The story begins with this ground-based image of the Trifid Nebula, a broad bubble of gas and dust some 9,000 light-years from Earth. Near the center of this nearly circular nebula, and partially hidden by a dark band of dust, is a large star, many times more massive than our sun.
The star is the source of energy that fuels the nebula. Its ultraviolet light streams out, stripping electrons away from atoms. (A process called ionization.) It also heats the interstellar gas and dust that makes a nebula what it is -- a stellar womb.
"When this happens, the result is like a bomb going off," says Hester, an astronomer at Arizona State University. "The bubble of hot, high-pressure gas pushes its way outward through the 'dense' interstellar cloud from which the star formed."
The wrenching results are wounds in the natal cloud, which Hester likens to bursting bubbles in a mud pot at Yellowstone National Park. The massive star's radiation eats away at the walls of the wounds as an "advancing front of destruction moves outward from the star at a snail's pace -- only about 2,000 miles per hour. Even so, over the millions of years that the massive star lives, the bubble that it carves grows to be many light-years in size."
Sounds bad? Well, it is -- if you're trying to be a star. Read on.
The story of birth, death and murder continues with a detailed view of a region of the nebula taken by the Hubble Space Telescope. Hester and a team of astronomers released this image in early June, but it has been presented to the public again by the Space Telescope Science Institute.
The image shows a region of the nebula below the large central star.
This image reveals a stellar nursery at the head of the dense cloud. (The bulbous protrusion up and to the left with the two horns on its tip.) But while stars are being born in this colossal gaseous bulge, the very cradle in which they form is being destroyed by radiation from the massive star at the center of the nebula -- the original giver of life.
"When it comes to star formation, it looks like the influence of the massive star is both the beginning and the end of the story," Hester said.
But our story doesn't end there, for the images Hester's team produced have taught them much more, and we're still looking for evidence of this murder. So we move in for this closer look of the bulging cloud.
Emerging from it at the far top-left is what Hester calls a "stellar jet." It is evidence, he says, of the life within, pointing back to "a very young stellar object that lies buried within the cloud." Hester says the jet -- a thing rarely imaged in full like this -- is the exhaust gas of star formation, something like the contrail behind a commercial airliner. And (you're probably expecting this by now) it tells a whole story of its own.
Hester, never at a loss for metaphors, describes the jet as a ticker tape of history. Every 15 years or so, over the past 600 years, the jet has spat out knots of material, he says. And every few hundred years it wobbles, causing the corkscrew look seen in this closeup.
"The jet in the Trifid is a ticker tape telling the history of one particular young stellar object that is continuing to grow as its gravity draws in gas from its surroundings," Hester said. "But this particular ticker tape will not run for much longer."
Like a somber space doctor, Hester gives the jet 10,000 years or so to live. To understand the cause of death, you'll have to remember back to the beginning of our story: Seems the advancing front of energy from the massive star at the middle of the nebula is going to overrun and destroy the poor little forming star in our corkscrew jet.
If Hester is right, and if the massive central star is ever put on trial in the galactic courts, it might be useful to show a history of aggression. Hester can provide that, too, in the form of what he calls an evaporating gaseous globule (EGG).
The protrusion shown at left is the other "horn" in the bulging cloud above, the one that appears to point toward you and slightly over your head. Hester thinks this protrusion -- an evaporating gaseous globule -- has already survived a battle with the front of energy from the massive star at the middle of the nebula.
A galactic murder was likely committed as this battle appears to have claimed a fledgling star. At the tip of the stalk is a bright spot that Hester thinks might be reflected light from a young stellar object inside the stalk. And the even tinier spike at the very tip may be what astronomers call a "stellar micro-jet."
Jurors may be overwhelmed by all this, but here's why it's important: "If our interpretation is correct," Hester says, "the micro-jet may be the last gasp from a star that was cut off from its supply lines 100,000 years ago."
If you can imagine, there are more parts to this story. More revelations, more clues about star formation, nebula evolution, and the untimely death of stellar nurseries. And there is more yet to be learned as astronomers use the new research as a springboard for further study.
Hester sums up his life-and-death story this way: "The images seem to support a view in which the expanding region of hot ionized gas [powered by the massive, luminous star at the center of the nebula] first causes clumps of gas to contract to form stars and then, a short time later, overruns those clumps of forming stars, shutting the whole process down."
Other researchers on the project included Paul Scowen of Arizona State University, Karl Stapelfeldt of NASA's Jet Propulsion Laboratory, and John Krist of the Space Telescope Science Institute. The scientists collaborated with the HST Wide Field Planetary Camera 2 Investigation Definition Team.
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