Astronomers discover largest molecule yet in a planet-forming disc


Date:
March 8, 2022
Source:
ESO
Summary:
Using the Atacama Large Millimeter/submillimeter Array (ALMA) in
Chile, researchers have for the first time detected dimethyl ether
in a planet- forming disc. With nine atoms, this is the largest
molecule identified in such a disc to date. It is also a precursor
of larger organic molecules that can lead to the emergence of life.



FULL STORY ========================================================================== Using the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, researchers at Leiden Observatory in the Netherlands have for the first
time detected dimethyl ether in a planet-forming disc. With nine atoms,
this is the largest molecule identified in such a disc to date. It
is also a precursor of larger organic molecules that can lead to the
emergence of life.


========================================================================== "From these results, we can learn more about the origin of life on our
planet and therefore get a better idea of the potential for life in
other planetary systems. It is very exciting to see how these findings
fit into the bigger picture," says Nashanty Brunken, a Master's student
at Leiden Observatory, part of Leiden University, and lead author of
the study published today in Astronomy & Astrophysics.

Dimethyl ether is an organic molecule commonly seen in star-forming
clouds, but had never before been found in a planet-forming disc. The researchers also made a tentative detection of methyl formate, a complex molecule similar to dimethyl ether that is also a building block for
even larger organic molecules.

"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 young star
IRS 48 (also known as Oph-IRS 48) with the help of ALMA, an observatory co-owned by the European Southern Observatory (ESO). IRS 48, located
444 light-years away in the constellation Ophiuchus, has been the
subject of numerous studies because its disc contains an asymmetric, cashew-nut-shaped "dust trap." This region, 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 planets.

Many complex organic molecules, such as dimethyl ether, are thought
to arise in star-forming clouds, even before the stars themselves
are born. In these cold environments, atoms and simple molecules like
carbon monoxide stick to dust grains, forming an ice layer and undergoing chemical reactions, which result in more complex molecules. Researchers recently discovered that the dust trap in the IRS 48 disc is also an ice reservoir, harbouring dust grains covered with this ice rich in complex molecules. It was in this region of the disc that ALMA has now spotted
signs of the dimethyl ether molecule: as heating from IRS 48 sublimates
the ice into gas, the trapped molecules inherited from the cold clouds
are freed and become detectable.

"What makes this even more exciting is that we now know these larger
complex molecules are available to feed forming planets in the disc,"
explains Booth.

"This was not known before as in most systems these molecules are hidden
in the ice." The discovery of dimethyl ether suggests that many other
complex molecules that are commonly detected in star-forming regions
may also be lurking on icy structures in planet-forming discs. These
molecules are the precursors of prebiotic molecules such as amino acids
and sugars, which are some of the basic building blocks of life.

By studying their formation and evolution, researchers can therefore gain
a better understanding of how prebiotic molecules end up on planets,
including our own. "We are incredibly pleased that we can now start to
follow the entire journey of these complex molecules from the clouds
that form stars, to planet- forming discs, and to comets. Hopefully with
more observations we can get a step closer to understanding the origin of prebiotic molecules in our own Solar System," says Nienke van der Marel,
a Leiden Observatory researcher who also participated in the study.

Future studies of IRS 48 with ESO's Extremely Large Telescope (ELT),
currently under construction in Chile and set to start operations later
this decade, will allow the team to study the chemistry of the very
inner regions of the disc, where planets like Earth may be forming.


========================================================================== Story Source: Materials provided by ESO. Note: Content may be edited
for style and length.


========================================================================== Related Multimedia:
* Molecules_in_the_disc_around_the_star_IRS_48 ========================================================================== Journal Reference:
1. Nashanty G. C. Brunken, Alice S. Booth, Margot Leemker, Pooneh
Nazari,
Nienke van der Marel, Ewine F. van Dishoeck. A major asymmetric
ice trap in a planet-forming disk. Astronomy & Astrophysics, 2022;
659: A29 DOI: 10.1051/0004-6361/202142981 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/03/220308102807.htm

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