Category Archives: Questions and Answers

Most people have many questions about astronomy, and aren’t happy with the standard answers. Here are some articles trying to change this. If you have any questions you would like to see answered, ask me in an email to the address below, and I will answer your question in an article on this list

What is a satellite?

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When you have two bodies orbiting each other (For example, the Earth and the Moon), we call the smaller of the two the Satellite of the larger.  Thus the planets are satellites of the Sun, the Moon is a satellite of Earth, and so on.  But when most people talk about satellites, they are referring to artificial satellites.  These are manufactured objects which have been launched into space and carefully maneuvered into orbit around something much more massive like a … Continue reading →

How many moons does Jupiter have?

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Current total: 95. I’ll keep updating this page as more get discovered. Details in the UPDATES section below As of 2 February 2012, we know of 67 moons around Jupiter.  We will probably continue to find more and more, as we keep looking, since Jupiter is large enough that it constantly captures passing asteroids and comets, turning them into moons.  The smallest ones are so hard to see, and have such big irregular orbits, that astronomers sometimes lose them, until … Continue reading →

Will we see two suns on 21 June?

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  Edit:  This article was posted on 21 June, the very day that the email discusses.  Obviously it would have been simpler to just say “Stick your head out the window.  How many suns do you see?  Any questions?”, but emails like this tend to get recycled.  Some genius adjusts the date (that “Mars as big as the Moon” hoax has hit my inbox every august for years now) to move the supposed event back into the future, and the … Continue reading →

What is a Supermoon?

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  A Supermoon is a Full Moon which appears larger than usual in our skies.  The Moon’s orbit is not perfectly circular, but is elliptical.  This means that there is a point in its orbit that is closer to Earth than any other (called ‘Perigee’) and a point that is further (‘Apogee’).  The orbit takes 27.3 days, so the Moon is at Perigee exactly once every 27.3 days.  However, the cycle of phases takes a little longer (Because they are … Continue reading →

What is light?

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Dear Urban Astronomer   I just read your article about “what is the speed of light.”  I’m so surprised (and amazed) that light travels faster in a vacuum than in (atmosphere?) – does this mean that LIGHT is actual…”stuff” ? It might sound silly to you, but I find it quite hard to comprehend! Does this mean that light has a “mass”?  It’s very cool, and opens up a whole new world of symbolic drama-movie themes.   Jody     … Continue reading →