Total Solar Eclipses and the Great American Eclipse on April 8, 2024

A total solar eclipse is one of the most amazing visual and sensory experiences you can find in nature, a combination of astronomical alignments and local phenomena that combine to dazzle us humans when we witness this spectacle. I caught the 'solar eclipse bug' decades ago and have traveled far and wide over the past years to be in the shadow of the moon many times. I find it to be a profoundly moving experience, and I am heading to the next one in April 2024 that will be visible across a large swath of North America. During a total solar eclipse, there are three broad categories of the experience. 

In no particular order: 

The Heavens Above: an eclipse happens when the moon, sun and earth are perfectly aligned and the penumbral (dark) shadow of the moon traverses the earth's surface. During the partial phases, a little more than an hour long, the sky dims very gradually, but in the last 10 minutes before totality the change in the sky is dramatic, going from daytime blue to sunset blue. Planets are suddenly visible and a few bright stars as well. And then, when the moon fully covers the sun's disk, the image in the sky is stunning. For a few brief minutes you can view the eclipse without eye protection and see the outer atmosphere of the sun, the solar corona. If you have a telescope or binoculars, you can see the solar prominences, beautiful red flares that flow out from the solar surface. The images here were taken by amateur astronomers near my viewing site in Australia. 

The Earth Below: as the partial phases progress, the nature of the light changes as the light source, the sun, changes from a round ball to a crescent to an ever-diminishing point of light. The shadows on the ground develop sharp edges and the light of the sun filtering through trees takes on a crescent shape. The air cools noticeably, and the wildlife starts to react. I have been in many an eclipse where flocks of birds set flight just before or after totality. The rapid cooling of the air often leads to a light breeze. And the horizon become brighter than the sky above you as the shadow of the moon envelops you and everything around you. 

The Humans Around You: I enjoy going to eclipses where there are other people around me. Sometimes I lead a group, or other times I take part in a tour. Either way, I find it remarkable how the eclipse affects us as human beings, whether someone has seen many eclipses or is witnessing this for the first time. The buildup is so gradual and slow that you could barely notice unless you have a telescope with a solar filter (which I always have with me). But as the final minutes tick down to totality, there is a noticeable buzz in the people around you and at the last moment as the diamond ring effect takes place, there is an outcry from those around you ... a kind of group exhale combined with a primal scream ... because this incredible visual image appears magically in the sky. I enjoy the energy of this shared experience. 

There are so many aspects of eclipses to learn about, I cannot cover all of this in one blog post. So here are some helpful links for the curious reader.  

Third party posts: 

NASA Eclipse Website with focus on April 2024.

Great American Eclipse website with lots of resources and maps for April 2024. 

My own posts: 

Solar Eclipses and the Saros Cycle - a previous blog post focused on the celestial dynamics that underlie eclipses. 

2006 Eclipse in Turkey - a short blog post about my experience in Turkey in 2006.

2023 Eclipse in Australia - a short blog post about my experience in Australia in 2023.

Images courtesy of Aditya Madhavan. 

Total Solar Eclipse in Australia: watch live

As an Eclipse Chaser, I often travel long and far to see a total solar eclipse. Today is no exception, as I find myself in Western Australia to witness the Ningaloo Solar Eclipse from Exmouth. There are several live streams: 

NASA

Australian Geographic 

Happy viewing. I'll post comments later. 

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Here is my report from later on 20 April: it was an impressive eclipse, with a very sharply defined corona. The prominences were like I have never seen before, with one very extended prominence and one beautifully curved prominence that had a broken filament. The sky was crystal clear and the spectators at my site here in Exmouth were quite excited by the whole thing. 

I have added two photos from the photographers next to me. The one above shows the Diamond Ring effect, and the one below totality with the solar corona. 

Solar Eclipses and the Saros Cycle

Moon's Ascending and Descending Nodes

Eclipses are the outcome of a chance series of alignments between three bodies: the Sun, Moon and Earth. Orbital mechanics and the laws of Kepler ensure that these bodies circle each other in a beautiful series of harmonious ellipses, near perfect circles each with their own periodicity and in the case of the Moon, with its own orbital inclination. The interplay between the various cycles of the Moon orbiting the Earth, the Earth orbiting the Sun, and the Moon’s gradually changing orbital inclination lead to patterns that repeat over short, medium and long periods of time as these three bodies align.

