Epsilon Indi Ab

Last updated
Epsilon Indi Ab
Epsilon Indi Ab (MIRI Image).png
Epsilon Indi Ab imaged by JWST MIRI. The star motif marks the position of its host star; whose light is blocked by a coronagraph.
Discovery [1]
Discovered by Fabo Feng, et al.
Discovery date21 March 2018 (suspected since 2002)
Radial velocity
Orbital characteristics [2] [lower-alpha 1]
28.4+10
−7.2  AU
Eccentricity 0.40+0.15
−0.18
~173.6 years [lower-alpha 2]
Inclination 103.7°±2.3°
Star Epsilon Indi A
Physical characteristics [2]
1.08 RJup [lower-alpha 3]
Mass 6.31+0.60
−0.56  MJ
Temperature 275  K (2  °C; 35  °F)

    Epsilon Indi Ab is a gas giant exoplanet orbiting the star Epsilon Indi A, about 11.9 light-years away in the constellation of Indus. The planet was confirmed to exist in 2018. [1] It orbits at around 28 AU (almost as far as Neptune from the Sun) with a period of around 174 years and a relatively high eccentricity of 0.4, and has a mass around 6 times that of Jupiter. [2] It was directly imaged using the James Webb Space Telescope in 2023 [3] and the image was released in 2024. [4]

    Contents

    As of 2024, Epsilon Indi Ab is the nearest exoplanet to be directly imaged, and with a temperature of about 275  K (2  °C ; 35  °F ), is also the coolest exoplanet to be directly imaged, and cooler than all but one imaged brown dwarf (the exception being the planetary-mass WISE 0855−0714). [4] It is predicted, based on evolutionary models, to have a luminosity around to 6.31×10−8  L☉ . [2]

    The Epsilon Indi system also contains a pair of brown dwarfs, Epsilon Indi Ba and Bb, at a wide separation from the primary star. As such, this system provides a benchmark case for the study of the formation of gas giants and brown dwarfs. [1]

    History of observations

    The first evidence of Epsilon Indi Ab was found in 2002 when measurements of the radial velocity of Epsilon Indi by Endl et al. appeared to show a trend that indicated a planetary companion with an orbital period of more than 20 years. A substellar object with a minimum mass of 1.6  MJ and orbital separation of roughly 6.5 AU was within the parameters of the highly approximate data. [5]

    A longer study of radial velocity, using the HARPS echelle spectrometer, to follow up on Endl's findings, was published in a paper by M. Zechmeister et al. in 2013. The findings confirm that, quoting the paper, "ε Ind A has a steady long-term trend still explained by a planetary companion". [6]

    This refined the radial-velocity trend observed and indicated a planetary companion with an orbital period greater than 30 years and a minimum mass of 0.97  MJ. The radial-velocity trend was observed through all the observations taken using the HARPS spectrometer, but due to the long period predicted for just one orbit of the object around ε Indi A, more than 30 years, the phase coverage was not yet complete. [6]

    In March 2018, a preprint was posted to arXiv that confirmed the existence of Epsilon Indi Ab using radial velocity measurements. [1] In December 2019, the confirmation of this planet, along with updated parameters from both radial velocity and astrometry, was published by Fabo Feng et al. in Monthly Notices of the Royal Astronomical Society . This study found a semi-major axis of about 11.6 AU, an orbital period of about 45 years, an eccentricity of about 0.26, and a mass of 3.25 MJ. [7] Updated orbital solutions were published in 2023, finding a higher eccentricity. [8] [9]

    A direct imaging attempt of this planet using the James Webb Space Telescope was performed in 2023, [3] and the image was released in 2024. The detected planet's mass and orbit are different from what was predicted based on radial velocity and astrometry observations. [4] The JWST and VLT/VISIR observations imply a super-Jupiter with a mass of about 6 Jupiter masses. The object is fainter than expected in the shorter wavelengths, which might be due to absorption by methane, carbon dioxide, and carbon monoxide commonly found in giant planets. This might be confirmed in the future with a spectrum. Alternatively this could be explained with a cloudy atmosphere. [10] A second direct imaging attempt on this system to confirm the nature of this planet has been approved. [11] The new orbital parameters were calculated with archived radial velocity data, the Hipparcos-Gaia astrometry of the host star and the position of the planet from the images. The planet has a semi-major axis of around 30 AU, an eccentricity of 0.4 and an inclination of 104°. The planet-star separation is 4.1 arcsec in JWST MIRI data and 4.8 arcsec in VLT VISIR data. It is undetected in VLT NaCo observations. [2] The temperature of 275 K is slightly warmer or similar to the nearby Y-dwarf WISE J0855−0714 (225 to 260 K or 285 K), making Epsilon Indi Ab likely one of the coldest objects to be directly imaged outside the solar system. At this temperature, which is warmer than Jupiter (Teff=125 K), [12] but colder than 350 K, it is predicted that such an exoplanet could have water ice clouds and lower layers of sulfide clouds. [13]

