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Alex’s Space

The astronomy blog of astrophysicist Alex Filippenko.

AnnularEclipse

Annular Solar Eclipse – Oct. 14, 2023

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A partial solar eclipse can be fun to watch, though it’s not even *close* to being as spectacular as a total solar eclipse — and I hope all of you travel to the path of totality to see the total solar eclipse on April 8, 2024, in Mexico or the USA. (More about that later…)

We are fortunate to have a chance to see a partial solar eclipse from all of North America and most of South America on Saturday, October 14, 2023. Indeed, in the USA, from a relatively narrow path, an “annular eclipse” will be visible. This occurs when the the Moon is farther from Earth than average in its elliptical orbit, so it looks too small to fully cover the Sun, which thus appears as an annulus (“ring of fire”) at mid-eclipse. No corona will be visible, unlike the case in a total solar eclipse, so it’s not as spectacular, but still fun to view. (Some articles in the media are making a big deal out of the Oct. 14 event, claiming it’s a total eclipse or as good as a total eclipse — it’s *not*!) A photo is attached here.

The path of annularity is shown at https://www.timeanddate.com/eclipse/map/2023-october-14 , and you can type various cities in the Search box to see whether they are within it (broadly speaking: parts of Texas, New Mexico, Utah, Nevada, and Oregon; small sections of Colorado, Arizona, and California). Other places in the USA will experience a partial eclipse shaped more or less like a “C” — but not the full “ring of fire.”

I encourage you to view the partial eclipse, even if you don’t go to the path of annularity. For example, seen from Berkeley, CA, about 77% of the Sun will be covered. The beginning, middle, and end of the eclipse will be at 8:05 am, 9:19 am, and 10:42 am PDT (respectively) — I got this information by clicking on Berkeley on the map at
https://www.timeanddate.com/eclipse/map/2023-october-14 .

When looking at the Sun, be sure to use a “CE certified” solar filter that blocks 99.999% of the visible light and 100% of the ultraviolet and infrared light. These can be purchased online for a small price (about $1-2 each, depending on how many you buy); for example, go to Amazon.com and type in “solar eclipse glasses CE certified.” For a more durable viewer, you could purchase a small (2″ x 4″, or 4″ x 5″) piece of Shade 14 welder’s glass from a welding supply store; cut a rectangular hole in a sheet of cardboard and tape the glass to it, to make the filter easier to hold and to shield the rest of your face from sunlight (but put on sunscreen, anyway). Also, or instead, make a “pinhole camera” (a pencil-width hole in a sheet of cardboard) and project an image of the Sun onto a shaded surface.

If you’d like to take photographs of the Sun, be sure to use a filter in front of your camera. Also, do *not* look directly at the Sun through the camera viewfinder lens unless you have a filter (though it’s okay to look directly at the LCD display of the Sun without a filter).

Feel free to share all of this information with your family and friends.

Wishing you clear skies,

Alex

Perseid Meteor Shower, Aug 2023

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The annual Perseid meteor shower (arguably the best meteor shower of the year) will peak on the night of August 12/13 (conveniently Sat./Sun.), but the nights of August 10/11, 11/12, 13/14, and 14/15 should reveal some Perseids as well. Unlike last year, when light from the full moon brightened the sky and washed out the dimmer meteors, this year the waning crescent moon will not be a problem — skies will be dark (if you’re away from city lights).

In general, view Perseids after 11 pm local time — or better, after 12 am (indeed, the pre-dawn hours should actually yield the largest hourly rate). Before about 11 pm, few Perseids are visible — though they should be longer streaks than average, skimming through Earth’s atmosphere because the “radiant” from which they appear to come will be closer to the horizon. Also, you don’t have to account for your specific *time zone* — the times I list above are fine *regardless* of where you are (though the northern hemisphere is more favorable than the southern hemisphere, for this particular shower).

