Wikipedia

Epsilon Indi

Epsilon Indi,Latinizedfrom ε Indi, is astar systemlocated at a distance of approximately 12light-yearsfromEarthin the southernconstellationofIndus.The star has an orange hue and is faintly visible to the naked eye with anapparent visual magnitudeof 4.674.[2]It consists of aK-type main-sequence star,ε Indi A, and twobrown dwarfs,ε Indi Ba and ε Indi Bb, in a wide orbit around it.[14]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.

Epsilon Indi
Location of ε Indi (circled)
Observation data
EpochJ2000.0EquinoxJ2000.0(ICRS)
Constellation Indus
Right ascension 22h03m21.65363s[1]
Declination −56° 47′ 09.5228″[1]
Apparent magnitude(V) 4.674±0.006[2]
Characteristics
Spectral type K5V + T1 + T6[3]
U−Bcolor index 1.00[4]
B−Vcolor index 1.056±0.016[5]
Astrometry
ε Ind A
Radial velocity(Rv)−40.43±0.13[1]km/s
Proper motion(μ)RA:3,966.661(86)mas/yr[1]
Dec.:−2,536.192(92)mas/yr[1]
Parallax(π)274.8431 ± 0.0956mas[1]
Distance11.867 ± 0.004ly
(3.638 ± 0.001pc)
Absolute magnitude(MV)6.89[6]
ε Ind Ba/Bb
Parallax(π)270.6580 ± 0.6896mas[7]
Distance12.05 ± 0.03ly
(3.695 ± 0.009pc)
Orbit[8]
Primaryε Ind Ba
Companionε Ind Bb
Period(P)11.0197 ± 0.0076yr
Semi-major axis(a)661.58 ± 0.37 mas
(2.4058 ± 0.0040 au)
Eccentricity(e)0.54042 ± 0.00063
Inclination(i)77.082 ± 0.032°
Longitude of the node(Ω)147.959 ± 0.023°
Argument of periastron(ω)
(secondary)		328.27 ± 0.12°
Details[9]
ε Ind A
Mass0.782±0.023[10]M☉
Radius0.711±0.005R☉
Luminosity0.21±0.02L☉
Surface gravity(logg)4.63±0.01cgs
Temperature4,649±84K
Metallicity[Fe/H]−0.13±0.06dex
Rotation35.732+0.006
−0.003days[11]
Rotational velocity(vsini)2.00 km/s
Age3.5+0.8
−1.0[8]Gyr
ε Ind Ba/Bb
MassBa:66.92±0.36MJup
Bb:53.25±0.29[8]MJup
RadiusBa: ~0.080–0.081R☉
Bb: ~0.082–0.083[12]R☉
LuminosityBa:2.04×10−5L☉
Bb:5.97×10−6[8]L☉
Surface gravity(logg)Ba: 5.43–5.45
Bb: 5.27–5.33[12]cgs
TemperatureBa: 1,352–1,385 K
Bb: 976–1,011[12]K
Other designations
UGP 544,ε Ind,CD−57°8464,CPD−57°10015,FK5825,GJ845,HD209100,HIP108870,HR8387,SAO247287,LHS67[13]
Database references
SIMBADThe system
A
Bab
Bab (as X-ray source)

ε Indi A has one known planet,ε Indi Ab,with a mass of 6.31Jupiter massesin an elliptical orbit with a period of about 171.3 years. ε Indi Ab is the second-closestJovian exoplanet,afterε Eridani b.The ε Indi system provides a benchmark case for the study of the formation of gas giants and brown dwarfs.[11]

Observation

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Epsilon Indi withSkyMapperand a HubbleNICMOSimage of the brown dwarf binary

The constellation Indus (the Indian) first appeared inJohann Bayer's celestial atlasUranometriain 1603. The 1801 star atlasUranographia,by German astronomerJohann Elert Bode,places ε Indi as one of the arrows being held in the left hand of the Indian.[15]

In 1847,Heinrich Louis d'Arrestcompared the position of this star in several catalogues dating back to 1750, and discovered that it possessed a measureableproper motion.That is, he found that the star had changed position across the celestial sphere over time.[16]In 1882–3, theparallaxof ε Indi was measured by astronomersDavid Gilland William L. Elkin at theCape of Good Hope.They derived a parallax estimate of0.22 ± 0.03arcseconds.[17]In 1923,Harlow Shapleyof theHarvard Observatoryderived a parallax of 0.45 arcseconds.[18]

