A rogue planet, also termed a free-floating planet (FFP) or an isolated planetary-mass object (iPMO), is an interstellar object of planetary mass which is not gravitationally bound to any star or brown dwarf. [1] [2] [3] [4]
Rogue planets may originate from planetary systems in which they are formed and later ejected, or they can also form on their own, outside a planetary system. The Milky Way alone may have billions to trillions of rogue planets, a range the upcoming Nancy Grace Roman Space Telescope will likely be able to narrow. [5] [6]
Some planetary-mass objects may have formed in a similar way to stars, and the International Astronomical Union has proposed that such objects be called sub-brown dwarfs. [7] A possible example is Cha 110913−773444, which may either have been ejected and become a rogue planet or formed on its own to become a sub-brown dwarf. [8]
The two first discovery papers use the names isolated planetary-mass objects (iPMO) [9] and free-floating planets (FFP). [10] Most astronomical papers use one of these terms. [11] [12] [13] The term rogue planet is more often used for microlensing studies, which also often uses the term FFP. [14] [15] A press release intended for the public might use an alternative name. The discovery of at least 70 FFPs in 2021, for example, used the terms rogue planet, [16] starless planet, [17] wandering planet [18] and free-floating planet [19] in different press releases.
Isolated planetary-mass objects (iPMO) were first discovered in 2000 by the UK team Lucas & Roche with UKIRT in the Orion Nebula. [10] In the same year the Spanish team Zapatero Osorio et al. discovered iPMOs with Keck spectroscopy in the σ Orionis cluster. [9] The spectroscopy of the objects in the Orion Nebula was published in 2001. [20] Both European teams are now recognized for their quasi-simultaneous discoveries. [21] In 1999 the Japanese team Oasa et al. discovered objects in Chamaeleon I [22] that were spectroscopically confirmed years later in 2004 by the US team Luhman et al. [23]
There are two techniques to discover free-floating planets: direct imaging and microlensing.
Astrophysicist Takahiro Sumi of Osaka University in Japan and colleagues, who form the Microlensing Observations in Astrophysics and the Optical Gravitational Lensing Experiment collaborations, published their study of microlensing in 2011. They observed 50 million stars in the Milky Way by using the 1.8-metre (5 ft 11 in) MOA-II telescope at New Zealand's Mount John Observatory and the 1.3-metre (4 ft 3 in) University of Warsaw telescope at Chile's Las Campanas Observatory. They found 474 incidents of microlensing, ten of which were brief enough to be planets of around Jupiter's size with no associated star in the immediate vicinity. The researchers estimated from their observations that there are nearly two Jupiter-mass rogue planets for every star in the Milky Way. [24] [25] [26] One study suggested a much larger number, up to 100,000 times more rogue planets than stars in the Milky Way, though this study encompassed hypothetical objects much smaller than Jupiter. [27] A 2017 study by Przemek Mróz of Warsaw University Observatory and colleagues, with six times larger statistics than the 2011 study, indicates an upper limit on Jupiter-mass free-floating or wide-orbit planets of 0.25 planets per main-sequence star in the Milky Way. [28]
In September 2020, astronomers using microlensing techniques reported the detection, for the first time, of an Earth-mass rogue planet (named OGLE-2016-BLG-1928) unbound to any star and free floating in the Milky Way galaxy. [15] [29] [30]
Microlensing planets can only be studied by the microlensing event, which makes the characterization of the planet difficult. Astronomers therefore turn to isolated planetary-mass objects (iPMO) that were found via the direct imaging method. To determine a mass of a brown dwarf or iPMO one needs for example the luminosity and the age of an object. [31] Determining the age of a low-mass object has proven to be difficult. It is no surprise that the vast majority of iPMOs are found inside young nearby star-forming regions of which astronomers know their age. These objects are younger than 200 Myrs, are massive (>5 MJ) [4] and belong to the L- and T-dwarfs. [32] [33] There is however a small growing sample of cold and old Y-dwarfs that have estimated masses of 8-20 MJ. [34] Nearby rogue planet candidates of spectral type Y include WISE 0855−0714 at a distance of 7.27±0.13 light-years. [35] If this sample of Y-dwarfs can be characterized with more accurate measurements or if a way to better characterize their ages can be found, the number of old and cold iPMOs will likely increase significantly.
