2018, Loeb and his postdoc, Shmuel Bialy, submitted a paper exploring the possibility of ʻOumuamua being an artificial thin solar sail[139][140] accelerated by solar radiation pressure, in an effort to help explain the object's comet-like non-gravitational acceleration.[77][78][141] Other scientists have stated that the available evidence is insufficient to consider such a premise,[142][143][144] and that a tumbling solar sail would not be able to accelerate.[145] In response, Loeb wrote an article detailing six anomalous properties of ʻOumuamua that make it unusual, unlike any comets or asteroids seen before.[146][147] A subsequent report on observations by the Spitzer Space Telescope set a tight limit on cometary outgassing of any carbon-based molecules and indicated that ʻOumuamua is at least ten times shinier than a typical comet.[79] The solar sail technosignature hypothesis is considered unlikely by many experts owing to available simpler explanations that align with the expected characteristics of interstellar asteroids and comets.[148][129][149]

Other interstellar objects

[edit]
Main article: Interstellar object

2I/Borisov was discovered on 30 August 2019, and was soon confirmed to be an interstellar comet. Arriving from the direction of Cassiopeia, the object arrived at perihelion (closest point to the Sun) on 8 December 2019.

Other proposed interstellar objects include the meteors CNEOS 2014-01-08[150] and CNEOS 2017-03-09 that impacted Earth in 2014[151][152][153][154] and 2017, respectively,[155] although these claims have been met with skepticism.[156]

See also

[edit]

Notes

[edit]
  1. ^ 5-minute exposure taken by the William Herschel Telescope on 28 October; ʻOumuamua appears as a light source in the center of the image, while background stars appear streaked due to the speed of ʻOumuamua as the telescope tracked it.[1]
  2. ^ Objects on hyperbolic trajectories have negative semimajor axis, giving them a positive orbital energy.
  3. ^ Range at which the object was expected to be observable. Brightness peaked at 19.7 mag on 18 October 2017, and faded below 27.5 mag (the limit of Hubble Space Telescope for fast-moving objects) around 1 January 2018. By late 2019, it should have dimmed to 34 mag.
  4. ^ For comparison, comet C/1980 E1 will only be moving 4.2 km/s when it is 500 AU from the Sun.
  5. ^ The solar escape velocity from Earth's orbit (1 AU from the Sun) is 42.1 km/s. For comparison, even 1P/Halley moves at 41.5 km/s when 1 AU from the Sun, according to the formula v = 42.1219 √1/r − 0.5/a, where r is the distance from the Sun, and a is the major semi-axis. Near-Earth asteroid 2062 Aten only moves at 29 km/s when 1 AU from the Sun because of the much smaller semi-major axis.
  6. ^ Unlike ʻOumuamua, C/1980 E1's orbit got its high eccentricity of 1.057 due to a close encounter with Jupiter. Its inbound-orbit eccentricity was less than 1.[56]
  7. ^ Orbits computed with only a handful of observations can be unreliable. Short arcs can result in computer generated orbits rejecting some data unnecessarily.
  8. ^ JPL #10 shows that on 1855-Mar-24 C/2008 J4 was moving 4.88±1.8 km/s.
  9. ^ Comet C/2012 S1 (ISON) peaked at 377 km/s (1,360,000 km/h) at perihelion[76] because it passed 0.0124 AU from the Sun (20 times closer than ʻOumuamua).
  10. ^ According to the formula:
  11. ^ This is true for the nominal position of the star. However, its actual distance is not known precisely: According to Gaia Data Release 1, the distance to TYC4742-1027-1 is 137 ± 13 parsecs (447 ± 42 light-years). It is not known if an encounter actually occurred. Update: This star has new measurements in Gaia Data Release 2, and an origins study based on this by Bailer-Jones et al. (2018) shows that TYC4742-1027-1 did not come within 2 pc of ʻOumuamua.
  12. ^ See also Ravikov, Roman R. (2018). "1I/2017 ʻOumuamua-like Interstellar Asteroids as Possible Messengers from Dead Stars". The Astrophysical Journal. 861: 35. arXiv:1801.02658. doi:10.3847/1538-4357/aac5ef.. ʻOumuamua is a fragment of a white-dwarf-star tidal-disruption-event. This easily explains its 6:1 or 10:1 elongation and its "refractory" composition; containing probably nickel-iron, possibly other metals, too.
  13. ^ According to Central Bureau for Astronomical Telegrams's CBET 4450, none of the observers had detected any sign of cometary activity. The initial classification as a comet was based on the object's orbit.
  14. ^ 1865 Cerberus has a lightcurve amplitude of 2.3 magnitudes.

References

[edit]
  1. ^ Bonnell, Jerry; Nemiroff, Robert (3 November 2017). "A/2017 U1: An Interstellar Visitor". Astronomy Picture of the Day. Archived from the original on 13 March 2019. Retrieved 13 March 2019. A point of light centered in this 5 minute exposure recorded with the William Herschel Telescope in the Canary Islands on October 28 ... Faint background stars appear streaked because the massive 4.2 meter diameter telescope is tracking the rapidly moving A/2017 U1 in the field of view.
  2. ^ "Small Asteroid or Comet 'Visits' from Beyond the Solar System". NASA. 26 October 2017. Archived from the original on 2 December 2017. Retrieved 29 October 2017.
  3. ^ a b c "MPEC 2017-U181: COMET C/2017 U1 (PANSTARRS)". Minor Planet Center. International Astronomical Union. 25 October 2017. Archived from the original on 25 October 2017. Retrieved 25 October 2017. (CK17U010)
  4. ^ a b c d e f g "MPEC 2017-V17: New Designation Scheme for Interstellar Objects". Minor Planet Center. International Astronomical Union. 6 November 2017. Archived from the original on 8 January 2020. Retrieved 6 November 2017.
  5. ^ a b "MPEC 2017-U183: A/2017 U1". Minor Planet Center. International Astronomical Union. 25 October 2017. Archived from the original on 26 October 2017. Retrieved 25 October 2017. (AK17U010)
  6. ^ Antier, K. (30 October 2017). "A/2017 U1, first interstellar asteroid ever detected!". International Meteor Organization. Archived from the original on 7 November 2017. Retrieved 7 November 2017.
