Epsilon Indi

Starbox begin
name=Epsilon IndiStarbox observe
epoch = J2000.0 (ICRS)
constell = Indus
ra = RA|22|03|21.6571cite web
url=http://simbad.u-strasbg.fr/simbad/sim-id?Ident=epsilon%20indi
title=SIMBAD Query Result: LHS 67 -- High proper-motion Star
publisher=Centre de Données astronomiques de Strasbourg
accessdate=2007-07-11 ]
dec = DEC|−56|47|09.514
appmag_v = 4.69Starbox character
class = K4.5V
b-v = 1.06cite journal |last=Kollatschny |first=W. |title=A model atmosphere of the late type dwarf Epsilon INDI |journal=Astronomy and Astrophysics |year=1980 |volume=86 |issue=3 |ages=308-314 |url=http://adsabs.harvard.edu/abs/1980A&A....86..308K |accessdate=2007-07-11 ]
u-b=1.00
variable = "None"Starbox astrometry
radial_v = −40.4
prop_mo_ra = 3,961.41
prop_mo_dec = −2,538.33
parallax = 275.79
p_error = 0.69
parallax_footnote =
absmag_v = 6.89Ref_label|C|c|noneStarbox detail
mass=0.77cite web |author=Staff |date=2007-06-08 |url=http://www.chara.gsu.edu/RECONS/ |title=List of the Nearest 100 Stellar Systems |publisher=Research Consortium on Nearby Stars | accessdate=2007-07-11 ]
radius=0.76cite journal |author=Johnson, H. M.; Wright, C. D. |title=Predicted infrared brightness of stars within 25 parsecs of the sun |journal=Astrophysical Journal Supplement Series |year=1983 |volume=53 |pages=643-711 |url=http://adsabs.harvard.edu/abs/1983ApJS...53..643J | accessdate=2007-07-11 |doi=10.1086/190905 — see p. 701]
luminosity=0.17Ref_label|D|d|none
temperature=4,280
metal=cite journal
last=Kotoneva | first=Eira
coauthors=Flynn, Chris; Jimenez, Raul
title=Luminosity-metallicity relation for stars on the lower main sequence
journal=Monthly Notices of the Royal Astronomical Society
year=2002 | volume=335 | issue=4 | pages=1147-1157
url=http://arxiv.org/abs/astro-ph/0203118v1
accessdate=2008-07-01 ]
gravity=4.65 ± 0.15
rotation=23 days (0.7 km/s)
age=1.3 × 10⁹ [cite journal
author=Lachaume, R.; Dominik, C.; Lanz, T.; Habing, H. J.
title=Age determinations of main-sequence stars: combining different methods
journal=Astronomy and Astrophysics
year=1999 | volume=348 | pages=897-909
url=http://adsabs.harvard.edu/abs/1999A&A...348..897L
accessdate=2007-07-12 — This paper gives a median log age = 9.11, with a range of min = 8.91 and max = 9.31. This corresponds to 1.3 Gyr, with an error range of 0.8–2.0 Gyr.] Starbox catalog
names = CP(D) −57°10015, GCTP 5314.00, GJ 845, HD 209100, HIP 108870, HR 8387, LHS 67, SAO 247287, FK5 825, UGP 544.Starbox reference
Simbad = HD+209100
ARICNS =

Epsilon Indi (ε Ind / ε Indi) is an orange dwarf star approximately 12 light-years away in the constellation of Indus. As seen from Epsilon Indi, the Sun is a 2nd magnitude star in Ursa Major, near the bowl of the Big Dipper.Ref_label|A|a|none As of 2003, two brown dwarfs were found orbiting the star.

Observation

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 Epsilon Indi as one of the arrows being held in the left hand of the Indian. [cite web
last=Scholz | first=Ralf-Dieter
coauthors=McCaughrean, Mark | date=2003-01-13
url=http://www.eso.org/public/outreach/press-rel/pr-2003/pr-01-03.html
title=Discovery of Nearest Known Brown Dwarf
publisher=ESO | accessdate=2008-07-02 ]

