Ask Astro | Page 4 of 22 | Astronomy.com

Hubble image of variable star RS Puppis

How do Cepheid variables indicate distance?

Exotic Objects, Solar System

What are the chances of dark matter or a black hole ripping apart Earth?

The Moon rises over mountains in Utah. Credit: NASA/Bill Dunford.

Science, The Moon

Why does the Moon look so large sometimes as it rises on the horizon?

Artist's rendition of asteroid Psyche

Could Psyche be the core of the planetesimal that struck Earth and formed the Moon?

The expanding universe

How can the visible universe be 46 billion light-years in radius when the universe is only 13.8 billion years old?

Merging black holes

When black holes merge, is the diameter of the new black hole bigger?

There isn’t a scale large enough to weigh galaxies like NGC 7714. ESA, NASA; Acknowledgement: A. Gal-Yam (Weizmann Institute of Science)

Ask Astro: How do scientists weigh planets and other celestial objects?

HST image of Jupiter near opposition

Science, Solar System

How old is each planet in our solar system?

Artist's concept of Planet X

Could we find Planet Nine using JWST?

Location of Jupiter's Trojan asteroids

How closely packed are Jupiter’s Trojan asteroids?

When stars “die,” they leave one of two objects behind. Massive stars explode as supernovae, creating remnants of gas and dust like the Crab Nebula (M1). Credit: ASA, ESA, J. Hester and A. Loll (Arizona State University)

Milky Way, Stars

How many stars die in the Milky Way each year?

The very center of globular cluster NGC 6397

How do globular clusters remain intact for so long?