BAN #197: BAHFest Houston, Daylight fireball

02 March 2020   Issue #197

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

Subscribers light up days and nights.

Upcoming Appearances/Shameless Self-Promotion

Where I’ll be doing things you can watch and listen to or read about

A reminder for Texans: BAHFest Houston is Sunday, March 8, at 7:00 p.m., at Rice University. It’s a night of science humor and trust me, it’s very, very funny. Several people compete to present the most ridiculous explanation of an actual scientific observation, and their defense must not only be internally consistent — even if, and perhaps especially if it’s externally nonsense — but also funny. I have been to two of these, and laughed myself silly. The presentations are brilliant.

I’m not only judging but also giving the keynote, such as it is. I’ve been finishing up my talk and it’s made me laugh. I know the science is solid… at least the parts I’m not purposely keeping hidden because they contradict my thesis.

This event is run by Zach and Kelly Weinersmith, which should be enough to get you running to buy tickets all by itself. If you’re in the area, treat yourself.

Astro Tidbit

A brief synopsis of some interesting astronomy/science news that may be too short for the blog, too long for Twitter, but just right (and cool enough to talk about) for here.

A couple of days ago (28. February) a decently big fireball burned up over Slovenia and Croatia in the morning after sunrise, yet still easily bright enough to see. In fact, it was caught on many cameras. This video shows how spectacular it was:

The NASA fireball page reports it was moving at 21.5 km/sec and exploded with a yield of 0.34 kilotons of TNT (a standard unit of energy release used in nukes for example; in this case equal to roughly a trillion Joules). I calculate that it had a mass of roughly 4 tons and a diameter (assuming it was rocky) of roughly 1.5 meters. So, lounge-chair-sized (also a standard unit of meteoroid size, which goes up from grain of sand to grape to volleyball to lounge chair to car to house top building to holy crap).

As it rams through the upper atmosphere the pressure heats the air in front of hit and compress the meteoroid itself. That can crumble it, and then each piece rams the air, and you get a cascade effect which slows it extremely rapidly, dumping all its kinetic energy of motion in a second or two, converting it to light and heat. And sound: You get a sonic boom, and there are reports this one was heard by lots of folks.

This was far, far smaller than the Chelyabinsk asteroid, which was 19 meters across and exploded with half a megaton of energy. Still, pretty exciting. I’d love to see something like this myself! It’s possible some pieces survived to hit the ground and become meteorites; I hope some are found. Meteorites from a known fall are valuable scientifically, and we can learn more about all the space stuff hitting us that way.

Blog Jam

What I’ve recently written on the blog, ICYMI

[A small rock I currently orbiting the Earth — a minimoon — and this is its trajectory. From Thursday’s article. Credit: Tony Dunn / Orbit Simulator ]

Monday 24 February, 2020: No supernova for you: Betelgeuse is brightening again right on schedule

Tuesday 25 February, 2020: Space potatoes and rubber duckies: Shattered asteroids reassemble into weird shapes

Wednesday 26 February, 2020: Does our galaxy's huge black hole have a little black hole buddy?

Thursday 27 February, 2020: The Earth has a new minimoon! But not for long…

Friday 28 February, 2020: Why do we have leap days?

Et alia

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