R Scuti
Encyclopedia
R Scuti is a star in the constellation
of Scutum
. It is a yellow supergiant
and is a pulsating variable known as a RV Tauri variable
.
It was discovered in 1795 by Edward Pigott at a time when only a few variable star
s were known to exist. R Sct is the brightest of the RV Tau-type stars and the American Association of Variable Star Observers
(AAVSO) contains over 110,000 observations of this star. At its brightest it is visible to the naked eye
, and at its dimmest can be located with good binocular
s. In the sky it is about 1 degree northwest of the Wild Duck Cluster
(Messier 11).
gives a parallax
of 2.32 milli-arcseconds for R Sct, giving it an estimated distance of 431 pc. But a period–luminosity relation similar to what is used for Cepheid variables suggests that R Sct is at a distance of 750 pc with a luminosity
of around 9400 Sun
s. But this would make R Sct twice as luminous as the next most luminous RV Tau-type star in the study. The author of the period–luminosity study doubts the high luminosity and resulting distance, and it has been argued (Matsuura2002) that R Sct is a thermal-pulsing AGB star, observed in a helium-burning phase instead of a post-AGB star.
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 Scutum
Scutum
Scutum is a small constellation introduced in the seventeenth century. Its name is Latin for shield.-History:Scutum is the only constellation that owes its name to a non-classical historical figure...
. It is a yellow supergiant
Supergiant
Supergiants are among the most massive stars. They occupy the top region of the Hertzsprung-Russell diagram. In the Yerkes spectral classification, supergiants are class Ia or Ib . They typically have bolometric absolute magnitudes between -5 and -12...
and is a pulsating variable known as a RV Tauri variable
RV Tauri variable
RV Tauri variables are supergiant variable stars. They exhibit changes in luminosity which are tied to radial pulsations of their surfaces. Their changes in brightness are also correlated with changes in their spectral type. While at their brightest, the stars have spectral types F or G. At...
.
It was discovered in 1795 by Edward Pigott at a time when only a few 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...
s were known to exist. R Sct is the brightest of the RV Tau-type stars and the American Association of Variable Star Observers
American Association of Variable Star Observers
Since its founding in 1911, the American Association of Variable Star Observers has coordinated, collected, evaluated, analyzed, published, and archived variable star observations made largely by amateur astronomers and makes the records available to professional astronomers, researchers, and...
(AAVSO) contains over 110,000 observations of this star. At its brightest it is visible to the naked eye
Naked eye
The naked eye is a figure of speech referring to human visual perception unaided by a magnifying or light-collecting optical device, such as a telescope or microscope. Vision corrected to normal acuity using corrective lenses is considered "naked"...
, and at its dimmest can be located with good binocular
Binocular
Binocular may refer to:* Binocular vision, seeing with two eyes* Binoculars, a telescopic tool* Binocular, a thoroughbred race horse* Binocular , Kevin Rudolf's band that released a self-titled album in 2001....
s. In the sky it is about 1 degree northwest of the Wild Duck Cluster
Wild Duck Cluster
The Wild Duck Cluster is an open cluster in the constellation Scutum. It was discovered by Gottfried Kirch in 1681. Charles Messier included it in his catalogue in 1764....
(Messier 11).
Distance
HipparcosHipparcos
Hipparcos was a scientific mission of the European Space Agency , launched in 1989 and operated between 1989 and 1993. It was the first space experiment devoted to precision astrometry, the accurate measurement of the positions of celestial objects on the sky...
gives a parallax
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. The term is derived from the Greek παράλλαξις , meaning "alteration"...
of 2.32 milli-arcseconds for R Sct, giving it an estimated distance of 431 pc. But a period–luminosity relation similar to what is used for Cepheid variables suggests that R Sct is at a distance of 750 pc with a luminosity
Luminosity
Luminosity is a measurement of brightness.-In photometry and color imaging:In photometry, luminosity is sometimes incorrectly used to refer to luminance, which is the density of luminous intensity in a given direction. The SI unit for luminance is candela per square metre.The luminosity function...
of around 9400 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...
s. But this would make R Sct twice as luminous as the next most luminous RV Tau-type star in the study. The author of the period–luminosity study doubts the high luminosity and resulting distance, and it has been argued (Matsuura2002) that R Sct is a thermal-pulsing AGB star, observed in a helium-burning phase instead of a post-AGB star.
External links
- AAVSO: Quick Look View of AAVSO Observations (get recent magnitude estimates for R Sct)