Catch a ‘shooting star’ this month — and most others | Science News for Students

Catch a ‘shooting star’ this month — and most others

Rice-sized grains of space rock produce these meteor showers
Dec 11, 2018 — 12:00 pm EST
meteor shower over mountains

Commonly called ‘shooting stars,’ these streaks of light in the night sky are meteors caused by bits of space rock crashing into Earth’s atmosphere. The ones shown here are part of the annual Geminid shower.

sripfoto/iStockphoto

They’re called shooting stars. In fact, they’re only bits of space rock burning up in Earth’s atmosphere. This month’s Geminid (JEM-in-id) meteor shower will briefly send streaks of light across the heavens after dark. The night of December 13 (into the 14th) should offer peak viewing. Up to 100 of these shooting stars will spark overhead every hour.  But people are still likely to catch a few stragglers the day before and after.

During some years, a bright, nearly full moon will outshine the fainter meteors. This year's event occurs as the moon enters its first quarter phase. So its face will be only halfway illuminated during the show’s peak. That means plenty of meteors should be visible. Plus, the moon sets before midnight in the lower 48 U.S. states. That means the second half of the night should offer great viewing — if the weather cooperates.

This light show has a humble beginning. Most shooting stars actually are due to rock shards only the size of a rice grain. These interstellar bits are the leftovers of comets, asteroids and larger celestial bodies hurtling through space. Often, these objects leave behind trails of debris in their wake, like pebbles falling off a construction truck.

In the case of this week’s Geminid shower, the space pebbles shooting across the sky come from 3200 Phaethon. This asteroid is a rock 5.8 kilometers (3.6 miles) in diameter. That size was estimated in 2017 during an experiment led by NASA’s Jet Propulsion Laboratory in Pasadena, Calif. That parent rock is the source of all the tiny shards that light the sky on fire each mid-December.

The Geminids get their name because they appear to come from the constellation Gemini. If you traced back the paths of all Geminid meteors from Earth’s perspective, that is the part of the sky from which they appear to emerge. So Gemini is what’s called the radiant of this shower.

Geminid meteor shower, 2014
A brilliant Geminid meteor burns through the atmosphere over Cape Cod, Mass., on December 13, 2014. The stunning meteor shower sent dozens of lime-green streaks across the sky. The author witnessed 46 shooting stars in three hours during the Geminid show a year earlier.
K.D. Cappucci and M.E. Cappucci

The Geminids tend to be the most dramatic and colorful meteor showers of the year. That’s because at roughly 125,000 kilometers (78,000 miles) per hour, they are relatively slow. Their sluggish speed means they last longer in the sky, making them relatively easy to spot. And they leave a brilliant trail that lasts three to four long seconds. In comparison, the Perseid (PER-see-id) showers each August send meteors shooting through the atmosphere at 209,000 kph (130,000 mph).

Their colors are the most amazing part of these light shows. Shooting stars during the Geminids shine a deep, emerald green. Sometimes the edges are tinged violet. A few might even glimmer with a bit of pink, white, yellow or blue. Their colors trace to the minerals in their rocky parent. The Geminids are rich in magnesium, sodium, and iron.

As the rock bits zip through the atmosphere, friction causes them to burn up. In the process, the meteors ionize the air around them, creating azure to turquoise hues. That causes gases in their wake to glow vibrant colors even after the rocks have burned up.

Fireballs are extremely bright meteors that penetrate lower into the earth’s atmosphere. They appear larger and can light up the sky as bright as daytime for a few seconds. Any shooting star brighter than Venus tends to be called a fireball.

The Geminids tie with the Perseid meteor shower for producing the most fireballs.

Other meteor showers

Meteor showers aren’t overly rare. More than a dozen occur each year. How big a display each offers depends on how many space specks they shoot into our atmosphere as meteors. But a show as good as this year’s Geminids only comes once every few years.

Next month will feature the Quadrantids (Kwan-DRAN-tidz). They peak for only a few hours. Still, they have impressive streak rates. For a few hours the night of January 3 to 4, viewers may witness 100 shooting stars per hour.

The Lyrids show up in April. The Eta Aquarid shower produces a few sporadic meteors every May. The Leonids show up every November. And if you’re looking for a good summer memory, then check out the Perseids. Each August 12 to 13, this meteor shower sends more than 100 meteors flying overhead every hour! It’s the best of the year — unless you’re willing to brave a crisp, cold December night for the Geminids.

For best viewing

To catch any meteor show, patience is key.

Pack a blanket, pillow or anything else you need to be comfy as you can. Then bring it to a place with wide open views. The lower to the horizon that you can see, the better. This puts more stellar real estate in view, upping the share of meteors you can glimpse. Ball fields, golf courses and beaches are ideal. Of course, safety is essential — so make sure you are with a group at a safe location.

The spot you choose also needs to be dark. The hours around midnight are the best for viewing. Check local moonset times in your city to figure out when skies will be the darkest. It may also help to monitor the latest weather forecast to know when the best odds of clear skies will be.

Your eyes have to adjust to be sensitive enough to see all the visible stars. Under perfect conditions beneath a moonless sky, you should be able to discern nearly 5,000 stars.

Here’s how to view a meteor shower, such as December’s annual and prolific Geminids.
M. Cappucci

Now lay back and stare upwards. There’s no need to search for the radiant. Shooting stars will eventually streak across the sky.

Above all, it’s important to not give up too soon. Sometimes meteors come in little “packets.” A flurry of three our four may be preceded by several minutes of nothingness.

And put away cell phones. Their concentrated blue light will cause your eyes to adjust back to “daytime mode.” That means no snaps, tweets or other social media that normally captures your attention. Your phone camera won’t be able to capture shooting stars, so don’t even bother trying. Challenge yourself to go an hour technology-free and bask in the wonder of the universe above.

