What Is an Exoplanet?

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An exoplanet is a planet that orbits a star outside of our solar system. These planets are located in other star systems and are not part of our own planetary system. Exoplanets come in a variety of sizes and compositions, ranging from rocky planets similar to Earth to gas giants like Jupiter. Scientists study exoplanets to learn more about the formation and evolution of planets, as well as to search for signs of life beyond Earth. The discovery of exoplanets has revolutionized our understanding of the universe and has opened up new possibilities for finding habitable worlds.


Are you someone who likes to imagine and ponder about the existence of other worlds while sitting under the stars at night? Have you ever wondered if there are other planets with life somewhere in the vast universe?

When astronomers discovered the other planets in our solar system, it sparked curiosity about the possibility of life on those planets. As scientists learned more about the planets orbiting the Sun, it became evident that Earth was unique and the only planet capable of supporting life.

While this realization might have satisfied some, astronomers are a curious bunch and don’t limit their exploration to just our solar system. They know that there are billions of other stars like our Sun scattered throughout the universe.

With such a vast number of stars, astronomers began searching for planets similar to Earth in the vicinity of these stars. Is there a planet like Earth, with perfect conditions for life, orbiting another star? It’s a possibility!

Astronomers refer to these planets that orbit other stars as “exoplanets,” short for extrasolar planets. To date, scientists have discovered exoplanets of various sizes. Some are much larger than Jupiter, while others are smaller than Earth.

Scientists have also found similarities between other solar systems and our own. For instance, they have observed that exoplanets can orbit their stars at different distances. Some exoplanets are so close to their stars that their surface temperatures could melt iron.

There are also exoplanets that orbit at just the right distance within their star’s habitable zone, a zone where temperatures would allow liquid water to exist on the planet’s surface. The presence of liquid water is considered a key factor in the formation of life.

Unfortunately, observing exoplanets from Earth is challenging. Exoplanets are relatively small and dim compared to the bright light emitted by the stars they orbit, making them difficult to detect. Scientists have developed an indirect method called the “transit method” to discover exoplanets.

Based on the understanding that exoplanets orbit their stars similar to how Earth orbits the Sun, scientists predicted that exoplanets would regularly pass between their stars and Earth. By monitoring the brightness of stars over long periods of time, scientists can identify periodic decreases in brightness that correspond to exoplanets orbiting them.

Although astronomers have long believed in the existence of exoplanets, the first confirmed exoplanets were discovered in the 1990s. Since then, over 2,000 exoplanets have been identified, with over 1,000 of them being discovered by NASA’s Kepler space telescope alone.

Launched in 2009, the Kepler space telescope used the transit method to search for exoplanets for four years. Even though its primary mission has concluded, the Kepler space telescope collected an extensive amount of data, and scientists are still uncovering new discoveries from that data today.

Try It Out

Are you ready for an adventure into deep space? Get ready and explore the following activities with a friend or family member:

  • Head over to the NASA website and explore a planet similar to Earth, known as an exoplanet. Would you be interested in joining a manned mission to investigate exoplanet Kepler-452b? What do you think you would discover there?
  • Do you believe there is life on other planets beyond our solar system? Deep down, what is your opinion? Yes…or no? Explain your reasoning to a friend or family member. If you do believe in extraterrestrial life, do you think humans will ever make contact or establish communication with these beings? Provide reasons for your answer.
  • Is it worthwhile to search for life on planets outside of our solar system? Advanced telescopes come with a high price tag. Could the funds allocated for this research be better used elsewhere? Discuss the topic of money spent on such studies with friends and family. Consider the pros and cons. Do the potential benefits outweigh the costs?

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