ʻOumuamua (/ʔoʊˌmuːəˈmuːə/, Hawaiian: [ʔowˌmuwəˈmuwə] (listen)) is the first and currently only interstellar object detected passing through the Solar System. Formally designated 1I/2017 U1, it was discovered by Robert Weryk using the Pan-STARRS telescope at Haleakala Observatory, Hawaii, on 19 October 2017, 40 days after it passed its closest point to the Sun. When it was first observed, it was about 33,000,000 km (21,000,000 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 about 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) in size. It has a dark red color, similar to objects in the outer Solar System. ʻOumuamua showed no signs of a comet coma (atmosphere) despite its close approach to the Sun, but underwent non-gravitational acceleration. This effect is seen in many icy comets, although other reasons have been suggested. Nonetheless, the object could be a remnant of a disintegrated interstellar comet (or exocomet), according to a NASA scientist. The object has a rotation rate similar to the average spin rate seen in Solar System asteroids, but is more elongated than all but a few other natural bodies. While a strengthless object (rubble pile) would require it to be of a density similar to rocky asteroids, a small amount of internal strength similar to icy comets would allow a relatively low density. ʻOumuamua is tumbling, rather than smoothly rotating, and is moving so fast relative to the Sun that there is no chance it originated in the Solar System. It also means that ʻOumuamua cannot be captured into a solar orbit, so it will eventually leave the Solar System and resume traveling through interstellar space. It will take the object roughly 20,000 years to travel the Solar System before exiting.[Note 3] ʻOumuamua's system of origin and the amount of time it has spent traveling amongst the stars are unknown.
ʻOumuamua on 28 October 2018[a]
|Discovered by||Robert Weryk using Pan-STARRS 1|
|Discovery site||Haleakala Obs., Hawaii|
|Discovery date||19 October 2017|
|MPC designation||1I/2017 U1|
|Hawaiian term for scout|
|Orbital characteristics |
|Epoch 2 November 2017 (JD 2458059.5)|
|Observation arc||34 days|
|−1.2798±0.0008 AU[Note 1]|
Average orbital speed
|26.33±0.01 km/s (interstellar)|
|0° 40m 48.72s / day|
|Earth MOID||0.0959 AU · 37.3 LD|
|Jupiter MOID||1.455 AU|
|Dimensions||100–1000 m long|
230 m × 35 m × 35 m
(est. at albedo 0.10)
|Tumbling (non-principal axis rotation)|
Reported values include: 8.10±0.02 h
|0.1 (spectral est.)|
0.06–0.08 (spectral est.)
B–V = 0.7±0.06
V-R = 0.45±0.05
g-r = 0.47±0.04
r-i = 0.36±0.16
r-J = 1.20±0.11
|19.7 to >27.5[Note 2]|
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. ʻOumuamua, as the first object so identified, was designated 1I, with rules on 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 referred to as 1I; 1I/2017 U1; 1I/ʻOumuamua; or 1I/2017 U1 (ʻOumuamua).
The name comes from Hawaiian ʻoumuamua, meaning 'scout' (from ʻou, meaning 'reach out for', and mua, reduplicated for emphasis, meaning 'first, in advance of'), and reflects the way this object is like a scout or messenger sent from the distant past to reach out to humanity. It roughly translates to "first distant messenger". The first character is a Hawaiian ʻokina, not an apostrophe, and is pronounced as a glottal stop; the name was chosen by the Pan-STARRS team in consultation with Kaʻiu Kimura and Larry Kimura of the University of Hawaii at Hilo.
Before the official name was decided upon, the name 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.
Observations and conclusions concerning the trajectory of ʻOumuamua were primarily obtained with data from the Pan-STARRS1 Telescope, part of the Spaceguard Survey, and the Canada-France-Hawaii Telescope (CFHT), and its composition and shape from the Very Large Telescope and the Gemini South telescope in Chile, as well as 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. Post announcement, the space-based telescopes Hubble and Spitzer joined in the observations.
