[extropy-chat] cosmic dust in the news

[spike]

http://www.cnn.com/2006/TECH/space/07/27/dead.star/index.html


New life in dead star
By Ker Than
SPACE.com


Thursday, July 27, 2006; Posted: 9:55 a.m. EDT (13:55 GMT) 


Telescopic images show changes in Supernova 1987A.  


(SPACE.com) -- Newly detected dust found around the burst remains of a dead
star could help reveal how planets and stars formed and how life began.

About 160,000 years ago, a star 20 times more massive than our sun erupted
in a fiery explosion called a supernova. The star was located in the Large
Magellanic Cloud, a nearby dwarf galaxy. In 1987, the first light from that
catastrophic event reached Earth and for several months, the supernova,
dubbed SN 1987A, blazed as brightly as 100 million suns before fading again.

Now, nearly two decades later, astronomers have detected dust particles
around the supernova that they think formed before the star exploded. The
new finding is the first evidence that star dust can survive a supernova
explosion. It is also providing a rare glimpse into a process called
"sputtering," in which dust is eroded by interactions with superheated gas.

"Supernova 1987A is changing right before our eyes," said Eli Dwek, a cosmic
dust expert at NASA Goddard Space Flight Center in Maryland who was involved
in the finding. "What we are seeing is a milestone in the evolution of a
supernova."

Cosmic building blocks
Finer than grains of beach sand, stellar dust is a constant source of
frustration for astronomers because it can obscure observations from distant
stars. Yet the troublesome dust is also a prime ingredient in the
construction of planets and of all living things. The dust is made in the
fiery furnaces of stars as they burn and is scattered across space either by
stellar winds or by supernova explosions.

Despite its importance, scientists still know very little about star dust.
How much dust does a star produce throughout its lifetime? How much survives
a star's death? And how do rings of dust coalesce to form stars and planets?

1987A's newly detected stardust, found using an infrared telescope at the
Gemini South Observatory in Chile, could help astronomers answer these
questions. The dust particles are intermixed with superheated, X-ray
emitting gas and found within an equatorial ring around SN 1987A. About a
light-year across, the ring of gas and dust is expanding very slowly.

This suggests that the ring was created about 600,000 years before the star
exploded, the researchers say. It is therefore unlikely that the ring was
created by a supernova blast during the star's death, but rather by stellar
winds when the star was still alive.

Made visible
The ring of dust and gas remained invisible for nearly twenty years until
shockwaves from the supernova blast caught up with it. As the shockwaves
expanded, they passed through the ring, heating up its gas and normally cool
dust until they glowed in the infrared.

"This much was expected," said study team member Patrice Bouchet of the
Observatoire de Paris. "The collision between the ejecta of supernova 1987A
and the equatorial ring was predicted to occur sometime in the interval of
1995 to 2007, and it is now underway."

What was surprising, however, was the composition of the dust, which
followup observations with NASA's Spitzer Space Telescope revealed to be
almost pure silicate. Also, far less dust than expected was detected. A star
as massive as the one that created SN 1987A was thought to produce much more
dust.

The dearth of dust could mean that shockwaves from the supernova blast
destroyed more dust than originally thought. This could have broad
implications for determining dust origins throughout the universe if
confirmed, the researchers say.

A spate of new infrared, optical and X-ray observations of SN 1987A are now
planned to follow up on the new findings.