Video of the Falcon 9 rocket over Sydney, courtesy John Stevens
There was great excitement in Sydney and other places on the east coast of Australia on the morning of Saturday 5 June 2010. Early risers reported seeing a bright spiral slowly moving across the sky from west to east. People reported their sightings to media outlets, emergency services and a good number appropriately reported it on the Sydney Observatory blog Lights in the Sky page.
No one seemed to know what it was. The usual suspects mentioned in the media suggested that it was a UFO or even visitors from space. The best suggestion seemed to be that it is a stunt associated with the next day’s arrival of teenage sailor Jessica Watson on the Sunshine Coast. Even astronomers were quoted in the media with various random suggestions such that people had been looking at the planet Jupiter or that it was space junk. However, the mystery was quickly solved by Sydney Observatory astronomers Dr Andrew Jacob and Geoff Wyatt who identified the object as the newly launched Falcon 9 spacecraft on its first pass after launch. Their comments were widely reported in the Australian media.
Circumstances were perfect for the visibility of the spacecraft over eastern Australia. The craft had been launched at 4:45 am AEST from Cape Canaveral and had reached orbit within nine minutes. An hour later after travelling across a large part of the globe from west to east (the same direction that the Earth turns on its axis) it reached the east coast just before nautical twilight that occurred in Sydney at 5:55 am. The timing meant that the rocket, circling about 250 km above the ground, was illuminated by the Sun while the sky was still dark.
As explained by Andrew Jacob in a comment on the Lights in the Sky page and, in greater detail by Phil Plait on his Bad Astronomy blog, the second stage booster of the Falcon 9 rocket was spinning and as it released vapour the spin created a water-sprinkler effect.
For those who were lucky enough to see it, the Spiral in the Sky must have been an awe-inspiring sight. And for the astronomers, Andrew Jacob says that, “It made a standard Saturday quite something!”.