ʻOumuamua is small and dark. It was not seen in STEREO HI-1A observations near its perihelion on 9 September 2017, limiting its brightness to ~13.5 mag. By the end of October, ʻOumuamua had already faded to apparent magnitude ~23, and in mid-December 2017, it was too faint and fast moving to be studied by even the largest ground-based telescopes.
ʻOumuamua was compared to the fictional alien spacecraft Rama because of its interstellar origin. Adding to the coincidence, both the real and the fictional objects are unusually elongated. ʻOumuamua has a reddish hue and unsteady brightness, which are typical of asteroids.
The SETI Institute's radio telescope, the Allen Telescope Array, examined ʻOumuamua, but detected no unusual radio emissions. More detailed observations, using the Breakthrough Listen hardware and the Green Bank Telescope, were performed; 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 power of 0.08 watts.
ʻOumuamua appears to have come from roughly the direction of Vega in the constellation Lyra. The incoming direction of motion of ʻOumuamua is 6° from the solar apex (the direction of the Sun's movement relative to local stars), which is the most likely direction for approaches from objects outside the Solar System. On 26 October, two precovery observations from the Catalina Sky Survey were found dated 14 and 17 October. A two-week observation arc had verified a strongly hyperbolic trajectory. It has a hyperbolic excess velocity (velocity at infinity, ) of 26.33 km/s (94,800 km/h), its speed relative to the Sun when in interstellar space.[Note 4]
|1 AU||9 August 2017||49.67|
|Perihelion||9 September 2017||87.71|
|1 AU||10 October 2017||49.67[Note 5]|
By mid-November, astronomers were certain that it was an interstellar object. Based on observations spanning 34 days, ʻOumuamua's orbital eccentricity is 1.20, the highest ever observed. 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,[Note 6] 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, if any should exist, could not account for ʻOumuamua's trajectory nor boost its speed to the observed value. For these reasons, ʻOumuamua can only be of interstellar origin.
|# of observations|
and obs arc[Note 7]
|90377 Sedna||1.99||196 in 9240 days|
|C/1980 E1 (Bowell)||2.96||179 in 2514 days|
|C/1997 P2 (Spacewatch)||2.96||94 in 49 days|
|C/2010 X1 (Elenin)||2.96||2222 in 235 days|
|C/2012 S1 (ISON)||2.99||6514 in 784 days|
|C/2008 J4 (McNaught)||4.88||22 in 15 days[Note 8]|
|1I/2017 U1 (ʻOumuamua)||26.5||121 in 34 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) as it passed south of the ecliptic on 6 September and made a sharp turn upward at its closest approach to the Sun (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.[Note 9] The object is now heading away from the Sun towards Pegasus towards a vanishing point 66° from the direction of its approach.[Note 10] This implies that a hypothetical observer near the Sun facing towards ʻOumuamua will eventually rotate through 294 degrees, while the direction of motion of ʻOumuamua (relative to the Sun) will eventually have turned by 114 degrees.
On the outward leg of its journey through the Solar System, ʻOumuamua passed within the orbit of Earth on 14 October at a distance of approximately 0.1616 AU (24,180,000 km; 15,020,000 mi) from Earth, and went back north of the ecliptic on 16 October and passed beyond the orbit of Mars on 1 November. It passed beyond Jupiter's orbit in May 2018, and will pass beyond Saturn's orbit in January 2019 and Neptune's orbit in 2022. As it leaves the Solar System it will be approximately right ascension 23h51m and declination +24°45', in Pegasus. It will continue to slow down until it reaches a speed of 26.33 km/s relative to the Sun, the same speed it had before its approach to the Solar System. It will take the object roughly 20,000 years to leave the Solar System completely.[Note 11]
On 27 June 2018, astronomers reported a non-gravitational acceleration to ʻOumuamua's trajectory, potentially consistent with a push from solar radiation pressure. Initial speculation as to the cause of this acceleration pointed to comet off-gassing, whereby portions of the object are ejected as the Sun heats the surface. Although no such tail of gases was ever observed following the object, researchers estimated that enough outgassing may have increased the object's speed without the gasses being detectable. A critical re-assessment of the comet hypothesis found that, instead of the observed stability of 'Oumuamua's spin, outgassing would have caused its spin to rapidly change due to its elongated shape, resulting in the object tearing apart.
