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How can you tell what’s in the atmosphere of a planet that’s over one billion miles from Earth?

January 19th, 2011 by Sarah Pryputniewicz
Use a VERY long sampling straw?  Nope.
Use a spectrometer? Yup.  (Explore how this works in our “Is there life outside of Earth?” investigation.)
Scientists at NASA, the European Space Agency, and the Italian Space Agency collaborated to send the Cassini spacecraft to Saturn to get closer looks at the planet, its rings, and its many moons.  In November 2010, the exciting news came back that oxygen was discovered in the atmosphere of Rhea, one of the moons.
It took five years of measurements and data analysis to collect enough data to fully support the discovery.
So if there’s oxygen, there’s life, right?  Nope.  There are lots of organisms on Earth that don’t need oxygen.  And Rhea is too far from the Sun to be in a “habitable zone” anyways.
This discovery, relatively close to home, shows that we can detect molecules in the atmosphere of an orbiting body nearly one billion miles away.
And if we can make the measurement from that far away, it’s only a matter of time until we’ll be able to measure atmospheres of planets and moons outside of our solar system!
http://saturn.jpl.nasa.gov/news/cassinifeatures/feature20101126/
http://www.sciencedaily.com/releases/2010/11/101128222041.htm
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Finding a needle in a haystack–how to deal with noise in the data?

January 9th, 2011 by Sarah Pryputniewicz

Scientists have used indirect measurements of movement to infer the presence of waves for a very long time.  For example, how can you tell when it’s windy without going outside?  You look to see the movements of the trees or flags or other flexible structures.

Now, scientists at NASA’s Jet Propulsion Laboratory are using lasers to measure gravitational waves.  Gravitational waves were predicted by Albert Einstein, but only in the last few years has the equipment gotten sensitive enough to attempt measurements.  The scientists face the task of detecting a wave that’s 0.000000000005 meters tall from spacecraft 5,000,000,000 meters away!
Using known masses attached to spacecrafts and lasers that measure the positions of the masses, the scientists hope to detect the movements caused by gravitational waves.  Lasers, although very precise, are still too noisy to measure the gravitational waves.  (Learn more about noise and using indirect measurements in our “Is there life outside of Earth?” investigation.)
What’s the solution to the noise problem, finding that tiny little wave across trillions of miles?  Generate artificial noise in the lab and see if you can still detect the signal.  It’s worked in the laboratory, so scientists may soon be able to detect gravitational waves in space.
The ability to detect smaller and smaller motions will enhance the ability of instruments to detect smaller and smaller planets around other stars–perhaps even another “Earth.”  Technological innovation is the only limit.
http://www.sciencedaily.com/releases/2010/11/101128220203.htm
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How much does a star weigh?

January 4th, 2011 by Sarah Pryputniewicz
Scientists may soon find out.
Orbiting objects exert a gravitational pull on each other.   This gravitational pull is what gives objects their weights; it’s the reason that you weigh 83% less on Earth’s moon than on Earth, without losing any of your mass.
Scientists are currently using measurements of objects’ gravitational pulls to find new planets around stars.  As a planet orbits around a star, it pulls on the star, making the star appear to wobble.  Looking for the wobble (as you can do in our space investigation”Is there life outside of Earth?“) is how scientists find objects around stars.
David Kipping, an astrophysicist at the Harvard-Smithsonian Center for Astrophysics, realized that by using the same strategy with a planet and its orbiting moon, along with some calculation using Kepler’s Laws of Motion, scientists will be able to determine the mass of distant stars.
In essence, they’re just measuring the wobble effect that all three objects (star, planet, and moon) exert on each other.  All they need to do now is find stars that have planets that have at least one moon.
“When they’re found, we’ll be ready to weigh them,” said Kipping.
http://www.sciencedaily.com/releases/2010/10/101015140801.htm
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Goldilocks and the Habitable Planets?

December 9th, 2010 by Sarah Pryputniewicz
In the fairy tale, Goldilocks was a little girl who walked into a house in the forest.  She ate porridge, sat in chairs, and slept in beds.  The first choices she tried were too hot, too big, and too hard.  Her second choices were too cold, too big, and too soft.  Her third choices were all “just right.”
The story of Goldilocks is a good metaphor for finding planets that can harbor life.  Some are too close to their stars (too hot), some are too far from their stars (too cold), and some are just the right distance from their stars (not too hot or too cold).
In September 2010, planet-hunting scientists from the University of California Santa Cruz and the Carnegie Institution of Washington found such a “Goldilocks” planet.  Does this planet, dubbed Gliese 581g, have life?  Maybe, maybe not.  Even if it did have life, it’s unlikely to look like the fictional movie and television versions of aliens.
Much like the movies and televisions, artists’ representations of planets (like Lynette Cook’s version of Gliese581g, courtesy of NASA, at left) are also fantasy.  Gliese 581g is close to 19 billion kilometers from Earth–far too far away for any visual sightings with a telescope!
Still, the ability to find planets that are in habitable Goldilocks zone orbits is amazing in itself!  While scientists have been able to find planets for a while, most of the planets discovered have been very large.  After all, those are the easiest ones to detect with the current technology.  As telescope technology advances, scientists should be able to detect smaller and smaller planets, some of which might be more like Earth.
Even if scientists never find planets with living organisms, the advances in technology and the information we learn about other solar systems will only help us to better understand our own planet and the wide variety of organisms with which we share it.
Read about the discovery at: http://www.nasa.gov/topics/universe/features/gliese_581_feature.html
Learn how scientists find new planets and practice finding your own in our newest High-Adventure Science curriculum module: “Is there life outside of Earth?“
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