The phenomenon occurred during SpaceX’s latest mission, dubbed Starlink 15-9, which launched at 11:36 PM ET (8:36 PM PT) from Vandenberg Space Force Station in California. Just minutes into the flight, the rocket’s exhaust interacted with Earth’s atmosphere, creating a stunning visual effect known as the “jellyfish phenomenon.” This occurs when the rocket’s exhaust, primarily water vapor, encounters the cold, dense air of the upper atmosphere. The rapid expansion of the exhaust causes the water vapor to condense into a visible cloud, forming a balloon-like shape around the rocket. The high speed of the Falcon 9 also generates shock waves, sculpting the exhaust into the distinctive jellyfish-like pattern.

What made Monday’s display particularly breathtaking was its timing. The launch took place shortly after sunset, allowing the sun’s rays to illuminate the crystallized exhaust plume. This created a glowing, otherworldly spectacle visible across Southern California, from Riverside—over 200 miles southeast of Vandenberg—to Los Angeles County’s South Bay. Cameron Gable, SpaceX’s lead avionics systems engineer, captured the jellyfish effect as it soared over the South Bay, sharing the striking images on X.

The Starlink 15-9 mission was part of SpaceX’s ambitious effort to expand its Starlink constellation, a network of satellites designed to provide global internet coverage. The Falcon 9, a reusable rocket, successfully deployed its latest batch of satellites into low Earth orbit. In a hallmark of SpaceX’s cost-saving design, the rocket’s first-stage engine made a perfect landing on a droneship in the Pacific Ocean about eight minutes after launch. This marked the 463rd successful recovery of a SpaceX engine and the 200th launch from Vandenberg’s Space Launch Complex 4 East.

While the jellyfish effect may have seemed like a UFO to the untrained eye, it’s a well-documented occurrence during rocket launches. Often referred to as a “vapor cone” or “shock collar,” it forms when the localized air pressure around the rocket drops, causing the air temperature to plummet and water vapor to condense into visible clouds. The phenomenon is especially dramatic when launches occur around dawn or dusk, as the sunlight enhances the visibility of the exhaust plume. In fact, this wasn’t the first time a SpaceX rocket produced such a display. In October 2022, a similar Falcon 9 launch created a jellyfish-like trail during another Starlink mission, captivating skywatchers across the region.

The jellyfish effect isn’t unique to SpaceX, either. Any rocket launch worldwide can produce this striking visual under the right conditions. For instance, in June 2024, an X user in Phoenix, Arizona, spotted a similar phenomenon during a Falcon 9 launch from Vandenberg, over 500 miles away. The ability to see these displays from hundreds of miles away highlights the scale and power of modern rocketry.

SpaceX’s frequent launches—75 in 2025 alone, mostly for Starlink missions—mean the jellyfish phenomenon is becoming a familiar sight for those living near launch sites. The company’s reusable rocket technology, combined with carefully timed launches, ensures that these displays remain a regular occurrence. Monday’s mission, broadcast live by SpaceX, showcased not only the jellyfish effect but also the precision of the rocket’s reusable engine landing, a testament to the company’s innovative approach to space exploration.

For Californians who witnessed the glowing “jellyfish UFO” on Monday night, the sight was a reminder of humanity’s reach into the cosmos. What initially appeared to be an alien mystery was, in fact, a stunning byproduct of cutting-edge technology. As SpaceX continues to expand its Starlink network and push the boundaries of spaceflight, skywatchers can expect more of these awe-inspiring displays, each one a dazzling blend of science, engineering, and natural beauty.