Imagine you’re on an island paradise, staying up very late and enjoying your view of the dark sky on a warm predawn morning. Suddenly, your reverie is interrupted by a bizarre and frankly eerie sight: Rising over the horizon is a huge circle of light, a glowing smoke ring that gets bigger as it moves silently across the starry vault. After several minutes, growing the whole time, it finally dips below the far horizon, leaving you stunned and wondering if you’ve lost your mind.

Last week, I got two emails from two different people describing just this sort of event. I knew what they were telling me was real … but not because the two reports were independent of one another and not because one of them sent me the amazing picture displayed above.

I knew it was real because I knew right away what event they were describing. I’ve heard these stories before. Once was in 2009 when such an event freaked out people all over Norway, and two have been seen in recent years over Hawaii—one in 2011 and another in 2013.

Hawaii, you say? The folks who sent me the emails were both on the Haleakala volcano on the Hawaiian island of Maui. And both saw the halo around 04:30 local time on Tuesday morning, Sept. 23.

Aha! They had just seen a suborbital missile on its way across the planet after a test launch.

That’s what was seen from the same area in 2011 and 2013. A Minuteman III ICBM was launched from Vandenberg Air Force Base in California, and while it’s in space the third stage performs a fuel dump. When the material is released, it expands as a spherical shell in the near-vacuum of space, and looks very much like an expanding, glowing soap bubble. It also moves rapidly across the sky, since it maintains the momentum of the rocket itself moving at several kilometers per second.

I looked again at the picture I was sent. If the launch was from California, people seeing it in Hawaii would see the halo approaching from the northeast. And sure enough: If you look at the picture, you can see the four stars comprising the bowl of the Big Dipper on the left side of the halo. This picture was taken facing northeast.

OK, so it was a Minuteman launch. However, I poked around and couldn’t find any launch info. As I do in situations like this, I went to my friend Jonathan McDowell, who is a space aficionado and keeps tracks of all launches. He showed me that, indeed, there was a test launch of a Minuteman III intercontinental ballistic missile from Vandenberg Air Force Base on Tuesday morning at 7:45 a.m. Pacific time—4:45 Hawaii time. Aha again!

Jonathan pointed me to an article about the launch on the Vandenberg website, too. I contacted the public affairs office there, and they told me that in fact the launch was to the southwest, so the missile would send its payload into the Pacific Ocean near Kwajalein Atoll, where there’s a military installation. Mind you, a Minuteman is designed to drop nuclear weapons on a target, so tracking the launch down to the impact is important. In this case, you may be somewhat relieved to note, the payload was a dummy for the missile test.

Case closed.

One of these days, I hope to see something like this. I’ve watched countless satellites pass overhead, and even witnessed two or three rocket launches. But to see that weird halo of light gliding silently across the sky, growing ever larger as it moves … that would be pretty amazing. Someday.