First direct evidence of early flattening as planets form

William Atkins
Thursday, 13 December 2007 18:58

Science - Space

The protostar is named L1157. It is about 800 light-years from the Sun within the constellation Cepheus. L1157 is an embryonic star, which is estimated to be only a few thousands of years old.

Such a discovery is very important to astronomers because L1157 is similar to our own Sun, and may provide a glimpse as to how the Sun first formed 4.5 billion years ago.

Assistant professor of astronomy Looney stated in the UIUC article, “We are seeing this object in the early stages of stellar birth. Eventually, the protostar will form into a star much like our sun, and the disk will form into planets and moons.”

Looney continues, “Some theories had predicted that envelopes flatten as they collapse onto their stars and surrounding planet-forming disks, but we hadn’t seen any strong evidence of this until now.”

Looney could only see the star from Earth by using the Spitzer Space Telescope which is operated by the NASA Jet Propulsion Laboratory (California Institute of Technology) because the orbiting telescope uses a very sensitive infrared camera to delve into the dust and record the structure within the cloud.

The abstract to Looney’s paper states, “Deep Spitzer IRAC images of L1157 reveal many of the details of the outflow and the circumstellar environment of this Class 0 protostar. In IRAC channel 4 (8 μm), there is a flattened structure seen in absorption against the background emission. The structure is perpendicular to the outflow and is extended to a diameter of ~2'. This structure is the first clear detection of a flattened circumstellar envelope or pseudodisk around a Class 0 protostar. Such a flattened morphology is an expected outcome for many collapse theories that include magnetic fields or rotation. We construct an extinction model for a power-law density profile, but we do not constrain the density power-law index.”

Images of the protostar and its planet-forming spinning but flattened cloud appear on the University of Illinois website at: http://www.news.uiuc.edu/news/07/1129cradle.html.