The meteor shower occurs because Earth flies through debris from Comet Swift-Tuttle (whose orbital period in a long ellipse is about 130 years), and the little bits of rock and ice (typically the size of a grain of sand or a small pebble) will burn up as they zip through Earth’s upper atmosphere (altitude about 60 miles) at roughly 133,000 miles/hour (37 miles per second).  (“Shooting stars” or  “falling stars” are not stars at all!) Only very rarely do fragments reach the ground.

If you wish to view the meteor shower, it’s best do so for at least half an hour (but an hour or longer is better). Try to get as far away from city lights as possible. The Perseids are known for having many bright and fast meteors that should be visible even in a somewhat light-polluted sky, though you’ll see many more from a darker location. *NO* binoculars or telescopes are needed; just look at the sky with your unaided eyes after getting dark-adapted (this can take up to 15 minutes). Choose a wide-open sky, without buildings or trees in the way. Dress warmly, and pack a hot beverage if you want to. Bug spray might be useful, too, depending on where you are. You should lie down on a mattress, sleeping bag, or reclining lawn/deck chair for greater comfort, if you wish.

Looking anywhere in the sky is fine, but straight up often has the darkest sky. Views to the northeast should provide the most meteors, though their streaks will be shorter than if you look elsewhere. If you have clear and dark skies, you might see 20-40 meteors per hour. (The media often report 100 per hour, but that’s from the darkest locations, with a completely clear and unobstructed sky, at the shower’s peak intensity.)

There are many useful references with additional information and viewing tips, etc.; type “Perseid meteor shower 2023” in your favorite search engine. See, for example, https://www.space.com/perseid-meteor-shower-how-to-see-august-2023 .

Wishing you clear skies,

Alex

Total-lunar-eclipse-map-110822

Total Lunar Eclipse, Nov 7-8

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Early Tuesday morning, November 8 (i.e., Monday night, November 7), there will be an “Election Day” total lunar eclipse (when the Moon goes into Earth’s shadow) visible from North America. Weather permitting, everyone on Earth’s dark (night) side will be able to see it. No optical aid is needed — just use your eyes (though the view through binoculars should be interesting as well). Here’s some useful information; more details can be found at the end of the message.

We will be on Standard Time by Monday (switching from Daylight Time this Saturday night, Nov. 5). Unlike the case in a total *solar* eclipse, the lunar eclipse will occur simultaneously from any location where it is visible. However, you have to adjust for different time zones. Here are the relevant times (all are Tuesday early morning — that is, Mon. night after midnight):

Partial eclipse begins: 1:09 am PST,
                        2:09 am MST,
                        3:09 am CST,
                        4:09 am EST.

Total eclipse begins:   2:16 am PST,
                        3:16 am MST,
                        4:16 am CST,
                        5:16 am EST.

Total eclipse ends:     3:42 am PST,
                        4:42 am MST,
                        5:42 am CST,
                        6:42 am EST.

Partial eclipse ends:   4:49 am PST,
                        5:49 am MST,
                        6:49 am CST,
                        7:49 am EST.

(Subtract 2 hours from the above times, if in Hawaii.)

The time of sunrise (and thus moonset, since the full Moon will be opposite the Sun in the sky) depends on where you are in your time zone and also on your latitude — but *roughly* 6:40 am for much of the USA. So, from the eastern USA, the *total* eclipse ends around the time of sunrise, in a very bright sky. The rest of the USA can watch the entire total eclipse in dark skies. Over most of the USA, Mexico, and Canada, the Moon will be high in the sky throughout the eclipse (especially during the first partial phases and totality). However, as seen from the east coast, you’ll need a relatively low, clear western horizon.

The eclipse will also be visible from Australia, New Zealand, Siberia, and much of Asia, though it will be on Tue. night with the Moon in the east (not Tue. morning with the Moon in the west, as in N. America). See the attached map, courtesy Dominic Ford from in-the-sky.org . You can also consult the excellent website https://www.timeanddate.com/eclipse/lunar/2022-november-8 for a detailed map and to see whether the eclipse will be visible from a specific location (put your location in the “Eclipse Lookup” box on the right-hand side of the web page). Another good website is
https://earthsky.org/astronomy-essentials/total-lunar-eclipse-nov8-2022/ .

