Pop quiz, hot shot: What’s the closest star to Earth?*
A couple of weeks ago, people across Canada and even as far south as Arkansas in the United States, were treated to a spectacular light show. The night sky became a glowing curtain of colours that stretched across the the black, starlit sky. I, sadly, did not witness this. If you missed it, here is a link to a fantastic time-lapse of the show that astrophotographer Malcolm Park produced (through cloud, no less!):
If you’ve never seen the Northern Lights (aurorae), let me tell you, they’re breathtaking: the sky comes alive, shimmering and moving, in waves of green, red and purple. The first time I saw them was in March 1991. I was out walking my dog, head up, gazing at the stars as usual. But I became increasingly annoyed because there were red clouds blocking my view. But then it hit me: the Northern Lights! I ran home and burst in the door, ecstatically dragging my family outside with me (along the way, I almost killed a dog and a guinea pig, but that’s another story). For months I could see them on a weekly basis, even the faintest ones. It was just incredible. (I won’t discuss the time I dragged my best friend Sonia to a location just north of Toronto — which was deserted back then, but is now full of homes — to show them to her, and she dove through my open car window, skirt and all, because she thought she heard a bear. It was not a bear. But it was hilarious.)
So . . . what do the Northern Lights have to do with the sun? Well, it’s the sun that gives us these stunning lights.
The sun isn’t the smooth yellow (white) disc we think it is. It has six areas: the core (where the thermonuclear reactions occur), the radiative zone and the convective zone, which are in the interior; the visible surface, called the photosphere; the chromosphere; and the outermost region — the corona. The sun produces sunspots in its photosphere. Sunspots are cooler areas on the sun. (The sun’s surface temperature is about 5,000 degrees Celsius. These sunspots are close to about 2,500 degrees Celsius.)
Sunspots have been observed for over a thousand years, but it’s been only recently that scientists have come to understand them better. In 1843, German astronomer Samuel Heinrich discovered that our sun has a sunspot cycle of about 11 years. In the solar minimum, we see virtually no sunspots. In the solar maximum, the sun can be spotted with many of these dark, cooler spots. Sunspots can range in size from quite small to as large as Earth, and they come in groups. They also have magnetic fields. When these magnetic fields become unstable, the sun blasts a solar flare or coronal mass ejection (CME) into space that sends the charged particles along the solar wind towards Earth. When these charged particles interact with our magnetic fields (which is strongest at the north and south poles) it excites the atmosphere and creates these beautiful lights. Usually people who live closest to the poles, in places such as northern Canada, Greenland, Iceland and other nordic countries are the only ones lucky enough to witness the special light show (and of course, those nearest the south pole, primarily Antarctica; their aurorae are called the Southern Lights or the aurora australis). But every so often, we get a huge blast that really excites our atmosphere, giving people much farther south a special treat.
But these geomagnetic storms, as they are called, also have negative effects. We are now a society that depends greatly on technology: power grids control our heat, air conditioning, lighting . . . you name it. But if a particularly strong solar storm were to hit Earth, it could disrupt all of this. In fact, this happened in Quebec in 1989. On March 10, the sun gave off a powerful eruption. The storm hit Earth two days later, and aurorae could be seen as far south as Cuba. This storm was so powerful, it actually created electrical currents under North America. These currents travelled through to Quebec’s power grid. At 2:44 a.m., the entire province of Quebec was plunged into darkness. The blackout lasted for 12 hours, trapping people in elevators, shutting down Montreal’s subway system and closing schools and businesses, as well as Dorval airport. This was March. In Quebec. And it was cold. The blackout lasted for 12 hours.
So sure, geomagnetic storms can be beautiful, but let’s not forget that they can have a negative impact as well, beyond the disruption of power. If a super-flare like the Carrington Event were ever to hit Earth today instead of 1859, most of humanity would be left in the dark.
But on the bright side, at least it’s not a zombie apocalypse.
Here is another Malcolm Park photo, from the Astronomy Picture of the Day (APOD) site:
Age: 4.6 billion years
Composition: 92.1% Hydrogen, 7.8%Helium
Equatorial circumference: 4,370,005.6 km (2,715,395.6 miles) = roughly 110 Earths
Mass: 1,989,100,000,000,000,000,000,000,000,000 kg (4,385,214,857,119,400,000,000,000,000,000 lbs) = 333,060.402 x Earth
Rotation period at equator: 26.8 Earth days
Surface Temperature: 5,500 °C (10,000 °F)
*Answer: The sun