Accounting for Vega's proper motion, it would have taken ʻOumuamua 600,000 years to reach the Solar System from Vega. But as a nearby star, Vega was not in the same part of the sky at that time. Astronomers calculate that one hundred years ago the object was 561 ± 0.6 AU (83.9 ± 0.090 billion km; 52.1 ± 0.056 billion mi) from the Sun and traveling at 26.33 km/s with respect to the Sun. 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. In fact, the strong correlation between ʻOumuamua's velocity and 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.
It is unknown how long the object has been traveling among the stars. The Solar System is likely the first star system that ʻOumuamua has closely encountered since being ejected from its birth star system, potentially several billion years ago. 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, some 45 million years ago. 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. 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 (54,000 km/h).[Note 12] A more recent study (August 2018) using Gaia Data Release 2 has updated the possible past close encounters and has identified four stars that ʻOumuamua passed relatively close to and at moderately low velocities in the past few million years. This study also identifies future close encounters of ʻOumuamua on its outgoing trajectory from the Sun.
According to one hypothesis, ʻOumuamua could be a fragment from a tidally disrupted planet.[Note 13] If true, this would make ʻOumuamua a rare object, of a type much less abundant than most extrasolar "dusty-snowball" comets or asteroids.
Initially, ʻOumuamua was announced as comet C/2017 U1 (PANSTARRS) based on a strongly hyperbolic trajectory. 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.[Note 14] Accordingly, the object was renamed A/2017 U1, becoming the first comet ever to be re-designated as an asteroid. Once it was identified as an interstellar object, it was designated 1I/2017 U1, the first member of a new class of objects. 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. 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. It is difficult to say which scenario is more likely due to the chaotic nature of small body dynamics, 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.
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. However, studies submitted in October 2018 suggest that the object is neither an asteroid nor a comet, although the object could be a remnant of a disintegrated interstellar comet (or exocomet), as suggested by a NASA scientist.
Spectra recorded by the 4.2 m (14 ft) William Herschel Telescope on 25 October showed that the object was featureless, and colored red like Kuiper belt objects. Spectra from the Hale Telescope showed a less-red color resembling comet nuclei or Trojans. Its spectrum is similar to that of D-type asteroids.
ʻOumuamua is rotating around a non-principal axis, a type of movement known as tumbling. This accounts for the various rotation periods reported, such as 8.10 hours, (±0.42 hours) (±0.02 hours) with a lightcurve amplitude of 1.5–2.1 magnitudes, whereas Meech et al. reported a rotation period of 7.3 hours and a lightcurve amplitude of 2.5 magnitudes.[Note 15] 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.
The large variations on the light curves indicate that ʻOumuamua may be either a highly elongated object, comparable to or greater than the most elongated Solar System objects, or an extremely flat object, a pancake or oblate sphereoid. 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 the albedo nor triaxial ellipsoid shape are precisely known. If cigar-shaped, the longest-to-shortest axis ratio could be 5:1 or greater. Assuming an albedo of 10% (slightly higher than typical for D-type asteroids) 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) with an average diameter of about 110 m (360 ft). According to astronomer David Jewitt, the object is physically unremarkable except for its highly elongated shape. Bannister et al. have suggested that it could also be a contact binary, although this may not be compatible with its rapid rotation. 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. JPL News reported that ʻOumuamua "is up to one-quarter mile, 400 m (1,300 ft), long and highly-elongated-perhaps 10 times as long as it is wide".
Light curve observations suggest the object may be composed of dense metal-rich rock that has been reddened by millions of years of exposure to cosmic rays. 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. This possibility is inferred from spectroscopic characterization and its dark and reddened color, and from the expected effects of interstellar radiation. 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".