Totality will last about 1 hour 26 minutes, a relatively long total lunar eclipse (because part of the Moon will pass near the center of Earth’s shadow); if you include the partial phases, it lasts 3 hours 40 minutes. In case of clouds, rain, or snow, don’t give up hope (unless the forecast is truly hopeless)! The long duration of the eclipse means that you might occasionally get a good view of the Moon through a break in the clouds.

Wishing you clear skies during the night of November 7/8, 2022,

Alex

Perseid Meteor Shower & Supermoon This Week (Aug 8-14, 2022)

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The annual Perseid meteor shower (arguably the best meteor shower of the year) will peak on the night of August 11/12 (Thur./Fri.), but the nights of August 8/9, 9/10, 10/11, 12/13, and 13/14 should reveal some Perseids as well. The big problem with this year’s shower is that it coincides with the full moon on August 11, which will brighten the sky and wash out the dimmer meteors — indeed, a “supermoon” (when the Moon is near is closest point to Earth in its elliptical orbit, and thus will appear about 5% larger and 10% brighter than a typical full moon). Given these circumstances, your best views of the Perseids might actually occur in the pre-dawn skies of Tuesday, August 9, after the Moon has set — there will be about an hour of dark skies. [If you’re up during the predawn hours, you’ll also see brilliant Venus shining in the east (the so-called “Morning Star” — though it’s not a star, of course).]

In general, view them after 11 pm local time — or better, after 12 am (indeed, the pre-dawn hours should actually yield the largest hourly rate). [Before about 11 pm, few Perseids are visible (though they should be longer streaks than average, skimming through Earth’s atmosphere because the “radiant” from which they appear to come will be closer to the horizon).] Also, you don’t have to account for your specific *time zone* — the times I list above are fine *regardless* of where you are (though the northern hemisphere is more favorable than the southern hemisphere, for this shower).

The meteor shower occurs because Earth flies through debris from Comet Swift-Tuttle, and the little bits of rock and ice will burn up as they zip through Earth’s upper atmosphere (altitude about 60 miles) at roughly 130,000 miles/hour.  (“Shooting stars” or “falling stars” are not stars at all, of course!)

If you wish to view the meteor shower (despite the bright moonlight — though some of you will doubtless want to gaze at the “supermoon”), it’s best do so for at least half an hour (but an hour or longer is better). Try to get as far away from city lights as possible. The Perseids are known for having many bright and fast meteors that should be visible even in a somewhat light-polluted sky, though you’ll see many more from a darker location. *NO* binoculars or telescopes are needed; just look at the sky with your unaided eyes after getting dark-adapted (this can take up to 15 minutes). Choose a wide-open sky, without buildings or trees in the way. Dress warmly, and pack a hot beverage if you want to. Bug spray might be useful, too, depending on where you are. You should lie down on a mattress, sleeping bag, or reclining lawn chair for greater comfort, if you wish.

Looking anywhere in the sky is fine, as long as you’re not looking in the vicinity of the bright Moon. Views to the northeast should provide the most meteors, though their streaks will be shorter than if you look elsewhere. If possible, put yourself in a “moon shadow” — the shadow of a building or trees cast by the Moon — and look toward the unobstructed part of the sky (the night will appear darker). If you have clear skies, you might see 4-8 meteors per hour (yes, a poor showing this year, given the bright moonlight). But let me quote from the earthsky.org website below:

“Not every meteor shower is a winner. Sometimes, you come away having seen only one meteor. But consider this. If that one meteor is a pretty one… or a colorful one… or it takes a slow path across a starry night sky… if you enjoyed being outside, bathing in the moonlight, smelling the night air, chatting with a friend… you’ll be glad you went outside!”

