You are looking up into the night sky and you finally see one, a shooting star! You close your eyes and make a wish. A few minutes later to your amazement you see another!
“What are the odds?” you think to yourself as yet another one shoots across the sky. While you might think this is your lucky night, this is actually a common and reoccurring event, known as a meteor shower.
What is a Meteor Shower?
The Earth often experiences many meteoroids at once. What differentiates a meteor shower from just a highly active night sky with multiple shooting stars? A meteor shower’s meteors all originate from one point in the sky.
Why would the Earth encounter many meteoroids at once? This happens when the Earth passes through a region in space filled with debris. This debris is most often caused by a comet.
Like Earth, comets orbit the Sun. As a comet zips closer to the Sun, it leaves a trail of debris behind it. When the Earth’s orbit crosses the path of the comet’s orbit it crashes into the debris the comet leaves behind. Since both the comet’s orbit and Earth’s orbit follow the same path, the Earth will pass through this debris trail on a regular basis.
We experience approximately 30 meteor showers every year and distinguish them by which constellation they appear to be originating from. Some of these showers we have been seeing for over 100 years. Since they occur at approximately the same time every year, you can plan to catch one!
Geminid Meteor Shower
One of the most well-known meteor showers is the Geminid Meteor shower. This meteor shower occurs every year between November 19th and December 24th. A general rule of thumb is the higher the constellation the meteors appear to be radiating from – the radiant point – the more shooting stars you’re likely to see.
The Geminid’s radiant point almost lines up with the bright star Castor in the Gemini constellation. This alignment is completely by chance. Castor is 52 light years away from Earth, while the meteors burn up in our sky about 100 km above the surface.
Meteor showers are best experienced on a clear night with a New Moon. A Full Moon produces enough light in the sky to outshine most faint meteors. If there is no interference from moonlight, you can see up to 150 meteors per hour during the Geminid meteor shower.
While the Geminids can be seen from the Southern Hemisphere it is most prominent from the Northern Hemisphere. The Geminids shower is unique in that it is actually caused by an asteroid not a comet.
This asteroid is called Phaethon that has a rare blue color and an extremely eccentric orbit that we usually only see with comets. Astronomers are not sure how Phaethon created the Geminids, because unlike a comet, it does not expel debris as it gets closer to the Sun.
Phaethon’s trail of debris is currently a mystery. While some dust can be swept off the surface of the asteroid as it travels through space, it is not enough to sustain the Geminid shower. One possibility is that Phaethon collided with another object long ago, and the Geminid shower is the debris from that event.
Another possibility is that Phaethon is a dormant comet that turned into an asteroid over time. The Geminid shower is created from the crumbs left behind from the comet as expected. In either case, because Phaethon is an asteroid it is no longer producing debris. This means that there once we run out of debris to cross paths with, we will no longer see the Geminid shower.
While this may not happen for hundreds or thousands of years, try to see it while you can!
Tips for Geminid Meteor Shower Viewers
- Best viewing is with a dark open sky. If you can find a place away from city lights, you will see more shooting stars.
- For all parts of the globe the Geminid shower will peak at 2 am. This year there is a waning gibbous moon lighting up the sky so visibility will not be as good this year.
- Having a buddy to watch the shower with is perfect. You each can look at different parts of the sky and call out when you see one. This teamwork will let you see more meteors than watching a shower by yourself. It is also nice to share this great experience with someone.
- Try and give yourself at least an hour or more to observe the shower. It will often take about 20 minutes for your eyes to adapt to the dark so that you can see some of the fainter meteors as well.
- Meteor showers are not a constant stream. There spurts of many meteors with lulls of no activity in between.
- You do not need any special equipment to see this meteor shower.