May 28, 2023

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The James Webb telescope detects a dust storm on a distant world

  • By Jonathan Amos
  • BBC Science Correspondent

image source, NASA/ESA/CSA/J Olmsted (STScI)

photo caption,

VHS 1256b artwork: The planet takes about 10,000 years to orbit its parent star

A raging dust storm has been spotted on a planet outside our solar system for the first time.

It was discovered on an exoplanet known as VHS 1256b, which is about 40 light-years from Earth.

It took the remarkable capabilities of the new James Webb Space Telescope (JWST) to make the discovery.

Dust particles are silicates – small grains composed of silicon and oxygen, which form the basis of most rock minerals.

But the storm Webb discovered is not the same phenomenon that would occur in an arid desert region of our planet. It’s more of a rock mist.

“It’s kind of like if you took grains of sand, but much finer. We’re talking silicate grains the size of smoke particles,” explained Professor Beth Beller of the University of Edinburgh and the Royal Observatory in Edinburgh, UK.

She told BBC News: “This is what the clouds on VHS 1256b would be like, but it’s much hotter. This planet is a hot, young body. The temperature of the upper cloud is probably similar to that of a candle flame.”

VHS 1256b was first identified by the UK-developed Vista telescope in Chile in 2015.

It is the so-called “super Jupiter” – a planet similar to the gas giant in our solar system, but much larger, perhaps 12 to 18 times the mass.

It orbits a couple of stars at a great distance – about four times the distance that Pluto is from our Sun.

Previous observations of VHS 1256b showed it to have a reddish appearance, indicating that it may have dust in its atmosphere. Webb’s study confirms this.

“It’s fascinating because it shows how different clouds can be on a planet other than the water vapor clouds we’re familiar with on Earth,” said Professor Beller.

“We see carbon monoxide and methane in the atmosphere, which indicates that it is hot and turbulent, with material being pulled up from the depths.

“It’s possible that there are multiple layers of silicate grains. The ones we’re seeing are some very fine grains high up in the atmosphere, but there could be larger grains deeper in the atmosphere.”

Telescopes have previously detected silicates in so-called brown dwarfs. These are basically star-like objects that fail to ignite properly. But this is a first for a planet-sized object.

To make the discovery, Webb used the Medium Infrared Spectrometer (Miri), built in part in the UK, and the Near Infrared Spectrometer (NirSpec).

They haven’t taken pretty pictures of the planet, at least not in this case. What they did was decompose the light coming from VHS 1256b into its component colors as a way to characterize the composition of the atmosphere.

“JWST is the only telescope that can measure all of these molecular and dust properties together,” said Merry co-principal investigator Professor Gillian Wright, who directs STFC UK’s Astronomy Technology Center in Edinburgh.

“The dynamic image of the atmosphere of VHS 1256b provided by this study is a prime example of the detections enabled by the advanced capabilities of Miri and NirSpec together.”

JWST’s primary mission is to observe the pioneer stars and galaxies that first shone bright only a few hundred million years after the Big Bang. But the main goal is to investigate exoplanets. At Miri and NirSpec, it has the tools to study its atmospheres in unprecedented detail.

Scientists hope they will even be able to find out if some exoplanets have conditions suitable for hosting life.

James Webb is a collaborative project of the US, European and Canadian space agencies. It was launched in December 2021 and is considered the successor to the Hubble Space Telescope.

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