Difference between revisions of "Variable Stars"
(→Variable Star Types) |
|||
| Line 3: | Line 3: | ||
=Variable Star Types= | =Variable Star Types= | ||
Variable stars have a wide number of classifications, with the main types listed below. | Variable stars have a wide number of classifications, with the main types listed below. | ||
| + | ==Classification== | ||
| + | |||
| + | Variable stars may be either ''intrinsic'' or ''extrinsic''. | ||
| + | |||
| + | *'''Intrinsic variable stars''': stars where the variability is being caused by changes in the physical properties of the stars themselves. This category can be divided into three subgroups. | ||
| + | **Pulsating variables, stars whose radius alternately expands and contracts as part of their natural evolutionary ageing processes. | ||
| + | **Eruptive variables, stars who experience eruptions on their surfaces like flares or mass ejections. | ||
| + | **Cataclysmic or explosive variables, stars that undergo a cataclysmic change in their properties like [[nova]]e and [[supernova]]e. | ||
| + | |||
| + | *'''Extrinsic variable stars''': stars where the variability is caused by external properties like rotation or eclipses. There are two main subgroups. | ||
| + | **Eclipsing binaries, [[double star]]s where, as seen from [[Earth]]'s vantage point the stars occasionally eclipse one another as they orbit. | ||
| + | **Rotating variables, stars whose variability is caused by phenomena related to their rotation. Examples are stars with extreme "sunspots" which affect the apparent brightness or stars that have fast rotation speeds causing them to become ellipsoidal in shape. | ||
| + | |||
| + | These subgroups themselves are further divided into specific types of variable stars that are usually named after their prototype. For example, dwarf novae are designated ''U Geminorum'' stars after the first recognized star in the class, ''U Geminorum''. | ||
=Intrinsic= | =Intrinsic= | ||
Revision as of 10:45, 28 April 2014
A variable star is a star where its brightness as seen from Earth fluctuates. The study of variable stars involves the recording of its magnitude, and how that fluctuates over time. The plotting of a variable star's magnitude vs. time is known as a light curve. The light curve plotting of variable stars combined with the study of supernovae events help physicists understand the formation of the universe.
Contents
Variable Star Types
Variable stars have a wide number of classifications, with the main types listed below.
Classification
Variable stars may be either intrinsic or extrinsic.
- Intrinsic variable stars: stars where the variability is being caused by changes in the physical properties of the stars themselves. This category can be divided into three subgroups.
- Pulsating variables, stars whose radius alternately expands and contracts as part of their natural evolutionary ageing processes.
- Eruptive variables, stars who experience eruptions on their surfaces like flares or mass ejections.
- Cataclysmic or explosive variables, stars that undergo a cataclysmic change in their properties like novae and supernovae.
- Extrinsic variable stars: stars where the variability is caused by external properties like rotation or eclipses. There are two main subgroups.
- Eclipsing binaries, double stars where, as seen from Earth's vantage point the stars occasionally eclipse one another as they orbit.
- Rotating variables, stars whose variability is caused by phenomena related to their rotation. Examples are stars with extreme "sunspots" which affect the apparent brightness or stars that have fast rotation speeds causing them to become ellipsoidal in shape.
These subgroups themselves are further divided into specific types of variable stars that are usually named after their prototype. For example, dwarf novae are designated U Geminorum stars after the first recognized star in the class, U Geminorum.
Intrinsic
Intrinsic Variable stars are stars which vary their light output, where the variability is being caused by changes in the physical properties of the stars themselves. These stars provide information about the internal structure of stars and provide astronomers with informational to support models of stellar evolution.
Pulsating Stars
Pulsating variable stars experience periodic expansion and contraction of the surface layers of the stars. Pulsating variables actually increases and decreases in size periodically, creating light curves which give clues to the interior processes of the stars. Pulsating variables are also valuable in distance measurements to the stars. The four primary classifications of pulsating variables includes Cephids, RR Lyrae, RV Tauri, and Long-Period Variables.
Cepheids
Type I Classical
Type II W Virginis
RR Lyrae
RV Tauri
Long-Period Variables (LPVs)
Mira Type
Semiregular
Eruptive (cataclysmic stars)
Supernovae
Novae
Recurrent Novae
Dwarf Novae
Symbiotic Stars
R Coronae Borealis
Extrinsic
Eclipsing Binaries
Rotating Variables
Variable Star Resources
American Association of Variable Star Observers - (AAVSO) is a non-profit worldwide scientific and educational organization of amateur and professional astronomers who are interested in stars that change in brightness—variable stars.
arXiv.org Astrophysics - An e-print service in the fields of physics, mathematics, computer science, quantitative biology, quantitative finance and statistics maintained Cornell University.
Astrophysics Data System - The ADS maintains three bibliographic databases containing more than 10.8 million records: Astronomy and Astrophysics, Physics, and arXiv e-prints.
The British Astronomical Association: Variable Star Section - The VSS was formed in 1890, the year the BAA was founded, with the aim of collecting and analysing observations of variable stars.
Konkoly Observatory, Hungary - Variable Stars - The Information Bulletin on Variable Stars is a bulletin of the Commissions 27 and 42 of the International Astronomical Union, published by the Konkoly Observatory, Budapest, Hungary.
Royal Astronomical Society of New Zealand - The RASNZ has links to Variable Stars South, a group focused on Variable Stars in the Southern skies.
The SIMBAD astronomical database provides basic data, cross-identifications, bibliography and measurements for astronomical objects outside the solar system.
