Building blocks of life found around young star
A team of astronomers including Leiden Professor Ewine van Dishoeck were the first to discover sugar molecules in the dust and gas around a young, sun-like star. The discovery shows that the building blocks of life are available in the right place at the right time to be incorporated into the planets that are forming around the star. Appearing soon in Astrophysical Journal Letters.
‘The sugar in question, glycolaldehyde, is not that different from the sugar we use to sweeten our coffee,’ says first author Jes Jørgensen, former NOVA PhD student in Leiden and currently affiliated to the Niels Bohr Institute in Denmark. ‘The molecule is one of the ingredients in the formation of RNA which, just like its cousin DNA, forms one of the building blocks of life.’
More about the photograph
The photograph shows the protostar IRAS 16293-2422: the red object in the middle of the small square. The inset offers an artist’s impression of the molecular structure of glycolaldehyde (C2H4O2). Carbon atoms are depicted in grey, oxygen atoms are red and hydrogen atoms white. On the WISE satellite images, blue and cyan represent infrared radiations with a wavelength of 3.4 and 4.6 micrometers which mostly come from stars. Green and red belong to infrared radiations of respectively 12 and 22 micrometers, which are primarily radiated by dust.
The astronomers discovered molecules of glycolaldehyde, a simple form of sugar, using the Atacama Large Millimeter/submillimeter Array (ALMA) in the gas surrounding IRAS 16293-2422, a young binary star with approximately the same mass as the sun. Although glycolaldehyde has already been observed in interstellar space, this is the first time that it was observed so close to a sun-like star; the distance is comparable to that between the sun and Uranus. The discovery proves that some of the chemical compounds required for life to begin are already available near this star during the planet formation process.
ALMA’s high sensitivity – even in the technically challenging shortest wavelengths at which the telescope can operate – was crucial for these observations. The observations were made during the Science Verification Phase of the Observatory, whereby only part of the array of antennas was available. 'The quality of the ALMA data in the highest frequencies – measured using Dutch Band-9 receivers – is excellent, much better than we had expected in this early phase of the project. Thanks to the ALMA Allegro expertise centre we were also able to directly reduce the data. The line density is 10 times higher than what we had seen so far. This means that ALMA will really revolutionise astrochemistry,’ says co-author Prof. Ewine van Dishoeck.
Team member Cécile Favre, University of Aarhus, Denmark, adds: 'What makes these findings so exciting is that the ALMA measurements show that the sugar molecules are falling towards one of the stars in the solar system. The sugar molecules are not only at the right place to reach a planet, but they are also moving towards it.’
The clouds of gas and dust that collapse together to form new stars are extremely cold. As a result many gases freeze and attach to dust molecules, where they can bind to form more complex molecules. However, as soon the star at the heart of a spinning cloud of gas and dust has formed, it warms the inner parts of the cloud to approximately room temperature. In the process the chemically complex molecules evaporate and gases are released which then emit a characteristic radio wave. This wave can be mapped using powerful radio telescopes such as ALMA. The processes are simulated at the Raymond & Beverly Sackler Laboratory for Astrophysics in Leiden; the ALMA readings now confirm that this is really what is happening.
At a distance of approximately 400 light years, IRAS 16293-2422 is relatively close to the Earth, which makes it a perfect target for research on molecules and chemical reactions surrounding young stars. Thanks to the possibilities of the new generation of telescopes such as ALMA, astronomers are now able to study in detail the clouds of gas and dust from which planet systems arise.
Jørgensen: 'An important question is: how complex can molecules get before they are incorporated into the new planets? This would tell us something about the way in which life can arise elsewhere. ALMA measurements will play an important role in solving this question.’ This research is described in an article due to appear in Astrophysical Journal Letters.
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(30 September 2012)
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