exoplanets

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A new scientific report suggests that there are 29 planets in our cosmic neighbourhood where alien life could potentially see and hear evidence of humans on Earth, based on humanity’s own techniques for studying the universe.

The report was published Wednesday by two New York-based astronomers in the journal Nature, in an effort to narrow down our own search for alien life among the stars. It doesn’t attempt to prove that anyone is actually out there listening, or that they’d want to hear from us if they were. The report simply tries to determine where our most likely alien audiences would be.

The authors assume that aliens would be able to spot Earth by seeing its faint shadow as it transits in front of the sun — a technique that we’ve used to find many Earth-like worlds to date.

“One way we find planets is if they block out part of the light from their host star,” Lisa Kaltenegger, director of the Carl Sagan Institute at Cornell University and co-author of the article, told The Guardian. “We asked, ‘Who would we be the aliens for, if somebody else was looking?’ There is this tiny sliver in the sky where other star systems have a cosmic front seat to find Earth as a transiting planet.”

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This artist's concept is of a Jupiter-mass planet orbiting the nearby star Epsilon Eridani. Located 10.5 light-years away, it is the closest known exoplanet to our solar system. The planet is in an elliptical orbit that carries it as close to the star as Earth is from the Sun, and as far from the star as Jupiter is from the Sun.

Epsilon Eridandi is a young star, only 800 million years old. It is still surrounded by a disk of dust that extends 20 billion miles from the star. The disk appears as a linear sheet of reflecting dust in this view because it is seen edge-on from the planet's orbit, which is in the same plane as the dust disk.

The planet's rings and satellites are purely hypothetical in this view, but plausible. As a gas giant, the planet is uninhabitable for life as we know it. However, any moons might have conditions suitable for life.

Astronomers determined the planet's mass and orbital tilt in 2006 by using Hubble to measure the unseen planet's gravitational pull on the star as it slowly moved across the sky. Evidence for the planet first appeared in 2000 when astronomers measured a telltale wobble in the star.

Source: nasa.gov