Wikipedia

Epsilon Indi

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.[2] 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.[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
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Indus
Right ascension 22h 03m 21.65363s[1]
Declination −56° 47′ 09.5228″[1]
Apparent magnitude (V) 4.674±0.006[2]
Characteristics
Spectral type K5V + T1 + T6[3]
U−B color index 1.00[4]
B−V color 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 ± 0.0956 mas[1]
Distance11.867 ± 0.004 ly
(3.638 ± 0.001 pc)
Absolute magnitude (MV)6.89[6]
ε Ind Ba/Bb
Parallax (π)270.6580 ± 0.6896 mas[7]
Distance12.05 ± 0.03 ly
(3.695 ± 0.009 pc)
Orbit[8]
Primaryε Ind Ba
Companionε Ind Bb
Period (P)11.0197 ± 0.0076 yr
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±0.005 R☉
Luminosity0.21±0.02 L☉
Surface gravity (log g)4.63±0.01 cgs
Temperature4,649±84 K
Metallicity [Fe/H]−0.13±0.06 dex
Rotation35.732+0.006
−0.003 days[11]
Rotational velocity (v sin i)2.00 km/s
Age3.5+0.8
−1.0[8] Gyr
ε Ind Ba/Bb
MassBa: 66.92±0.36 MJup
Bb: 53.25±0.29[8] MJup
RadiusBa: ~0.080–0.081 R☉
Bb: ~0.082–0.083[12] R☉
LuminosityBa: 2.04×10−5 L☉
Bb: 5.97×10−6[8] L☉
Surface gravity (log g)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, FK5 825, GJ 845, HD 209100, HIP 108870, HR 8387, SAO 247287, LHS 67[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 6.31 Jupiter masses in an elliptical orbit with a period of about 171.3 years. ε Indi Ab is the second-closest Jovian exoplanet, after ε Eridani b. The ε Indi system provides a benchmark case for the study of the formation of gas giants and brown dwarfs.[11]

Observation

edit
 
Epsilon Indi with SkyMapper and a Hubble NICMOS image of the brown dwarf binary

The constellation Indus (the Indian) first appeared in Johann Bayer's celestial atlas Uranometria in 1603. The 1801 star atlas Uranographia, by German astronomer Johann 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'Arrest compared the position of this star in several catalogues dating back to 1750, and discovered that it possessed a measureable proper motion. That is, he found that the star had changed position across the celestial sphere over time.[16] In 1882–3, the parallax of ε Indi was measured by astronomers David Gill and William L. Elkin at the Cape of Good Hope. They derived a parallax estimate of 0.22 ± 0.03 arcseconds.[17] In 1923, Harlow Shapley of the Harvard Observatory derived a parallax of 0.45 arcseconds.[18]

In 1972, the Copernicus satellite was used to examine this star for the emission of ultraviolet laser signals. Again, the result was negative.[19] ε Indi leads a list, compiled by Margaret Turnbull and Jill Tarter of the Carnegie Institution in Washington, 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's Goddard Space Flight Center.[21]

Characteristics

edit

ε Indi A is a main-sequence star of spectral type K5V. The star has only about three-fourths the mass of the Sun[22] and 71% of the Sun's radius.[9] Its surface gravity is slightly higher than the Sun's.[4] The metallicity of 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 its photosphere.[3]

The corona of ε Indi A is similar to the Sun, with an X-ray luminosity of 2×1027 ergs s−1 (2×1020 W) and an estimated coronal temperature of 2×106 K. The stellar wind of this star expands outward, producing a bow shock at a distance of 63 AU. Downstream of the bow, the termination shock reaches as far as 140 AU from the star.[23]

 
Position of Sun and α Centauri in Ursa Major as seen from ε Indi

This star has the third highest proper motion of any star visible to the unaided eye, after Groombridge 1830 and 61 Cygni,[24] and the ninth highest overall.[25] This motion will move the star into the constellation Tucana around 2640 AD.[26] ε Indi A has a space velocity relative to the Sun of 86 km/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 Indi moving group of at least sixteen population I stars.[28] This is an association of stars that have similar space velocity vectors, 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 makes perihelion passage 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 in Ursa Major, near the bowl of the Big Dipper.[note 2]