The first iPMOs were discovered in the early 2000s via direct imaging inside young star-forming regions. [36] [9] [20] These iPMOs found via direct imaging formed probably like stars (sometimes called sub-brown dwarf). There might be iPMOs that form like a planet, which are then ejected. These objects will however be kinematically different from their natal star-forming region, should not be surrounded by a circumstellar disk and have high metallicity. [21] None of the iPMOs found inside young star-forming regions show a high velocity compared to their star-forming region. For old iPMOs the cold WISE J0830+2837 [37] shows a Vtan of about 100 km/s, which is high, but still consistent with formation in our galaxy. For WISE 1534–1043 [38] one alternative scenario explains this object as an ejected exoplanet due to its high Vtan of about 200 km/s, but its color suggests it is an old metal-poor brown dwarf. Most astronomers studying massive iPMOs believe that they represent the low-mass end of the star-formation process. [21]
Astronomers have used the Herschel Space Observatory and the Very Large Telescope to observe a very young free-floating planetary-mass object, OTS 44, and demonstrate that the processes characterizing the canonical star-like mode of formation apply to isolated objects down to a few Jupiter masses. Herschel far-infrared observations have shown that OTS 44 is surrounded by a disk of at least 10 Earth masses and thus could eventually form a mini planetary system. [39] Spectroscopic observations of OTS 44 with the SINFONI spectrograph at the Very Large Telescope have revealed that the disk is actively accreting matter, similar to the disks of young stars. [39]
The first discovery of a resolved planetary-mass binary was 2MASS J1119–1137AB. There are however other binaries known, such as 2MASS J1553022+153236AB, [40] [41] WISE 1828+2650, WISE 0146+4234, WISE J0336−0143 (could also be a brown dwarf and a planetary-mass object (BD+PMO) binary), NIRISS-NGC1333-12 [42] and several objects discovered by Zhang et al. [41]
In the Orion Nebula a population of 40 wide binaries and 2 triple systems were discovered. This was surprising for two reasons: The trend of binaries of brown dwarfs predicted a decrease of distance between low mass objects with decreasing mass. It was also predicted that the binary fraction decreases with mass. These binaries were named Jupiter-mass binary objects (JuMBOs). They make up at least 9% of the iPMOs and have a separation smaller than 340 AU. [43] It is unclear how these JuMBOs formed, but an extensive study argued that they formed in situ, like stars. [44] If they formed like stars, then there must be an unknown "extra ingredient" to allow them to form. If they formed like planets and were later ejected, then it has to be explained why these binaries did not break apart during the ejection process. Future measurements with JWST might resolve if these objects formed as ejected planets or as stars. [43] A study by Kevin Luhman reanalysed the NIRCam data and found that most JuMBOs did not appear in his sample of substellar objects. Moreover the color were consistent with reddened background sources or low signal-to-noise sources. Only JuMBO 29 is identified as a good candidate in this work. [45] JuMBO 29 also was observed with NIRSpec and one component was identified as a young M8 source. [46] This spectral type is consistent with a low mass for the age of the Orion Nebula. [45]
There are likely hundreds [47] [43] of known candidate iPMOs, over a hundred [48] [49] [50] objects with spectra and a small but growing number of candidates discovered via microlensing. Some large surveys include:
As of December 2021, the largest-ever group of rogue planets was discovered, numbering at least 70 and up to 170 depending on the assumed age. They are found in the OB association between Upper Scorpius and Ophiuchus with masses between 4 and 13 MJ and age around 3 to 10 million years, and were most likely formed by either gravitational collapse of gas clouds, or formation in a protoplanetary disk followed by ejection due to dynamical instabilities. [47] [16] [51] [18] Follow-up observations with spectroscopy from the Subaru Telescope and Gran Telescopio Canarias showed that the contamination of this sample is quite low (≤6%). The 16 young objects had a mass between 3 and 14 MJ, confirming that they are indeed planetary-mass objects. [50]
