Dr. Universe explores how scientists measure the mass and size of planets

Washington State University's resident feline scientist, Dr. Universe, takes readers on an out-of-this-world journey to answer a big question from Lucy, 10, of Illinois: How do scientists know the mass and size of planets?

In her latest column, Dr. Universe explains that while planets can't be placed on a scale or measured with a tape, scientists have clever ways to figure out their size and weight. With help from WSU geologist Katie Cooper, readers learn how satellites, gravity, and light from distant stars reveal key details about planets both in this solar system and far beyond it.

The column explores how spacecraft measurements, seismic waves, and telescope data from missions like NASA's TESS help scientists estimate a planet's mass, shape, and even what it's made of. Dr. Universe also takes the time to introduce young readers to exoplanets - planets orbiting other stars - and shows how tiny wobbles and dips in starlight can reveal worlds trillions of miles away.

Ask Dr. Universe is a science education project from WSU that answers real questions from curious kids around the world. Readers and listeners can submit their own questions and explore more columns, videos, and the Ask Dr. Universe podcast online.