NASA astronomers have for the first time detected an outburst from a star believed to be in the earliest stages of its development – an eruption that they believe reveals a sudden accumulation of gas and dust by an exceptionally young star also known as a protostar.
Using data obtained from the Spitzer Space Telescope and other orbiting instruments, as well as from ground-based observatories, an international team of researchers discovered the activity in an object known as HOPS 383, an short-lived star categorized as a “Class 0” protostar.
Stars form inside of collapsing fragments of cold gas clouds, scientists at the US space agency explained. As the cloud contracts under its own gravity, its center becomes increasingly dense and hotter. By the end of this process, the collapsing fragment has transformed into a “Class 0” protostar that is surrounded by a dusty disk roughly equal in mass.
First outburst we’ve ever seen
The Class 0 phase, which is also embedded in a dense envelope of gas and dust, is a short-lived phase of stellar development that lasts approximately 150,000 years. It is considered to be the first stage of development for sun-like stars, and at this point it has not yet developed the ability to produce energy by fusing hydrogen into helium at its core, the researchers added.
Instead, protostars shine from the heat energy given off by its contraction and the accumulation of material from the gas-and-dust disk that surrounds it. Since these infant suns are surrounded by such thick material, their visible light cannot escape. However, the light warms dust around the protostar, which reradiates the energy in the form of heat that can be detected using infrared sensitive instruments on both ground-based and orbiting telescopes and instruments.
HOPS 383, which is located approximately 1,400 light years from Earth near NGC 1977 in the constellation Orion, “is the first outburst we’ve ever seen from a Class 0 object, and it appears to be the youngest protostellar eruption ever recorded,” William Fischer, a Postdoctoral Program Fellow at the NASA Goddard Space Flight Center in Maryland, said in a statement.
Lurking the whole time
Thomas Megeath at the University of Toledo in Ohio and his colleagues used Spitzer to identify over 300 protostars in a star-forming complex in Orion, and an associated project that used the ESA’s Herschel Space Observatory, called the Herschel Orion Protostar Survey (HOPS), studied several of those objects in greater detail. The eruption of HOPS 383 was first recognized in 2014 by astronomer Emily Safron shortly following graduation from the University of Toledo.
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With Megeath and Fischer guiding her, Safron had recently completed a senior thesis comparing the several-decade-old Spitzer Orion survey with more recent 2010 observations made using the Wide-field Infrared Survey Explorer (WISE) satellite. Safron has used computer software to look at the data several times during her thesis, but upon its completion decided to compare images of the objects with the naked eye. That’s when she first noticed HOPS 383’s eruption.
“This beautiful outburst was lurking in our sample the whole time,” she said, noting that the protostar was so deeply blanketed by dust that it had not been seen at all prior to the outburst at the shortest Spitzer wavelength. Furthermore, an oversight in a version of the catalog produced before Safron’s involvement masked the increase at the longest wavelengths.
“As a result, her software saw a rise in brightness in only one wavelength out of three, which failed to meet her criteria for the changes she was hoping to find,” NASA said. “Once they realized what had happened, Safron, Fischer and their colleagues gathered additional Spitzer data, Herschel observations, and images from ground-based infrared telescopes.”
Their findings were published in the February 10 edition of The Astrophysical Journal.