Scientists using the Atacama Large Millimeter/submillimeter Array (ALMA) to study the protoplanetary disk around a young star have discovered the most compelling chemical evidence to date of the formation of protoplanets. The discovery will provide astronomers with an alternate method for detecting and characterizing protoplanets when direct observations or imaging are not possible. The results will be published in an upcoming edition of The Astrophysical Journal Letters.
HD 169142 is a young star located in the constellation Sagittarius that is of significant interest to astronomers due to the presence of its large, dust- and gas-rich circumstellar disk that is viewed nearly face-on. Several protoplanet candidates have been identified over the last decade, and earlier this year, scientists at the University of Liège and Monash University confirmed that one such candidate— HD 169142 b— is, in fact, a giant Jupiter-like protoplanet. The discoveries revealed in a new analysis of archival data from ALMA— an international collaboration in which the National Science Foundation’s National Radio Astronomy Observatory (NRAO) is a member— may now make it easier for scientists to detect, confirm, and ultimately characterize, protoplanets forming around young stars.
“When we looked at HD 169142 and its disk at submillimeter wavelengths, we identified several compelling chemical signatures of this recently-confirmed gas giant protoplanet,” said Charles Law, an astronomer at the Center for Astrophysics | Harvard & Smithsonian, and the lead author of the new study. “We now have confirmation that we can use chemical signatures to figure out what kinds of planets there might be forming in the disks around young stars.”
The team focused on the HD 169142 system because they believed that the presence of the HD 169142 b giant protoplanet was likely to be accompanied by detectable chemical signatures, and they were right. Law’s team detected carbon monoxide (both 12CO and its isotopologue 13CO) and sulfur monoxide (SO), which had previously been detected and were thought to be associated with protoplanets in other disks. But for the first time, the team also detected silicon monosulfide (SiS). This came as a surprise because in order for SiS emission to be detectable by ALMA, silicates must be released from nearby dust grains in massive shock waves caused by gas traveling at high velocities, a behavior typically resulting from outflows that are driven by giant protoplanets. “SiS was a molecule that we had never seen before in a protoplanetary disk, let alone in the vicinity of a giant protoplanet,” Law said. “The detection of SiS emission popped out at us because it means that this protoplanet must be producing powerful shock waves in the surrounding gas.”
With this new chemical approach for detecting young protoplanets, scientists may be opening a new window on the Universe and deepening their understanding of exoplanets. Protoplanets, especially those that are still embedded in their parental circumstellar disks such as in the HD 169142 system, provide a direct connection with the known exoplanet population. “There’s a huge diversity in exoplanets and by using chemical signatures observed with ALMA, this gives us a new way to understand how different protoplanets develop over time and ultimately connect their properties to that of exoplanetary systems,” said Law. “In addition to providing a new tool for planet-hunting with ALMA, this discovery opens up a lot of exciting chemistry that we’ve never seen before. As we continue to survey more disks around young stars, we will inevitably find other interesting but unanticipated molecules, just like SiS. Discoveries such as this imply that we are only just scratching the surface of the true chemical diversity associated with protoplanetary settings.”
The National Radio Astronomy Observatory (NRAO) is a major facility of the National Science Foundation (NSF) operated under a cooperative agreement by Associated Universities, Inc.
The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of the European Organisation for Astronomical Research in the Southern Hemisphere (ESO), the U.S. National Science Foundation (NSF), and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in cooperation with the National Research Council of Canada (NRC) and the National Science and Technology Council (NSTC) in Taiwan and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI).
ALMA construction and operations are led by ESO on behalf of its Member States; by the National Radio Astronomy Observatory (NRAO), managed by Associated Universities, Inc. (AUI), on behalf of North America; and by the National Astronomical Observatory of Japan (NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning, and operation of ALMA.
Amy C. Oliver, FRAS
Public Information & News Manager, NRAO
More News From Atacama Large Millimeter/submillimeter Array
Scientists studying the supermassive black hole at the heart of the M87 galaxy have revealed the origins of the monster’s powerful jet and imaged the jet and its source together for the first time. What’s more, the observations have revealed that the black hole’s ring is much larger than scientists previously believed.
Radio astronomers have observed galaxies billions of light years away. But how do they know just how far away those galaxies are?
On March 13th, 2023, astronomers around the world will mark the 10th anniversary of the inauguration of the Atacama Large Millimeter/submillimeter Array (ALMA), the world’s largest radio telescope. Over the past decade, the international ALMA collaboration— led by the U.S. National Science Foundation’s National Radio Astronomy Observatory (NRAO), the European Southern Observatory (ESO), and the National Astronomical Observatory of Japan (NAOJ)— has revolutionized our understanding of the Universe and unveiled its secrets, from the formation of planets, stars, and galaxies to deciphering the chemistry of the cosmos, and even taking part in capturing the first images of black holes.
Scientists studying a nearby protostar have detected the presence of water in its circumstellar disk. The new observations made with the Atacama Large Millimeter/submillimeter Array (ALMA) mark the first detection of water being inherited into a protoplanetary disk without significant changes to its composition. These results further suggest that the water in our Solar System formed billions of years before the Sun. The new observations are published today in Nature.
More News Related to Protoplanets and Exoplanets
The Universe is a dynamic and exciting place, with stars, planets, and galaxies being born, dying, and undergoing dramatic changes. In 2022, the telescopes of the National Science Foundation’s National Radio Astronomy Observatory (NRAO) revealed fascinating new details about several of these processes, and we’re giving you a taste of the greatest radio astronomy moments of the year.
Scientists using the Atacama Large Millimeter/submillimeter Array (ALMA)— in which the National Radio Astronomy Observatory (NRAO) is a partner— to study planet formation have made the first-ever detection of gas in a circumplanetary disk. What’s more, the detection also suggests the presence of a very young exoplanet.
Most planets orbit a star, but some planets can escape and “go rogue.” But how do astronomers study planets that wander the cold dark of interstellar space? Join our host, Summer Ash of the National Radio Astronomy Observatory, as she talks about how radio astronomers study rogue planets.