In December 2017, astronomer Avi Loeb of Harvard University, an adviser to the Breakthrough Listen Project, cited ʻOumuamua's unusually elongated shape as one of the reasons why 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, although earlier limited observations by other radio telescopes such as the SETI Institute's Allen Telescope Array had produced no such results. 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 observations are ongoing.
On 26 October 2018, Loeb and his postdoc Shmuel Bialy submitted a paper exploring the possibility of ʻOumuamua being an artificial thin solar sail accelerated by solar radiation pressure in an effort to help explain the object's non-gravitational acceleration. Other scientists have stated that the available evidence is insufficient to consider such a premise, and that a tumbling solar sail would not be able to accelerate. In response, Loeb wrote an article detailing six anomalous properties of ʻOumuamua that make it unusual, unlike any comets or asteroids seen before. 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 more shiny than a typical comet. A detailed podcast produced by Rob Reid provides the full details about the differences between ʻOumuamua and known comets.
ʻOumuamua was at first thought to be traveling too fast for any existing spacecraft to reach. The Initiative for Interstellar Studies (i4is) launched Project Lyra to assess the feasibility of a mission to ʻOumuamua. Several options for sending a spacecraft to ʻOumuamua within a time-frame of 5 to 25 years were suggested. One option is using first a Jupiter flyby followed by a close solar flyby at 3 solar radii (2.1×106 km; 1.3×106 mi) in order to take advantage of the Oberth effect. Different mission durations and their velocity requirements were explored with respect to the launch date, assuming direct impulsive transfer to the intercept trajectory. Using a powered Jupiter flyby, a solar Oberth maneuver and Parker Solar Probe heat shield technology, a Falcon Heavy-class launcher would be able to launch a spacecraft of dozens of kilograms towards 1I/ʻOumuamua, if launched in 2021. 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 asteroid 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". 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. 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.
Astronomers estimate that several interstellar objects of extrasolar origin (like ‘Oumuamua) pass inside the orbit of Earth each year, and that 10,000 are passing inside the orbit of Neptune on any given day. If the estimate is correct, this provides future opportunities for studies of interstellar objects. However, with current space technology, close visits and orbital missions are challenging due to their high speeds, though not impossible.
On 27 November 2018, Loeb and his undergraduate student at Harvard College, Amir Siraj, proposed a search for ‘Oumuamua-like objects which are trapped in the Solar System as a result of losing orbital energy through a close encounter with Jupiter. They identified 4 candidates for trapped interstellar objects that could be visited by dedicated missions (2011 SP25, 2017 RR2, 2017 SV13, and 2018 TL6). The authors pointed out that future sky surveys, such as with LSST, should find many more.
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.
As its albedo is unknown, we do not describe 1I/‘Oumuamua as consistent with Tholen (1984) P type.
So far limited observations of ‘Oumuamua, using facilities such as the SETI Institute’s Allen Telescope Array, have turned up nothing.
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.
Such outgassing is a behaviour typical for comets and contradicts the previous classification of `Oumuamua 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.”
We find that ‘Oumuamua 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.
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.
It’s 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.
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  at Phys.org
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.
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
Chemical propulsion just doesn’t close the case in this scenario.
