Newborn stars discovered in dark cosmic cloud

Jul 07, 2010
A dark, wispy cloud of dust (extending from the center, right) seems to billow out from a bright explosion in this false-color image in infrared light from the Spitzer Space Telescope. These views have revealed that the mystery cloud, called M17 SWex, is forming stars at a furious rate but has not yet spawned the most massive stars -- O stars. To the left, on the trailing end of the dark cloud, such mammoth O stars create a dramatic contrast of brilliant light near the image's center. Credit: NASA/JPL-Caltech/Matthew Povich (Penn State)

A wave of massive star formation appears poised to begin within a mysterious, dark cloud in the Milky Way. NASA's Spitzer Space Telescope has revealed a secluded birthplace for stars within a wispy, dark cloud named named M17 SWex. The dark cloud is part of the larger, parent nebula known as M17, a vast region of our galaxy with a bright, central star cluster. "We believe we've managed to observe this dark cloud in a very early phase of star formation before its most massive stars have ignited," said Penn State astronomer Matthew Povich, a postdoctoral fellow and the lead author of a study published recently in The Astrophysical Journal Letters. The new research could shed light on the question of how and when massive stars form.

Though astronomers first discovered the dark cloud in the Sagittarius constellation more than 30 years ago, it took the keenness of the Spitzer telescope's instruments to spot the hidden within. Spitzer's infrared vision has shown that M17 SWex is among the closest to Earth and also among the Milky Way's busiest star-making factories, with 488 newly forming stars. More than 200 will become blue-white class B stars, larger and hotter than our Sun. "Most of the stars we've detected are relatively bright," said Povich. "So we predict the actual number of stars forming in M17 SWex is over 10,000, since the fainter stars cannot be detected with the current observations."

Conspicuously absent from M17 SWex are the bluest, hottest, and biggest of new stars -- the class O stars. Though relatively rare in the cosmos, O stars are what light up neighboring regions within the colossal M17 nebula.

One possible answer to this riddle is that developing O stars -- wild, windy, and spewing radiation -- rapidly destroy their dusty envelopes, which Spitzer otherwise would sniff out. But a more likely explanation is that such gigantic stars form later, perhaps needing an extra "nudge" into existence. A shock wave from a burst of star births in the region could set off a chain of massive star formation -- a cosmic "domino effect." In support of this idea, Povich and his colleagues point to a giant "bubble" blown by blue O stars aged some two to five million years in the far left of the Spitzer image. Part of this great smoke ring appears to shape the left, curving border of the M17 nebula, whose interior is lit up by a about one-million years old. Farther to the right, the shrouded, budding stars in the dark M17 SWex cloud have not yet celebrated their one millionth birthdays -- truly infants in the stellar sense.

The architecture of our galaxy likely plays a role in this chronology. In its orbit around the Milky Way's center, the M17 region is now passing though the Sagittarius spiral arm, one of the giant bands of stars and gas pinwheeling out from our galaxy's hub. The greater concentration of gas and dust in the arm is mashing material together in the M17 region, triggering a round of massive star formation that moves through this cloud, causing a chain reaction.

"The time-sequence of star formation proceeds in the same direction that a spiral arm crosses the M17 cloud complex," Povich says. "The M17 region brings to mind images of other spiral galaxies where the leading edges of the arms appear blue, with young O stars, but the trailing edges are still dark, with obscuring dust like in M17 SWex." The time required, for the M17 region to pass through the edge of the Sagittarius spiral arm is about a million years.

Further investigation of the M17 SWex flying dragon and other clouds may reveal whether need this added oomph of an expanding shock wave to come to luminous life.

"We hope that astronomers will use M17 SWex as a new laboratory for studying the mystery of how massive really happens," says Povich. "Most very young clouds being studied don't have as much going on as this one does."

Explore further: Can astronomy explain the biblical Star of Bethlehem?

Related Stories

Celestial Season's Greetings from Hubble

Dec 19, 2006

Swirls of gas and dust reside in this ethereal-looking region of star formation imaged by NASA's Hubble Space Telescope. This majestic view, located in the Large Magellanic Cloud (LMC), reveals a region where ...

Hubble Observes Infant Stars in Nearby Galaxy

Jan 08, 2007

This new image taken with NASA's Hubble Space Telescope depicts bright, blue, newly formed stars that are blowing a cavity in the center of a star-forming region in the Small Magellanic Cloud.

AKARI's view on birth and death of stars

Aug 28, 2006

AKARI, the Japan Aerospace Exploration Agency (JAXA) infrared astronomical satellite with ESA participation, is continuing its survey of the sky and its mapping of our cosmos in infrared light. New exciting ...

Recommended for you

Can astronomy explain the biblical Star of Bethlehem?

Dec 24, 2014

Bright stars top Christmas trees in Christian homes around much of the world. The faithful sing about the Star of Wonder that guided the wise men to a manger in the little town of Bethlehem, where Jesus was ...

Hubbles spies the beautiful galaxy IC 335

Dec 24, 2014

This new NASA/ESA Hubble Space Telescope image shows the galaxy IC 335 in front of a backdrop of distant galaxies. IC 335 is part of a galaxy group containing three other galaxies, and located in the Fornax ...

Image: Multicoloured view of supernova remnant

Dec 22, 2014

Most celestial events unfold over thousands of years or more, making it impossible to follow their evolution on human timescales. Supernovas are notable exceptions, the powerful stellar explosions that make ...

Ultra-luminous X-ray sources in starburst galaxies

Dec 22, 2014

Ultra-luminous X-ray sources (ULXs) are point sources in the sky that are so bright in X-rays that each emits more radiation than a million suns emit at all wavelengths. ULXs are rare. Most galaxies (including ...

When a bright light fades

Dec 22, 2014

Astronomer Charles Telesco is primarily interested in the creation of planets and stars. So, when the University of Florida's giant telescope was pointed at a star undergoing a magnificent and explosive death, ...

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

omatumr
1 / 5 (4) Jul 07, 2010
The central issue is this:

Do new stars form:

a.) Out of the collapse of interstellar clouds of H and He?

b.) On the gravitational wells of preexisting objects?

With kind regards,
Oliver K. Manuel

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.