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Exoplanets That Could Support Life — Reading Comprehension

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MS-ESS1-2

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This informational science reading passage introduces middle school students to the search for potentially habitable exoplanets. Aligned with NGSS MS-ESS1-2, it explains the criteria scientists use to identify Earth-like worlds: rocky composition, location within the habitable zone, suitable size, and the presence of an atmosphere. Using real examples like Proxima Centauri b, the TRAPPIST-1 system, Kepler-452b, and LHS 1140 b, students learn how astronomers use telescopes such as James Webb to analyze planetary conditions. The passage explores complex concepts such as tidal locking, flare radiation, and biosignatures, showing how these factors interact to determine habitability. The resource includes a glossary, Spanish translations, a differentiated version for struggling readers, comprehension quizzes, writing prompts, and graphic organizers. Audio integration supports diverse learners. This passage helps students connect astronomical discoveries to broader scientific principles and the ongoing search for life beyond our solar system.

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Proxima Centauri b by NASA / Wikimedia Commons

Exoplanets are planets that orbit stars outside our solar system. The search for potentially habitable exoplanets is one of the most exciting areas of modern astronomy. Scientists want to find worlds that might have the right conditions for life as we know it. To do this, researchers look for planets that are rocky, similar in size to Earth, and located in a region called the habitable zone. This zone is the area around a star where temperatures could allow liquid water to exist on a planet’s surface. The presence of liquid water is an important clue because life on Earth depends on water.

How Scientists Identify Habitable Worlds
To determine if an exoplanet could be habitable, astronomers use telescopes to observe the planet’s size, composition, and distance from its star. A planet that is too close to its star may be too hot, while a planet too far away could be too cold. The habitable zone is sometimes called the “Goldilocks zone” because the conditions must be just right—not too hot and not too cold. Scientists also look for planets that are the right size—usually between 0.5 and 2 times the size of Earth—because very large planets may be gas giants like Jupiter, which cannot support life as we know it. Another important factor is whether the planet has an atmosphere. An atmosphere can protect a planet from harmful radiation and help keep temperatures stable.

Examples of Potentially Habitable Exoplanets
The closest potentially habitable exoplanet is Proxima Centauri b, located just 4.2 light-years away. This rocky planet is slightly larger than Earth and orbits a red dwarf star in the habitable zone. However, red dwarf stars can be very active and produce strong flares that send dangerous radiation toward the planet. This could make it difficult for life to survive. The TRAPPIST-1 system is another important discovery. It contains seven Earth-sized planets orbiting a red dwarf star about 40 light-years away. Three or four of these planets are in the habitable zone, making this system a prime target for further study. Kepler-452b is often called “Earth’s cousin” because it is similar in size to Earth and orbits a Sun-like star in the habitable zone, though it is much farther away at 1,400 light-years. LHS 1140 b is a rocky super-Earth that may have an atmosphere and is also in its star’s habitable zone.

Challenges and the Search for Biosignatures
Although these exoplanets meet many requirements, there are still challenges. We do not yet know if any of these planets truly have atmospheres, liquid water, or the right conditions for life. Many planets around red dwarf stars are tidally locked, which means one side always faces the star while the other side is in darkness. This could create extreme temperature differences. Also, frequent stellar flares might strip away atmospheres or make the surface dangerous for life. To learn more, scientists use powerful telescopes like the James Webb Space Telescope to study exoplanet atmospheres. They search for biosignatures—chemicals like oxygen, methane, or water vapor that could indicate life processes.

Discovering potentially habitable exoplanets helps us understand our place in the universe. It connects to larger scientific questions about how planets form and what makes a world suitable for life. As technology improves, astronomers hope to find planets that are even more Earth-like. The search for life beyond our solar system continues to inspire new scientific discoveries.

Interesting Fact:
There are over 5,000 confirmed exoplanets, but only a small fraction are considered potentially habitable!

What is an exoplanet?

A planet that orbits a star outside our solar systemA large moon orbiting JupiterA comet in our solar systemA type of asteroid

Why do scientists look for planets in the habitable zone?

Because these planets are always close to their starsBecause the temperatures allow liquid water to existBecause they are the biggest planetsBecause they have no atmosphere

Which exoplanet is the closest potentially habitable one to Earth?

Kepler-452bTRAPPIST-1eLHS 1140 bProxima Centauri b

What is one challenge for life on planets around red dwarf stars?

They are always gas giantsThey receive strong flares and radiationThey have too much waterThey are too far from their stars

What does 'atmosphere' mean as used in the passage?

An area of strong gravityA layer of gases surrounding a planetA type of rocky surfaceA distant star

What is a biosignature?

A region where planets can't existA sign of a planet's sizeA chemical clue that may suggest lifeA type of telescope

Why do scientists use telescopes like James Webb to study exoplanets?

To look for biosignatures in their atmospheresTo measure the planets' speedTo make the planets brighterTo find asteroids

Which is TRUE about the TRAPPIST-1 system?

It has only one planetAll its planets are gas giantsIt contains several Earth-sized planets in the habitable zoneIt orbits a star like our Sun