1865 Cerberus, provisional designation 1971 UA, is a stony asteroid and near-Earth object of the Apollo group, approximately 1.6 kilometers in diameter. It was discovered on 26 October 1971, by Czech astronomer Luboš Kohoutek at the Hamburger Bergedorf Observatory, Germany, and named for Cerberus from Greek mythology.1I
1I may refer to:
1i Productions, an American board game publisher
SSH 1I (WA), part of which became Washington State Route 525
1I/2017 U1 (ʻOumuamua), abbreviated 1I, the first observed interstellar object passing through the Solar System.276P/Vorobjov
276P/Vorobjov (previously P/2012 T7 (VOROBJOV)) is a Jupiter-family comet discovered on 15 October 2012 by Tomáš Vorobjov on three 120-s images taken remotely using the 0.81-m f/7 Ritchey-Chretien Schulman Telescope located at the Mt. Lemmon SkyCenter via the Sierra Stars Observatory Network in the course of a minor-planet search survey undertaken as part of the International Astronomical Search Collaboration (IASC) school campaigns. After posting on the Minor Planet Center's NEOCP webpage, other observers have commented on the object's cometary appearance. The discovery was announced by the Minor Planet Center on 18 October, three days after the discovery.Avi Loeb
Abraham "Avi" Loeb (Hebrew: אברהם (אבי) לייב) is an Israeli American theoretical physicist who works on astrophysics and cosmology. Loeb is the Frank B. Baird Jr. Professor of Science at Harvard University. He serves as Chair of the Harvard Astronomy department (since 2011), Chair of the Advisory Committee for the Breakthrough Starshot project – which aims to launch lightweight spacecraft towards the nearest stars using a powerful laser (since 2016), founding director of Harvard's Black Hole Initiative – the first interdisciplinary center worldwide dedicated to the study of black holes (since 2016), and director of the Institute for Theory and Computation (ITC) (since 2007) within the Harvard-Smithsonian Center for Astrophysics.
Loeb is an elected fellow of the American Academy of Arts and Sciences, the American Physical Society, and the International Academy of Astronautics. As of July 2018, he was appointed as chair of the Board on Physics and Astronomy (BPA) of the National Academies, which is the Academies' principal forum for issues connected with the fields of Physics and Astronomy including oversight of their decadal surveys. In December 2012, TIME magazine selected Loeb as one of the 25 most influential people in space. In 2015, Loeb was appointed as the Science Theory Director for the Breakthrough Initiatives of the Breakthrough Prize Foundation. In 2018, he attracted publicity for suggesting that alien space craft may be in our solar system, using the anomalous behavior of 'Oumuamua as an example.C/1980 E1 (Bowell)
C/1980 E1 is a non-periodic comet discovered by Edward L. G. Bowell on 11 February 1980. C/1980 E1 is leaving the Solar System on a hyperbolic trajectory with only 1I/ʻOumuamua being on a faster hyperbolic trajectory.Before entering the inner Solar System for a 1982 perihelion passage, C/1980 E1 had a barycentric (epoch 1950-Jan-01) orbit with an aphelion of 74,300 AU (1.17 light-years), and a period of approximately 7.1 million years.As the comet was approaching perihelion on December 9, 1980, it passed within 0.228 AU of Jupiter, which accelerated the comet briefly giving an (epoch 1981-Jan-09) eccentricity of 1.066. The comet came to perihelion on March 12, 1982, when it had a velocity of 23.3 km/s (52,000 mph) with respect to the Sun. Since the epoch of 1977-Mar-04, C/1980 E1 has had a barycentric eccentricity greater than 1, keeping it on a hyperbolic trajectory that will eject it from the Solar System. Objects in hyperbolic orbits have a negative semimajor axis, giving them a positive orbital energy. The Minor Planet Center does not directly list a semimajor axis for this comet.