In 1972, theCopernicus satellitewas used to examine this star for the emission ofultravioletlaser signals. Again, the result was negative.[19]ε Indi leads alist,compiled byMargaret TurnbullandJill Tarterof theCarnegie InstitutioninWashington,of 17,129 nearby stars most likely to have planets that could support complex life.[20]

The star is among five nearby paradigms as K-type stars of a type in a 'sweet spot' between Sun-analog stars and M stars for the likelihood of evolved life, per analysis of Giada Arney from NASA'sGoddard Space Flight Center.[21]

Characteristics

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ε Indi A is amain-sequencestar ofspectral typeK5V. The star has only about three-fourths the mass of the Sun[22]and 71% of theSun's radius.[9]Its surface gravity is slightly higher than the Sun's.[4]Themetallicityof a star is the proportion of elements with higher atomic numbers than helium, being typically represented by the ratio of iron to hydrogen compared to the same ratio for the Sun; ε Indi A is found to have about 87% of the Sun's proportion of iron in itsphotosphere.[3]

Thecoronaof ε Indi A is similar to the Sun, with anX-rayluminosity of 2×1027ergs s−1(2×1020W) and an estimated coronal temperature of 2×106K. Thestellar windof this star expands outward, producing abow shockat a distance of 63AU.Downstream of the bow, the termination shock reaches as far as 140 AU from the star.[23]

Position of Sun andα Centauriin Ursa Major as seen from ε Indi

This star has the third highestproper motionof any star visible to the unaided eye, afterGroombridge 1830and61 Cygni,[24]and the ninth highest overall.[25]This motion will move the star into the constellationTucanaaround 2640 AD.[26]ε Indi A has aspace velocityrelative to the Sun of 86km/s,[4][note 1]which is unusually high for what is considered a young star.[27]It is thought to be a member of the ε Indimoving groupof at least sixteenpopulation Istars.[28]This is an association of stars that have similarspace velocityvectors, and therefore most likely formed at the same time and location.[29]ε Indi will make its closest approach to the Sun in about 17,500 years when it makesperihelionpassage at a distance of around 10.58 light-years (3.245 pc).[30]

As seen from ε Indi, the Sun is a 2.6-magnitude star inUrsa Major,near the bowl of theBig Dipper.[note 2]

Brown dwarfs

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Artist's conception of the Epsilon Indi system showing Epsilon Indi A and its brown-dwarf binary companions. The labels give the initial minimum measurement of the distance between Epsilon Indi A and the binary.

In January 2003, astronomers announced the discovery of abrown dwarfwith a mass of 40 to 60Jupiter massesin orbit around ε Indi A with a projected separation on the sky of about 1,500AU.[31][32]In August 2003, astronomers discovered that this brown dwarf was actually a binary brown dwarf, with an apparent separation of 2.1 AU and an orbital period of about 15 years.[12][33]Both brown dwarfs are ofspectral class T;the more massive component, ε Indi Ba, is of spectral type T1–T1.5 and the less massive component, ε Indi Bb, of spectral type T6.[12]More recent parallax measurements with the Gaia spacecraft place the ε Indi B binary about 11,600 AU (0.183 lightyears) away from ε Indi A, along line of sight from Earth.[7]

Evolutionary models[34]have been used to estimate the physical properties of these brown dwarfs fromspectroscopicandphotometricmeasurements. These yield masses of47 ± 10and28 ± 7times the mass of Jupiter, and radii of0.091 ± 0.005and0.096 ± 0.005solar radii,for ε Indi Ba and ε Indi Bb, respectively.[35]Theeffective temperaturesare 1300–1340Kand 880–940K,while the logg(cm s−1) surface gravities are 5.50 and 5.25, and their luminosities are1.9 × 10−5and4.5 × 10−6theluminosity of the Sun.They have an estimated metallicity of [M/H] = –0.2.[12]

Planetary system

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Main article:Epsilon Indi Ab
The Epsilon Indi A planetary system[36]
Companion
(in order from star) 		Mass Semimajor axis
(AU) 		Orbital period
(years) 		Eccentricity Inclination Radius
b 6.31+0.60
−0.56MJ 		28.4+10
−7.2 		~171.3[note 3] 0.40+0.15
−0.18 		103.7°±2.3° 1.08[a]RJ
Epsilon Indi Ab imaged byJWSTMIRI.The star marks the position of its host star, whose light is blocked by acoronagraph.

