Tonight, after the sun sets, look west to see a cool astronomical phenomenon: the two brightest planets, Venus and Jupiter, will seemingly collide in the night sky.
Of course, the planets aren't actually hitting each other — in reality, they're hundreds of millions miles apart. But from our vantage point, they've been steadily approaching each other throughout the month of June. This evening will mark their closest pass — scientifically known as a conjunction — as they move within a third of a degree of each other.
Because the two planets are so bright, they can easily be spotted without binoculars or a telescope and can even be seen before night completely falls. Just look to the west, and you'll see the two planets nearly touching, forming what looks like a double star fairly close to the horizon.
These sorts of conjunctions occur because the planets orbit the sun at different rates: it takes Venus only 225 (Earth) days to complete a lap around the sun, compared to 12 (Earth) years for Jupiter. As a result, from our vantage point, they occasionally appear to pass each other in the sky — and if they align just right in a straight line with Earth, they appear to collide.
Here are the two planets' current positions compared to Earth's (their sizes are not to scale):
The planets will gradually drift apart until July 4, when they'll dip below the horizon and go out of view. The next conjunction of Venus and Jupiter will be August 27, 2016.