Eclipses of Saros 145

One of the overall epicycles of these orbits is called the Saros Cycle. At any given time there are many Saros Cycles occurring coincidentally and the Great Eclipse on August 21^st is a member of Saros 145. What does this mean? A Saros is an 18 year cycle in which three of the Moon-Earth cycles repeat nearly perfectly, the end effect of which is to create a near duplicate eclipse in this long period of time. The eclipse across Europe in August 1999 was a member of Saros 145, the most recent one of that Saros series until this coming August. In the intervening 6585 days there have been many other lunar and solar eclipses, but none with the exact geometry and timing that we saw in August 1999. So if you get a chance to see the eclipse in August 2017, know that it is virtually identical to the one experienced by observers in Europe 18 years ago. I was in Hungary for the 1999 eclipse and look forward to seeing the Great American Eclipse this summer, a chance to see an old friend again, a pleasant 2 minutes and 40 seconds where I am aligned with the Sun, Moon and Earth but not only just aligned, but in the specific geometrical arrangement that I witnessed 18 years prior. 

For a somewhat deeper look into the Saros Cycle, here are the basic three motions. (1) The Moon’s orbit around the Earth combined with the Earth’s orbit around the Sun leads to the well-known phases of the Moon that repeat every 29.5 days, the time from New Moon to New Moon, and we call that the Synodic Month. (2) At the same time, the Moon’s elliptical orbit around the Earth means we have a close approach and a more distant approach every month and the time between two successive closest approaches (Perigee) is 27.55 days, a time period that is called the Anomalistic (Perigee) Month. (3) Finally the Moon orbits the Earth on a slightly inclined orbit so at times the Moon is ascending from below to above the plane of the solar system (‘ascending node’) or descending from above to below the ecliptic plane (‘descending node’). The time period from one ascending node to the next is called a Draconic Month which is 27.21 days. If you combine all three of these time periods, they nearly perfectly repeat after 18 years and 10 or 11 days (depending on the number of Leap Years between the two years in question), constituting the repetition period of consecutive eclipses in a Saros Series. Saros 145 eclipses took place on August 11th 1999 and on August 21st 2017. And of course the next Saros 145 eclipse will arrive on September 2nd 2035, right on schedule!

For more on this subject, Wikipedia has an excellent write up. 

Images courtesy NASA. 

The Spring 2015 Eclipse Season

We are in an Eclipse Season, a period of time approximately every six months when we experience 2 or 3 eclipses in a short period of time. Just a few days ago Europe experienced a Total Solar Eclipse far in the north of the continent, and by coincidence I was in the region on a business trip and experienced a partial eclipse. Being there reignited the love I have for eclipses and now that I am back in San Francisco, I am counting down the days to the next Total Lunar Eclipse on the early morning hours of April 4th. This is the third in a 'Tetrad of Total Lunar Eclipses' that started in 2014 and conclude later this year.

Lunar Eclipse April 4

The upcoming Lunar Eclipse will be visible from the west coast of the United States in the pre-dawn hours, starting at 3:17 AM and reaching totality from 4:58 until 5:03 AM. This should be a unique eclipse due to the very short duration of totality. As the Moon will barely be fully engulfed in the umbral shadow of Earth, the color will likely be quite unusual. The past few Lunar Eclipses have produced 'blood red' Moons, but I expect this one will be a more shallow shading with more light on the limb of the Moon and not the dark or ruddy color that is often seen during totality. I look forward to a high-speed Lunar Eclipse. In many ways it will be reminiscent of a Total Solar Eclipse, in that we will only experience a tantalizing short few minutes of totality - something I am quite used to when it comes to Solar Eclipses, but not used to for Lunar.

The San Francisco Amateur Astronomers are planning a public viewing event at Ocean Beach in San Francisco on April 4th. Come join us for a fun time viewing this unique eclipse at the beach.

Image courtesy Fred Espenak.

