The Sun's angular diameter, as observed from Earth, is approximately 0.5°. This is based on Earth's average distance of 93 million miles (150 million km) from the Sun. From Mercury, at an average ...

This is one of my favorite stories. In short, one of John Burk's (@occam98) students wanted to launch a space balloon. If you want all the details, this post at Quantum Progress pretty much says it ...

Elongation is the angle, in degrees, between the Sun and the planet as seen from here on the Earth. Superior planets (those that lie further from the Sun than us: Mars, Jupiter, Saturn, Uranus, ...

Forbes contributors publish independent expert analyses and insights. The Universe is out there, waiting for you to discover it. Intuitively, we all know that when we see an image of an object, it ...

In my January column, I challenged readers to look for some of the finest naked-eye features on the Moon during lunar perigee — when the Moon is closest to Earth in its elliptical orbit. But have you ...

If you were to compare planet Earth to the Sun, you'd find that you'd have to stack 109 Earths atop one another just to go from one end of the Sun to the other. Yet there are stars out there that are ...

Phobos is the best known irregular satellite in our solar system, but it isn't a squoon. (ESA/DLR/FU Berlin (G Neukum), CC BY-SA 3.0 IGO) Well let’s think about the physics: for a satellite to be ...

Cepheids are a class of variable (pulsating) stars whose absolute luminosities are related in a simple manner to their pulsational periods. By measuring the period and using the ‘period–luminosity’ ...