While I was camping in central Texas last weekend, a bright fireball meteor streaked across the evening sky and exploded into several smaller fireballs before fizzling out. It was truly spectacular, the most impressive single meteor I’ve witnessed, and I was lucky to be looking at a dark patch of sky at that very instant. But it left me with questions, as I realized I knew very little about where meteors originate and why they behave as they do. This might be a divergence from the usual meteorology – which focuses on hydrometeors, we’re more interested in fiery space rocks for today’s post – but I learned enough in my deep dive that I wanted to drop a few nuggets here on this forum.
Fireball meteors generally come from a specific region of the asteroid belt that experiences a resonance with Jupiter’s gravity that scatters asteroid debris through the rest of the belt and beyond into the solar system. In fact, about a third of all meteorites found on Earth originated from the same asteroid, Hebe, presumably broken off in an asteroid collision thousands of years ago. The fireball I saw traversed the ecliptic, tracing the sky between Jupiter and Venus, which makes sense as a meteoroid from the asteroid belt would likely need to stay in the plane of the solar system to impact Earth. Depending on semantics, this meteor qualifies as a rare bolide under some definitions, namely that the meteor was brighter than Venus and detonated under the pressure of the atmosphere. At least 3 smaller meteors were visible after the explosion, which was followed by a faint echoic pop, like a cosmic firework. I reported the event to the American Meteor Society, who collects anecdotal data for verification and record-keeping. It was pretty cool to see that my sighting was corroborated by a guy over 100 miles away in San Antonio, and maybe others will add details to the report!
Most of my fireball sightings have occurred outside of a designated ‘meteor shower’. That’s because meteor showers happen by a different mechanism: Earth passes through comet trails of ice and dust periodically along its orbit, hence why the position and peak intensity times are on a predictable annual schedule. Some showers can persist for decades or even centuries before debris trails dissipate – the Perseid meteor shower was documented by the ancient Chinese over 2,000 years ago, consistent due to the regular passage of the Swift-Tuttle comet every ~133 years. These meteor showers are more visible in the early morning hours, as this is when you look up into the direction of Earth’s travel. While the streaks of comet dust hitting Earth’s atmospheric windshield are still a sight to behold, fireballs are only marginally more likely to become visible meteors in the predawn hours since meteoroids travel at several times Earth’s orbital velocity.
There’s quite an interest in studying large meteors, not just for their stellar beauty but also for the existential risk posed to humanity. Surprisingly, there have been no documented deaths from a direct meteor strike, though a number of close calls have occurred over the years. Memorably, a house-sized meteor fell over a densely populated area near Chelyabinsk, Russia in 2013, creating a shockwave that injured 1500 people. Just this month, a 2.8 pound meteorite crashed into a lady’s bedroom in British Columbia. Although the impacts of comparatively small meteorites are random and immitigable, NASA and other space/defense agencies worldwide are diligently working on technologies to intercept the next ‘big one,’ which historically happen over a period of about 250 years. Meanwhile, I will continue watching the skies, hoping that another impressive fireball might pass overhead.