The Hubble Space Telescope has revealed a large group of unusual hot, bright, ultra-blue stars glowing in the heart of Andromeda, the second closest galaxy to the Milky Way, NASA announced.
Typical blue stars are massive hotbeds of activity that burn out while young, according to UniverseToday, but the population of ultra-blue stellar misfits the Hubble uncovered are old stars similar to Earth's sun that shed their outer layers, leaving their blue, extremely hot cores exposed, NASA reported about the surprising discovery presented at the 219th meeting of the American Astronomical Society this week.
The new observation, part of the Panchromatic Hubble Andromeda Treasury survey, expanded upon Hubble's earlier spotting of these stars in Andromeda (also known as known as NGC 224, Messier 31 and M31), and showed these rare stars are scattered all around the spiral galaxy's active center, though physical models suggest only one unusual type of old star can show up so hot and bright when observed in ultraviolet light.
According to the survey team, these stars puffed up to become red giants but ejected much more material than stars evolving normally that keep more outer layers and cannot appear as bright when peered at with ultraviolet waves.
The ultra-blue stars may have lost more material because they were extra-rich in chemical elements heavier than helium and hydrogen, or because their radiation pushed more efficiently on stellar gasses laced with heavy elements, the astronomers speculated.
Another possible explanation being considered involves blue stars losing mass to partner stars in close binary systems.
The team's next step is running computerized simulations to determine which scenario most likely shifted the evolutionary path of Andromeda's strange ultra-blue stars.