Epsilon Indi: Difference between revisions
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| Simbad3=*+eps+Ind+B|sn3=Bab | | Simbad3=*+eps+Ind+B|sn3=Bab | ||
| Simbad4=1WGA+J2203.9-5647|sn4=Bab (as X-ray source) | | Simbad4=1WGA+J2203.9-5647|sn4=Bab (as X-ray source) | ||
| NSTED= | | NSTED=HR_8387 | ||
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==Observation== | ==Observation== | ||
[[File:Epsilon Indi.png|thumb|left|Epsilon Indi with [[SkyMapper]] and a Hubble [[Near Infrared Camera and Multi-Object Spectrometer|NICMOS]] image of the brown dwarf binary]] | [[File:Epsilon Indi.png|thumb|left|Epsilon Indi with [[SkyMapper]] and a Hubble [[Near Infrared Camera and Multi-Object Spectrometer|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.<ref name= | 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.<ref name="eso0303"/> | ||
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.<ref name="D'Arrest1847"/> In 1882–3, the [[parallax]] of ε Indi was measured by astronomers [[David Gill (astronomer)|David Gill]] and William L. Elkin at the [[Cape of Good Hope]]. They derived a parallax estimate of {{nowrap|0.22 ± 0.03 }}[[arcsecond]]s.<ref name="Callandreau1886"/> In 1923, [[Harlow Shapley]] of the [[Harvard Observatory]] derived a parallax of 0.45 arcseconds.<ref name="Shapley1923"/> | 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.<ref name="D'Arrest1847"/> In 1882–3, the [[parallax]] of ε Indi was measured by astronomers [[David Gill (astronomer)|David Gill]] and William L. Elkin at the [[Cape of Good Hope]]. They derived a parallax estimate of {{nowrap|0.22 ± 0.03 }}[[arcsecond]]s.<ref name="Callandreau1886"/> In 1923, [[Harlow Shapley]] of the [[Harvard Observatory]] derived a parallax of 0.45 arcseconds.<ref name="Shapley1923"/> | ||
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==Brown dwarfs== | ==Brown dwarfs== | ||
[[Image:Artist's Conception of Epsilon Indi System (labelled).jpg|thumb|left|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.]] | [[Image:Artist's Conception of Epsilon Indi System (labelled).jpg|thumb|left|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.<ref name="NOIRLab"/>]] | ||
In January 2003, astronomers announced the discovery of a [[brown dwarf]] with a mass of 40 to 60 [[Jupiter mass]]es in orbit around ε Indi A with a projected separation on the sky of about 1,500 [[astronomical unit|AU]].<ref name="ScholzA"/><ref name="ScholzB"/> 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.<ref name=aaa510/><ref name="Volk2003"/> Both brown dwarfs are of [[T dwarf|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.<ref name=aaa510/> 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.<ref name="Gaia3b"/> | In January 2003, astronomers announced the discovery of a [[brown dwarf]] with a mass of 40 to 60 [[Jupiter mass]]es in orbit around ε Indi A with a projected separation on the sky of about 1,500 [[astronomical unit|AU]].<ref name="ScholzA"/><ref name="ScholzB"/> 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.<ref name=aaa510/><ref name="Volk2003"/> Both brown dwarfs are of [[T dwarf|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.<ref name=aaa510/> 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.<ref name="Gaia3b"/> | ||
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==See also== | ==See also== | ||
* [[List of nearest stars and brown dwarfs]] | * [[List of nearest stars and brown dwarfs]] | ||
* [[List of nearest stars by spectral type#List of nearest K-type stars|List of nearest K-type stars]] | |||
== Notes == | == Notes == | ||
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<ref name="Smith et al">{{cite journal| title=High-resolution infrared spectroscopy of the brown dwarf ε Indi Ba| first1=Verne V.| last1=Smith| first2=Takashi| last2=Tsuji| first3=Kenneth H.| last3=Hinkle| first4=Katia| last4=Cunha| first5=Robert D.| last5=Blum| first6=Jeff A.| last6=Valenti| first7=Stephen T.| last7=Ridgway| first8=Richard R.| last8=Joyce| first9=Peter| last9=Bernath| year=2003| journal=The Astrophysical Journal Letters| volume=599| pages=L107–L110| number=2| doi=10.1086/381248| arxiv=astro-ph/0311237| bibcode=2003ApJ...599L.107S| s2cid=117133193}}</ref> | <ref name="Smith et al">{{cite journal| title=High-resolution infrared spectroscopy of the brown dwarf ε Indi Ba| first1=Verne V.| last1=Smith| first2=Takashi| last2=Tsuji| first3=Kenneth H.| last3=Hinkle| first4=Katia| last4=Cunha| first5=Robert D.| last5=Blum| first6=Jeff A.| last6=Valenti| first7=Stephen T.| last7=Ridgway| first8=Richard R.| last8=Joyce| first9=Peter| last9=Bernath| year=2003| journal=The Astrophysical Journal Letters| volume=599| pages=L107–L110| number=2| doi=10.1086/381248| arxiv=astro-ph/0311237| bibcode=2003ApJ...599L.107S| s2cid=117133193}}</ref> | ||
