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Exoplanets: Top 10 Questions

January 2017

Thanks to Thanks to Dr. Nick Siegler, astrophysicist and chief technologist for NASA's Exoplanet Exploration Program, NASA's Jet Propulsion Laboratory; and Dr. Tiffany Meshkat, postdoctoral scholar in the Exopl for the answers.

1: What is an exoplanet?

An exoplanet is a planet that orbits another star. In our solar system, we have eight planets, and they all orbit around the sun. As you can imagine, you will find exactly the same thing across the galaxy where all the other stars and all the other suns have their own planetary systems. So, those planets outside of our solar system, orbiting other stars, are called exoplanets. (From Emmett at Dalton Elementary School in Dalton Gardens)

2: Is there life on other planets?

We have been looking for life on other planets, and so far we haven't found any signatures. Signs of oxygen in the atmosphere of a planet, or any other signs of life like faint radio signals that could be used for communication, continue to be investigated. Scientists are looking for devices to probe the atmospheres of these exoplanets. These devices would detect gases that are very similar to gases on our own planet, like carbon dioxide, oxygen, and water vapor. We do think that life could exist on these exoplanets. (From Alec at Cynthia Mann Elementary School in Boise)

3: How many exoplanets are there?

To date, we have discovered over 3,000 planets. We believe that the galaxy is absolutely teeming with planets. We have eight planets in our own solar system. There are hundreds of billions of stars, and we believe that each one of these stars probably has a planetary system of its own. So, there could be hundreds of billions of exoplanets. We have an exoplanet website with a counter that can tell you how many we have discovered on a daily basis. Check it out! (From Maddie at Koelsch Elementary School in Boise)

4: How big does the star have to be for a planet to orbit around it?

Planets can orbit around many different ranges of stars. You may think that our star, the sun, is very large. In fact, however, it is pretty average compared to all of the stars in the galaxy. We have found that the planets orbit the very smallest stars and up to the very largest stars. It seems like there are planets around just about every star. (From Wyatt at Trail Wind Elementary School in Boise)

5: What is the closest exoplanet to Earth?

The closest exoplanet to Earth was just discovered last summer. It happens to be around our closest star, Proxima Centauri. It's about four light years away. Don't pack your bags anytime soon. With our current technology, it would take maybe 80,000 years to get there! That's how distant the stars are from one another. Perhaps one day we will develop technology to actually fly there and take a look for ourselves. (From Brooklyn at Russell Elementary School in Moscow)

6: What substances are exoplanets made of?

Exoplanets are made of many different substances. The planets in our own solar system are made of things like rock and lots of gas. Exoplanets are made of these same substances, but in differing amounts. Some planets have so much carbon that we consider them like a diamond planet. There is a big range of exoplanets. They range in size, distance from their star, and in amounts of gas in their atmosphere. Every time we find a new planet, there is something surprising about it. (From Brandon at Sagle Elementary School in Sagle)

7: How many telescopes for looking at exoplanets are there?

There are many telescopes looking for exoplanets. The five biggest telescopes on Earth are looking for exoplanets. Also, many of the smaller telescopes are working around the clock to keep searching for exoplanets. These telescopes are not just on the ground. We also have space telescopes looking for exoplanets, like the Hubble Space Telescope and the Kepler Space Telescope. (From Evan at Koelsch Elementary School in Boise)

8: Is it possible to have two Earths?

Some scientists feel that since we have one Earth that is flourishing with life, they don't see any reason why there wouldn't be similar circumstances in our galaxy where there could be another planet that is very similar to our Earth. It could have life that has taken hold and, perhaps, advancing intelligent life. Although we haven't discovered a planet like Earth yet, we feel optimistic that we will. (From Haylee at Sagle Elementary School in Sagle)

9: Do any exoplanets have rings?

Since exoplanets are so far away, it's very hard to detect something as faint as rings. However, if you look at our own solar system, several of the planets do have rings. There is one example of a planet that was found to have a ring system so large that it's something like a super Saturn. So, there are some planets around other stars with rings. (From Kriste at Liberty Elementary School in Boise)

10: Is Pluto an exoplanet?

