A cloud of dust and gas in space, called a nebula, seems to be changing colour and brightness in a rhythmic way every four years, like a galactic mood lamp.
The VISTA telescope in the Atacama desert in Chile can survey large tracts of the Milky Way to look for extremely rare events in our galactic neighbourhood, such as supernova explosions, the most recent of which happened in 1604.
at the Federal University of Santa Catarina in Brazil and his colleagues were looking for supernova signatures in VISTA observations over a nine-year period. They noticed a particularly strange nebula that appeared to be changing colour and brightness in sync with a source of light, which they called VVV-WIT-12. WIT is short for 鈥渨hat is this?鈥� 鈥� a label the team gave to objects that couldn鈥檛 easily be classified.
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鈥淔rom our database, which is more than 1 billion objects and more than 17,000 square degrees in the sky, this is the only source with this kind of behaviour,鈥� says Saito.
Not only did the nebula change colour over a four-year period, but it also appeared to be out of sync with itself 鈥� when the side closest to Earth got brighter, the side furthest away dimmed, and vice versa. 鈥淭his was kind of surprising to us,鈥� says Saito. 鈥淭o understand this is challenging.鈥�
Saito and his colleagues鈥� best guess is that the object is an unusual young star in the process of forming, which can display the kind of variability they see. However, to really understand the star鈥檚 nature, they will need a detailed spectrum to reveal its chemical make-up, which VISTA isn鈥檛 capable of providing.
Future observations with newer, large-scale survey telescopes, like the Vera C. Rubin Observatory in Chile, will be able to gather more detail on the object, says Saito.
鈥淚t鈥檚 a cool discovery,鈥� says at the University of St Andrews, UK. 鈥淟arge-scale variability surveys have the potential to find weird, strange and difficult-to-interpret objects, and this is another example of that.鈥�
The star could help explain how young stars form from nebulae, but more information will be needed about the nebula first, says Scholz.
arXiv
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