Astronomers have spotted the massive first growth spurt of a newborn star! By rapidly gobbling up the gas and dust surrounding it, the stellar baby became 35 times brighter in about two years. Called HOPS 383, the young protostar is located 1,400 light-years away near the NGC 1977 nebula within the constellation Orion. It was in its earliest phase of development when an eruption was detected in data from multiple space- and ground-based instruments. And the latest data suggest that it’s still going strong.
Stars are born within the collapsing fragments of cold gas clouds contracting under their own gravity. As the center becomes both denser and hotter, the collapsing fragment eventually transforms into a hot central protostar surrounded by a dusty, gassy disk roughly equal to it in mass. This is what’s called a "Class 0" protostar, and this short-lived phase lasts just 150,000 years. "HOPS 383 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 of NASA's Goddard Space Flight Center says in a news release.
A protostar hasn’t developed its energy-generating capabilities yet, but it still shines because of the heat energy that’s released by its contraction and by the accumulation of material from the disk of gas and dust. (Asteroids, comets, and planets may form from this disk later on.) Using NASA's Spitzer Space Telescope, astronomers have found more than 300 protostars in the sprawling Orion star-formation complex, and they were studied in detail using ESA's Herschel Space Observatory—part of the Herschel Orion Protostar Survey (HOPS). Since these baby sun-like stars are swaddled in gas and dust, their visible light can’t escape. So it warms the dust around the star, which then reradiates that energy as heat that’s detectable by infrared-sensitive instruments.
University of Toledo’s Emily Safron first recognized the eruption of HOPS 383 in 2014 using data from Spitzer and the Wide-field Infrared Survey Explorer (WISE) satellite. The first hint of brightening appeared in 2006 Spitzer data, and by 2008, HOPS 383’s brightness at a wavelength of 24 microns had increased by 35 times. Additional data were gathered from the Kitt Peak National Observatory in Arizona and the Atacama Pathfinder Experiment in Chile. As of 2012, the eruption showed no sign of fading.
"An outburst lasting this long rules out many possibilities, and we think HOPS 383 is best explained by a sudden increase in the amount of gas the protostar is accreting from the disk around it," Fischer adds. It’s possible that instabilities in the surrounding disk triggered the flow of large amounts of material onto the protostar, creating a hotspot at the impact point that heated up the disk—brightening them both up intensively.
These findings were published in The Astrophysical Journal in February.