AFGL 2298

Lore & Background

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, with results published in 1975. Its status as a luminous blue variable star was confirmed in 2003. Like most extremely massive stars, AFGL 2298 is undergoing mass loss; in 2005 it was estimated to be losing a certain number of solar masses each year, though the rate varies frequently and dramatically. The stellar mass is currently being ejected as a nebula around the star, similar to AG Carinae. This nebula was imaged by the Very Large Telescope in 2010 and found to be fairly circular, with the properties of the dust appearing constant throughout the entire nebula.

Reader's Guide

AFGL 2298 is significant as one of the most luminous stars known, with an absolute bolometric magnitude of −11.25 at peak brightness, placing it among the hottest and most luminous early-type stars, many of which are luminous blue variables. Its extreme luminosity is counterbalanced by heavy interstellar extinction, making it invisible at visual wavelengths and detectable only in the infrared. The star's mass loss, estimated in 2005 at a rate that varies dramatically, feeds a surrounding nebula imaged in 2010 by the Very Large Telescope. The nebula's circular shape and uniform dust properties provide insight into the star's recent mass-loss history. As an LBV, AFGL 2298 represents a brief, unstable phase in the evolution of the most massive stars, and its study contributes to understanding stellar evolution and the enrichment of the interstellar medium. Its discovery via the AFGL rocket survey highlights the importance of infrared observations in revealing objects hidden by galactic dust.

Did You Know?

• AFGL 2298 is completely undetectable at visual wavelengths due to extreme interstellar reddening.
• Its absolute bolometric magnitude of −11.25 makes it one of the most luminous stars known.
• The star's mass-loss rate varies frequently and dramatically, as estimated in 2005.
• The surrounding nebula, imaged by the Very Large Telescope in 2010, is fairly circular with uniform dust properties.