Astronomers Discover Youngest Solar System Yet

An international group of astronomers using the Submillimeter Array and the Combined Array for Millimeter-Wave Astronomy has found evidence of what might be youngest still-forming solar system yet detected.

The protostar L1527 IRS, also known as IRAS 04368+2557, as seen by NASA’s Spitzer Space Telescope (John Tobin)

The protostar, labeled L1527 IRS, resides in a stellar nursery called Taurus Cloud in the constellation Taurus about 450 light-years from Earth. It is about 300,000 years old, compared to the 4.6-billion-year age of the Sun.

“It may be even younger, depending on how fast it accumulated mass in the past,” said Dr John Tobin of the National Radio Astronomy Observatory in Charlottesville, lead author of the study published in the journal Nature (arXiv.org version).

The young star currently has about one-fifth the mass of the Sun, but will likely pull in material from its surroundings to eventually match the Sun’s mass. The disk surrounding the star contains at least enough mass to make seven Jupiters.

“This very young object has all the elements of a solar system in the making,” Dr Tobin said.

The astronomers detected both dust and carbon monoxide around L1527 IRS, and were able to measure the mass of the protostar itself.

By measuring the Doppler shift of radio waves coming from carbon monoxide in the disk around L1527 IRS, they were able to show that the rotation speed in the disk changes with the material’s distance from the star in the same fashion that the orbital speeds of planets change with distance from the Sun.

Co-author Dr Hsin-Fang Chiang of the University of Illinois, and the Institute for Astronomy of the University of Hawaii, said: “this pattern, called Keplerian rotation, marks one of the first essential steps toward forming planets, because the disk is supported by its own rotation, will mediate the flow of material onto the protostar and allow the planet formation process to begin.”

“This is the youngest protostar found thus far to show that characteristic in a surrounding disk,” Dr Tobin said. “In many ways, this system looks much like we think our own Solar system looked when it was very young.”

The group has received approval to improve their understanding of L1527 IRS by making high-precision observations with the Atacama Large Millimeter/Submillimeter Array (ALMA) in northern Chile.

“ALMA’s advanced capabilities will allow us to study more such objects at greater distances,” Dr Tobin said. “With ALMA, we will be able to learn more about how the disks form and how quickly the young stars grow to their full size, and gain a much better understanding of how stars and their planetary systems begin their lives.”

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Bibliographic information: Tobin JJ et al. 2012. A ~0.2-solar-mass protostar with a Keplerian disk in the very young L1527 IRS system. Nature 492, 83–85; doi: 10.1038/nature11610