It is often difficult for parents to help their children with science education, in part because the idea of doing science with your child can be intimidating. Parents often feel at sea when it comes to science lessons, and the notion of a laboratory science experiment conjures images of expensive equipment, complex instructions, the specter of failure hangs heavily in the air. No parent wants to go to time, trouble and expense to set up an experiment for the kids only to have it fail!
A meteor shower represents the ultimate in science experiences for both parent and child. Nature provides the setup and all the materials, all we have to do is watch the show with our kids – but what is this magnificent show of fiery streaks across the night sky actually demonstrating? How do we use this natural show to teach our kids something about astronomy and science? As it turns out – the process is an easy one.
Meteors (we often call them ‘falling stars’) happen when a bit of ice, stone or metal collides with the Earth’s upper atmosphere at many times the speed of sound. When anything enters the atmosphere at 35,000 kph, friction with the atmosphere heats the object to well over 10,000 oF within seconds, causing the object to burn away in a brilliant streak of fire that stretches silently across the night sky for just a few seconds. Although they are burning furiously at tremendous temperatures, meteors are virtually never a danger to us on Earth – they burn up completely in the air and most do not get within 20 km of the surface before they are destroyed. The great height at which they burn up also shows why meteors are completely silent – even if they are directly overhead, they will still be many miles away when they burn up; much too far away to be heard by those of us watching on the ground!
Random meteors can appear from any part of the sky, and at any time of day or night. If you are in a dark location, well away from city lights, you can see 5-10 meteors per hour on any given night of the year. These meteors are single bits of carbon, iron, stone, or ice that have remained intact from the formation of the solar system 4.7 billion years ago. They have been floating in space, orbiting the Sun for that entire time, only to eventually collide with the Earth as it moves in its own orbit about the Sun. Spotting a random meteor can be problematic. Although several appear each and every hour of the night, you must be looking in the right direction at the time or you will likely miss them – frustrating both parent and child!
Meteor showers are quite different. Unlike random meteors, which have no pattern and cannot be predicted at all, meteor showers come from debris left behind by comets as they orbit the Sun. Comets follow predictable orbits, leaving a trail of dust, bits of rock, and ice particles behind them. When the trail is fresh, it glows in the Sun’s light producing the comet’s characteristic tail. In a relatively short time however, the trail grows cold and stops glowing – but it does not go away! This trail of cosmic debris left behind the comet hangs in space – there are no winds to disturb it and no great gravity field that would cause it to settle out like dust does on surfaces on the Earth – and every trip around the Sun that the comet makes adds more dust and debris to the trail!
Earth orbits about the Sun at 30,000 kph (almost 30x the speed of sound!). At these tremendous speeds, when Earth plows through the comet’s debris trail, hundreds or even thousands of meteoroids can strike the Earth every hour. This fiery show is what we call a meteor shower; because it occurs predictably each year when the Earth reaches a particular point in its orbit, we can predict the nights when meteor showers will occur – making it easy for parents, teachers and students to plan to be out observing when the big show occurs! And since a meteor shower will provide many more meteors per hour, and all in a relatively short time, it becomes easy for everyone to see and enjoy them.
The problem with observing a meteor shower is that they are best observed late at night. We can see this with the little diagram below. In our diagram, the lower half of the Earth is in daylight – that part of our planet faces the Sun in the center of Earth’s orbit; the upper half of the planet is the night side. Now consider that the Earth is in motion around the Sun. The portion of the Earth that is exposed to the brunt of the meteor shower is the part which is facing forward in orbit.
Just as bugs splat! on the front window of a car when it drives along, so the meteors will smear themselves out in a fiery trail on the “front window” of our atmosphere – the portion that is facing forward in space. You can see that this means that the best of the meteor shower occurs after midnight. Although this is true, in practice we find that meteor shower activity picks up substantially after 9PM and increases until about 3AM. Some people find that they prefer to get up early in the morning (just before dawn) to catch the tail end of the meteor shower. No matter which you choose – you will find many more meteors per hour in the sky on a meteor shower night than any random night of the year. Meteor shower night is always worthwhile – even if you can’t stay up really late!
So what do we see on a meteor night? Evidence that the Earth moves through space! Copernicus, Kepler, and Galileo all struggled to find proof that the Earth moved in orbit around the Sun; the radial pattern of meteors all seeming to spread out from a single point in the sky is visual evidence that the Earth is moving in orbit about the Sun. A child and parent with a star map can trace out the paths of meteors that they see, building up this wonderful radial pattern over a period of a few hours showing positively that the Earth must be moving through space. We also see evidence of planet building. How did the Earth get here? In fact, it was built up by accretion, small particles colliding and sticking together to build a larger body. Every time you see a meteor, the Earth has absorbed it, and become just a bit bigger. Astronomers estimate that the Earth may acquire some ten million tonnes of meteoric material each year – effectively making our planet just a little bit bigger! When we see a meteor shower, we actually watch our planet getting bigger! We are observing the cosmic process of planet building in action.
The list below gives some of the best meteor shower nights for 2013. Each shower may spread itself out over a period of days, with a peak on a particular night. Just because you can’t get out on the night of the peak doesn’t mean that you should give up – the days just before and after a meteor shower can be productive as well! In addition to the peak days, each shower gives the predicted meteor rate for that shower, called the Zenithal Hourly Rate or ZHR, which tells how many meteors per hour are expected from this shower. The higher the ZHR, the more meteors you can expect to see.
