Author Topic: Diet of a dying star  (Read 722 times)

0 Members and 1 Guest are viewing this topic.

Online Buster's Uncle

  • Through art, I
  • Transcend
  • *
  • Posts: 45799
  • €258
  • View Inventory
  • Send /Gift
  • Someone thinks a Winrar is You!  Because there are times when people just need a cute puppy  Soft kitty, warm kitty, little ball of fur  
  • AC2 is my instrument, my heart, as I play my song.
  • Planet tales writer Smilie Artist Custom Faction Modder AC2 Wiki contributor Downloads Contributor
    • View Profile
    • My Custom Factions
    • Awards
Diet of a dying star
« on: March 09, 2012, 04:36:12 PM »
Quote
Diet of a dying star
Astronomers pinpoint what feeds a type of stellar explosion

 By Nadia Drake


 The explosion of the white dwarf star that produced supernova remnant SNR0509-67.5 (shown) may have been fueled by material sucked from another white dwarf, a recent study suggests.NASA, ESA, Hubble Heritage Team; J. Hughes/Rutgers Univ.
AUSTIN, Texas — Scientists are beginning to sort out the stellar ingredients that produce a type 1a supernova, a type of cosmic explosion that has been used to measure the universe’s accelerating expansion.

Two teams of researchers presented new data about these supernovas at the American Astronomical Society meeting on January 11. One team confirmed a long-held suspicion about the kind of star that explodes, and the second provided new evidence for what feeds that star until it bursts.

“This is a confirmation of a decades-old belief, namely that a type 1a supernova comes from the explosion of a carbon-oxygen white dwarf,” said Joshua Bloom, an astronomer at the University of California, Berkeley.

Bloom and his colleagues have been studying supernova 2011fe, the explosion that became visible 21 million light-years away, near the Pinwheel Galaxy, in August. When the PIRATE telescope in Majorca, Spain, wasn’t able to detect the supernova just hours after it exploded, Bloom’s team could set better limits on the size of the star that exploded. They concluded it must have been a white dwarf. When the dwarf — fed by a companion star — gets too heavy, a runaway thermonuclear reaction ignites in its core, producing a fireball bright enough to outshine surrounding galaxies.

But the culprit behind the dwarf’s mass gain is still a mystery: Although scientists know a companion star is feeding the dwarf, they don’t know what type of star that companion is.

Now, astronomers from Louisiana State University in Baton Rouge have answered that question for a centuries-old explosion. The team focused on a bubble-shaped remnant — the remains of a type 1a explosion that occurred 400 years ago — in the nearby galaxy the Large Magellanic Cloud. The remnant, called SNR0509-67.5, now spans 23 light years.

“It’s a beautifully symmetric remnant,” says graduate student Ashley Pagnotta, a coauthor on the team’s paper, which appears in the January 12 Nature. “We could find the center very precisely.”

The bubble’s center is the likely site of the explosion, and, since a large companion star would have survived the explosion and been flung outward at a predictable speed, the team calculated how far from that point a companion might have traveled over the last 400 years.

But they saw no stars within that region, suggesting that the star responsible for inflating the dwarf to explosive proportions was also destroyed. That result pointed to a second white dwarf as the companion, which instead of being chucked from the epicenter would have been shredded and destroyed.

“That’s not what we’d expected,” Pagnotta says. “This is the first supernova for which we’ve been able to make a definitive claim like that.”

Scientists have differing theories about what kind of star feeds a white dwarf. Some, like Pagnotta, suggest a second white dwarf; others think the companion must be a larger, main-sequence star like the sun — or bigger. Different starting ingredients might produce supernovas with different light curves and spectra — the output that lets scientists measure cosmological distances and calculate the rate of the universe’s expansion. 

Understanding type 1a “progenitor” systems is crucial for refining these measurements and seeing how the resulting explosions differ, says astronomer Peter Nugent of Lawrence Berkeley National Laboratory in California. “I think now we’re seeing really good evidence that supernovas have all the possible progenitors that people have looked at,” he says. “I don’t think it’ll screw things up. I think it’ll make things better.”
http://www.sciencenews.org/view/generic/id/337652/title/Diet_of_a_dying_star

 

* User

Welcome, Guest. Please login or register.
Did you miss your activation email?


Login with username, password and session length

Select language:

* Community poll

SMAC v.4 SMAX v.2 (or previous versions)
-=-
19 (7%)
XP Compatibility patch
-=-
9 (3%)
Gog version for Windows
-=-
78 (29%)
Scient (unofficial) patch
-=-
29 (10%)
Kyrub's latest patch
-=-
14 (5%)
Yitzi's latest patch
-=-
85 (32%)
AC for Mac
-=-
2 (0%)
AC for Linux
-=-
5 (1%)
Gog version for Mac
-=-
10 (3%)
No patch
-=-
13 (4%)
Total Members Voted: 264
AC2 Wiki Logo

* Random quote

Technological advance is an inherently iterative process. One does not simply take sand from the beach and produce a Dataprobe. We use crude tools to fashion better tools, and then our better tools to fashion more precise tools, and so on. Each minor refinement is a step in the process, and all of the steps must be taken.
~Chairman Sheng-ji Yang 'Looking God in the Eye'

* Select your theme

*