Don’t look up: NASA is about to smash a probe into an asteroid and you can watch

Illustration of DART on course to impact Dimorphos (NASA/Johns Hopkins APL)
Illustration of DART on course to impact Dimorphos (NASA/Johns Hopkins APL)

It sounds like the plot of a Hollywood blockbuster but it’s true. NASA is about to crash a £300,000 probe into an asteroid at 14,000mph tonight (September 26).

You can see all this celestial action play out for yourself via live images sent from the doomed probe back to Earth.

The Double Asteroid Redirection Test (DART) aims to check our planetary defences against potential asteroid strikes and it is the first NASA mission of its kind.

The results will be pretty spectacular, says Nancy Chabot, DART co-ordination lead at the John Hopkins University Applied Research Laboratory, who advises everyone to tune in.

Here’s how to watch the mission, along with the answers to some other burning questions.

Why is NASA crashing a probe into an asteroid?

The party ended for the dinosaurs when scientists believe an asteroid ended life on Earth 66 million years ago. There’s been little reason to fear a sequel on that level but this mission will help us to prepare for any smaller asteroids that could, say, hit a city - with devastating consequences.

NASA believes that by firing a probe into an asteroid, it’s possible to adjust its flight path so this object would miss Earth, provided the collision happens far enough in advance.

In November 2021, NASA sent the DART probe into the cosmos to test if this idea works.

Illustration of DART, from behind the NEXT–C ion engine (NASA/Johns Hopkins APL)
Illustration of DART, from behind the NEXT–C ion engine (NASA/Johns Hopkins APL)

Which asteroid is NASA aiming for?

The target for DART is Dimorphos, which is actually a small moon that orbits a larger asteroid called Didymos. Both objects are located around seven million miles from Earth.

Dimorphos itself is 160 metres in diameter, which is roughly half the height of the Eiffel Tower (321m), whereas Didymos dwarfs both of them at a whopping 780m across.

Neither of these are exactly small but, in Space terms, they are tiny. What’s odd is that DART will only be able to distinguish between the two in the last 50 minutes of its journey.

What will happen during the NASA DART mission?

If successful, we should see Dimorphos’s 11-hour-and-55-minute orbit time reduced by 10 minutes, which will prove that its path has changed so that it runs closer to Didymos. The official results won’t come in for several months after impact.

There should be minimal damage to Dimorphos, despite being hit by the DART probe at 14,000mph. Chabot compares tonight’s event to a golf cart hitting a pyramid. “This isn’t going to blow up the asteroid,” she explains, insisting that it won’t get smashed into pieces.

Instead, the impact will give the asteroid a new crater, tens of metres in size, and push around one million kilograms’s worth of rocks and dirt into space before (hopefully) sending the asteroid along its new path. This is the plan.

Infographic showing the effect of DART’s impact on the orbit of Dimorphos (NASA/Johns Hopkins APL)
Infographic showing the effect of DART’s impact on the orbit of Dimorphos (NASA/Johns Hopkins APL)

What will you be able to see from Earth?

Most of the images will be sent from the DART probe, millions of miles away, so it will be more like a slideshow with one image every second until the final strike. Even so, it should be amazing to see, not least given that nobody has ever seen this asteroid before. At least, nobody on this planet.

Alternatively, if you want a view from Earth, smart telescope makers Unistellar have their own live stream running from Reunion Island, on the east coast of Africa — part of a narrow band of our planet where the impact will be viewable via telescope.

Is there any risk to Earth?

No, NASA says. The asteroid has been chosen to avoid any such concerns, and this won’t suddenly send it our way. “There’s no danger in this whatsoever,” Professor Colin Snodgrass, of the DART mission science team at Edinburgh University, told the Guardian. “We are only changing its orbit around the bigger asteroid, we’re not changing its orbit around the sun. It cannot come towards Earth.”

How to watch the NASA Dart mission?

NASA says impact is expected at 12.14 am on Tuesday (UK time), though the feed will start broadcasting at 10pm on Monday. The last two minutes will be the most exciting, as the asteroid looms into view, filling the screen in preparation for the climax.

You can watch the NASA Dart mission via NASA TV — the space agency’s YouTube channel.