There are many useful references with additional information and viewing tips, etc.; type “Perseid meteor shower 2022” in your favorite search engine. See, for example,

https://www.space.com/perseid-meteor-shower-2022-webcast
and
https://earthsky.org/astronomy-essentials/meteors-in-moonlight-tips-for-watching/

Wishing you clear skies,

Alex

JWST-SMACS0723-first-image-071122

Supermoon, and spectacular first JWST results

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On the night of Wednesday, July 13, take a look at the full moon, a “supermoon.” Since it is closest to Earth in its elliptical orbit, the moon will look 14% larger and 30% brighter than when it is farthest from Earth (but only 7% larger and 15% brighter than an average full moon) — nice to see, though not the big deal that the press often makes of supermoons (they typically occur a few times per year). The view will be nearly as good on Tuesday and Thursday nights, in case Wednesday isn’t convenient for you or clouds are forecast.

What IS a big deal, though, is the first full-color, ”real science” image from the James Webb Space Telescope (JWST), released on Monday and attached here. It’s truly stunning! Showing a patch of sky just the size of a grain of sand held at arm’s length, it reveals thousands of distant galaxies — gravitationally bound collections of billions of stars (like the Milky Way Galaxy). This is the ”deepest” image of the Universe ever obtained, meaning that it shows the faintest and among the most distant objects ever seen, and it took 12.5 hours of observing at different wavelengths (colors of light) primarily in the infrared (longer wavelengths than visible light — what we often refer to as heat radiation, like from glowing coals).

The image is centered on a massive cluster of galaxies known as SMACS 0723, about 4.6 billion light years away (meaning that the light we are now seeing left those galaxies roughly when Earth and our Solar System was being formed!). It has a giant galaxy in the middle that’s gradually gobbling up other, smaller galaxies in the cluster. Surrounding the cluster are more-distant galaxies, some perhaps more than 13 billion light years away. Many of them are magnified in brightness and distorted into arc shapes because of the ”warping” of space (and time) caused by the massive cluster and predicted by Einstein’s theory of gravity (the general theory of relativity) — an effect called ”gravitational lensing.” The beauty and grandeur of this image are mind-boggling — as is the amount of information in it. (By the way, don’t pay attention to the few objects with six spikes coming out of them — these are stars in our own Milky Way Galaxy, and the spikes are a ”diffraction pattern” produced by the 18 hexagonal segments of JWST’s main mirror. They don’t appear in the images of faint, distant, fuzzy galaxies.)

On Tuesday, July 12, NASA’s main press conference about the first results from JWST will take place, and I encourage you to watch it (or read about the findings online, since you may receive this message too late — apologies). Opening remarks will be at 6:45 am PDT, and four new images will be shown and discussed in succession starting at 7:30 am PDT. There will be a news conference at 9:30 am PDT with more details about the images. Here’s a brief summary.

(1) The Carina Nebula is a cloud of gas and dust 7500 light years away (a light year is 6 million million miles) that can be thought of as a stellar nursery (in which stars have recently been born and are still being born). Many of those stars are very massive and hot. Our own Solar System formed about 4.6 billion years ago from a cloud similar to (but almost certainly much smaller than) this one.

(2) WASP-96b is a planet orbiting another star with a period of only 3.4 days, about half the mass of Jupiter and 1150 light years away from Earth. Its infrared spectrum will be shown, possibly revealing whether the planet has an atmosphere. In future studies of this type, astronomers hope to detect possible biosignatures (such as oxygen and methane) in the atmospheres of exoplanets.

(3) The Southern Ring Nebula is a ”planetary nebula” — gas that was gently ejected by a dying central star and is now glowing by a process similar to fluorescence (the central star is hot, and the UV light that it emits ionizes the surrounding cloud of gas, which then glows). It is about 2000 light years from Earth. Our own Sun will produce a similar object in about 7 billion years — so this is a sneak preview of its future. (“Planetary nebula” is actually a misnomer … the object only looks vaguely like a planet.)