By May 1995, the comet was 30 AU from the Sun on an ejection trajectory going 8.6 km/s (19,000 mph). Since February 2008, the comet has been more than 50 AU from the Sun.The production of OH (hydroxide) was observed pre-perihelion while the comet was nearly 5 AU from the Sun. CN (cyanide) was not detected until the comet was near perihelion. The comet nucleus was estimated to have a radius of several kilometers. The surface crust was probably a few meters thick.C/2012 E2 (SWAN)
Comet C/2012 E2 (SWAN) was a Kreutz group sungrazing comet discovered by Vladimir Bezugly in publicly available images taken by the SWAN instrument (Solar Wind ANisotropies) on board the SOHO spacecraft. It is recognized for being the first Kreutz sungrazer observed in SWAN imagery.C/2015 F3
Comet C/2015 F3 (SWAN) was discovered in March 2015 by Rob Matson, Vladimir Bezugly and Michael Matiazzo in near real time images taken by the SWAN instrument aboard the SOHO spacecraft. At discovery the comet was already shining at around 10th magnitude as it was already near perihelion
. Orbital studies revealed C/2015 F3 to be a related fragment to long periodic comets C/1988 A1 (Liller) and C/1996 Q1 (Tabur), which were already thought to have broken off each other at a previous perihelion passage. As of May 2015, Comet SWAN was fading rapidly, as both C/1988 A1 and C/1996 Q1 ultimately did. .C/2015 F5 (SWAN-XingMing)
Comet C/2015 F5 (SWAN-XingMing) was discovered on March 29, 2015 in near real time SWAN images of the SOHO spacecraft, by Szymon Liwo and Worachate Boonplod. It was also independently discovered on April 4, 2015 by Guoyou Sun and Gao Xing at the XingMing observatory near Ürümqi, China. At discovery, the comet had just passed perihelion and was only 0,35 AU from the Sun, shining at about +10 mag. As of May 2015 the comet had faded below mag +13. The comet is periodic with an orbital period of about 61 years .C/2017 U7
C/2017 U7 is a hyperbolic comet (previously classified as A/2017 U7, a hyperbolic asteroid), first observed on 29 October 2017 by astronomers of the Pan-STARRS facility at Haleakala Observatory, Hawaii, United States when the object was 7.8 AU (1.2 billion km) from the Sun. Despite being discovered only 10 days after interstellar asteroid 1I/'Oumuamua, it was not announced until March 2018 (along with C/2018 C2 (Lemmon), which was believed to be another hyperbolic asteroid at the time) as its orbit is not strongly hyperbolic beyond most Oort Cloud comets. Based on the absolute magnitude of 10.6, it may measure tens of kilometers in diameter. As of August 2018, there is only 1 hyperbolic asteroid known, ʻOumuamua, but hundreds of hyperbolic comets are known.C/2018 C2 (Lemmon)
C/2018 C2 (Lemmon) is a hyperbolic comet (previously classified as A/2018 C2, a hyperbolic asteroid). It was first observed on 5 February 2018 by the Mount Lemmon Survey conducted at the Mount Lemmon Observatory near Tucson, Arizona, in the United States. The discovery was announced on 4 March 2018 along with another hyperbolic object, A/2017 U7. Based on the absolute magnitude of 15.1, it may measure several kilometers in diameter. On 22 March 2018 it was determined to be a hyperbolic comet,.C/2018 F4 (PANSTARRS)
C/2018 F4 (PANSTARRS) is a hyperbolic comet (previously classified as A/2018 F4, a hyperbolic asteroid). It was discovered on 17 March 2018 when it was beyond the orbit of Jupiter, 6.4 AU (960 million km) from the Sun. It was quite far from the Sun and turned out to simply be an asteroidal object that was discovered before cometary activity was noticeable. As perihelion (closest approach to the Sun) is inside the orbit of Jupiter, this object should become more active. In April 2018 it was determined to be a hyperbolic comet. Given that the incoming velocity was similar to that of an Oort cloud object, we can very confidently say that it is not of interstellar origin.Hyperbolic asteroid
A hyperbolic asteroid is any sort of asteroid or non-cometary astronomical object observed to have an orbit not bound to the Sun and will have an orbital eccentricity greater than 1 when near perihelion.Interstellar object
An interstellar object is an astronomical object, other than a star or substar, that is located in interstellar space and is not gravitationally bound to a star. The term can also be applied to objects that are on an interstellar trajectory but are temporarily passing close to a star, such as certain asteroids and comets (including exocomets).
Due to present observational difficulties, an interstellar object can usually only be detected if it passes through the Solar System, where it can be distinguished by its strongly hyperbolic trajectory, indicating that it is not gravitationally bound to the Sun. In contrast, gravitationally bound objects follow elliptic orbits around the Sun, like most asteroids, comets, and objects in the Oort cloud.
