UZH researchers have analyzed the composition and structure of far-away exoplanets using statistical tools. Their analysis indicates whether a planet is earth-like, made up of pure rock or a water-world. The larger the planet, the more hydrogen and helium surround it.
Is there a second Earth out there in space? Our knowledge of planetary systems far, far away is increasing constantly, as new technologies continue to sharpen our gaze into space. To date, 3,700 planets have already been discovered outside our solar system.
The planetary masses and radii of these exoplanets can be used to infer their mean density, but not their exact chemical composition and structure. The intriguing question about what these planets could look like is thus still open.
“Theoretically, we can assume various compositions, such as a world of pure water, a world of pure rock, and planets that have hydrogen-helium atmospheres and explore what radii are expected” explains Michael Lozovsky, a doctoral candidate in the group of Prof. Ravit Helled at the Institute for Computational Science at the University of Zurich.
Thresholds for planetary composition
Lozovsky and collaborators have used databases and statistical tools to characterize exoplanets and their atmospheres. These are fairly common and surrounded by a volatile layer of hydrogen and helium. However, the directly measured data previously didn’t allow the researchers to determine the exact structure, since different compositions may lead to the same mass and radius.
In addition to the accuracy of the data relating to mass and radius, the research team thus also investigated the assumed internal structure, temperature and reflected radiation in 83 of the 3,700 known planets, for which the masses and radii are well-determined.
“We used a statistical analysis to set limits on possible compositions. Using a database of detected exoplanets, we found that every theoretical planetary structure has a ‘threshold radius’, a planetary radius above which no planets of this composition exist,” explains Michael Lozovsky. The amount of elements in the gaseous layer that are heavier than helium, the percentage of hydrogen and helium, as well as the distribution of elements in the atmosphere are important factors in determining the threshold radius.
Super-Earths and mini-Neptunes
The researchers from the Institute for Computational Science found that planets with a radius of up to 1.4 times that of Earth (6,371 kilometers) can be earth-like, i.e. they have a composition similar to Earth. Planets with radii above this threshold have a higher share of silicates or other light materials.
Most of the planets with a radius above 1.6 radii of the Earth must have a layer of hydrogen-helium gas or water in addition to their rocky core, while those larger than 2.6 Earth radii can’t be water worlds and therefore might be surrounded by an atmosphere.
Planets with radii larger than 4 Earth radii are expected to be very gaseous and consist of at least 10 percent hydrogen and helium, similarly to Uranus and Neptune.
The findings of the study provide new insights into the development and diversity of these planets. One particularly interesting threshold concerns the difference between large terrestrial-like planets – otherwise known as super-Earths – and small gaseous planets, also referred to as mini-Neptunes.
According to the researchers, this threshold lies at a radius of three times that of Earth. Below this threshold, it is therefore possible to find earth-like planets in the vast expanse of the galaxy.
Institute for Computational Science (ICS)
University of Zurich
Phone +41 44 635 61 89
M. Lozovsky, R. Helled, C. Dorn, and J. Venturini. Threshold Radii of Volatile-Rich Planets. Astrophysics. Astrophysical Journal. 9. October 2018, DOI: 10.3847/1538-4357/aadd09
Melanie Nyfeler | Universität Zürich
Newly discovered adolescent star seen undergoing 'growth spurt'
19.12.2018 | University of Exeter
New type of low-energy nanolaser that shines in all directions
18.12.2018 | Eindhoven University of Technology
Different eras of civilization are defined by the discovery of new materials, as new materials drive new capabilities. And yet, identifying the best material...
Researchers from the University of Basel have reported a new method that allows the physical state of just a few atoms or molecules within a network to be controlled. It is based on the spontaneous self-organization of molecules into extensive networks with pores about one nanometer in size. In the journal ‘small’, the physicists reported on their investigations, which could be of particular importance for the development of new storage devices.
Around the world, researchers are attempting to shrink data storage devices to achieve as large a storage capacity in as small a space as possible. In almost...
The more objects we make "smart," from watches to entire buildings, the greater the need for these devices to store and retrieve massive amounts of data quickly without consuming too much power.
Millions of new memory cells could be part of a computer chip and provide that speed and energy savings, thanks to the discovery of a previously unobserved...
What if, instead of turning up the thermostat, you could warm up with high-tech, flexible patches sewn into your clothes - while significantly reducing your...
A widely used diabetes medication combined with an antihypertensive drug specifically inhibits tumor growth – this was discovered by researchers from the University of Basel’s Biozentrum two years ago. In a follow-up study, recently published in “Cell Reports”, the scientists report that this drug cocktail induces cancer cell death by switching off their energy supply.
The widely used anti-diabetes drug metformin not only reduces blood sugar but also has an anti-cancer effect. However, the metformin dose commonly used in the...
12.12.2018 | Event News
10.12.2018 | Event News
06.12.2018 | Event News
19.12.2018 | Information Technology
19.12.2018 | Physics and Astronomy
19.12.2018 | Life Sciences