Tracing the origins of life on our planet and understanding the potential of life in other planetary systems is the dream of many scientists. Astronomers sometimes start at the molecular level, using organic molecules as a valuable clue.
Recently, a group of astronomers used Chile's ALMA (Atacama Large Millimeter/Submillimeter Wave Array) to detect dimethyl ether (CH3OCH3) for the first time in a planet-forming disk. The molecule contains 9 atoms, the largest molecule ever found in this type of dish. It is also a precursor to larger organic molecules that have the potential to bring about life. The study was recently published in Astronomy and Astrophysics.
Astronomers have detected dimethyl ether for the first time in a planet-forming disk. | Image credit: ESO/L. Cal ada, ALMA (ESO/NAOJ/NRAO)/A. Pohl, van der Marel et al., Brunken et al.
Molecules in dust traps
In the new study, astronomers used ALMA to make detailed observations of planetary disks around the young star IRS 48, also known as Oph-IRS 48.
Ophiuchus. The red circle shows the location of the Oph-IRS 48 system. | Image credit: ESO, IAU and Sky & Telescope
IRS 48, located about 444 light-years away in the constellation of Ophiuchus, is actually an "old friend" of many researchers and has been the subject of many studies because the planetary disk here contains an asymmetrical, cashew nut-shaped "dust trap". This area retains a large number of millimeter-sized dust particles that can come together and grow into thousand-meter-sized objects, such as comets, asteroids, and possibly even planets.
Cashew-like dust trap observed by ALMA. | Image credit: ALMA (ESO/NAOJ/NRAO)/Nienke van der Marel
Dimethyl ether is a relatively complex organic molecule like this one that is often thought to arise in a star-forming cloud, and they may even predate the birth of stars. In these cold environments, atoms and simple molecules like carbon monoxide (CO) stick to dust particles, forming ice layers and chemical reactions that give birth to more complex molecules.
The researchers found through observations that the dust trap in the IRS 48 planetary disk is also such an "ice reservoir", which contains many dust particles, which are covered by ice rich in complex molecules. As it delved deeper into this region of the planetary disk, ALMA eventually found signs of dimethyl ether molecules.
Various gas molecules found by ALMA around IRS 48, including formaldehyde (orange), methanol (green) and dimethyl ether (blue), as well as carbon monoxide (purple), are present throughout the dish. The asterisk represents the position of the central star. | Image credit: ESO/L. Cal ada, ALMA (ESO/NAOJ/NRAO)/A. Pohl, van der Marel et al., Brunken et al.
As the heat from IRS 48 sublimates the ice into gas, molecules left behind in the cold clouds are released and become detectable. Such molecules have never been found before in the disks that form planets.
The researchers also made initial discoveries of traces of methyl formate, a complex molecule similar to dimethyl ether that is also a basic building block of larger organic molecules.
More complex molecules
The discovery of dimethyl ether suggests that many other complex molecules typically detected in star-forming regions may also be lurking on the ice structure of planetary disks. These molecules are precursors of probiomolecules, such as amino acids and sugars, which are indispensable fundamental components of life.com.
The researchers believe that by tracking the "journey" of these molecules from the clouds that form stars to the planetary disks to celestial bodies, studying their formation and evolution will lead to a deeper understanding of how pre-biomolecules eventually emerged on planets, including our planet.
In the future, when the Extra-Large Telescope (ELT) is completed, research on IRS 48 will continue. This gives scientists the opportunity to study chemistry in regions further inside the planetary disk, where planets like Earth may be forming.
#创作团队:
Compiled: Gaviota
Typography: Wenwen
#参考来源:
https://www.eso.org/public/news/eso2205/
https://www.aanda.org/articles/aa/full_html/2022/03/aa42981-21/aa42981-21.html
#图片来源:
封面图:ALMA (ESO/NAOJ/NRAO)/A. Pohl, van der Marel et al., Brunken et al.
首图:ALMA (ESO/NAOJ/NRAO)/A. Pohl, van der Marel et al., Brunken et al.