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. [cite journal
last=D'Arrest | first=M.
title=On proper motion of ε Indi
journal=Monthly Notices of the Royal Astronomical Society
year=1847 | volume=8 | pages=16
url=http://articles.adsabs.harvard.edu/abs/1847MNRAS...8...16D
accessdate=2008-07-01 ] In 1882-3, the parallax of Epsilon Indi was measured by astronomers David Gill and William L. Elkin at the Cape of Good Hope. They derived a parallax estimate of .22±.03 arcseconds. [cite journal
last=Callandreau | first=O.
title=Revue des publications astronomiques. Heliometer determinations of Stellar parallax, in the southern hemisphere, by David Gill and W. L. Elkin
journal=Bulletin Astronomique | language=fr
year=1886 | volume=2 | issue=1 | pages=42-44
url=http://adsabs.harvard.edu/abs/1885BuAsI...2...42C
accessdate=2008-07-01 ] In 1923, Harlow Shapley of the Harvard Observatory derived a parallax of 0.45 arcseconds. [cite journal
last=Shapley | first=Harlow | title=Epsilon Indi
journal=Harvard College Observatory Bulletin
year=1923 | issue=789 | pages=2
url=http://articles.adsabs.harvard.edu/abs/1923BHarO.789Q...2S
accessdate=2008-07-02 ]

During Project Ozma in 1960, this star was examined for artificial radio signals, but none were found. [cite book
first=Robert | last=Burnham
coauthors=Luft, Herbert A. | year=1978
title=Burnham's Celestial Handbook: An Observer's Guide to the Universe Beyond the Solar System
publisher=Courier Dover Publications
isbn=0486235688 ] In 1972, the Copernicus satellite was used to examine this star for the emission of ultraviolet laser signals. Again, the result was negative. [cite journal
last=Lawton | first=A. T. | title=CETI from Copernicus
journal=Spaceflight | year=1975 | volume=17 | pages=328-330
url=http://adsabs.harvard.edu/abs/1975SpFl...17..328L
accessdate=2008-07-02 ] Epsilon 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. [cite web
last = Stahl | first = Jason | month = January | year = 2007
url = http://www.discover.com/issues/jan-07/departments/20-things-aliens/
title = 20 Things You Didn't Know About... Aliens
publisher = Discover | accessdate = 2007-03-02 ]

Characteristics

Epsilon Indi is a dwarf star of spectral type K4.5V. The star has only about three-fourths the mass of the Sun. Its surface gravity is slightly higher than the Sun's. The metallicity of a star is the proportion of elements with higher atomic numbers than helium. This is typically represented by the ratio of iron to hydrogen compared to the same ratio for the Sun. Epsilon Indi is found to have about 79% of the Sun's proportion of Iron in its photosphere.

The corona of Epsilon Indi is similar to the Sun, with an X-ray luminosity L_x = 2e|27 ergs s^-1 and an estimated coronal temperature of 2e|6 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. [cite journal
last=Müller | first=Hans-Reinhard | coauthors=Zank, Gary P.
title=Modeling the Interstellar Medium-Stellar Wind Interactions of λ Andromedae and ε Indi
journal=The Astrophysical Journal | year=2001
volume=551 | pages=495–506 | doi=10.1086/320070 ]

This star has the third highest proper motion of any star visible to the unaided eye (after Groombridge 1830 and 61 Cygni) [cite journal
last=Weaver | first=Harold F.
title=The Visibility of Stars Without Optical Aid
journal=Publications of the Astronomical Society of the Pacific
year=1947 | volume=59 | issue=350 | pages=232–243
url=http://adsabs.harvard.edu/abs/1947PASP...59..232W
accessdate=2007-02-04 ] and the ninth highest overall. [cite web
author=Staff | date=2007-05-04
url=http://www.rssd.esa.int/index.php?project=HIPPARCOS&page=areas
title=High Proper Motion Stars: Interesting Areas to View
publisher=ESA | accessdate=2006-08-10 ] It has a space velocity relative to the Sun of 86 km/s,Ref_label|B|b|none which is unusually high for what is considered a young star. [cite conference
first = Helio J. | last = Rocha-Pinto
coauthors=Maciel, Walter J.; Castilho, Bruno V.
title = Chromospherically Young, Kinematically Old Stars
booktitle = Astrophysical Ages and Times Scales
pages = 364-
publisher = Astronomical Society of the Pacific
year = 2001 | url = http://arxiv.org/abs/astro-ph/0112452
accessdate = 2007-01-08 ] It is thought to be a member of the ε Indi moving group of at least sixteen population I stars. [cite journal
last = Eggen | first = O. J.
title=The zeta Herculis, sigma Puppis, ε Indi, and eta Cephei Groups of Old Disk Population Stars
journal=Publications of the Astronomical Society of the Pacific
year=1971 | volume=83 | issue=493 | pages=251-270
url=http://adsabs.harvard.edu/abs/1971PASP...83..251E ] This is an association of stars that have similar space velocity vectors, and therefore most likely formed at the same time and location. [cite journal
last=Kollatschny | first=W.
title=A model atmosphere of the late type dwarf Epsilon INDI
journal=Astronomy and Astrophysics
year=1980 | volume=86 | issue=3 | pages=308-314
url=http://adsabs.harvard.edu/abs/1980A&A....86..308K
accessdate=2008-07-01 ]