(4) Stephan’s Quintet is a famous group of five galaxies, four of which are at nearly the same distance from Earth (about 290 million light years) and gravitationally interacting with each other in a cosmic dance. (The fifth galaxy is unrelated, and just happens to be along the same line of sight.) There might be a side-by-side comparison of what the Hubble Space Telescope records at visible (optical) wavelengths and what JWST detects in the infrared.

These promise to be amazing images and results! I’m absolutely thrilled that JWST is working correctly. Honestly, a year ago I had serious doubts that the mission would be successful, given the 340+ potential single-point failures. Kudos to NASA and all the people involved in the planning, construction, launch, unfolding, and commissioning of JWST!

I’m looking forward to getting JWST data in the coming year, for two approved studies regarding exploding stars (supernovae) — we are trying to see how much dust they form in the ejected gases. Some of this dust much later becomes incorporated into giant clouds of gas and dust like the Carina Nebula, forming new stars and planetary systems. Exciting stuff, indeed!

With best wishes,

Alex

P.S. Let me also alert you to a press release that my team sent out on Monday, regarding observations of the nearest known example of a star that was shredded, or ”spaghettified,” after approaching too close to a supermassive black hole at the center of a galaxy:
https://news.berkeley.edu/2022/07/11/the-ultimate-fate-of-a-star-shredded-by-a-black-hole/

This study was led by one of my graduate students, Kishore Patra. I’ll provide some more details (via email) later, after we compose and release another press release about a different study we’ve completed… but I want to keep this message focused on the JWST results.

PlanetaryAlignment-6-24-22

Rare Planetary Alignment Visible This Week

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Here is an interesting celestial sight that will be visible in the early morning this week in mid-June 2022.

Five naked-eye planets arc across the sky from east to west in the correct order of increasing distance from the Sun: Mercury (low above the eastern horizon), then very bright Venus, followed by Mars (looks reddish orange), Jupiter (bright), and Saturn. Such a “planetary parade” with all 5 planets visible *simultaneously* last occurred 18 years ago, and I think it won’t happen again until around 2100 (I might be wrong about this, but the configuration is quite rare in any case). To top it off, on the early morning of June 24, the waning crescent Moon will appear between Venus and Mars — representing Earth (since the Moon orbits us) at its proper place in the celestial lineup.

If you want to include Mercury, the best time to view this spectacle will be about 45 minutes before local sunrise: late enough in the night that Mercury will have had a chance to rise higher above the horizon, but not so late that the sky will be too bright because of the approaching sunrise. Binoculars could help you spot Mercury (or, use an App such as Sky Tonight, Star Walk 2, or SkyView). To see Mercury, you’ll need a very low, clear eastern horizon (i.e., no buildings, trees, hills, etc. in the way), but the other planets will be much easier to see in the southeast sky (and south, for Saturn).

This week, Mercury’s apparent separation from the Sun is decreasing, so the sooner you look (e.g., Sunday or Monday, June 19 or 20), the easier it will be to see Mercury — but try to also view the sky 45 minutes before sunrise on June 24, when the crescent Moon will join the arc between Venus and Mars.

I attach two diagrams: one from Sky & Telescope magazine showing the planets among the constellations, the other from timeanddate.com showing a simulated view from New York City at 4:40 am EDT on June 24.

Of course, although these planets *appear* close together in the sky, they are actually separated by up to hundreds of millions of kilometers; Jupiter and Saturn are 5 and 10 times farther from the Sun than Earth is, for example.