The existence of a planetary companion to Epsilon Indi A was suspected since 2002 based onradial velocityobservations.[37]The planetEpsilon Indi Abwas confirmed in 2018[38]and formally published in 2019 along with its detection viaastrometry.[11]

A direct imaging attempt of this planet using theJames Webb Space Telescopewas performed in 2023,[39]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.[40]It has a mass of 6.31Jupiter massesand an elliptical orbit with a period of about 171.3 years.[36]

No excessinfraredradiation that would indicate adebris diskhas been detected around ε Indi.[41]Such a debris disk could be formed from the collisions ofplanetesimalsthat survive from the early period of the star'sprotoplanetary disk.

See also

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Notes

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  1. ^The space velocity components are: U = −77; V = −38, and W = +4. This yields a net space velocity ofkm/s.
  2. ^From ε Indi the Sun would appear on the diametrically opposite side of the sky at the coordinates RA=10h03m21s,Dec=56° 47′ 10″, which is located nearBeta Ursae Majoris.The absolute magnitude of the Sun is 4.8, so, at a distance of 3.63 parsecs, the Sun would have an apparent magnitude.
  3. ^Calculated usinggiven a semi-major axis of 28.4 AU and a host star mass of 0.78M☉
  1. ^Calculated, using theStefan-Boltzmann lawand the planet'seffective temperatureand luminosity, with respect to the being thesolarnominal effective temperature of 5,772K:

