Scientists witness start of star's explosive death

[Gfted1]

May 22, 4:21 AM (ET)

 

By SETH BORENSTEIN

 

WASHINGTON (AP) - In a stroke of cosmic luck, astronomers for the first time witnessed the start of one of the universe's most fiery events: the end of a star's life as it exploded into a supernova.

 

On Jan. 9, astronomers used a NASA X-ray satellite to spy on a star already well into its death throes, when another star in the same galaxy started to explode. The outburst was 100 billion times brighter than Earth's sun. The scientists were able to get several ground-based telescopes to join in the early viewing and the first results were published in Thursday's issue of the journal Nature.

 

"It's like winning the astronomy lottery," said lead author Alicia Soderberg, an astrophysics researcher at Princeton University. "We caught the whole thing from start-to-finish on tape."

 

Another scientist, University of California at Berkeley astronomy professor Alex Filippenko, called it a "very special moment because this is the birth, in a sense, of the death of a star."

 

 

And what a death blast it is.

 

"As much energy is released in one second by the death of a star as by all of the other stars you can see in the visible universe," Filippenko said.

 

Less than 1 percent of the stars in the universe will die this way, in a supernova, said Filippenko, who has written a separate paper awaiting publication. Most stars, including our sun, will get stronger and then slowly fade into white dwarfs, what Filippenko likes to call "retired stars," which produce little energy.

 

The first explosion of this supernova can only be seen in the X-ray wave length. It was spotted by NASA's Swift satellite, which looks at X-rays, and happened to be focused on the right region, Soderberg said. The blast was so bright it flooded the satellite's instrument, giving it a picture akin to "pointing your digital camera at the sun," she said.

 

The chances of two simultaneous supernovae explosions so close to each other is maybe 1 in 10,000, Soderberg said. The odds of looking at them at the right time with the right telescope are, well, astronomical.

 

Add to that the serendipity of the Berkeley team viewing the same region with an optical light telescope. It took pictures of the star about three hours before it exploded.

 

This new glimpse of a supernova seems to confirm decades-old theories on how stars explode and die, not providing many surprises, scientists said. That makes the findings "a cool thing," but not one that fundamentally changes astrophysics, said University of California, Santa Cruz astrophysicist Stan Woosley, who wasn't part of the research.

 

The galaxy with the dual explosions is a run-of-the-mill cluster of stars, not too close and not too far from the Milky Way in cosmic terms, Soderberg said. The galaxy, NGC2770, is about 100 million light years away. One light year is 5.9 trillion miles.

 

The star that exploded was only about 10 million years old. It was the same size in diameter as the sun, but about 10 to 20 times more dense.

 

The death of this star went through stages, with the core getting heavier in successive nuclear reactions and atomic particles being shed out toward the cosmos, Filippenko said. It started out in its normal life with hydrogen being converted to helium, which is what is happening in our sun. The helium then converts to oxygen and carbon, and into heavier and heavier elements until it turns into iron.

 

That's when the star core becomes so heavy it collapses in on itself, and the supernova starts with a shock wave of particles piercing through the shell of the star, which is what the Soderberg team captured on x-rays.

 

People at home can simulate how this shockwave works, Filippenko said.

 

Take a basketball and a tennis ball, get about five feet above the ground and rest the tennis ball on top of the basketball. Drop them together and the tennis ball will soar on the bounce. The basketball is the collapsing core and the tennis ball is the shockwave that was seen by astronomers, he said.

[Morgoth]

Pics or it didn't happen.

[Tale]

BAWWW

 

Edit: Also, I'm with Morgoth. I presume NASA will be making the pictures public. Will they be doing it on their site?

Edited May 23, 2008 by Tale

[SteveThaiBinh]

I heard Soderberg interviewed on the radio last night, and she sounded thrilled that she'd seen something so amazing. Congratulations to her team on their luck.

[Xard]

oh c'mon that's not fair, you didn't give me time for comeback, I was in sauna while you pruned this

[random n00b]

Edit: Also, I'm with Morgoth. I presume NASA will be making the pictures public. Will they be doing it on their site?

The article says it was only captured in x-rays. If they make any pics public, they'll be the artificially colored kind. Also, it says the sat was "blinded" at first, which may limit the amount of material available.

 

It'd be cool to have some pics, tho.

[WILL THE ALMIGHTY]

They managed to get more telescopes to view it, so there's a good chance we'll get a non-X-Ray version as well.

[Walsingham]

I'd like to be completely tasteless, and say that I genuinely thought for a second that this was about Kurt Cobain.

[Gorth]

The star that exploded was only about 10 million years old. It was the same size in diameter as the sun, but about 10 to 20 times more dense.

Oww... poor young star. It hadn't even reached teenage years yet as far as stars go. Heck, not even a starlet, Just a little toddler

[Dark_Raven]

In a few thousands of years we can watch our star go super nova.

