The Subaru Telescope in Hawai'i captured a strange “flying whirlpool” whizzing across the night sky at the weekend. Anyone looking up would have been very curious at its cause, before probably shrugging and moving on because it's 2022, and if this was the year aliens got in contact, frankly, no one would be surprised.
Spied hours after SpaceX’s Falcon 9 rocket launched a classified US spy satellite, it’s thought the luminous night spiral was caused by the upper stage of the rocket after being deorbited over the Pacific Ocean before burning up in Earth's atmosphere.
There are three stages to a rocket. The first stage, also known as a booster, is the first engine to engage, providing the initial thrust that launches the whole thing upward. The second, or upper stage, is the next engine to engage, propelling the rocket's cargo further than the booster can alone to continue the payload on its trajectory. The third is the payload itself – which may be a satellite, a spacecraft carrying humans, or pretty much anything being launched into space.
SpaceX launched its secret payload for the US National Reconnaissance Office (NRO) on Sunday, April 17, from the Vandenberg Space Force Base in California. The "night spiral" as Spaceweather.com dubbed it, was spotted a few hours later.
Now that SpaceX has nailed reusable rockets, the first stage of Falcon 9 is designed to return to Earth, landing neatly atop a drone ship in the Pacific, as SpaceX demonstrated in this video. In fact, this marked SpaceX's 114th successful recovery of a first-stage booster.
The upper stage of the Falcon 9 is not reusable, and so after its job is done it is deorbited – one last engine thrust to get it out of Earth's orbit – so it can fall back naturally to Earth and burn up in the atmosphere. Before it does that, there is one last fuel burn vent to get rid of any unused fuel.
The video the Subaru-Asahi Star Camera caught "shows the characteristic spiral caused by the post-deorbit-burn fuel vent of the Falcon 9 upper stage, which was deorbited over the Pacific just after the end of the 1st revolution," satellite tracker Dr Marco Langbroek told SpaceWeather.com.
The "Subaru-Asahi Star Camera" is a live stream of the night sky project in collaboration with the Asahi-Shimbun newspaper in Japan and the Subaru Telescope run but the National Astronomical Observatory of Japan. Based about 4,000 meters (13,123 feet) above sea level on the dormant volcano Maunakea on the island of Hawaiʻi, the telescope is an 8.2-meter optical-infrared telescope.
The "star camera" runs 24/7, so if you ever find yourself needing some peace and quiet, or fancy a sunrise or sunset from somewhere else in the world, you can pop by the live stream and see what the sky is doing in Hawai'i.
Or if this is the year aliens reach out, Hawai'i is as nice a spot as any to visit and you could watch them arrive.