Researchers have found an intensely hot exoplanet with metallic clouds that rain titanium. The strange world, rather prosaically known as LTT9779b, is the brightest planet discovered outside the solar system.
LTT9779b, some 260 light years from Earth, is the brightest planet known outside the solar systemImage: Ricardo Ramírez Reyes/Universidad de Chile/dpa/picture alliance
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Scientists on Monday announced the discovery of a scorching world with temperatures of up to 2,000 degrees Celsius (over 3,600 degrees Fahrenheit), where glass-like silicate and metals boil into clouds.
The brightest planet to be discovered outside our solar system to date, LTT9779b has been described by researchers as "a planet that shouldn't exist."
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What we know about the planet
The planet — about the size of Neptune— lies close to its star, orbiting it every 19 hours. It's the star-facing side of the planet that has a temperature of about 2,000 degrees Celsius.
LTT9779b — some 260 light years from Earth— was initially discovered by NASA in 2020, but the latest discoveries were made in a follow-up study by the European Space Agency's exoplanet-spotting Cheops space telescope. Researchers found the planet was a conundrum from the very beginning because of its high reflectiveness, also called albedo in scientific terminology.
Most planets and moons have a low albedo because they absorb, rather than reflect, light. Exceptions include ice worlds like Jupiter's satellite Europa or cloudy ones like Venus.
Although it reflects "like a mirror," the researchers said LTT9779b seemed too hot for clouds, even if they were made of metal or glass. However, it turned out that the atmosphere of LTT9779b is so saturated with metals and silicate vapors that droplets do form — including raindrops composed of titanium.
"To steam up a bathroom you can either cool the air until water vapor condenses, or you can keep the hot water running until clouds form because the air is so saturated with vapor that it simply can't hold anymore," said Vivien Parmentier, co-author of a study in the journal Astronomy and Astrophysics.
The latest images from the James Webb Space Telescope
The James Webb Space Telescope has been in action since July 2022. The latest images continue to stun the world and help advance our understanding of the universe.
Image: NASA, ESA, CSA, K. Lawson (GSFC), J. Schlieder (GSFC), A. Pagan (STScI)
Dusty disks of a red dwarf star
A dusty debris disk surrounds red dwarf star AU Mic, 32 light-years away from Earth. The star is marked in white. Debris disks are continuously replenished by collisions of solid dust clumps called planetesimals. The two images were taken using different wavelengths. In the blue image, the disk appears to be shorter, indicating fine dust scatters shorter-wavelength blue light.
Image: NASA, ESA, CSA, K. Lawson (GSFC), J. Schlieder (GSFC), A. Pagan (STScI)
Webb reveals previously shrouded newborn stars
Astronomers dug deep into the data from this near-infrared image of the star-forming region in the constellation Carina known as the cosmic cliffs. Webb’s infrared camera penetrated clouds of dust, allowing astronomers to discover signs of two dozen infant stars.
Image: NASA, ESA, CSA AND STSCI
Hydrogen recycling in Stephan’s Quintet
Astronomers discovered a recycling plant for hydrogen gas in Stephan’s Quintet, 270 million light-years away. In the left image, a giant cloud of cold hydrogen gas (green) is stretched into a warm tail of hydrogen over and over again. In the center, a high-speed collision feeds warm gas into cold gas clouds. On the right, hydrogen gas has collapsed, forming what may be a small dwarf galaxy.
Image: ALMA (ESO/NAOJ/NRAO)/JWST/ P. Appleton (Caltech), B.Saxton (NRAO/AUI/NSF)
An exoplanet without an atmosphere
Exoplanet LHS 475 b is almost exactly the same size as Earth. Webb's near-infrared spectograph found the planet has no atmosphere. The white data dots are in a pattern consistent with a planet that has no atmosphere (yellow line). If the planet had a pure carbon dioxide atmosphere, the dots would follow the purple line, if it had a pure methane atmosphere it would follow the green line.
Image: ILLUSTRATION: NASA, ESA, CSA, Leah Hustak (STScI)/SCIENCE: Kevin B. Stevenson (APL), Jacob A. Lustig-Yaeger (APL), Erin M. May (APL), Guangwei Fu (JHU), Sarah E. Moran (University of Arizona)
Webb captures galaxy in much higher detail compared to Hubble
These two images show the same galaxy, EGS23205, about 11 billion years ago. In the left image, the Hubble Space Telescope captured a fuzzy shot of the galaxy. But the James Webb Telescope image on the right reveals a spiral galaxy with a clear stellar bar.
Image: NASA/CEERS/University of Texas at Austin
Ancient 'green pea' galaxies
The trio of galaxies circled here are "green pea" galaxies. They are rare, small galaxies found much closer to home. These images show the galaxies as they existed when the universe was in its first billion years of its current age of 13.8 billion years.
Image: NASA, ESA, CSA, and STScI
Star formation in dusty ribbons
This cluster of stars, named NGC 346, lies within a nebula. That's a place where stars and planets are formed in clouds packed with dust and hydrogen. The pinker plumes are energized hydrogen as hot as 10,000 degrees Celsius (18,000 degrees Fahrenheit), while the more orange gas represents denser, colder hydrogen at around -200 Celsius.
Image: NASA, ESA, CSA, M. Meixner, G. DeMarchi, O. Jones, L. Lenkic, L. Chu, A. Pagan (STScI)
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"Similarly, LTT9779 b can form metallic clouds despite being so hot because the atmosphere is oversaturated with silicate and metal vapors."
Hot Neptune puzzle
Another curiosity was that planets the size of LTT9779b that have an atmosphere shouldn't exist so close to their sun — normally the outer layer would simply burn away.
"It's a planet that shouldn't exist," said Parmentier. "We expect planets like this to have their atmosphere blown away by their star, leaving behind bare rock."
The answer was partly explained by the high reflectivity, allowing LTT9779b to exist in what scientists term a "hot Neptune desert."
"The clouds reflect light and stop the planet from getting too hot and evaporating," said paper co-author Sergio Hoyer. "Meanwhile, being highly metallic makes the planet and its atmosphere heavy and harder to blow away."
Exploring extrasolar planets with CHEOPS
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To determine the properties of the planet, scientists looked at differences in light when the planet was technically "visible" and when it was eclipsed by its own star. Only with the precision of the Cheops telescope — focused on discovering new exoplanet systems — was it possible to measure the data the team needed this time around.
The scientists hope to follow up with other data from the Hubble and James Webb space telescopes, which they say will provide a fuller picture.
