Free Astronomy Magazine May-June 2022

38 MAY-JUNE 2022 ASTRO PUBLISHING young star IRS 48 (also known as Oph-IRS 48) with the help of ALMA, an observatory co-owned by the Eu- ropean Southern Ob- servatory (ESO). IRS 48, located 444 light- years away in the con- stellation Ophiuchus, has been the subject of numerous studies because its disc con- tains an asymmetric, cashew-nut-shaped “dust trap”. This re- gion, which likely formed as a result of a newly born planet or small companion star located between the star and the dust trap, retains large numbers of millimetre-sized dust grains that can come together and grow into kilometre- sized objects like comets, asteroids and potentially even plan- ets. Many complex or- ganic molecules, such as dimethyl ether, are thought to arise in star-forming clouds, even before the stars themselves are born. In these cold environ- ments, atoms and sim- ple molecules like carbon monoxide stick to dust grains, form- ing an ice layer and undergoing chemical reactions, which result in more complex mol- ecules. Researchers re- cently discovered that the dust trap in the IRS 48 disc is also an ice reser- voir, harbouring dust grains covered with this ice rich in complex mole- T hese images from the Atacama Large Millimeter/submillimeter Array (ALMA) show where various gas molecules were found in the disc around the IRS 48 star, also known as Oph-IRS 48. The disc contains a cashew-nut-shaped region in its southern part, which traps millimetre- sized dust grains that can come together and grow into kilometre-sized objects like comets, as- teroids and potentially even planets. Recent observations spotted several complex organic molecules in this region, including formaldehyde (H 2 CO; orange), methanol (CH 3 OH; green) and dimethyl ether (CH 3 OCH 3 ; blue), the last being the largest molecule found in a planet-forming disc to date. The emission signaling the presence of these molecules is clearly stronger in the disc’s dust trap, while carbon monoxide gas (CO; purple) is present in the entire gas disc. The location of the central star is marked with a star in all four images. The dust trap is about the same size as the area taken up by the methanol emission, shown on the bottom left. [ALMA (ESO/NAOJ/NRAO)/A. Pohl, van der Marel et al., Brunken et al.] “It is really exciting to finally detect these larger molecules in discs. For a while we thought it might not be possible to observe them,” says co- author Alice Booth, also a researcher at Leiden Observatory. The molecules were found in the planet-forming disc around the