The same old moon has been hanging around up there for at least 4.46 billion years, according to the latest science. What’s so special about it now?
What’s special this week is that the moon will reach full phase Thursday, appearing perfectly round in the sky, while simultaneously veering as close to our eyeballs as it ever gets. That will makes it appear bigger (a little) and brighter (weather permitting) than usual, and a great object of wonder while it lasts — which isn’t long.
In recent decades, astronomers and science educators have started calling the moon a “supermoon” when it’s both full and at its closest orbital point to Earth. You can judge for yourself just how super when the moon rises in the east-northeast at 6:21 p.m. Thursday (right around dusk) looking exceptionally orange and swollen.
“The orange color of a moon near the horizon is a true physical effect,” said Jim Todd, space science educator at the Oregon Museum of Science and Industry.
When we look toward the horizon, we’re actually looking through a greater thickness of Earth’s atmosphere than when looking up, Todd said. The atmosphere scatters blue light, making the sky look blue, but it lets red pass through.
“Therefore a moon near the horizon takes on a yellow, orange or reddish hue,” Todd said.
And a moon that’s closer to our eyes than usual will seem positively pregnant with color. As the moon keeps rising above the horizon, it will gradually shed that color and wind up the silver-white orb we’re used to — but larger.
How much larger? A supermoon can exceed the size of your average-sized moon by as much as 8 percent and exceed the brightness by 16 percent, Todd said, making it a great occasion to get out the binoculars, or just your sense of awe.
“The Oct. 17 supermoon will be the closest, biggest and brightest full supermoon of 2024,” Todd said.
Supermoons are not rare, happening three or four times per year, and they have a simple explanation. The moon’s orbit around the Earth is not round but elliptical, with its closest point (the perigee) about 31,000 miles closer to us than its farthest point (the apogee).
By the way, the recently popular term “supermoon” sure represents some super-effective moon marketing, as it was coined just a few decades ago by astrologers, not astronomers.
“The scientific term for the phenomenon is ‘perigee moon,’ ” Todd said.
Awesome auroras
If you do spend time looking up this season, you might also try for a glimpse of the colorful auroras that have been sweeping North American skies on and off this year.
You probably won’t see them while the moon is big and bright — because that washes out other lights in the sky — but astronomers say it may be worth keeping an eye on the sky when it’s really dark up there. With a little luck — and an eye on space-weather predictions — you might just catch undulating curtains of green, purple and red lights.
That’s because the sun is at the maximum of its 11-year sunspot cycle right now. When sunspots get busy, so do other dramatic sun phenomena — including solar flares (brief eruptions of radiation) and coronal mass ejections (cosmically huge explosions of energy, magnetism and plasma).
When all that charged-up solar stuff hits our atmosphere, it can spark those astonishing lights in the sky. Usually those are most visible at the north and south poles, but this year has been unusual with lots of sun activity leading to visible auroras at much lower latitudes.
Scientists expect the unusually good aurora conditions to continue for the foreseeable future.
“We are clearly at solar maximum, when the sun has the most sunspots, flares and coronal mass ejections. This solar max will continue until mid-2025,” Todd said. “A very active sun (is) expected in the coming several years.”
Later at night, and into the morning, is usually best for catching auroras, Todd said. Move away from city lights and look to the north. Auroras can last for minutes or hours.
“Sometimes this happens around 10 p.m. then repeats a couple hours later,” he said. “Or we get a modest coronal display around 11 p.m. or midnight, only to see the entire sky ‘break open’ at 2 a.m.”
While auroras are hard to predict with certainty, the aurora dashboard at the National Oceanic and Atmospheric Administration’s Space Weather Prediction Center can help you stay ahead of them. Aurora predictions can change every few hours, Todd said.
