Moon Size

I hate the term ‘supermoon’. In fact that is the only time I’m going to use that term during this entire post.  The Moon does appear a tiny bit larger in the sky, but it’s not an uncommon thing.  Here’s why this one was particularly good at driving headlines. The technical term for the full Moon we saw this past week is a ‘perigee syzygy,’ which I think sounds way cooler.  Perigee is the term for the Moon’s closest point to the Earth in it’s orbit, and syzygy is the term for an alignment of bodies in space, in this...

Atmospheric Spectral Shift

Why does the Sun seem red near the horizon? Why does the Moon do the same?  We know the Moon isn’t actually changing colour, and the Sun isn’t either.  So what is happening to the light? The first thing to note about the image above is that the size of the Moon doesn’t change, showing that the well-known ‘Moon Illusion,’ where the Moon appears larger near the horizon, is just that – an illusion.  The second is of course the gradual change in hue as the Moon rises. The reason for the colour shift really has nothing to do with the Moon...

Everlasting Light

Light is beautiful.  It illuminates a world of beauty for us to appreciate while giving us a tool to decipher the riddles of the universe.  In astronomy, it’s always about more photons! Because more photons = more data = better results.  But in an increasingly technological world, more photons can be a bad thing.  Especially when the artificial photons overpower the natural. I was lucky to spend most of my youth living away from the bright lights of the city, but with the sprawling metropolis of Toronto to the South, I could always see the orange glow that blocked out...

Mercury Surprises

One of the most fascinating things happens whenever I show someone the planet Mercury in the sky. Their first reaction is to be surprised at how bright it is.  Most people think of Mercury as a faraway planet, too close to the Sun to see at all. But in reality, Mercury is close to Earth, and when the angles are just right, it’s not hard to find. Mercury is 57 million kilometers from the Sun, more than a third of the way to Earth.  We are also much closer to Mercury than we are to Jupiter and Saturn. When we see the...

Polar Asterisms

Have you ever seen the North star, Polaris? It’s decently bright and very close to the North celestial pole.  Lining up with the rotation axis of the Earth, the North celestial pole is the point in the sky that never moves, day or night.  If you know how to find Polaris, it becomes easy to find the cardinal directions and navigate by the stars. And finding it simply requires finding the big dipper, a bright and easily recognizable object.  The same rules apply in the southern hemisphere.  But even though there is no southern star, there is another fantastic object in the South that can guide you to the...

Planets to See: September 2015

Lovely Earth is not entirely lonely.  We have five planets that have been observed since the dawn of civilization.  The five are visible with the naked eye in the sky at different times of year, and were given the name planets as a derivation of the Greek ‘planetes,’ meaning ‘wanderers.’  They do wander, or at least they appear to move against the background of the stars, since they are much closer to the Earth as it orbits the Sun. So what planets are visible this month? For September 2015 and back to school, you had better be willing to get...

Where are you? The Moon can tell you!

I was out on a sunny day a few weeks ago waiting for a bus, and as per usual I have my head up in space (I would say up in the clouds but that is too low for me).  I noticed the Moon up in the sky, just past first quarter, and I was thinking about the angle of the illuminated side and how it related to some of the positions of the Earth and Sun in space.  I wondered what information we could gather from the way it looked.  It led me to this ‘illuminating’ post. I realized...