double star
In observational astronomy, a double star or visual double is a pair of stars that appear close to each other as viewed from Earth, especially with the aid of optical telescopes.
This occurs because the pair either forms a binary star (i.e. a ...
consisting of a
yellow hypergiant
A yellow hypergiant (YHG) is a massive star with an extended atmosphere, a spectral class from A to K, and, starting with an initial mass of about 20–60 solar masses, has lost as much as half that mass. They are amongst the most visually lumino ...
primary (V810 Cen A) and blue giant secondary (V810 Cen B). It is a small amplitude
variable star
A variable star is a star whose brightness as seen from Earth (its apparent magnitude) changes systematically with time. This variation may be caused by a change in emitted light or by something partly blocking the light, so variable stars are ...
, entirely due to the supergiant primary which is visually over three magnitudes (about 12x) brighter than the secondary. It is the MK spectral standard for class G0 0-Ia. A 5th
magnitude
Magnitude may refer to:
Mathematics
*Euclidean vector, a quantity defined by both its magnitude and its direction
*Magnitude (mathematics), the relative size of an object
*Norm (mathematics), a term for the size or length of a vector
*Order of ...
star, it is visible to the
naked eye
Naked eye, also called bare eye or unaided eye, is the practice of engaging in visual perception unaided by a magnification, magnifying, Optical telescope#Light-gathering power, light-collecting optical instrument, such as a telescope or microsc ...
under good observing conditions.
Maurice Pim FitzGerald announced that the star's brightness varies, in 1973. It was given its
variable star designation
In astronomy, a variable-star designation is a unique identifier given to variable stars. It extends the Bayer designation format, with an identifying label (as described below) preceding the Latin genitive of the name of the constellation in whic ...
, V810 Centauri, in 1979.
V810 Cen A shows semi-regular variations with several component periods. The dominant mode is around 156 days and corresponds to
Cepheid
A Cepheid variable () is a type of variable star that pulsates radially, varying in both diameter and temperature. It changes in brightness, with a well-defined stable period (typically 1–100 days) and amplitude. Cepheids are important cosmi ...
fundamental mode
A normal mode of a dynamical system is a pattern of motion in which all parts of the system move sinusoidally with the same frequency and with a fixed phase relation. The free motion described by the normal modes takes place at fixed frequencies. ...
radial pulsation. Without the other
stellar pulsation
Stellar pulsations are caused by expansions and contractions in the outer layers as a star seeks to maintain equilibrium. These fluctuations in stellar radius cause corresponding changes in the luminosity of the star. Astronomers are able to ded ...
modes it would be considered a
Classical Cepheid variable
Classical Cepheids are a type of Cepheid variable star. They are young, population I variable stars that exhibit regular radial pulsations with periods of a few days to a few weeks and visual amplitudes ranging from a few tenths of a magnitude u ...
. Other pulsation modes have been detected at 89 to 234 days, with the strongest being a possible non-radial p-mode at 107 days and a possible non-radial g-mode at 185 days.
The blue giant secondary has a similar mass and luminosity to the supergiant primary, but is visually much fainter. The primary is expected to have lost around since it was on the
main sequence
In astronomy, the main sequence is a classification of stars which appear on plots of stellar color index, color versus absolute magnitude, brightness as a continuous and distinctive band. Stars on this band are known as main-sequence stars or d ...
, and has expanded and cooled so it lies at the blue edge of the Cepheid
instability strip
The unqualified term instability strip usually refers to a region of the Hertzsprung–Russell diagram largely occupied by several related classes of pulsating variable stars: Delta Scuti variables, SX Phoenicis variables, and rapidly oscillat ...
. It is expected to get no cooler and may perform a
blue loop
In the field of stellar evolution, a blue loop is a stage in the life of an evolved star where it changes from a cool star to a hotter one before cooling again. The name derives from the shape of the evolutionary track on a Hertzsprung–Russel ...
while slowly increasing in luminosity.
V810 Cen was once thought to be a member of the Stock 14
open cluster
An open cluster is a type of star cluster made of tens to a few thousand stars that were formed from the same giant molecular cloud and have roughly the same age. More than 1,100 open clusters have been discovered within the Milky Way galaxy, and ...
at 2.6 kpc, but appears to be more distant (3.2-3.5 kpc) based on spectrophotometric study. The distance derived from
Gaia
In Greek mythology, Gaia (; , a poetic form of ('), meaning 'land' or 'earth'),, , . also spelled Gaea (), is the personification of Earth. Gaia is the ancestral mother—sometimes parthenogenic—of all life. She is the mother of Uranus (S ...
parallax
Parallax is a displacement or difference in the apparent position of an object viewed along two different sightline, lines of sight and is measured by the angle or half-angle of inclination between those two lines. Due to perspective (graphica ...
measurements is even larger, between 4 kpc and 16 kpc.
4511
The 4000 series is a CMOS logic family of integrated circuits (ICs) first introduced in 1968 by RCA. It was slowly migrated into the 4000B buffered series after about 1975. It had a much wider supply voltage range than any contemporary logic fami ...