When you go out to observe a meteor shower, observe a few simple guidelines:
- Find the Dark. Seek a dark place away from city lights and traffic. The darker your location, the more meteors you will see. Dark skies allow your eyes to adapt fully, and faint meteors are best seen against a dark sky.
- Be Safe! Visit your observation site by daylight. Know where you are going, and be sure you won’t stumble over unseen obstacles. Never observe from a roadside location, be sure you are well away from any traffic hazards! Safety also lies in numbers, be sure you go observing with friends, meteor night is more fun when you observe with others!
- A beach chair, warm blanket, and a thermos of coffee will be welcome as the night progresses. Observing meteors isn’t particularly active, and the cold can spoil a fun night if you aren’t dressed for it!
Here are the best meteor shower nights for 2013, organized chronologically for you! Remember that the peak meteor show occurs early in the AM hours (just after midnight). If you want to observe a peak on May 6th for instance, go out late on May 5th – and stay up into the early morning hours of the 6th for the best show!
January 3rd (Thur): Quadrantids – active from Dec 28 – Jan 12
Named for an extinct constellation called Quadrans Muralis (The Mural Quadrant), this shower’s radiant point is in northern Boötes. The gibbous Moon rises near midnight, spoiling the view for this year. Not expected to be easily seen except with cameras as the Moon will wash out most visible activity.
April 22nd (Mon): Lyrids – active from Apr 16 – 25
The constellation Lyra (the Lyre or Harp) contains brilliant blue-white Vega, one of the brightest stars in the northern skies. Vega makes it easy to spot the radiant area for this shower each year which lies between Lyra and Hercules. Predictions this year are for 18-25 ZHR (meteors per hour), but recent years have had outbursts of activity up to 90 ZHR. 2013 Lyrids will have to share the sky with a nearly full Moon that will wash out all but the brightest. That said, the Lyrids are noted for a few spectacularly bright fireballs, so they may be worth watching for anyway.
May 6th (Mon): Eta Aquarids – active from Apr 19 – May 28
The radiant for this shower is the Y-shaped urn in the constellation of Aquarius (The Water Bearer) which rises only an hour or two before dawn. Usually swift, bright and tending to leave persistent trails easily seen with the eye or binoculars, the Eta Aquarids are best thought of as a pre-dawn show. This shower is associated with Comet Halley, as are the Orionids which occur in October.
June 11th (Tue): Gamma Delphinids – active window is very narrow, 11th only?
Named for Delphinus (the Dolphin), this shower is rarely seen, but the folks at NASA have said that this year may be ideal for an outburst of activity up to 50-100 ZHR! Waning crescent Moon presents an ideal night with little or no lunar interference for this shower.
July 30th (Tue): Delta Aquarids – active July 12 – Aug 23.
16-20 ZHR, slow & faint meteors; perhaps 10% will leave a persistent trail.
August 12th (Mon): Perseids – active July 17 – Aug 24.
The real show of the summer, named for a radiant in the constellation Perseus (the Hero). Expect 100 ZHR this year, with a possible outburst of 200 ZHR on the night of the 11th or 12th. Fast and bright, many Perseid meteors leave persistent trains in their passing. The waxing crescent Moon sets early and will offer dark skies to observers for meteor night!
October 8th – 10th (Tue-Thur): Draconids & Southern Taurids – active October 6-10 and Sept 10-Nov 20 respectively.
The Draconid shower peaks on October 8th, and the Taurid shower peaks just two days later. Neither shower is expected to show more than 10 ZHR, but outbursts have been noted in the past and the waxing crescent Moon offers excellent dark skies for watching meteors on both nights.
October 21st (Mon): Orionids – active Oct 2 – Nov 7.
Associated with Comet Halley, this shower is first part of the fall classic, followed by the Leonids in mid‑November. 20-25 ZHR is typical for this shower, but outbursts of up to 70 ZHR have been seen in 1993, 98, 2006, and 2009, so 2013 could be a good year to check out the Orionids!
November 17th (Sun): Leonids – active Nov 6-30.
15-25 ZHR, swift and bright, the Leonids always make a good show, but the full Moon will clobber them this year, making observations of all but the few very brightest meteors impossible.
December 13th (Fri): Geminids – active Dec 4-17.
A very active shower with ZHR up to 120. A waxing gibbous Moon will interfere with the sky until near dawn. The cold winter nights also do not invite long observing sessions in most parts of the globe! Think of this year’s Geminids as a good pre-dawn show on the morning of the 13th!
By Dr. Daniel Barth. Dr. Barth is a former research scientist who turned his talents for innovative laboratory work toward teaching science. Dr. Barth was awarded the prestigious 2009 Amgen Award for Excellence in Science Education and he was awarded the “Science is For Kids” Foundation fellowship in 2009. He was recently nominated for the 2010 Presidential Award for Excellence in Mathematics and Science Teaching. You can read his full bio here. You can learn more about Dr. Barth and his Maurice on the Moon curriculum by visting his website, www.mauriceonthemoon.com. You can email Dr. Barth at email@example.com.