Planets form in a disk that contains alcohol
Astronomers have found alcohol in a planet-forming disk. It’s not the regular form of alcohol that makes you drunk. Instead, it’s methyl alcohol, or methanol. Moreover, the methanol that has been found is not in the form of a liquid. Instead, it’s a gas.
Methanol consists of rather large molecules. Each methanol molecule has one atom of carbon (C), four of hydrogen (H), and one of oxygen (O). The chemical formula of methanol is CH3OH. On Earth, methanol is being used in the chemical industry. It’s very toxic – just 25 grams of the stuff could kill you.
Using ALMA, astronomers have now found methanol in the disk of gas and dust around the young star TW Hydrae. In the future, the material in this disk will clump together into planets. TW Hydrae is in a star-forming region in the constellation Hydra, the Water Snake, at just 170 light-years. It’s the nearest star with a planet-forming disk that we know of.
ALMA could detect the faint millimeter radiation that is emitted by methanol molecules. The methanol sits in a broad ring in the disk, between 4.5 and 10 billion kilometers from the star. Never has methanol been found in a protoplanetary disk. The find is important, because methanol is one of the chemical building blocks of amino acids. And amino acids are the basic ingredients of life.
It’s also the first time that astronomers are witnessing the transition from solid organic molecules into a gas. In space, methanol molecules can only form in thin coatings of ice on the surfaces of dust grains. Apparently, the ‘frozen’ methanol in the disk of TW Hydrae has somehow evaporated into gaseous methanol.
It’s still unclear how this transition from ice into gas happens. Future observations of TW Hydrae and of other planet-forming disks will hopefully provide more answers.
TW Hydrae is a young ‘proto-star’ at some 170 light-years in the constellation Hydra, the Water Snake. The star is about 20 percent less massive than our own Sun. It’s just a few million years old. (for comparison: our Sun is 4.6 billion years old). The star is surrounded by a flat, rotating disk of gas and dust. Because TW Hydrae is so close to us, it can be studied very well. In the past, ALMA already imaged the protoplanetary disk of TW Hydrae in much detail.
The discovery of methanol in the protoplanetary disk of TW Hydrae was made by an international group of astronomers led by British astronomer Catherine Walsh. At the time, Catherine worked at Leiden Observatory in the Netherlands. For the ALMA observations, she worked together with colleagues from Leiden, the United Stated, the United Kingdom, and Japan. The team has published the discovery in The Astrophysical Journal, a professional magazine of astronomy.