GY Andromedae (GY And) is an α² Canum Venaticorum type

binary Binary may refer to: Science and technology Mathematics * Binary number, a representation of numbers using only two values (0 and 1) for each digit * Binary function, a function that takes two arguments * Binary operation, a mathematical op ...

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 ...

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 first constellati ...

Andromeda. Its brightness fluctuates in

visual magnitude Apparent magnitude () is a measure of the brightness of a star, astronomical object or other celestial objects like artificial satellites. Its value depends on its intrinsic luminosity, its distance, and any extinction of the object's light ca ...

between 6.27^m and 6.41^m, making it a challenge to view with the naked eye even in good seeing conditions. The

magnetic activity A stellar magnetic field is a magnetic field generated by the motion of conductive Plasma (physics), plasma inside a star. This motion is created through convection, which is a form of energy transport involving the physical movement of material ...

on this star shows an unusually long period of variability, cycling about once every 23 years. Based upon

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, this star is located at a distance of about from the

Earth Earth is the third planet from the Sun and the only astronomical object known to Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...

. This is

classified Classified may refer to: General *Classified information, material that a government body deems to be sensitive *Classified advertising or "classifieds" Music *Classified (rapper) (born 1977), Canadian rapper * The Classified, a 1980s American ro ...

as an Ap/Bp star, with a peculiar spectrum showing lines of

chromium Chromium is a chemical element; it has Symbol (chemistry), symbol Cr and atomic number 24. It is the first element in Group 6 element, group 6. It is a steely-grey, Luster (mineralogy), lustrous, hard, and brittle transition metal. Chromium ...

and

europium Europium is a chemical element; it has symbol Eu and atomic number 63. It is a silvery-white metal of the lanthanide series that reacts readily with air to form a dark oxide coating. Europium is the most chemically reactive, least dense, and soft ...

that change in intensity over a period matching the variability cycle, although opposite in

phase Phase or phases may refer to: Science *State of matter, or phase, one of the distinct forms in which matter can exist *Phase (matter), a region of space throughout which all physical properties are essentially uniform *Phase space, a mathematica ...

. Its most striking characteristic is the presence of the unstable element

promethium Promethium is a chemical element; it has Symbol (chemistry), symbol Pm and atomic number 61. All of its isotopes are Radioactive decay, radioactive; it is extremely rare, with only about 500–600 grams naturally occurring in the Earth's crust a ...

in its

emission spectrum The emission spectrum of a chemical element or chemical compound is the Spectrum (physical sciences), spectrum of frequencies of electromagnetic radiation emitted due to electrons making a atomic electron transition, transition from a high energ ...

. All isotopes of this element are

radioactive Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is conside ...

with

half lives Half-life is a mathematical and scientific description of exponential or gradual decay. Half-life, half life or halflife may also refer to: Film * ''Half-Life'' (film), a 2008 independent film by Jennifer Phang * '' Half Life: A Parable for t ...

of 17.7 years or less. The promethium in the outer envelope may be generated by the spontaneous

fission Fission, a splitting of something into two or more parts, may refer to: * Fission (biology), the division of a single entity into two or more parts and the regeneration of those parts into separate entities resembling the original * Nuclear fissio ...

of higher mass

transuranic element The transuranium (or transuranic) elements are the chemical elements with atomic number greater than 92, which is the atomic number of uranium. All of them are radioactively unstable and decay into other elements. Except for neptunium and pluton ...

System

Based on

radial velocity The radial velocity or line-of-sight velocity of a target with respect to an observer is the rate of change of the vector displacement between the two points. It is formulated as the vector projection of the target-observer relative velocity ...

measurements taken at the

Dominion Astrophysical Observatory The Dominion Astrophysical Observatory, located on Observatory Hill (Saanich), Observatory Hill, in Saanich, British Columbia, was completed in 1918 by the Canadian Government, Canadian government. The Dominion architect responsible for the bui ...

between 1927 and 1935 Canadian astronomer

William Edmund Harper William Edmund Harper, March 20, 1878 – June 14, 1940, (age 62) was a Canadian astronomer. William Harper was born in Dobbington, Ontario. He attended high school in Owen Sound, then taught for three years following his graduation. When he had ...

strongly suspected that this star was a

spectroscopic binary A binary star or binary star system is a system of two stars that are gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved as separate stars us ...

. In 1958, American astronomer

Horace W. Babcock Horace Welcome Babcock (September 13, 1912 – August 29, 2003) was an American astronomer. He was the son of Harold D. Babcock. Career Babcock invented and built several astronomical instruments and was the first to propose adaptive optic ...

confirmed the binary nature of the star. It has an orbital period of 273 days with a large

eccentricity Eccentricity or eccentric may refer to: * Eccentricity (behavior), odd behavior on the part of a person, as opposed to being "normal" Mathematics, science and technology Mathematics * Off-Centre (geometry), center, in geometry * Eccentricity (g ...

of 0.47. The two components are separated by an estimated distance of at least , or 0.25

Astronomical Unit The astronomical unit (symbol: au or AU) is a unit of length defined to be exactly equal to . Historically, the astronomical unit was conceived as the average Earth-Sun distance (the average of Earth's aphelion and perihelion), before its m ...

References

External links

* Astronomie: Die Sterne - Special Stars
GY Andromedae
{{DEFAULTSORT:Gy Andromedae Andromeda (constellation) Alpha2 Canum Venaticorum variables B-type main-sequence stars Spectroscopic binaries 0465 007651 009996 Andromedae, GY Durchmusterung objects