Hubble's 'Pillars of Creation' are fading

The original image was taken at visible wavelengths

By Dr David Whitehouse BBC News Online science editor

It is the most famous picture ever taken by the Hubble Space Telescope. Released in 1995, the image - dubbed the Pillars of Creation - has become an icon for the grandeur and beauty of the cosmos.

When you view [the pillars] in the infrared, you get a different picture

Prof Rodger Thompson

The awesome pillars are several light-years long, big enough to stretch from our Sun to its nearest stellar neighbour.

The Eagle Nebula, as it is known, was described at the time as a region of intense star formation; you can see bright stars sprinkled across the image and embedded in the vast columns of gas and dust.

Now, however, the latest observations (looking at wavelengths outside the optical region of the spectrum) suggest the Eagle is anything but a stellar breeding ground - it is, in fact, producing very few stars and fading fast.

A different picture

Professor Rodger Thompson, of the University of Arizona, US, has been observing the Eagle Nebula using the Nicmos (Near-infrared camera and multi-object spectrometer) on the Hubble Space Telescope.

He told BBC News Online: "They look like very dark, dense columns of gas and dust. But when you view them in the infrared, you get a different picture."

The Nicmos view tells a different story

The infrared images show that the Pillars of Creation do not contain a lot of material and that star formation is coming to an end. The only place where stars are being born is at the very tips of the pillars.

The nebula - the word comes from the Latin for cloud - has been influenced by a cluster of very bright, type O stars nearby. They have shaped and illuminated the nebula (and initiated star formation within it) whilst at the same time working to destroy it.

The O stars, much larger and far more luminous than our Sun, would have formed quickly when the nebula was young. Although such stars burn for only a few million years at most, their influence on the development of the nebula has been profound.

Just a handful

The radiation and stellar winds from the O stars have evaporated much of the material from the nebula.

In some parts of the nebula, however, the outpourings of the O stars have met resistance. Unable to evaporate very dense regions of dust and gas, these outpourings have instead compressed material, triggering a burst of star formation.

Protected from the O stars' ravages behind a dust "capstone", huge pillars have reached out into space.

"The optical picture alone is very confusing," Professor Thompson told BBC News Online. "You need to look in the infrared to understand what is going on and what happened in the past."

Although the tips of the pillars do act as a stellar nursery, astronomers now think even there not many stars are being formed - certainly no more than a handful.

Undiminished beauty

"In the tips, we can see five or six places where stars are forming. But we don't know if they are multiple or single stars or even if they are reflections from dust clouds," said Professor Thompson.

The Orion Nebula really is bursting forth with stars

"The next step is to use the Chandra X-ray telescope to home in on the young stars in the Eagle Nebula because they radiate a lot of X-rays. That way we can take a census of what is exactly in these pillars."

There is no denying the beauty of the original Hubble image, but for some, knowing that the pillars will fade in a million years or so means the picture has lost a little of its appeal.

This revised analysis of the Eagle Nebula is in stark contrast to what we now know about star formation in the mighty nebula in Orion.

Evidence gathered in recent years has shown it to be an even more vigorous site of starbirth than had been thought, with tens of thousands of stars being born.