In October 2023 an even larger group of 540 planetary-mass object candidates was discovered in the Trapezium Cluster and inner Orion Nebula with JWST. The objects have a mass between 13 and 0.6 MJ. A surprising number of these objects formed wide binaries, which was not predicted. [43]
There are in general two scenarios that can lead to the formation of an isolated planetary-mass object (iPMO). It can form like a planet around a star and is then ejected, or it forms like a low-mass star or brown dwarf in isolation. This can influence its composition and motion. [21]
Objects with a mass of at least one Jupiter mass were thought to be able to form via collapse and fragmentation of molecular clouds from models in 2001. [52] Pre-JWST observations have shown that objects below 3-5 MJ are unlikely to form on their own. [4] Observations in 2023 in the Trapezium Cluster with JWST have shown that objects as massive as 0.6 MJ might form on their own, not requiring a steep cut-off mass. [43] A particular type of globule, called globulettes, are thought to be birthplaces for brown dwarfs and planetary-mass objects. Globulettes are found in the Rosette Nebula and IC 1805. [53] Sometimes young iPMOs are still surrounded by a disk that could form exomoons. Due to the tight orbit of this type of exomoon around their host planet, they have a high chance of 10-15% to be transiting. [54]
Some very young star-forming regions, typically younger than 5 million years, sometimes contain isolated planetary-mass objects with infrared excess and signs of accretion. Most well known is the iPMO OTS 44 discovered to have a disk and being located in Chamaeleon I. Charmaeleon I and II have other candidate iPMOs with disks. [55] [56] [32] Other star-forming regions with iPMOs with disks or accretion are Lupus I, [56] Rho Ophiuchi Cloud Complex, [57] Sigma Orionis cluster, [58] Orion Nebula, [59] Taurus, [57] [60] NGC 1333 [61] and IC 348. [62] A large survey of disks around brown dwarfs and iPMOs with ALMA found that these disks are not massive enough to form earth-mass planets. There is still the possibility that the disks already have formed planets. [57] Studies of red dwarfs have shown that some have gas-rich disks at a relative old age. These disks were dubbed Peter Pan Disks and this trend could continue into the planetary-mass regime. One Peter Pan disk is the 45 Myr old brown dwarf 2MASS J02265658-5327032 with a mass of about 13.7 MJ, which is close to the planetary-mass regime. [63]
Ejected planets are predicted to be mostly low-mass (<30 ME Figure 1 Ma et al.) [64] and their mean mass depends on the mass of their host star. Simulations by Ma et al. [64] did show that 17.5% of 1 M☉ stars eject a total of 16.8 ME per star with a typical (median) mass of 0.8 ME for an individual free-floating planet (FFP). For lower mass red dwarfs with a mass of 0.3 M☉ 12% of stars eject a total of 5.1 ME per star with a typical mass of 0.3 ME for an individual FFP.
Hong et al. [65] predicted that exomoons can be scattered by planet-planet interactions and become ejected exomoons. Higher mass (0.3-1 MJ) ejected FFP are predicted to be possible, but they are also predicted to be rare. [64] Ejection of a planet can occur via planet-planet scatter or due a stellar flyby. Another possibility is the ejection of a fragment of a disk that then forms into a planetary-mass object. [66] Another suggested scenario is the ejection of planets in a tilted circumbinary orbit. Interactions with the central binary and the planets with each other can lead to the ejection of the lower-mass planet in the system. [67]
If a stellar or brown dwarf embryo experiences a halted accretion, it could remain low-mass enough to become a planetary-mass object. Such a halted accretion could occur if the embryo is ejected or if its circumstellar disk experiences photoevaporation near O-stars. Objects that formed via the ejected embryo scenario would have smaller or no disk and the fraction of binaries decreases for such objects. It could also be that free-floating planetary-mass objects for from a combination of scenarios. [66]
Most isolated planetary-mass objects will float in interstellar space forever.
