'Planet Killer' asteroid 'the size of a mountain' to pass by Earth today

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By James Kay

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Get ready - a mountain-sized "planet killer" asteroid is set to pass by Earth today.

The colossal asteroid dubbed 2011 UL21 will come within 4.1 million miles of Earth, making it one of the largest space rocks to approach our planet in 125 years, per LiveScience.

This "planet killer" asteroid will travel at a staggering 58,000 mph (93,000 km/h) during its flyby, offering a rare opportunity for skywatchers and astronomers to witness the event.

According to SpaceReference.org, it measures between 1.1 and 2.4 miles (1.7 to 3.9 kilometers) wide, making it larger than 99% of known near-Earth asteroids, as confirmed by the European Space Agency (ESA).

GettyImages-460713851.jpgThe asteroid is set to fly past Earth today. Credit: SCIEPRO/Getty

2011 UL21 is classified as a near-Earth asteroid, meaning its orbit brings it within 1.3 astronomical units (AU) of the sun, or roughly 1.3 times the average distance between Earth and the sun. The asteroid completes an orbit around the sun every three years.

Despite being categorized as a "planet killer" due to its massive size, 2011 UL21 is still much smaller than the Chicxulub asteroid, which is believed to have caused the dinosaurs' extinction approximately 66 million years ago.

Interestingly, 2011 UL21 does not follow the usual orbital path of most NEOs. Instead, it travels at a steep angle, possibly influenced by the gravitational forces of Jupiter.


The European Space Agency (ESA) has noted that Jupiter's gravity can sometimes redirect asteroids towards Earth. 

According to simulations by NASA's Jet Propulsion Laboratory (JPL), 2011 UL21's approach will be the closest it has come to Earth in over a century.

Although its distance will be about 17 times that of the moon from Earth, it is still considered a potentially hazardous object by NASA.

Astrophysicist Gianluca Masi, director of the Virtual Telescope Project (VTP), noted in a recent statement: "It is interesting because it's probably one of the 10 biggest asteroids to pass within 4.7 million miles (7.5 million km) of our planet since 1900."

2011 UL21 will not come this close to Earth again until 2089, when it will approach within 1.7 million miles (2.7 million km) of our planet—more than two and a half times closer than this year's flyby.

GettyImages-163692539.jpgThe asteroid measures between 1.1 and 2.4 miles wide. Credit: Doug Armand/Getty

There is no threat of a planet-killer asteroid impacting Earth for at least the next 1,000 years.

However, a second asteroid, named 2024 MK, will pass much closer on Saturday. Discovered only on June 16, 2024 MK will zip by at a distance of 180,200 miles from Earth - approximately 75% of the distance to the Moon.

Though significantly smaller than 2011 UL21, measuring between 120 and 260 meters wide, 2024 MK could still cause substantial damage if it were to impact Earth.

Dr. Greg Brown, an astronomer at the Royal Greenwich Observatory, commented on the significance of these events, via the Metro: "This week, two asteroids will pass somewhat nearby to the Earth. For small asteroids, this is a very common occurrence, with close passes dozens of times a month. However, these two asteroids are somewhat larger than we normally expect."

GettyImages-460713859.jpgThere is no chance of the asteroid hitting Earth. Credit: SCIEPRO/Getty

Dr. Brown highlighted the importance of asteroid 2024 MK's recent discovery: "While neither asteroid poses a threat to Earth, 2024 MK was discovered less than two weeks before its projected close approach.

"It is also thought to be considerably larger than the asteroid that caused the Tunguska event, which caused devastation across a 2,000 square kilometer region of — thankfully uninhabited — Siberian countryside in 1908."

For those eager to witness the 2011 UL21, the VTP will host a free live stream from the Bellatrix Astronomical Observatory in Ceccano, Italy.

The stream begins at 4:00PM ET on June 27, with the closest approach expected 15 minutes later.

Additionally, the asteroid will be visible through a telescope, appearing brightest on June 28 and June 29. Viewers in the Northern Hemisphere should look for a brightness similar to Proxima Centauri, the nearest star to the sun.

