HD 108874 is a
yellow dwarf star (
spectral type G5 V) in the
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 ...
of
Coma Berenices
Coma Berenices is an ancient asterism in the northern sky, which has been defined as one of the 88 modern constellations. It is in the direction of the fourth galactic quadrant, between Leo and Boötes, and it is visible in both hemisphere ...
. It is 195
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 Earth
and has two
extrasolar planets that are possibly in a 9:2
orbital resonance.
Star
HD 108874 is probably billions of years older than the
Sun however the age is not well constrained. The star has a temperature of about 5600 K. Its
metallicity
In astronomy, metallicity is the abundance of elements present in an object that are heavier than hydrogen and helium. Most of the normal physical matter in the Universe is either hydrogen or helium, and astronomers use the word ''"metals"'' as a ...
is 1.18 times that of the Sun, meaning it has greater
iron
Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in f ...
abundance relative to
hydrogen
Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic, an ...
and
helium
Helium (from el, ἥλιος, helios, lit=sun) is a chemical element with the symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas and the first in the noble gas group in the periodic table. ...
. It has about the same mass as the Sun, but the radius is probably greater.
Planetary system
In 2003, the
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 ...
HD 108874 b was discovered by the US-based team led by
Paul Butler,
Geoffrey Marcy
Geoffrey William Marcy (born September 29, 1954) is an American astronomer. He was an early influence in the field of exoplanet detection, discovery, and characterization. Marcy was a professor of astronomy at the University of California, Berk ...
,
Steven Vogt
Steven Scott Vogt (born December 20, 1949) is an American astronomer of German descent whose main interest is the search for extrasolar planets.
He is credited, along with R. Paul Butler, for discovering Gliese 581 g, the first potentially ha ...
, and
Debra Fischer. A total of 20 radial velocity observations, obtained at the
W. M. Keck Observatory
The W. M. Keck Observatory is an astronomical observatory with two telescopes at an elevation of 4,145 meters (13,600 ft) near the summit of Mauna Kea in the U.S. state of Hawaii. Both telescopes have aperture primary mirrors, and when comp ...
between 1999 and 2002, were used to make the discovery.
In 2005, further observations revealed this star has another jovian planet orbiting further out, designated as
HD 108874 c.
The orbital parameters of both planets were updated in 2009 with additional observations.
Those two planets are near, and possibly in a 9:2 orbital resonance. This means if HD 108874 b orbits the star nine times, then HD 108874 c orbits twice, because the
orbital period
The orbital period (also revolution period) is the amount of time a given astronomical object takes to complete one orbit around another object. In astronomy, it usually applies to planets or asteroids orbiting the Sun, moons orbiting planets ...
for planet c is four and a half times longer than planet b.
There is an additional
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 ...
signal in the data at a period of 40 days however this likely caused by the
stellar rotation
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 ...
period.
See also
*
List of extrasolar planets
These are lists of exoplanets. Most of these were discovered by the Kepler space telescope. There are an additional 2,054 potential exoplanets from Kepler's first mission yet to be confirmed, as well as 978 from its " Second Light" mission and ...
References
External links
Extrasolar Planet Interactionsby Rory Barnes & Richard Greenberg, Lunar and Planetary Lab, University of Arizona
{{DEFAULTSORT:HD 108874
Coma Berenices
108874
061028
Planetary systems with two confirmed planets
G-type main-sequence stars
Durchmusterung objects