Astronomers have discovered the farthest planets from Earth yet found, including one with a year as short as 10 hours — the fastest known.
Using the Hubble space telescope to peer deeply into the centre of the galaxy, the scientists found as many as 16 planetary candidates, they said at a news conference in Washington, D.C., on Wednesday.
The findings were published in the journal Nature.
Looking into a part of the Milky Way known as the galactic bulge, 26,000 light years from Earth, Kailash Sahu and his team of astronomers confirmed they had found two planets, with at least seven more candidates that they said should be planets.
The bodies are about 10 times farther away from Earth than any planet previously detected.
A light year is the distance light travels in one year, or about 9.46 trillion kilometres.
If all 16 candidates are confirmed, it would be the largest number of planetary announcements made at once. The previous record was 12 planets.
Year less than a day
Sahu, an associate astronomer at the Space Telescope Science Institute in Baltimore, Md., said five of the planetary candidates have years that are less than a day long — the shortest ever recorded.
"They orbit their stars in less than one day, the likes of which we have never seen before," Sahu said.
"One of our candidates orbits its parent star in 10 hours," added researcher Mario Livio, an astrophysicist at Johns Hopkins University in Baltimore.
The shortest planetary orbit previously on record is 1.2 days, Sahu said.
Answers key questions
The research findings answer long-standing questions about the nature of the galaxy and the existence of planets around the stars, Livio said.
Until now, scientists wondered whether planets existed throughout the Milky Way or were a unique feature of the region of the galaxy humans inhabit. The planetary candidates found using the Hubble telescope change that.
"This allows us to say with confidence there are billions of stars in our galaxy with planets," Livio said.
Astronomers also did not previously know whether planets are commonly found around stars rich in heavy elements such as iron, which are far more common in the galaxy than the sun, which is made mostly of hydrogen, a little helium and traces of other, heavier elements, he said.
The researchers found that planets were as common around the more abundant heavier stars as they are for stars made of lighter elements.
Standing on the surface of one of the planets would be a dramatic experience, Sahu said.
The bodies are so close to the stars they orbit that their surface temperature is about 1,650 C, he noted.
"One side would always be facing the star and one side would always be facing away," making for a perpetual day and a spectacular view.
The star would fill the sky from the horizon to about 30 degrees above it, he said.
With so many planets in the galaxy, the odds of finding one that is capable of supporting life rise dramatically, the researchers said.
"All of us are dreamers and we would like to find life elsewhere, and perhaps intelligent life," Livio said.