Building blocks of life found in disk around baby star
Over the past twenty years, scientists have discovered that most stars in the universe are accompanied by planets, including small, rocky planets similar to our own Earth. Using ALMA, astronomers have now found evidence that these distant planetary systems may also harbour the building blocks of life.
Just to be sure: no one has found extraterrestrial life yet. And no one knows how life on Earth got started, some 3.5 billion years ago. But one thing is certain: it all began with so-called ‘organic molecules’: compounds that contain carbon, hydrogen, oxygen and nitrogen atoms. The very first micro-organisms arose from chemical reactions of these organic molecules in the warm oceans of the early Earth.
Organic molecules can be found in many places in the universe. But they are pretty fragile, so can they survive the harsh conditions surrounding new-born stars? In our own solar system they apparently did, or we wouldn’t be here. But what about other planetary systems?
ALMA has now detected huge amounts of organic molecules in the cold, outer parts of a planetary-system-in-the-making. ALMA looked at a ‘proto-planetary disk’ surrounding the young baby star MWC 480. This star, located at a distance of 455 light-years in the constellation Taurus the Bull, is only one million years old – extremely young for a star.
As yet, no planets have been formed in MWC 480’s disk. But in the disk’s outer reaches, where icy comets will coalesce, astronomers found lots of methyl cyanide and hydrogen cyanide – two organic molecules that are important building blocks for life as we know it. In fact, there is as much methyl cyanide in the disk as there is water in all the oceans on Earth.
The researchers expect that Earth-like planets will form closer to the star within a few million years or so. When newly formed comets from the disk’s outer regions start to rain down on these planets, the organic molecules may end up in warm oceans. Who knows what kind of chemical reactions will start to take place then?
MWC 480 is a young baby star. It is the 480th entry in the Mount Wilson Catalog (MWC) of very young stars. The star was born some one billion years ago from a large coud of gas and dust in the constellation Taurus, together with many other stars. The Taurus star-forming region is located some 455 light-years from the Earth. MWC 480 is twice as massive as our own Sun. It is surrounded by a flattened, rotating disk of gas and dust from which new planets may form over the next ten million years or so. The cold, outer parts of this disk – the region where the organic molecules have been found – is between 4.5 and 15 billion kilometres from the central star.
The discovery of organic molecules in the disk surrounding MWC 480 was made by a team of astronomers led by Karin Öberg of the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Massachusetts. Karin worked together with her CfA colleagues Viviana Guzmán, Chunhua Qi, Sean Andrews, Ryan Loomis, and David Wilner, and with Kenji Furuya of Leiden Observatory in the Netherlands and Yuri Aikawa of Kobe University in Japan. The ALMA observations have been published in the scientific journal Nature.