NASA finds strange alien planet hidden away from our solar system


NASA has found a strange alien planet sitting outside our solar system.

The world is cool and small: two characteristics that make it very strange indeed for scientists to find.

The small planet known as HD 21749b is the third planet to be found by TESS, NASA's new planet-hunting telescope. It revolves around its star in a long orbit, taking a relatively slow 36 days.

Despite this proximity, it's pretty cool around 300 degrees Fahrenheit.

As such, it could be a very important way for scientists to find out about these relatively small and temperate worlds.

"It's the coolest planet we know around such a bright star," says Diana Dragomir, a postdoc at the Kavli Institute of Astrophysics and Space Research at MIT who led the new discovery.

"We know a lot about atmospheres of hot planets, but since it is very difficult to find small planets that orbit farther from their stars and therefore are cooler, we can not learn much about these smaller, colder planets. But here we were lucky and we took this one, and now we can study it in more detail. "

Even though it is called small by the scientists who found it, the world is still huge compared to us: it is about three times our size and 23 times more massive. This puts it in the category of a "sub-Neptune", and means that it would be the first planets about the size of Earth to be found by TESS.

But it's unlikely to look much like our own planet. It is probably made of gas like Neptune or Uranus, although something much denser than its atmospheres.

"We think this planet would not be as gaseous as Neptune or Uranus, which are mostly hydrogen and very swollen," says Dragomir. "The planet probably has a water density or a thick atmosphere."

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