Liquifying a rocky exoplanet
by Staff Writers
Bern, Switzerland (SPX) Oct 10, 2019
Rocky exoplanets that are around Earth-size are comparatively small, which makes them incredibly difficult to detect and characterise using telescopes. What are the optimal conditions to find such small planets that linger in the darkness? "A rocky planet that is hot, molten, and possibly harboring a large outgassed atmosphere ticks all the boxes," says Dan Bower, astrophysicist at the Center for Space and Habitability (CSH) of the University of Bern. Such a planet could be more easily seen by telescopes due to strong outgoing radiation than its solid counterpart.
The SNSF Ambizione and CSH Fellow continues: "Granted, you wouldn't want to vacation on one of these planets, but they are important to study since many if not all rocky planets begin their life as molten blobs, yet eventually some may become habitable like Earth.
Rocky planets are built from the leftovers of the leftovers. "Everything that doesn't make its way into the central star or a giant planet has the potential to end up forming a much smaller terrestrial planet," says Bower: "We have reason to believe that processes occurring during the baby years of a planet's life are fundamental in determining its life path." Therefore, Bower and a team of post-docs - dominantly from within the PlanetS network - were intrigued to uncover the observable nature of such a planet. Their study is now published in the journal Astronomy and Astrophysics.
It shows that a molten Earth would actually be around 5% larger in radius than a solid Earth, and this is due to the difference in the behavior of molten versus solid materials at the extreme conditions of a planetary interior. "In essence, a molten silicate occupies more volume than its equivalent solid, and this increases the size of the planet," Bower explains.
A difference that CHEOPS can detect
Interestingly, 5% difference in planetary radii can be measured with current and future observational facilities, notably the space telescope CHEOPS which was developed and assembled in Bern and will launch later this year.
Indeed, the latest exoplanet data already provides an inkling that low mass molten planets, sustained by intense star-light, are present in the exoplanet catalogue. Some exoplanets could therefore be Earth-like in terms of similar building blocks, yet have different amounts of solid and molten rock to explain observed variations in planet size. "They do not necessarily need to be made of exotic light materials to explain the data," says Bower.
However, even a totally molten planet may not be able to explain the observation of the most extreme low density planets. But on this the research team also has a proposition: Molten planets early in their history can outgas large atmospheres of volatile species that were originally trapped inside the magma in the interior of the planet. This could explain an additional decrease in the observed planetary density. The James Webb Space Telescope (JWST) should be able to distinguish such an outgassed atmosphere on a planet around a cool red dwarf if it is dominated by either water or carbon dioxide.
In addition to the consequences for observations, Bower, with his roots as an Earth Scientist, sees his study in a broader context: "Clearly, we can never observe our own Earth in its .history when it was also hot and molten. But interestingly, exoplanetary science is opening the door for observations of early Earth and early Venus analogues that could greatly impact our understanding of Earth and the Solar System planets. Thinking about Earth in the context of exoplanets, and vice-versa, offers new opportunities for understanding planets both within and beyond the Solar System."
|The content herein, unless otherwise known to be public domain, are Copyright 1995-2024 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. All articles labeled "by Staff Writers" include reports supplied to Space Media Network by industry news wires, PR agencies, corporate press officers and the like. Such articles are individually curated and edited by Space Media Network staff on the basis of the report's information value to our industry and professional readership. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. General Data Protection Regulation (GDPR) Statement Our advertisers use various cookies and the like to deliver the best ad banner available at one time. All network advertising suppliers have GDPR policies (Legitimate Interest) that conform with EU regulations for data collection. By using our websites you consent to cookie based advertising. If you do not agree with this then you must stop using the websites from May 25, 2018. Privacy Statement. Additional information can be found here at About Us.|