If you ever see a red spherical flash in the night sky, it’s most likely coming from a Falcon 9 rocket. This phenomenon has become so common that astronomers have given it a pet name: “SpaceX auroras.”
They are not auroras. The bright “SpaceX aurora” you see above was photographed on November 3 of last year from the McDonald Observatory, west of Texas. Despite its name, it is not an aurora, but rather a perforation in the ionosphere caused by the re-entry of a rocket. Yes, a SpaceX rocket.
The author of the photo, Stephen Hummel, told the creator of Spaceweather.com that they were seeing “two to five every month” due to the unusual frequency of SpaceX launches.
Holes in the ionosphere. SpaceX launches have long been known to open holes in Earth’s atmosphere. Not at takeoff, but at reentry: when the second stage of the Falcon 9 rocket restarts its engine to leave orbit and disintegrate in the Earth’s atmosphere.
The phenomenon occurs at about 300 km altitude in the ionosphere, the layer of ionized gas that surrounds our planet. 90 minutes after a launch, the Falcon 9’s second stage restarts its engine to deorbit and produces a temporary hole that glows red.
Visible with the naked eye. The hole is actually a chemical alteration of the ionosphere. The rocket exhaust, loaded with water vapor, reduces local ionization by up to 70%, a disturbance that becomes visible by emitting a fluorescent red glow.
Although the Falcon 9 turns on its engine for just two seconds (just enough to propel it towards the ocean), its restart releases around 200 kg of water and carbon dioxide, which can produce a very intense glow visible to the naked eye. . “SpaceX auroras” last up to 10 minutes, according to Spaceweather.
They do not pose a threat. It is known that space launches can trigger these types of effects in the atmosphere since 2005when a Titan rocket caused “serious disturbances in the ionosphere.” However, the ionospheric holes close after a few minutes as the recombined gases re-ionize, so they pose no threat.
Why the name SpaceX. If the phenomenon is common to different rockets, why is it known by the name SpaceX? The nickname “SpaceX aurora” is not an astronomical term, but is due to the frequency of launches of the Falcon 9, which has made these brightnesses a much more common phenomenon. SpaceX surpassed 90 launches last year, putting 80% of the mass sent into space into orbit by 2023.
Most of them are Starlink satellite launches. SpaceX has more than 5,500 Starlinks in operation and hopes to reach 12,000 in the coming years.
Image | Stephen Hummel
In techopiniones | In 2022, an “ownerless” rocket crashed on the Moon. Everyone thought it was from Elon Musk, but a study confirmed its true origin
In techopiniones | Leaving California is just the first step: SpaceX has started the process to create an independent city in Texas
*An earlier version of this article was published in December 2023