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Planet-forming discs around young low-mass star differs fundamentally from one around sun-like star

Using the James Webb Space Telescope, an international team of researchers, including Leiden Professor of Molecular Astrophysics Ewine van Dishoeck, has discovered a palette of hydrocarbons in a planet-forming disc around a young, low-mass star. The results confirm that discs around very lightweight young stars are really different from those around sun-like stars. As a result, the atmospheres of planets around these stars are also different. The astronomers publish their findings on 7 June in Science.

The team investigated the region around the still young star ISO-ChaI-147. That star is located in the southern constellation Chameleon about 650 light years away from us. This star is a lightweight. It is nine times lighter than our sun. Scientists are interested in lightweight stars because more Earth-like planets seem to form there than around very heavy stars. The researchers used MIRI (Mid-Infrared Instrument) for these observations.

Plenty of hydrocarbons, little water

The astronomers found thirteen different hydrocarbons in the planet-forming disc around the star. The largest molecule found is benzene (C6H6), which incidentally was first observed around another very bright young star a year ago. Most unusual is the finding of ethane (C2H6). It is the first time ethane has been detected outside our solar system. ‘Great that we are now seeing all these molecules in the nurseries of planets,’ says first author Aditya Arabhavi, PhD student at the University of Groningen. ‘We had not dared to dream this.’

The chemistry of planet-forming discs is a major focus at Leiden and thanks to JWST, astronomers are now getting a wealth of new data. ‘This result is one of the big surprises: that discs around very bright stars contain a lot of hydrocarbons and little water,’ says Ewine van Dishoeck. This vast difference in chemical composition could possibly also influence the composition of Earth-like planets forming around bright stars.

Reaping scientific fruits

Dutch scientists have been closely involved in JWST for more than 25 years, in particular in the design and construction of the MIRI instrument. ‘Now we can finally reap the scientific fruits!’ says Van Dishoeck. The research took place within the MIRI mid-INfrared Disk Survey (MINDS). Astronomers from Groningen, Leiden, and Nijmegen are part of the team. From Leiden, Milou Temmink and Marissa Vlasblom are also involved in addition to Van Dishoeck. The identification of the molecules via their spectral fingerprint was possible thanks to a collaboration with chemists. In total, the researchers aim to analyse more than fifty dust discs around young stars. They expect to discover other molecules soon and gain more knowledge about the formation of rocky planets in discs around small and larger stars.

Scientific publication
Abundant hydrocarbons in the disk around a very-low-mass star. By: A.M. Arabhavi, I. Kamp, Th. Henning, E.F. van Dishoeck, V. Christiaens, et al. In: Science, 7 juni 2024.

Image: NASA/JPL-Caltech/T. Pyle (SSC)

About NOVA

The Netherlands Research School for Astronomy (NOVA) is the partnership of the astronomical institutes of the universities of Amsterdam, Groningen, Leiden and Nijmegen. Top research school NOVA's mission is to conduct groundbreaking astronomy research, train young astronomers at the highest international level and share new discoveries with society. The NOVA laboratories specialize in building state-of-the-art optical/infrared and submillimeter instrumentation for the largest telescopes on Earth.

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