Astronomers catch moment of star's birth

Posted by Emma Woollacott

What could be the youngest known star has been photographed in the earliest stages of being born.

Not yet fully developed into a true star, the object is in the earliest stages of formation and has just begun pulling in matter from a surrounding envelope of gas and dust, according to a new study in the Astrophysical Journal.

The study’s authors found the object using the Submillimeter Array in Hawaii and the Spitzer Space Telescope. Known as L1448-IRS2E, it’s located in the Perseus star-forming region of our Milky Way galaxy, about 800 light years away.

The team reckons it's in between the prestellar phase, when a particularly dense region of a molecular cloud first begins to clump together, and the protostar phase, when gravity has pulled enough material together to form a dense, hot core out of the surrounding envelope.

"It’s very difficult to detect objects in this phase of star formation, because they are very short-lived and they emit very little light," said Xuepeng Chen, a postdoctoral associate at Yale and lead author of the paper.

Most protostars are at least as luminous as the sun, with large dust envelopes that glow at infrared wavelengths. Because L1448-IRS2E is less than one tenth as bright as this, the team believes it's too dim to be considered a true protostar.

Yet they also discovered that the object is ejecting streams of high-velocity gas from its center, confirming that some sort of preliminary mass has already formed and the object has developed beyond the prestellar phase. This kind of outflow is seen in protostars as a result of the magnetic field surrounding the forming star, but has never before been seen at such an early stage.

"Stars are defined by their mass, but we still don’t know at what stage of the formation process a star acquires most of its mass," said Héctor Arce, assistant professor of astronomy at Yale and an author of the paper. "This is one of the big questions driving our work."