Bucket-list sky phenomena

Mammatus clouds (photo by John C. Olsen)

Who doesn’t enjoy looking at towering orange cumulus clouds in the late afternoon sun?  Or a brilliant meteor flashing across the sky? Or the Milky Way away from city lights?

Such sights are common in some seasons, but not others. Towering cumulus clouds are frequent in summer, but rare in winter. The Milky Way is prominent every autumn, but absent in the spring. Meteors are far more prevalent from August through December than during the rest of the year.

Yet, other gorgeous sky apparitions can happen anytime and, despite not requiring telescopes, still manage to be rarely observed. Some of these are nearly mythical. So here are my top six sky apparitions that belong on everyone’s bucket list, most of which appear in your own backyard.


6. The Northern Lights

If you live in a big city and refuse to travel, forget this one. But if you’re willing to go to Alaska (join us, some year!) or merely have patience, you’ll see the fabled lights. From here, there’s a good display in all rural locations once a decade or so. You’ll see aurora predictions in the media a day in advance, based on sudden solar storms sending material in our direction. But you’re out of luck if the Moon is nearly full.

5. Cloud iridescence

This is much more easily seen through sunglasses.  Simply look at the white fringes of clouds in the vicinity of the Sun, especially high-altitude clouds. Before too long you’ll observe strange non-spectral colors. Such non-prismatic hues mean colors never seen in a rainbow! We’re talking about an odd brownish yellow-orange, aquamarine, purple, maroon…wow, they can amaze and astound. Such cloud iridescence appears weekly. It’s not rare at all. It’s caused by diffraction: the same process that produces swirly psychedelic colors on oily roadside puddles.

4. The Circumzenithal Arc

More vivid than a rainbow, and featuring the same colors, this brilliant arc appears nearly straight overhead and always takes one’s breath away. It’s invariably oriented like a smile, not a frown like the rainbow exhibits. It appears a few times a month. Simply look nearly straight up, directly above the lowish Sun whenever the sky has thin ice layers or thin cirrus clouds. The CZA best appears when the Sun is between 15 and 27 degrees high: a situation seen this month, after Sunday’s clock change, between 1:30 and 3 p.m.

3. Mammatus clouds

These dramatic bulging clouds hang below storm clouds. If the sunlight angle is low, they can be mind-blowing. They appear a few times a year for those who regularly watch the sky.

2. The Green Flash

The final speck of the red setting Sun sometimes turns vivid emerald-green for a few seconds before it too has set. It’s best-seen when the Sun is vanishing below a true horizon, like at sea or through a jet window. I’ve looked for it at sunset for decades, perhaps 300 times, and seen it about 30 times. If my experience is typical, expect success during ten percent of all sunsets. Don’t expect an actual flash. I did see that once, but normally the green is a quiet metamorphosis that could be missed if you’re not looking carefully.

1. The total solar eclipse

Because it is the most magnificent of all of these, it’s the ultimate bucket-list apparition.  It’s the rarest of these phenoms by far. It appears in your backyard once every 360 years, on average. There’s usually one a year somewhere on Earth, confined to a narrow strip. The next three will happen in Chile in 2019, Chile again in 2020 and Antarctica in 2021. The next one around here will take place on April 8, 2024, visible from Buffalo, Syracuse and Burlington. Our immediate region will then see a partial eclipse: a common phenomenon that cannot be looked at directly and doesn’t make our list.