Some iPMOs will have a close encounter with a planetary system. This rare encounter can have three outcomes: The iPMO will remain unbound, it could be weakly bound to the star, or it could "kick out" the exoplanet, replacing it. Simulations have shown that the vast majority of these encounters result in a capture event with the iPMO being weakly bound with a low gravitational binding energy and an elongated highly eccentric orbit. These orbits are not stable and 90% of these objects gain energy due to planet-planet encounters and are ejected back into interstellar space. Only 1% of all stars will experience this temporary capture. [68]
Interstellar planets generate little heat and are not heated by a star. [69] However, in 1998, David J. Stevenson theorized that some planet-sized objects adrift in interstellar space might sustain a thick atmosphere that would not freeze out. He proposed that these atmospheres would be preserved by the pressure-induced far-infrared radiation opacity of a thick hydrogen-containing atmosphere. [70]
During planetary-system formation, several small protoplanetary bodies may be ejected from the system. [71] An ejected body would receive less of the stellar-generated ultraviolet light that can strip away the lighter elements of its atmosphere. Even an Earth-sized body would have enough gravity to prevent the escape of the hydrogen and helium in its atmosphere. [70] In an Earth-sized object the geothermal energy from residual core radioisotope decay could maintain a surface temperature above the melting point of water, [70] allowing liquid-water oceans to exist. These planets are likely to remain geologically active for long periods. If they have geodynamo-created protective magnetospheres and sea floor volcanism, hydrothermal vents could provide energy for life. [70] These bodies would be difficult to detect because of their weak thermal microwave radiation emissions, although reflected solar radiation and far-infrared thermal emissions may be detectable from an object that is less than 1,000 astronomical units from Earth. [72] Around five percent of Earth-sized ejected planets with Moon-sized natural satellites would retain their satellites after ejection. A large satellite would be a source of significant geological tidal heating. [73]
The table below lists rogue planets, confirmed or suspected, that have been discovered. It is yet unknown whether these planets were ejected from orbiting a star or else formed on their own as sub-brown dwarfs. Whether exceptionally low-mass rogue planets (such as OGLE-2012-BLG-1323 and KMT-2019-BLG-2073) are even capable of being formed on their own is currently unknown.
These objects were discovered with the direct imaging method. Many were discovered in young star-clusters or stellar associations and a few old are known (such as WISE 0855−0714). List is sorted after discovery year.
Exoplanet | Mass (MJ) | Age (Myr) | Distance (ly) | Spectral type | Status | Stellar assoc. membership | Discovery |
---|---|---|---|---|---|---|---|
OTS 44 | ~11.5 | 0.5–3 | 554 | M9.5 | Likely a low-mass brown dwarf [36] | Chamaeleon I | 1998 |
S Ori 52 | 2–8 | 1–5 | 1,150 | Age and mass uncertain; may be a foreground brown dwarf | σ Orionis cluster | 2000 [9] | |
Proplyd 061-401 | ~11 | 1 | 1,344 | L4–L5 | Candidate, 15 candidates in total from this work | Orion nebula | 2001 [20] |
S Ori 70 | 3 | 3 | 1150 | T6 | interloper? [21] | σ Orionis cluster | 2002 |
Cha 110913-773444 | 5–15 | 2~ | 529 | >M9.5 | Confirmed | Chamaeleon I | 2004 [74] |
SIMP J013656.5+093347 | 11-13 | 200~ | 20-22 | T2.5 | Candidate | Carina-Near moving group | 2006 [75] [76] |
UGPS J072227.51−054031.2 | 0.66–16.02 [77] [78] | 1000 – 5000 | 13 | T9 | Mass uncertain | none | 2010 |
M10-4450 | 2–3 | 1 | 325 | T | Candidate | rho Ophiuchi cloud | 2010 [79] |
