So, this is kinda cool. A SpaceX launch back in August 2017 apparently created a shockwave four times the size of California, which is unusually large.

The Falcon 9 rocket lifted off on August 24 with Taiwan’s FORMOSAT-5 Earth-observing satellite on board. Carrying just that satellite, weighing 475 kilograms (1,050 pounds), the rocket wasn’t that heavy. So it traveled nearly vertical.

Normally rockets launch at an angle, and when they pass the speed of sound they produce a V-shaped shockwave. But as this one was going almost straight up, the shockwave was circular.

Researchers from the National Cheng Kung University in Taiwan published a study on the unusual launch in the journal Space Weather. They said it was the largest circular shockwave they’d seen.

“We’ve seen many cases of a rocket-produced disturbance, but there’s never been something that perfectly circular and with that large area,” lead author Charles Lin said in a statement.

The launch took place from the Vandenberg Air Force Base in California, and it included a landing of the rocket’s booster. This was SpaceX’s 40th launch; they recently celebrated their 50th.

This launch was particularly unique as FORMOSAT-5 traveled alone. It had originally been intended to travel with other satellites, but after a SpaceX rocket exploded in September 2016, rescheduling meant it was by itself.

Rockets are usually launched at a bit of an angle, placing satellites about 200 kilometers (125 miles) above Earth. From here, the satellite operators can then move their satellite into its desired orbit. This time around, however, it was launched straight to its intended orbit of 720 kilometers (450 miles) high.

In their study, the researchers found that the momentum from a vertical launch had a greater effect on the ionosphere – extended from 60 to 1,000 kilometers (37 to 620 miles) – than a regular launch. This resulted in more atmospheric disturbance, causing a bigger shockwave.

They also found that the launch punched a hole in the ionosphere, with water from the rocket’s exhaust reacting with charged particles. This lasted for up to two hours, and may have caused GPS data – which has to travel through the ionosphere – to be inaccurate by up to 1 meter (3 feet).

“Understanding how the rocket launches affect our upper atmosphere and space environment is important as these anthropogenic space weather events are expected to increase at an enormous rate in the near future,” the authors noted in their paper.