Alex’s Space

On Thursday, June 10, there will be an “annular” eclipse of the Sun visible from parts of Canada, Greenland, and (going over the North Pole!) finally Russia (Siberia). The Moon will be directly between Earth and the Sun, but it won’t completely block the Sun’s bright disk as it does in a total solar eclipse. That’s because the Moon will be more distant from Earth than average in its elliptical orbit, and (this is a smaller effect) Earth will be more distant from the Sun than average in its elliptical orbit, so the Moon will look a little smaller than the Sun. People located in the right places (located along a narrow swath of Earth’s surface) will see the Sun appear as an “annulus” — sometimes referred to as a “ring of fire.” This is a special case of a partial solar eclipse, and it’s nowhere near as fabulous as a *total* solar eclipse, but it’s fun to view nonetheless. See the attached photo of a previous annular solar eclipse.

Over a much broader part of Earth’s surface, a more “normal” partial solar eclipse will occur. For people in the northeastern United States, the partial eclipse will already be in progress at sunrise, ending not long thereafter. Try to see it, if you can. (However, you’ll still need to put a *total* solar eclipse on your “bucket list.” There will be one in the United States on April 8, 2024 — I’ll write more about this later, but mark the date on your calendars now!)

To view a partial solar eclipse, you MUST have the right eye protection. For more information, see https://eclipse.aas.org/eye-safety and also https://eclipse.aas.org/eye-safety/iso-certification. Look through green Shade 14 welder’s glass, or through special eclipse glasses (“CE certified”) sold by a reputable vendor such as Rainbow Symphony; see https://eclipse.aas.org/resources/solar-filters for an extensive list of options. The filter *must* block 99.999% of the Sun’s visible light and 100% of the Sun’s ultraviolet and infrared light, or your eyes could be very seriously damaged (even blindness is possible). Regular sunglasses (even polarized ones) are NOT suitable at all, and neither is smoked glass or an exposed/developed film negative. If you use binoculars or a telescope, a proper filter *must* be placed at the front end of the device (closest to the Sun). Please be VERY careful when observing the Sun!

You can also use the pinhole camera technique, which is much safer: punch a hole (roughly the width of a pencil is a reasonable size) in a sheet of cardboard and look at the image of the Sun projected onto a shaded region below the cardboard. If you use a collander or other object having lots of holes (such as a straw hat), you’ll get many images of the partially eclipsed Sun. Holes between the leaves of a tree can act like pinhole cameras and produce many Sun images on the ground.

For more information about this solar eclipse, see the really excellent and thorough website https://www.greatamericaneclipse.com/2021-june-10. You can also check out https://www.timeanddate.com/eclipse/solar/2021-june-10 ; it provides a detailed map, and you can determine whether the eclipse will be visible from your specific location: https://www.timeanddate.com/eclipse/map/2021-june-10. Another useful website is https://earthsky.org/tonight/annular-solar-eclipse-on-june-10-2021/.

I attach a detailed map made by Michael Zeiler, available at https://www.greatamericaneclipse.com/2021-june-10. It shows the fraction of the Sun’s disk covered by the Moon at maximum eclipse and the Sun’s orientation relative to the horizon, as seen from southeastern Canada and the eastern/northeastern U.S. Views of the Sun rising above the horizon should be very pretty, looking like “horns” or a “shark fin” depending on your specific location. There will be outstanding opportunities for photography!

Note that this solar eclipse follows just 2 weeks after the May 26, 2021 total lunar eclipse. If you didn’t see it, I encourage you to view the recording obtained at the Chabot Space and Science Center (in the hills of Oakland, CA): https://www.youtube.com/watch?v=4bhus6UBPcg. Be aware that the video is 4 hours long, and the first 15 minutes is just the “Starting Soon” slide. You don’t start noticing any significant change in the Moon’s appearance until about 45 minutes into the video. If you wish, you can fast-forward about 2 hours 50 minutes, to the time when totality was taking place (4:11-4:26 am PDT).

Happy (and safe) viewing, if you’re lucky enough to be in the right part of the world!

