Illustration of the Hayabusa2 spacecraft making a fast close flyby of the rocky asteroid Torifune
Space
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Japan’s Space Explorer Zooms Past an Asteroid Today — Going 12,000 Miles Per Hour!

Quick Summary

Today, a Japanese spacecraft is making one of the closest asteroid flybys ever attempted. The probe, called Hayabusa2, is zooming past an asteroid named Torifune at a mind-blowing speed. Scientists are watching closely to learn about this mysterious space rock.

What Happened?

Japan’s space agency, JAXA, planned today’s flyby years in advance. At around 6:30 p.m. Japan time on July 5, the Hayabusa2 spacecraft will make its closest pass to asteroid Torifune.

How close? The plan is to get within just 1 kilometer — about 0.6 miles — of the asteroid’s surface. That’s like flying a jetliner at full speed and coming within arm’s length of a building! And Hayabusa2 will be moving at 5 kilometers per second. In miles per hour, that’s over 11,000 mph. Even the fastest jets on Earth only reach about 1,500 mph, so Hayabusa2 is traveling more than seven times faster.

Torifune is estimated to be about 450 meters wide — roughly the length of five American football fields placed end to end. But scientists don’t know its exact shape yet. It might be one solid rock. It might be a loose pile of rubble. It might even be two smaller rocks that slowly bumped into each other and stuck together long ago. The flyby will help answer these questions!

Hayabusa2 is no rookie. This probe launched back in December 2014 and visited a different asteroid called Ryugu. It actually landed on Ryugu, collected a sample of space rock, and dropped a capsule back to Earth in December 2020. That capsule contained about 5.4 grams of Ryugu material — less than a teaspoon — but it was the largest asteroid sample ever returned to Earth at the time.

After dropping off those precious samples, Hayabusa2 had fuel left over. So JAXA gave it a new mission! The probe, now nicknamed Hayabusa2# (which stands for “Sharp”), set off across deep space toward Torifune. Today’s flyby is its next big adventure. After this, it will continue its journey toward another tiny asteroid called 1998 KY26, where it is scheduled to arrive in 2031.

During today’s flyby, Hayabusa2 will use five science instruments to photograph and study Torifune. It won’t pick up a sample this time — that equipment was used up at Ryugu. But the photos and data it collects will help scientists understand what Torifune is made of and how to track asteroids that might come close to Earth in the future.

This type of mission also helps with something called planetary defense — learning how to change the path of an asteroid if one were ever heading toward Earth.

Why Does It Matter?

Every asteroid we study up close gives scientists more information about our solar system’s history. Asteroids are like time capsules from when the planets first formed, 4.5 billion years ago. Studying Torifune also helps JAXA practice the navigation skills needed for future asteroid missions — including ones that might one day protect Earth.

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Fun Fact

Hayabusa2’s final destination — asteroid 1998 KY26 — is only about 11 meters wide. That’s smaller than a basketball court! It would be the tiniest asteroid a spacecraft has ever visited.

Think About It

If scientists could gently nudge an asteroid off its path, what would be the best tool to use — a spacecraft that pushes it, a rocket that explodes nearby, or something else entirely? What would you design?

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