![]() ![]() In general, however, Macdonald found that "the planets with the highest globally averaged surface temperatures and the most atmospheric water vapor have oceans in the center of their daysides and land on the cold parts of the planet." Alien super-Earths may get a habitability boost from hydrogen-rich atmospheres James Webb Space Telescope will study two strange 'super-Earths' Gallery: James Webb Space Telescope's 1st photos "So the land has a desert climate," Macdonald told. This is because the presence of more land means there is less surface water to evaporate into the atmosphere, which also results in less precipitation. In the simulation, planets with a similar dayside fraction of land, whether in a central substellar continent or around a substellar ocean, saw average surface temperatures increase by up to 36 F (20 C).įurthermore, the greater the amount of land, the hotter the dayside and the drier the planet's atmosphere. The models showed that the average global temperature on a tidally locked world depends more on the amount of land than on the location of the land. The amount of land and ocean in each configuration was then varied to see how it would affect the planet's climate. With fellow astronomers at the University of Toronto, Macdonald modeled such a hypothetical world in two configurations: one with a circular continent at the substellar point (directly beneath the star) on the dayside surrounded by ocean, and one with a circular ocean at the substellar point surrounded by land. Related: Imagining early Earth as an exoplanet can help us search for alien life, scientists say These planets orbit their star in a matter of days, which makes them prone to becoming gravitationally locked with their star. This so-called tidal locking does not mean a planet's near-side hemisphere is in constant daylight and the far-side is under constant night, however.Ĭonsequently, the habitability of such a planet also depends on the planet's ability to redistribute heat from the dayside to the nightside so that conditions don't become too warm or too cold. Rocky planets orbiting red dwarf stars are particularly susceptible to tidal locking, because red dwarf systems tend to be scaled down and the planets are often very close to their stars.ĭespite their proximity to their star, these worlds can be in the habitable zone - the right distance where it can host liquid water on its surface - because red dwarfs are cool, with surface temperatures of about 6,300 degrees Fahrenheit (3,500 degrees Celsius), or 3,600 F (2,000 C) cooler than the sun. It is the same phenomenon that keeps the moon showing the same face toward Earth. As such, the planet rotates at a rate that means it always keeps the same face pointed toward its star. A tidally locked world is in synchronous rotation, meaning it takes the same amount of time to spin on its axis as it does to orbit its star. ![]()
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