There's a Radar Record of the Bay's May Fireball

CAPE COD BAY · A DAYLIGHT FIREBALL

Five months after the boom, researchers have a radar-backed reconstruction. It's more complicated than one altitude.

3 min read · A Celebrate Lower Cape spotlight

If you heard the boom on May 30, you heard it in daylight. It was about 2:06 on a Saturday afternoon when a fireball crossed the sky over eastern Massachusetts, loud enough to carry across parts of New England. NOAA's GOES-19 satellite caught its light.

That wasn't the end of the evidence. An international team including MIT's Haystack Observatory has reconstructed the event from several independent kinds of measurement.

More than one kind of radar

The team's SIMONe meteor radar picked up radio reflections from the plasma around the incoming body and its trail. Weather radars then caught signals consistent with solid fragments falling after the breakup. Infrasound instruments measured the shock in the air. The team also used optical records, including the satellite data and ground-based video.

Each one sees a different part of the same few seconds. A radar echo from a meteor trail is not the same as a rock in somebody's hand.

31 miles, or 21? It depends which page you read

MIT's Nov. 9 summary describes breakup at about 31 miles up. The team's public research paper, first posted Oct. 17, puts the end of the meteor-radar plasma trail at 33.61 kilometers, about 21 miles. The same paper gives 32 kilometers, about 20 miles, for the moment of peak brightness recorded by NASA's fireball center.

Back in May, NASA told news outlets the object broke apart near 40 miles. Those numbers measure different things at different stages of the analysis, and nobody has published one figure that reconciles them. The safest way to say it: the fireball came apart high over the region, and the radar followed its trail down to about 21 miles.

The paper was out before the announcement

MIT's announcement came Nov. 9, but the preprint had been public since Oct. 17, and Cape and Islands public radio interviewed Haystack Director Phil Erickson on Nov. 5.

The paper has been submitted to The Astronomical Journal. As of those November announcements, the journal hadn't finished vetting it, so for now it's a public draft, not a final published paper.

What might be on the bottom of the bay

The weather radar and flight modeling point to a likely area in Cape Cod Bay where fragments came down. None of the published work reports a piece being found.

In the Nov. 5 interview, Erickson said Woods Hole colleagues might try to look for fragments. That's a maybe, not a search under way.

The boom you heard that afternoon now has a trail of radar echoes, satellite light and pressure waves behind it. If any pieces made it down, they're still out there.

Send it to: whoever swears they heard the boom in May.