Brown dwarfs

edit
 
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 a brown dwarf with a mass of 40 to 60 Jupiter masses in orbit around ε Indi A with a projected separation on the sky of about 1,500 AU.[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 of spectral 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 from spectroscopic and photometric measurements. These yield masses of 47 ± 10 and 28 ± 7 times the mass of Jupiter, and radii of 0.091 ± 0.005 and 0.096 ± 0.005 solar radii, for ε Indi Ba and ε Indi Bb, respectively.[35] The effective temperatures are 1300–1340 K and 880–940 K, while the log g (cm s−1) surface gravities are 5.50 and 5.25, and their luminosities are 1.9 × 10−5 and 4.5 × 10−6 the luminosity of the Sun. They have an estimated metallicity of [M/H] = –0.2.[12]

Planetary system

edit
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
−0.56 MJ 		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 by JWST MIRI. The star marks the position of its host star, whose light is blocked by a coronagraph.

The existence of a planetary companion to Epsilon Indi A was suspected since 2002 based on radial velocity observations.[37] The planet Epsilon Indi Ab was confirmed in 2018[38] and formally published in 2019 along with its detection via astrometry.[11]

A direct imaging attempt of this planet using the James Webb Space Telescope was 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 6.31 Jupiter masses and an elliptical orbit with a period of about 171.3 years.[36]

No excess infrared radiation that would indicate a debris disk has been detected around ε Indi.[41] Such a debris disk could be formed from the collisions of planetesimals that survive from the early period of the star's protoplanetary disk.

See also

edit

Notes

edit
  1. ^ The space velocity components are: U = −77; V = −38, and W = +4. This yields a net space velocity of   km/s.
  2. ^ From ε Indi the Sun would appear on the diametrically opposite side of the sky at the coordinates RA=10h 03m 21s, Dec=56° 47′ 10″, which is located near Beta 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 using   given a semi-major axis of 28.4 AU and a host star mass of 0.78 M☉
  1. ^ Calculated, using the Stefan-Boltzmann law and the planet's effective temperature and luminosity, with respect to the being the solar nominal effective temperature of 5,772 K: 

References

edit
  1. ^ a b c d e Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data 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. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  2. ^ a b Paunzen, 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. ISSN 0004-6361.
  3. ^ a b Demory, 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. S2CID 14786643.
  4. ^ a b c 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.
  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. S2CID 18759600.
  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. PMID 12624260. S2CID 1424666.
  7. ^ a b Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data 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. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  8. ^ a b c d 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. S2CID 248834536.
  9. ^ a b Rains, 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 李, Yaguang 亚光; 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. ISSN 0004-637X.
  11. ^ a b c 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
  12. ^ a b c d e f King, 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, S2CID 53550866, 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. Retrieved 2007-07-11.
  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. S2CID 117133193.
  15. ^ Scholz, Ralf-Dieter; McCaughrean, Mark (2003-01-13). "Discovery of Nearest Known Brown Dwarf". ESO. Archived from the original on September 20, 2008. Retrieved 2008-07-02.
  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 from the original on 2007-02-21. Retrieved 2007-03-02.
  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. Retrieved 2012-06-11.
  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. Retrieved 2006-08-10.
  26. ^ Moore, Patrick; Rees, Robin (2014). Patrick Moore's Data Book of Astronomy. Cambridge: Cambridge University Press. p. 296. ISBN 978-1-139-49522-6.
  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. S2CID 16982360.
  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, S2CID 59039482, 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 from the original on October 14, 2007. Retrieved 2006-05-24.
  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. S2CID 119474823.
  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. S2CID 15838318.
  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. S2CID 15407249.
  36. ^ a b 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. PMC 11424479. PMID 39048015.
  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. S2CID 17393347.
  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. 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.
  40. ^ "NASA's Webb Images Cold Exoplanet 12 Light-Years Away". nasa.gov. NASA Webb Mission Team. Retrieved Jul 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. S2CID 54940779.
edit


Retrieved from "https://en.wikipedia.org/w/index.php?title=Epsilon_Indi&oldid=1255783759"