Kapteyn's Star
Encyclopedia
Kapteyn's Star is a class M1
red dwarf
star about 13 light years from Earth in the southern constellation
of Pictor
. With a magnitude
of nearly 9 it is visible through binoculars
or a telescope
.
, in 1898. While he was reviewing star charts and photographic plates he noted the star's very high proper motion
of more than 8 arc seconds per year. Later, the star became referred to as Kapteyn's Star, in honor of its discoverer. At that time, it had the highest proper motion of any star known, dethroning Groombridge 1830
. With the discovery of Barnard's Star
in 1916, Kapteyn's Star dropped to second place, where it remains. This star came within 2.15 pc of the Sun about 10,800 years ago.
star between one quarter and one third the size and mass of the Sun
and much cooler at about 3500°K, with some disagreement in the exact measurements between different observers. It is a variable star
identified as VZ Pictoris and is of the BY Draconis
variable type.
This star is distinctive in a number of other regards: it has a high radial velocity, orbits the Milky Way
retrograde
, and is the nearest known halo
star to the Sun.
Element abundances
indicate that Kapteyn's Star may originally have been part of Omega Centauri
, a globular cluster
that is thought to be the remnant of a dwarf galaxy
that merged with the Milky Way.
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...
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....
star about 13 light years from Earth in the southern 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 Pictor
Pictor
Pictor is a small and faint constellation in the southern sky , located between the brilliant star Canopus and the Large Magellanic Cloud. Its name is Latin for painter, but it is in fact an abbreviation of its original name Equuleus Pictoris, the 'painter's easel', and it is normally represented...
. With a magnitude
Apparent magnitude
The apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere...
of nearly 9 it is visible through binoculars
Binoculars
Binoculars, field glasses or binocular telescopes are a pair of identical or mirror-symmetrical telescopes mounted side-by-side and aligned to point accurately in the same direction, allowing the viewer to use both eyes when viewing distant objects...
or a telescope
Telescope
A telescope is an instrument that aids in the observation of remote objects by collecting electromagnetic radiation . The first known practical telescopes were invented in the Netherlands at the beginning of the 1600s , using glass lenses...
.
History
The star now known as Kapteyn's Star was originally cataloged by the Dutch astronomer, Jacobus KapteynJacobus Kapteyn
Jacobus Cornelius Kapteyn, was a Dutch astronomer, best known for his extensive studies of the Milky Way and as the first discoverer of evidence for galactic rotation....
, in 1898. While he was reviewing star charts and photographic plates he noted the star's very 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...
of more than 8 arc seconds per year. Later, the star became referred to as Kapteyn's Star, in honor of its discoverer. At that time, it had the highest proper motion of any star known, dethroning Groombridge 1830
Groombridge 1830
Groombridge 1830 is a star in the constellation Ursa Major.-Description:It is a yellowish class G8 subdwarf catalogued by Stephen Groombridge with the Groombridge Transit Circle between 1806 and the 1830s and published posthumously in his star catalog, Catalogue of Circumpolar Stars...
. With the discovery of Barnard's Star
Barnard's star
Barnard's Star, also known occasionally as Barnard's "Runaway" Star, is a very low-mass red dwarf star approximately six light-years away from Earth in the constellation of Ophiuchus . In 1916, the American astronomer E.E...
in 1916, Kapteyn's Star dropped to second place, where it remains. This star came within 2.15 pc of the Sun about 10,800 years ago.
Characteristics
Kapteyn's Star is a main sequenceMain 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 between one quarter and one third the size and mass of 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 much cooler at about 3500°K, with some disagreement in the exact measurements between different observers. It is a variable star
Variable star
A star is classified as variable if its apparent magnitude as seen from Earth changes over time, whether the changes are due to variations in the star's actual luminosity, or to variations in the amount of the star's light that is blocked from reaching Earth...
identified as VZ Pictoris and is of the BY Draconis
BY Draconis
BY Draconis is a multi-star system in the constellation Draco. It consists of at least three components. Components A and B form a close binary star system with a short orbital period of only 5.98 days. These may be pre-main sequence objects that are still in the process of collapsing. Their...
variable type.
This star is distinctive in a number of other regards: it has a high radial velocity, orbits the Milky Way
Milky Way
The Milky Way is the galaxy that contains the Solar System. This name derives from its appearance as a dim un-resolved "milky" glowing band arching across the night sky...
retrograde
Retrograde motion
Retrograde motion is motion in the direction opposite to the movement of something else, and is the contrary of direct or prograde motion. This motion can be the orbit of one body about another body or about some other point, or the rotation of a single body about its axis, or other phenomena such...
, and is the nearest known halo
Galactic halo
The term galactic halo is used to denote an extended, roughly spherical component of a galaxy, which extends beyond the main, visible component. It can refer to any of several distinct components which share these properties:* the galactic spheroid...
star to the Sun.
Element abundances
Abundance of the chemical elements
The abundance of a chemical element measures how relatively common the element is, or how much of the element is present in a given environment by comparison to all other elements...
indicate that Kapteyn's Star may originally have been part of Omega Centauri
Omega Centauri
Omega Centauri or NGC 5139 is a globular clusterin the constellation of Centaurus, discovered by Edmond Halley in 1677 who listed it as a nebula. Omega Centauri had been listed in Ptolemy's catalog 2000 years ago as a star. Lacaille included it in his catalog as number I.5...
, a globular cluster
Globular cluster
A globular cluster is a spherical collection of stars that orbits a galactic core as a satellite. Globular clusters are very tightly bound by gravity, which gives them their spherical shapes and relatively high stellar densities toward their centers. The name of this category of star cluster is...
that is thought to be the remnant of a dwarf galaxy
Dwarf galaxy
A dwarf galaxy is a small galaxy composed of up to several billion stars, a small number compared to our own Milky Way's 200-400 billion stars...
that merged with the Milky Way.
See also
- Kapteyn's Star in fiction
- List of nearest stars
- Stars named after peopleStars named after peopleOver the past few centuries, a small number of stars have been named after individual people. It is common in astronomy for objects to be given names, in accordance with accepted astronomical naming conventions...