International Asteroid Day

Black and white photograph of an asteroid captioned "International Asteroid Day"

International Asteroid Day is observed every year on June 30th. Also known as National Meteor Watch Day, on a cloudless night, STEMists turn their eyes to the sky in hopes of spotting the glow of a falling star.

What is an Asteroid?

Asteroids are small, rocky objects that orbit the sun. Asteroids orbit the sun like planets, but they are much smaller than planets.

What is a Meteoroid?

Sometimes one asteroid smashes into another asteroid. This can cause small pieces of the asteroid to break off. Those small pieces are called meteoroids.

What is a Meteor?

If a meteoroid comes close enough to Earth and enters Earth’s atmosphere, it vaporizes and turns into a meteor: a streak of light in the sky. Because of their appearance, meteors are sometimes called “shooting stars.” But scientists know that meteors are not stars at all—they are just bits of rock!

What is a Meteorite?

Sometimes meteoroid rocks don’t vaporize completely in the atmosphere. In fact, sometimes they survive their trip through Earth’s atmosphere and land as rocks on the Earth’s surface. Those rocks are called meteorites.

An illustration of a Meteroid and an Asteroid.
Most asteroids in our solar system can be found in the asteroid belt between Mars and Jupiter.
Most asteroids in our solar system can be found in the asteroid belt between Mars and Jupiter.

When space debris, such as pieces of rock, enter the earth’s atmosphere the friction causes the surrounding air to become scorching hot. This “shooting star” streaking through the sky surrounded by flaming hot air is a meteor. The majority of the meteoroids that cause meteors are only the size of a pebble.

Meteors sometimes occur in showers. National Meteor Watch Day is the right moment to plan for a meteor-watching party. Whether it is to catch a few stray falling stars or to watch the entire meteor dropping, gathering the kids or a few friends to map the constellations while waiting to make a wish or two is sure to be a fun time.

A photograph of a meteor shower.
At certain times of the year, you might be lucky enough to see more meteors in the sky than usual. This is called a meteor shower. This photo was taken during the Perseid meteor shower, which happens each year in August. Image credit: NASA/JPL

In the Northern Hemisphere, one of the most active meteor showers is the Perseids. The Perseids were named in honor of the constellation Perseus the Hero as this seems to be its point of origin. The meteors are caused by particles released by the comet 109P/Swift-Tuttle. Active from mid-July to late August, the Perseids put on a dazzling display at its peak, especially when the skies are clear and the moon is new.

Meteors are usually observed at night. They are very visible when they are about 34 to 70 miles above the Earth. They often disintegrate at about 31 to 51 miles above the Earth. Their glow time is usually about a second.

A small percent of meteoroids hit the Earth’s atmosphere and then skip back into space.

The chemical composition and the speed of the meteoroid will cause different hues to the light. Possible colors and elements producing them include:

  • Orange/yellow (sodium)
  • Yellow (iron)
  • Blue/green (copper)
  • Purple (potassium)
  • Red (silicate)

Asteroid Day events will address science as well as government and private-sector initiatives to study asteroids, and particularly advanced efforts to develop greater detection, tracking and deflection techniques. Additionally, the events are independently produced by space agencies, universities, science centers, planetariums, observatories, museums, schools, theaters, libraries, local governments, and other civic organizations. Most events are aimed at citizens of all ages and are free of charge.

Meteor Shower Dates for STEMists

  • January 4, 2019 Quadrantids
  • April 23, 2019 Lyrids
  • May 5, 2019 Eta Aquariids
  • Late July, 2019 Delta Aquariids
  • August 12, 2019 Perseids
  • October 9, 2019 Draconids
  • October 21, 2019 Orionids
  • November 5-6, 2019 South Taurids
  • November 12-13, 2019 North Taurids
  • November 18, 2019 Leonids
  • December 13-14, 2019 Geminids

This list and a guide to successful watching can be found on the EarthSky website.

How to Observe

Plan your night. Gather some of your STEM Friends together with a blanket and find a place far from the city lights on a cloudless night.

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  • Emphasis on STEM (science, technology, engineering and math)
  • Extended learning through our exclusive online portal
  • For children ages 8 and up

Top Photo: A close-up view of Eros, an asteroid with an orbit that takes it somewhat close to Earth. The photo was taken by NASA’s Near Earth Asteroid Rendezvous – Shoemaker spacecraft in 2000. Image credit: NASA/JHUAPL

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