Heart of the Milky Way

Stars move at tremendous speeds in the galaxy's core

By BBC News Online science editor Dr David Whitehouse

The first scientific observations from the Gemini North telescope in Hawaii are providing a dramatic glimpse into the core of our galaxy.

The pioneering image shows a star ploughing through a gas and dust cloud, just three light-years from the centre of the Milky Way.

The star creates a shockwave as it goes through the cloud. Astronomers believe the discovery could alter current understanding of the galactic core.

"There has been a buzz of increased interest by astronomers," said Professor Andrea Ghez of the University of California, at Los Angeles. "Gemini has demonstrated many unique capabilities for studying our galaxy and beyond.

"It is a remarkable new tool for exploring the Universe," she added.

Shock wave

The peculiar star, catalogued as IRS8, was only an ill-defined smudge until Gemini looked at it. Now, the telescope's advanced optic system has revealed that IRS8 is a star ploughing through a poorly understood gas and dust cloud near the galactic centre.

A star creates a bow shockwave as it streams through a gas cloud

Moving through the cloud, the star creates a bow shockwave, similar to the wave that forms in front of a boat as it travels through water.

It is a discovery that could alter our understanding of the centre of our galaxy once astronomers find out how the star and gas cloud are moving relative to each other.

By studying the properties of the gas cloud and the conditions surrounding the star, astronomers will have a new way to probe the intense conditions near the centre of the Milky Way.

Science testing

The centre of our galaxy is a strange and dramatic place. Rotating gas rings can be seen there as well as stars travelling at great speeds around a massive black hole.

"Never before have we seen such a large area of the galactic centre this clearly," said Dr François Rigaut of the Gemini Observatory.

The Gemini North telescope is nearing completion

The image was obtained over several nights in July and August 2000 as part of the science-testing period as the Gemini North telescope nears completion on Mauna Kea in Hawaii.

The Gemini 8-metre Observatory Project is a multinational collaboration that will provide twin telescopes, one in the Northern Hemisphere and one in the South.

Gemini North is nearing scientific operations early in 2001. Gemini South will follow about six months later.

Trickle of light

"This is the first scientific data to be released to the astronomical community by the Gemini Observatory," said Director Dr Matt Mountain. "To be able to release such a spectacular image and data set shows the tremendous potential of these telescopes."

The remarkable sharpness of the image is due to a technology called adaptive optics that corrects for distortions to starlight introduced by turbulence in the Earth's atmosphere.

In addition, observing the galactic centre is especially difficult because its light must travel through thousands of light-years of gas and dust before it reaches us.

Only a small portion of the light ever gets to our planet and most is in the infrared region of the spectrum. The Gemini Observatory has been designed to be sensitive to this trickle of infrared radiation.