Hubble Reveals New Mysteries in 40-Year-Old Stellar Explosion

Recent observations of the Sagittae system show unexpected changes in temperature and luminosity, providing fresh insights into stellar evolution.

HM Sagittae, a binary star system, erupted as a bright nova in 1975 and has remained unusually luminous for decades.
New data from Hubble and SOFIA reveals the system has become hotter but has paradoxically dimmed slightly.
The white dwarf in the system shows increased temperatures, evidenced by a strong emission line of highly ionized magnesium.
Infrared data indicates the giant companion star returned to normal behavior quickly after the explosion but has dimmed recently.
Amateur astronomers continue to monitor HM Sagittae, contributing to the understanding of this rare and dynamic stellar event.