Earth-like Planet Fuels Excitement for Space Exploration

The question is the subject of movies, science fiction novels and our own curious minds. Are we alone in the universe? Prevailing scientific wisdom says yes but more and more the answer appears to be no.

With the advent of more sensitive cosmological equipment to scan the night sky, astronomers are able to see smaller objects with ever greater detail. The Kepler space telescope has been focused on a region of space containing over 100,000 stars. Scientists have been watching those stars for the tiniest hint of a wobble, indicating those stars could be hiding planets.

Now, the hunt for exoplanets — planets being discovered outside of our own solar system — is on and the results are startling.

Ten years ago, two University of Washington astrobiologists postulated that Earth is a rare planet indeed. In their book Rare Earth, Don Brownlee and Peter Ward suggested that for life to exist elsewhere in the universe very specific conditions must be met. They called this the habitable or Goldilocks zone, where a planet wasn’t too hot or too cold to support life. It had to have a certain amount of sunlight from its nearby star. So it had to be located in a solar system with other planets a certain distance from its star.

Building on that set of criteria, professional astronomers, undergraduates, citizens and curious skywatchers are all becoming planet hunters. Now the science is improving to the point where a new discovery yields the planets size, mass and even its average surface temperature.

Finding a Planet in a Star Stack

Kepler 22 Star System, Showing Kepler 22b in the Habitable Zone

British author and astronomy expert Ian Ridpath explains the way astronomers find new exoplanets.

“NASA has this space telescope called Kepler which has been staring for the past couple of years at this one particular area of sky containing over 100,000 stars. And it’s been looking for very slight dips in the star’s brightness as something goes across in front of the stars.

“It’s called the transit method. Now if it does that three times in succession then the NASA scientists think that is good enough to conclude that what is causing the dip in light is a planet.”

That’s why astronomers are so excited about the confirmation of a new exoplanet, Kepler 22b. By all calculations it is located in a habitable zone around its star, known as Kepler 22. The star, which is smaller and cooler than our sun is located between the constellations Cygnus and Lyra. Kepler 22b orbits around the star and may be the right distance from the star to support life. But the size of the planet — about 2.4 times that of Earth, really excites scientists. It is rare for a discovery to find a planet in the same size range as our own blue planet. Of the 28 planets found so far his is the smallest planet ever confirmed by Kepler.

Douglas Hudgins, Kepler program scientist at NASA says, “This is a major milestone on the road to finding Earth’s twin.”

It’s much easier to spot a big planet, like a gas giant the size of Jupiter. But those are not likely candidates for the search for life, microbial or intelligent. Kepler 22b is about the right size and appears to have a liquid water surface. In fact, it looks like the entire planet is covered in water.

That coupled with measurements pointing to the temperature being about 72 degrees gives astronomers hope that life may exist there.

The one problem is that the newly discovered planet is far, far away. 600 light years to be exact. It would take over 600 million years to travel there under current rocket power. So for now, our powerful telescopes and improving resolution will have to be enough to fuel the search for new planets where life could exist.

William Borucki, Kepler principal investigator at NASA Ames Research Center says the Kepler team got very lucky in detecting this planet. He says, “The first transit was captured just three days after we declared the spacecraft operationally ready. We witnessed the defining third transit over the 2010 holiday season.”