Sydney Morning Herald
Tue, 21 Jul 2009 10:49 UTC
Anthony Wesley, 44, a computer programmer from Murrumbateman, a village north of Canberra, made the discovery about 1am yesterday using his backyard 14.5-inch reflecting telescope.
The impact would have occurred no more than two days earlier and will only be visible for another few days.
Within hours, his images had spread across the internet on science websites.
NASA's Jet Propulsion Laboratory confirmed the discovery at 9pm yesterday using its large infrared telescope at the summit of Mauna Kea in Hawaii.
The only other time astronomers have discovered evidence of a space object having hit Jupiter was when the Shoemaker-Levy 9 comet collided with the giant planet in July, 1994.
That event was also the first direct observation of two objects colliding in space.
Glenn Orton, the NASA scientist who confirmed Wesley's discovery, said: "We are extremely lucky to be seeing Jupiter at exactly the right time, the right hour, the right side of Jupiter to witness the event. We couldn't have planned it better."
Orton said he was not yet sure whether the object that hit Jupiter was a comet, asteroid or some other piece of space junk. But the impact mark is about the size of the Earth.
"It's been a whirlwind of a day and this, on the anniversary of the Shoemaker-Levy 9 and Apollo anniversaries, is amazing," he said.
To most people the image is unremarkable and appears as little more than a scar on Jupiter's vast gas surface.
Leigh Fletcher, an astronomer who worked with Orton on confirming the discovery last night, said: "These are the most exciting observations I've seen in my five years of observing the outer planets."
Wesley said in a phone interview that documenting these sorts of impacts was the only way to get new data on how the solar system formed and what planets such as Jupiter are made of, as the impact throws up debris that would otherwise be invisible when looking through a telescope from Earth.
The collision also allows astronomers to examine Jupiter's role in cleaning up space debris in the solar system.
"If anything like that had hit the Earth it would have been curtains for us, so we can feel very happy that Jupiter is doing its vacuum-cleaner job and hoovering up all these large pieces before they come for us," he said.
"An impact event like this, even just knowing how often they happen, gives you some idea of how much debris is left over from the solar system when it formed and how quickly Jupiter is vacuuming up the remains of the bits and pieces floating around in the solar system."
Mike Salway, who runs the Australian amateur astronomy community website iceinspace.com.au, said astronomers around the world were raving about the discovery.
"Amateur astronomers are all over it at the moment - they all had their telescopes out last night looking for it," he said.
Wesley, who has been keen on astronomy since he was a child, said telescopes and other astronomy equipment were so inexpensive now that the hobby had become a viable pastime for just about anybody. His own equipment cost about $10,000.
In many cases, particularly with planets such as Jupiter, professional space watchers were turning to amateurs to provide them with new discoveries.
"A lot of the professional astronomers have access to large scopes but those scopes are in demand for all sorts of other jobs and you just can't afford to tie up a large telescope worth millions of dollars looking at Jupiter every night," Wesley said.
"These large telescopes only get built because of the interests of the consortium parties, and those interests need to be attended to, so it's really left to amateurs who've got no fixed agenda to image whatever they find interesting."