RR Lyrae

RR Lyrae
RR Lyrae are variable, horizontal branch stars with periods ranging from a few hours to 2 days, and optical brightnesses that typically vary between 0.3 and 2 magnitudes.

Rr Lyrae
Related Category: Astronomy: General
see variable star.
More on Rr Lyrae
Variable Star - star that varies, either periodically or irregularly, in the intensity of the light it emits.

RR Lyrae stars were first discovered in the late nineteenth century, where they were found in great numbers in globular clusters. They were first called ``cluster variables,'' a name which they retained for many decades.

RR Lyrae
Another type of pulsating star similar to the Cepheids are the RR Lyrae variable stars (named after the prototype star RR Lyrae). They are smaller than Cepheids and, therefore, have shorter periods and lower luminosities.

RR Lyrae
These old population II giant stars are mostly found in globular clusters. They are characterised by their short periods, usually about 1.5 hours to a day and have a brightness range of 0.3 to 2 magnitudes.

RR Lyrae stars. These are lower-luminosity stars, where the instability strip crosses the horizontal branch. They may appear on cluster H-R diagrams by omission in the "RR Lyrae gap", since variables are usually not plotted.

RR Lyrae star Variable star whose luminosity changes in a characteristic way. All RR Lyrae stars have more or less the same period.

RR Lyrae Variable
Variable stars with periods of 12-24 hours, common in some globular clusters.
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RR Lyrae Stars
A large class of pulsating (amplitude variation about 1 mag) blue giants of anomalous spectral type (A2-F6) with periods of less than 1 day. Their average absolute magnitude is about +0.8.

RR Lyrae variable star: Variable star with a period of 12 to 24 hours; common in some globular clusters.
Sagittarius A*: The powerful radio source located at the core of the Milky Way Galaxy.

RR Lyrae Star - A member of a class of giant pulsating stars, all of which have pulsation periods of about 1 day
Runoff Channel - One of a network of Martian valleys that probably were formed by the collection of widespread rainfall ...

RR LYRAE STARS
Variable stars similar to the cepheids. They are blue giants with periods of about ten to fifteen hours and they change in brightness by about one magnitude.
R TYPE STARS ...

RR Lyrae is a prototype for a pulsating type of variable with short periods, usually less than twenty-four hours. RR Lyrae's period is 13h36m, and it changes in magnitude from 7.1 to 8.1.
Deep Sky Objects in Lyra: ...

RR Lyrae stars are a sub-classification of Cephied variables. They have a much shorter oscillation period - usually less than a day - and are all about 90 times brighter than the Sun.

RR Lyrae variable - (n.)
A member of a class of pulsating variable stars named after the prototype star, RR Lyrae.

RR Lyrae Variables: A variable star that has a regularly varying luminosity. These stars all have about the same luminosity making them suitable for obtaining distances.

see RR Lyrae star. [H76]
Clustering
In cosmology, the observed tendency of galaxies to bunch together, rather than to distribute themselves uniformly and independently of each other. [LB90]
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RR Lyrae Distance
RR Lyrae stars are pulsating stars like Cepheids, but they are low mass stars with short periods (less than a day). They are seen in globular clusters, and appear to all have the same luminosity.

Cepheids and RR Lyrae Stars.
Figure 3. Light variation of a Cepheid variable. It is plotted so that two cycles of pulsation are shown.

Short-period Cepheids, also called cluster-type variables, or RR Lyrae variables, all have periods of less than one day and show no dependable relationship between period and luminosity; ...

Instead, distance indicators whose origins are in an older stellar population (like novae and RR Lyrae variables) must be used.

Una estrella variable famosa y bien estudiada, RR Lyrae es el prototipo de su clase. Durante un período aproximado de 13 horas, la estrella deja de brillar en más de un factor de dos y después vuelve a su brillo inicial.

Another class of variable star is the low mass red giant type star known as an RR Lyrae variable. These are located at the low luminosity end of the instability strip and they have periods less than a day.

The most commonly used standard candles are Cepheid variable stars and RR Lyrae stars. In both cases, the absolute magnitude can be determined from its variability period.

Identification of stars within a given constellation includes use of Bayer designations such as Alpha Centauri, Flamsteed designations such as 61 Cygni, and variable star designations such as RR Lyrae.

The second group has a slightly longer period of RR Lyrae variable stars. Both groups have weak lines of metallic elements. But the lines in the stars of Oosterhoff type I (OoI) cluster are not quite as weak as those in type II (OoII).

Another star that serves as a prototype for an entire group of stars is RR Lyrae, a variable star that varies in brightness between magnitudes 7 and 8 within a period of about 13 hours.

RR: RR Lyrae stars, low mass pulsating stars with helium-fusing cores. They have variation amplitudes of a few tenths of a magnitude and periods under a day. Their uniform absolute magnitudes make them good distance indicators.

Among A-type peculiar stars are Ae stars, Am stars, and Ap stars. Also, two of the main kinds of pulsating variables, RR Lyrae stars and Delta Scuti stars, have surface temperatures in the A-star range.
Related category
- TYPES OF STAR ...

These names include Bayer designations such as Alpha Centauri, Flamsteed designations such as 61 Cygni, and variable star designations such as RR Lyrae. For more information about star names, see Star designations.

Also called Population II stars because of their later discovery, this group also includes RR Lyrae variables with periods greater than 12 hours, subdwarfs and other extremely metal-poor stars, and some red giants.

He continued to research and publish papers right up until his death, his last paper on RR Lyrae variable stars (another kind of standard candle) appearing in the Astrophysical Journal in June.

RR Lyrae stars allow measurement of distances to globular clusters.spectroscopic parallax: the distance obtained by observing a star's color, correcting for Doppler shift, inferring the star's luminosity from a calibrated HR diagram, ...

See also: Star, Cluster, Variable star, Distance, Sun