  7. ^ a b c d e f "JPL Small-Body Database Browser: ʻOumuamua (A/2017 U1)". JPL Small-Body Database. Jet Propulsion Laboratory. Archived from the original on 21 January 2021. Retrieved 19 March 2021.
    JPL 1 (Solution date: 2017-Oct-24)
    JPL 10 (Solution date: 2017-Nov-03)
    JPL 14 (Solution date: 2017-Nov-21)
    JPL 16 (Solution date: 2018-Jun-26
  8. ^ a b c Rafikov, Roman R. (20 September 2018). "Spin Evolution and Cometary Interpretation of the Interstellar Minor Object 1I/2017 ʻOumuamua". arXiv:1809.06389v2 [astro-ph.EP].
  9. ^ a b Skibba, Ramin (10 October 2018). "Interstellar Visitor Found to Be Unlike a Comet or an Asteroid". Quanta Magazine. Archived from the original on 27 April 2020. Retrieved 10 October 2018.
  10. ^ a b c d e f g h "Pseudo-MPEC for A/2017 U1 (FAQ File)". Bill Gray of Project Pluto. 26 October 2017. Archived from the original on 26 October 2017. Retrieved 26 October 2017. (Orbital elements) Archived 30 September 2018 at the Wayback Machine
  11. ^ a b Mashchenko, S. (2019). "Modeling the light curve of 'Oumuamua: evidence for torque and disc-like shape". Monthly Notices of the Royal Astronomical Society. 489 (3): 3003–3021. arXiv:1906.03696. Bibcode:2019MNRAS.489.3003M. doi:10.1093/mnras/stz2380. S2CID 182952355.
  12. ^ Jewitt, D.; Seligman, D. (September 2022). "Interstellar Interlopers". arXiv:2209.08182 [astro-ph.EP].
  13. ^ a b c Cofield, Calia (14 November 2018). "NASA Learns More About Interstellar Visitor 'Oumuamua". NASA. Archived from the original on 15 April 2020. Retrieved 14 November 2018.
  14. ^ a b Watzke, Megan (20 October 2018). "Spitzer Observations of Interstellar Object ʻOumuamua". SciTechDaily.com. Archived from the original on 16 October 2019. Retrieved 20 October 2018.
  15. ^ a b "'Oumuamua". Smithsonian Astrophysical Observatory. 19 October 2018. Archived from the original on 1 February 2021. Retrieved 24 October 2019.
  16. ^ a b c d e f g h i Jewitt, D.; Luu, J.; Rajagopal, J.; Kotulla, R.; Ridgway, S.; Liu, W.; Augusteijn, T. (30 November 2017). "Interstellar Interloper 1I/2017 U1: Observations from the NOT and WIYN Telescopes". The Astrophysical Journal Letters. 850 (2): L36. arXiv:1711.05687. Bibcode:2017ApJ...850L..36J. doi:10.3847/2041-8213/aa9b2f. S2CID 32684355.
  17. ^ a b c d e "A Familiar-Looking Messenger from Another Solar System" (Press release). National Optical Astronomy Observatory. 15 November 2017. NOAO 17-06. Archived from the original on 16 November 2017. Retrieved 15 November 2017.
  18. ^ a b c d Fraser, W. C.; Pravec, P.; Fitzsimmons, A.; Lacerda, P.; Bannister, M. T.; Snodgrass, C.; Smolić, I. (9 February 2018). "The tumbling rotational state of 1I/ʻOumuamua". Nature Astronomy. 2 (5): 383–386. arXiv:1711.11530. Bibcode:2018NatAs...2..383F. doi:10.1038/s41550-018-0398-z. S2CID 119353074. Archived from the original on 3 September 2018. Retrieved 3 September 2018.
  19. ^ a b c d Bolin, B.T.; et al. (2017). "APO Time Resolved Color Photometry of Highly-Elongated Interstellar Object 1I/ʻOumuamua". The Astrophysical Journal. 852 (1): L2. arXiv:1711.04927. Bibcode:2018ApJ...852L...2B. doi:10.3847/2041-8213/aaa0c9. S2CID 118894742.
  20. ^ a b c d e f g h i Bannister, M.T.; Schwamb, M.E. (2017). "Col-OSSOS: Colors of the Interstellar Planetesimal 1I/2017 U1 in Context with the Solar System". The Astrophysical Journal. 851 (2): L38. arXiv:1711.06214. Bibcode:2017ApJ...851L..38B. doi:10.3847/2041-8213/aaa07c. S2CID 56264680. As its albedo is unknown, we do not describe 1I/ʻOumuamua as consistent with Tholen (1984) P type.
  21. ^ Feng, F. & Jones, H. R. A. (23 November 2017). "ʻOumuamua as a messenger from the Local Association". The Astrophysical Journal. 852 (2): L27. arXiv:1711.08800. Bibcode:2018ApJ...852L..27F. doi:10.3847/2041-8213/aaa404. S2CID 56197486.
  22. ^ Meech, Karen; et al. (8 November 2017). "Proposal 15405 – Which way home? Finding the origin of our Solar System's first interstellar visitor" (PDF). STScI – Space Telescope Science Institute. Retrieved 15 November 2017.
  23. ^ Osborne, Hannah (16 April 2019). "First meteor of interstellar origin discovered by scientists". Newsweek. Retrieved 11 April 2022.
  24. ^ Carlisle, Camille M. (12 March 2019). "'Oumuamua sped up as it left the inner solar system. This may be why – Astronomers think a jet-powered rocking motion could solve the puzzle". Salon. Archived from the original on 19 March 2020. Retrieved 12 March 2019.
  25. ^ a b c Micheli, M.; et al. (2018). "Non-gravitational acceleration in the trajectory of 1I/2017 U1 (ʻOumuamua)". Nature. 559 (7713): 223–226. Bibcode:2018Natur.559..223M. doi:10.1038/s41586-018-0254-4. PMID 29950718. S2CID 49477508.
  26. ^ McNeill, Andrew; Trilling, David E.; Mommert, Michael (1 April 2018). "Constraints on the Density and Internal Strength of 1I/'Oumuamua". The Astrophysical Journal Letters. 857 (1): L1. arXiv:1803.09864. Bibcode:2018ApJ...857L...1M. doi:10.3847/2041-8213/aab9ab. ISSN 0004-637X. S2CID 56163074.
