Here’s Why June 30th is Asteroid Day And It’s A Little Freaky

A day to celebrate Asteroids? Sort of. Asteroid Day marks the anniversary of an explosion so enormous, researchers are still trying to figure out what happened.

Asteroid Day is recognized on June 30th and marks the anniversary of an explosion that was so enormous, researchers are still trying to figure out what happened.

The Tunguska Event

On the morning of June 30, 1908, there was a large explosion that occurred near the Stony Tunguska Eiver in Siberia. The explosion over the sparsely populated Eastern Siberian Tiaga flattened 770 square miles of forest, yet caused no known human casualties. The explosion is generally attributed to a meteoroid blowing up high in the atmosphere. It is classified as an “impact event” even though no crater has been found; the object is thought to have disintegrated at an altitude of 3–6 miles rather than to have hit the surface of the Earth.

The Tunguska event is the largest impact event on Earth in recorded history. Studies have yielded different estimates of the meteoroid’s size, on the order of 200–620 feet, depending on whether the body was a comet or a denser asteroid.

How Much Energy Are We Talking about?

Early estimates of the energy of the air burst range from 10-15 megatons of TNT to 30 megatons of TNT. Modern supercomputer calculations that include the effect of the object’s momentum find that more of the energy was focused downward than would be the case from a nuclear explosion and estimate that the airburst had an energy range from three to five megatons of TNT.

The 15-megaton estimate represents an energy about 1,000 times greater than that of the atomic bomb dropped on Hiroshima, Japan!

It is estimated that the Tunguska explosion knocked down some 80 million trees over an area of 830 square miles, and that the shock wave from the blast would have measured 5.0 on the Richter scale. An explosion of this magnitude would be capable of destroying a large metropolitan area, but due to the remoteness of the location, no human fatalities were officially documented.

So What Is Asteroid Day?

Asteroid Day aims to raise awareness about asteroids and what can be done to protect the Earth, its families, communities, and future generations from another potential catastrophic event. It has been an annual event since 2004, but has slowly become more well-known in recent years worldwide. It became official in 2015. Asteroid Day was co-founded by Stephen Hawking, filmmaker Grigorij Richters, B612 Foundation President, Danica Remy, Apollo 9 astronaut Rusty Schweickart and Brian May, Queen guitarist and astrophysicist.

Who knew Brian May from the band Queen was an astrophysicist? He is also the co-founder of Astronomy Day. Take a look at the video below:

For more details visit the official website for Asteroid Day!

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Joe Rao is an expert astronomer.
Joe Rao

Joe Rao is an esteemed astronomer who writes for, Sky & Telescope, and Natural History Magazine. Mr. Rao is a regular contributor to the Farmers' Almanac and serves as an associate lecturer for the Hayden Planetarium in New York City.

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