Alex

On Wednesday, May 26, there will be a total lunar eclipse (when the Moon goes into Earth’s shadow). Weather permitting, everyone on Earth’s dark (night) side will be able to see it. The eclipse will occur in the early morning, shortly before sunrise, as seen from the western continental United States, western Canada, southern Alaska, Mexico, and the southern part of South America. It will occur in the middle of the night as seen from Hawaii. [Across the Pacific Ocean, it will be visible on the evening of Wednesday, May 26, in New Zealand, Australia, Indonesia, Japan, eastern China, and eastern Russia.] See the excellent website https://www.timeanddate.com/eclipse/lunar/2021-may-26 for a detailed map and the ability to see whether the eclipse will be visible from a specific location.

Totality will last about 15 minutes, a relatively short total lunar eclipse. Unlike the case in a total solar eclipse, the lunar eclipse will occur at the same time (after adjusting
for time zones) from any location where it is visible. No optical aid is needed — just use your eyes (though the view through binoculars should be interesting as well). A photo of a total lunar eclipse (January 20, 2019, taken by Richard Spence) is shown above, and you can find many more on the internet.

Here are the relevant times in California; adjust for your time zone if you will be away from Pacific Daylight Time (PDT). (For example, mid-eclipse will be at 1:19 am Hawaii Standard Time on Wednesday morning, May 26 — that’s late on Tuesday night, of course.)

Partial eclipse begins: 2:45 am PDT Wednesday, May 26
Total eclipse begins: 4:11 am PDT
Mid-eclipse: 4:19 am PDT
Total eclipse ends: 4:26 am PDT
Partial eclipse ends: 5:52 am PDT

“Prime time” (total eclipse) will be 4:11-4:26 am PDT. The Moon will be west, low over the horizon, shortly before it sets; try to avoid obstructions like mountains, buildings, and trees. The farther east you are in the continental United States, the closer to the horizon the Moon will be, and the closer to sunrise the eclipse will occur; Denver, for example, is near the eastern boundary, though at least a partial lunar eclipse will be visible throughout most of the continental United States. Viewed from southeast Asia, the Moon will appear low over the eastern horizon, shortly after it rises.

Again, for more information see https://www.timeanddate.com/eclipse/lunar/2021-may-26 . Also, let me alert you to a handy astronomy/space calendar from the New York Times that you can download right to your Google or iOS calendars. Here’s the 2021 version: https://www.nytimes.com/interactive/2021/science/astronomy-space-calendar.html .

Note that there will be a partial solar eclipse (“annular” in some small parts of the world, so the Sun will look like a ring) on June 10, visible over much of the continental United States. I’ll try to provide more information later, but you can find many details here: https://www.timeanddate.com/eclipse/map/2021-june-10 .

Wishing you clear skies during the night of May 25/26,

Alex

Additional details:

The Moon doesn’t appear completely dark during a total lunar eclipse because some sunlight goes through Earth’s atmosphere and is bent (refracted) toward the Moon, and then it bounces off the Moon back toward us. But the Moon’s color generally appears some shade of yellow, orange, or even red because the light that reaches it has been filtered by Earth’s atmosphere, preferentially getting rid of the violet, blue, and green colors — just as in the case of the setting or rising Sun, which looks some shade of yellow, orange, or red, depending on the amount of particular matter (such as smoke) in the atmosphere.

Also, this time the full moon will be a little closer to Earth than average in its elliptical orbit and therefore look a bit bigger — a “Super Moon” (or “Supermoon”). But in my opinion, this is often exaggerated by the press; though the Moon is nearly at its closest to Earth in its elliptical orbit, even the best Super Moon looks only slightly bigger (6-7%) and brighter (12-14%) than an average full moon. Also, “Super Moons” are pretty common; in fact, this will actually be the second in a series of three consecutive “Super Moons” in 2021. Since the totally eclipse Moon can appear reddish orange, it is sometimes called a “Blood Moon,” so this particular eclipse will be a “Super Blood Moon.”

Given that the Moon will be passing through the top part of Earth’s shadow, I predict that at the time of mid-totality, the top (north) part of the Moon will appear substantially
brighter and more yellow/orange than the bottom (south) part of the Moon (darker; orange/red).

Note that during the partial phases, Earth’s shadow on the Moon looks distinctly curved. This is always the case during a lunar eclipse, and it was one of the many pieces
of evidence that the ancients used to conclude Earth is round, not flat.

In the above list of times, I didn’t include the “penumbral” eclipse, when Earth blocks only part of the Sun as seen from the Moon; the full moon will look slightly fainter during the penumbral eclipse, but this effect is hard to notice and isn’t very interesting. It begins at 1:48 am PDT and ends at 6:50 am PDT, after the Moon has already set.