  27. ^ Shi, X.; Vincent, J-B.; Tubiana, C.; Toth, I.; Pajola, M.; Oklay, N.; Naletto, G.; Mottola, S.; Marzari, F. (1 March 2018). "Tensile strength of 67P/Churyumov–Gerasimenko nucleus material from overhangs". Astronomy & Astrophysics. 611: A33. arXiv:1712.07508. Bibcode:2018A&A...611A..33A. doi:10.1051/0004-6361/201732155. ISSN 0004-6361. S2CID 44120504.
  28. ^ a b Williams, Matt (1 February 2019). "Oumuamua Could be the Debris Cloud of a Disintegrated Interstellar Comet". Universe Today. Archived from the original on 3 February 2019. Retrieved 2 February 2019.
  29. ^ a b Sekanina, Zdenek (31 January 2019). "1I/'Oumuamua As Debris Of Dwarf Interstellar Comet That Disintegrated Before Perihelion". arXiv:1901.08704 [astro-ph.EP].
  30. ^ a b c Jackson, Alan P.; et al. (16 March 2021). "1I/'Oumuamua as an N2 ice fragment of an exo-Pluto surface: I. Size and Compositional Constraints". Journal of Geophysical Research: Planets. 126 (5). arXiv:2103.08788. Bibcode:2021JGRE..12606706J. doi:10.1029/2020JE006706.
  31. ^ a b Desch, S. J.; et al. (16 March 2021). "1I/'Oumuamua as an N2 ice fragment of an exo-Pluto surface II: Generation of N2 ice fragments and the origin of 'Oumuamua". Journal of Geophysical Research: Planets. 126 (5). arXiv:2103.08812. Bibcode:2021JGRE..12606807D. doi:10.1029/2020JE006807.
  32. ^ a b Overbye, Dennis (23 March 2021). "Why Oumuamua, the Interstellar Visitor, Looks Eerily Familiar – A piece of an extrasolar Pluto may have passed through our cosmic neighborhood, a new study suggests". The New York Times. Retrieved 23 March 2021.
  33. ^ a b Bergner, Jennifer; Seligman, Darryl Z. (22 March 2023). "Acceleration of 1I/'Oumuamua from radiolytically produced H2 in H2O ice". Nature. 615 (7953): 610–613. arXiv:2303.13698. doi:10.1038/s41586-022-05687-w. PMID 36949336. S2CID 257668585. Retrieved 23 March 2023.
  34. ^ Overbye, Dennis (22 March 2023). "Oumuamua Was a Comet After All, a Study Suggests – Astronomers offer 'a surprisingly simple explanation' for the curious behavior of the interstellar visitor in 2017". The New York Times. Retrieved 23 March 2023.
  35. ^ Williams, Matt (20 January 2022). "If Launched by 2028, a Spacecraft Could Catch up With Oumuamua in 26 Years". Universe Today. Retrieved 27 January 2022.
  36. ^ Hibberd, Adam; et al. (11 January 2022). "Project Lyra: A mission to 1I/'Oumuamua without Solar Oberth Manoeuvre". Acta Astronautica. 199: 161–165. arXiv:2201.04240. Bibcode:2022AcAau.199..161H. doi:10.1016/j.actaastro.2022.07.032. S2CID 245877397.
  37. ^ NASA. "animation".
  38. ^ Pukui, M.K.; Elbert, S.H. (2003). "Hawaiian Dictionary". Ulukau: Hawaiian Electronic Library. University of Hawaiʻi Press. Archived from the original on 1 February 2021. Retrieved 21 November 2017.
  39. ^ Kesh, Johnathan (8 November 2017). "Our Solar System's First Interstellar Asteroid is Named ʻOumuamua'". Outer Places. Archived from the original on 1 December 2017. Retrieved 23 November 2017.
  40. ^ Wall, Mike (16 November 2017). "Meet ʻOumuamua, the First-Ever Asteroid from Another Star". Scientific American. Archived from the original on 22 November 2017. Retrieved 24 November 2017 – via Space.com.
  41. ^ Gal, Roy (20 November 2017). "An interstellar visitor unmasked". University of Hawaiʻi System News. Archived from the original on 24 November 2017. Retrieved 22 November 2017.
  42. ^ "The first visitor from another solar system has just been spotted: Rendezvous with Rama?". The Economist. 2 November 2017. Archived from the original on 6 December 2017. Retrieved 6 December 2017.
  43. ^ Morrison, David (March–April 2018). "Interstellar Visitor: The Strange Asteroid from a Faraway System". Skeptical Inquirer. 42 (2): 9.
  44. ^ a b "First Known Interstellar Visitor is an 'Oddball'". Gemini Observatory (Press release). 20 November 2017. Archived from the original on 23 November 2017. Retrieved 28 November 2017.
  45. ^ a b c d e Meech, K.J.; et al. (20 November 2017). "A brief visit from a red and extremely elongated interstellar asteroid". Nature. 552 (7685): 378–381. Bibcode:2017Natur.552..378M. doi:10.1038/nature25020. PMC 8979573. PMID 29160305. S2CID 4393243.
  46. ^ a b c d Rincon, Paul (20 November 2017). "Bizarre shape of interstellar asteroid". BBC News. Archived from the original on 8 April 2020. Retrieved 20 November 2017.
  47. ^ a b "Solar System's First Interstellar Visitor Dazzles Scientists". Jet Propulsion Laboratory. 20 November 2017. Archived from the original on 10 March 2020. Retrieved 20 December 2017.
  48. ^ a b "1I/ʻOumuamua = A/2017 U1 Orbit". Minor Planet Center. International Astronomical Union. Archived from the original on 4 January 2018. Retrieved 9 November 2017.
  49. ^ a b Koren, Marina (11 December 2017). "Astronomers to Check Mysterious Interstellar Object for Signs of Technology". The Atlantic. Archived from the original on 11 December 2017. Retrieved 11 December 2017.
  50. ^ a b Wenz, John (22 November 2017). "The first discovered interstellar asteroid is a quarter-mile long red beast". Astronomy. Archived from the original on 4 June 2019. Retrieved 6 December 2017.
