4.5 Billion Earthlike Planets in our Galaxy 02.14.13 Search

Six are within 13 light-years of Earth

George Filer

Billions of Earth-like alien planets likely reside in our Milky Way galaxy, and the nearest such world may be just a stone's throw away in the cosmic scheme of things, a new study reports. Astronomers have calculated that 6% of the galaxy's 75 billion or so red dwarfs — stars smaller and dimmer than the Earth's own sun — probably host habitable, roughly Earth-size planets. That works out to at least 4.5 billion such "alien Earths," the closest of which might be found a mere dozen light-years away, researchers said.

Milky Way Our home galaxy

"We thought we would have to search vast distances to find an Earth-like planet," study lead author Courtney Dressing, of the Harvard-Smithsonian Center for Astrophysics (CfA), said in a statement. "Now we realize another Earth is probably in our own backyard, waiting to be spotted."

[Editor's Note: ...or perhaps, they have already noticed us.... hmm... What a concept!]

Dressing and her team analyzed data gathered by NASA's prolific Kepler space telescope, which is staring continuously at more than 150,000 target stars. Kepler spots alien planets by flagging the tiny brightness dips caused when the planets transit, or cross the face of, their stars from the instrument's perspective.

Kepler has detected 2,740 exoplanet candidates since its March 2009 launch.

Follow-up observations have confirmed only 105 of these possibilities to date. In the new study, Dressing and her colleagues re-analyzed the red dwarfs in Kepler's field of view and found that nearly all are smaller and cooler than previously thought. This new information bears strongly on the search for Earth-like alien planets, since roughly 75% of the galaxy's 100 billion or so stars are red dwarfs.

Further, scientists determine the sizes of transiting exoplanets by comparison to their parent stars, based on how much of the stars' disks the planets blot out when transitting. So a reduction in a star's calculated size brings a planet's size down, to the realm of rocky worlds with a solid, potentially life-supporting surface.

And the size and location of a star's "habitable zone," the range of distances that could support the existence of liquid water on a planet's surface, are strongly tied to stellar brightness and temperature.

The team calculated that about 60% of red dwarfs likely host worlds smaller than Neptune. Dressing and her colleagues determined that Kepler has spotted three roughly Earth-size exoplanet candidates in the habitable zones of their parent red dwarfs. One of these worlds is Kepler Object of Interest (KOI) 1422.02. This candidate's newly calculated size is 90% that of Earth, and it circles its star every 20 days. This planet may be the first "alien Earth" ever discovered. There are other candidates that could have life like Earth.

Gliese 581g Slide Show on 9 Exoplanets That Could Host Alien Life

4.5 Billion Earth-like planets
The team further determined that about 6% of the Milky Way's red dwarfs should harbor roughly Earth-size planets in their habitable zones, meaning that at least 4.5 billion such worlds may be scattered throughout our galaxy.

"We now know the rate of occurrence of habitable planets around the most common stars in our galaxy," co-author David Charbonneau, also of CfA, said in a statement. "That rate implies that it will be significantly easier to search for life beyond the solar system than we previously thought."

That search may bear fruit right in Earth's backyard, researchers said.

 

"According to our analysis, the closest Earth-like planet is likely within 13 light-years, which is right next door in terms of astronomical distances," Dressing told SPACE.

"The knowledge that another Earth-like planet might be so close is incredibly exciting and bodes well for the next generation of missions designed to detect nearby Earth-like planets," she added. "Once we find nearby Earthlike planets, astronomers are eager to study them in detail with the James Webb Space Telescope and proposed extremely large ground-based telescopes like the Giant Magellan Telescope."

Red dwarfs are also longer-lived than stars like the sun, suggesting that some planets in red dwarf habitable zones may harbor life that's been around a lot longer than that on Earth, which first took root about 3.8 billion years ago.

Scientists have also detected five planetary candidates circling the star Tau Ceti, which lies 11.9 light-years away. The new study will be published in The Astrophysical Journal. Thanks to space com.

Source

News - Milestones - New History - Thoughts - Humor - Expectations - Wisdom - Knowledge

1306 Gypsy
A Higher-Level Solution to CCDNMBH-banner
before and after
5th WorldReturn to 5W
Archives Archives
Granite-Planet.net
logo Free Sign Up