HD 128311 is a
variable star
A variable star is a star whose brightness as seen from Earth (its apparent magnitude) changes with time. This variation may be caused by a change in emitted light or by something partly blocking the light, so variable stars are classified as ...
in the northern
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
Boötes
Boötes ( ) is a constellation in the northern sky, located between 0° and +60° declination, and 13 and 16 hours of right ascension on the celestial sphere. The name comes from la, Boōtēs, which comes from grc-gre, Βοώτης, Boṓtēs ...
. It has the
variable star designation
In astronomy, a variable star designation is a unique identifier given to variable stars. It uses a variation on the Bayer designation format, with an identifying label (as described below) preceding the Latin genitive of the name of the constell ...
HN Boötis, while HD 128311 is the star's designation in the ''
Henry Draper Catalogue''. The star is invisible to the naked eye with an
apparent visual magnitude that fluctuates around 7.48.
[ It is located at a distance of 53 ]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 the Sun based on 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 ...
, but is drifting closer 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 −9.6 km/s.[ Two confirmed extrasolar planets have been detected in orbit around this star.]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 HN Boo is K3V,[ which indicates this is a ]K-type main sequence star
A K-type main-sequence star, also referred to as a K-type dwarf or an orange dwarf, is a main-sequence (hydrogen-burning) star of spectral type K and luminosity class V. These stars are intermediate in size between red M-type main-sequence stars ...
. It is a BY Draconis-type variable, randomly varying in brightness by 0.04 in magnitude over a period of 11.54 days[ due to star spots and high ]chromospheric activity
A chromosphere ("sphere of color") is the second layer of a star's atmosphere, located above the photosphere and below the solar transition region and corona. The term usually refers to the Sun's chromosphere, but not exclusively.
In the S ...
. The star exhibits strong emission, which suggests an age of 0.5–1.0 billion years.mass of the Sun
The solar mass () is a standard unit of mass in astronomy, equal to approximately . It is often used to indicate the masses of other stars, as well as stellar clusters, nebulae, galaxies and black holes. It is approximately equal to the mass ...
and 78% of the Sun's radius. The 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 ...
of the star, meaning its abundance of heavier elements, appears slightly higher than in the Sun. It is radiating 31% of the luminosity of the Sun 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 4,863 K.[
]
Planetary system
In 2002, the discovery of the 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 ...
HD 128311 b
HD 128311 b is an exoplanet located approximately 54 light-years away in the constellation of Boötes. This planet orbits in an eccentric orbit about 1.084 AU from its star (HD 128311
HD 128311 is a variable star in the northern conste ...
was announced by Paul Butler.HD 128311 c
HD 128311 c is an exoplanet located approximately 54 light-years away in the constellation of Boötes. This planet orbits in an eccentric orbit at 1.74 AU from its star (HD 128311). The planet has a minimum mass of 3.22 , and astrometric
Astrom ...
was announced by Steve Vogt
''yes'Steve is a masculine given name, usually a short form (hypocorism) of Steven or Stephen
Notable people with the name include:
steve jops
* Steve Abbott (disambiguation), several people
* Steve Adams (disambiguation), several people
* Steve ...
.astrometry
Astrometry is a branch of astronomy that involves precise measurements of the positions and movements of stars and other celestial bodies. It provides the kinematics and physical origin of the Solar System and this galaxy, the Milky Way.
His ...
. The same study also proposed a third planetary candidate, but it has not been confirmed.
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
*
External links
GJ 3860
Extrasolar Planet Interactions
by Rory Barnes & Richard Greenberg, Lunar and Planetary Lab, University of Arizona
Image HD 128311
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{{Sky, 14, 36, 00.5607, +, 09, 44, 47.466, 54.14
K-type main-sequence stars
BY Draconis variables
Planetary systems with two confirmed planets
Boötes
Durchmusterung objects
Gliese and GJ objects
128311
071395
Boötis, HN