  51. ^ a b Overbye, Dennis (22 November 2017). "An Interstellar Visitor Both Familiar and Alien". The New York Times. Archived from the original on 17 April 2020. Retrieved 23 November 2017.
  52. ^ Shostak, Seth (14 December 2017). "Is this mysterious space rock actually an alien spaceship?". NBC News. Archived from the original on 19 December 2017. Retrieved 20 December 2017.
  53. ^ a b c Billings, Lee (11 December 2017). "Alien Probe or Galactic Driftwood? SETI Tunes In to ʻOumuamua". Scientific American. Archived from the original on 14 December 2017. Retrieved 12 December 2017. So far limited observations of ʻOumuamua, using facilities such as the SETI Institute's Allen Telescope Array, have turned up nothing.
  54. ^ Beall, Abigail (12 December 2017). "It isn't an alien spacecraft, but we should still study ʻOumuamua". Wired UK. Archived from the original on 12 December 2017. Retrieved 12 December 2017.
  55. ^ Enriquez, J. E. (9 January 2018). "Breakthrough Listen Observations of 1I/ʻOumuamua with the GBT". Research Notes of the American Astronomical Society. 2 (1): 9. arXiv:1801.02814. Bibcode:2018RNAAS...2....9E. doi:10.3847/2515-5172/aaa6c9. S2CID 119435272.
  56. ^ a b c d e Beatty, Kelly (25 October 2017). "Astronomers Spot First-Known Interstellar Comet". Sky & Telescope. Archived from the original on 26 October 2017. Retrieved 25 October 2017.
  57. ^ Seidel, Jamie (26 October 2017). "'Alien' object excites astronomers. Is it a 'visitor' from nearby star?". The New Zealand Herald. Archived from the original on 24 September 2018. Retrieved 29 October 2017.
  58. ^ a b c Hein, A.M.; Perakis, N.; Long, K.F.; Crowl, A.; Eubanks, M.; Kennedy, R.G. III; Osborne, R. (2017). "Project Lyra: Sending a Spacecraft to 1I/ʻOumuamua (former A/2017 U1), the Interstellar Asteroid". arXiv:1711.03155 [physics.space-ph].
  59. ^ "MPEC 2017-U185: A/2017 U1". Minor Planet Center. International Astronomical Union. 26 October 2017. Archived from the original on 1 November 2017. Retrieved 26 October 2017.
  60. ^ "Inbound 2300 AU in 1606".
  61. ^ Inbound 1 AU (passing Earth's orbit)
  62. ^ "Outbound 100 AU in 2034".
  63. ^ Outbound 2300 AU in 2429
  64. ^ Clark, Stuart (20 November 2017). "Mysterious object confirmed to be from another solar system". The Guardian. Archived from the original on 25 April 2020. Retrieved 21 November 2017. Astronomers are now certain that the mysterious object detected hurtling past our Sun last month is indeed from another solar system. They have named it 1I/2017 U1 (ʻOumuamua) and estimate it could be one of 10,000 others lurking undetected in our cosmic neighbourhood.
  65. ^ a b "JPL Small-Body Database Search Engine – Constraints: e > 1". JPL Small-Body Database. Jet Propulsion Laboratory. Archived from the original on 9 December 2019. Retrieved 26 October 2017.
  66. ^ de la Fuente Marcos, C.; de la Fuente Marcos, R.úl (1 November 2017). "Pole, Pericenter, and Nodes of the Interstellar Minor Body A/2017 U1". Research Notes of the AAS. 1 (1): 5. arXiv:1711.00445. Bibcode:2017RNAAS...1....5D. doi:10.3847/2515-5172/aa96b4. S2CID 119537175.
  67. ^ Wright, Jason T.; Jones, Hugh R. A. (2018). "On Distinguishing Interstellar Objects Like ʻOumuamua From Products of Solar System Scattering". Research Notes of the AAS. 1 (1): 38. arXiv:1712.06044. Bibcode:2017RNAAS...1...38W. doi:10.3847/2515-5172/aa9f23. S2CID 119467366.
  68. ^ de la Fuente Marcos, Carlos; de la Fuente Marcos, Raúl; Aarseth, Sverre J. (2018). "Where the Solar system meets the solar neighbourhood: patterns in the distribution of radiants of observed hyperbolic minor bodies". Monthly Notices of the Royal Astronomical Society Letters. 476 (1): L1–L5. arXiv:1802.00778. Bibcode:2018MNRAS.476L...1D. doi:10.1093/mnrasl/sly019. S2CID 119405023.
  69. ^ "Sedna inbound 200 AU in 1746".
  70. ^ "Bowell (C/1980 E1) inbound 200 AU in 1765".
  71. ^ "ISON inbound 200 AU in 1801".
  72. ^ C/2008 J4 inbound 200 AU in 1854 (C/2008 J4 has an unreliable long-term orbit due a short arc of 15 days)
  73. ^ "Inbound 200 AU in 1982".
  74. ^ "2I/Borisov inbound 200 AU in 1991".
  75. ^ a b c d "Interstellar Asteroid FAQs". NASA. 20 November 2017. Archived from the original on 18 December 2019. Retrieved 21 November 2017.
  76. ^ Battams, Karl (9 October 2013). "Comet ISON is doing just fine!". NASA Comet ISON Observing Campaign. Archived from the original on 28 October 2017. Retrieved 12 December 2017.
  77. ^ a b Williams, Matt (2 November 2018). "Could Oumuamua Be an Extra-Terrestrial Solar Sail?". Universe Today. Archived from the original on 3 November 2018. Retrieved 2 November 2018.
  78. ^ a b Bialy, Shmuel; Loeb, Abraham (26 October 2018). "Could Solar Radiation Explain ʻOumuamua's Peculiar Acceleration?". The Astrophysical Journal. 868 (1): L1. arXiv:1810.11490. Bibcode:2018ApJ...868L...1B. doi:10.3847/2041-8213/aaeda8. S2CID 118956077.
  79. ^ a b Trilling, David; al., et (20 November 2018). "Spitzer Observations of Interstellar Object 1I/'Omumuamua". The Astronomical Journal. 156 (6): 261. arXiv:1811.08072. Bibcode:2018AJ....156..261T. doi:10.3847/1538-3881/aae88f. S2CID 119444117.