Why You Should See An Eclipse

Shadows during an eclipse

I gave a talk recently at an event in San Francisco called Ignite, a fun evening of short, fast-paced talks on a wide variety of subjects. Click here to watch my 5 minute video on the subject of eclipses. I think you'll be inspired (and if not, then it's only 5 minutes :-)

Preview of the Aug 21, 2017 Total Solar Eclipse

August 2017 Eclipse Path

I am a fan of total solar eclipses, and although it is a long time in the future, I want to provide some resources for those who want to learn about an incredible eclipse that will cross the entire North American continent in August of 2017. This summertime spectacle tracks from the Oregon coast to South Carolina and affords good views for up to 2 minutes and 40 seconds of breathtaking totality. The summer climate is mostly reliable along the eclipse track and the interstate freeway system ensures that local climate problems will be manageable should there be inclement weather in spots along the eclipse path. Here are some of the best online resources for planning to see the eclipse that I have found so far:

NASA's Eclipse Resource Center
Eclipse2017.org
Eclipse Chasers

Each of these sites offer tips and suggestions for getting to the right place and being ready for seeing an eclipse. Since weather plays such a critical role in the success or failure of an eclipse expedition, you'll need to carefully study Jay Anderson's excellent analysis. Jay is a legendary eclipse chaser and I was on his mission in 1991. I have come to respect his analysis as the best around.

Eclipse Season: Three Solar and Lunar Eclipses all in a row

For most people it is a surprise to learn that Solar and Lunar eclipses are quite frequent events. Every six months we have an "Eclipse Season" in which we have two or sometimes three eclipses over the course of a few weeks, depending on the exact geometry of the Sun-Earth-Moon trio. June is one of these months, starting with a Partial Solar Eclipse (today), then a Total Lunar Eclipse mid-month, and finishing with a Partial Solar Eclipse (actually in July, but just hours after the end of June!).

Eclipses are indeed common for Planet Earth, but for a given fixed location on the planet, eclipses are less common. For example, the first eclipse (Solar) of June is visible only from the very far north regions of the planet. The Total Lunar Eclipse mid-June will be visible primarily in the eastern hemisphere, so for those of us in San Francisco, it will take place during the day when we cannot see the Moon. And the final (Solar) eclipse of this eclipse season will be visible only in a small region of the globe deep in the southern hemisphere.

Eclipses come in "seasons" because they can only happen when the Moon is precisely positioned to cast its shadow on the Earth, or when the Moon passes precisely through the Earth's shadow. As the Moon's orbit is not exactly aligned with the Earth's orbit, the two orbits (and shadows) come into alignment for a few weeks every six months. The rest of the time, the shadows of the Moon and Earth miss each other and we are eclipse-free!

Since eclipses are such dramatic events, when they are visible in your area, you should go out of your way to see them. For us in California, the next good eclipse will be a Total Lunar Eclipse on December 10th. More on that when the date draws nearer.

Meanwhile, if you want to know more about upcoming eclipses, visit the excellent on-line resource from NASA. The NASA Eclipse Web Site is filled with detailed information about solar and lunar eclipses, including maps, charts, and exact timing for each event. Another excellent resource is the EarthView Eclipse Network. The image (above) is courtesy of the EarthView Eclipse Network.

Vernal Equinox, Super Full Moon, and other astronomical musings

I enjoy sharing highlights of the sky with friends and have been blogging for several years now, pointing out events of astronomical interest here as The Urban Astronomer. I was surprised to see the excitement and questions about the Super Full Moon, the coincidence of nature that is leading to a full moon at perigee today. The fact that the general public is being scared into thinking something bad is about to happen is unfortunate, but the fact that people will be out tonight looking at the full moon is the good outcome that I wish for. Of course, there is absolutely nothing to be worried about. Every 29 days the Moon swings a bit closer to the Earth than other times of the month, and that pattern of perigee and apogee, full and new, repeats in a beautiful "super pattern" every 18 years, something now known (but likely not fully understood) by the many who are reading about the Super Full Moon being the biggest one in 18 years.

There are numerous patterns and cycles in the heavens. Tomorrow, March 20th, is the Vernal Equinox, the semi-annual moment when the length of the day is exactly 12 hours everyone on Earth. I like that dynamic, a twice-a-year event in which we are all given equal periods of sun above the horizon and below the horizon, regardless of your latitude, regardless of whether you are in the Northern or Southern Hemisphere. That is a moment of beauty in the grand annual rhythms of our home planet.

