So I saw many planets and they looked just a little bit brighter than they do from Earth - Sally Ride
Even though there are one thousand million stars in our galaxy, the Milky Way, most of which are thought to have planets orbiting them and there are a further one hundred billion galaxies in the observable universe, the only planets that most of us will ever be able to see without the aid of the most powerful telescopes on the planet, are those that make up our own solar system.
That means that there are eight (it used to be nine until Pluto was officially downgraded and is now regarded as being a dwarf planet) planets that we can see in the night sky at any given time.
Or, there would be if it wasn’t for the distance they are from Earth and their relative size and position in the solar system, which when taken into account means that there are only five planets (not including our own) that we can see in the night sky at any given time.
The Five Observable Planets
Due to their size and relative (in galactic terms) proximity to Earth, the five planets that can be seen in our solar system are Mercury, Venus, Mars, Jupiter, and Saturn.
That means the two planets that are closest to the sun, and the next three that are closest to Earth are the worlds that are most easily observable within our solar system.
The world's closest to the sun, Mercury and Venus are known as the inferior planets because their orbits take them closer to the sun than Earth’s does, which means that they orbit the sun far faster than we do, and as such move across the night sky relatively quickly.
It also means that, much like our own moon, they have distinct phases (meaning that at various times, they’ll be observable in crescent, half, and full aspects dependent on their position in the sky) and we can only see the side of the inferior planets that isn’t facing the sun.
The three of the five observable planets that orbit the sun at a greater distance than Earth (or are further from the sun than our world is), Mars, Jupiter, and Saturn are known as the superior planets and because they are much further away from the sun than Earth is, they move across the night sky at a much slower pace than the inferior planets do.
Because of this, we only ever see the sides of the superior planets that are always facing the sun, which is what they always appear in their full (round) aspect.
The Best Times To See The Five Planets
As all of the five observable planets have their own distinct orbits, there are times when it’s easier to see them, and there are times when it’s far more difficult and almost impossible to see them.
During a planetary opposition, when one of the five planets is on the same side of the sun as Earth and its orbital transition means that it is in a direct line of sight with our world, that planet is at its closest and that means its relatively easy to see from Earth.
However during planetary conjunction, said planet’s orbit has taken it around the far side of the sun, which means that it is at its furthest point from Earth and because the sun is directly between us and that world, it’s incredibly difficult to see it.
All of the five planets have different oppositions and conjunctions which makes them easier, and more difficult to see at different times during the year.
Which Planets Can I See Tonight?
Let’s start with the inferior planets and work our way out from the sun to the superior planets.
The best months, thanks to its close orbit around the sun to see Mercury are January, March, May, July, September, and October.
And thanks to its proximity to the sun, Mercury is always incredibly low in the sky and more difficult to see at night than it is during the day, and this means that the best time to catch a glimpse of this elusive little planet is just before sunrise and immediately after sunset.
Thanks to its orbital path, Venus is usually visible throughout January and from May through to December, As it takes longer to travel around the sun than Mercury does and because it’s larger than its neighbor, it’s easier to see and is the second brightest object in the night sky after the Moon.
Appearing on the Western horizon in the night sky and the Eastern horizon during the early hours of daylight, Venus is easily observable with a telescope or a good pair of binoculars. Just look for the brightest star in the sky, which without a shadow of a doubt, will always be Venus
The first of the superior planets that can be seen within the naked eye, Mars has always been an endless source of fascination for the inhabitants of Earth.
Visible for ten months of the year (the only time we can’t see it, is when it’s in conjunction during September and October), Mars distinct reddish glow is a distinct giveaway, and when seen through a telescope, it’s desolate but hauntingly beautiful image is one that all astronomers fall in love with.
Another world that can be seen from Earth for five-sixths of the year, the only time that we can’t see Jupiter is during its conjunction which occurs in January and February.
Despite the fact that it’s much further away from Earth than Mars is, because it’s nearly one thousand times bigger than the Red Planet, it’s actually much brighter in the night sky.
If you want to see Jupiter, cast your eyes skyward toward the constellations of Aquarius and Capronicus, and the incredibly bright star that’s situated between them? That’s Jupiter.
Much like Jupiter, Saturn’s period of conjunction lasts from January to February, and even though it’s seven hundred and forty-six million miles from Earth, due to the gas giants’ sheer size, it’s easy to see in the night sky.
Admittedly, it’s easier to see it during the second half of the year, but when you do look up at the night sky, the brightest object in the middle of Capronicus? That’s Saturn. And if you think it looks incredible without a telescope, try focusing on it with one.
It’s a breathtaking sight that will change the way you think about the planets and astronomy forever. The first time that you see its planetary rings, is a moment that you’ll remember for the rest of your life.