What if it’s cloudy?

Even if it’s cloudy, you still have a chance to marvel over meteors. NASA has a “listening” station at the Marshall Space Flight Center in Huntsville, Ala. It can detect the echoes of radio waves bounced back by meteors. The system is more sensitive than the human eye. At any given time, it can detect between two and 10 more shooting stars than a person would see in a dark sky. You can listen online to the meteor radar’s pings as it captures signals of the meteors.

Power Words

(more about Power Words)

asteroid     A rocky object in orbit around the sun. Most asteroids orbit in a region that falls between the orbits of Mars and Jupiter. Astronomers refer to this region as the asteroid belt.

atmosphere     The envelope of gases surrounding Earth or another planet.

celestial     (in astronomy) Of or relating to the sky, or outer space.

comet     A celestial object consisting of a nucleus of ice and dust. When a comet passes near the sun, gas and dust vaporize off the comet’s surface, creating its trailing “tail.”

constellation     Patterns formed by prominent stars that lie close to each other in the night sky. Modern astronomers divide the sky into 88 constellations, 12 of which (known as the zodiac) lie along the sun’s path through the sky over the course of a year. Cancri, the original Greek name for the constellation Cancer, is one of those 12 zodiac constellations.

debris     Scattered fragments, typically of trash or of something that has been destroyed. Space debris, for instance, includes the wreckage of defunct satellites and spacecraft.

diameter     The length of a straight line that runs through the center of a circle or spherical object, starting at the edge on one side and ending at the edge on the far side.

fireball     A lump of rock or metal from space that hits the atmosphere of Earth. Fireballs are meteors that are exceptionally bright and large.

friction     The resistance that one surface or object encounters when moving over or through another material (such as a fluid or a gas). Friction generally causes a heating, which can damage a surface of some material as it rubs against another.

hue     A color or shade of some color.

interstellar     Between stars.

ionize     To strip electrons from an atom or molecule, creating electrically charged particles. Electrons will have a negative charge. The atom or molecule that they left is left with a net positive electrical charge.

meteor     A lump of rock or metal from space that hits the atmosphere of Earth. In space it is known as a meteoroid. When you see it in the sky it is a meteor. And when it hits the ground it is called a meteorite.

monitor     To test, sample or watch something, especially on a regular or ongoing basis.

moon     The natural satellite of any planet.

NASA     Short for the National Aeronautics and Space Administration. Created in 1958, this U.S. agency has become a leader in space research and in stimulating public interest in space exploration. It was through NASA that the United States sent people into orbit and ultimately to the moon. It also has sent research craft to study planets and other celestial objects in our solar system.

radiant     (adj.) A term for something that is radiated, such as heat or some other type of radiation. (n.) The point or object from which light or heat radiates (such as the heating element in an electric heater). Or the point from which objects (such as meteors) appear to come.

radio waves     Waves in a part of the electromagnetic spectrum. They are a type that people now use for long-distance communication. Longer than the waves of visible light, radio waves are used to transmit radio and television signals. They also are used in radar.

shard     A piece of broken pottery, tile or rock, or a hard, broken piece of anything that has an irregular shape.

social media     Internet-based media, such as Facebook, Twitter and Tumblr, that allow people to connect with each other (often anonymously) and to share information.

sporadic     An adjective that describes events that occur infrequently and at unpredictable intervals.

star     The basic building block from which galaxies are made. Stars develop when gravity compacts clouds of gas. When they become dense enough to sustain nuclear-fusion reactions, stars will emit light and sometimes other forms of electromagnetic radiation. The sun is our closest star.

stellar     An adjective that means of or relating to stars.

technology     The application of scientific knowledge for practical purposes, especially in industry — or the devices, processes and systems that result from those efforts.

tweet     Message consisting of 140 or fewer characters that is available to people with an online Twitter account.

universe     The entire cosmos: All things that exist throughout space and time. It has been expanding since its formation during an event known as the Big Bang, some 13.8 billion years ago (give or take a few hundred million years).

Venus     The second planet out from the sun, it has a rocky core, just as Earth does. Venus lost most of its water long ago. The sun’s ultraviolet radiation broke apart those water molecules, allowing their hydrogen atoms to escape into space. Volcanoes on the planet’s surface spewed high levels of carbon dioxide, which built up in the planet’s atmosphere. Today the air pressure at the planet’s surface is 100 times greater than on Earth, and the atmosphere now keeps the surface of Venus a brutal 460° Celsius (860° Fahrenheit).

wake     An area of disturbed air or water left behind an object (such as a boat or animal) moving through it.

weather     Conditions in the atmosphere at a localized place and a particular time. It is usually described in terms of particular features, such as air pressure, humidity, moisture, any precipitation (rain, snow or ice), temperature and wind speed. Weather constitutes the actual conditions that occur at any time and place. It’s different from climate, which is a description of the conditions that tend to occur in some general region during a particular month or season.

Citation

Explainer: Spaceweather.com. The MFSC Online Meteor Radar In cooperation with Rob Suggs, Bill Cooke, and Jeff Anderson of Marshall Space Flight Center in Huntsville, Alabama.

Article: J. Rao. Shooting star reflections: The Great Leonid Meteor storm of 1966. Space.com.  November 14, 2011.

Meeting: Borovička J. et al. Structure and composition of Geminid meteors and implications for the nature of Phaethon. Astronomical Institute of the Academy of Sciences. Presented at the 10th annual Asteroids, Comets, and Meteors meeting. 14-18 July, 2008.   

Journal: J. Licandro et al. (2006). The nature of (3200) Phaethon. Astronomy & Astrophysics. Vol. 461, January 11, 2007, p. 751. doi: 10.1051/0004-6361:20065833.