Wishing you clear skies,

Alex

LunarEcliplse-5-15-22

Total Lunar Eclipse, May 15-16, 2022

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 On Sunday evening/night, May 15, 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 eastern evening sky, shortly *after* sunset, as seen from the western continental United States and western Canada. It will be high in the sky at various times around the middle of the night in the eastern United States and Canada, Mexico, Central America, and South America. The total eclipse will not be visible from Hawaii, but the Moon will be partially eclipsed at moonrise (which occurs at sunset). In Spain and western Africa, the total eclipse will be visible before moonset in the western morning sky (Monday, May 16), shortly before sunrise. See the attached map, courtesy Dominic Ford from in-the-sky.org. Also, consult the excellent website https://www.timeanddate.com/eclipse/lunar/2022-may-16 for a detailed map and the ability to see whether the eclipse will be visible from a specific location (put your location in the “Eclipse Lookup” box on the right-hand side of the web page).

Totality will last about 1 hour 24 minutes, a relatively long total lunar eclipse (because part of the Moon will pass through the center of Earth’s shadow). 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).

Here are the  relevant times in San Francisco, CA; adjust for your time zone if you will be away from Pacific Daylight Time (PDT). (For example, mid-eclipse will be at 12:11 am EDT on May 16, as viewed from the USA’s east coast that’s Sunday night, but technically Monday early morning.)

Partial eclipse begins:   7:27 pm PDT Sunday, May 15  (below the eastern horizon)
Moonrise:   8:06 pm PDT  (You will need a very clear, low, eastern horizon to see it.)
Total eclipse begins:   8:29 pm PDT
Mid-eclipse:   9:11 pm PDT
Total eclipse ends:   9:53 pm PDT
Partial eclipse ends:   10:55 pm PDT

“Prime time” (total eclipse) will be 8:29-9:53 pm PDT. The Moon will be east, low over the horizon, shortly after it rises; try to avoid obstructions like mountains, buildings, and trees. The farther east you are in the continental United States, the farther above the horizon the Moon will be.

Again, for more information see https://www.timeanddate.com/eclipse/lunar/2022-may-16 .
Another good website is https://earthsky.org/astronomy-essentials/total-lunar-eclipse-may16-2022/ .

Wishing you clear skies during the night of May 15/16, 2022,

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. I expect that on May 15/16, the Moon will look pretty dark (though still orange/red) at mid-eclipse, because it will be deep in Earth’s shadow.

Also, on May 15/16 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 isnearly 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, there are three in 2022. 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.”

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 6:32 pm PDT (before moonrise in the PDT time zone) and ends at 11:50 pm PDT.

CometLeonard-Dec18-2021

Comet Leonard this Weekend, near Venus in Evening Sky

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I’d like to alert you to a good opportunity to see the best comet of 2021 this weekend: Comet Leonard. Feel free to pass this information to your family and friends, if you wish.

A comet is a ” dirty iceball” (or an ” icy dirtball” — depending on the relative amounts of ice and dust) that comes from the deep freeze of the outer Solar System, beyond the orbit of Neptune. It heats up as it gets closer to the Sun, and the ices sublimate, becoming gas. This releases a cloud of dust that becomes visible by reflecting sunlight; the ” coma” of dust surrounds the nucleus, and the tail points roughly away from the Sun. The gas can also glow, and it points directly away from the Sun.

Comet Leonard, the brightest comet of 2021, has now conveniently moved from the morning sky to the evening sky, and will be very close to the brightest planet (Venus) the next few nights, making it easier to find. In clear, dark skies with a low southwest horizon, the comet’s nucleus might be visible to the unaided eye as a faint and fuzzy ”star.” You are much more likely to see it through binoculars; this will reveal the coma and perhaps also the tail. Photographs obtained with a digital camera mounted on a tripod will reveal more of the coma and tail (typical exposure time 4-20 seconds). You can find many excellent photos of the comet online (e.g., https://earthsky.org/astronomy-essentials/comet-leonard-might-become-2021s-brightest-2022/). After passing closest to the Sun on January 3, 2022, the comet will be ejected from our Solar System.