References

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  1. ^abcdeVallenari, A.; et al. (Gaia collaboration) (2023)."GaiaData Release 3. Summary of the content and survey properties ".Astronomy and Astrophysics.674:A1.arXiv:2208.00211.Bibcode:2023A&A...674A...1G.doi:10.1051/0004-6361/202243940.S2CID244398875. Gaia DR3 record for this sourceatVizieR.
  2. ^abPaunzen, E. (2015-08-01). "A new catalogue of Strömgren-Crawford uvbyβ photometry".Astronomy and Astrophysics.580:A23.arXiv:1506.04568.Bibcode:2015A&A...580A..23P.doi:10.1051/0004-6361/201526413.ISSN0004-6361.
  3. ^abDemory, Brice-Olivier; Ségransan, Damien; Forveille, Thierry; Queloz, Didier; Beuzit, Jean-Luc; Delfosse, Xavier; Di Folco, Emmanuel; Kervella, Pierre; Le Bouquin, Jean-Baptiste; Perrier, Christian; Benisty, Myriam; Duvert, Gilles; Hofmann, Karl-Heinz; Lopez, Bruno; Petrov, Romain (October 2009). "Mass-radius relation of low and very low-mass stars revisited with the VLTI".Astronomy and Astrophysics.505(1): 205–215.arXiv:0906.0602.Bibcode:2009A&A...505..205D.doi:10.1051/0004-6361/200911976.S2CID14786643.
  4. ^abcKollatschny, W. (1980). "A model atmosphere of the late type dwarf Epsilon INDI".Astronomy and Astrophysics.86(3): 308–314.Bibcode:1980A&A....86..308K.
  5. ^van Leeuwen, F. (2007)."Validation of the new Hipparcos reduction".Astronomy and Astrophysics.474(2): 653–664.arXiv:0708.1752.Bibcode:2007A&A...474..653V.doi:10.1051/0004-6361:20078357.S2CID18759600.
  6. ^Jimenez, Raul; Flynn, Chris; MacDonald, James; Gibson, Brad K. (March 2003). "The Cosmic Production of Helium".Science.299(5612): 1552–1555.arXiv:astro-ph/0303179.Bibcode:2003Sci...299.1552J.doi:10.1126/science.1080866.PMID12624260.S2CID1424666.
  7. ^abVallenari, A.; et al. (Gaia collaboration) (2023)."GaiaData Release 3. Summary of the content and survey properties ".Astronomy and Astrophysics.674:A1.arXiv:2208.00211.Bibcode:2023A&A...674A...1G.doi:10.1051/0004-6361/202243940.S2CID244398875. Gaia DR3 record for this sourceatVizieR.
  8. ^abcd Chen, Minghan; Li, Yiting; Brandt, Timothy D.; Dupuy, Trent J.; Cardoso, Cátia V.; McCaughrean, Mark J. (2022)."Precise Dynamical Masses of ε Indi Ba and Bb: Evidence of Slowed Cooling at the L/T Transition".The Astronomical Journal.163(6): 288.arXiv:2205.08077.Bibcode:2022AJ....163..288C.doi:10.3847/1538-3881/ac66d2.S2CID248834536.
  9. ^abRains, Adam D.; et al. (April 2020)."Precision angular diameters for 16 southern stars with VLTI/PIONIER".Monthly Notices of the Royal Astronomical Society.493(2): 2377–2394.arXiv:2004.02343.Bibcode:2020MNRAS.493.2377R.doi:10.1093/mnras/staa282.
  10. ^ Lundkvist, Mia S.; Kjeldsen, Hans; Bedding, Timothy R.; McCaughrean, Mark J.; Butler, R. Paul; Slumstrup, Ditte; Campante, Tiago L.; Aerts, Conny; Arentoft, Torben; Bruntt, Hans; Cardoso, Cátia V.; Carrier, Fabien; Close, Laird M.; da Silva, João Gomes; Kallinger, Thomas; King, Robert R.; Li Lý, Yaguang á quang; Murphy, Simon J.; Rørsted, Jakob L.; Stello, Dennis (2024-04-01)."Low-amplitude Solar-like Oscillations in the K5 V Star ϵ Indi A".The Astrophysical Journal.964(2): 110.arXiv:2403.04509.Bibcode:2024ApJ...964..110L.doi:10.3847/1538-4357/ad25f2.ISSN0004-637X.
  11. ^abcFeng, 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,S2CID204575783
  12. ^abcdefKing, R. R.; et al. (February 2010),"ɛ Indi Ba, Bb: a detailed study of the nearest known brown dwarfs"(PDF),Astronomy and Astrophysics,510:A99,arXiv:0911.3143,Bibcode:2010A&A...510A..99K,doi:10.1051/0004-6361/200912981,S2CID53550866,However, it seems that derivations of the mass of cool brown dwarfs are uncertain even where estimates of the effective temperature, surface gravity, and luminosity exist.[permanent dead link]
  13. ^"SIMBAD Query Result: LHS 67 -- High proper-motion Star".Centre de Données astronomiques de Strasbourg.Retrieved2007-07-11.
  14. ^Smith, Verne V.; Tsuji, Takashi; Hinkle, Kenneth H.; Cunha, Katia; Blum, Robert D.; Valenti, Jeff A.; Ridgway, Stephen T.; Joyce, Richard R.; Bernath, Peter (2003). "High-resolution infrared spectroscopy of the brown dwarf ε Indi Ba".The Astrophysical Journal Letters.599(2): L107–L110.arXiv:astro-ph/0311237.Bibcode:2003ApJ...599L.107S.doi:10.1086/381248.S2CID117133193.
  15. ^Scholz, Ralf-Dieter; McCaughrean, Mark (2003-01-13)."Discovery of Nearest Known Brown Dwarf".ESO. Archived fromthe originalon September 20, 2008.Retrieved2008-07-02.
  16. ^D'Arrest, M. (1847)."On proper motion of ε Indi".Monthly Notices of the Royal Astronomical Society.8:16.Bibcode:1847MNRAS...8...16D.doi:10.1093/mnras/8.1.16.
  17. ^Callandreau, O.(1886). "Revue des publications astronomiques. Heliometer determinations of Stellar parallax, in the southern hemisphere, by David Gill and W. L. Elkin".Bulletin Astronomique(in French).2(1): 42–44.Bibcode:1885BuAsI...2...42C.
