January 30, and the days just before and just after, will be a good time to try to see Mercury, as it’s at its greatest western stretch. You don’t need a telescope for this, but you may need to wake up early. Also, the southern hemisphere gets a better view than the northern hemisphere. And as always with stargazing, you’re out of luck if the clouds don’t cooperate.
What is the greatest western elongation of Mercury?
Mercury is an ‘inferior planet’. That doesn’t mean it’s just not that great. For Earthlings, the term simply refers to Venus and Mercury, the planets that orbit closer to the sun than we do. So every time we try to look at one of these planets, we’re sort of looking at the sun instead of out into space.
Why is it called a snow moon? (And when you can see it)
You don’t tend to see Venus and Mercury too often, as they hug the sun, an object exponentially brighter in our sky – as you’ve probably noticed.
But if an inferior planet is at or near one of its “greatest elongations” (each inferior planet has an eastern and a western “greatest elongation”), you have a good chance of seeing it. Because it’s at a point of the greatest (deep breath) angular distance from the sun to Earth – so it’s not necessarily at the greatest distance from the sun in its entire orbit, but that’s what it looks like to us earthlings, and therefore, it will appear brighter and last longer.
How can I see Mercury at its greatest western elongation?
You will need to look at the sun at dusk just before sunrise or just after sunset. If you have a reasonably clear line of sight to the horizon, Mercury should be there, a tiny speck in the clown near where the sky meets the land. To distinguish this tiny, faint planet from any stars that might be visible, it may help to download a stargazing app with an augmented reality component. SkySafari(Opens in a new window) is an example of such an app.