HD 38529
Encyclopedia
HD 38529 is a binary star
approximately 128 light-year
s away in the constellation
of Orion
.
, which has also been classified as a main sequence
dwarf
of spectral type G4V. It is about 40% more massive than our Sun
. Two substellar companions are known in orbit around this star, including one with a mass above the deuterium fusion limit that is often used as the dividing line between giant planets and brown dwarf
s. There is a debris disk
located at least 86 astronomical unit
s from the star.
who used Doppler spectroscopy
. It has mass 78% that of Jupiter
and orbits very close to the star, just beyond the distance limit for hot Jupiter
s. One year later, a massive superjovian HD 38529 c was found orbiting at 3.68 AU
with a minimum mass
of 12.7 Jupiter mass
es. Astrometric measurements from the Hipparcos
satellite gave a best fit inclination of 160° and a true mass
37 times that of Jupiter, turning this planet into a brown dwarf
. Further study of the system using Hubble Space Telescope
astrometry revised the mass of HD 38529 c downwards to 17.7 Jupiter masses and suggested the presence of an additional planet, orbiting in the gap between HD 38529 b and c.
stellar companion to HD 38529 A at a projected distance of about 12042 AU
. The star is a red dwarf
of spectral type M3.0V.
Binary star
A binary star is a star system consisting of two stars orbiting around their common center of mass. The brighter star is called the primary and the other is its companion star, comes, or secondary...
approximately 128 light-year
Light-year
A light-year, also light year or lightyear is a unit of length, equal to just under 10 trillion kilometres...
s away in the constellation
Constellation
In modern astronomy, a constellation is an internationally defined area of the celestial sphere. These areas are grouped around asterisms, patterns formed by prominent stars within apparent proximity to one another on Earth's night sky....
of Orion
Orion (constellation)
Orion, often referred to as The Hunter, is a prominent constellation located on the celestial equator and visible throughout the world. It is one of the most conspicuous, and most recognizable constellations in the night sky...
.
HD 38529 A
HD 38529 A is a yellow subgiant starStar
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...
, which has also been classified as a main sequence
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...
dwarf
Dwarf star
The term dwarf star refers to a variety of distinct classes of stars.* Dwarf star alone generally refers to any main sequence star, a star of luminosity class V.** Red dwarfs are low-mass main sequence stars....
of spectral type G4V. It is about 40% more massive than our 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...
. Two substellar companions are known in orbit around this star, including one with a mass above the deuterium fusion limit that is often used as the dividing line between giant planets and 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...
s. There is a debris disk
Debris disk
A debris disk is a circumstellar disk of dust and debris in orbit around a star. Sometimes these disks contain prominent rings, as seen in the image of Fomalhaut on the right. Debris disks have been found around both evolved and young stars, as well as at least one debris disk in orbit around a...
located at least 86 astronomical unit
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
s from the star.
Planetary system
In 2002, the planet HD 38529 b was discovered orbiting the star HD 38529 A by Debra FischerDebra Fischer
Debra A. Fischer is a professor of astronomy at Yale University. Fischer has co-authored over 100 papers on dwarf and sub-stellar mass objects in the galactic neighborhood, including many on extrasolar planets. She is a principal investigator with the N2K Consortium searching for exoplanets...
who used Doppler spectroscopy
Doppler spectroscopy
Doppler spectroscopy, also known as radial velocity measurement, is a spectroscopic method for finding extrasolar planets. It involves the observation of Doppler shifts in the spectrum of the star around which the planet orbits....
. It has mass 78% that 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,...
and orbits very close to the star, just beyond the distance limit for hot Jupiter
Hot Jupiter
Hot Jupiters are a class of extrasolar planet whose mass is close to or exceeds that of Jupiter...
s. One year later, a massive superjovian HD 38529 c was found orbiting at 3.68 AU
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
with a minimum mass
Minimum mass
In astronomy, minimum mass is the lower-bound calculated mass of observed objects such as planets, stars and binary systems, nebulae, and black holes. Minimum mass is a widely cited statistic for extrasolar planets...
of 12.7 Jupiter mass
Jupiter mass
Jupiter mass , is the unit of mass equal to the total mass of the planet Jupiter . Jupiter mass is used to describe masses of the gas giants, such as the outer planets and extrasolar planets. It is also used in describing brown dwarfs....
es. Astrometric measurements from the Hipparcos
Hipparcos
Hipparcos was a scientific mission of the European Space Agency , launched in 1989 and operated between 1989 and 1993. It was the first space experiment devoted to precision astrometry, the accurate measurement of the positions of celestial objects on the sky...
satellite gave a best fit inclination of 160° and a true mass
True mass
The term true mass is synonymous with the term mass, but is used in astronomy to differentiate the measured mass of a planet from the lower limit of mass usually obtained from radial velocity techniques...
37 times that of Jupiter, turning this planet into 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...
. Further study of the system using Hubble Space Telescope
Hubble Space Telescope
The Hubble Space Telescope is a space telescope that was carried into orbit by a Space Shuttle in 1990 and remains in operation. A 2.4 meter aperture telescope in low Earth orbit, Hubble's four main instruments observe in the near ultraviolet, visible, and near infrared...
astrometry revised the mass of HD 38529 c downwards to 17.7 Jupiter masses and suggested the presence of an additional planet, orbiting in the gap between HD 38529 b and c.
HD 38529 B
HD 38529 B is a common proper motionProper motion
The proper motion of a star is its angular change in position over time as seen from the center of mass of the solar system. It is measured in seconds of arc per year, arcsec/yr, where 3600 arcseconds equal one degree. This contrasts with radial velocity, which is the time rate of change in...
stellar companion to HD 38529 A at a projected distance of about 12042 AU
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
. The star is a red dwarf
Red dwarf
According to the Hertzsprung-Russell diagram, a red dwarf star is a small and relatively cool star, of the main sequence, either late K or M spectral type....
of spectral type M3.0V.