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 with two
exoplanet
An exoplanet or extrasolar planet is a planet outside the Solar System. The first possible evidence of an exoplanet was noted in 1917 but was not recognized as such. The first confirmation of detection occurred in 1992. A different planet, init ...
ary companions in the southern
constellation
A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object.
The origins of the e ...
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 ...
parallax
Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight and is measured by the angle or semi-angle of inclination between those two lines. Due to foreshortening, nearby objects ...
measurements, and is drifting further away 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 +87.8 km/s. This star is too faint to be viewed with the naked eye, having an apparent visual magnitude of 11.98 and an
absolute magnitude
Absolute magnitude () is a measure of the luminosity of a celestial object on an inverse Logarithmic scale, logarithmic Magnitude (astronomy), astronomical magnitude scale. An object's absolute magnitude is defined to be equal to the apparent mag ...
of 11.06.
This is an
M-type main-sequence star
''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. ...
with a
stellar classification
In astronomy, stellar classification is the classification of stars based on their stellar spectrum, spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a Prism (optics), prism or diffraction grati ...
of M2.5V. Photometric calibrations and infrared spectroscopic measurements indicate that the star is enriched in heavy elements compared to the Sun. The star is estimated to be roughly five billion years old and has a low
activity level
Activity may refer to:
* Action (philosophy), in general
* Human activity: human behavior, in sociology behavior may refer to all basic human actions, economics may study human economic activities and along with cybernetics and psychology may stu ...
for a star of its class. It has 42% of the mass and radius of the Sun and is spinning with a
rotation period
The rotation period of a celestial object (e.g., star, gas giant, planet, moon, asteroid) may refer to its sidereal rotation period, i.e. the time that the object takes to complete a single revolution around its axis of rotation relative to the ...
of 69 days. The star is radiating 2.2% of the Sun's luminosity from its
photosphere
The photosphere is a star's outer shell from which light is radiated.
The term itself is derived from Ancient Greek roots, φῶς, φωτός/''phos, photos'' meaning "light" and σφαῖρα/''sphaira'' meaning "sphere", in reference to it ...
at 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 3,510 K.
Planetary system
In 2007, a
jovian planet
The giant planets constitute a diverse type of planet much larger than Earth. They are usually primarily composed of low-boiling-point materials (volatiles), rather than rock or other solid matter, but massive solid planets can also exist. Ther ...
(designated
Gliese 317 b
Gliese 317 b is an extrasolar planet approximately 50 light-years away in the constellation of Pyxis. The planet was reported in July 2007 to be orbiting the red dwarf star Gliese 317. The planet is a Jovian planet that orbits at about 95% of ...
) was announced to orbit the star. The planet orbits about 95% the
distance
Distance is a numerical or occasionally qualitative measurement of how far apart objects or points are. In physics or everyday usage, distance may refer to a physical length or an estimation based on other criteria (e.g. "two counties over"). ...
between Earth to the Sun. Despite this, it takes about 1.9 years, due to the lower mass of the central M dwarf. Astrometric measurements on Gliese 317 provided a significant update to the distance, putting the star at 15.3 pc, which is 65% further out than previously assumed. Using mass-luminosity calibrations, the new distance implies the star is significantly more massive and so are the planet candidates. The same astrometric measurements allowed to constrain the orbital inclination and put an upper limit to the mass of Gliese 317 b (98% confidence level) of 2.5 .
The second planet in the system was also confirmed with the additional new RV measurements, but the period and orbital parameters of Gliese 317 c were very uncertain (P>2000 days). A stability analysis on this putative system suggest that the pair of gas giant planets are in a 4:1 mean motion resonance. The second planet, remote from its host star, is a good candidate for direct imaging. Revised elements of this companion were presented in 2020, demonstrating this is a Jupiter analog.
See also
*
Gliese 649
Gliese 649 is a small star with an orbiting exoplanet in the constellation Hercules. It has an apparent visual magnitude of 9.7, which is too faint to be seen with the naked eye. The system is located at a distance of 33.9 light y ...
*
Gliese 849
, - style="background-color: #A0B0FF;" colspan="3"
, Planet
, - bgcolor="#FFFAFA"
, Gliese 849b , data
Gliese 849, or GJ 849, is a small, solitary star in the equatorial constellation of Aquarius. It has a reddish hue and is invis ...
*
HD 108874
HD 108874 is a yellow dwarf star (spectral type G5 V) in the constellation of Coma Berenices. It is 195 light years from Earth and has two extrasolar planets that are possibly in a 9:2 orbital resonance.
Star
HD 108874 is probably billio ...
*
List of exoplanets discovered between 2000–2009
This is a List of exoplanets discovered between 2000–2009.
For exoplanets detected only by radial velocity, the mass value is actually a lower limit. (See Minimum mass for more information)
Specific exoplanet lists
References
2000-2009
...
- Gliese 317 b
*
List of exoplanets discovered in 2020
This list of exoplanets discovered in 2020 is a list of confirmed exoplanets that were first observed in 2020.
For exoplanets detected only by radial velocity, the listed value for mass is a lower limit. See Minimum mass for more information.
...