AFGL 2298

AFGL 2298, also known as IRAS 18576+0341, is a luminous blue variable star (LBV) located in the constellation Aquila, very close to the galactic plane. Its distance is not well known; it may be anywhere between 23,000 and 42,000 light years (7,000 to 13,000 parsecs) away from the Earth.^[4] Despite being extremely luminous, it is extremely reddened by interstellar extinction, so its apparent magnitude is brighter for longer-wavelength passbands; in fact, in visual wavelengths it is completely undetectable.^[7]

AFGL 2298

A near-infrared (J band) light curve for AFGL 2298, adapted from Clark et al. (2009)[1]
Observation data Epoch J2000      Equinox J2000
Constellation	Aquila
Right ascension	19h 00m 10.89s[2]
Declination	+03° 45′ 47.1″[2]
Characteristics
Spectral type	B8I,[3] B:I:[e],[4] B0-0.5I[5]
Apparent magnitude (J)	12.164[2]
Apparent magnitude (H)	8.918[2]
Apparent magnitude (K)	6.91[6]
Variable type	LBV[4]
Astrometry
Distance	30,000±10,000 ly (10,000±3,000[4] pc)
Absolute bolometric magnitude (Mbol)	−11.25[1]
Details
Radius	158 - 385[1] R☉
Luminosity	1,300,000 - 2,000,000[1] L☉
Temperature	11,000 - 15,500[1] or 26,000[5] K
Other designations
V1672 Aql, RAFGL 2298, IRAS 18576+0341, 2MASS J19001089+0345471[7]
Database references
SIMBAD	data

AFGL 2298 was discovered during the US Air Force Geophysical Laboratory (AFGL) survey, a rocket based infrared sky survey conducted at Hanscom Air Force Base, whose results were published in 1975.^[8]

AFGL 2298 has an absolute bolometric magnitude of −11.25,^[1] making it one of the most luminous stars known. Indeed, many of the hottest and most luminous stars known are luminous blue variables and other early-type stars. However, like all LBVs, AFGL 2298 is highly variable and the bolometric magnitude refers to its peak luminosity.^[1] Its status as an LBV was confirmed in 2003.^[4]

Like most extremely massive stars, AFGL 2298 is undergoing mass loss.^[5] For example, in 2005 it was estimated to be losing 3.7×10⁻⁵ solar masses each year,^[5] although the rate of mass loss itself varies frequently and dramatically.^[1] The stellar mass is currently being ejected as a nebula around the star (similar to AG Carinae), which was imaged by the Very Large Telescope in 2010.^[9] The nebula was found to be fairly circular, and the properties of the dust appeared to be constant throughout the entire nebula.^[9]

Properties of AFGL 2298 over time^[1]

	Effective temperature (K)	Mass loss rate (M☉/yr)	Bolometric luminosity (L☉)
June 2001	11,700	4.5×10−5	1.5×106
August 2002	10,900	1.2×10−4	1.3×106
June 2006	10,300	5.2×10−5	2.0×106
May 2007	10,900	4×10−5	1.5×106

See also

• AG Carinae
• List of most luminous stars