Comet, snow moon and eclipse ′trifecta′ have the potential to disappoint | Science| In-depth reporting on science and technology | DW | 10.02.2017
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Comet, snow moon and eclipse 'trifecta' have the potential to disappoint

Stop the hyperbole, please. The combination of a comet, a "snow moon" and a penumbral lunar eclipse on February 10 is actually a coincidence of two events, not three - and none are worth looking for.

Nothing's worse than disillusioning a potential astronomer.

And the overnight events between Friday, February 10 and Saturday, February 11, all bundled together and marketed as a "spectacular triple treat," have the potential to do just that.

Let's take a look at the "coincidence" of celestial happenings.

Snow moon

How do you envision a "snow moon?"

I imagine the bright white moonshine of a crystal clear full moon atop freshly fallen snow powder, turning night into almost-day and everything into winter magic.

But that's not what a snow moon is.

A snow moon is a full moon that happens in February.

In other words, it is a regular full moon - it just happens in February.

That is meaningless.

meaningful February event could, for example, involve no full moon whatsoever for the entire month. That's possible given the moon's roughly 29.5-day period and February's 28 days (or 29). The last time this happened was 1999. It will happen again in 2018.

So next year, we will have no "snow moon." And that is something to celebrate.

Penumbral lunar eclipse

It's hard to hear "penumbral lunar eclipse" without accidentally imagining a "total lunar eclipse."

The latter is an event that darkens the moon to a sinister deep red and gives the night-time sky a sort of biblical menace. In 2015 we even had a "super blood moon," when a lunar eclipse occurred just as the moon was at its largest. That was genuine fun.

But a penumbral lunar eclipse means that only part of the sun's light is blocked by the Earth's sphere. The moon will only be slightly fainter, and just on one side.

That is a nice lesson in physics. It's not, however, visually exciting. Just look at the photo of a penumbral lunar eclipse below.

Penumbrale Mondfinsternis (gemeinfrei)

The left one is the penumbral lunar eclipse

Comet 45p

That takes us to a celestial event that occurs every five years or so and is usually worth trying to find.

Comet 45P will come closest to our planet overnight between February 10 and 11.

How close is close? Compared to our own moon, Comet 45P will be about 30 times further away.

That's far enough that you'll need very powerful binoculars at the very least - a good telescope would be better - to have any chance at seeing the beautiful green and blue hues this comet has to offer.

But here's the catch - and it's a very big one.

The reason the picture above was taken on December 23 is because there was almost no moon in the sky that night. It was just before a "new moon," so the moon was almost entirely black - ideal conditions for catching a comet reflecting the sun.

Now, remember our dear friend, the so-called snow moon?

Any full moon is the enemy of a stargazer. A full moon whitewashes the starlight out of huge swaths of the night sky. Serious stargazers avoid full moons unless the moon itself is the source of the gazing.

This is why the "trifecta" of stargazing opportunities on offer this February 10 are in fact a self-canceling basket of pure nonsense. The best a casual observer is likely to get out of all of this is a simple full moon, one that's a tiny bit darker than normal. There is a very real risk that a potential astronomer, hyped by the headlines, will walk away feeling literally and figuratively cool.

So here's a tip from a friend at DW: Check out Venus. It's really bright right now, and it'll appear in the west, far away from that spotlight of a full moon. Just follow the sunset and you won't be able to miss it. About a week later, on February 16 and 17, Venus will be at its brightest point of the year. And that is actually an event worth looking forward to.