You're out one evening and a bright object in the sky catches your attention. What is it? A planet, a star, a satellite, maybe a comet or shooting star, or maybe it's a UFO? It could be any of these and more but read on before you phone in that UFO sighting...
If you are outside at night for a walk or a drive and the sky is clear, it doesn't take long before you notice lights in the sky. Whether you are in the country or the city, with a clear sky you will see things in the sky that are not terrestrial in origin and the brighter they are, the greater the chance that you will notice them. The variety of objects visible to you in the night sky varies greatly depending on your location. In the city, with all the ambient light from street lamps, cars, buildings and signs, your night vision is severely limited but you will be able to spot some of the brighter planets, and a few stars, the Moon and even a shooting star if you are lucky.
What's up there? Many wondrous things! There are many objects that might be visible and get your notice. The planets Venus, Jupiter, Saturn and maybe Mars and even Mercury may be bright enough to garner your attention.
Venus is the queen of the planets and under the right conditions can have a magnitude approaching -4.5. (Note that the more negative the magnitude, the brighter the object: the full moon has a magnitude of -12.5, which appears almost 1700 times brighter than Venus and the sun is -26.7. For more about magnitude read Magnitude and How it Works.) Jupiter, the largest of the planets and the fourth brightest object in the sky, can reach a magnitude of -2.9 with Mars next at -2.8 with a distinct reddish hue. The elusive Mercury, which when it can be seen, is always very low in the sky, near the sun at sunrise or sunset and it can reach -1.5. Saturn, the ringed planet, rounds out the list of naked-eye visible planets with a magnitude of -0.3. As a point of reference the human eye can only make out stars down to a magnitude of +6 (remember, the more negative the magnitude, the brighter the object) .
The inner planets, Mercury and Venus will always be relatively low in the sky and be visible in the evening or morning because of the geometry of their orbits and the Earth's. The outer planets, Mars, Jupiter and Saturn can be seen throughout the night from evening to morning and can appear in the sky anywhere from horizon to zenith (the point in the sky directly above you). This is also due to the geometry of their orbits and the Earth’s.
There are a few stars that stand out prominently in the night sky but not quite as bright as the planets, except for Sirius, the Dog Star in the constellation of Canis Major, which shines at a magnitude of -1.42—brighter than Mars but not quite as bright as Mercury. Next in brightness is Canopus, which is in the constellation of Carina and has a magnitude of -0.72. At -0.27, the Alpha Centauri star system is next in order of brightness. This system is also the closest stars to our solar system at a distance of 4.3 light-years and can be found in the constellation of Centaurus. Arcturus is fourth on the list with a magnitude of -0.04 and is in the Bootes constellation. In the constellation of Lyra resides the star Vega, which shines at a magnitude of 0.03. Capella has a magnitude of 0.08 and is the brightest star in the constellation of Auriga and is followed by Rigel at 0.12 in the constellation of the Hunter – Orion. Orion also possesses the red giant Betelgeuse, which blazes at a magnitude of 0.5.