![An artist impression of exoplanet LTT9779b orbiting its host star. The planet is around the size of Neptune and reflects 80 percent of the light shone on it.](https://cdn.arstechnica.net/wp-content/uploads/2023/07/Exoplanet_LTT9779_b_orbiting_its_host_star_pillars-800x450.png)
It has been about three a long time because the first confirmed exoplanet was discovered. In the next 30 years, using a wide range of telescopes and instruments on the bottom and in space, astronomers have cataloged greater than 5,000 planets around other stars.
As a part of this technique of scientific discovery, astronomers have confirmed that our Milky Way galaxy teems with billions of planets. They exist around many (if not most) stars, and so they are available all sizes and flavors. There are very large and really small planets and highly regarded and really cold ones. There are greater than a couple of that might harbor life as we understand it on Earth.
After this initial wave of discovery, powered by such NASA survey missions because the Kepler Space Telescope and the Transiting Exoplanet Survey Satellite, second-generation instruments like Europe’s small Cheops satellite have sought to characterize the character of those exoplanets. Launched lower than three years ago on a Soyuz rocket, the Cheops instrument has delivered some precious insights on planets orbiting other stars.
A really vivid planet
On Monday, within the journal Astronomy & Astrophysics, European scientists describe certainly one of these worlds that has a particularly high albedo, planet LTT9779 b. An albedo is solely the quantity of sunshine reflected by a planet back into space. Earth reflects about 30 percent of the Sun’s light into space, whereas Venus, with its thick clouds, reflects 75 percent of its light.
The planet LTT9779 b, which is positioned around a Sun-sized star about 260 light-years from Earth, has the next albedo than that of Venus, about 80 percent. One big query for scientists is how the planet could reflect a lot light, because it’s hot enough that it shouldn’t have any clouds. It is because it’s positioned extremely near its star, orbiting once every 19 hours.
It is a pretty hellish planet with a radius barely larger than that of Neptune (and 4.7 times that of Earth) and a surface temperature on the order of about 2,000° Celsius. Based upon their observations of other exoplanets, astronomers were surprised to seek out a Neptune-sized world so near its star. Before, only large worlds (similarly sized to Jupiter) or much smaller worlds have been found so near stars. Accordingly, the environment near stars has been characterised as a “hot Neptune desert.”
But with the invention of planet LTT9779 b in 2020, astronomers had themselves a mystery. Here was a ‘hot Neptune’ in a hot Neptune desert. And it was extremely vivid, the shiniest exoplanet ever observed.
Mystery explained
These were the sorts of mysteries that missions resembling Cheops were designed to resolve with their ability to not survey the whole night sky but to focus in on a single world for an prolonged time frame.
On this case, Cheops observed the planet because it transited behind its star on 10 different occasions. During these transits, the telescope measured the combined light coming from each the star and planet to watch the difference and infer the intrinsic brightness of LTT9779 b.
From this data, scientists have developed a theory that the planet started off as a gas giant but has been losing mass over time. It should have an environment composed of silica material, like glass, together with titanium. Effectively, then, the atmosphere has a mirror-like composition.
No clouds should give you the chance to exist on the surface temperatures on a world like this, estimated at about 2,000° Celsius—even those manufactured from metal and glass.
“It was really a puzzle until we realized we must always take into consideration this cloud formation in the identical way as condensation forming in a rest room after a hot shower,” said Vivien Parmentier, a researcher on the Observatory of Côte d’Azur (France) and co-author of the study. “To steam up a rest room, you possibly can either cool the air until water vapor condenses, or you possibly can keep the new water running until clouds form since the air is so saturated with vapor that it simply can’t hold any more.”
Within the case of LTT9779 b, he said, the planet can form metallic clouds since the atmosphere is super-saturated with silicate and metal vapors. Because of this, quite literally, it rains titanium on this weird world.
Additional information may very well be gleaned about this shiny latest object if other space-based telescopes, resembling Hubble and James Webb, make similar observations concerning the planet and its atmosphere.