ANU astronomers are investigating four unknown objects uncovered by a online public hunt to discover the ninth planet in our solar system.

About 60,000 people from around the world have logged on, searched, and classified close to 5 million objects in space since the site was launched on Tuesday March 28 timed with the BBC Stargazing Live broadcast.

ANU astronomer and astrophysicist Dr Brad Tucker the incredible public participation in the project had helped to rule out areas in the southern sky where Planet 9 could be situated.

"With the help of tens of thousands of dedicated volunteers sifting through hundreds of thousands of images taken by SkyMapper, we have achieved four years of scientific analysis in under three days," he said. 

"We've managed to rule out a planet about the size of Neptune being in about 90 per cent of the southern sky out to a depth of about 350 times the distance the Earth is from the Sun." 

Dr Tucker said the project had uncovered many known objects such as two minor planets, Chiron and Comacina, but plenty of unknown objects too.

The team at the ANU Siding Spring Observatory has isolated some of the most interesting and is busy  confirming whether or not they are Planet 9, dwarf planets or asteroids by using telescopes at the facility or others from around the world.

"Whatever they are they are interesting. They are objects that require further investigation," Dr Tucker said.

"We know they are previously undiscovered. I hope one is a dwarf planet, or what we call a trans-neutonian object, that would be really nice. They are all consistent with that but without more observation we just don't know." 

Tracking down these new objects requires cooperation and a good deal of tracking to get a clearer picture of what they are.

"We are using SkyMapper to find them again," he said. "Once we find them again we can look back previously tp where we saw them before and with those points calculate the orbit, path, rate and know a lot more." 

The overwhelming response to the public call to search had been "absurd, in a good way" Dr Tucker said. 

"I thought we had enough data to take weeks or months to get through but people got through it in a few days," he said.

"The fact that we have been able to accomplish this really fast, means we will have an answer, no matter what that is, years quicker than we thought which is so exciting." 

To view the ANU's SkyMapper telescope images, visit www.planet9search.org.