NASA's Deep Space Network closely tracks an Empire State Building-sized asteroid

Scientists at NASA's Jet Propulsion Laboratory in Southern California closely tracked an asteroid - called 2011 AG5 - to determine its size, shape and other details. Discovered in 2011, the asteroid -roughly the size of the Empire State Building - is one of the most elongated asteroids to date.

Asteroid 2011 AG5 safely flew past Earth at a distance of about 1.8 million kilometres (a little under five times the distance between the Moon and Earth) on February 3. The above collage shows six planetary radar observations of the asteroid a day after it made a close approach to our planet.

This close approach provided scientists with the first opportunity to take a detailed look at the asteroid, revealing that its dimensions are similar to those of the Empire State Building - about 1,600 feet (500 meters) long and about 500 feet (150 meters) wide.

The team used the powerful Goldstone Solar System Radar antenna dish at NASA's Deep Space Network facility near Barstow, California, to track this extremely elongated asteroid. The observations took place from Jan. 29 to Feb. 4.

Apart from the dimensions, revealed other details about the object. Asteroid 2011 AG5 takes nine hours to fully rotate and features subtle dark and lighter regions that may indicate small-scale surface features a few dozen meters across.

The Goldstone radar observations also reveal that the asteroid orbits the Sun once every 621 days and won't have a very close encounter with Earth until 2040 when it will pass safely at a distance of about 670,000 miles - that's nearly three times the distance between the Earth and the Moon.

According to NASA-JPL, the use of radar allows for accurate distance measurements, which can assist scientists at NASA's Center for Near Earth Object Studies (CNEOS) in improving the asteroid's orbital path.

"Interestingly, shortly after its discovery, 2011 AG5 became a poster-child asteroid when our analysis showed it had a small chance of a future impact. Continued observations of this object ruled out any chance of impact, and these new ranging measurements by the planetary radar team will further refine exactly where it will be far into the future," Paul Chodas, the director for CNEOS at JPL, said in a statement.

An asteroid roughly the size of the Empire State Building! Scientists recently tracked one of the most elongated objects ever imaged by planetary radar and revealed its unique dimensions: 1,600 ft (500 meters) long and about 500 ft (150 meters) wide. https://t.co/DqhBSNTtzi pic.twitter.com/9x9gM7Qgpq

— NASA JPL (@NASAJPL) February 17, 2023