WISE 1828+2650 | 3–6 or 0.5–20 [80] | 2–4 or 0.1–10 [80] | 47 | >Y2 | candidate, could be binary | none | 2011 |
CFBDSIR 2149−0403 | 4–7 | 110–130 | 117–143 | T7 | Candidate | AB Doradus moving group | 2012 [81] |
SONYC-NGC1333-36 | ~6 | 1 | 978 | L3 | candidate, NGC 1333 has two other objects with masses below 15 MJ | NGC 1333 | 2012 [82] |
SSTc2d J183037.2+011837 | 2–4 | 3 | 848–1354 | T? | Candidate, also called ID 4 | Serpens Core cluster [83] (in the Serpens Cloud) | 2012 [11] |
PSO J318.5−22 | 6.24–7.60 [77] [78] | 21–27 | 72.32 | L7 | Confirmed; also known as 2MASS J21140802-2251358 | Beta Pictoris Moving group | 2013 [13] [84] |
2MASS J2208+2921 | 11–13 | 21–27 | 115 | L3γ | Candidate; radial velocity needed | Beta Pictoris Moving group | 2014 [85] |
WISE J1741-4642 | 4–21 | 23–130 | L7pec | Candidate | Beta Pictoris or AB Doradus moving group | 2014 [86] | |
WISE 0855−0714 | 3–10 | >1,000 | 7.1 | Y4 | Age uncertain, but old due to solar vicinity object; [87] candidate even for an old age of 12 Gyrs (age of the universe is 13.8 Gyrs) | none | 2014 [88] |
2MASS J12074836–3900043 | ~15 [89] | 7–13 | 200 | L1 | Candidate; distance needed | TW Hydrae association [90] | 2014 [91] |
SIMP J2154–1055 | 9–11 | 30–50 | 63 | L4β | Age questioned [92] | Argus association | 2014 [93] |
SDSS J111010.01+011613.1 | 10.83–11.73 [77] [78] | 110–130 | 63 | T5.5 | Confirmed [77] | AB Doradus moving group | 2015 [33] |
2MASS J11193254–1137466 AB | 4–8 | 7–13 | ~90 | L7 | Binary candidate, one of the components has a candidate exomoon or variable atmosphere [54] | TW Hydrae Association | 2016 [94] |
WISEA 1147 | 5–13 | 7–13 | ~100 | L7 | Candidate | TW Hydrae Association | 2016 [12] |
USco J155150.2-213457 | 8–10 | 6.907-10 | 104 | L6 | Candidate, low gravity | Upper Scorpius association | 2016 [95] |
Proplyd 133-353 | <13 | 0.5–1 | 1,344 | M9.5 | Candidate with a photoevaporating disk | Orion Nebula | 2016 [59] |
Cha J11110675-7636030 | 3–6 | 1–3 | 520–550 | M9–L2 | Candidate, but could be surrounded by a disk, which could make it a sub-brown dwarf; other candidates from this work | Chamaeleon I | 2017 [32] |
PSO J077.1+24 | 6 | 1–2 | 470 | L2 | Candidate, work also published another candidate in Taurus | Taurus Molecular Cloud | 2017 [96] |
2MASS J1115+1937 | 6+8 −4 | 5–45 | 147 | L2γ | has an accretion disk | Field, possibly ejected | 2017 |
Calar 25 | 11–12 | 120 | 435 | Confirmed | Pleiades | 2018 [97] | |
2MASS J1324+6358 | 10.7–11.8 | ~150 | ~33 | T2 | unusually red and unlikely binary; robust candidate [77] [78] | AB Doradus moving group | 2007, 2018 [98] |
WISE J0830+2837 | 4-13 | >1,000 | 31.3-42.7 | >Y1 | Age uncertain, but old because of high velocity (high Vtan is indicative of an old stellar population), Candidate if younger than 10 Gyrs | none | 2020 [37] |
2MASS J0718-6415 | 3 ± 1 | 16-28 | 30.5 | T5 | Candidate member of the BPMG. Extremely short rotation period of 1.08 hours, comparable to the brown dwarf 2MASS J0348-6022. [99] [100] | Beta Pictoris moving group | 2021 |
DANCe J16081299-2304316 | 3.1–6.3 | 3–10 | 104 | L6 | One of at least 70 candidates published in this work, spectrum similar to HR 8799c | Upper Scorpius association | 2021 [47] [50] |
WISE J2255−3118 | 2.15–2.59 | 24 | ~45 | T8 | very red, candidate [77] [78] | Beta Pictoris moving group | 2011,2021 [49] |
WISE J024124.73-365328.0 | 4.64–5.30 | 45 | ~61 | T7 | candidate [77] [78] | Argus association | 2012, 2021 [49] |
2MASS J0013−1143 | 7.29–8.25 | 45 | ~82 | T4 | binary candidate or composite atmosphere, candidate [77] [78] | Argus association | 2017, 2021 [49] |
SDSS J020742.48+000056.2 | 7.11–8.61 | 45 | ~112 | T4.5 | candidate [77] [78] | Argus association | 2002, 2021 [49] |
2MASSI J0453264-175154 | 12.68–12.98 | 24 | ~99 | L2.5β | low gravity, candidate [77] [78] | Beta Pictoris moving group | 2003, 2023 [77] [78] |
