Better than the Hubble

'Clearest' images taken of space

By Pallab Ghosh Science correspondent, BBC News

The Cat's Eye Nebula as imaged conventionally by the Palomar 200in telescope (l) and with the Lucky Camera (r)

A team of astronomers from the US and the UK has obtained some of the clearest pictures of space ever taken.

They were acquired using a new "adaptive optics" system which sharpens pictures taken from the Mount Palomar Observatory in California.

The images are twice as sharp as those from Hubble Space Telescope.

The new system, dubbed "Lucky", is the result of work by a team from Cambridge University and the California Institute of Technology (Caltech).

Our techniques can do very well when the telescope is bigger than Hubble and has intrinsically better resolution Craig Mackay, University of Cambridge

Pictures taken by Hubble are normally much better than images from ground-based telescopes because the Earth's atmosphere has a distorting effect.

The Lucky camera overcomes this problem in two ways.

First, it uses one of the most sensitive light-detection systems developed to date. This comprises a chip that has very low electrical noise and so can see much greater detail.

Secondly, the software system is able to distinguish when the atmospheric distortion starts and stops.

The Globular cluster M13 as imaged conventionally by the Palomar 200in telescope (l) and with the Lucky camera (r)

The inventor of the system, Dr Craig Mackay of the Institute of Astronomy in Cambridge, says it is rather like looking at an object through a heat haze.

"The object is distorted by the haze most of the time," he explained, "but every now and again there are moments when the haze drops and you can see it very clearly."

The Lucky system gathers together all the clear pictures and throws out the distortions to produce images that Dr Mackay believes are the clearest ever images from the ground.

"The images space telescopes produce are of extremely high quality but they are limited to the size of the telescope," Dr Mackay added.

"Our techniques can do very well when the telescope is bigger than Hubble and has intrinsically better resolution."

Two images have been published to date. One is of the globular star cluster M13 which is at a distance of 25,000 light-years.

Stars that are as little as one light-day apart can be differentiated in the picture.

The other shows very fine detail in the Cat's Eye Nebula (NGC6543).

This is another potentially big deal. Usually, adaptive optics in astronomy mean some sort of physical correction, like manipulating tiny sections of a reflecting telescope's mirror to keep the image of a star and the image of a guide spot in the upper atmosphere from a ground-based laser synchronized. This new system uses software to choose "still" images recorded by a very sensitive and quiet CCD and throw out the noisy ones. Imagine if both techniques could be used simultaneously.