    See also

    Notes

    1. ↑ While more complete orbital solutions have been published in earlier work, they are significantly discrepant from the most recent orbital solution including imaging data, so only parameters from the most recent solution are included here.
    2. ↑ Calculated using given a semi-major axis of 28.4 AU and a host star mass of 0.76 M☉
    3. ↑ Calculated, using the Stefan-Boltzmann law and the planet's effective temperature and luminosity, with respect to the solar nominal effective temperature of 5,772  K:

    Related Research Articles

    <span class="mw-page-title-main">Epsilon Indi</span> Star system in the constellation of Indus

    Epsilon Indi, Latinized from ε Indi, is a star system located at a distance of approximately 12 light-years from Earth in the southern constellation of Indus. The star has an orange hue and is faintly visible to the naked eye with an apparent visual magnitude of 4.674. It consists of a K-type main-sequence star, ε Indi A, and two brown dwarfs, ε Indi Ba and ε Indi Bb, in a wide orbit around it. The brown dwarfs were discovered in 2003. ε Indi Ba is an early T dwarf (T1) and ε Indi Bb a late T dwarf (T6) separated by 0.6 arcseconds, with a projected distance of 1460 AU from their primary star.

    <span class="mw-page-title-main">Gliese 229</span> Star in the constellation Lepus

    Gliese 229 is a binary system composed of a red dwarf and the second brown dwarf seen by astronomers, 18.8 light years away in the constellation Lepus. The primary component has 58% of the mass of the Sun, 69% of the Sun's radius, and a very low projected rotation velocity of 1 km/s at the stellar equator.

    HD 28185 is a yellow dwarf star similar to the Sun located 128 light-years away from Earth in the constellation Eridanus. The designation HD 28185 refers to its entry in the Henry Draper catalogue. The star is known to possess one long-period extrasolar planet.

    HD 38529 is a binary star approximately 138 light-years away in the constellation of Orion.

    <span class="mw-page-title-main">Methods of detecting exoplanets</span>

    Any planet is an extremely faint light source compared to its parent star. For example, a star like the Sun is about a billion times as bright as the reflected light from any of the planets orbiting it. In addition to the intrinsic difficulty of detecting such a faint light source, the light from the parent star causes a glare that washes it out. For those reasons, very few of the exoplanets reported as of January 2024 have been observed directly, with even fewer being resolved from their host star.

    Pi Mensae, also known as HD 39091, is a G-dwarf star in the constellation of Mensa. This star has a high proper motion. The apparent magnitude is 5.67, which can be visible to the naked eye in exceptionally dark, clear skies. It is nearly 60 light-years away. The star is slightly larger than the Sun in terms of mass, size, luminosity, temperature and metallicity, and is about 730 million years younger. It hosts three known planets.

    ρ Indi, Latinised as Rho Indi, is a yellow-hued star in the constellation Indus. With an apparent visual magnitude of +6.05 it is, barely, a naked eye star, not visible in the northern hemisphere outside the tropics. Based upon an annual parallax shift of 37.46 mas, it is located 87 light-years from the Sun. The star is moving closer to the Sun with a radial velocity of −2 km/s.

    HD 219828 is a star with two exoplanetary companions in the constellation of Pegasus. With an apparent visual magnitude of 8.04, it is an eighth magnitude star that is too dim to be readily visible to the naked eye. The star is located at a distance of approximately 237 light years from the Sun based on parallax measurements, but is drifting closer with a radial velocity of −24 km/s.

    <span class="mw-page-title-main">Epsilon Eridani b</span> Gas giant orbiting Epsilon Eridani

    Epsilon Eridani b, also known as AEgir [sic], is an exoplanet approximately 10.5 light-years away orbiting the star Epsilon Eridani, in the constellation of Eridanus. The planet was discovered in 2000, and as of 2024 remains the only confirmed planet in its planetary system. It orbits at around 3.5 AU with a period of around 7.6 years, and has a mass around 0.6 times that of Jupiter. As of 2023, both the Extrasolar Planets Encyclopaedia and the NASA Exoplanet Archive list the planet as 'confirmed'.

    HD 4113 is a dual star system in the southern constellation of Sculptor. It is too faint to be viewed with the naked eye, having an apparent visual magnitude of 7.88. The distance to this star, as estimated by parallax measurements, is 137 light years. It is receding away from the Sun with a radial velocity of +5 km/s.

