This year is off to an auspicious start. Within 24 hours astronomers meeting in Pasadena announced the discovery of a galaxy in formation about 12 billion light years away, and closer to home the discovery of a disk of gas orbiting a young star that looks like what they suspect our solar system looked like at its birth.
Astronomers have long conjectured about the origins of cosmic phenomena. But only in the second half of the 20th Century has theory and technology cooperated to enable the verification of many of these ideas.
Astronomers work in two ways. In some instances they have predicted the existence of objects such as the planet, Pluto, from knowledge of the way matter in space obeys Kepler's laws. Alternatively, as technology has allowed us to probe more deeply into space, phenomena such as quasars have been discovered, which astronomers have then had to explain.
Anneila Sargent at Caltech and Steven Beckwith at Cornell were actively looking for an embryonic solar system. If only 5% of all stars have planets, they suggest, that is plenty of places where intelligent life is likely to have evolved. The odds are high, but until now no other solar system has been seen. Planets do not emit light but only reflect light. Early in its evolution, however, a developing solar system still in a cloud of dust would be visible. They began looking for a star about the age that our sun, Sol, was 4 billion years ago when theory suggests a similar disk orbited the sun. Only half a dozen possibilities had been scanned before they hit on HL Tauri in the constellation Taurus. If it was so easy, Sargent and Beckwith reason, it must be because such embryonic systems are commonplace. If its evolution continues unchecked, in 4 billion years HL Tauri may boast an Earthlike satellite.
The team from Berkeley, Arizona and Boston that reported the discovery of the evolving galaxy were searching for the birth of a galaxy but they did expect to find one in such an embryonic state where they found 3C 326.1. Its position suggests that the origin of the universe was a more gradual process than is now believed. The proto-galaxy is comprised of a cloud of ionized hydrogen molecules three times the size of the Milky Way galaxy and it seems to be producing thousands of new stars a year. The gas is dazzlingly bright compared to the dimmer glow from the still rapidly forming stars.
These "birth processes" are new to astronomy. Heretofore documenting the end point in stellar evolution has absorbed more scientific attention. We are familiar with the death throes of stars in several forms. There is the phenomena of supernovae that leave in their wake neutron stars. There are white dwarfs that fade slowly into obscurity, and there are the mysterious black holes--objects so dense that their gravity sucks in everything that approaches, including light, so that we don't know what lies inside.
But whether the search turns up exactly what the astronomers predicted, like the orbiting disk in Taurus or discovers that what they were looking for is not quite what they expected, as with the evolving galaxy, there is surely a shift of focus from the way things end in space to the way they begin.
Not that astronomers had avoided documenting beginnings, but while stars seem to die with a dramatic burst of energy, the births of solar systems and galaxies are more subtle events.
We owe their detection to a host of technological innovations. In the past decade optical telescopes have begun to work in conjunction with new instruments that see beyond the visible spectrum. Arrays of radio telescopes, including Caltech's facility in the Owens' Valley, complement information received with the infrared equipment on Mauna Kea in Hawaii. Because wavelengths shift as objects race through space, it is necessary to be able to trace them from one spectrum to another.
The developing galaxy was discovered through radio waves, then found by optical telescopes using extremely sensitive electronic light detectors. The developing solar system was noticed first in the infra-red and then examined in greater detail with radio telescopes. Neither discovery would have been possible even five years ago.
Both allow us to use astronomy as a time machine. They provide a mirror to our past.