CWISE J0506+0738 | 7 ± 2 | 22 | 104 | L8γ–T0γ | Candidate member of the BPMG. Extreme red near-infrared colors. [101] | Beta Pictoris moving group | 2023 |
These objects were discovered via microlensing. Rogue planets discovered via microlensing can only be studied by the lensing event and are often also consistent with exoplanets in a wide orbit around an unseen star. [102]
Exoplanet | Mass (MJ) | Mass (ME) | Distance (ly) | Status | Discovery |
---|---|---|---|---|---|
OGLE-2012-BLG-1323 | 0.0072–0.072 | 2.3–23 | candidate; distance needed | 2017 [103] [104] [105] [106] | |
OGLE-2017-BLG-0560 | 1.9–20 | 604–3,256 | candidate; distance needed | 2017 [104] [105] [106] | |
MOA-2015-BLG-337L | 9.85 | 3,130 | 23,156 | may be a binary brown dwarf instead | 2018 [107] [108] |
KMT-2019-BLG-2073 | 0.19 | 59 | candidate; distance needed | 2020 [109] | |
OGLE-2016-BLG-1928 | 0.001-0.006 | 0.3–2 | 30,000–180,000 | candidate | 2020 [102] |
OGLE-2019-BLG-0551 | 0.0242-0.3 | 7.69–95 | Poorly characterized [110] | 2020 [110] | |
VVV-2012-BLG-0472L | 10.5 | 3,337 | 3,200 | 2022 [111] | |
MOA-9y-770L | 0.07 | 22.3+42.2 −17.4 | 22,700 | 2023 [112] | |
MOA-9y-5919L | 0.0012 or 0.0024 | 0.37+1.11 −0.27 or 0.75+1.23 −0.46 | 14,700 or 19,300 | 2023 [112] |
Exoplanet | Mass (MJ) | Age (Myr) | Distance (ly) | Spectral type | Status | Stellar assoc. membership | Discovery |
---|---|---|---|---|---|---|---|
J1407b | <6 | <451 | Candidate ALMA detection; although the object's brightness and proximity is consistent with it being the same object that eclipsed the star V1400 Centauri in 2007, follow-up observations by ALMA are needed to confirm whether it is moving, let alone in the right direction. [113] | none | 2012, 2020 [113] |
Brown dwarfs are substellar objects that have more mass than the biggest gas giant planets, but less than the least massive main-sequence stars. Their mass is approximately 13 to 80 times that of Jupiter (MJ)—not big enough to sustain nuclear fusion of ordinary hydrogen (1H) into helium in their cores, but massive enough to emit some light and heat from the fusion of deuterium (2H). The most massive ones can fuse lithium (7Li).
A proplyd, short for ionized protoplanetary disk, is an externally illuminated photoevaporating protoplanetary disk around a young star. Nearly 180 proplyds have been discovered in the Orion Nebula. Images of proplyds in other star-forming regions are rare, while Orion is the only region with a large known sample due to its relative proximity to Earth.
2M1207b is a planetary-mass object orbiting the brown dwarf 2M1207, in the constellation Centaurus, approximately 170 light-years from Earth. It is one of the first candidate exoplanets to be directly observed. It was discovered in April 2004 by the Very Large Telescope (VLT) at the Paranal Observatory in Chile by a team from the European Southern Observatory led by Gaël Chauvin. It is believed to be from 5 to 6 times the mass of Jupiter and may orbit 2M1207 at a distance roughly as far from the brown dwarf as Pluto is from the Sun.
An exomoon or extrasolar moon is a natural satellite that orbits an exoplanet or other non-stellar extrasolar body.
OTS 44 is a free-floating planetary-mass object or brown dwarf located at 530 light-years (160 pc) in the constellation Chamaeleon near the reflection nebula IC 2631. It is among the lowest-mass free-floating substellar objects, with approximately 11.5 times the mass of Jupiter, or approximately 1.1% that of the Sun. Its radius is estimated to be 3.2 or 3.6 times that of Jupiter.
A sub-brown dwarf or planetary-mass brown dwarf is an astronomical object that formed in the same manner as stars and brown dwarfs but that has a planetary mass, therefore by definition below the limiting mass for thermonuclear fusion of deuterium . Some researchers call them rogue planets whereas others call them planetary-mass brown dwarfs.
