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Asteroid Day

Today marks the international day of awareness and education about asteroids – Asteroid Day! It’s a huge program, organising events all over the world, and headquartered from Luxembourg. The date of June 30th was chosen specially to mark the anniversary of the Tunguska event. In 1908 Siberia, an asteroid exploded, flattening 2,000 square kilometres of forest with a force a thousand times more powerful than the atomic bomb dropped on Hiroshima in 1945. So, today’s the perfect day to learn all about asteroids!

What is an asteroid?

Asteroids are small rocky bodies that orbit the Sun. They are normally classed as minor planets, especially those within the inner solar system. There are millions of them in our solar system alone: over 150 million, and that’s only those larger than 100m that are in the inner solar system! Despite this, the Asteroid Belt (where most asteroids originate) is mostly empty space. This is because, compared to the planets and their moons, asteroids are generally miniscule. In fact, 25% of the Asteroid Belt’s total mass is contained, not within asteroids, but in the form of the dwarf planet Ceres. And yet, Ceres is 14 times smaller than Pluto!

Most of the material that makes up asteroids is rock and stone, but some have more exotic materials. A few contain iron and nickel metals, and some contain carbon-based materials. Asteroids that orbit further out can also contain ices. There’s even evidence of water in some of them! In addition, their small size and mass means that none of them are big enough to form spheres. Instead, the rock forms irregular, clumpy shapes.

Is the Earth in danger?

At the moment, it’s unlikely. There are currently 1062 NEAs (Near Earth Asteroids) on the ESA risk list. But don’t panic – the probability of any of them hitting us is extremely low. When asteroids are put on the list, their predicted date of impact is also estimated. This can range from right now all the way into the 2100s, so scientists have a pretty good idea about the threat level. In fact, lots of tiny asteroids hit the Earth all the time, with no adverse effects. It’s only when larger asteroids are on course for the Earth that we need to worry.

Having said that, we don’t have any certain way of protecting the Earth if an impact was to happen. Scientists can’t be totally sure that an asteroid will hit us until it gets fairly close, so everything has to be based on probabilities. There are a few ideas that could be tested out, such as ESA’s Hera mission or the theoretical gravity tractor. But until we know they are going to work, our planet is vulnerable. It’s the aim of Asteroid Day and its supporters to change this.

What is Asteroid Day?

Asteroid Day is a global awareness campaign. It was started by Dr. Brian May, astrophysicist and lead guitarist of Queen, alongside Danica Remy, President of B612 Foundation, Rusty Schweickart, Apollo 9 astronaut, and filmmaker Grig Richters. It began in 2014, with a petition, known as the 100X Asteroid Declaration, that garnered public support and urged governments to take action to increase the tracking and detection of asteroids. In 2016, 30th June was given official designation as Asteroid Day by the United Nations.

Asteroid Day organise all kinds of things throughout the year. Although live events can’t happen this year, you can watch their web TV for loads of interesting programs. Check it out today for special Asteroid Day content!

Sources: Asteroid Day, Encyclopaedia Britannica, NASA,, Universe Today