GJ 1151 is a

star A star is an astronomical object comprising a luminous spheroid of plasma (physics), plasma held together by its gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked ...

located in the northern circumpolar constellation of Ursa Major at a distance of 26.2

light year A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 1012 ...

s from the Sun. It has a reddish hue and is too faint to be visible to the naked eye with an apparent visual magnitude of 14.0 The star is moving closer with a

radial velocity The radial velocity or line-of-sight velocity, also known as radial speed or range rate, of a target with respect to an observer is the temporal rate of change, rate of change of the distance or Slant range, range between the two points. It is e ...

of −36 km/s, and has a relatively large

proper motion Proper motion is the astrometric measure of the observed changes in the apparent places of stars or other celestial objects in the sky, as seen from the center of mass of the Solar System, compared to the abstract background of the more dista ...

, traversing the

celestial sphere In astronomy and navigation, the celestial sphere is an abstract sphere that has an arbitrarily large radius and is concentric to Earth. All objects in the sky can be conceived as being projected upon the inner surface of the celestial sphere, ...

at a rate of ·yr⁻¹. This is a small

red dwarf ''Red Dwarf'' is a British science fiction comedy franchise created by Rob Grant and Doug Naylor, which primarily consists of a television sitcom that aired on BBC Two between 1988 and 1999, and on Dave since 2009, gaining a cult following. T ...

star of spectral type dM4.5. It is 2.5 billion years old and is spinning with a

projected rotational velocity Stellar rotation is the angular motion of a star about its axis. The rate of rotation can be measured from the spectrum of the star, or by timing the movements of active features on the surface. The rotation of a star produces an equatorial bulge ...

of 2.0 km/s. The star has 15.4% of the

mass of the Sun The solar mass () is a standard unit of mass in astronomy, equal to approximately . It is often used to indicate the masses of other stars, as well as stellar clusters, nebulae, galaxies and black holes. It is approximately equal to the mass ...

and 19.0% of the Sun's radius, with an

effective temperature The effective temperature of a body such as a star or planet is the temperature of a black body that would emit the same total amount of electromagnetic radiation. Effective temperature is often used as an estimate of a body's surface temperature ...

of 3,143 K.

Planetary system

In 2020, astronomers announced the discovery of radio emissions from the star which are consistent with the star having a magnetic interaction with a planet approximately the size of Earth, revolving in a 1-5 day long orbit. Such an interaction would be analogous to a scaled-up version of the Jupiter-Io magnetic interaction, with GJ 1151 taking the role of Jupiter and its planet the role of Io. Two papers published only a month apart in 2021 discussed planet detection at GJ 1151 by the

radial velocity method Doppler spectroscopy (also known as the radial-velocity method, or colloquially, the wobble method) is an indirect method for finding extrasolar planets and brown dwarfs from radial-velocity measurements via observation of Doppler shifts in t ...

. One claimed the detection of a planet with a minimum mass of and a period of 2 days, supporting the radio emission detection, while the other was unable to confirm this candidate planet, finding that the 2-day signal is likely caused by long-term variability, possibly connected to a more distant planet. This second study placed an upper limit of on the minimum masses of any undetected planets with periods from 1-5 days. In 2023, a different planet was found, with a minimum mass of and a 390-day orbit, along with additional radial velocity variations. This new planet is referred to by the discovery paper as GJ 1151 b, but it is possible that other sources will refer to it as GJ 1151 c to differentiate it from the previous candidate. While the presence of a short-period planet associated with the radio emissions could not be completely ruled out, if such a planet exists its minimum mass must be less than .

References

{{Stars of Ursa Major M-type main-sequence stars Ursa Major (constellation) J11505787+4822395

1151 Year 1151 ( MCLI) was a common year starting on Monday (link will display the full calendar) of the Julian calendar. Events * September 7 – Geoffrey of Anjou dies, and is succeeded by his son Henry, aged 18. * After the Battle of Ghazni ...

Hypothetical planetary systems

Planetary system

See also

References