Featured image credit: SCIEPRO/Getty

'Planet Killer' asteroid 'the size of a mountain' to pass by Earth today

vt-author-image

By James Kay

Article saved!Article saved!

Get ready - a mountain-sized "planet killer" asteroid is set to pass by Earth today.

The colossal asteroid dubbed 2011 UL21 will come within 4.1 million miles of Earth, making it one of the largest space rocks to approach our planet in 125 years, per LiveScience.

This "planet killer" asteroid will travel at a staggering 58,000 mph (93,000 km/h) during its flyby, offering a rare opportunity for skywatchers and astronomers to witness the event.

According to SpaceReference.org, it measures between 1.1 and 2.4 miles (1.7 to 3.9 kilometers) wide, making it larger than 99% of known near-Earth asteroids, as confirmed by the European Space Agency (ESA).

GettyImages-460713851.jpgThe asteroid is set to fly past Earth today. Credit: SCIEPRO/Getty

2011 UL21 is classified as a near-Earth asteroid, meaning its orbit brings it within 1.3 astronomical units (AU) of the sun, or roughly 1.3 times the average distance between Earth and the sun. The asteroid completes an orbit around the sun every three years.

Despite being categorized as a "planet killer" due to its massive size, 2011 UL21 is still much smaller than the Chicxulub asteroid, which is believed to have caused the dinosaurs' extinction approximately 66 million years ago.

Interestingly, 2011 UL21 does not follow the usual orbital path of most NEOs. Instead, it travels at a steep angle, possibly influenced by the gravitational forces of Jupiter.


The European Space Agency (ESA) has noted that Jupiter's gravity can sometimes redirect asteroids towards Earth. 

According to simulations by NASA's Jet Propulsion Laboratory (JPL), 2011 UL21's approach will be the closest it has come to Earth in over a century.

Although its distance will be about 17 times that of the moon from Earth, it is still considered a potentially hazardous object by NASA.

Astrophysicist Gianluca Masi, director of the Virtual Telescope Project (VTP), noted in a recent statement: "It is interesting because it's probably one of the 10 biggest asteroids to pass within 4.7 million miles (7.5 million km) of our planet since 1900."

2011 UL21 will not come this close to Earth again until 2089, when it will approach within 1.7 million miles (2.7 million km) of our planet—more than two and a half times closer than this year's flyby.

GettyImages-163692539.jpgThe asteroid measures between 1.1 and 2.4 miles wide. Credit: Doug Armand/Getty

There is no threat of a planet-killer asteroid impacting Earth for at least the next 1,000 years.

However, a second asteroid, named 2024 MK, will pass much closer on Saturday. Discovered only on June 16, 2024 MK will zip by at a distance of 180,200 miles from Earth - approximately 75% of the distance to the Moon.

Though significantly smaller than 2011 UL21, measuring between 120 and 260 meters wide, 2024 MK could still cause substantial damage if it were to impact Earth.

Dr. Greg Brown, an astronomer at the Royal Greenwich Observatory, commented on the significance of these events, via the Metro: "This week, two asteroids will pass somewhat nearby to the Earth. For small asteroids, this is a very common occurrence, with close passes dozens of times a month. However, these two asteroids are somewhat larger than we normally expect."

GettyImages-460713859.jpgThere is no chance of the asteroid hitting Earth. Credit: SCIEPRO/Getty

Dr. Brown highlighted the importance of asteroid 2024 MK's recent discovery: "While neither asteroid poses a threat to Earth, 2024 MK was discovered less than two weeks before its projected close approach.

"It is also thought to be considerably larger than the asteroid that caused the Tunguska event, which caused devastation across a 2,000 square kilometer region of — thankfully uninhabited — Siberian countryside in 1908."

For those eager to witness the 2011 UL21, the VTP will host a free live stream from the Bellatrix Astronomical Observatory in Ceccano, Italy.

The stream begins at 4:00PM ET on June 27, with the closest approach expected 15 minutes later.

Additionally, the asteroid will be visible through a telescope, appearing brightest on June 28 and June 29. Viewers in the Northern Hemisphere should look for a brightness similar to Proxima Centauri, the nearest star to the sun.

Featured image credit: SCIEPRO/Getty