    HD 190228 is a star with an orbiting substellar companion in the northern constellation of Vulpecula. Its apparent magnitude is 7.30 – too faint to be seen with the naked eye – and the absolute magnitude is 3.34. Based on parallax measurements, it is located at a distance of 205 light-years from the Sun. The system is drifting closer with a radial velocity of −50 km/s.

    HD 8673 is a binary star in the northern constellation of Andromeda. It has an apparent magnitude and absolute magnitude of 6.34 and 3.56 respectively. Based upon an annual parallax shift of 26.2 mas, the system is located around 124.5 light years away. The system is moving further from the Earth with a heliocentric radial velocity of +19 km/s. A sub-stellar companion was detected in 2005; it could either be an exoplanet or a brown dwarf.

    HD 23596 b is an exoplanet approximately 170 light years away in the constellation Perseus. The planet is very massive, with a minimum mass 7.8 times that of Jupiter, classifying it as mid-superjovian. Based on its mass, the planet would probably be a gas giant with no solid surface. The planet orbits at the average distance of 2.83 AU, taking 1565 days to complete its orbit with average velocity of 19.7 km/s. The eccentricity of the planet's orbit is higher than all the planets in the Solar System, bringing as close as 2.00 AU to as far as 3.66 AU from the parent star.

    HD 175167 is a star with an exoplanet companion in the southern constellation of Pavo. It is too faint to be visible with the naked eye at an apparent visual magnitude of 8.01. The system is located at a distance of 232 light-years from the Sun based on parallax measurements, and it is drifting further away with a radial velocity of 5 km/s. It shows a high proper motion, traversing the celestial sphere at an angular rate of 0.190 arcsec yr−1.

    HD 175167 b is an exoplanet orbiting HD 175167, which is a G type star within the Pavo constellation 232 light-years away from the Earth. The planet was discovered by the Magellan Planet Search Program as the astronomical object fit the Keplerian orbital model. During the observations 13 doppler velocity tests were conducted, which showed this object's mass was at least 7.8 Jovian-masses and its orbit has a high eccentricity. The exoplanet takes 3.53 years to complete a full stellar orbit.

    HD 98649 is a star with an orbiting exoplanet in the southern Crater constellation. Based on parallax measurements, it is located at a distance of 137.5 light years from the Sun. The system is drifting further away with a heliocentric radial velocity of 4.3 km/s. With an apparent visual magnitude of +8.00, it is too faint to be viewed with the naked eye. The system has a relatively high proper motion, traversing the celestial sphere at an angular rate of 0.24″·yr−1.

    <span class="mw-page-title-main">Luhman 16</span> Binary brown dwarf system in the constellation Vela

    Luhman 16 is a binary brown-dwarf system in the southern constellation Vela at a distance of 6.51 light-years from the Sun. These are the closest-known brown dwarfs and the closest system found since the measurement of the proper motion of Barnard's Star in 1916, and the third-closest-known system to the Sun. The primary is of spectral type L7.5 and the secondary of type T0.5 ± 1. The masses of Luhman 16 A and B are 35.4 and 29.4 Jupiter masses, respectively, and their ages are estimated to be 400–800 million years. Luhman 16 A and B orbit each other at a distance of about 3.5 astronomical units with an orbital period of approximately 26.6 years.

    Beta Pictoris c is the second exoplanet discovered orbiting the young star Beta Pictoris, located approximately 63 light-years away from Earth in the constellation of Pictor. Its mass is around nine times that of Jupiter, and it orbits at around 2.7 astronomical units (AU) from Beta Pictoris, about 3.5 times closer to its parent star than Beta Pictoris b. It has an orbital period of 1,200 days. The orbit of Beta Pictoris c is moderately eccentric, with an eccentricity of 0.24.

    HD 217786 is a binary star system in the equatorial constellation of Pisces. With an apparent visual magnitude of 7.78, it requires binoculars or a small telescope to view. The system is located at a distance of 181 light-years from the Sun based on parallax, and is drifting further away with a radial velocity of +10 km/s. Kinematically, the star system belongs to the thin disk population of the Milky Way.

    HD 7449 is a binary star system about 126 light-years way. The primary star, HD 7449 A, is a main-sequence star belonging to the spectral class F9.5. It is younger than the Sun. The primary star is slightly depleted of heavy elements, having 80% of solar abundance.

