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Star in birth reportedly witnessed

June 18, 2010
Courtesy of Yale University
and World Science staff

As­tro­no­mers are re­port­ing that they have glimpsed what could be the youngest known star at the mo­ment of its birth. 

Not yet de­vel­oped in­to a true star, the ob­ject has just be­gun pulling in mat­ter from a sur­round­ing en­ve­lope of gas and dust, ac­cord­ing to a new study that ap­pears in the cur­rent is­sue of The As­t­ro­phys­i­cal Jour­nal.

A star-forming re­gion si­mi­lar to the one where astro­nomers say they have found a star in its ear­li­est stages of for­ma­tion. The re­gion pic­tured above is known as the Orion-KL re­gion. (Pho­to: NA­SA, ESA)


The au­thors found the ob­ject us­ing the Spitzer Space Tel­e­scope and the Sub­mil­lime­ter Ar­ray tel­e­scope in Ha­waii. It lies in the Per­seus star-form­ing re­gion, about 800 light years away with­in our Milky Way gal­axy. (A light-year is the dis­tance light tra­vels in a year).

Stars form out of large, cold, dense re­gions of gas and dust called mo­lec­u­lar clouds, which pep­per the gal­axy. 

As­tro­no­mers think the new­found ob­ject is in be­tween its 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 Uni­vers­ity and lead au­thor of the pa­per. The team de­tected the faint light emitted by the dust sur­round­ing the ob­ject.

Most pro­to­stars are be­tween one to 10 times as lu­mi­nous as the Sun, with large dust en­ve­lopes that glow in in­fra­red light, a low-energy form of light not vis­i­ble to the un­aided eye. 

Be­cause the new ob­ject, dubbed L1448-IRS2E, is less than one tenth as lu­mi­nous as the Sun, the as­tro­no­mers be­lieve it’s too dim to be a true pro­to­star. Yet they al­so found it’s eject­ing streams of high-speed gas from its cen­ter, con­firm­ing, they said, that some sort of pre­lim­i­nar­y mass has formed and the ob­ject is be­yond its pre­stel­lar phase. This kind of out­flow is seen in pro­to­stars as a re­sult of the mag­net­ic field sur­round­ing the form­ing star, but has not been seen at such an early stage un­til now.

The team hopes to use the new Hers­chel space tel­e­scope, launched last May, to look for more of these ob­jects caught be­tween the ear­li­est stages of star forma­t­ion so they can bet­ter un­der­stand how stars grow and evolve. “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 Yale’s Héc­tor Ar­ce, an­oth­er au­thor of the pa­per. “This is one of the big ques­tions driv­ing our work.”

The re­search group al­so in­cludes as­tro­no­mers from the Har­vard-Smith­son­ian Cen­ter for As­t­ro­phys­ics in Cam­bridge, Mass. and the Max Planck In­sti­tute for As­tronomy in Hei­del­berg, Ger­ma­ny.


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Astronomers are reporting that they have glimpsed what could be the youngest known star at the moment of its birth. Not yet developed into a true star, the object has just begun pulling in matter from a surrounding envelope of gas and dust, according to a new study that appears in the current issue of the Astrophysical Journal. The authors found the object using the Submillimeter Array in Hawaii and the Spitzer Space Telescope. It lies in the Perseus star-forming region, about 800 light years away within our Milky Way galaxy. Stars form out of large, cold, dense regions of gas and dust called molecular clouds, which exist throughout the galaxy. Astronomers think the newfound object is 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 University and lead author of the paper. The team detected the faint light emitted by the dust surrounding the object. Most protostars are between one to 10 times as luminous as the Sun, with large dust envelopes that glow in infrared light, a low-energy form of light not visible to the unaided eye. Because the new object, dubbed L1448-IRS2E, is less than one tenth as luminous as the Sun, the astronomers believe it’s too dim to be a true protostar. Yet they also found it’s ejecting streams of high-speed gas from its center, confirming, they said, that some sort of preliminary mass has formed and the object is beyond its prestellar phase. This kind of outflow is seen in protostars as a result of the magnetic field surrounding the forming star, but has not been seen at such an early stage until now. The team hopes to use the new Herchel space telescope, launched last May, to look for more of these objects caught between the earliest stages of star formation so they can better understand how stars grow and evolve. “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 Yale’s Héctor Arce, another author of the paper. “This is one of the big questions driving our work.” The research group also includes astronomers from the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. and the Max Planck Institute for Astronomy in Heidelberg, Germany.