Data will characterize the planetary atmosphere models

A super-Earth is discovered that can be used to test planetary atmospheric models

Moments of the virtual journey, with overlaid astronomical data. Credit: RenderArea

Over the past 25 years, astronomers have discovered a wide variety of exoplanets made of rock, ice, and gas, thanks to the construction of astronomical instruments specifically designed for planetary searches. Using a combination of different observation techniques, they were able to determine a large number of masses, sizes and thus the density of the planets, which helps them to estimate their internal composition and increase the number of planets discovered outside the country. Solar system.

However, studying the atmosphere of the rocky planets, which makes it possible to fully characterize the exoplanets that are similar to Earth, is very difficult with instruments currently available. For this reason, the atmospheric models for rocky planets remain untested.

It is therefore interesting that the astronomers in the CARMENES (Calar Alto high-resolution search for M dwarfs with Exoearths with near-infrared and optical échelle spectrographs), a consortium in which the Instituto de Astrofisica de Canarias (IAC) recently launched a is a partner. published a study led by Trifon Trifonov, an astronomer at the Max Planck Institute of Astronomy in Heidelberg (Germany), on the discovery of a hot super-Earth in orbit around a nearby red dwarf star Gliese 486, only 26 light-years from the Sun.

To do this, scientists used the combined techniques of transit photometry and radial velocity spectroscopy, including observations using the instrument MuSCAT2 (Multicolor Simultaneous Camera used to study the atmosphere of transit exoplanets) on the Carlos Sánchez telescope of 1 , 52 m at the Teide Observatory. . The results of this study were published in the journal Science.







This virtual journey to Gliese 486b begins with its position in the night sky. After focusing on the parent star Gliese 486b, the dimensions are depicted. Finally, we fly to the exoplanet Gliese 486b and explore its possible surface, which probably looks like Venus, with a hot and dry landscape interspersed with glowing lava flows. Credit: RenderArea

The planet they discovered, called Gliese 486b, has a mass of 2.8 times that of Earth and is only 30% larger. “To calculate its average density from the measurements of its mass and radius, we conclude that its composition is similar to that of Venus or Earth, with metal cores in them,” explains Enric Pallé, an IAC researcher and co-author of the article.

Gliese 486b orbits its host every 1.5 days on a circular orbit, at a distance of 2.5 million kilometers. Despite being so close to its star, the planet has probably retained some of its original atmosphere (the star is much cooler than our sun), so it’s a good candidate to get into more detail with the next generation of space. and land observation. telescopes.

A super-Earth is discovered that can be used to test planetary atmospheric models

The diagram gives an estimate of the inner compositions of selected exoplanets based on their masses and radii in Earth units. The red dot represents Gliese 486b, and the orange symbols represent planets around cool stars such as Gliese 486. The gray dots show planets housed by warmer stars. The color curves indicate the theoretical mass-radius relationships for pure water at 700 K (blue), for the mineral enstatite (orange), for the Earth (green) and pure iron (red). For comparison, the diagram also highlights Venus and Earth. Credit: Trifonov et al./MPIA Graphic Department.

For Trifonov, the fact that this planet is so close to the sun is exciting because it will be possible to study it in more detail using powerful telescopes such as the leading James Webb Space Telescope and the ELT (Extremely Large Telescope) now being built. word. “

Gliese 486b takes the same time to rotate on its axis as to orbit its host, so it always has the same side to the star. Although Gliese 486 is much duller and cooler than the sun, the radiation is so intense that the surface of the planet heats up to at least 700 K (about 430 degrees C). As a result, the surface of Gliese 486b probably looks more like the surface of Venus than Earth, with a hot dry landscape, with burning lava rivers. Unlike Venus, however, Gliese 486b may have a thin atmosphere.

A super-Earth is discovered that can be used to test planetary atmospheric models

The graph illustrates the orbit of a transitional rocky exoplanet such as Gliese 486b around its host. During transport, the planet obscures the tail disk. At the same time, a small portion of the starlight passes through the atmosphere of the planet. While Gliese 486b continues to orbit, parts of the illuminated hemisphere become visible as phases until the planet disappears behind the star. Credit: MPIA Graphic Department.

Calculations made with existing models of planetary atmosphere may correspond to the hot surface and thin atmosphere scenarios because stellar radiation tends to evaporate the atmosphere while the planet’s gravitational pulls it back. It is difficult today to determine the balance between the two contributions.

“The discovery of Gliese 486b was a stroke of luck. If it were about a hundred degrees warmer, all its surfaces would be lava, and its atmosphere would be vaporized rock,” explains José Antonio Caballero, a researcher at the Astrobiology Center (CAB, CSIC -INTA) and co-author of the article. “On the other hand, if Gliese 486b had been about a hundred degrees cooler, it would not have been suitable for the follow-up observations.”

A super-Earth is discovered that can be used to test planetary atmospheric models

Artist’s impression of the atmosphere of Gliese 486b. Credit: RenderArea

Future planned observations by the CARMENES team will try to determine its orbital inclination, which will allow Gliese 486b to cross the line of sight between us and the surface of the star, thus removing from its light and to produce so-called passages. .

They will also make spectroscopic measurements, using emission spectroscopy, when the regions of the hemisphere illuminated by the star are visible as phases of the planet (analogous to the phases of our moon) during the orbits of Gliese 486b before disappear. the star. The spectrum observed will contain information about the conditions on the illuminated hot surface of the planet.

“We can not wait until the new telescopes are available,” admits Trifonov. ‘The results we can obtain with them will help us to better understand the atmosphere of rocky planets, their expansion, their very high density, their composition and their influence on the distribution of energy around the planets.

  • A super-Earth is discovered that can be used to test planetary atmospheric models

    Artistic impression of the surface of the newly discovered hot super-Earth Gliese 486b. With a temperature of about 700 Kelvin (430 ° C), Gliese 486b may have an atmosphere. Credit: RenderArea

  • MAROON-X begins its exoplanet quest

    Colored 2D spectra of the star Gliese 486 as seen with MAROON-X. The two spectra come from the two camera arms of MAROON-X. Each spectrum covers the wavelength range of 500-670 nm and the color coding corresponds to how a human eye would see the colors. Credit: International Gemini Observatory / NOIRLab / NSF / AURA / A. Seifahrt

The CARMENES project, the consortium of which consists of 11 research institutes in Spain and Germany, aims to monitor a set of 350 red dwarf stars to search for planets such as Earth, using a spectrograph on the 3, 5 m telescope at the Calar Alto Observatory. (Spain). The present study also used spectroscopic measurements to derive the mass of Gliese 486b. Observations were made with the MAROON-X instrument on Gemini North (8.1m) in the USA, and archival data were taken from the Keck 10 m telescope (USA) and the 3.6m telescope from ESO, (Chile).

The photometric observations come from NASA’s TESS (Transiting Exoplanet Survey Satellite) space station, (USA), the data of which were basically to obtain the radius of the planet, from the MuSCAT2 instrument on the 1.52 m Carlos Sánchez- telescope at the Teide Observatory (Spain). and from, among others, the LCOGT (Las Cumbres Observational Global Telescope) in Chile.


Super-Earth discovered around a nearby red dwarf


More information:
T. Trifonov et al. A rocky exoplanet in the perimeter suitable for atmospheric exploration. Science (2021). science.sciencemag.org/cgi/doi… 1126 / science.abd7645

Provided by Instituto de Astrofísica de Canarias

Quotation: Super-Earth Discovered: Data Will Characterize Planetary Atmosphere Models (2021, March 4) Retrieved March 5, 2021 from https://phys.org/news/2021-03-super-earth-planetary-atmosphere.html

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