Skip to main content

Astronomers identify locations from which aliens could spot Earth

Earth visible from distant exoplanets

The search for intelligent life beyond Earth has most often focused on where we could find potential signs of life beyond our solar system. But two astronomers from Cornell have investigated a different way to approach this issue — looking at how visible Earth is from distant exoplanets from which aliens might be searching for us.

Recommended Videos

One way in which astronomers here on Earth search for exoplanets is using a technique called the transit method. This is where they observe distant stars and look for periodic dips in their brightness which indicate a planet passing between us and them.

Please enable Javascript to view this content

“Let’s reverse the viewpoint to that of other stars and ask from which vantage point other observers could find Earth as a transiting planet,” lead author Lisa Kaltenegger explained. “If observers were out there searching, they would be able to see signs of a biosphere in the atmosphere of our Pale Blue Dot,” she said, “And we can even see some of the brightest of these stars in our night sky without binoculars or telescopes.”

Cornell astronomer Lisa Kaltenegger and Lehigh University’s Joshua Pepper have identified 1,004 main-sequence stars – similar to our sun – that might contain Earth-like planets in their own habitable zones within about 300 light-years of here, which should be able to detect Earth’s chemical traces of life.
Cornell astronomer Lisa Kaltenegger and Lehigh University’s Joshua Pepper have identified 1,004 main-sequence stars – similar to our sun – that might contain Earth-like planets in their own habitable zones within about 300 light-years of here, which should be able to detect Earth’s chemical traces of life. John Munson/Cornell University

The new research aimed to identify which distant planets would be able to detect the presence of Earth using the transit technique, and the researchers came up with a list of the 1,000 nearest stars which could host planets from which Earth could be spotted.

“Only a very small fraction of exoplanets will just happen to be randomly aligned with our line of sight so we can see them transit,” co-author Joshua Pepper said. ”But all of the thousand stars we identified in our paper in the solar neighborhood could see our Earth transit the sun, calling their attention.”

This work could help select potential locations where we could search for life beyond Earth. “If we found a planet with a vibrant biosphere, we would get curious about whether or not someone is there looking at us too,” Kaltenegger said. “If we’re looking for intelligent life in the universe, that could find us and might want to get in touch, we’ve just created the star map of where we should look first.”

Georgina Torbet
Georgina has been the space writer at Digital Trends space writer for six years, covering human space exploration, planetary…
Auroras and radiation from solar storms spotted on Mars
The specks in this scene were caused by charged particles from a solar storm hitting a camera aboard NASA’s Curiosity Mars rover. Curiosity uses its navigation cameras to try and capture images of dust devils and wind gusts, like the one seen here.

The specks in this scene were caused by charged particles from a solar storm hitting a camera aboard NASA’s Curiosity Mars rover. Curiosity uses its navigation cameras to try and capture images of dust devils and wind gusts, like the one seen here. NASA/JPL-Caltech

The recent solar storms caused epic events here on Earth, where auroras were visible across much of the globe last month. These storms, caused by heightened activity from the sun, don't only affect our planet though -- they also affect Mars. NASA missions like the Curiosity rover have been observing the effects of solar storms there, where the very thin atmosphere creates a potentially dangerous radiation environment. If we ever want to send people to visit the red planet, we're going to need to learn more about this radiation and how it's affected by events like solar storms.

Read more
Astronomers discover rare ‘exo-Venus’ just 40 light-years away
Gliese 12 b, which orbits a cool, red dwarf star located just 40 light-years away, promises to tell astronomers more about how planets close to their stars retain or lose their atmospheres. In this artist’s concept, Gliese 12 b is shown retaining a thin atmosphere.

Gliese 12 b, which orbits a cool, red dwarf star located just 40 light-years away, promises to tell astronomers more about how planets close to their stars retain or lose their atmospheres. In this artist’s concept, Gliese 12 b is shown retaining a thin atmosphere. NASA/JPL-Caltech/R. Hurt (Caltech-IPAC)

Astronomers have discovered a rare type of planet called an "exo-Venus," which is between the size of Earth and Venus and is located just 40 light-years away -- practically in our back yard. Although scientists think that planets of this size could be very common in our galaxy, they are hard to identify because they are so much smaller than the big gas giants that are more commonly discovered. This new planet also seems to have similar temperatures to Earth, and studying it could help to explain how atmospheres develop and how Earth became habitable.

Read more
Hubble spots a bright galaxy peering out from behind a dark nebula
The subject of this image taken with the NASA/ESA Hubble Space Telescope is the spiral galaxy IC 4633, located 100 million light-years away from us in the constellation Apus. IC 4633 is a galaxy rich in star-forming activity and also hosts an active galactic nucleus at its core. From our point of view, the galaxy is tilted mostly towards us, giving astronomers a fairly good view of its billions of stars.

A new image from the Hubble Space Telescope shows a galaxy partly hidden by a huge cloud of dust known as a dark nebula. The galaxy IC 4633 still shines brightly and beautifully in the main part of the image, but to the bottom right, you can see dark smudges of dust that are blocking the light from this part of the galaxy.

Taken using Hubble's Advanced Camera for Surveys (ACS) instrument, the image also incorporates data from the DECam instrument on the Víctor M. Blanco 4-meter Telescope, which is located in Chile. By bringing together data from the space-based Hubble and the ground-based DECam, astronomers can get a better look at this galaxy, located 100 million light-years away, and the dark dust partially obscuring it.

Read more