2 ‘potentially hazardous’ asteroids will streak by Earth this week, one as big as a mountain. You can watch it live.

Neither of these asteroids will be visible to the naked eye, but you may be able to spot them with a telescope or binoculars, Gianluca Masi, astrophysicist and founder of The Virtual Telescope Project, told Business Insider over email.

Or, you can watch them via livestreams hosted by The Virtual Telescope Project:

• Use this link to watch Asteroid (415029) 2011 UL21 streak past Earth on Thursday, June 27, starting at 4:00 p.m. ET.
• And this link to watch Asteroid 2024 MK fly by on Saturday, June 29, starting at 5:00 p.m. ET.

Mountain-sized Asteroid (415029) 2011 UL21

Asteroid (415029) 2011 UL21 is one of the largest asteroids to have recently passed near Earth, Masi wrote in a press statement.

With an estimated diameter of roughly 1.4 miles, this mountain-sized space rock is larger than 99% of all known near-Earth objects, according to the European Space Agency.

Asteroid 2011 UL21 falls into a class of space rocks known as “planet killers,” which are at least 1.2 miles wide. If one crashed into Earth, it would cause damage on a continental scale, and potentially kick up enough dust to trigger significant climactic changes for many years, LiveScience reported.

The Chicxulub asteroid, for example, credited with the dinosaurs’ demise was about 6.5 miles across and triggered global warming for an estimated 100,000 years after impact.

Luckily, 2011 UL21 won’t be coming close enough to cause any concern on Thursday. It’ll sneak by Earth at a safe distance of more than 4 million miles, which is 17 times farther than the distance between Earth and the moon, Masi wrote.

But this fly-by is noteworthy because 2011 UL21 will be among the top 10 largest asteroids to pass by Earth at close range in the last 125 years, he added.

Newly discovered Asteroid 2024 MK

Asteroid 2024 MK was first discovered earlier this month, just 13 days before it will pass by Earth at remarkably close range, according to the European Space Agency.

It’s much smaller than 2011 UL21, with an estimated diameter between 390 and 885 feet. That’s roughly the length of one to 2.5 football fields.

But what this asteroid lacks in size, it should make up for in brightness. It will come within 184,000 miles of Earth, which is about 77% of the average distance between the Earth and the moon, Masi wrote.

It’s close proximity will make it one of the brightest objects of its kind observed in recent history, he added.