Companions

In January 2003, astronomers announced the discovery of a brown dwarf with a mass of 40 to 60 Jupiter masses in orbit around Epsilon Indi at a distance of at least 1500 astronomical units. [cite news
last=Scholz | first=Ralf-Dieter
coauthors=McCaughrean, Mark | date=2003-01-13
title=Discovery of Nearest Known Brown Dwarf: Bright Southern Star Epsilon Indi Has Cool, Substellar Companion
publisher=European Southern Observatory
url=http://www.eso.org/public/outreach/press-rel/pr-2003/pr-01-03.html
accessdate=2006-05-24] [cite journal
last=Scholz | first=R.-D.
coauthors=McCaughrean, M. J.; Lodieu, N.; Kuhlbrodt, B.
title=ε Indi B: A new benchmark T dwarf
journal=Astronomy and Astrophysics
month=February | year=2003 | volume=398 | pages=L29–L33
url=http://adsabs.harvard.edu/abs/2003A%26A...398L..29S
accessdate=2008-06-24 ] In August 2003, astronomers discovered that this brown dwarf was actually a binary brown dwarf, with an apparent separation of 2.1 AU. [cite journal
last=Volk | first=K.
coauthors=Blum, R.; Walker, G.; Puxley, P. | year=2003
url=http://adsabs.harvard.edu/abs/2003IAUC.8188....2V
journal=International Astronomical Union Circular
issue=8188 | title=epsilon Indi B | publisher=IAU
accessdate=2006-11-29 ] Both brown dwarfs are of spectral class T; the more massive, ε Indi Ba, has been classified as spectral type T1V, while its less massive companion, Epsilon Indi Bb, has been classified as spectral type T6V.

Evolutionary models [E.g., cite journal
last=Baraffe | first=I.
coauthors=Chabrier, G.; Barman, T.; Allard, F.; Hauschildt, P. H.
title=Evolutionary models for cool brown dwarfs and extrasolar giant planets. The case of HD 209458
journal=Astronomy and Astrophysics
month=May | year=2003 | volume=402 | pages=701–712
url=http://adsabs.harvard.edu/abs/2003A%26A...402..701B
accessdate=2008-06-24 ] 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, radii of 0.091 ± 0.005 and 0.096 ± 0.005 solar radii, and effective temperature of 1280 ± 40 K and 850 ± 20 K for Epsilon Indi Ba and Epsilon Indi Bb, respectively. [cite journal
author=McCaughrean, M. J. "et al"
title=ε Indi Ba, Bb: The nearest binary brown dwarf
journal=Astronomy and Astrophysics
month=January | year=2004 | volume=413 | pages=1029-1036
url=http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2004A%26A...413.1029M
doi=10.1051/0004-6361:20034292 ]

Measurements of the radial velocity of Epsilon Indi appear to show a trend that indicated the presence of a planetary companion with an orbital period of more than 20 years. A visual search using the ESO's Very Large Telescope found one potential candidate. However, a subsequent examination by the Hubble Space Telescope NICMOS showed that this was a background object. Thus, no other companions have yet been found orbiting this star. [cite journal
last=Geißler | first=K.
coauthors=Kellner, S.; Brandner, W.; Masciadri, E.; Hartung, M.; Henning, T.; Lenzen, R.; Close, L.; Endl, M.; Kürster, M.
title=A direct and differential imaging search for sub-stellar companions to epsilon Indi A
journal=Astronomy and Astrophysics | year=2007
volume=461 | issue=2 | pages=665-668
url=http://adsabs.harvard.edu/abs/2007A%26A...461..665G
accessdate=2008-07-02 ]

See also

* Double planet
* Epsilon Indi in fiction
* List of nearest stars

Notes

References

External links

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** [http://www.extrasolar.net/planettour.asp?StarCatId=browndwarf&PlanetId=294 Epsilon Indi Ba]
** [http://www.extrasolar.net/planettour.asp?StarCatId=browndwarf&PlanetId=295 Epsilon Indi Bb]
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