  80. ^ a b Cofield, Calla; Chou, Felicia; Wendel, JoAnna; Weaver, Donna; Villard, Ray (27 June 2018). "Our Solar System's First Known Interstellar Object Gets Unexpected Speed Boost". NASA. Archived from the original on 27 June 2018. Retrieved 27 June 2018.
  81. ^ Mamajek, Eric (2017). "Kinematics of the Interstellar Vagabond A/2017 U1". arXiv:1710.11364 [astro-ph.EP].
  82. ^ a b c Ye, Q.-Z.; Zhang, Q. (5 December 2017). "1I/ʻOumuamua is Hot: Imaging, Spectroscopy and Search of Meteor Activity" (PDF). The Astrophysical Journal Letters. 851 (1): L5. arXiv:1711.02320. Bibcode:2017ApJ...851L...5Y. doi:10.3847/2041-8213/aa9a34. S2CID 119392232. Archived (PDF) from the original on 23 July 2018. Retrieved 3 November 2018.
  83. ^ Moór, A.; Szabó, Gy. M.; Kiss, L. L.; Kiss, Cs.; Ábrahám, P.; Szulágyi, J.; Kóspál, Á.; Szalai, T. (2013). "Unveiling new members in five nearby young moving groups". Monthly Notices of the Royal Astronomical Society. 435 (2): 1376–1388. arXiv:1309.1669. Bibcode:2013MNRAS.435.1376M. doi:10.1093/mnras/stt1381. S2CID 54584506.
  84. ^ Gaidos, E.; Williams, J.P.; Kraus, A. (2017). "Origin of Interstellar Object A/2017 U1 in a Nearby Young Stellar Association?". Research Notes of the AAS. 1 (1): 13. arXiv:1711.01300. Bibcode:2017RNAAS...1...13G. doi:10.3847/2515-5172/aa9851. S2CID 119091790.
  85. ^ Hansen, Brad; Zuckerman, Ben (December 2017). "Ejection of Material—'Jurads'—from Post-main-sequence Planetary Systems". Research Notes of the American Astronomical Society. 1 (1). 55. arXiv:1712.07247. Bibcode:2017RNAAS...1...55H. doi:10.3847/2515-5172/aaa3ee. S2CID 118957210.
  86. ^ Portegies Zwart, S.; Pelupessy, I.; Bedorf, J.; Cai, M.; Torres, S. (9 November 2017). "The origin of interstellar asteroidal objects like 1I/2017 U1". Monthly Notices of the Royal Astronomical Society: Letters. 479 (1): L17–L22. arXiv:1711.03558. Bibcode:2018MNRAS.479L..17P. doi:10.1093/mnrasl/sly088. S2CID 56249057.
  87. ^ Bailer-Jones, Coryn A. L.; et al. (18 October 2018). "Plausible Home Stars of the Interstellar Object ʻOumuamua Found in Gaia DR2". The Astronomical Journal. 156 (5): 205. arXiv:1809.09009. Bibcode:2018AJ....156..205B. doi:10.3847/1538-3881/aae3eb. S2CID 119051284.
  88. ^ Bailer-Jones, C. A. L.; et al. "Plausible home stars of the interstellar object ʻOumuamua found in Gaia DR2". Coryn Bailer-Jones. Archived from the original on 23 October 2018. Retrieved 23 October 2018.
  89. ^ Feng, Fabo; Jones, Hugh R. A. (2018). "Plausible home stars of the interstellar object ʻOumuamua found in Gaia DR2". The Astronomical Journal. 156 (5): 205. arXiv:1809.09009. Bibcode:2018AJ....156..205B. doi:10.3847/1538-3881/aae3eb. S2CID 119051284.
  90. ^ Bartels, Meghan (25 September 2018). "ʻOumuamua Isn't from Our Solar System. Now We May Know Which Star It Came From". Space.com. Archived from the original on 25 September 2018. Retrieved 25 September 2018.
  91. ^ University of California, Santa Cruz (13 April 2020). "New formation theory explains the mysterious interstellar object 'Oumuamua – A new scenario based on computer simulations accounts for all of the observed characteristics of the first known interstellar object to visit our solar system". EurekAlert!. Archived from the original on 14 April 2020. Retrieved 13 April 2020.
  92. ^ Zhang, Yun; Lin, Douglas N. C. (13 April 2020). "Tidal fragmentation as the origin of 1I/2017 U1 (ʻOumuamua)". Nature Astronomy. 254 (9): 852–860. arXiv:2004.07218. Bibcode:2020NatAs...4..852Z. doi:10.1038/s41550-020-1065-8. S2CID 215768701. Archived from the original on 14 April 2020. Retrieved 13 April 2020.
  93. ^ Ćuk, Matija (2018). "1I/ʻOumuamua as a Tidal Disruption Fragment From a Binary Star System". The Astrophysical Journal. 852 (1): L15. arXiv:1712.01823. Bibcode:2018ApJ...852L..15C. doi:10.3847/2041-8213/aaa3db. S2CID 54959652.
  94. ^ Seligman, D.; Laughlin, G. (2020). "Evidence that 1I/2017 U1 ('Oumuamua) was composed of molecular hydrogen ice". The Astrophysical Journal. 896 (1): L8. arXiv:2005.12932. Bibcode:2020ApJ...896L...8S. doi:10.3847/2041-8213/ab963f. S2CID 218900854.
  95. ^ Hoang, T.; Loeb, Abraham (2020). "Destruction of molecular hydrogen ice and Implications for 1I/2017 U1 ('Oumuamua)". The Astrophysical Journal. 899 (2): L23. arXiv:2006.08088. Bibcode:2020ApJ...899L..23H. doi:10.3847/2041-8213/abab0c. S2CID 219687520.
  96. ^ Witze, Alexandra (27 June 2018). "Mysterious interstellar visitor is a comet – not an asteroid – Quirks in ʻOumuamua's path through the Solar System helped researchers solve a case of mistaken identity". Nature. doi:10.1038/d41586-018-05552-9. S2CID 126317359. Archived from the original on 27 June 2018. Retrieved 27 June 2018.
