Perhaps most exciting of all, much of the leg work of identifying candidate planets has been done not in high tech labs or around university tables, but by citizen scientists with little or no training. Sites like planethunters.org have made it possible for anyone to comb through the data collected by NASA’s Kepler space telescope looking for indications that a given star hosts at least one planet. That means that on any given night, you (yes you) can sit down at your computer and look for hidden worlds that are both long ago and far away.
THE GRAPHS AND THE GLORY
Though we were once literally in the dark about how to look for exoplanets, there are now a variety of ways to successfully identify our distant planetary neighbors.
Kepler and a host of other telescopes use what’s known as the transit method. Though planets are much, much smaller than stars, when they pass in front of a star, that star’s brightness appears to dim ever so slightly. That brief dimming produces telltale dips in graphed data that can be picked out by amatuer planet sleuths.
The wobble method—whereby planets are detected by measuring the very small wobbles that their gravitational pull causes in a host star—has also produced some stunning results.
This tiny glowing dot is the first exoplanet ever directly imaged by Hubble. It’s trillions of miles from Earth. ⓒ NASA,ESA, P. Kalas, J. Graham, E. Chiang, E. Kite (University of California, Berkeley), M. Clampin (NASAGoddard Space Flight Center), M. Fitzgerald (Lawrence Livermore National Laboratory), and K. Stapelfeldt and J. Krist (NASAJet Propulsion Laboratory).
Lest you think that the hunt for exoplanets is all graphs and very little glory, know that we can now capture their images as well. The world’s most famous space telescope, the Hubble, produced the first image of an exoplanet in 2008. That historic image was made possible by Hubble’s powerful optics, designed in part by National Science Medalist Dr. Sandra Faber. Other images are forthcoming from the Subaru Telescope at the Mauna Kea observatory in Hawaii, which another National Science Medalist, Dr. James Gunn, played a role in designing.
Though perhaps most famous for its images, Hubble has also unlocked some of the mysteries of these alien atmospheres—probably our best hope for detecting possible signs of life. Using a spectrometer to split light into its constituent colors and reveal the “fingerprints” of chemical molecules, Hubble has identified water vapor, methane, and other particles in exoplanet atmospheres. It’s also provided temperature maps of planets orbiting distant stars. Spitzer, another space telescope, has been able to further fill in the picture by providing scientists with a way to study weather patterns. Subaru too will provide information about exoplanet atmospheres.
A WHOLE NEW WORLD
Thanks to these incredible leaps of science, our skies are now populated with a weird and wonderful host of planets unlike anything we have ever known—or known was possible.
A random sampling of planets sounds like imaginative science fiction. One third of the surface of 55 cancri e is likely to be covered in diamonds, created by intense pressures and heat acting on its carbon-rich surface.
Then there’s TrES-2b, known as “the Dark Planet” because its surface reflects only 1% of the light that falls on it, making it darker than coal or black acrylic paint. Scientists don’t know why the planet is so dark, and the explanation may very well be something as yet unknown to science.
We’ve even found a whole group of Tatooine-like planets, including one called Kepler 16-b. This planet, like Luke Skywalker’s home, orbits two different stars. That means it would have two sunrises and two sunsets every day. Sadly, you wouldn’t be able to see those sunrises because, well there’s nowhere to stand. Kepler 16-b is about the size and density of Saturn—making it a gas giant, rather than the rocky planet young Skywalker inhabited.