Edited May 25, 2008 by Dark_Raven

[Xard]

Sun is too small star for that, it won' go supernova

[Humodour]

In a few thousands of years we can watch our star go super nova.

 

Nah, the sun will become a red giant in 5 to 6 billion years (c.f. Earth and Sol are 4.56 billion years old while life is about 4 billion years old).

 

Meanwhile, by about 0.9 billion years time, the Sun's thermal expansion leading up to red giant phase will have incinerated most of Earth's atmosphere and annihilated all life on earth.

 

After a red giant, Sol will become a nebula, and then a white dwarf and finally a black dwarf.

 

Of course, no black dwarfs have been observed, because the universe is relatively young (13.7 billion years old) so none have formed yet. Even so, it is unknown exactly how long black dwarfs take to form... it depends on whether or not protons decay and what dark matter is (i.e. WIMPs).

[Xard]

Just out of curiosity doesn't some people consider them as possible sources for black holes?

[Humodour]

What? Black dwarfs? Black dwarfs should be extremely hard to detect (because, like planets and black holes, they emit little to no light), so gravitational analysis is probably the best method. But they aren't black holes - the gravity pulls would be noticeably different. Further, black dwarfs can't possibly exist yet - all the white dwarfs in existence are still too hot.

 

BTW, did you know that when you are within a neutron star's gravity, you must reach 50% the speed of light to escape, or be accelerated so fast to the core that you are immediately converted into pure neutrons?

[Xard]

What? Black dwarfs? Black dwarfs should be extremely hard to detect (because, like planets and black holes, they emit little to no light), so gravitational analysis is probably the best method. But they aren't black holes - the gravity pulls would be noticeably different. Further, black dwarfs can't possibly exist yet - all the white dwarfs in existence are still too hot.

 

BTW, did you know that when you are within a neutron star's gravity, you must reach 50% the speed of light to escape, or be accelerated so fast to the core that you are immediately converted into pure neutrons?

 

You and your physics

 

Which translates to no, I didn't know that

 

Yeah, I didn't think so too but some theory of birth of black holes involved stars somehow - propably bigger ones.

 

edit: Yay, I remembered at least partially right

 

Death of a Massive Star

 

Massive stars burn brighter and perish more dramatically than most. When a star ten times more massive than Sun exhaust the helium in the core, the nuclear burning cycle continues. The carbon core contracts further and reaches high enough temperature to burn carbon to oxygen, neon, silicon, sulfur and finally to iron. Iron is the most stable form of nuclear matter and there is no energy to be gained by burning it to any heavier element. Without any source of heat to balance the gravity, the iron core collapses until it reaches nuclear densities. This high density core resists further collapse causing the infalling matter to "bounce" off the core. This sudden core bounce (which includes the release of energetic neutrinos from the core) produces a supernova explosion. For one brilliant month, a single star burns brighter than a whole galaxy of a billion stars. Supernova explosions inject carbon, oxygen, silicon and other heavy elements up to iron into interstellar space. They are also the site where most of the elements heavier than iron are produced. This heavy element enriched gas will be incorporated into future generations of stars and planets. Without supernova, the fiery death of massive stars, there would be no carbon, oxygen or other elements that make life possible.

 

The fate of the hot neutron core depends upon the mass of the progenitor star. If the progenitor mass is around ten times the mass of the Sun, the neutron star core will cool to form a neutron star. Neutron stars are potentially detectable as "pulsars", powerful beacons of radio emission. If the progenitor mass is larger, then the resultant core is so heavy that not even nuclear forces can resist the pull of gravity and the core collapses to form a black hole.

 

Click

Edited May 25, 2008 by Xard

[Humodour]

Ohhh yeah, sorry. That's true.

 

Black holes form when stars are too massive. But not all massive stars form black holes - some do, some don't, It depends on a bunch of factors like elemental composition, temperature, density, etc at the time of 'death', meaning that some large stars form neutrons while some smaller ones form black holes.

 

Other fates for supernovas are quark stars and neutron stars.

 

Even white dwarfs can form supernovas if they bump into other stars (e.g. a binary system of white dwarfs).

 

Black holes eventually explode into Hawking radiation when they leak away too much matter for their gravitational pull to hold the rest together (I think it's because of virtual antimatter interaction with virtual normal matter on the event horizon of the black hole - the black hole sucks up one of the virtual particles but the other escapes, meaning the black hole 'gives off' matter... but this is only a problem when cosmic background radiation loses enough energy, like a bazigillion years from now, ok maybe a googol). This is why micro black holes on Earth won't suddenly swallow it up - they'll explode harmlessly almost immediately. Well, supposedly... a lot of the theory at that level is incomplete. For example, electrons bear a striking resemblance to micro black holes.