An asteroid estimated to be 470 metres wide will pass close to Earth on Halloween weekend, giving scientists an excellent opportunity for study but not quite coming close enough to be seen with the naked eye.

Asteroid 2015 TB145 was discovered on October 10, 2015, by a Hawaiian telescope that is part of NASA's Near-Earth Object Observation (NEOO) Program.

NEOO is a project to identify and track all near-Earth objects (NEOs) closer than 30 million miles, or about 48 million kilometres.

"If the size is correct, the new found asteroid is 28 times bigger than the Chelyabinsk meteor that penetrated the atmosphere over Russia in February 2013," astronomy website Earth and Sky said.

The asteroid will pass closer to the Moon than to Earth over October 31 and November 1.

"The trajectory of 2015 TB145 is well understood," NASA's Paul Chodas said in a statement.

"At the point of closest approach, it will be no closer than about 480,000 kilometres, or 1.3 lunar distances," or 1.3 times the average distance between the Earth and Moon.

Mr Chodas, manager of the NEO program at NASA's Jet Propulsion Laboratory in California, said although this was close by astronomical standards, a small telescope would be needed to view the visitor.

The approach can also be viewed online at the Virtual Telescope Project website.

This will be the closest approach by a large object until 2027, when the 800-metre asteroid 1999 AN10 comes within 1 lunar distance of the Earth.

Asteroid 2015 TB14 has a highly unusual oblong orbit that is tilted relative to the Earth's orbit.

Most asteroids stay close to the same plane as the Earth, explains astronomy blogger and former NASA employee Phil Plait on his blog Bad Astronomy.

"It will come at us from the south, cross Earth's orbit, then move up to the north for a while, and then back down again.

"This unusual orbit is why it was only discovered on October 10."

Mr Plait, who worked on the Hubble Space Telescope, added the Southern Hemisphere had relatively few telescopes searching for NEOs, making a late discovery more likely.

Lance Benner, who heads NASA's asteroid radar research program, said the asteroid's orbit and its high velocity of about 126,000 kilometres per hour suggested it might be some type of comet.

The gravitational influence of the asteroid is so small it will have no detectable effect on the Moon or on Earth, NASA said.

The closest approach will be on Sunday morning, November 1, at about 4:00am AEDT.

ABC/AFP