Tag: NASA Ames Research Center

The James Webb Space Telescope Begins Looking at Exoplanets

 

Artist rendering of Gliese (GJ) 436 b  is a Neptune-sized planet that orbits a red dwarf  star.  Red dwarfs are cooler, smaller, and less luminous than the Sun. The planet completes one full orbit around its parent star in just a little over 2 days. It is made, scientists say, of extremely hot ice.  (NASA/JPL-Caltech/UCF)

The James Webb Space Telescope has begun the part of its mission to study the atmospheres of 70 exoplanets in ways, and at a depth, well beyond anything done so far.

The telescope is not likely to answer questions like whether there is life on distant planet — its infrared wavelengths will tell us about the presence of many chemicals in exoplanet atmospheres but little about the presence of the element most important to life on Earth, oxygen.

But it is nonetheless undertaking a broad study of many well-known exoplanets and is likely to produce many tantalizing results and suggest answers to central questions about exoplanets and their solar systems.

Many Worlds has earlier looked at the JWST “early release” program, under which groups are allocated user time on the telescope under the condition that they make their data public quickly.  That way other teams can understand better how JWST works and what might be possible.

Another program gives time to scientists who worked on the JWST mission and on its many instruments.  They are given guaranteed time as part of their work making JWST as innovative and capable as it is.

One of the scientist in this “guaranteed time observations program” is Thomas Greene, an astrophysicist at NASA Ames Research Center.  The groups he leads have been given 215 hours of observing time for this first year (or more) of Cycle 1 of JWST due to his many contributions to the JWST mission as well as his history of accomplishments.

In a conversation with Greene, I got a good sense of what he hopes to find and his delight at the opportunity.  After all, he said, he has worked on the JWST idea and then mission since 1997.

“We will be observing a diverse sample of exoplanets to understand more about them and their characteristics,” Greene said.  “Our goal is to get a better understanding of how exoplanets are similar to and different from those in our solar system.”

And the JWST spectra will tell them about the chemistry, the composition and the thermal conditions on those exoplanets, leading to insights into how they formed, diversified and evolved into planets often so unlike our own.Read more

Cloudy, With a Chance of Iron Rain

Analysis of data from the Kepler space telescope has shown that roughly half of the dayside of the exoplanet Kepler-7b is covered by a large cloud mass. Statistical comparison of more than 1,000 atmospheric models show that these clouds are most likely made of Enstatite, a common Earth mineral that is in vapor form at the extreme temperature on Kepler-7b. These models varied the altitude, condensation, particle size, and chemical composition of the clouds to find the right reflectivity and color properties to match the observed signal from the exoplanet. Courtesy of NASA (edited by Jose-Luis Olivares/MIT)

Many exoplanets being discovered are covered with thick clouds, offering an opportunity to analyze their compositions but hiding the lower atmosphere and surface from measurement and view.  This artist rendering of Kepler-7b is based Kepler Space Telescope data and shows that half of the day-side of the planet is covered by a large cloud.  Statistical comparison of more than 1,000 atmospheric models show that these clouds are most likely made of enstatite, a common Earth mineral that is in vapor form at the extreme temperature on Kepler-7b. (NASA/ edited by Jose-Luis Olivares/MIT)

 

From an Earth-centric point of view, rain of course means falling water.  We can have storms with falling dust — I experienced a few of those while a reporter in India — but rain is pretty much exclusively H2O falling from the clouds. But as the study of exoplanets moves aggressively into the realm of characterizing these distant planets after they are detected, the concepts of rain and clouds are changing rapidly.

We already know that it rains methane on the moon Titan, sulfuric acid on Venus and ammonia, helium and, yes, water, on Jupiter and Saturn.  Some have even posited that carbon — in the form of graphite and then diamonds — falls from the “clouds” of Saturn and Jupiter, but the eye-catching view is widely disputed.

Now the clouds of exoplanets large and small are being rigorously scrutinized not only because they can potentially tell researchers a great deal about the planets below,  but also because especially thick clouds have become a major impediment to learning what many exoplanet atmospheres and even surfaces are made of.  Current telescopes and spectrometers just can’t see much through many of the thick ones.

Here’s why:  The chemical compositions of many exo-planetary clouds are so profoundly different from what is found in our solar system.  Hot gas exoplanets, for instance, tend to have clouds of irons and silicates — compounds that are in a gas form on the surface (such as it is), then rise into the atmospheres and form into grain-like solids when they get higher and colder.  For some smaller exoplanets, the composition tends to be salts such as zinc sulfide and potassium chloride.

The process of identifying the make-up of different clouds is very much a work in progress, as is an understanding of how thick or how patchy the clouds may be.

The light curve for the planet studied, which is some four times larger than Jupiter, shows differences in brightness as the planet rotates.

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