Scientists have found two rocky, possibly Earth-like inner planets orbiting a star called Teegarden’s Star just 12.59 light years from our solar system that are in precisely the right place for any inhabitants to see Earth move across the Sun. Are we being watched?

What and where is Teegarden’s Star?

Teegarden’s Star, a red dwarf (a relatively cool and old star) was discovered in 2003, and it's so close to the solar system that astronomers have been able to detect it moving. It's in the constellation of Aries, close to the easy-to-spot Pleiades star cluster that's best viewed in winter in the northern hemisphere. However, Teegarden’s Star itself can only be seen in large telescopes.

One of the smallest known stars, Teegarden’s Star is only about 2,700 °C warm and about ten times lighter than the Sun.

Does Teegarden’s Star have planets?

Two, at least, according to an international research team led by the University of Göttingen in Germany. Researchers there discovered two new Earth-like planets after studying Teegarden’s Star for about three years.“The two planets resemble the inner planets of our solar system,” explains lead author Mathias Zechmeister of the Institute for Astrophysics at the University of Göttingen. “They are only slightly heavier than Earth and are located in the so-called habitable zone, where water can be present in liquid form.”

Are there any more planers around Teegarden’s Star? 

There are probably more. “Many stars are apparently surrounded by systems with several planets,” says co-author Professor Stefan Dreizler of the University of Göttingen.

How could the planets around Teegarden’s Star 'see' us? 

It's a hypothesis, but this star system is located at a very "special place in the sky." From Teegarden’s Star it would be possible to see the planets of the solar system passing in front of the Sun. “An inhabitant of the new planets would have the opportunity to view the Earth using the transit method,” says Professor Ansgar Reiners of the University of Göttingen, one of the scientific directors of the project. Mostly, exoplanets are discovered by astronomers using the "transit method". The planets have to pass visibly in front of the star and darken it for a moment, which only happens in a very small fraction of all planetary systems. 

However, the CARMENES project, which this research was part of, used a different technique to find the two planets around Teegarden’s Star.

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