As they ingest matter from neighbouring disks, class 0 protostars frequently emit bright bursts of light. A recent analysis of data from NASA’s decommissioned Spitzer Space Telescope reveals that newborn stars “feed” at a furious rate and grow through surprisingly frequent feeding frenzies.
The analysis discovered that outbursts from stellar babies occur roughly every 400 years at the earliest stage of development when they are about 100,000 years old, or the equivalent of a 7-hour-old infant. These luminosity explosions are evidence of feeding frenzy episodes as the young, developing stars consume matter from the gas and dust disks that surround them.
“When you’re watching star formation, clouds of gas collapse to form a star. It’s literally the process of star creation in real time,”
University of Toledo astronomer Tom Megeath said.
Class 0 Protostars
Space telescope images captured in infrared light reveal otherwise unseen details, as in this image of star-forming regions in the Orion Nebula. A recent study that relied on infrared data tracked frequent outbursts from baby stars as they gathered mass from surrounding disks of gas and dust. Credit: ESA/NASA/JPL-Caltech
The study, led by Wafa Zakri, a professor at Saudi Arabia’s Jazan University, is a significant step forward in understanding the formative years of stars. Until now, it has been difficult to study the formation and early development of the very youngest stars because they are mostly hidden from view inside the clouds from which they form.
These young stars — less than 100,000 years old and known as Class 0 protostars — and their outbursts are especially difficult to observe using ground-based telescopes because they are encased in thick envelopes of gas. The first such outburst was discovered nearly a century ago, and they’ve only been seen a few times since.
Spitzer, which completed a 16-year run of observations from orbit in 2020, saw the universe in the infrared, which human eyes cannot see. Spitzer was able to see through gas and dust clouds and pick up bright flares from the stars nestled inside because of this, as well as its long-lasting gaze.
Baby Star Bursts
The researchers looked for protostar outbursts in the Orion constellation’s star-forming clouds between 2004 and 2017 using Spitzer data — a long enough look to catch baby stars in the act of exploding.
They found three outbursts among 92 known class 0 protostars, two of which were previously unknown. The data revealed a likely burst rate of roughly every 400 years for the youngest baby stars, which is much higher than the rate measured from the 227 older protostars in Orion.
They also compared Spitzer data to that of other telescopes, such as the now-retired ESA (European Space Agency) Herschel Space Telescope, the space-based Wide-field Infrared Survey Explorer (WISE), and the airborne Stratospheric Observatory for Infrared Astronomy (SOFIA).
This enabled them to calculate that the bursts typically last 15 years. During the early class 0 period, half or more of a baby star’s bulk is added.
“By cosmic standards, stars grow rapidly when they are very young. It makes sense that these young stars have the most frequent bursts,”
Megeath said.
Raw Planet Formation Material
The new findings will aid astronomers in better understanding how stars form and accumulate mass, as well as how these early bouts of mass consumption may affect planet formation later on.
“The disks around them are all raw material for planet formation,”
he said. Bursts can actually influence that material, possibly causing molecules, grains, and crystals to form and stick together to form larger structures. It’s even conceivable that our own sun was once a burping baby.
“The sun is a bit bigger than most stars, but there’s no reason to think that it didn’t undergo bursts. It probably did. When we witness the process of star formation, it is a window into what our own solar system was doing 4.6 billion years ago,”
Megeath said.
Reference: Wafa Zakri et al. The Rate, Amplitude, and Duration of Outbursts from Class 0 Protostars in Orion. The Astrophysical Journal Letters 924 L23 DOI 10.3847/2041-8213/ac46ae