Arecibo Radar Returns with Asteroid Phaethon Images

This is close enough for 2017 YZ4 to be classified as a "near-Earth object" - described by Nasa as a body that has been "nudged by the gravitational attraction of nearby planets into orbits that allow them to enter the Earth's neighbourhood". Arecibo's radar images of Phaethon have resolutions as fine as about 250 feet (75 meters) per pixel.

This year Nasa discovered almost 2,000 new near-Earth asteroids, but they estimate the locations of only around 3 per cent of the total number are known.

The images of 3200 Phaethon show that it also has "a large concavity, or depression, at least several hundred meters in extent near its equator, and a conspicuous dark, circular feature near one of the poles", according to the statement.

The space rock - which will be travelling at 21,363 miles per hour when it makes its closest approach to earth at 4.56pm on December 28 - measures between seven and 15 metres (22.6 to 49 feet) in diameter. High frequency radio signals from Earth did not return from the mysterious dark zone, suggesting it could be a crater.

Analysis of the space rock reveals it is about 1 kilometer bigger than previous estimates. Most asteroids are found orbiting in the Asteroid Belt, a series of rings located between the orbits of Mars and Jupiter.

Asteroids and comets are differentiated based on what they are mad of. "We have been working diligently to get it back up and running since Hurricane Maria devastated Puerto Rico".

The Arecibo Observatory is only just coming back online after the devastating impact Hurricane Maria had on Puerto Rico and its people, the strongest hurricane to hit the island in nearly a century.

These new readings were made possible as 3200 Phaethon passed by Earth in December, getting as near as 10.3 million kilometres (6.4 million miles) this time around.

The new observations conducted from December 15-19 show Phaethon to be about 3.6 miles (six kilometres) wide. The encounter is the closest the asteroid will come to Earth until 2093, but it came a little closer in 1974 and about half this distance back in 1931 before its existence was known. The Arecibo Observatory is a facility of the National Science Foundation operated under cooperative agreement by SRI International, USRA, and Universidad Metropolitana. Arecibo has the most powerful radar system on Earth and is used by NASA's Planetary Defense Coordination Office to monitor "potentially hazardous asteroids", or PHAs.