by Aurorasaurus and Friends
Last month we received a letter with some GREAT questions from a class of Manitoba 4th graders! Below we have compiled some answers, along with details and resources for teachers and caregivers to help students dive in further. For some questions, we asked our science and museum colleagues. Scientists know a lot about their special subject area, but one of their other strengths is recognizing what they don’t know and finding out answers from others or from research. Scientists are people who are always asking questions and learning!
How many particles does it take to make the full northern lights?
We aren’t sure exactly, but it’s a LOT!
More to Explore:
Overall, space and the upper atmosphere are not very dense, which means that there are many fewer particles in the air than there are where we live. If you imagine a tiny cube that is 1 cm on each side, there might only be 100 tiny particles in that cube—sometimes less and sometimes more. The air we breathe is sooooooo much more dense.
That said, the Northern Lights are like a glittery work of art, the colors shining with many many tiny points of light. We didn’t know how many particles that might be, because while scientists learn a lot about the subject they study, no one knows everything there is to know about it. When scientists don’t know an answer, they ask questions and do research—just like you did sending us these questions! We asked our friend Dr. Sten Odenwald if he had an idea for how many particles might be shining. He did some math problems and estimated that it might be about 100 trillion trillion! That’s not just trillion, but trillion trillion—a lot of particles!
We know that we can see aurora at night, but we still wonder: is there a certain time that is best?
The hours around midnight are best for seeing nighttime aurora. Aurora chasers, or people who often go looking for aurora, sometimes stay up all night to watch the beautiful Lights! If you want to explore them at your own pace, you can watch them virtually through recordings or live on an aurora camera like this one in Churchill, Manitoba. Since it is nighttime in Finland when it is afternoon in Manitoba, you could even watch aurora live on a Finnish aurora camera during the day.
How many times do they happen in one month?
Auroras are happening all the time, day and night, but beyond that, it depends! There are a lot of things that have to go just right to get an aurora. And just because an aurora is happening doesn’t mean we can always see it—a whole bunch of other things have to go just right for it to be visible to our eyes, too. For example, you have to be in the right location, and because auroras happen above the clouds, you need a clear sky.
More to Explore:
Some people have jobs as space weather forecasters. They learn about the Sun and space science, study data from satellites, and look out for things like auroras. Would you like to become a space weather forecaster someday?
What do you feel like when you see the northern lights? What is the first place that you saw them?
Dr. Liz talked about her aurora experience with Quanta Magazine—you can watch her interview here.
Laura: The first time I ever saw the Northern Lights was in Iceland three Octobers ago. Seeing them in person is not always the same as seeing them in a photo, because cameras are better at seeing in the dark than our eyes are.
The Lights I saw were pale green and slow. They rippled and waved like a ribbon in a swimming pool. They made me feel quiet and peaceful. They reminded me that I am a small creature on a blue marble in a vast universe, and the world is huge and beautiful even when I am having a bad day. Remembering the Lights makes me feel better when I am stressed out, and it always makes me feel calm and happy. The next few times I saw the aurora it looked like a misty grey cloud, but it was see-through like the smoke from a birthday candle and I could look at the stars through it. It wasn’t bright or colorful, but it was graceful, mysterious, and beautiful.
Dr. Liz and Laura are just visitors to the aurora. Many groups of people have had deep knowledge of the Northern and Southern Lights throughout history. For example, you can find out more about Iñupiaq cultural knowledge about the Northern Lights with vocabulary, stories, and dance at the University of Alaska Museum of the North website.
Is the temperature of the aurora different for the different colours? What colour is more hot or more cold?
It’s a little more complicated than hot or cold. When we say something is “hot,” a lot of times we mean that it feels hot when we touch it. But since there are so few particles that high up in the atmosphere, we wouldn’t be able to feel heat even if we could touch a piece of aurora.
That said, most of the atmosphere is very cold, and most of the particles from space that cause aurora could be called “hot” because they have extra energy and move fast! These particles can be different from one another, but those with more speed and more energy create more light—and that light can also reach deeper into the atmosphere. Because different atoms and molecules in various parts of the atmosphere give off different colors, the different energies and depths can lead to different colors. Most aurora light is green, but a really energetic aurora can have a little purple border at its lower edge that moves really fast!
Are there more colours than green, blue, pink and red?
Aurora colors are made when particles that have gotten a lot of energy from the Earth’s magnetic field bump into atoms and molecules in the upper atmosphere. Instead of saying “whoops excuse me!” the particles give the atoms or molecules some of their energy. The atom or molecule can’t hang onto the energy for very long, so it then gives off the energy as light. Different atoms and molecules make different colors of light. Oxygen makes red and green, and nitrogen makes pink and blue.
Sometimes the aurora can look like it has other colors because of the way that our eyes interpret colors mixing. Colors of light mix differently than colors of paint. While red and green paint might be a great way to make brown paint, red and green light make yellow light. Because of this, people sometimes see colors like yellow or cyan in aurora.
There are also aurora-like lights that take other colors. One was brought to the attention of scientists in 2016 by Canadian aurora chasers, who named it STEVE (it now stands for Strong Thermal Emission Velocity Enhancement.) STEVE looks grey to our eyes, but in photographs is purplish-mauve with a bright green pattern beneath it that they call a “picket fence.” Scientists and citizen scientists are working together to figure out why STEVE has such unusual colors.
We also wonder how big they can be, and how far they can go!
Aurora can be thousands of kilometers long!
More to Explore:
How high up an aurora is can affect far away you can see it. Aurora forms between 100 to more than 500 kilometers (60 miles to more than 300 miles) above Earth. To give you an idea of what that means, 500 kilometers (300 miles) is roughly the altitude of the International Space Station. The higher the aurora, the farther away it can be seen from the ground. Usually they occur at high latitudes around Earth’s poles, but the stronger the solar storm causing the aurora, the further toward the Earth’s equator they can occur.
How long can they stay in the sky?
On an active night, auroras can be seen from sundown to sunup, but usually cycle through peaks of active dancing every 3 hours or so. Whether moving slowly or quickly, the Northern and Southern Lights are magnificent to watch.
Can you actually see them from space?
You can and they look amazing! Satellites circling the planet take measurements, but astronauts on the International Space Station also love taking aurora pictures and videos. Here you can see a time lapse of photographs taken by astronaut Paolo Nespoli:
Do the aurora damage the atmosphere?
No, the aurora is a natural process that affects the atmosphere but doesn’t hurt it.
More to Explore:
One of the things that makes this possible is that the Earth is shielded by a protective magnetic field made deep in the planet’s core. If we didn’t have a magnetic field, the aurora might damage our atmosphere. For example, Mars lost its magnetic field, so eventually it also lost its atmosphere through some of the processes that make auroras. Earth is different from Mars, though. Our planet’s core is very active, so our magnetic field will be strong for many thousands of years to come!
Why is the magnetic field weaker at the poles?
Like a bar dipole magnet, the Earth’s magnetic field is stronger at the poles. It gets weaker as it goes out into space, and at the equator. The field for this kind of magnet takes a very distinctive shape, as you can see below when bits of iron are sprinkled over a dipole magnet.
Click here for a teacher workshop from the Burlington, MA Science Center on using magnets in the classroom.
Remote Grade 4 Learners, thank you again for asking all these questions! The most important things you can do to think like a scientist are ask questions and figure out how to look for answers, and you did just that! Last year we put together a blog post of recommended ways for students to explore the aurora remotely. We hope you enjoy finding out more about—and hopefully experiencing—the beautiful Lights!
Dr. Liz and Laura