Have you ever wondered if there are other planets in the
universe (besides the nine in our solar system)? Everyday astronomers search for
planets that orbit other stars. These planets are called extrasolar because they
do not orbit our Sun.
How do astronomers find extrasolar planets?
Astronomers can’t just look up, point their finger, and say
"Oh look! There’s another new planet!"
Astronomers use different techniques to locate extrasolar
planets. It is hard to find extrasolar planets because the stars they orbit are
light years away and are VERY bright! With even the most powerful telescopes you
can’t see these planets orbiting near their glowing stars. Sometimes
astronomers detect the dimming of a star’s light as its planet passes in front
of it.
One of the techniques used is to watch stars to see if they
slightly wobble. This works because a star wobbles from the slight gravity of an
orbiting planet. Even though stars are much bigger than planets, the planets
have just enough gravity to tug a little bit on the star that they orbit. This
causes the star to wobble. Some stars have wobbles inside of wobbles, which
means that there is probably more than one planet orbiting the star.
Another way astronomers find extrasolar planets is to use radio
telescopes to detect the radio waves that are created while a solar system
is forming. The radio waves are from the hot dust and gas in the forming solar
system. The radio telescopes that are on Earth can detect those radio waves.
How big are the extrasolar planets?
All of the extrasolar planets found so far are several times
larger than Jupiter, which is the largest planet in
our solar system. This is a bit amazing because that type of planet is usually
made of gasses and usually takes a long time to form.
What is the history of the search for extrasolar planets?
In the 1900s astronomers found out that our solar system is not
the center of the galaxy, and that our galaxy is not the center of the universe.
Earth is just one tiny planet orbiting one star out of billions. This made it
seem possible that there were other planets that are just like Earth.
The first extrasolar planet was found in 1995. Its name is
51PegasiB, and it orbits a star that is 45 light years from Earth.
The American astronomers Geoffrey Marcy and Paul Butler
discovered 13 more stars with planets orbiting them between 1996 and 1998.
Geoffrey Marcy and his team of astronomers found 18 other
extrasolar planets since 1995 and also found a planet on November 7, 1999. This
planet is much bigger than Jupiter, and it orbits the star HD209458 in the
constellation Pegasus.
On November 29, 1999 six more extrasolar planets were found.
This brought the number of extrasolar planets that were discovered by
astronomers to 28.
Upsilon Andromedae and its 3 planets
In June look up in the sky and you might see Upsilon Andromedae.
Now imagine that far away, a little yellow dot has 3 planets orbiting it. Two of
its planets are at least twice the size of Jupiter, and the third is at least
four times as large as Jupiter. They are all gas planets with very elliptical
orbits. This was the first multi-planet solar system discovered besides our own.
Could life exist near Upsilon Andromedae?
The orbit of one of Upsilon Andromedae’s planets is very close
to the area where life could develop. Upsilon Andromedae is a bit brighter and
bigger than our Sun but is otherwise similar to it.
All of Upsilon Andromedae’s planets are made of gas, so life
would have to be on their moons (if they had any). It would be on its outer two
planets. It couldn’t be on the planet closest to Upsilon Andromedae because it
is only 5.5 million miles away from it, that means anything on it would fry
(Earth is 93 million miles from the Sun).
What about water?
Upsilon Andromedae’s outer most planet is on the edge of the
area where life could develop. If it had large enough moons that had good enough
atmospheres, then they could support life. If they had good enough atmospheres,
then they could hold liquid water. That means it could have carbon-based life
forms like us.
Life in our solar system
Water on Mars?
Water could also exist on Mars.
Scientists have found more evidence of water on the fourth planet in our solar
system, Mars. The Mars Global Surveyor took pictures of newly formed channels in
Mars’s surface. Scientists believe some sort of liquid formed these channels.
One of Jupiter’s moons, Europa, may have liquid water under
its surface. If this is true, it could support life (such as microscopic
organisms). The information that is collected by the Europa probe, along with
information from the Galileo spacecraft, might give us more clues to life on
Europa.
Europa Probe
Scientists plan to send a spacecraft called the Europa Probe to Europa. It will use radio waves to measure the thickness of the ice on Europa’s
surface, which scientists now think is ¾ of a mile thick. The tool that sends
the radio waves through the ice is called a radar sounder. This radar sounder
will be able to detect if there is any liquid water under the surface of ice.