  97. ^ "ESO's VLT Sees ʻOumuamua Getting a Boost – New results indicate interstellar nomad ʻOumuamua is a comet". www.eso.org. 27 June 2018. Archived from the original on 3 July 2018. Retrieved 28 June 2018. Such outgassing is a behaviour typical for comets and contradicts the previous classification of ʻOumuamua as an interstellar asteroid. "We think this is a tiny, weird comet," commented Marco Micheli. "We can see in the data that its boost is getting smaller the farther away it travels from the Sun, which is typical for comets."
  98. ^ Fitzsimmons, Alan [@FitzsimmonsAlan] (27 October 2017). "Spectrum of A/2017 U1 obtained on Wednesday night with the @INGLaPalma 4.2m WHT. Colour is red like Kuiper Belt Objects, featureless" (Tweet) – via Twitter.
  99. ^ a b c d Fitzsimmons, A.; et al. (18 December 2017). "Spectroscopy and thermal modelling of the first interstellar object 1I/2017 U1 ʻOumuamua". Nature Astronomy. 2 (2): 133. arXiv:1712.06552. Bibcode:2018NatAs...2..133F. doi:10.1038/s41550-017-0361-4. S2CID 216937304. Archived from the original on 17 October 2019. Retrieved 25 September 2018. The discovery epoch photometry implies a highly elongated body with radii of ~200×20 m when a comet-like geometric albedo of 0.04 is assumed. Here we report spectroscopic characterisation of ʻOumuamua, finding it to be variable with time but similar to organically rich surfaces found in the outer Solar System. The observable ISO population is expected to be dominated by comet-like bodies in agreement with our spectra, yet the reported inactivity implies a lack of surface ice. We show this is consistent with predictions of an insulating mantle produced by long-term cosmic ray exposure. An internal icy composition cannot therefore be ruled out by the lack of activity, even though ʻOumuamua passed within 0.25 au of the Sun.
  100. ^ Drahus, M.; Guzik, P.; Waniak, W.; Handzlik, B.; Kurowski, S.; Xu, S. (1 December 2017). "Tumbling motion of 1I/ʻOumuamua reveals body's violent past". arXiv:1712.00437 [astro-ph.EP].
  101. ^ Meech, Karen; et al. (20 November 2017). "Light curve of interstellar asteroid ʻOumuamua". ESO. European Southern Observatory. Archived from the original on 19 December 2019. Retrieved 21 November 2017.
  102. ^ Amos, Jonathan (11 February 2018). "ʻOumuamua: 'space cigar's' tumble hints at violent past". BBC News. Archived from the original on 24 July 2018. Retrieved 21 July 2018.
  103. ^ Belton, M. J. S.; et al. (10 April 2018). "The Excited Spin State of 1I/2017 U1 'Oumuamua". The Astrophysical Journal. 856 (2): L21. arXiv:1804.03471. Bibcode:2018ApJ...856L..21B. doi:10.3847/2041-8213/aab370. S2CID 119336678. We find that ʻOumuamua is 'cigar-shaped', if close to its lowest rotational energy, and an extremely oblate spheroid if close to its highest energy state for its total angular momentum.
  104. ^ Thomas, C. A.; Trilling, D. E.; Emery, J. P.; Mueller, M.; Hora, J. L.; Benner, L. A. M.; Bhattacharya, B.; Bottke, W. F.; Chesley, S. (1 September 2011). "ExploreNEOs. V. Average Albedo by Taxonomic Complex in the Near-Earth Asteroid Population". The Astronomical Journal. 142 (3): 85. Bibcode:2011AJ....142...85T. doi:10.1088/0004-6256/142/3/85. ISSN 0004-6256.
  105. ^ a b Ian Sample (11 December 2017). "Astronomers to check interstellar body for signs of alien technology". The Guardian. Archived from the original on 25 April 2020. Retrieved 12 December 2017. Green Bank telescope in West Virginia will listen for radio signals from ʻOumuamua, an object from another solar system ... "Most likely it is of natural origin, but because it is so peculiar, we would like to check if it has any sign of artificial origin, such as radio emissions," said Avi Loeb, professor of astronomy at Harvard University and an adviser to the Breakthrough Listen project. "If we do detect a signal that appears artificial in origin, we'll know immediately." ... While many astronomers believe the object is an interstellar asteroid, its elongated shape is unlike anything seen in the asteroid belt in our own solar system. Early observations of ʻOumuamua show that it is about 400m long but only one tenth as wide. "It's curious that the first object we see from outside the solar system looks like that," said Loeb.
  106. ^ Mashchenko, Sergey (November 2019). "Modeling the light curve of 'Oumuamua: evidence for torque and disc-like shape". Monthly Notices of the Royal Astronomical Society. 489 (3): 3003–3021. arXiv:1906.03696. Bibcode:2019MNRAS.489.3003M. doi:10.1093/mnras/stz2380. S2CID 182952355.
  107. ^ de la Fuente Marcos, C.; de la Fuente Marcos, R. (1 November 2020). "Constraining the orientation of the spin axes of extrasolar minor bodies 1I/2017 U1 ('Oumuamua) and 2I/Borisov". Astronomy and Astrophysics. 643: A18 (17 pp). arXiv:2009.08423. Bibcode:2020A&A...643A..18D. doi:10.1051/0004-6361/202037447. S2CID 221761422. Archived from the original on 1 February 2021. Retrieved 27 October 2020.
  108. ^ Voosen, Paul (20 November 2017). "Updated: For the first time, astronomers are tracking a distant visitor streaking through our solar system". Science. doi:10.1126/science.aar3433. Archived from the original on 21 November 2017. Retrieved 30 November 2017.
  109. ^ O'Neill, Ian (20 November 2017). "Wow! 1st Interstellar Asteroid Is a Spinning Space Cigar". Space.com. Archived from the original on 25 April 2020. Retrieved 30 November 2017.
  110. ^ a b Williams, Matt (20 November 2017). "That Interstellar Asteroid is probably pretty strange looking". Universe Today. Archived from the original on 22 December 2017. Retrieved 20 December 2017. Its dark and reddened surface is also an indication of tholins, which are the result of organic molecules (like methane) being irradiated by cosmic rays for millions of years.
