Meteor hurtling towards Earth explodes over the United States

A meteor* hurtling toward Earth exploded over the northeastern United States on Saturday local time, NASA has confirmed.

The meteor set off booms that echoed across the region.

The fireball broke up over northeastern Massachusetts and southeastern New Hampshire at 2:06pm (18:06 GMT), the US space agency’s deputy news chief Jennifer Dooren told AFP.

“This fireball was not associated with any currently active meteor shower, but it was a natural object and not a re-entry of space debris or a satellite,” she said.

“The energy released at break-up is estimated to be equivalent to about 300 tonnes of TNT*, which accounts for the loud booms.”

The meteor was travelling at more than 120,000km/hr at an altitude of 64km when it broke apart, Ms Dooren said.

Area residents were alarmed by the unexpected loud booms, with social media users reporting they were so powerful that houses were shaking.

It’s not the first unannounced arrival from space. In 2013, a fireball streaked above Chelyabinsk, Russia.

The house-sized space rock blew apart 22km above the ground, releasing a blast equivalent to 440,000 tonnes of TNT, NASA said.

The explosion blew out windows over 518km sq, injuring more than 1600 people, mostly due to broken glass.

The weekend meteor in America came less than a fortnight after a tiny, unannounced rock lit up skies much closer to home. For a brief moment on May 21, a small space rock approximately the size of a microwave turned up without warning.

Sydney’s cloudy evening sky turned white, with surf cams in the capital’s east showing a giant flash. Other angles captured a gigantic mass of light coursing through the clouds at breakneck speed.

The unexpected sight came as a sudden shock to anyone gazing east at 6.50pm. Social media exploded with Sydneysiders initially fearing a plane crash or missile strike. There was even a bit of optimistic* UFO chatter.

Normally astronomers* are all over this kind of event, broadcasting the imminent* arrival of the tiniest observable particle for amateur space fans to set their alarms to.

But for this one … nothing.

ANU astrophysicist Dr Brad Tucker said the object may have been just “30 to 50 centimetres in size, based on the brightness”, potentially smaller than a TV.

Its sheer speed was enough to light up the sky from Sydney to Canberra and beyond.

WHY WAS IT SO BRIGHT?
Meteors hit Earth’s atmosphere at tens of thousands of kilometres an hour. At those speeds, even a small object carries enough energy to superheat the air around it, fragment mid-flight and produce a brilliant flash far larger than the rock itself would suggest.

Dr Tucker said the bright flash likely showed the object breaking apart, while the green-blue colour pointed to metals such as iron and nickel*.

“People started to see this bright fireball, and then all of a sudden they got this bright flash happening,” he said.

“Enough pressure builds up with all the friction and pressure … it causes it to fracture.”

WHY WASN’T IT SPOTTED EARLIER?
The meteor slipped through because objects this small are incredibly hard to spot before they hit the atmosphere.

NASA-backed systems such as ATLAS are designed to detect larger near-Earth objects, with ATLAS saying it can see a roughly 20m asteroid* several days out and a 100m asteroid several weeks out.

Sydney’s meteor, by contrast, was likely too small to register.

That puts it in the very annoying category of space rocks that are too small, too dim and too fast to reliably detect in advance, but still big enough to produce a spectacular atmospheric light show when they finally show up.

Much larger objects have slipped through before, including that 2013 Chelyabinsk meteor. Even though it was 17 to 20m wide, it still arrived without warning.

NASA would later describe it as a “cosmic wake-up call”. Because that meteor came from near the direction of the sun, ground-based telescopes struggled to see the incoming phenomenon.

WHERE DOES THAT LEAVE US?
The European Space Agency has openly acknowledged that there are “an unknown number of asteroids on paths we cannot track hidden in the glare of our sun”.

While it might seem like sci-fi, global powers actually spend quite a bit on planetary defence.

NASA’s future NEO Surveyor* is one of the latest examples. The mission has been specifically designed to help detect asteroids approaching from the sun’s direction that were once invisible on the ground.

POLL

GLOSSARY

• meteor: a piece of rock or metal that burns very brightly when it enters the Earth’s atmosphere from space
• TNT: a powerful explosive substance, TNT is an abbreviation for “trinitrotoluene”
• optimistic: hoping or believing that good or exciting things will happen in the future
• astronomers: scientists who study the stars, planets and other natural objects in space
• imminent: coming or likely to happen very soon
• nickel: a chemical element that is a hard, silver-white metal used in making steel
• ATLAS: Asteroid Terrestrial-impact Last Alert System
• asteroid: an object like a very large rock that goes around the sun like a planet
• NEO Surveyor: NASA’s Near-Earth Object Surveyor is the first space telescope specifically designed to detect asteroids and comets that may be potential hazards to Earth

EXTRA READING

NASA move for medium asteroids

Webb telescope on asteroid’s tail

Aussie team to assess asteroid risk

QUICK QUIZ

1. NASA’s deputy news chief Jennifer Dooren said the meteor blast over the US released energy equivalent to what?
2. How fast was the meteor travelling and at what altitude when it exploded?
3. Most of the injuries after the 2013 meteor broke up above Chelyabinsk in Russia were caused by what?
4. The impact zone covered how many square kilometres?
5. The recent May 21 meteor seen across Sydney was thought to be what size?

LISTEN TO THIS STORY

CLASSROOM ACTIVITIES

1. Earth defence team
Work in a group of three to work on an important mission. You are to design the prototype of a contraption that can help deflect asteroids and meteors such as this one, back into the atmosphere to ensure no harm to humans.

Your system is up to you. Be imaginative and creative as you can using modern technology.

Sketch your idea and pitch to the class.

Time: allow 25 minutes to complete this activity
Curriculum Links: English, Science, Design and Technologies, Digital Technologies, Personal and Social, Critical and Creative Thinking

2. Extension
The article states the meteor released energy equal to 300 tonnes of TNT. Compare this amount of energy to other loud blasts such a:

• Volcanoes
• Fireworks
• Lightning
• Building demolitions

What precautions should we have taken if we knew the meteor was headed for Earth?

–

–

–

Time: allow 10 minutes to complete this activity
Curriculum Links: English, Science, Personal and Social, Critical and Creative Thinking

VCOP ACTIVITY
I spy nouns
Nouns are places, names (of people and objects), and time (months or days of the week).

How many nouns can you find in the article?

Can you sort them into places, names and time?

Pick three nouns and add an adjective (describing word) to the nouns.