Strange New Worlds: Science Fiction Becomes Reality in Our Time

By Inge Heyer, Joint Astronomy Centre

For most of our lives, the only planets we have known are the ones circling our Sun. Our home planet, Earth, and the other small and large planets in our Solar System, plus assorted moons, asteroids and comets are our celestial family. As we see the sun by day and watch the planets wander among the stars by night, we people of Earth have wondered throughout the ages about what untold mysteries the heavens might harbor.

Bit by bit some of these mysteries have been uncovered. We have found birth places of stars, we have seen the various stages of the life cycle of the stars, and we have realized that our Sun is part of a large collection of stars making up a galaxy. The Milky Way, in turn, is one galaxy among untold millions in the vastness of the Universe.

But one important question has been eluding us: are there other families of planets like ours? As we look out from Earth at night, we see the stars as tiny dots all over the sky. Our Sun is such a star just like all the others. So if our Sun has a family of planets, why shouldn’t the other suns have planets as well? Until very recently, planets around other stars could only be found in science fiction books or movies. We all remember the Starship Enterprise on TV orbiting oddly colored planets in star systems far away, and we can still see our heroes admiring vistas of beautiful nightscapes, lit by two or three moons. What was mere fiction as little as two decades ago, has now become much more real.

Many people have thought for some time that it would make sense to investigate planets around other stars, but sadly, the technology was not available to find out. The stars are so much brighter compared to their planets, it is like trying to find a candle next to a football stadium flood light. But technology has developed to a point where we can now overcome these obstacles.

In 1990, the first planet detected since Tombaugh's discovery of Pluto in 1930 was found around a pulsar, a dead star, by timing the spin of the pulsar very precisely. In 1995, a planet was found around the star 51 Pegasi by carefully measuring the star's motion, thereby detecting the small gravitational influence of a planet. After 51 Pegasi, the discovery flood gates opened. As of 13 January 2009, 335 planets around other stars have been found.

Some of these stars have more than one planet, like our Sun. Many of the planets are much larger than our largest planet, Jupiter. And many of these super-Jupiters are in orbits around their star that are much closer than Mercury is to our Sun, earning them the name “hot Jupiters.” Then there are smaller worlds, also very close to their star, called “lucifer planets.” Astronomers have found planets as large as 25 times the size of Jupiter, and as small as about ten times the size of Earth. But none of these systems look anything like our Solar System. How can this be? We do not know, yet, but it appears that there is much diversity among the planets and their systems. As we find more and more planets, we hope that we will begin to understand how their systems formed and evolved, and how our Solar System fits into this picture.

In order to get a complete planetary census, we need to find not only the big planets, but also the smaller ones. However, the smaller ones are more difficult to find, and therefore we have to work much harder at making our technology more sensitive to the tiny bit of light these little ones give off. We are making progress, but much work is to be done by future generations of astronomers, instrument engineers, and also chemists and biologists.

For the ultimate question to ponder is obvious… are there planets like Earth out there, and could they, maybe, sustain life? One problem we humans on the planet Earth have is one of limited examples. The only life-sustaining planet we know is ours. To figure out what other such planets might be like, we have to use our imagination, as well as knowledge of chemistry and biology. How would such a planet appear in the different wavelengths of light we observe with our telescopes? What types of stars would these planets orbit, and how close to their star would they be? And, as Lynette Cook’s painting of 70 Virginis B shows, the life-sustaining world does not necessarily have to be a planet, it could be a moon. The possibilities are as limited, or as endless, as our imagination.

We do not know the answer to many of these questions yet, but the successes in finding any planets at all give hope that one day we will know: Are we or aren’t we alone?

The Extrasolar Planets Encyclopedia http://exoplanet.eu/ Lynette Cook’s Planets Paintings http://extrasolar.spaceart.org/extrasol.html Joint Astronomy Centre Outreach http://outreach.jach.hawaii.edu/