  111. ^ Williams, Matt (24 November 2017). "Project Lyra, a mission to chase down that interstellar asteroid". Universe Today. Archived from the original on 30 December 2017. Retrieved 20 December 2017. It was also determined to be rocky and metal rich, and to contain traces of tholins – organic molecules that have been irradiated by UV radiation. Also here [1] Archived 22 December 2017 at the Wayback Machine at Phys.org
  112. ^ Anderson, Paul Scott (26 November 2019). "Was 'Oumuamua a cosmic dust bunny?". Earth & Sky. Archived from the original on 27 November 2019. Retrieved 27 November 2019.
  113. ^ Flekkøy, Eirik G.; et al. (11 November 2019). "The Interstellar Object 'Oumuamua as a Fractal Dust Aggregate" (PDF). The Astrophysical Journal Letters. 885 (2): L41. arXiv:1910.07135. Bibcode:2019ApJ...885L..41F. doi:10.3847/2041-8213/ab4f78. S2CID 204734116. Archived (PDF) from the original on 1 February 2021. Retrieved 30 November 2019.
  114. ^ Tomaswick, Andy (8 September 2020). "Okay, New Idea. Oumuamua is an Interstellar 'Dust Bunny'". Universe Today. Archived from the original on 11 September 2020. Retrieved 9 September 2020.
  115. ^ Harvard-Smithsonian Center for Astrophysics and Korea Astronomy and Space Science Institute (17 August 2020). "Scientists determine 'Oumuamua isn't made from molecular hydrogen ice after all". Phys.org. Archived from the original on 17 August 2020. Retrieved 17 August 2020.
  116. ^ Hoang, Thiem; Loeb, Abraham (17 August 2020). "Destruction of Molecular Hydrogen Ice and Implications for 1I/2017 U1 ('Oumuamua)". The Astrophysical Journal Letters. 899 (2): L23. arXiv:2006.08088. Bibcode:2020ApJ...899L..23H. doi:10.3847/2041-8213/abab0c.
  117. ^ "Breakthrough Listen Releases Initial Results and Data from Observations of ʻOumuamua". Breakthrough Listen. 13 December 2017. Archived from the original on 15 December 2017. Retrieved 15 December 2017. No evidence of artificial signals emanating from the object so far detected by the Green Bank Telescope, but monitoring and analysis continue. Initial data are available for public inspection in the Breakthrough Listen archive
  118. ^ Ian Sample (15 December 2017). "Is ʻOumuamua an alien spacecraft? Initial scans show no signs of technology". The Guardian. Archived from the original on 15 December 2017. Retrieved 15 December 2017.
  119. ^ Siegel, Ethan (10 February 2021). "New Theory Perfectly Explains 'Oumuamua Naturally: It's A Nitrogen Iceberg". Forbes. Archived from the original on 13 February 2021. Retrieved 13 February 2021.
  120. ^ Staff (17 March 2021). "Scientists determine the origin of extra-solar object 'Oumuamua". Phys.org. Retrieved 17 March 2021.
  121. ^ "Was the Interstellar Object 'Oumuamua a Nitrogen Iceberg?". Scientific American.
  122. ^ a b Siraj, Amir; Loeb, Abraham (April 2022). "The mass budget necessary to explain 'Oumuamua as a nitrogen iceberg". New Astronomy. 92. 101730. arXiv:2103.14032. Bibcode:2022NewA...9201730S. doi:10.1016/j.newast.2021.101730. S2CID 232352541.
  123. ^ Hickok, Kimberly (15 November 2021). "Interstellar visitor 'Oumuamua wasn't a nitrogen iceberg, Harvard astrophysicists say - The bizarre interloper called 'Oumuamua continues to defy explanation". Live Science. Retrieved 15 November 2021.
  124. ^ Seligman, Darryl; Laughlin, Gregory (26 May 2020). "Evidence that 1I/2017 U1 ('Oumuamua) was Composed of Molecular Hydrogen Ice". The Astrophysical Journal. 896 (1): L8. arXiv:2005.12932. Bibcode:2020ApJ...896L...8S. doi:10.3847/2041-8213/ab963f. S2CID 218900854.
  125. ^ Overbye, Dennis (15 June 2020). "Oumuamua: Neither Comet nor Asteroid, but a Cosmic Iceberg – A new study suggests the interloper may have arisen in an interstellar cloud, where stars are sometimes born". The New York Times. Archived from the original on 16 June 2020. Retrieved 16 June 2020.
  126. ^ Perets, Hagai B.; Biham, Ofer; Manico, Giulio; Pirronello, Valerio; Roser, Joe; Swords, Sol; Vidali, Gianfranco (29 March 2005). "Molecular Hydrogen Formation on Ice Under Interstellar Conditions". The Astrophysical Journal. 627 (2): 850–860. arXiv:astro-ph/0412202. Bibcode:2005ApJ...627..850P. doi:10.1086/430435. S2CID 56368174. Archived from the original on 6 June 2020.
  127. ^ "About Comets". lpi.usra.edu. Archived from the original on 16 November 2020. Retrieved 6 June 2020.
  128. ^ Hoang, Thiem; Loeb, Abraham (2020). "Destruction of molecular hydrogen ice and Implications for 'Oumuamua". The Astrophysical Journal Letters. 899 (2). arXiv:2006.08088. Bibcode:2020ApJ...899L..23H. doi:10.3847/2041-8213/abab0c. S2CID 219687520.
  129. ^ a b Letzer, Ran (19 August 2020). "Interstellar visitor 'Oumuamua could still be alien technology, new study hints – Aliens? Or a chunk of solid hydrogen? Which idea makes less sense?". Live Science. Archived from the original on 9 January 2021. Retrieved 6 January 2021.
  130. ^ Bergner, Jennifer B.; Seligman, Darryl Z. (2023), "Acceleration of 1I/'Oumuamua from radiolytically produced H2 in H2O ice", Nature, 615 (7953): 610–613, arXiv:2303.13698, doi:10.1038/s41586-022-05687-w, PMID 36949336, S2CID 257668585
  131. ^ a b "Project Lyra – A Mission to ʻOumuamua". I4IS. Initiative for Interstellar Studies. Archived from the original on 3 December 2017. Retrieved 3 December 2017.
