starbabies_cluster_000807 Scientists have a whole new perspective on the youngest cluster of massive stars yet detected in the
Milky Way Galaxy. Imagine a bunch of big, fat, feverish babies who can cry across the galaxy while hiding out in the womb. That's how astrophysicist Peter Conti describes the stars.
The 1 million-year-old cluster, known as W 49, is a huge gas cloud surrounding a batch of hot, heavy
stars that emit radio waves but are hidden by individual shrouds of gas and dust."You are looking at the cocoons. You dont see the babies yet," said Conti, a professor at the University of Colorado at Boulder. "They are in their individual wombs and the whole thing (W 49) is the nursery."
W 49 a glowing cloud of ionized hydrogen known as a giant H 2 region was studied by Conti and astrophysicists Robert Blum of the Cerro Tololo Inter-American Observatory in Chile and Augusto Damineli of the University of Sao Paulo, Brazil.
Conti was scheduled to present the findings August 10 during the International Astronomical Union meeting in Manchester, England.
Hot, young stars are visible in this infrared (IR) telescope image of massive star cluster W 31. But they hide without detectable IR emissions in younger clusters like W 49.
Conti said W 49 is among the brightest H 2 clouds in the Milky Way. The young stars within W 49 are "type O" stars the hottest and most massive in our
galaxy. Each is 15 to 100 times more massive than our sun. Their surface temperature is about 90,000 degrees Fahrenheit (50,000 degrees Celsius), Conti said.Blinded by the dust
There is too much dust between
Earth and W 49 some 23,000 light-years distant (135,000 trillion miles) for the stars to be seen by optical telescopes. But for about a decade, radio-telescopic images have indicated W 49 harbors type O stars.Conti, Blum and Damineli made near-infrared pictures of eight giant H 2 clouds using 13-foot (4-meter) and 5-foot (1.5-meter) telescopes at Cerro Tololo. In seven of the clouds, central clusters of type O stars were visible at infrared wavelengths. But type O stars in the center of W 49 were not.
That means the type O stars in the middle of W 49 are at a younger stage of development, still shrouded in dust and gas so thick that not even near-infrared telescopes can detect their heat, Conti said.
"Its a
star cluster that has not yet revealed itself because its highly obscured," agreed Jack Welch, an astronomer at the University of California, Berkeley. "Its a cluster at an earlier stage" than seen in other H 2 gas clouds.Young stars
Type O stars live only 5 million to 10 million years compared with the up to 10 billion-year lifetimes of less massive stars like our sun. Given their early stage of development, the shrouded type O stars in W 49 must be younger than 1 million years old, Conti said.
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The W 49 gas cloud not only contains 10 to 20 shrouded type O stars near its center, but up to another 80 to 90 slightly older, baby type O stars that apparently are located near the gas clouds edges. Unlike the O stars at W 49s center, they are visible to infrared telescopes. They "could just be getting out of the nursery," Conti said.
The W 49 gas cloud likely also includes thousands of smaller, less luminous stars undetected by any telescopes, Conti said.
Conti said W 49s young type O stars, swaddled in individual gas-and-dust shrouds, resemble smaller glowing gas clouds known as "ultra-compact H 2 regions" seen elsewhere in the galaxy by radio telescopes.
Giant H 2 clouds like W 49 are 5 to 10 light-years wide (29 trillion to 59 trillion miles), while ultra-compact H 2 clouds are 10 to 100 times smaller, Conti said.
"Nobody used the word cluster. What is new is the realization that W49is the only giant HII gas cloud that has O stars at this young a stage."
He said the swaddled baby stars at the center of W 49 are "a cluster of ultra-compact H 2 regions. They are still in the earliest stages of birth."
W 49 first was discovered as a radio emitter in the 1950s, Conti said. About a decade ago, radio astronomers realized the objects emitting radio waves from W 49 were ultra-compact H 2 gas-and-dust clouds powered by type O stars.
"But nobody put together what this meant," Conti said. "Nobody used the word cluster. What is new is the realization that W 49 is the only giant H 2 gas cloud that has O stars at this young a stage. In all the others we look at, we see the stars out of their cocoons."
Meanwhile, other scientists reported on the latest observations of five perhaps still-younger massive star clusters discovered in 1999 outside the Milky Way, some 32 million light-years (190 million trillion miles) away in Galaxy
Henize 2-10. Those clusters are believed to be only 500,000 years old."Thats as much as a guess as under 1 million years" for the massive star clusters of W 49, Conti said.
Meanwhile, Welch said he might have seen something even younger on one side of the W 49 gas cloud -- a "hot core," which Welch described as "a small, dense clump of gas thats extremely luminous in the infrared and radio. There has to be a star in there, probably a couple of O stars" even younger than those shrouded in the center of W 49.
"This is 100,000 years or something, or maybe even a few tens of thousands of years," Welch said.
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