Planet Nine

High school (ages 12+)
Space & Astronomy

Name:

Date:

Step 1 · Read the article

Open the article and read it at the level above. Then answer the questions below in your own words.

https://smallwhale.org/articles/planet-nine

Write what each word means, using the article.

Do not copy the article. Write two things you learned, the way you would explain them to a friend.

Answers below are taken from the article’s stored facts, so they match what the student read.

1. How big is Planet Nine?A massive planet, potentially a super-Earth or mini-Neptune
2. How heavy is Planet Nine?Five to ten Earth masses
3. What is the primary evidentiary basis?The statistically significant clustering of orbital parameters of extreme trans-Neptunian objects (ETNOs)
4. What is the observational status?Undetected; existence remains conjectural pending direct observation
5. Why do scientists think there might be a planet out there?The strange grouping and paths of some far‑away icy objects suggest they are being pulled by a big unseen planet, so scientists call it Planet Nine.
6. How do scientists look for Planet Nine?They use big sky‑watching telescopes and surveys like WISE, Pan‑STARRS, and the Subaru Telescope to scan the sky, but it is very faint and far away, so it is hard to see.

Extreme Trans-Neptunian Object (ETNO): A celestial body orbiting the Sun at an average distance greater than 250 AU, with highly elliptical orbits.
Perihelion: The point in an object's orbit where it is closest to the Sun.
Orbital Inclination: The angle between an object's orbital plane and a reference plane, typically the ecliptic.
Gravitational Perturbation: The influence of the gravitational force of one celestial body on the orbit of another.