R Aquarii (R Aqr) is a
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 ...
in the
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 ...
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 ...
.
R Aquarii is a
symbiotic star
A symbiotic binary is a type of binary star system, often simply called a symbiotic star. They usually contain a white dwarf with a companion red giant. The cool giant star loses material via Roche lobe overflow or through its stellar wind, whic ...
believed to contain a
white dwarf
A white dwarf is a stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very dense: its mass is comparable to the Sun's, while its volume is comparable to the Earth's. A white dwarf's faint luminosity comes fro ...
and a
Mira-type variable in a binary system. The
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 ...
is approximately 44 years.
[ The main Mira-type star is a ]red giant
A red giant is a luminous giant star of low or intermediate mass (roughly 0.3–8 solar masses ()) in a late phase of stellar evolution. The outer atmosphere is inflated and tenuous, making the radius large and the surface temperature around or ...
, and varies in brightness by a factor of several hundred and with a period of slightly more than a year; this variability was discovered by Karl Ludwig Harding
Karl Ludwig Harding (29 September 1765 – 31 August 1834) was a German astronomer, who discovered 3 Juno, the third asteroid of the main-belt in 1804. The lunar crater '' Harding'' and the asteroid 2003 Harding are named in his honor. ...
in 1810. It has a distance of about 390 parsec
The parsec (symbol: pc) is a unit of length used to measure the large distances to astronomical objects outside the Solar System, approximately equal to or (au), i.e. . The parsec unit is obtained by the use of parallax and trigonometry, and ...
s,[ and is one of the nearest symbiotic stars and a well-known jet source. The two components have been resolved at a separation of 55 mas.]
By its gravitation
In physics, gravity () is a fundamental interaction which causes mutual attraction between all things with mass or energy. Gravity is, by far, the weakest of the four fundamental interactions, approximately 1038 times weaker than the stron ...
al pull, the white dwarf draws in material from the red giant and occasionally ejects some of the surplus in loops to form the nebula seen in the linked image. The whole system appears reddened because it is situated in a very dusty region of space, and its blue light is absorbed before reaching Earth.
The nebula around R Aquarii is also known as Cederblad 211. It is possible that the nebula is the remnant of a nova-like outburst, which may have been observed by Japanese astronomers, in the year 930 AD. It is reasonably bright but small and dominated by its central star. Visual observations are difficult and rare. The central region of the jet shows an ejection that took place around 190 years ago, as well as much younger structures.
The giant primary star is a Mira variable
Mira variables (named for the prototype star Mira) are a class of pulsating stars characterized by very red colours, pulsation periods longer than 100 days, and amplitudes greater than one magnitude in infrared and 2.5 magnitude at visual wavelen ...
, a star that pulsates and changes temperature, leading to very large visual brightness changes. The total range of 5.2 - 12.4 is a variation of 750 times in brightness, from a naked eye star to one beyond the range of binoculars. The pulsations occur every 390 days but are not entirely regular.[
]
Gallery
References
External links
Weird loop image in R Aquarii
*
*
AAVSO Variable Star of the Month. R Aquarii: Summer 2003
Visual observation of a symbiotic star
{{Stars of Aquarius
Aquarius (constellation)
M-type giants
Mira variables
Spectroscopic binaries
222800
Aquarii, R
8992
117054
Durchmusterung objects
Z Andromedae variables