Groombridge 1618
Encyclopedia
Groombridge 1618 is a star
in the constellation
Ursa Major
. It is located close to Earth
, at a distance of less than 16 light years. This is an orange dwarf
star of spectral type K5 V.
in 1838. It has a high proper motion
across the sky, which is normally taken as an indicator that the star is located nearby—making it an early candidate for parallax
measurement of its distance. In 1884 the parallax angle was measured as , which is larger than the modern value of 0″.205.
Groombridge 1618 has a stellar classification
of K5 V, which means it is a K-type main sequence star that is generating energy by fusing hydrogen at its core. It has 67% of the mass of the Sun
, 61% of the Sun's radius, but radiates only 4.6% of the Sun's energy. The effective surface temperature of the star's photosphere
is about 4,000 K, giving it an orange hue.
It is a flare star
with behavior similar to UV Ceti, causing it to randomly undergo increases in luminosity. The chromosphere
has been shown to be active and possesses star spots comparable to Sun spot
s. It has a greater luminosity than most flare stars, which are typically red dwarfs, but is less active. The level of activity suggests that this is a somewhat youthful star.
came up
negative, implying that Groombridge 1618 does not possess
a debris disk
(such as Vega
). If this star does have a companion, astrometric
measurements appear to place an upper bound of 3–12 times the mass of Jupiter on such a hypothetical object (for orbital periods in the range of 5–50 years).
According to Marcy & Benitz (1989), a possible periodicity of 122 day
s has been detected, inferring the potential presence of a massive planetary object with minimum mass 4 times that of Jupiter
. This candidate planet has not been confirmed and the signal the authors had found could have been due to intrinsic stellar activity from the star's young age.
If confirmed, the planet would be located at the outer edge of the star's habitable zone
.
An examination of this system in 2010 using the MMT
telescope fitted with adaptive optics
failed to detect a planetary companion.
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...
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....
Ursa Major
Ursa Major
Ursa Major , also known as the Great Bear, is a constellation visible throughout the year in most of the northern hemisphere. It can best be seen in April...
. It is located close to Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
, at a distance of less than 16 light years. This is an orange dwarf
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 of spectral type K5 V.
Properties
This star was first identified as entry number 1618 in the work A Catalog of Circumpolar Stars, published posthumously by Stephen GroombridgeStephen Groombridge
Stephen Groombridge FRS was a British astronomer.In 1806, using a then new transit circle built by Edward Troughton, he began compiling a star catalogue of stars down to about eighth or ninth magnitude...
in 1838. It has a high proper motion
Proper 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...
across the sky, which is normally taken as an indicator that the star is located nearby—making it an early candidate for parallax
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. The term is derived from the Greek παράλλαξις , meaning "alteration"...
measurement of its distance. In 1884 the parallax angle was measured as , which is larger than the modern value of 0″.205.
Groombridge 1618 has a stellar classification
Stellar classification
In astronomy, stellar classification is a classification of stars based on their spectral characteristics. The spectral class of a star is a designated class of a star describing the ionization of its chromosphere, what atomic excitations are most prominent in the light, giving an objective measure...
of K5 V, which means it is a K-type main sequence star that is generating energy by fusing hydrogen at its core. It has 67% of the mass of the Sun
Solar mass
The solar mass , , is a standard unit of mass in astronomy, used to indicate the masses of other stars and galaxies...
, 61% of the Sun's radius, but radiates only 4.6% of the Sun's energy. The effective surface temperature of the star's photosphere
Photosphere
The photosphere of an astronomical object is the region from which externally received light originates. The term itself is derived from Ancient Greek roots, φῶς, φωτός/phos, photos meaning "light" and σφαῖρα/sphaira meaning "sphere", in reference to the fact that it is a spheric surface perceived...
is about 4,000 K, giving it an orange hue.
It is a flare star
Flare star
A flare star is a variable star that can undergo unpredictable dramatic increases in brightness for a few minutes. It is believed that the flares on flare stars are analogous to solar flares in that they are due to magnetic reconnection in the atmospheres of the stars. The brightness increase is...
with behavior similar to UV Ceti, causing it to randomly undergo increases in luminosity. The chromosphere
Chromosphere
The chromosphere is a thin layer of the Sun's atmosphere just above the photosphere, roughly 2,000 kilometers deep....
has been shown to be active and possesses star spots comparable to Sun spot
Sun SPOT
Sun SPOT is a wireless sensor network mote developed by Sun Microsystems. The device is built upon the IEEE 802.15.4 standard...
s. It has a greater luminosity than most flare stars, which are typically red dwarfs, but is less active. The level of activity suggests that this is a somewhat youthful star.
System
A search for an excess amount of infrared emission from this star by the Infrared Space ObservatoryInfrared Space Observatory
The Infrared Space Observatory was a space telescope for infrared light designed and operated by the European Space Agency , in cooperation with ISAS and NASA...
came up
negative, implying that Groombridge 1618 does not possess
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...
(such as Vega
Vega
Vega is the brightest star in the constellation Lyra, the fifth brightest star in the night sky and the second brightest star in the northern celestial hemisphere, after Arcturus...
). If this star does have a companion, astrometric
Astrometry
Astrometry is the branch of astronomy that involves precise measurements of the positions and movements of stars and other celestial bodies. The information obtained by astrometric measurements provides information on the kinematics and physical origin of our Solar System and our Galaxy, the Milky...
measurements appear to place an upper bound of 3–12 times the mass of Jupiter on such a hypothetical object (for orbital periods in the range of 5–50 years).
According to Marcy & Benitz (1989), a possible periodicity of 122 day
Day
A day is a unit of time, commonly defined as an interval equal to 24 hours. It also can mean that portion of the full day during which a location is illuminated by the light of the sun...
s has been detected, inferring the potential presence of a massive planetary object with minimum mass 4 times 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,...
. This candidate planet has not been confirmed and the signal the authors had found could have been due to intrinsic stellar activity from the star's young age.
If confirmed, the planet would be located at the outer edge of the star's habitable zone
Habitable zone
In astronomy and astrobiology, a habitable zone is an umbrella term for regions that are considered favourable to life. The concept is inferred from the empirical study of conditions favourable for Life on Earth...
.
An examination of this system in 2010 using the MMT
MMT Observatory
The MMT Observatory is an astronomical observatory on the site of Fred Lawrence Whipple Observatory . The Whipple observatory complex is located on Mount Hopkins, Arizona, USA in the Santa Rita Mountains...
telescope fitted with adaptive optics
Adaptive optics
Adaptive optics is a technology used to improve the performance of optical systems by reducing the effect of wavefront distortions. It is used in astronomical telescopes and laser communication systems to remove the effects of atmospheric distortion, and in retinal imaging systems to reduce the...
failed to detect a planetary companion.
See also
- Stephen GroombridgeStephen GroombridgeStephen Groombridge FRS was a British astronomer.In 1806, using a then new transit circle built by Edward Troughton, he began compiling a star catalogue of stars down to about eighth or ninth magnitude...
- List of nearest stars
- Groombridge 1618 in fiction