Methane and water vapor found on an exoplanet

Newswand: NASA’s James Webb Space Telescope observed methane gas and water vapor on exoplanet WASP-80 b as it passed in front of and behind its host star.

Photo credit: NASA

While water vapor has been detected in over a dozen planets to date, until recently methane – a molecule found in abundance in the atmospheres of Jupiter, Saturn, Uranus, and Neptune within our solar system – has remained elusive in the atmospheres of transiting exoplanets when studied with space-based spectroscopy.

Taylor Bell from the Bay Area Environmental Research Institute (BAERI), working at NASA’s Ames Research Center in California’s Silicon Valley, and Luis Welbanks from Arizona State University said, “With a temperature about 825 kelvins (about 1,025 degrees Fahrenheit), WASP-80 b is what scientists call a “warm Jupiter.” WASP-80 b goes around its red dwarf star once every three days and is situated 163 light-years away from us in the constellation Aquila.

Using the transit method, they observed the system when the planet moved in front of its star from our perspective, causing the starlight we see to dim a bit. It’s kind of like when someone passes in front of a lamp and the light dims. During this time, a thin ring of the planet’s atmosphere around the planet’s day/night boundary is lit up by the star, and at certain colors of light where the molecules in the planet’s atmosphere absorb light, the atmosphere looks thicker and blocks more starlight, causing a deeper dimming compared to other wavelengths where the atmosphere appears transparent.

Meanwhile, using the eclipse method, they observed the system as the planet passed behind its star from our perspective, causing another small dip in the total light we received. All objects emit some light, called thermal radiation, with the intensity and color of the emitted light depending on how hot the object is. Just before and after the eclipse, the planet’s hot dayside is pointed toward us, and by measuring the dip in light during the eclipse we were able to measure the infrared light emitted by the planet. For eclipse spectra, absorption by molecules in the planet’s atmosphere typically appear as a reduction in the planet’s emitted light at specific wavelengths. Also, since the planet is much smaller and colder than its host star, the depth of an eclipse is much smaller than the depth of a transit.

The initial observations they made needed to be transformed into something called a spectrum; this is essentially a measurement showing how much light is either blocked or emitted by the planet’s atmosphere at different colors (or wavelengths) of light. They interpreted spectrum using two kinds of models to simulate what the atmosphere of a planet under such extreme conditions would look like. The first type of model is entirely flexible, trying millions of combinations of methane and water abundances and temperatures to find the combination that best matches our data. The second type, called ‘self-consistent models,’ also explores millions of combinations but uses our existing knowledge of physics and chemistry to determine the levels of methane and water that could be expected. Both model types reached the same conclusion: a definitive detection of methane.

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Water vapor, sulfur dioxide, silicate and sand clouds found on an exoplanet

Newswand: A team of European astronomers, co-led by researchers from the Institute of Astronomy, KU Leuven, with the help of James Webb Space Telescope, have discovered water vapour and sulfur dioxide, silicate sand clouds on an exoplanet WASP- 107b. These particles reside within a dynamic atmosphere that exhibits vigorous transport of material. The results of the study appeared in the prestigious journal Nature.

Phto credit: Klaas Verpoest, Johan Van Looveren, Leen Decin

Astronomers worldwide are harnessing the advanced capabilities of the Mid-Infrared Instrument (MIRI) aboard the James Webb Space Telescope (JWST) to conduct groundbreaking observations of exoplanets—planets orbiting stars other than our own Sun.

One of these fascinating worlds is WASP-107b, a unique gaseous exoplanet that orbits a star slightly cooler and less massive than our Sun. Its mass is similar to that of Neptune but its size is much larger than that of Neptune, almost approaching the size of Jupiter. This characteristic renders WASP-107b rather ‘fluffy’ when compared to the gas giant planets within our solar system. The fluffiness of this exoplanet enables astronomers to look almost 50 times deeper into its atmosphere compared to the depth of exploration achieved for a solar-system giant like Jupiter.

