For a few weeks last summer, comet NEOWISE was visible to the naked eye in the sky. Such a visit is rare: the last comet this bright in the northern sky was Hale-Bopp in 1997. Many people got the chance to see their first comet, and thousands of pictures were posted on social media.
What about you? Did you get the chance to see it? In the sky, or only in pictures? Why was this comet visible last summer? And what is a comet, anyway? Here's some information to help you introduce your students to these wonderful visitors from the far reaches of our Solar system!
© François Quesnel - Comet NEOWISE as it appeared to the eye and through binoculars (or a small telescope).
WHAT IS A COMET?
Comets are small objects in the Solar system which can be identified by their composition and their orbit. They are mostly made of different types of ice which then turn to gas and dust particles when they get closer to the Sun. These transformations form the tail of the comet, which can sometimes be seen in the sky. Contrary to what we sometimes see in cartoons, the comet's tail isn’t made of fire; we simply see it because it reflects the light from the Sun.
Comets usually have a very elongated orbit and spend most of their time far away in the Solar system. It’s only when they get closer to the Sun that their tail forms. Many comets visit the Sun’s neighbourhood every year, but most of them can only be observed with an instrument such as a telescope.
The full name of the comet is NEOWISE C/2020 F3. This complicated notation indicates who discovered it, the type of comet, and when it was discovered – in this case, March 2020. The nucleus of the comet was only about 5 km across but its tail stretched over hundreds of thousands of kilometers, possibly even millions!
Use the site TheSkyLive.com to simulate the orbit of the comet in 3D and its position over time and discuss with your students:
How is the orbit of the comet different from the orbits of the planets? Think about its shape and its orientation in space.
Start the animation with the desired speed (default: 1 week = 1 second) and notice how the comet’s speed changes as it gets closer to the Sun and as it moves further away.
You can go back to the moment when the comet made its closest approach to the Sun (July 3, 2020) and to the Earth (July 23, 2020 – as shown in the picture above). During those weeks, and shortly after, the comet was visible to the naked eye in the sky.
The comet is now moving away from the Earth and the Sun on its return trip to the far reaches the Solar system. It will come back to visit us in many thousands of years!
WHAT COULD BE SEEN IN THE SKY
Did many of your students manage to see it? Would the answer be different if your school was located in a city / rural area? Unfortunately, light pollution in the city caused by all the light sources obscured the comet from most peoples' view.
Under a dark sky, the comet appeared like a small white trail below the Big Dipper in the constellation Ursa Major. Through binoculars, the comet's tail could be seen much more clearly.
Many pictures of comet NEOWISE were taken. Some were magnified and the majority had long exposure times, which allowed fainter details to be highlighted. No, it wasn't as obvious to the naked eye, but it was a nice show nonetheless! Here are some of our favourite pictures taken from across Canada.
TO LEARN MORE...
Here are a few resources to help you familiarize your students with comets :
Wonderful animated series on the Rosetta mission which visited a comet in 2014-2016. By the European Space Agency.
PowerPoint presentation from a webinar we presented in 2013. Except for the last series of slides on comet ISON which visited us that year, all slides can still be used and provide a lot of information on comets.
Don't hesitate to contact us if you have any questions!