Delta² Lyrae (δ² Lyr) is a 4th magnitude star in the constellation

Lyra Lyra (; Latin for lyre, from Greek ''λύρα'') is a small constellation. It is one of the 48 listed by the 2nd century astronomer Ptolemy, and is one of the modern 88 constellations recognized by the International Astronomical Union. Lyra was ...

, approximately 900

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 away from

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...

. It is one of the M4II spectral standard stars, meaning it is a

bright giant A giant star is a star with substantially larger radius and luminosity than a main-sequence (or ''dwarf'') star of the same surface temperature.Giant star, entry in ''Astronomy Encyclopedia'', ed. Patrick Moore, New York: Oxford University Press ...

star with a surface temperature around 3,600

kelvins The kelvin, symbol K, is the primary unit of temperature in the International System of Units (SI), used alongside its prefixed forms and the degree Celsius. It is named after the Belfast-born and University of Glasgow-based engineer and phys ...

. It puts out more energy than 10,000 suns, although more than 90% of it at longer than visual wavelengths. Direct angular measurements, combined with the Hipparcos parallax, give a radius of 1.1 - 1.3

astronomical unit The astronomical unit (symbol: au, or or AU) is a unit of length, roughly the distance from Earth to the Sun and approximately equal to or 8.3 light-minutes. The actual distance from Earth to the Sun varies by about 3% as Earth orbits t ...

s, comparable to the size calculated from other observed data. It began life as a hot blue main sequence star, but now is a large cool

asymptotic giant branch The asymptotic giant branch (AGB) is a region of the Hertzsprung–Russell diagram populated by evolved cool luminous stars. This is a period of stellar evolution undertaken by all low- to intermediate-mass stars (about 0.5 to 8 solar masses) lat ...

star with a

degenerate Degeneracy, degenerate, or degeneration may refer to: Arts and entertainment * Degenerate (album), ''Degenerate'' (album), a 2010 album by the British band Trigger the Bloodshed * Degenerate art, a term adopted in the 1920s by the Nazi Party i ...

carbon-oxygen core. It is a semi-regular

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 ...

that has its brightness change by 0.2 magnitudes over an ill-defined period. Delta² Lyrae was once thought to form a

visual binary A visual binary is a gravitationally bound binary star system that can be resolved into two stars. These stars are estimated, via Kepler's third law, to have periods ranging from a few years to thousands of years. A visual binary consists of two st ...

with the star Delta¹ Lyrae, but it does not, only appearing to do so if seen from earth's direction. δ² Lyrae is a

, probably a

semiregular variable In astronomy, a semiregular variable star, a type of variable star, is a giant or supergiant of intermediate and late (cooler) spectral type showing considerable periodicity in its light changes, accompanied or sometimes interrupted by various irre ...

. It has a magnitude range of 4.22 to 4.33. It is the brightest member of the scattered

open cluster An open cluster is a type of star cluster made of up 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 ...

Stephenson 1, also known as the δ Lyrae Cluster. Other known members include δ¹ Lyrae, a handful of 8th-9th magnitudes stars, and at least thirty other stars down to 14th magnitude. Multiple star catalogues list several companions to δ² Lyrae, with designations such as

ADS" \n\nads.txt (Authorized Digital Sellers) is an initiative from IAB Technology Laboratory. It specifies a text file that companies can host on their web servers, listing the other companies authorized to sell their products or services. This is des ...

11825. Two of them are a close pair of 10th magnitude stars about 87" from δ², designated components B and C. The spectral type of the pair suggests that they are at the same distance as Delta² Lyrae, which could mean that the three stars form a

triple Triple is used in several contexts to mean "threefold" or a " treble": Sports * Triple (baseball), a three-base hit * A basketball three-point field goal * A figure skating jump with three rotations * In bowling terms, three strikes in a row * ...

star system. In this case, the ADS 11825BC pair would be 24,000 AU away from δ² Lyrae, and it would take 24,000 years for it to make an orbit. The two stars in the BC system take at least 10,500 years to make an orbit and are separated by 600AU.

References

{{Stars of Lyra Lyra (constellation) Lyrae, Delta Lyrae, 12 7139 175588 BD+36 3319 092791 M-type bright giants Asymptotic-giant-branch stars Semiregular variable stars