  132. ^ Hein, Andreas M.; Perakis, Nikolaos; Eubanks, T. Marshall; Hibberd, Adam; Crowl, Adam; Hayward, Kieran; Kennedy III, Robert G.; Osborne, Richard (7 January 2019). "Project Lyra: Sending a spacecraft to 1I/'Oumuamua (former A/2017 U1), the interstellar asteroid". Acta Astronautica. 161: 552. arXiv:1711.03155. Bibcode:2019AcAau.161..552H. doi:10.1016/j.actaastro.2018.12.042. S2CID 119474144.
  133. ^ Hibberd, Adam; Hein, Andreas M.; Eubanks, T. Marshall (2020). "Project Lyra: Catching 1I/'Oumuamua – Mission Opportunities After 2024". Acta Astronautica. 170: 136–144. arXiv:1902.04935. Bibcode:2020AcAau.170..136H. doi:10.1016/j.actaastro.2020.01.018. S2CID 119078436.
  134. ^ Klaus, K. (2015). The Space Launch System and Missions to the Outer Solar System (PDF). 46th Lunar and Planetary Science Conference. 16–20 March 2015. The Woodlands, Texas. Archived (PDF) from the original on 26 October 2020. Retrieved 5 June 2019.
  135. ^ McNutt, R. L. Jr.; et al. (2014). Enabling interstellar probe with the Space Launch System (SLS). 65th International Astronautical Congress. 29 September-3 October 2014. Toronto, Canada. Archived from the original on 1 February 2021. Retrieved 5 June 2019.
  136. ^ "Space Launch System: Mission Booklet". Studylib.net. Boeing. 2013. Archived from the original on 5 June 2019. Retrieved 5 June 2019.
  137. ^ Arora, Nitin; et al. (2014). "An Architectural Framework for the design of missions to explore the ISM" (PDF). NASA/Jet Propulsion Laboratory. Archived (PDF) from the original on 1 September 2020. Retrieved 25 October 2019.
  138. ^ Seligman, Darryl; Laughlin, Gregory (12 April 2018). "The Feasibility and Benefits of in situ Exploration of ʻOumuamua-like Objects". The Astronomical Journal. 155 (5): 217. arXiv:1803.07022. Bibcode:2018AJ....155..217S. doi:10.3847/1538-3881/aabd37. S2CID 73656586.
  139. ^ Carmeli, Oded (14 January 2019). "If True, This Could Be One of the Greatest Discoveries in Human History". Haaretz. Archived from the original on 14 January 2019. Retrieved 14 January 2019.
  140. ^ Selik, Avi (4 February 2019). "Alien ship may be among us, Harvard astronomer insists, despite grumbling and criticism from peers". ChicagoTribune. Archived from the original on 5 February 2019. Retrieved 5 February 2019.
  141. ^ Loeb, Abraham (26 September 2018). "How to Search for Dead Cosmic Civilizations". Scientific American. Archived from the original on 27 April 2020. Retrieved 26 September 2018.
  142. ^ Sheridan, Kerry (7 November 2018). "Scientists push back against Harvard 'alien spacecraft' theory". Phys.org. Archived from the original on 23 January 2021. Retrieved 14 February 2021.
  143. ^ Boyle, Alan (6 November 2018). "'Oumuamua, oh my! Was interstellar object actually an alien solar sail? Not so fast". Yahoo!. Archived from the original on 8 November 2018. Retrieved 8 November 2018.
  144. ^ Schadwinkel, Alina (8 November 2018). "Glaubt dieser Harvard-Professor selbst, was er sagt?". Zeit Online (in German). Archived from the original on 8 November 2018. Retrieved 8 November 2018.
  145. ^ "Cigar-shaped interstellar object may have been an alien probe, Harvard paper claims". WPSD Local 6. CNN. 6 November 2018. Archived from the original on 25 October 2019. Retrieved 25 October 2019.
  146. ^ Loeb, Abraham (20 November 2018). "6 Strange Facts about the Interstellar Visitor 'Oumuamua". Scientific American. Archived from the original on 20 November 2018. Retrieved 20 November 2018.
  147. ^ Chotiner, Isaac (16 January 2019). "Have Aliens Found Us? A Harvard Astronomer on the Mysterious Interstellar Object 'Oumuamua". The New Yorker. Archived from the original on 16 January 2019. Retrieved 16 January 2019.
  148. ^ Wright, Jason T.; Desch, Steven; Raymond, Sean (18 July 2023). "'Oumuamua: Natural or Artificial?". Medium. Archived from the original on 21 July 2023. Retrieved 27 July 2023.
  149. ^ Katz, J. I. (15 February 2021). "'Oumuamua is not Artificial". arXiv:2102.07871 [physics.pop-ph].
  150. ^ Pultarova, Tereza (3 November 2022). "Confirmed! A 2014 meteor is Earth's 1st known interstellar visitor - Interstellar space rocks might be falling to Earth every 10 years". Space.com. Retrieved 4 November 2022.
  151. ^ Ferreira, Becky (7 April 2022). "Secret Government Info Confirms First Known Interstellar Object on Earth, Scientists Say - A small meteor that hit Earth in 2014 was from another star system, and may have left interstellar debris on the seafloor". Vice News. Retrieved 9 April 2022.
  152. ^ Wenz, John (11 April 2022). ""It Opens A New Frontier Where You're Using The Earth As A Fishing Net For These Objects." - Harvard Astronomer Believes An Interstellar Meteor (or Craft) Hit Earth In 2014". Inverse. Retrieved 11 April 2022.
  153. ^ Siraj, Amir; Loeb, Abraham (4 June 2019). "Discovery of a Meteor of Interstellar Origin". arXiv:1904.07224 [astro-ph.EP].
  154. ^ Handal, Josh; Fox, Karen; Talbert, Tricia (8 April 2022). "U.S. Space Force Releases Decades of Bolide Data to NASA for Planetary Defense Studies". NASA. Retrieved 11 April 2022.
  155. ^ Loeb, Avi (23 September 2022). "The discovery of a second interstellar meteor". TheDebrief.org. Retrieved 24 September 2022.
  156. ^ Richtel, Matt (11 March 2024). "Surprise: An 'Extraterrestrial' Gadget Was Something More Familiar - In 2014 a fireball from outer space was posited to be an alien artifact. A recent study suggests otherwise". The New York Times. Archived from the original on 11 March 2024. Retrieved 11 March 2024.
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