In orbit less than two months, a telescope called the Infrared Astronomical Satellite (IRAS) has discovered stars being born, the hints of stars in death throes and as many as 20 distant galaxies too small to have been mapped before.
This telescope is so sensitive that it can focus on an object with temperatures far below the equivalent of freezing on Earth. In contrast, optical telescopes see only objects whose temperatures are above 10,000 degrees Fahrenheit, hot enough to make them shine.
"Before IRAS went into orbit, astronomers had measured 20 small galaxies outside the Milky Way," Cornell University's Dr. James Houck said recently by telephone from California's Jet Propulsion Laboratory. "In 12 hours of operation with this satellite, we doubled that number."
Houck is one of 18 astronomers who make up the three-nation IRAS science team. The telescope was built in the United States, the spacecraft housing it in the Netherlands. The satellite's flight is tracked in Great Britain.
In a single minute of observation, the satellite's 22.4-inch-wide telescope gathered more information about the Large Magellanic Cloud--the galaxy nearest our own Milky Way--than had ever been collected by telescopes on the ground. Within the Magellanic Cloud, the IRAS has found dozens of huge dust clouds--too cool to be observed by optical telescopes--where stars are being born, an event that happens in the Milky Way once or twice a year.
"At the center of some of these clouds, which measure two or three light years in size, there are processes going on that are in an advanced stage of giving birth to stars," said Houck. "You can tell this by the temperatures we see at the cloud's center, which are much warmer than the surrounding cloud."
What the IRAS has detected since its Jan. 25 launch are objects in the cloud centers emitting heat the equivalent of room temperature, almost a sure sign of embryonic stars growing warmer all the time as they struggle to develop.
Houck said that the satellite also had seen hints of stars exhausting their nuclear fuel, when they lose large clouds of dust. The shell of this lost dust absorbs the dying star's visible light so it cannot be seen by optical telescopes. But the IRAS can pick up its telltale dying temperature.
One of IRAS' most striking accomplishments was the sharp image it got of a galaxy so small and so far away that optical astronomers have never even given it a name. They call it by its numbered position in the sky 300 million light-years from Earth: MCC Plus 1, Minus 11-013.
"We were quite surprised to be able to see so far and so clearly," Houck said. "We now think we'll be able to spot small galaxies out to about 900 million light-years, where galaxies have never even been seen before." A light-year is the distance light travels in a year, about 6 trillion miles.
The biggest surprise of all about the $80 million satellite is that, in Houck's words, "The satellite is working better than we had hoped it would even in our most secret moments," seeing cooler objects and in far greater detail than astronomers thought it could.
In the 12 months that scientists expect it to last, IRAS will survey 95 percent of the sky in the infrared, a feat never even attempted from the ground. It will also do detailed observations of the Andromeda galaxy, the Orion Nebula, the galaxy clusters in the Constellation Virgo and the Milky Way's mysterious center, which is largely hidden from optical telescopes by stars and dust.
"These are the regions where stars are being born and are dying," Houck explained. "This is where our infrared telescope can work the best." Infrared light waves are longer than those in the visible spectrum but shorter than radio waves.
Even the satellite's projected life is exceeding expectations. Liquid helium cools the telescope to 2.5 degrees above absolute zero to eliminate any stray heat that may confuse the stellar images it receives. The helium has been used up so slowly that scientists have extended its expected lifetime by 50 percent.