Stars, like babies, make quite a fuss in their first days after birth Taking their closest look ever inside the womb where a star is born, astronomers found surprisingly hot flares coming from otherwise cold stellar embryos.
These stars-to-be -- also called protostars, and sometimes just considered baby stars -- are less than 100,000 years old and still gathering themselves together. They will use their gravity to accumulate more material from a surrounding womb of gas and dust. And eventually they will be massive enough to contract, become more dense and jump-start thermonuclear fusion.
Then they will have an internal furnace like the one that drives our Sun, a more mature star.
But these bambinos probably aren't even in diapers yet. And without an interior furnace, they are cold -- as much as minus 400 degrees Fahrenheit (minus 240 degrees Celsius).
So researchers were surprised to catch them emitting powerful flares of energy that were 10 times hotter and up to 100,000 times brighter than flares on our Sun. Temperatures in the flares reached 180 million degrees Fahrenheit (100 million degrees Celsius).
"We peered at newborn stars deeply embedded in their cradle and found that their crying is much more tumultuous than we expected," said Yohko Tsuboi of the Pennsylvania State University, lead researcher in the study.
Out of hiding
A stellar embryo lives in an envelope of gas and dust, a womb that is consumed to feed the fledgling star. Our own Sun was born in such a "molecular cloud," as were the nine planets.
These clouds block astronomers' views of what's going on inside. But the powerful orbiting Chandra X-ray Observatory peered straight through the clouds and measured energy in the X-ray spectrum, which is not visible in normal telescopes, or to the eye.
Why the hot temper?
"The X-ray flares from protostars occur most likely due to the same mechanisms as those on the Sun," Tsuboi told SPACE.com.
The process involves large loops of magnetic energy that reach out into space and, somewhat mysteriously, snap back. Scientists are just beginning to understand how this works on the Sun. In the newly observed stellar embryos, these loops were enormous: up to 10 times the radius of our Sun.
"How such huge magnetic loops are formed and how the reconnections occur might be deeply linked with how a star contracts," Tsuboi said.
Scientists say our own infant Sun was prone to similar tantrums 5 billion years ago, when it was just a protostar. After a few million years, however, fusion took over and the Sun's emissions became more stable -- one of the preconditions for life as we know it.
Where the stars are
Tsuboi and her collaborators at Kyoto University in Japan looked at the two youngest types of protostars: Class 0 (zero) protostars, about 10,000 years old; and Class 1 protostars, about 100,000 years old.
They detected X-rays from 17 Class 1 protostars in the rho-Ophiuchi molecular cloud, 500 light-years from Earth in the constellation Ophiuchi. The astronomers saw nearly a dozen X-ray flares over a 27-hour period.
"Virtually all the Class 1 protostars in the rho-Ophiuchi molecular cloud may emit X-rays with extremely violent and frequent flare activity," said Kensuke Imanishi of Kyoto University.
In a different star-formation region, 1,400 light years from Earth in constellation Orion, the researchers observed for the first time activity from the youngest protostars, the Class 0 variety.
The findings were presented at the recent meeting of the High-Energy Astrophysics Division of the American Astronomical Society in Honolulu.
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