Massive ‘Planet Killer’ Asteroid Will Pass By Earth This Week

By: Sam Watanuki | Published: Jun 25, 2024

A massive asteroid known as 2011 UL21 will make a close approach to Earth this week, traveling at around 58,000 mph.

This “planet killer” asteroid is one of the largest to pass by our planet in over a century, offering a rare opportunity for observation.

What is 2011 UL21?

2011 UL21 is a near-Earth asteroid with an orbit that occasionally brings it within 1.3 astronomical units of the sun.

Earth and asteroid in space

Source: NASA/Newsmakers; NASA/Apollo 17 crew/Wikipedia

With a diameter between 1.1 and 2.4 miles, it ranks larger than 99% of known near-Earth asteroids

Historical Comparison

While 2011 UL21 is much smaller than the Vredefort asteroid and the one that wiped out the dinosaurs, it still poses a significant threat.

Illustration of an asteroid hitting the earth and killing the dinosaurs

Source: Adobe Stock

An impact could cause continental-scale damage and trigger significant climatic changes, earning it the nightmarish title of “planet killer.”

Close Encounter Details

On June 27, 2011 UL21 will pass by Earth at a distance of 4.1 million miles, closer than it’s been in at least 110 years.

A photograph of a large telescope

Source: Freepik

Although this distance is 17 times the gap between Earth and the moon, it is still classified as potentially hazardous by NASA.

Safe Distance

Despite being classified as a “planet killer,” 2011 UL21 poses no imminent threat to Earth.

Photograph of a large asteroid floating through space

Source: Wikimedia

NASA’s Jet Propulsion Laboratory confirms that there is no danger of impact now or in the foreseeable future, allowing for safe observation.

Watch the Live Stream

You can watch the asteroid’s closest approach via a free livestream from the Virtual Telescope Project.

Man in White Dress Shirt

Source: Andrea Piacquadio/Pexels

The stream, broadcasting from Italy’s Bellatrix Astronomical Observatory, starts at 4 p.m. ET on June 27, with the closest approach expected 15 minutes later.


Spotting 2011 UL21 in the Night Sky

For those with a telescope, the asteroid will be visible from the Northern Hemisphere on June 28 and June 29.

A photograph taken of the stars at night with a tree off to the side

Source: Wikimedia

When it’s at its peak brightness, 2011 UL21 will shine as brightly as Proxima Centauri, the closest known star to our sun.


Future Approaches

2011 UL21 won’t come this close to Earth again until 2089, when it will pass within 1.7 million miles.

An artist's rendition of an asteroid flying through space

Source: Wikimedia

This future encounter will be over two and a half times closer than its current approach, based on JPL simulations.


Asteroid Monitoring

Continuous monitoring and studying of near-Earth objects like 2011 UL21 are crucial.

An image of several scientists working on data in their office

Source: Wikimedia

These efforts help scientists understand their trajectories and potential impacts better, ensuring the safety and preparedness of our planet.


The Threat of Smaller Asteroids

While there is no known threat from any planet-killer asteroids for at least the next 1,000 years, smaller asteroids will have close encounters.

Illustration of an asteroid heading toward planet earth

Source: iStock

For example, the asteroid Apophis will pass closer to Earth than some satellites in 2029, highlighting the need for ongoing vigilance.


Importance of Astronomical Observations

Observing events like the approach of 2011 UL21 provides valuable data for astronomers.

n Palomar Mountain in California lies the Hale Telescope, that has been in use for 60 years. Now added to the telescope is a optics laser that shoots 56 miles upward to help Hale produce sharper and detailed views of galaxies and quasars.

Source: Joe McNally/Getty Images

This data helps refine our understanding of asteroid orbits and improve prediction models, which are essential for planetary defense strategies.


Public Engagement in Astronomy

Events like the close approach of 2011 UL21 also engage the public in astronomy.

Four people standing on a hilltop looking at the Milky Way galaxy in the night sky

Source: Kendall Hoopes/Pexels

By offering livestreams and encouraging amateur observations, these events help foster a greater interest in space and science among people of all ages.