Lifting a dusty veil to clear IRAS' view.

Lifting a dusty veil to clear IRAS' view

Observations made in 1983 by the Infrared Astronomy Satellite (IRAS) during its 10-month mission have helped astronomers map emissions of infrared radiation (heat) from distant interstellar and interplanetary dust clouds. But researchers have had to settle for a relatively fuzzy picture, because a thin haze of dust around Earth obscures distant and faint emissions. Now astronomers have employed computer tricks to effectively lift that veil of dust clouding IRAS' vision of our galaxy.

In the Sept. 15 MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Michael Rowan-Robinson and his colleagues from Queen Mary and Westfield College in London calculated the average size of dust particles between Earth and a belt of asteroids that orbit the sun between Mars and Jupiter. This dust cloud contains remnants of asteroid collisions that occurred millions of years ago. Drawn by gravity, the cloud slowly spirals toward the sun, enveloping Earth along the way.

The new calculations enabled the team to deduce the interplanetary dust particles' contribution to the infrared energy recorded by IRAS -- and to subtract it from the data used to compile IRAS' images.

An example of this computer processing, for emissions in the 60-micron wavelength (above), reveals a large, faint S-shaped curve. This wave-like feature -- which traces the path of the solar system as it rises above and falls below the Milky Way's plane (dark horizontal band) over nearly a year -- markes the dusty debris from relatively recent asteroid collisions, shown here in greater detail than ever before. Below the lower edge of the dark band are emissions from the Orion constellation, just right of center, and the Pleiades cluster, just left of center.