Tag: exoplanet atmospheres

Webb Telescope Finds No Signs of a Thick Atmosphere Around a Second TRAPPIST-1 Planet

The TRAPPIST-1 system, with its seven rocky planets orbiting close to their red dwarf Sun, is of great interest to planetary scientists and astrobiologists. Several early exoplanet James Webb Space Telescope observations have focused on the system and whether its planets have atmospheres.  So far, the results are less than promising, but the habitable zone TRAPPIST-1 planets have yet to be characterized. {NASA/JPL-Caltech/R. Hurt, T. Pyle (IPAC)}

Among the most eagerly awaited results from the early observations of the James Webb Space Telescope (JWST) is whether or not the seven rocky planets of the TRAPPIST-1 system have atmospheres.

The TRAPPIST-1 planets are close to us (40 light-years away), are all solid rather than gaseous, and they orbit a cool and small sun that makes the planets easier to observe and measure.  Not surprisingly, all seven of the planets in the system will be observed during the first year of JWST observations and the results have begun to come in.

And so far, at least, the planets do not have atmospheres, or at least don’t have substantial atmospheres.

The planet closest to its sun, TRAPPIST 1-b was determined to be devoid of an atmosphere earlier this year and last week a Nature paper reportsed that TRAPPIST 1-C also does not appear to have anything more than a very thin atmosphere.

Neither findings was completely surprising, since these are the two planets closest to the star.  But even so, the results indicate that gaseous atmospheres require a particular collection of planetary, stellar and system conditions that may be difficult to achieve.

“TRAPPIST-1 c is interesting because it’s basically a Venus twin,” explained co-author Laura Kreidberg, co-author of the paper and and Director at Max Planck Institute for Astronomy in Germany. “It’s about the same size as Venus and receives a similar amount of radiation from its host star as Venus gets from the Sun.”

Before the observations, she said “we thought it could have a thick carbon dioxide atmosphere like Venus.”  But now, “we can definitely rule out a thick and Venus-like atmosphere.”

In a Max Planck Institute release, the large international team studying TRAPPIST 1-C reports that while faint signals of a possible thin atmosphere were detected, that data did not come from a detection of atmospheric chemicals.  A barren rock with a surface layer of material weathered from stellar irradiation, it reported, could explain the observations equally well as a thin atmosphere would.Read more

The Just-Approved European ARIEL Mission Will Be First Dedicated to Probing Exoplanet Atmospheres


The Ariel space telescope will explore the atmospheres of exoplanets. (Artist impression, ESA)

The European Space Agency (ESA) has approved the ARIEL space mission—the world’s first dedicated exoplanet atmosphere sniffer— to fly in 2028.

ARIEL stands for the “Atmospheric Remote-sensing Infrared Exoplanet Large-Survey mission.” It is a space telescope that can detect which atoms and molecules are present in the atmosphere of an exoplanet.

The mission was selected as a medium class mission in the ESA Cosmic Vision program; the agency’s decadal plan for space missions that spans 2015 – 2025.

One of the central themes for Cosmic Vision is uncovering the conditions for planet formation and the origins of life. This has resulted in three dedicated exoplanet missions within the same decadal plan. ARIEL will join CHEOPS (in the small class mission category) and PLATO (another medium class mission) in studying worlds beyond our own sun.

Yet ARIEL is a different type of telescope from the other exoplanet-focused missions. To understand why, we need to examine what properties we can observe of these distance exo-worlds.

Exoplanet missions can be broadly divided into two types. The first type are the exoplanet hunter missions that search the skies for new worlds.

These are spacecraft and instruments such as the NASA Kepler Space Telescope. Since it launched in 2009, Kepler has been an incredibly prolific planet hunter. The telescope has found thousands of planets, modeled their orbits and told us about the distribution of their sizes.

From Kepler, we have learnt that planet formation is common, that it can occur around stars far different from our own sun, and that these worlds can have a vast range of sizes and myriad of orbits quite unlike our own Solar System.


Current and future (or proposed) space missions with capacities to identify and characterize exoplanets.  The very productive CoRotT mission is, however, missing.  It searched for and found many exoplanets from 2006 to 2013.  (NASA,ESA: T. Wynne/JPL, composited by Barbara Aulicino)


However, the information Kepler is able to provide about individual planets is very limited. The telescope monitors stars for the tiny drop in light as the planet crosses (or “transits”) the star’s surface. From this, astronomers can measure the radius of the planet and its orbital period but nothing about the planet’s surface conditions.

The result is a little like knowing the number of students and distribution of grades in a particular school, but having no idea if the student who sits in the third row actually likes math.… Read more

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