Doom for Hubble's iconic pillars

From: http://news.bbc.co.uk/2/hi/science/nature/6246333.stm

Jan 9, 2007

The three iconic columns of gas and dust pictured in space by the Hubble Telescope in 1995 may have met their end, the US space agency says.

Hubble's image, dubbed the "pillars of creation", has featured in countless papers, magazines and posters.

Now, new data shows the pillars being scorched by an exploding star - and a shockwave has probably torn them apart.

But because of the time taken for light to reach Earth, we will not see their final destruction for 1,000 years.

"In the Hubble pictures, the pillars seem to be compact and solid; but in fact they are not," said Nicolas Flagey, from France's Institut d'Astrophysique Spatiale.

"Only the top of the pillars and some parts within are dense enough to resist the shock. But the rest is going to be blown away by the shockwave," he told BBC News.

Hubble inspiration

The pillars are actually dark columns of cool interstellar hydrogen gas and dust that serve as incubators for new stars.

They are part of the Eagle Nebula (also called M16), a star-forming region 6,000 light-years from Earth in the constellation Serpens.

Mr Flagey, a PhD student who helped make the latest discovery, presented his findings here at a meeting of the American Astronomical Society.

He says he was inspired to study astrophysics after seeing Hubble's image of the pillars on the cover of a French magazine more than a decade ago.

So he was surprised to be offered the chance to work on the Eagle Nebula during a six-month attachment to the Spitzer Science Center in California.

The centre operates Nasa's Spitzer Space Telescope, which took new infrared pictures of a shell-shaped cloud of hot dust close to the pillars. The shell is being heated by an exploding star.

Using the telescope data, Dr Flagey and colleagues were able to measure the temperature of the dust and match it to a supernova (exploding star) event.

Back in time

"Something else besides starlight is heating this dust," said Dr Alberto Noriega-Crespo, Mr Flagey's advisor at the Spitzer Science Center.

Astronomers had long predicted that a supernova blast would spell the end for the popular pillars.

"We know that there are some massive stars inside the Eagle Nebula. The fate of these stars is to explode as supernovas," Mr Flagey told BBC News.

"So it was not completely unexpected that one of these has already exploded and has produced the shockwave that is heating the gas and dust."

The star is thought to have exploded around 8,000-9,000 years ago.

Since light from the Eagle Nebula takes 7,000 years to reach us, the stellar explosion would have appeared as an oddly bright star in our skies about 1,000 to 2,000 years ago.

The astronomers estimate that the blast would have spread outward and toppled the three pillars around 6,000 years ago. This means that we will not be able to see the destruction for another 1,000 years.

When the mighty pillars are seen to crumble, gas and dust will be blown away, exposing newborn stars forming inside. A new generation of stars might spring up from the dusty wreckage.

Despite being inspired to pursue his current career by Hubble's iconic picture of the structures, Mr Flagey said he was not disappointed to discover that they are - in all likelihood - already gone.

"I will not be here to see it destroyed," he said, "there are plenty of other regions like this. So I'm not sad."