BAN #277: Moon blocks Venus, Goodnight Exomoon

7 December 2020   Issue #277

[Spiral Galaxy M81 image credit: Adam Block/Mount Lemmon SkyCenter/University of Arizona]

Subscribers get a chance to dabble in the occult(ation).


As Dave Barry said, “Poli” = many and “tics” = blood-sucking parasites

If you live in Georgia, know someone who lives in Georgia, or perhaps most imporantly know a 17-year-old Georgian who will turn 18 on or before January 18, be aware that today (Monday Dec. 7) is the last day to register to vote for the runoff Senate election. This election is MASSIVELY important; if the two Democrats running win then the Senate will be essentially 50 R and 50 D, and incoming Vice President Kamala Harris will cast the tie-breaking vote. If you want to see the government actually do something, something good, then please make sure as many Democratic Georgians are regiestered to vote as possible, and then urge them to vote as well.


Putting my money where my mouth is: My wife and I wrote 200 letters to voters to urge them get out and vote come January 5. We did this as part of Vote Forward, so please check them out if you want to do more.

GOP Trump lickspittles Loeffler and Purdue are hugely corrupt and need to go. Mitch McConnell’s power needs to be stripped away, and then finally we can make real progress on crucial issues like COVID relief, climate change, and about a billion others.


What’s Up?

Look up! There’s stuff to see in the sky!

This coming Saturday, 12 December, an unusual and very cool event will occur: The Moon will pass directly in front of Venus, blocking the more distant planet. This event is called an occultation.

The planets orbit the Sun more or less in the same plane, called the ecliptic. The Moon’s orbit is tilted by about 5° with respect to the ecliptic, so a planet has to be at one of those two spots where they intersect on the sky at the same time the Moon is; that’s why an event like this is relatively rare.

[A map showing where the occultation is visible. Inside the teal loop in the US you can see the start of the event but not the reappearance of Venus before Moonset. For the loop in Russia you miss the beginning but can see the end. Above the red line it all happens during the day; blue at twilight, and white at night. Credit: IOTA]

The occultation is visible in a limited region of Earth; pretty much west of Denver over to far Eastern Russia. In the eastern US the Moon sets before the occultation, so you miss it. The farther west you are the better; west of about Great Salt Lake you can even see Venus re-appear on the other side of the Moon.

I’ll be able to see the actual occultation, but only the first part; the Moon will only be a few degrees above the horizon for me when it happens (and I lose a degree due to the mountains to my west blocking the true horizon). It happens around 2:20 in the afternoon for me Mountain time.

The exact time the Moon first blocks out Venus depends on your location. If you’re in the zone where you can see it, Earth and Sky has some example times, but you should go to software like Sky Safari (for mobile devices; the basic version is 3 bucks and I use it all the time) or Stellarium (for the web), put in your exact position, and see what’s what. In-The-Sky has more info about this as well.

[A simulation of the view I’ll have from Boulder County in Colorado; note the Moon will be only 7° above the horizon! Credit: Sky Safari]

It’ll be tough to see, to be honest. The Moon will be an extremely thin crescent just 25° west (to the right) of the Sun, making it tough to spot. I plan on using binoculars to find it, being VERY CAREFUL not to look anywhere near the Sun, and then maybe using my telescope to watch. I’d love to do it live online using Periscope (which gets pushed to my Twitter account, so if you follow me there you can watch), but no promises. It depends on weather, how well I can get set up, if I don’t hurt my back between now and then, etc.

I’ve seen the Moon occult Venus a couple of times, and it’s pretty fun to watch. They get closer, and closer and cloooooseeeerrrr, then over the course of a few seconds Venus dims and goes out (it takes a moment for the motion of the Moon to cover the whole planet).

Just so’s you know, Venus will be 222 million kilometers from Earth and the Moon about 361,000 km from us when it happens. That should give you a sense of perspective!

So if you can, give this a try. Even if you aren’t in the right place to see it, the Moon and Venus will be very close together all that day, so try to take a look. You don’t often get a chance to see an event like this.

[Note: I almost missed hearing about this. I was playing with Sky Safari, seeing if the Moon would be doing anything interesting in the next couple of weeks when I saw it pass in front of Venus! I yelped in surprise. It pays to play around sometimes.]

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Blog Jam

What I’ve recently written on the blog, ICYMI

[A still from the video of the catastrophic collapse of the platform above the Arecibo radio telescope. From Wednesday’s article. Credit: Courtesy of the Arecibo Observatory, a U.S. National Science Foundation facility.]

Monday 30 November, 2020: Don't panic, but we're 2,000 light years closer to the Milky Way's central black hole than we thought

Tuesday 1 December, 2020: Release the Kraken! Huge methane lakes on Saturn's moon Titan run deep.

Wednesday 2 December, 2020: An ancient star city circles our galactic twin. In fact... it's *too* ancient

I updated an older post about the object 2020 SO since it was confirmed to be a rocket booster and not an asteroid: A near-Earth asteroid passing us in December may actually be an old Moon rocket

Thursday 3 December, 2020: Like a runaway locomotive, NGC 1265 is leaving a 'smoke' trail behind it

I wrote an extra blog post this week due to the collapse of the Arecibo radio telescope, including footage: Watch footage of the devastating collapse of the Arecibo observatory telescope

Friday 4 December, 2020: Gaia’s map of the sky — with two *billion* stars

I recommend

Something I think you’ll like

[Note: The holidays are coming, so I’ll be throwing in some suggestion until it’s too late even for panicked procrastinators. Also, the links in this article are affiliate links.]

[The cover of Goodnight Exomoon by Kimberly Arcand]

When my daughter was but a wee one and not the adult who goes to college and writes way better than I did at her age, we would read to her every night like every parent does for their kids. Of course we had a copy of Goodnight Moon, but it was never really her (or our) favorite. I mean, it’s fine, but she had others we all liked better.

If only my friend and astronomer Kimberly Arcand had written her children’s book Goodnight Exomoon earlier! It’s a cute parody of the classic, with astronomy terms instead of, um, bowls of mush and mittens. She replaces them with meteorites, micrometers, interns, and, of course, the titular exomoon (a moon orbiting an exoplanet, a world around another star). The drawings, by artist Kelly Kennedy, are well done, too.

If you have a science-loving friend with a young child or you have one yourself, then this is a good book to have. Bonus: It’s not terribly long, which is good for those nights when you need something short and sweet.

It’s available at Amazon, Barnes and Noble, and probably other places as well.

Et alia

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