Pluto has been the source of many conversations. It is a member of our own solar system and it is referred to as a dwarf planet. So, it is not going to be an exoplanet, because exo, by definition, means outside of our own solar system. (From Beau at Dalton Elementary School in Dalton Gardens)

October 2010

Thanks to Dr. Mark Kuchner, Planetary Scientist, NASA Goddard Space Flight Center for the answers.

1: Is there life on other planets? Could there be another Earth?

We don't know if there is life on other planets yet, but maybe someday we will. There are planets that are similar to Earth. These planets have similar size and mass. Their orbit to the stars is like our orbit to the sun, and maybe they even have similar atmospheres. (From Amber in Mrs. Hunt's class at Cynthia Mann Elementary School in Boise)

2: How do you find new planets?

We have an ever-expanding collection of tools that we use to find new planets. One is the Radio Velocity Technique. Here, we look at a star that is being orbited by a planet. Based on the light spectrum, we can determine if it is moving closer to us or further away. Another technique that has become popular is the Transit Technique. This method blocks out some of the light from a star. When we see the change in a star's brightness, it tells us that there is a planet orbiting the star. A third technique is the Direct Detection. This method can be challenging as planets do not emit very much light. However, a cornograph, used inside a telescope, can enable us to detect planets. (From Megan in Mrs. Schweitzer's class at Riverside Elementary School in Boise)

3: How far are exoplanets?

We don't know how far the farthest one out is, but we have seen planets that are orbiting stars that are as close as only several light years away, maybe 20 or 30 light years away. Meaning, it takes them 20 or 30 years for their light to get to us. That's a short distance to astronomers. With techniques like Kepler, we're looking at stars that are halfway across the galaxy. They may be a thousand times farther away than that. (From Ting-Hsuan in Mrs. Schweitzer's class at Riverside Elementary School in Boise)

4: How do they figure out what to name the planets like Gliese 581G?

Planets are named after the stars they orbit. We look the stars up in a catalog and they usually have a number. That number becomes the name of the planet. Often, it takes a while to be certain a planet really is a planet. (From Gabrielle in Mrs. Hudson's class at Dalton Elementary School in Dalton Gardens)

5: Is Pluto considered an exoplanet?

Pluto is in our own solar system, so it orbits the sun. We consider it a dwarf planet, not an exoplanet. (From Ashley in Mrs. Wheeler's class at Five Mile Prarie Elementary School in Spokane)

6: How long would it take to get to the nearest exoplanet?

For now, we can't get to the nearest exoplanet. The nearest planet is about 20 or 30 light years away, so if we were traveling at the speed of light (186,000 miles per second), then we wouldn't get there for 20 or 30 years. What we mostly think about is not traveling to the exoplanets, but sending and receiving messages from them. (From Emma in Mrs. Hudson's class at Dalton Elementary School in Hayden)

7: What's in between solar systems?

In between solar systems is a lot of empty space. This space doesn't even have air in it. So, if you went there, you would suffocate because there is so little of anything in it. It's really, really empty. (From Jacey in Mrs. Woodall's class at Dalton Elementary School in Dalton)

8: Who discovered the first exoplanet?

The first exoplanet was discovered around a pulsar. A pulsar is like the nucleus of an atom, but it's huge, the size of a star. This discovery was made by Wolshan and Frail in the early 1990s. (From Bailee in Mrs. Woodall's class at Dalton Elementary School in Dalton)

9: Is there a star bigger than the sun?

There are many stars bigger than the sun. The sun is kind of small as far as stars go. There are stars that are so big, if you put one in the middle of our solar system, it would extend all the way out to Earth or even Jupiter. (From Ingrid in Mrs. Edlemier's class at Ustick Elementary School in Boise)

10: What holds the planets in place?

Gravity holds the planets in place. They are all whirling around the sun, and they are held in orbit because of the tremendous pull of the sun's gravity. (From Eva in Mrs. Angie's class at Longfellow Elementary School in Boise)

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