Epsilon Indi

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. ==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 which is unusually high for what is considered a young star. ==Brown dwarfs==

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. 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. 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. 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. Evolutionary models have been used to estimate the physical properties of these brown dwarfs from spectroscopic and photometric measurements. These yield masses of and times the mass of Jupiter, and radii of and solar radii, for ε Indi Ba and ε Indi Bb, respectively. 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 and the luminosity of the Sun. They have an estimated metallicity of [M/H] = –0.2. ==Planetary system==

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. The planet Epsilon Indi Ab was confirmed in 2018 and formally published in 2019 along with its detection via astrometry. A direct imaging attempt of this planet using the James Webb Space Telescope was performed in 2023, 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. It was found to have a mass of 6.31 Jupiter masses and an elliptical orbit with a period of about 171.3 years. Later observations found the orbit to be shorter and closer to circular, with a period of to years. This difference is attributed to a more careful treatment of the data. No excess infrared radiation that would indicate a debris disk has been detected around ε Indi. 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==