Why Are Stars And Planets Spherical When Galaxies Seem Flat?

24 April 2019, 16:03

Milky Way
Picture: PA

Question: Why do stars and planets appear spherical when galaxies are flat?

Name: John, Oxford

Qualification: Amateur Astrophysicist

Answer: Galaxies aren’t completely flat. At the centre of every galaxy is a black hole, which is very dense matter that pulls everything towards it. That black hole is moving through space and spinning very fast.

The black hole is pulling our solar system towards it, while the solar system is also spinning around the black hole and travelling through space.

The earth and the sun are both spherical, but if we could see the black hole it would also be sphere-shaped. It’s pulling us towards it and we’re spinning around it, and the black hole is also travelling through the universe at speed. That’s why the black hole appears to be flat even though it isn’t.

Planets appear spherical because there’s an equal pull of gravity on all parts of them.