It is possible for objects orbiting a star to be ejected due to interaction with a third massive body, thereby becoming interstellar objects. Such a process was initiated in early 1980s when C/1980 E1, initially gravitationally bound to the Sun, passed near Jupiter and was accelerated sufficiently to reach escape velocity from the Solar System. This changed its orbit from elliptical to hyperbolic and made it the most eccentric known object at the time, with an eccentricity of 1.057. It is headed for interstellar space.
The first discovered, and to date only known, interstellar object is ʻOumuamua (1I/ʻOumuamua, previously called C/2017 U1 and A/2017 U1). The object has an orbital eccentricity of about 1.20, indicating it did not originate from the Solar System.
Recent research suggests that asteroid (514107) 2015 BZ509 may be a former interstellar object, captured some 4.5 billion years ago, as evidenced by its co-orbital motion with Jupiter and its retrograde orbit around the Sun.List of Pan-STARRS discoveries
PANSTARRS or variation may refer to:
Pan-STARRS, the Panoramic Survey Telescope and Rapid Response System in Hawaii, United States
C/2011 L4 Pan-Starrs
C/2012 K1 (PANSTARRS)
C/2012 S4 (PANSTARRS)
P/2013 P5 (PANSTARRS), Main-Belt Comet
C/2014 G3 (PANSTARRS)
C/2014 Q1 (PANSTARRS)
C/2015 ER61 (PANSTARRS)
C/2016 R2 (PANSTARRS)
C/2017 K2 (PANSTARRS)
C/2018 F4 (PANSTARRS)
311P/PANSTARRS, Asteroid PANSTARRS
1I/2017 U1 (ʻOumuamua), Interstellar Asteroid discovered by Pan-STARRSMichele Bannister
Michele Bannister (born 1986) is an astrophysicist and science communicator at the Queen's University Belfast. Asteroid 10463 Bannister is named after her.Naming of comets
Comets have been observed for the last 2,000 years. During that time, several different systems have been used to assign names to each comet, and as a result many comets have more than one name.
The simplest system names comets after the year in which they were observed (e.g. the Great Comet of 1680). Later a convention arose of using the names of people associated with the discovery (e.g. Comet Hale–Bopp) or the first detailed study (e.g. Halley's Comet) of each comet. During the twentieth century, improvements in technology and dedicated searches led to a massive increase in the number of comet discoveries, which led to the creation of a numeric designation scheme. The original scheme assigned codes in the order that comets passed perihelion (e.g. Comet 1970 II). This scheme operated until 1994, when continued increases in the numbers of comets found each year resulted in the creation of a new scheme. This system, which is still in operation, assigns a code based on the type of orbit and the date of discovery (e.g. C/2012 S1).OGLE-2016-BLG-1190Lb
OGLE-2016-BLG-1190Lb is an extremely massive exoplanet, with a mass about 13.4 times that of Jupiter (MJ), or is, possibly, a low mass brown dwarf, orbiting the G-dwarf star OGLE-2016-BLG-1190L, located about 22,000 light years from Earth, in the constellation of Sagittarius, in the galactic bulge of the Milky Way.“Since the existence of the brown dwarf desert is the signature of different formation mechanisms for stars and planets, the extremely close proximity of OGLE-2016-BLG-1190Lb to this desert raises the question of whether it is truly a ‘planet’ (by formation mechanism) and therefore reacts back upon its role tracing the galactic distribution of planets," according to astronomers reporting the findings.Orbital eccentricity
The orbital eccentricity of an astronomical object is a parameter that determines the amount by which its orbit around another body deviates from a perfect circle. A value of 0 is a circular orbit, values between 0 and 1 form an elliptic orbit, 1 is a parabolic escape orbit, and greater than 1 is a hyperbola. The term derives its name from the parameters of conic sections, as every Kepler orbit is a conic section. It is normally used for the isolated two-body problem, but extensions exist for objects following a Klemperer rosette orbit through the galaxy.Project Lyra
Project Lyra is a feasibility study of a mission to the interstellar object ʻOumuamua, initiated on the 30 October 2017 by the Initiative for Interstellar Studies (i4is).
2017 in space