To find Comet Leonard, look to the southwest shortly after sunset in a darkening sky — around 5:20-5:30 pm (local time) would probably be best. It will be a little below Venus (the brightest object in the southwest sky) on the evening of Friday, December 17; see the attached chart (made by Eddie Irizarry using Stellarium software). On Saturday, December 18, it will be a little below and to the left of Venus, and on Sunday, Dec. 19, it will be farther to the left of Venus (and still a little below). Slowly scan that part of the sky while looking through binoculars. You’ll need to have a clear, low southwest horizon, not blocked by trees, hills, buildings, or other obstructions. Beyond Dec. 19, the comet could still be visible (progressively farther to the left of Venus), but it is expected to fade.

Good luck, clear skies, and happy holidays,

Alex

Nearly Total Lunar Eclipse, November 18/19, 2021

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On Thursday night, November 18/19, there will be a *nearly* (97%) 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. With a duration of 3 hours, 28 minutes, it will be the longest *partial* eclipse since the 15th century (in other words, partial lunar eclipses this close to being total are rare!). At mid-eclipse, only a thin sliver of the Moon will not be immersed into Earth’s dark shadow. No optical aid isneeded — just use your eyes (though the view through binoculars should be interesting as well).

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.
Here’s a USA timetable for the eclipse. If you have time to watch only part of it, the best half-hour would be starting about 15 minutes before mid-eclipse.

Eclipse starts: 11:18 pm PST (12:18 am MST, 1:18 am CST, 2:18 am EST)
Mid-eclipse: 1:03 am PST (2:03 am MST, 3:03 am CST, 4:03 am EST)
Eclipse ends: 2:47 am PST (3:47 am MST. 4:47 am CST, 5:47 am EST)

The entire eclipse will be visible throughout all of North America and Hawaii, and much of the first half can be seen from most of South America. The end of the eclipse will be visible in the early evening of Friday, November 19 from New Zealand, eastern Australia, eastern Indonesia, and eastern Asia. See the excellent website https://www.timeanddate.com/eclipse/lunar/2021-november-19 for a detailed map and the ability to determine whether the eclipse will be visible from a specific location.

Wishing you clear skies during the night of Nov. 18/19,

Alex

P.S. Note that there will be a total solar eclipse visible from a path across Antarctica on December 4, 2021. I will experience it from a ship near the South Orkney Islands — my 18th total solar eclipse! Unfortunately, even the partial phases won’t be visible from land elsewhere. If interested, more information can be found here:https://www.timeanddate.com/eclipse/solar/2021-december-4 .
 
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Additional details about the lunar eclipse:

The parts of the Moon that are in Earth’s shadow during a lunar eclipse don’t appear completely dark 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 near mid-eclipse, the Moon’s color should appear 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. Given this reddish orange color, a fully eclipsed moon is sometimes called a “Blood Moon,” though in this particular case the bottom part won’t be eclipsed so it will appear bright.

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 10:02 pm PST and ends at 4:03 am.
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Annular/Partial Solar Eclipse, June 10, 2021

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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

Total Lunar Eclipse, May 26, 2021

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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.

Total Lunar Eclipse (courtesy Richard Spence)

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.

Conjunction of Venus and Jupiter, February 11 (before sunrise), 2021

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I want to let you know of a celestial event that will be visible on the morning of Thursday, Feb. 11, about 20-30 minutes *before* local sunrise: Venus and Jupiter will appear close together in the sky, similar to what was seen in the December evening sky for Jupiter/Saturn (but they won’t be quite as close together).

To see this “conjunction,” find a location with a very clear, *low*, southeast horizon (no buildings, trees, or hills in the way). Better to arrive somewhat earlier than 30 minutes before sunrise and start looking southeast; the planets will be rising. If you arrive too late, closer to sunrise, they will be higher in the sky but not visible because of the sky brightness.

Venus and Jupiter should be visible to the unaided eye, though using binoculars could help you locate them. They will be the brightest “stars” in the sky. (By the way, the planets will appear nearly as close to one another Feb. 9, 10, 12, and 13 as well — this may be useful to know if the weather forecast for Feb. 11 in your area isn’t favorable.)