Discovering new planets in distant galaxies

Astronomers are searching for a second Earth — and many more!

A hundred years ago our Milky Way Galaxy was the only one known. Then in the 1920s Edwin Hubble, using the largest telescope of the time, discovered the second known galaxy, Andromeda. It was a tremendous finding.

Since then astronomers have been discovering billions of additional galaxies out in space. These discoveries have triggered astronomers to wonder about the existence of planets like our Earth, with life on them, and if so, how many there might be.

During the past 10 years more than 300 planets have been discovered encircling stars in our own Milky Way galaxy. However, they are so far away that they cannot be seen. So how do we know that they exist? As a planet circles its star, or sun, when it comes to the position where it is in front of the star from our standpoint it reduces the brightness or intensity of the star that it encircles. And astronomers discovered that this is a repetitive dimming and brightening, as the planet rotates. Current telescopes are not big enough to see the planets themselves.

In 1998 a team led by Geoff Marcy of the University of California was focusing on a star called Gliese 876, about one-third the mass of our sun and only 15 light years away. He discovered that the star became darker at times and then brighter again. He concluded that the reason was the rotation of a giant planet, twice the size of Jupiter, around the star, and when it covered the star in our direction it blocked out part of the star’s light.

Several years afterward a second planet was discovered, about half the size, and three years later a much smaller planet was discovered, one that appears to be about five or six times the size of our Earth. This was the beginning of the discoveries of the 300-plus planets to this date, all similar in size to Jupiter.

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But telescopes are getting bigger and bigger now and within the next five to 10 years there will be larger, new telescopes in space that might be able to begin to actually see these planets. It might take many years for this to happen, but the astronomers are determined to accomplish that. And as the scopes become larger and more details become visible, they hope to be able to actually see life itself on these planets. Right now the search is for water and oxygen on the planets because those are the two vital ingredients that support life.

The ability of astronomers and scientists to enlarge their scopes and enlarge their views of planets is really spectacular. The telescopes that aim at such views must operate in outer space, probably 1 million miles away from our Earth and solar system. It might take 25 or 50 years for that to happen, but knowing the desire and determination of the astronomers and scientists, I feel certain that the time will come when that life will become visible. Our children and grandchildren will have the pleasure of seeing this.

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Corot, a 1,300-pound spacecraft, was launched in December 2006. Corot relies on a technology that has recently come into existence in ground-based searches for planets rotating around stars. It detects the slight but regular dimming in a star’s light when a planet slides in front of it. Corot stares at the same spot to look at these changes in light over a long period of time, 150 days or more, to evaluate the time of rotation and the size of the planet.

Corot has a 10.6-inch telescope that monitors up to 12,000 sun-like stars at once. Not long after its launch, the Corot science team published a description of its mission. It predicted that the first confirmed terrestrial planets were expected to be seen in the spring of 2008. However, the discovery so far has been two new hot Jupiters and one unconfirmed super-earth planet. It is not easy to see these things but the efforts of astronomers will continue.

The Keplar spacecraft was launched in early March 2009. Keplar is the man who created the first telescope back in the early 1600s and who was the discoverer of the laws of planetary motion. Astronomers are expecting the Keplar mission to verify how common earths actually are, and will be a real push to search for life in the universe. The Keplar spacecraft has a telescope measuring 37.4 inches, which is 3.5 times the size of the telescope in Corot.

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As you can see, I firmly believe that little by little, as space telescopes improve, one day we will really be able to view life on the distant planets in our Milky Way.

While Keplar and Corot are focusing on sun-like stars, ground-based telescopes are now concentrating on viewing red dwarf stars because planets there are easier to find. An Earth-like planet would cause a bigger wobble and a darker transit than a sun, and the effect would be more pronounced if the planet were in the habitable zone.

Still more and larger telescopes are scheduled for launching during the next 10 to 20 years. Just when we will be able to see actual pictures of life on other Earth-like planets is something we scientists are all waiting for. And it will surely happen!

Sidney X. Shore is a scientist, inventor and educator who lives in Sharon and holds more than 30 U.S. patents.