“the first star I see may not be a star”
Jimmy Eat World – For me this is heaven

This lyric often gets stuck in my head and was the one that inspired this series of blog posts. This is because it’s often true – the first star you see may not be a star, but instead may be a planet! Full points to Jimmy Eat World for scientifically accurate lyrics!

When the sky gets dark in the evening, the first stars you’ll see will be the brightest ones. There are several really bright stars in the night sky and which of these you’ll see depends on where you are and when you are. We see different stars from different parts of the world, and also at different times of the year as the Earth travels around the Sun. In the northern hemisphere, the brightest star in the night sky is Sirius, the dog star, in the constellation Canis Major. Assuming you’re looking for this first star as it gets dark, it has to be visible in the evening, so look out for Sirius in the winter and spring evenings by following the three stars of Orion’s belt down to the left. In the summer one of the brightest stars you’ll see is Arcturus in the constellation Bootes; find it by following the curve of the Plough down.

As bright as these stars appear to us, they are often trumped by planets. In particular Venus, Mars and Jupiter can all outshine the brightest stars, and Venus is sometimes so bright that you can see it during the day. Astronomers use the magnitude system to quantify the brightness of stars (and other astronomical objects), where brighter objects have a lower magnitude, extending into the negative for the very brightest. Sirius has a magnitude of -1.46, whereas the faintest stars the human eye can see will have a magnitude of around 6. In comparison, Venus can be as bright as magnitude -4.5!

Venus, Jupiter and Mercury at sunset over La Silla Observatory. Credit: Y. Beletsky (LCO)/ESO

So the next time you go out and look up at the stars, why not think of Jimmy Eat World and try to spot a planet instead! At the time of writing (December 2014), Jupiter in particular is starting to become more prominent in the (UK) night sky. By the end of December 2014, it’ll be rising at around 8pm and shining incredibly brightly at magnitude -2.4. If you want to know when it’s a good time to look for planets there are loads of night sky guides online, such as the one by Ian Morison on the Jodrell Bank website (or check it out in audio form on The Jodcast). Alternatively you can download software like stellarium which will show you the night sky at any location and time in the world on your computer.