36 Ursae Majoris
Encyclopedia
36 Ursae Majoris is a yellowish main sequence
star
of spectral type F8V. The star is 1.2 times more massive than the Sun
and has a 1.2 times larger radius. Its age is around 2 billion years.
The star is thought to have a stellar companion B of spectral type K7V at wide separation (1500 AU
s). An optical companion C (spectral type K2V) is located at 49,000 AU
s, but is probably not bound to the system.
According to Nelson & Angel (1998), 36 Ursae Majoris could host one or two (or at least three) jovian planets (or even brown dwarfs) at wide separations from the host star, with orbital periods of 10-15, 25 and 50 years respectively. The authors have set upper limits of 1.1-2, 5.3 and 24 Jupiter masses for the putative planetary objects. Also Lippincott (1983) had previously noticed the possible presence of a massive unseen companion (with nearly 70 times the mass of Jupiter
, just below the stellar regime, thus a brown dwarf
). Putative parameters for the substellar object show an orbital period of 18 years and quite a high eccentricity (e=0.8).
Even Campbell et al. 1988 inferred the existence of planetary objects or even brown dwarfs less massive than 14 Jupiter masses around 36 Ursae Majoris.
Nevertheless no certain planetary companion has yet been detected or confirmed. The McDonald Observatory
team has set limits to the presence of one or more planets with masses between 0.13 and 2.5 Jupiter masses and average separations spanning between 0.05 and 5.2 AU.
Main sequence
The main sequence is a continuous and distinctive band of stars that appears on plots of stellar color versus brightness. These color-magnitude plots are known as Hertzsprung–Russell diagrams after their co-developers, Ejnar Hertzsprung and Henry Norris Russell...
star
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...
of spectral type F8V. The star is 1.2 times more massive than the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
and has a 1.2 times larger radius. Its age is around 2 billion years.
The star is thought to have a stellar companion B of spectral type K7V at wide separation (1500 AU
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
s). An optical companion C (spectral type K2V) is located at 49,000 AU
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
s, but is probably not bound to the system.
Hunt for substellar objects
According to Nelson & Angel (1998), 36 Ursae Majoris could host one or two (or at least three) jovian planets (or even brown dwarfs) at wide separations from the host star, with orbital periods of 10-15, 25 and 50 years respectively. The authors have set upper limits of 1.1-2, 5.3 and 24 Jupiter masses for the putative planetary objects. Also Lippincott (1983) had previously noticed the possible presence of a massive unseen companion (with nearly 70 times the mass of Jupiter
Jupiter
Jupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is a gas giant with mass one-thousandth that of the Sun but is two and a half times the mass of all the other planets in our Solar System combined. Jupiter is classified as a gas giant along with Saturn,...
, just below the stellar regime, thus a brown dwarf
Brown dwarf
Brown dwarfs are sub-stellar objects which are too low in mass to sustain hydrogen-1 fusion reactions in their cores, which is characteristic of stars on the main sequence. Brown dwarfs have fully convective surfaces and interiors, with no chemical differentiation by depth...
). Putative parameters for the substellar object show an orbital period of 18 years and quite a high eccentricity (e=0.8).
Even Campbell et al. 1988 inferred the existence of planetary objects or even brown dwarfs less massive than 14 Jupiter masses around 36 Ursae Majoris.
Nevertheless no certain planetary companion has yet been detected or confirmed. The McDonald Observatory
McDonald Observatory
The McDonald Observatory is an astronomical observatory located near the unincorporated community of Fort Davis in Jeff Davis County, Texas, United States. The facility is located on Mount Fowlkes and Mount Locke in the Davis Mountains of West Texas...
team has set limits to the presence of one or more planets with masses between 0.13 and 2.5 Jupiter masses and average separations spanning between 0.05 and 5.2 AU.
External links
- Spectroscopic Properties of Cool Stars (SPOCS). I. 1040 F, G, and K Dwarfs from Keck, Lick, and AAT Planet Search Programs
- The Range of Masses and Periods Explored by Radial Velocity Searches for Planetary Companions
- An unseen companion to 36 Ursae Majoris A from analysis of plates taken with the Sproul 61-CM refractor
- A search for substellar companions to southern solar-type stars
- Detection Limits from the McDonald Observatory Planet Search Program