Free Astronomy Magazine May-June 2019

MAY-JUNE 2019 (CH 3 OH), acetone (CH 3 COCH 3 ), ac- etaldehyde (CH 3 CHO), methyl for- mate (CH 3 OCHO), and acetonitrile (CH 3 CN). This is the first time that acetone was unambiguously de- tected in a planet forming region or protoplanetary disk. Various molecules are frozen in ice around micrometer-sized dust parti- cles in protoplanetary disks. V883 Ori’s sudden flare-up is heating the disk and sublimating the ice, which releases the molecules into gas. The region in a disk where the tempera- ture reaches the sublimation tem- perature of the molecules is called the “snow line.” The radii of snow lines are about a few astronomical units (au) around normal young stars, however, they are enlarged almost 10 times around bursting stars. “It is difficult to image a disk on the scale of a few au with current tele- scopes,” said Lee. “However, around an outburst star, ice melts in a wider area of the disk and it is easier to see the distribution of molecules. We are interested in the distribution of complex organic molecules as the building blocks of life.” Ice, including frozen organic mole- cules, could be closely related to the origin of life on planets. In our Solar System, comets are the focus of at- tention because of their rich icy com- pounds. For example, the European Space Agency’s legendary comet ex- plorer Rosetta found rich organic chemistry around the comet Churyu- mov-Gerasimenko. Comets are thought to have been formed in the outer colder region of the proto-Solar System, where the molecules were contained in ice. A rtist’s impression of the protoplanetary disk around a young star V883 Ori. The outer part of the disk is cold and dust particles are covered with ice. ALMA detected various com- plex organic molecules around the snow line of water in the disk. [Na- tional Astronomical Ob- servatory of Japan]