  18. ^Shapley, Harlow (1923). "Epsilon Indi".Harvard College Observatory Bulletin.789(789): 2.Bibcode:1923BHarO.789Q...2S.
  19. ^Lawton, A. T. (1975). "CETI from Copernicus".Spaceflight.17:328–330.Bibcode:1975SpFl...17..328L.
  20. ^Stahl, Jason (January 2007)."20 Things You Didn't Know About... Aliens".Discover. Archived fromthe originalon 2007-02-21.Retrieved2007-03-02.
  21. ^Bill Steigerwald (22 February 2019).""Goldilocks" Stars May be "Just Right" for Finding Habitable Worlds ".NASA.'I find that certain nearby K stars like 61 Cyg A/B, Epsilon Indi, Groombridge 1618, and HD 156026 may be particularly good targets for future biosignature searches,'said Arney.
  22. ^"The 100 nearest star systems".Research Consortium On Nearby Stars.Georgia State University.January 1, 2012.Retrieved2012-06-11.
  23. ^Müller, Hans-Reinhard; Zank, Gary P. (2001)."Modeling the Interstellar Medium-Stellar Wind Interactions of λ Andromedae and ε Indi".The Astrophysical Journal.551(1): 495–506.Bibcode:2001ApJ...551..495M.doi:10.1086/320070.
  24. ^Weaver, Harold F. (1947)."The Visibility of Stars Without Optical Aid".Publications of the Astronomical Society of the Pacific.59(350): 232–243.Bibcode:1947PASP...59..232W.doi:10.1086/125956.
  25. ^Staff (2007-05-04)."High Proper Motion Stars: Interesting Areas to View".ESA.Retrieved2006-08-10.
  26. ^ Moore, Patrick; Rees, Robin (2014).Patrick Moore's Data Book of Astronomy.Cambridge: Cambridge University Press. p. 296.ISBN978-1-139-49522-6.
  27. ^Rocha-Pinto, Helio J.; Maciel, Walter J.; Castilho, Bruno V. (2001). "Chromospherically Young, Kinematically Old Stars".Astronomy and Astrophysics.384(3): 912–924.arXiv:astro-ph/0112452.Bibcode:2002A&A...384..912R.doi:10.1051/0004-6361:20011815.S2CID16982360.
  28. ^Eggen, O. J. (1971)."The zeta Herculis, sigma Puppis, ε Indi, and eta Cephei Groups of Old Disk Population Stars".Publications of the Astronomical Society of the Pacific.83(493): 251–270.Bibcode:1971PASP...83..251E.doi:10.1086/129119.
  29. ^Kollatschny, W. (1980). "A model atmosphere of the late type dwarf Epsilon INDI".Astronomy and Astrophysics.86(3): 308–314.Bibcode:1980A&A....86..308K.
  30. ^Bailer-Jones, C. A. L. (March 2015), "Close encounters of the stellar kind",Astronomy & Astrophysics,575:13,arXiv:1412.3648,Bibcode:2015A&A...575A..35B,doi:10.1051/0004-6361/201425221,S2CID59039482,A35.
  31. ^Scholz, Ralf-Dieter; McCaughrean, Mark (2003-01-13)."Discovery of Nearest Known Brown Dwarf: Bright Southern Star Epsilon Indi Has Cool, Substellar Companion".European Southern Observatory. Archived fromthe originalon October 14, 2007.Retrieved2006-05-24.
  32. ^Scholz, R.-D.; McCaughrean, M. J.; Lodieu, N.; Kuhlbrodt, B. (February 2003). "ε Indi B: A new benchmark T dwarf".Astronomy and Astrophysics.398(3): L29–L33.arXiv:astro-ph/0212487.Bibcode:2003A&A...398L..29S.doi:10.1051/0004-6361:20021847.S2CID119474823.
  33. ^Volk, K.; Blum, R.; Walker, G.; Puxley, P. (2003). "epsilon Indi B".IAU Circular.8188(8188). IAU: 2.Bibcode:2003IAUC.8188....2V.
  34. ^E.g.,Baraffe, I.; Chabrier, G.; Barman, T.; Allard, F.; Hauschildt, P. H. (May 2003). "Evolutionary models for cool brown dwarfs and extrasolar giant planets. The case of HD 209458".Astronomy and Astrophysics.402(2): 701–712.arXiv:astro-ph/0302293.Bibcode:2003A&A...402..701B.doi:10.1051/0004-6361:20030252.S2CID15838318.
  35. ^McCaughrean, M. J.; et al. (January 2004). "ε Indi Ba, Bb: The nearest binary brown dwarf".Astronomy and Astrophysics.413(3): 1029–1036.arXiv:astro-ph/0309256.Bibcode:2004A&A...413.1029M.doi:10.1051/0004-6361:20034292.S2CID15407249.
  36. ^ab Matthews, E. C.; Carter, A. L.; et al. (July 2024)."A temperate super-Jupiter imaged with JWST in the mid-infrared".Nature.633(8031): 789–792.Bibcode:2024Natur.633..789M.doi:10.1038/s41586-024-07837-8.PMC11424479.PMID39048015.
  37. ^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 and Astrophysics.392(2): 671–690.arXiv:astro-ph/0207512.Bibcode:2002A&A...392..671E.doi:10.1051/0004-6361:20020937.S2CID17393347.
  38. ^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].
  39. ^ "A direct detection of the closest Jupiter analog with JWST/MIRI".stsci.edu.STScI.Retrieved31 July2022.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.
  40. ^ "NASA's Webb Images Cold Exoplanet 12 Light-Years Away".nasa.gov.NASA Webb Mission Team.RetrievedJul 24,2024.
  41. ^Trilling, D. E.; et al. (February 2008)."Debris Disks around Sun-like Stars".The Astrophysical Journal.674(2): 1086–1105.arXiv:0710.5498.Bibcode:2008ApJ...674.1086T.doi:10.1086/525514.S2CID54940779.
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