Upsilon Aquarii
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Upsilon Aquarii, Latinized from υ Aquarii, is the
Bayer designation A Bayer designation is a stellar designation in which a specific star is identified by a Greek or Latin letter followed by the genitive form of its parent constellation's Latin name. The original list of Bayer designations contained 1,564 stars. ...
for a
binary star A binary star 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 using a telescope as separate stars, in wh ...
system in the
equatorial Equatorial may refer to something related to: *Earth's equator **the tropics, the Earth's equatorial region **tropical climate *the Celestial equator ** equatorial orbit **equatorial coordinate system ** equatorial mount, of telescopes * equatorial ...
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
Aquarius Aquarius may refer to: Astrology * Aquarius (astrology), an astrological sign * Age of Aquarius, a time period in the cycle of astrological ages Astronomy * Aquarius (constellation) * Aquarius in Chinese astronomy Arts and entertainment ...
. It is visible to the naked eye as a faint star with an apparent visual magnitude of 5.21.
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 ...
measurements give a distance estimate of 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 ...
. This is a high proper-motion star that is drifting closer to the Sun 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 –2.3 km/s. It is part of the Hercules-Lyra association. The primary component is an F-type main sequence star with a
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 F7 V. It is less than a billion years old and is spinning with a
projected rotational velocity Stellar rotation is the angular motion of a star about its axis. The rate of rotation can be measured from the spectrum of the star, or by timing the movements of active features on the surface. The rotation of a star produces an equatorial bulge ...
of 35 km/s. The star has 1.4 times the
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 1.5 times the Sun's radius. It is radiating 3.6 times the Sun's luminosity 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 6,597 K, giving it the yellow-white hue of an F-type star. The star displays an
excess Excess may refer to: * Angle excess, in spherical trigonometry * Insurance excess, similar to a deductible * Excess, in chemistry, a reagent that is not the limiting reagent * "Excess", a song by Tricky from the album '' Blowback'' * ''Excess'' ( ...
of near infrared radiation, suggesting it has a
circumstellar disk A circumstellar disc (or circumstellar disk) is a torus, pancake or ring-shaped accretion disk of matter composed of gas, dust, planetesimals, asteroids, or collision fragments in orbit around a star. Around the youngest stars, they are the rese ...
of dusty debris. This disk has a mean temperature of and is orbiting at an estimated radius of . A faint stellar companion was detected in 2007 at the Gemini Observatory, with a separation of from the primary. This is equivalent to a physical projected separation of , which yields an estimated
orbital period The orbital period (also revolution period) is the amount of time a given astronomical object takes to complete one orbit around another object. In astronomy, it usually applies to planets or asteroids orbiting the Sun, moons orbiting planets ...
of ~. The debris disk is orbiting close to the dynamically unstable region of this system.


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Image Upsilon Aquarii
{{DEFAULTSORT:Upsilon Aquarii F-type main-sequence stars Circumstellar disks Binary stars Aquarius (constellation) Aquarii, Upsilon BD-21 6251 Aquarii, 059 0863.2 213845 111449 8592