The three known solar systems with planets inside the habitable zone of their stars. (
Centauri Dreams)
The rate of planetary discovery outside our solar system continues to accelerate beyond all expectations.
Today, along with the announcement of 50 other exoplanet discoveries, comes news from the European Southern Observatory (ESO) of the second planet ever detected in the habitable zone of another solar system:
Astronomers using ESO’s world-leading exoplanet hunter HARPS have today announced a rich haul of more than 50 new exoplanets, including 16 super-Earths, one of which orbits at the edge of the habitable zone of its star.
This is the largest number of exoplanets announced in a single discovery, and includes the remarkable finding that 40 percent of stars like the sun have planets smaller than Saturn.
More on the planet in the habitable zone:
“If we are really, really lucky, this planet could be a habitat” like Earth, said Lisa Kaltenegger of the Max Planck Institute for Astronomy in Heidelberg, Germany.
The planet, dubbed HD85512b, circles an orange star somewhat smaller and cooler than our sun about 36 light-years away. The star, HD85512, is visible in the southern sky in the constellation Vela.
The newly found planet circles this star every 59 days, putting it at the edge of the “habitable zone” where water could exist if atmospheric conditions were right.
In a teleconference, Kaltenegger said that the planet is at the warm edge of its star’s habitable zone, as if “standing next to a bonfire.” That means the planet would require a lot of cloud cover — which reflects starlight — to keep the surface cool enough to prevent any water from boiling, she said.
So, while it is possible that HD85512b has an Earth-like atmosphere, it is unfortunately unlikely. However, as the smallest exoplanet ever detected in the habitable zone of another star, it is still big news. Further, given both the ongoing Kepler mission and the forthcoming upgrade in the ESO's exoplanet hunting abilities, it may not be long before we (that is, humans) make multiple confirmed discoveries of Earth-like planets in the habitable zones of other stars.
Centauri Dreams explains why we should be excited:
And in addition to HARPS, which has found about ⅔ of all exoplanets with masses less than Neptune’s, we should put ESPRESSO on our radar. Echelle SPectrograph for Rocky Exoplanet and Stable Spectroscopic Observations is in its early design stage, but scheduled to begin operations on the ESO Very Large Telescope in 2016. Now we’re really getting down to cases: ESPRESSO will have a radial velocity precision of 0.35 km/h or less. Compare that to the 0.32 km/h that Earth induces on the Sun and you can see why astronomers look forward to using ESPRESSO to discover Earth analogues around nearby stars.
This means ESO will soon be able to find exoplanets the size of Earth around stars which can support life. This is something which is not currently possible. Outside of a pulsar planetary system, all exoplanets discovered to date have been at least 1.7 times as massive as Earth, and as such are not true analogues for our home.
The future of exoplanet detection is so bright, you gotta wear shades.