On Thursday night/Friday morning, the Moon will slide into Earth’s shadow, creating a total lunar eclipse! These are fun events to watch since they’re rather slow — it takes over 3 hours for the partial and total phases to play out — and you don’t need any equipment or (unlike a solar eclipse) special eye protection.

I wrote about how this all works for Scientific American, and also in a special article for Condé Nast Traveler. I also wrote about the mechanics of this for the November 2022 eclipse in BAN 483 (so for this week’s eclipse read the general stuff but ignore the times for the older event). I go into even more detail in my episode of Crash Course Astronomy about eclipses (the part about lunar eclipses starts at 6:54):

The eclipse is visible to essentially all of North, Central, and South America. The show is probably better for people farther west, who can still see the whole eclipse, but it happens at an earlier time for them. Here are the UTC timings for it:

Penumbral begins: 03:57
Partial begins: 05:09
Totality begins: 06:26
Totality ends: 07:32
Partial ends: 08:48
Penumbral ends: 10:00

Those times are to the nearest minute in UTC. Now that we’ve had the time change, the US east coast is UTC – 4, so for example the partial phase of the eclipse starts at 01:09 Friday morning. Kinda late. But for west coasters it starts at the much more civilized 10:09 p.m. Thursday night. Way better. You can find UTC converters online.

As for the phases, technically the Moon enters Earth’s shadow at 03:57, but that’s the outer, weaker shadow called the penumbra, so you likely won’t notice the Moon getting darker until shortly before the partial phase begins. That’s when the Moon enters the darkest part of the shadow, called the umbra, and it starts to look like a bite is being taken out of it. Totality is when the Moon is completely ensconced in the shadow, turning totally dark; or as I explain in the SciAm article and CCA video, it will likely turn blood red as the Sun’s light is filtered through Earth’s atmosphere, scattering away or absorbing all the blue light, only letting red through to illuminate the Moon. That the coolest part of the eclipse, so hopefully you’ll get a chance to see that.

I hope you get clear skies and a good afternoon nap the day of. You’ll likely need both for this one!

I don’t often show y’all graphs of data — I know a lot of people have a hard time with them — but I saw this one and just had to write about it.

Remember the asteroid 2024 YR4 from February? We knew it was going to get close to Earth in 2032, but not sure how close. Astronomers couldn’t rule out an impact, though the chance was low.

The European Near-Earth Object Coordination Centre newsletter for March 2025 had this plot, which shows how well we knew where YR4 would be in December 2032. I’ll explain it below.

The graph shows the predicted distance from Earth of the asteroid at closest approach in December 2032. The dates along the bottom are the days each prediction was made. So, each point represents the position of the asteroid at closest approach that was predicted on that date, given the observations in hand at that time.

The vertical y-axis shows that distance from Earth in units of lunar distance, the distance to the Moon (about 380,000 km). The size of the Earth is shown in the gray bar going across the middle (at y=0), although I think it’s exaggerated a bit vertically.

There are a few things to note. One is that the dots are the actual best estimate of the asteroid’s distance. But note the “error bars”! These show how well we understand that position; the larger the bar the less certain we can be. Statistically speaking, the bars represent what scientists call the three-sigma uncertainty; the easiest way to understand it is that there’s a 99.7% chance the asteroid will be somewhere between the top and bottom of the bars.

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