The team of European astronomers took full advantage of the remarkable fluffiness of this exoplanet, enabling them to look deep into its atmosphere. This opportunity opened a window into unravelling the complex chemical composition of its atmosphere. The reason behind this is quite straightforward: the signals, or spectral features, are far more prominent in a less dense atmosphere compared to a more compact one. Their recent study, now published in Nature, reveals the presence of water vapour, sulfur dioxide (SO2), and silicate clouds, but notably, there is no trace of the greenhouse gas methane (CH4).

These detections provide crucial insights into the dynamics and chemistry of this captivating exoplanet. First, the absence of methane hints at a potentially warm interior, offering a tantalising glimpse into the movement of heat energy in the planet’s atmosphere. Secondly, the discovery of sulfur dioxide (known for the odor of burnt matches), was a major surprise. Previous models had predicted its absence, but novel climate models of WASP-107b’s atmosphere now show that the very fluffiness of WASP-107b accommodates the formation of sulfur dioxide in its atmosphere. Even though its host star emits a relatively small fraction of high-energy photons due to its cooler nature, these photons can reach deep into the planet’s atmosphere thanks to its fluffy nature. This enables the reactions required to produce sulfur dioxide to occur.

But that’s not all they’ve observed. Both the spectral features of sulfur dioxide and water vapour are significantly diminished compared to what they would be in a cloudless scenario. High-altitude clouds partially obscure the water vapour and sulfur dioxide in the atmosphere. While clouds have been inferred on other exoplanets, this marks the first instance where astronomers can definitively identify the chemical composition of these clouds. In this case, the clouds consist of small silicate particles, a familiar substance for humans found in many parts of the world as the primary constituent of sand.

In contrast to Earth’s atmosphere, where water freezes at low temperatures, in gaseous planets reaching temperatures around 1000 degrees Celsius, silicate particles can freeze out to form clouds. However, in the case of WASP-107b, with a temperature of around 500 degrees Celsius in the outer atmosphere, traditional models predicted that these silicate clouds should be forming deeper within the atmosphere, where temperatures are substantially higher. In addition, sand clouds high up in the atmosphere rain out. How is it then possible that these sand clouds exist at high altitudes and continue to endure?

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A seven planets system found

Newswand: A system of seven sweltering planets has been revealed by continued study of data from NASA’s retired Kepler space telescope: Each one is bathed in more radiant heat from their host star per area than any planet in our solar system.

Photo credit: NASA/Daniel Rutter

Also unlike any of our immediate neighbors, all seven planets in this system, named Kepler-385, are larger than Earth but smaller than Neptune. It is one of only a few planetary systems known to contain more than six verified planets or planet candidates. The Kepler-385 system is among the highlights of a new Kepler catalog that contains almost 4,400 planet candidates, including more than 700 multi-planet systems.

“We’ve assembled the most accurate list of Kepler planet candidates and their properties to date,” said Jack Lissauer, a research scientist at NASA’s Ames Research Center in California’s Silicon Valley and lead author on the paper presenting the new catalog. “NASA’s Kepler mission has discovered the majority of known exoplanets, and this new catalog will enable astronomers to learn more about their characteristics.”

At the center of the Kepler-385 system is a Sun-like star about 10% larger and 5% hotter than the Sun. The two inner planets, both slightly larger than Earth, are probably rocky and may have thin atmospheres. The other five planets are larger – each with a radius about twice the size of Earth’s – and expected to be enshrouded in thick atmospheres.

The ability to describe the properties of the Kepler-385 system in such detail is testament to the quality of this latest catalog of exoplanets. While the Kepler mission’s final catalogs focused on producing lists optimized to measure how common planets are around other stars, this study focuses on producing a comprehensive list that provides accurate information about each of the systems, making discoveries like Kepler-385 possible.

The new catalog uses improved measurements of stellar properties and calculates more accurately the path of each transiting planet across its host star. This combination illustrates that when a star hosts several transiting planets, they typically have more circular orbits than when a star hosts only one or two.

Kepler’s primary observations ceased in 2013 and were followed by the telescope’s extended mission, called K2, which continued until 2018. The data Kepler collected continues to reveal new discoveries about our galaxy. After the mission already showed us there are more planets than stars, this new study paints a more detailed picture of what each of those planets and their home systems look like, giving us a better view of the many worlds beyond our solar system.

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