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Using data from the James Webb Space Telescope, a group of scientists has gotten the best-ever look at a distant planet\u2019s surface.<\/p>\n
Astronomers have found thousands of worlds in faraway star systems, but one of the questions that\u2019s been hardest to answer is the one that immediately jumps to any human mind: What does the planet look like?<\/p>\n
By analyzing subtle changes in light, researchers found the planet Kua\u2019kua\u2014which orbits a small star in the constellation Indus\u2014has a dark, solid surface, possibly made of basalt or a related type of rock. It probably doesn\u2019t have plate tectonics<\/a> like Earth does, and very little if any atmosphere.<\/p>\n In addition to providing a glimpse into the planet\u2019s physical appearance, these factors can help us understand the different types of worlds that exist in the universe. They can also narrow the search for potentially habitable planets by revealing whether they\u2019ve ever had water, active geology, or other conditions that might support life.<\/p>\n \u201cThis technique can tell us about how the rocks on this planet formed and what processes shaped it over the planet\u2019s lifetime,\u201d says Brandon Coy, a graduate student at University of Chicago and coauthor on the paper. \u201cThere\u2019s a lot of cool things we can do with this data.\u201d<\/p>\n The program\u2019s primary investigator was Laura Kreidberg of the Max Planck Institute for Astrophysics, and the first author was Sebastian Zieba of the Harvard\/Smithsonian Center for Astrophysics.<\/p>\n Though we now know of more than 6,000 exoplanets, they\u2019re generally too small and far away to be directly looked at, even with the most powerful telescopes. Instead, scientists must tease out clues about these planets with clever workarounds.<\/p>\n One of these techniques is known as the \u201csecondary eclipse technique.\u201d In this method, you map the light coming from the system, then wait for the planet to dip behind the star as part of its regular orbit. The difference between the readings is the light from the planet itself. Scientists can use this data to get a sense of the molecules in the planet\u2019s atmosphere and other details.<\/p>\n This technique works well for big gas planets, similar to Jupiter, that are close to their stars.<\/p>\n \u201cUnfortunately, the smaller worlds are harder to see,\u201d says Edwin Kite, associate professor of geophysical sciences at UChicago and a study coauthor, \u201cbut they\u2019re the ones most relevant to fragile carbon-based beings like us.\u201d<\/p>\n Luckily, scientists have a powerful new tool on their side: \u201cThe James Webb Space Telescope has really opened up a new era in characterizing these rocky planets,\u201d says Coy.<\/p>\n Kite, Coy, and the team used the telescope to focus on a planet known as Kua\ua78ckua, or LHS 3844 b by its formal scientific name, which is 48 light-years away from Earth, meaning it would take 48 years to travel there even at the speed of light. Kua\u2019kua is about twice the mass of Earth, but is much closer to its sun and zips around it faster\u2014its \u201cyear,\u201d the time it takes to complete a full trip around its host star, is the equivalent of 0.5 Earth days.<\/p>\n By analyzing data from three secondary eclipses with different models, they were able to put together a striking amount of detail about the planet.<\/p>\n Kua\u2019kua\u2019s surface appears to be very dark, most likely made up of basalt or similar rock\u2014much like the rock you might see in Iceland or Hawaii. The planet is probably covered in a dark, weathered powder, as our moon and Mercury are. And there\u2019s no signature in the readings for an atmosphere with carbon dioxide, or even a sulfurous one belched from volcanoes.<\/p>\n The color is of particular interest because a lighter-colored surface might have indicated a granite crust, which on Earth, is made in the presence of water and could also have indicated the presence of plate tectonics. It\u2019s been theorized that Earth\u2019s plate tectonics are key to keeping the planet\u2019s climate stable and habitable for life, so scientists are keen to understand how common they might be in the other planets of the universe.<\/p>\n Combining the new findings with data from previous missions paints a picture of the planet: a dark, dry, rocky, unmoving surface, with a thin atmosphere if any at all. One side of the planet always faces its star, so that side is constantly cooked by the sun to 1,300\u00baF and the other side is shrouded in darkness.<\/p>\n You probably aren\u2019t putting Kua\u2019kua on your vacation shortlist. But each planet we learn about tells us more about how planets form\u2014and by extension, how to look for planets friendlier to Earth life.<\/p>\n \u201cWe\u2019ve only got four rocky planets in our solar system, and they\u2019re very diverse. Some have atmospheres and some don\u2019t, one is habitable and three aren\u2019t\u2014and one used to be habitable. So we just don\u2019t have a big enough sample size to understand how these objects operate,\u201d says Kite.<\/p>\n \u201cThe more we learn about these other planets, the better we understand the ingredients that make for stable, habitable planets.\u201d<\/p>\n As for Kua\u2019kua, plans are underway to use the Webb Telescope to try to get a snapshot of how rough the planet\u2019s surface is and other details\u2014which would be another first.<\/p>\n