New Worlds
For years, scientists made little progress in their search for life on other worlds. One problem was that they hadn’t found many worlds. They knew of only Mars, Venus, and the other planets in our solar system.
But in 1991, two astronomers discovered the first planets ever found outside our solar system. Those planets are not likely to have life, but they proved that other stars—maybe many stars—can have planets.
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This
painting is an imaginative view of Pulsar 1257+12
from one
of its planets. The real pulsar is dark. We have shown it as if the pulsar and its radiation beams give off visible light. We have also made the other two planets closer, so they can be seen. |
At first, the scientists weren’t looking for new worlds. They were just trying to figure out why a small object trillions of miles away was sending badly timed pulses of radio waves.
That object is called a pulsar. Like all pulsars, it’s left over from a star that ran out of fuel and blasted most of its material into space in a huge explosion called a supernova. No one expected to find planets around a pulsar because a supernova would have blown any planets into space. In fact, scientists are still trying to understand where this pulsar’s planets came from.
The pulsar gives off no visible light, and it’s only about ten miles across, which is tiny compared to a star. It also spins thousands of times faster than a normal star, sending pulses of radio waves 161 times a second. The pulsar is so far from Earth that these flashes take 1,300 years to get here.
Pulsars are known for their precise timing, which is more regular than our best clocks. But this pulsar is different. It acts like a clock with mice in its works. Sometimes its pulses are early, and sometimes they’re late.
The simplest explanation is that the pulsar is wobbling. When it moves toward Earth, its pulses get here early. When it moves away, the pulses come late.
But what could make a pulsar wobble? The lead scientist, Dr. Alexander Wolszczan of Penn State University, thought the pulsar was being pulled back and forth by the gravity of planets in orbit around it.
His idea was hard to prove. Except for our Sun, all stars and pulsars are so far away that we would not be able to see any planets, even with the best telescopes.
But Dr. Wolszczan used exact predictions to show that the planets are there. He worked with the idea of a pulsar that has two planets, each of them about four times the size of Earth. He predicted the pulsar’s flashes for more than a year.
And the pulsar followed his schedule. It even gave evidence for a third planet about the size of Earth’s Moon.
Life
Out There?
Life
like ours could not survive in the deadly radiation of a
pulsar. But the pulsar’s planets show that planets
might form in many different situations, even after a supernova.
Scientists had new hope in their long search for more planets
and extraterrestrial life.
The belief that the universe holds billions of planets is centuries old. After all, if the stars and our Sun all formed in the same way, then many of those stars should also have planets. But the nagging question has been: Is our solar system typical, or is our Sun the only star with planets?
To answer that question, scientists have been searching for planets around Sun-like stars. Since the planets would be too far away to see, scientists have looked for any effects that planets might have on their “parent” stars.
Like the pulsar, a normal star should wobble as its planets whirl around it. So astronomers might see a star move slightly from side to side. Many times astronomers thought they had found new solar systems by watching for these movements. But later they learned that the stars only seemed to move because of small mistakes in the measurements or quirks in the equipment.
More
Jupiters
But
astronomers succeeded by looking for tiny changes in the
color of a star’s light. Such changes can also be caused
by the wobbling motion of a star.
This way scientists can find planets that are at least as big as Jupiter, our biggest planet.
In fact, after the pulsar’s planets were discovered, several of these giant-sized planets were found in orbit around normal stars.
To find smaller planets, like Earth, scientists and the National Aeronautics and Space Administration (NASA) are devising new ways to study distant stars. One idea is NASA’s Planet Finder, which would be made up of four telescopes working together in an orbit close to Jupiter’s.
This huge instrument would be able to erase starlight from the images it makes. And that would leave pictures of any planets that might be in orbit around distant stars. The Planet Finder would also be used to detect water vapor, carbon dioxide, and other gases that go along with all known forms of life.
Scientists have finally answered the question whether there are planets around other stars. In a few years, we may be asking an even more exciting question: Which of these planets might have life?