    References

    1. 1 2 3 4 Feng, Fabo; Tuomi, Mikko; Jones, Hugh R. A. (23 March 2018). "Detection of the closest Jovian exoplanet in the Epsilon Indi triple system". arXiv: 1803.08163 [astro-ph.EP].
    2. 1 2 3 4 5 Matthews, E. C.; Carter, A. L.; et al. (July 2024). "A temperate super-Jupiter imaged with JWST in the mid-infrared". Nature . doi: 10.1038/s41586-024-07837-8 . PMID   39048015.
    3. 1 2 "A direct detection of the closest Jupiter analog with JWST/MIRI". stsci.edu. STScI . Retrieved 31 July 2022. We will collect the first direct images of a radial velocity planet, by targeting Eps Indi Ab with JWST/MIRI. [...] Our simulations confirm that we will detect Eps Indi Ab's thermal emission at high confidence, regardless of its cloud properties or thermal evolution.
    4. 1 2 3 "NASA's Webb Images Cold Exoplanet 12 Light-Years Away". nasa.gov. NASA Webb Mission Team. Retrieved Jul 24, 2024.
    5. ↑ Endl, M.; Kürster, M.; Els, S.; Hatzes, A. P.; Cochran, W. D.; Dennerl, K.; Döbereiner, S. (2002). "The planet search program at the ESO Coudé Echelle spectrometer. III. The complete Long Camera survey results". Astronomy & Astrophysics . 392 (2): 671–690. arXiv: astro-ph/0207512 . Bibcode:2002A&A...392..671E. doi:10.1051/0004-6361:20020937. S2CID   17393347.
    6. 1 2 Zechmeister, M.; Kürster, M; Endl, M.; Lo Curto, G.; Hartman, H.; Nilsson, H.; Henning, T.; Hatzes, A.; Cochran, W. D. (April 2013). "The planet search programme at the ESO CES and HARPS. IV. The search for Jupiter analogues around solar-like stars". Astronomy & Astrophysics . 552: 62. arXiv: 1211.7263 . Bibcode:2013A&A...552A..78Z. doi:10.1051/0004-6361/201116551. S2CID   53694238.
    7. ↑ Feng, Fabo; Anglada-Escudé, Guillem; Tuomi, Mikko; Jones, Hugh R. A.; Chanamé, Julio; Butler, Paul R.; Janson, Markus (14 October 2019), "Detection of the nearest Jupiter analog in radial velocity and astrometry data", Monthly Notices of the Royal Astronomical Society , 490 (4): 5002–5016, arXiv: 1910.06804 , Bibcode:2019MNRAS.490.5002F, doi: 10.1093/mnras/stz2912 , S2CID   204575783
    8. ↑ Philipot, F.; Lagrange, A.-M.; et al. (January 2023). "Updated characterization of long-period single companion by combining radial velocity, relative astrometry, and absolute astrometry". Astronomy & Astrophysics. 670: A65. arXiv: 2301.01263 . Bibcode:2023A&A...670A..65P. doi:10.1051/0004-6361/202245396. S2CID   255393653.
    9. ↑ Feng, Fabo; Butler, R. Paul; et al. (July 2023). "Revised orbits of the two nearest Jupiters". Monthly Notices of the Royal Astronomical Society . 525 (1): 607–619. arXiv: 2307.13622 . Bibcode:2023MNRAS.525..607F. doi: 10.1093/mnras/stad2297 .
    10. ↑ "Webb images nearest super-Jupiter, opening a new window to exoplanet research". www.mpia.de. Retrieved 2024-07-24.
    11. ↑ "Confirmation of the closest directly detected exoplanet: a super-Jupiter orbiting Eps Ind A". stsci.edu. STScI . Retrieved 1 March 2024. JWST Cycle 1 images of Eps Ind A reveal a candidate companion that is consistent in color and magnitude with a massive (~10Mjup) planet. However, the position angle and mass of the candidate is different than expected from RV/astrometric models of the companion orbit - perhaps suggesting there are two giant planets in this system, with only one of these detected in the MIRI images.
    12. ↑ Coulter, Daniel J.; Barnes, Jason W.; Fortney, Jonathan J. (2022-11-01). "Jupiter and Saturn as Spectral Analogs for Extrasolar Gas Giants and Brown Dwarfs". The Astrophysical Journal Supplement Series. 263 (1): 15. arXiv: 2208.05541 . Bibcode:2022ApJS..263...15C. doi: 10.3847/1538-4365/ac886a . ISSN   0067-0049.
    13. ↑ Morley, Caroline V.; Marley, Mark S.; Fortney, Jonathan J.; Lupu, Roxana; Saumon, Didier; Greene, Tom; Lodders, Katharina (2014-05-01). "Water Clouds in Y Dwarfs and Exoplanets". The Astrophysical Journal. 787 (1): 78. arXiv: 1404.0005 . Bibcode:2014ApJ...787...78M. doi:10.1088/0004-637X/787/1/78. ISSN   0004-637X.
    This page is based on this Wikipedia article
    Text is available under the CC BY-SA 4.0 license; additional terms may apply.
    Images, videos and audio are available under their respective licenses.