Great Balls of Fire: Comets, Asteroids, Meteors
On October 1, Great Balls of Fire will open in the main galleries of the Newark Museum. This exciting exhibit explores the cutting edge of planetary science with comets, asteroids and meteors.
It is an excellent topic for an exhibit: for thousands of years we have been amazed by “shooting stars” and the graceful tails of comets as they swept across the nighttime sky. In ancient times we noticed lights moving slowly through the stars, called them planets and named them after the gods.
Ever since Galileo first spotted Jupiter and its moons in his small telescope we have wondered where planets come from and how our Solar System formed. After many years we have surveyed the major planets and moons with telescopes and spacecraft. Now we are probing even deeper, examining the smaller objects orbiting the Sun in order to understand the Solar System and its origins.
The small objects include asteroids, which are chunks of rock and iron. These are the “leftovers” from the formation of planets. Most are in the asteroid belt between Mars and Jupiter, but they can be found throughout the Solar System. They range in size from about 30 feet to 400 miles.
Comets are thought of as “dirty snowballs”. Comets range in size from 300 feet to 19 miles. These icy bodies spend most of their time in deep space but when they come close to the Sun, the ices turn to gas and release tremendous amounts of dust. This forms the graceful long tails for which comets are famous.
Deciphering a Comet
This summer the European Space Agency’s Rosetta spacecraft made an impressive rendezvous with a comet. Like its namesake, the famous Rosetta Stone, the probe will decipher the nature of comets in a unique way. Instead of flying past it for a brief glimpse, Rosetta is the first to orbit a comet and study it long-term.
Even more exciting is the small lander onboard spacecraft. It is named Philae after the location of an obelisk used to interpret the Rosetta Stone. For the very first time, it will set down on the comet’s surface to study it up close, determine its chemical composition and drill beneath its surface. The landing is currently scheduled for November 11.
Over the next several months Rosetta and Philae will ride the comet along its orbit as it approaches the Sun. This will be a spectacular trip astronomers have long yearned for.
Probing the Asteroid Belt
Meanwhile NASA’s Dawn mission is on an amazing journey through the asteroid belt in hopes of capturing the earliest moments of the Solar System’s formation. Dawn reached its first target, the asteroid Vesta, in July 2011. It orbited Vesta for a year making an in-depth study that revealed the asteroid to be much more complex than originally thought. Two enormous craters were discovered at its south pole. These impacts were so powerful that its surface folded at the equator, leaving behind massive troughs that circle the asteroid.
Careful study of Vesta reveals that is has a core, mantle and crust. Some speculate that Vesta is not just a mere asteroid but a remnant from the formation of the planets – exactly what astronomers hoped to find.
The mission gets even more amazing in the spring of 2015. Dawn will reach Ceres, the largest object in the asteroid belt and the only dwarf planet we know of in the inner Solar System. This will be our very first up-close look at a dwarf planet – a tantalizing taste of what is to come when the New Horizons spacecraft reaches Pluto next summer.
Wish Upon a Star
You don’t have to fly out to a comet or an asteroid to explore the Solar System. If you go outside on a clear dark night, you may see a piece of one of these objects. A “shooting star” is not really a star at all but a hunk of an asteroid or a speck of dust from a comet.
You can see a meteor in the sky just about any night if you are patient. It is said that nearly 100 tons of meteoritic material enters the Earth’s atmosphere every day. Much of this is fragments of asteroids. Most of these burn up and never reach the Earth’s surface. A few are large enough to reach the ground as meteorites. And in some cases we can have spectacular events such as the detonation of a 65-foot wide asteroid over the city of Chelyabinsk, Russia in February 2013. One of the largest impacts in recorded history also took place in Russia back in 1908. An object exploded in the air near the Tunguska River flattening 800 square miles of forest. This explosion was powerful enough to destroy a large city.
When comets get close to the Sun they release gas and dust. This is left behind and if the Earth passes through this debris we get a higher number of meteors as the bits of dust burn up in our atmosphere. This is a meteor shower. Alas you will not find any meteorites lying around after a meteor shower – these tiny bits all burn up.
We do have a couple of meteor showers coming up this fall. The Orionids come to a peak on October 22 (best between midnight and 5:30 a.m. on the morning of the 22nd). The Geminid meteor shower is one of the best of the year. Bright moonlight will spoil part of the shower but we should have a good view from about 9 p.m. on Dec 13 until moonrise around 1 a.m. on the morning of December 14.
Whether asteroid, comet or meteor, these diminutive members of the Solar System are fascinating objects in their own right and may be the key to greater understanding of our planetary system and its inner workings.
More than just satisfying our curiosity, greater awareness of these objects and how they threaten Earth will help us protect our planet and the life on its surface. Your chances of perishing in a cosmic impact are higher than winning the lottery: about 1 in 700,000. We need only to look at a dinosaur fossil to realize the peril of ignoring these fascinating objects.
In addition to Great Balls of Fire, the Dreyfuss Planetarium is featuring a new show about comets, asteroids and meteors called Firefall. There will also be a family festival, Astrofest, to celebrate the exhibition on Saturday, October 18.
– Kevin Conod, Manager, Dreyfuss Planetarium
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