<ref name= | <ref name="eso0303">{{cite press release | author=<!--Not stated--> | title=Discovery of Nearest Known Brown Dwarf | url=https://www.eso.org/public/news/eso0303/ | publisher=[[European Southern Observatory]] | date=2003-01-13 | access-date=2025-06-14}}</ref> | ||
<ref name=Trilling2008>{{cite journal | author=Trilling, D. E. | display-authors=etal | title=Debris Disks around Sun-like Stars | journal=The Astrophysical Journal | volume=674 | issue=2 | pages=1086–1105 | date=February 2008 | doi=10.1086/525514 | bibcode=2008ApJ...674.1086T | arxiv=0710.5498| s2cid=54940779 }}</ref> | <ref name=Trilling2008>{{cite journal | author=Trilling, D. E. | display-authors=etal | title=Debris Disks around Sun-like Stars | journal=The Astrophysical Journal | volume=674 | issue=2 | pages=1086–1105 | date=February 2008 | doi=10.1086/525514 | bibcode=2008ApJ...674.1086T | arxiv=0710.5498| s2cid=54940779 }}</ref> | ||
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}}</ref> | }}</ref> | ||
<ref name=Feng2024>{{Cite journal |last1=Feng |first1=Fabo | <ref name=Feng2024>{{Cite journal |last1=Feng |first1=Fabo |last2=Xiao |first2=Guang-Yao |last3=Jones |first3=Hugh R A |last4=Jenkins |first4=James S |last5=Pena |first5=Pablo |last6=Sun |first6=Qinghui |date=2024-12-19 |title=Lessons learned from the detection of wide companions by radial velocity and astrometry |journal=Monthly Notices of the Royal Astronomical Society |volume=539 |issue=4 |pages=3180–3200 |doi=10.1093/mnras/staf689 |doi-access=free |arxiv=2412.14542 |issn=0035-8711}}</ref> | ||
<ref name="NOIRLab">{{cite press release | author=<!--Not stated--> | title=Gemini Detects Something "Cool" in Our Neighborhood: Closest Known Brown Dwarf has a Companion | url=https://noirlab.edu/public/announcements/geminiann04016/ | publisher=[[NOIRLab]] | date=2004-10-27 | access-date=2025-06-13}}</ref> | |||
}} | }} | ||
Latest revision as of 19:05, 14 June 2025
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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.
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
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
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.[10] 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 2Template:E ergs s−1 (2Template:E W) and an estimated coronal temperature of 2Template:E 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]
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 Template:Convert.[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
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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.[32][33] 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][34] 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[35] 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.[36] 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
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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.[41]
No excess infrared radiation that would indicate a debris disk has been detected around ε Indi.[42] 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
Notes
Template:Reflist Template:NOTELIST
References
External links
- Discovery of Nearest Known Brown Dwarf (eso0303 : 13 January 2003)
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- Epsilon Indi Ab at The Extrasolar Planets Encyclopaedia. Retrieved 2018-07-02.
Template:Nearest systems Template:Stars of Indus
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- Pages with script errors
- Pages with broken file links
- K-type main-sequence stars
- Planetary systems with one confirmed planet
- T-type brown dwarfs
- Local Bubble
- Indus (constellation)
- Bayer objects
- Durchmusterung objects
- Gliese and GJ objects
- Henry Draper Catalogue objects
- Hipparcos objects
- Bright Star Catalogue objects
- Pages with reference errors