What is the brightest object in the sky? Why the Sun of course. Second brightest? The Moon. Most people are able to answer this question quite easily, but what is the third brightest? The fourth? Many people will confidently say Sirius, the brightest star in the sky, or Polaris the north star. The answer is that the planet Venus is third and the planet Jupiter is fourth. It shouldn’t be that surprising that planets hold these positions. They are much closer than the distant background of stars, and the human species has been observing them since the dawn of recorded history. We even realized that they are different, that they move against the background of stars. The root of the word planets in Greek means ‘wanderers.’
Throughout the Spring, we have been able to see Venus dazzling the Western sky after sunset, and Jupiter has been further up in the sky, gradually moving further West each night. By the end of June, the two will undergo a very close pass (at least from our point of view on Earth, they are really hundreds of millions of kilometres apart). They will only be one 3rd of a degree apart, which means you could cover them both up with your finger held up at arm’s length. Pretty amazing show to kick off Summer.
Venus always appears to stay close to the Sun in the sky, since it is closer to the Sun than Earth is. Our perspective never gives it the distance from the Sun it would need to really shine. Jupiter, being further from the Earth than the Sun is, is a true wanderer, travelling through the sky in a predictable but seemingly random fashion. To figure out where it is, you need to know where it is in its orbit, where Earth is in its orbit, and where you’re located on the Earth. Or just use some of the amazing astronomy software out there to do the calculation for you.
Just because the close pass is at the end of the month doesn’t mean you can’t go planet-hunting right now – Venus and Jupiter are visible every clear night in the West, and pretty easy to spot. But how can we tell the difference between the planets and the stars that fill the night sky?
Planets don’t appear to twinkle like stars do. Stars are effectively point sources since they are so far away, so our turbulent atmospheric air can bend and twist their light, while the closer planets have size and can’t be scattered about as much.
If there’s one thing to notice about astronomy, it’s that there is always something amazing to see in the sky, you just have to go out and look. Get a reclining chair and a blanket, maybe a cup of tea, and sit underneath the stars. Watch the life of the universe unfold in front of you and realize how small you truly are in the amazing reality of existence.