Subscribers make visible impact flashes in my life

As I wrote in BAN Issue #1042, the upper stage of a Falcon 9 rocket is going to hit the moon next week, on August 5, 2026. The impact time is predicted to be 06:34:33 UTC (02:34:33 Eastern US time). The upper stage will impact near the crater Einstein in the northwest portion of the moon, which, unfortunately, will be lit by the sun at the time. That will make seeing any impact flash difficult.

But not impossible! A paper has come out detailing the event, and the plans to observe it. It’s not likely to be visible by amateur telescopes, but hey, “amateurs” have pretty sophisticated equipment these days, so I would encourage anyone with a good setup and some experience give it a try. You’ll need to take video — the flash will be very brief, so capturing it during a short image exposure of the sunlit moon is extremely unlikely. The paper also talks about how to share data if you get any. 

If you need more details, Bill Grey’s amazing Project Pluto site has what you need, including prediction times, maps, and more.

The Falcon 9 rocket launched on January 15, 2025, taking two landers to the moon. The upper stage used up all its fuel boosting the missions, which left it on an elliptical orbit around Earth that took it past the moon. On this elliptical orbit, it moves most rapidly when it drops down to Earth, and more slowly when it’s at its apex (called apogee). This makes it hard to observe, since that means it spends most of its time far from telescopes. Still, enough observations were made to calculate a decent orbit for it, and predict when it will impact.

Smart starts here.

You don't have to read everything — just the right thing. 1440's daily newsletter distills the day's biggest stories from 100+ sources into one quick, 5-minute read. It's the fastest way to stay sharp, sound informed, and actually understand what's happening in the world. Join 4.5 million readers who start their day the smart way.

Join for free today!

Why will it make a flash? Kinetic energy! That’s the energy of motion. Think of it this way: when you throw a baseball, the more energy you give it the faster it moves. When you catch a ball, that energy is transferred to your hand, making a loud noise and rocking your hand back.

An object in space tends to be moving much more rapidly, and when it impacts something that energy released is much higher. This creates a lot of heat, and the resulting fireball makes visible (and infrared) light. The faster the object, or the higher its mass, the brighter the flash. 

It gets complicated though. As the scientists point out in their paper, the rocket booster is moving at only about 2.4 km/sec, which is actually slow compared to most natural impacts, like asteroids, which can hit at over a dozen km/sec. At such low speeds the flash is much fainter due to the physics of how the energy is transferred to the surface, so even though the booster, with a mass of 4 metric tons, is much more massive than most natural lunar impactors (which we’ve seen!) the lower speed makes the brightness very difficult to predict.

I personally won’t be hauling my butt out of bed for this, but hopefully many other astronomers will. These sorts of impacts are extremely useful in understanding the moon’s geology; since we know the mass and velocity of the object, that narrows down a lot of uncertainties in the impact, making the event generated is easier to analyze and interpret. These rocket impacts have happened before and will happen again — the linked paper has an excellent history of such things — and being able to predict and study them is a boon to lunar studies. 

It also helps understanding of space debris, which is getting to be a bigger and bigger problem (not to put too fine a point on it, but a lot of that is also thanks to SpaceX). So the more eyes on this the better.

Tip o’ the Whipple Shield to my friend and astronomer Jonathan McDowell on Bluesky for pointing out the paper.

• JWST observations of the interstellar comet 3I/ATLAS show that it is very old indeed [link to journal paper]. It has a very high ratio of heavy water (where the hydrogen atoms have an extra neutron, making them deuterium), about 20 times what’s normal for solar system comet. For ices, deuterium forms in very cold environments where there’s a lot of radiation around. That indicates it formed very far out from its parent star in a region with high star formation rates. Also, a low ratio of heavy elements in it indicate the comet formed when the universe was much younger, likely 10 – 12 billion years ago.
  

• The Hadean era on Earth covers the period from its formation to about 4 billion years ago. It’s hard to study because there are no extant rocks found that date back to that era. Why not? Until recently this was blamed on tectonics, but a team of scientists suspected impacts may also be to blame, so they modeled how impacts at that time affected the crust [link to journal paper]. What they found is that impacts were so common and so severe they actually added more heat to the crust than the internal heat of Earth itself! This kept the crust thick and partially molten, erasing any geologic surface records from that time.

You can email me at [email protected] (though replies can take a while), and all my social media outlets are gathered together at about.me. Also, if you don’t already, please subscribe to this newsletter! And feel free to tell a friend or nine, too. Thanks!