The Optical Gravitational Lensing Experiment (OGLE) is a Polish astronomical project based at the University of Warsaw that runs a long-term variability sky survey (1992–present). The main goals are the detection and classification of variable stars, discovery of microlensing events, dwarf novae, and studies of the structure of the Galaxy and the Magellanic Clouds. Since the project began in 1992, it has discovered a multitude of extrasolar planets, together with the first planet discovered using the transit method (OGLE-TR-56b) and gravitational microlensing. The project has been led by professor Andrzej Udalski since its inception.
Microlensing Observations in Astrophysics (MOA) is a collaborative project between researchers in New Zealand and Japan, led by Professor Yasushi Muraki of Nagoya University. They use microlensing to observe dark matter, extra-solar planets, and stellar atmospheres from the Southern Hemisphere. The group concentrates especially on the detection and observation of gravitational microlensing events of high magnification, of order 100 or more, as these provide the greatest sensitivity to extrasolar planets. They work with other groups in Australia, the United States and elsewhere. Observations are conducted at New Zealand's Mt. John University Observatory using a 1.8 m (70.9 in) reflector telescope built for the project.
NGC 1333 is a reflection nebula located in the northern constellation Perseus, positioned next to the southern constellation border with Taurus and Aries. It was first discovered by German astronomer Eduard Schönfeld in 1855. The nebula is visible as a hazy patch in a small telescope, while a larger aperture will show a pair of dark nebulae designated Barnard 1 and Barnard 2. It is associated with a dark cloud L1450. Estimates of the distance to this nebula range from 980–1,140 ly (300–350 pc).
A circumbinary planet is a planet that orbits two stars instead of one. The two stars orbit each other in a binary system, while the planet typically orbits farther from the center of the system than either of the two stars. In contrast, circumstellar planets in a binary system have stable orbits around one of the two stars, closer in than the orbital distance of the other star. Studies in 2013 showed that there is a strong hint that a circumbinary planet and its stars originate from a single disk.
A planetary-mass object (PMO), planemo, or planetary body is, by geophysical definition of celestial objects, any celestial object massive enough to achieve hydrostatic equilibrium, but not enough to sustain core fusion like a star.
SIMP J013656.5+093347 is a brown dwarf or planetary mass object at 19.9 light-years from Earth in the constellation Pisces. It belongs to the spectral class T2.5 and its position shifts due to its proper motion annually by about 1.24 arcsec in the right ascension.
An exocomet, or extrasolar comet, is a comet outside the Solar System, which includes rogue comets and comets that orbit stars other than the Sun. The first exocomets were detected in 1987 around Beta Pictoris, a very young A-type main-sequence star. There are now a total of 27 stars around which exocomets have been observed or suspected.
PSO J318.5−22 is an extrasolar object of planetary mass that does not orbit a parent star, it is an analog to directly imaged young gas giants. There is no consensus yet among astronomers whether the object should be referred to as a sub-brown dwarf, as a rogue planet or as a young brown dwarf. It is approximately 80 light-years away and belongs to the Beta Pictoris moving group. The object was discovered in 2013 in images taken by the Pan-STARRS PS1 wide-field telescope. PSO J318.5-22's age is inferred to be 23 million years, the same age as the Beta Pictoris moving group. Based on its calculated temperature and age, it is classified under the brown dwarf spectral type L7.
A circumplanetary disk is a torus, pancake or ring-shaped accumulation of matter composed of gas, dust, planetesimals, asteroids or collision fragments in orbit around a planet. They are reservoirs of material out of which moons may form. Such a disk can manifest itself in various ways.
A Peter Pan disk is a circumstellar disk around a star or brown dwarf that appears to have retained enough gas to form a gas giant planet for much longer than the typically assumed gas dispersal timescale of approximately 5 million years. Several examples of such disks have been observed to orbit stars with spectral types of M or later. The presence of gas around these disks has generally been inferred from the total amount of radiation emitted from the disk at infrared wavelengths, and/or spectroscopic signatures of hydrogen accreting onto the star. To fit one specific definition of a Peter Pan disk, the source needs to have an infrared "color" of , an age of >20 Myr and spectroscopic evidence of accretion.