R Aquarii

From Wikipedia, the free encyclopedia

**R Aquarii**
Observation data Epoch J2000
R Aquarii
Constellation (pronunciation)	Aquarius
Right ascension	23^h 43^m 49.4616^s
Declination	-15° 17′ 04.202″
Apparent magnitude (V)	7.69
Characteristics
Spectral type	M7IIIpev
U-B color index	0.32
B-V color index	1.58
Variable type	pulsating variable star
Astrometry
Radial velocity (R_v)	-22 km/s
Proper motion (μ)	RA: 32.98 mas/yr Dec.: -32.61 mas/yr
Parallax (π)	5.07 ± 3.15 mas
Distance	approx. 600 ly (approx. 200 pc)
Absolute magnitude (M_V)	8.83
Details
Mass	? M_☉
Radius	? R_☉
Luminosity	? L_☉
Temperature	? K
Metallicity	?
Rotation	386.96 days
Age	? years
Other designations
V* R Aqr, GSC 06404-00077, IRC -20642, BD-16 6352, HD 222800, 2MASS J23434939-1517043, TYC 6404-77-1, EM* MWC 400, HIC 117054, PPM 242022, YZ 105 8733, GC 32948, HIP 117054, RAFGL 3136, GCRV 14862, HR 8992, 1RXS J234351.0-151655, AAVSO 2338-15, IRAS 23412-1533, SAO 165849.
Database references
SIMBAD	data

R Aquarii (R Aqr) is a variable star in the constellation Aquarius.

R Aquarii is a symbiotic star believed to contain a white dwarf and a Mira-type variable in a binary system. The main Mira-type star is a red giant, and varies in brightness by a factor of several hundred and with a period of slightly more than a year; this variability has been discovered by Karl Ludwig Harding in 1810.

Aquarius Constellation

By its gravitational pull, the white dwarf draws in material from the red giant and occasionally ejects some of the surplus in the weird loops to form the nebula seen in the linked image.^[1] The whole system appears reddened because it is situated in a very dusty region of space, and its blue light is absorbed before reaching us.

The nebula around R Aquarii is also known as Cederblad 211. According to Tom Polakis ^[2], at that time, noone had succeeded to observe this challenging object visually. 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.