The pattern of lunar repetition that lasts for just longer than 18 years is also responsible for the cycle of lunar and solar eclipses that take place around the world. I witnessed a total solar eclipse in Europe in July 1999, and the celestial dynamics of that eclipse will exactly repeat in August 2017 when a wonderful total solar eclipse will sweep across the United States. For me, it will be a rare chance to be standing in the shadow of the Moon on the second passing of this particular alignment of Moon, Earth and Sun, one that will be far more dramatic and meaningful to me than any particular Super Full Moon you might encounter between now and then. But in the end, if you can find some meaning and solace looking up at the Moon tonight, savor the moment and mark your calendar for April 2029 when the conditions will align themselves and present you with a chance to relive this magic moment when you saw a particularly big and impressive full moon. That is something worth pondering, and the rest of the media hype you are hearing right now should be simply ignored.

Image courtesy NASA.

A Must See: Four Planets and the Moon

This week the sky features four of the brightest planets in a beautiful lineup in the sunset sky. The illustration on the left, borrowed from Sky & Telescope Magazine, demonstrates how the planets all align themselves in a path across the sky known as the Ecliptic. This line in the sky, actually a gentle curve from west to east across the south part of the sky, is the plane of the Solar System as viewed from our observing platform on Earth. We see fast-moving Mercury close to the Sun, then Venus, Mars and Saturn, a most impressive line-up.

To set this into perspective, the young Moon emerges from the glare of the Sun on Tuesday 13th, moving somewhat parallel to the Ecliptic but each day a bit farther south of the Ecliptic. This is because the orbit of the Moon around the Earth is slightly inclined to the rest of the bodies in the Solar System. And as we just had a Total Solar Eclipse on Sunday, the Moon is following a path away from the Ecliptic into what is called the "descending node" south of the Ecliptic.

I will be talking about this at the California Academy of Sciences at their Nightlife event this Thursday in Golden Gate Park. If you are in or near San Francisco, please join me on the roof for Star Tours!

Total Solar Eclipse 2010

One of the most dramatic spectacles of nature takes place Sunday July 11th, as the New Moon passes in front of the Sun and creates a Total Solar Eclipse over the South Pacific Ocean. This eclipse will be especially unique for those who travel to Easter Island to see it. As the shadow of the Moon sweeps across the ocean at speeds of up to 1000 miles per hour, the darkness will pass directly across Easter Island and the famous Moai, the large stone statues that are nearly 1000 years old.

I have experienced Total Solar Eclipses in the past and they are remarkable, not only for the brilliant image you see in the sky, but also for the dramatic changes in the environment you experience as the sky slowly darkens, the horizon changes color, the animals begin to react strangely, and the fellow eclipse-chasers react with great anticipation. Although I will not travel to this one, I plan to travel to one of the upcoming eclipses in the next few years.

For those in the US who don't want to travel far, your next chance to experience at Total Solar Eclipse will be 2017.

Star-and-Planet Drama

The evening sky over the next few weeks offers a study in the changes that take place in the sky along the path of the Moon and the path of the planets. This is exciting to watch and helps to unveil some of the intricacies of the Solar System, something you can see right from your own backyard. For quite a while now I have been particularly fond of sharing the path of the planets across the sky (the "Ecliptic") while conducting star parties and giving astronomy talks. I find that the ability to visualize this band across the sky is an important one for those who wish to have a basic understanding of the motion of the planets across the sky. And for several months the bright planets, a collection of bright stars, and the monthly sweep of the Moon across the sky have provided a perfect laboratory for learning. This month is no exception.

Shortly after sunset there is an excellent parade of planets and stars easily visible as the glare of dusk fades, starting with brilliant Venus in the west, and then in succession from west to south are Regulus, Mars, Saturn and Spica. These bright objects show the line of the Ecliptic.

At the end of this week there is a total solar eclipse (unfortunately not visible

from the San Francisco Bay Area). The eclipse comes at the middle of an Eclipse Season and as such, the Moon follows a descending path below the Ecliptic in the days that follow the eclipse, in particular from the 12th to the 17th of July. As it moves from day to day, it swoops just below the Ecliptic and makes a pleasant arc across the southern sky below Venus and Regulus, then Mars, then Saturn and then Spica.

And in addition, we are just coming into a period of time when fast-moving Venus has close encounters with the other planets and stars along the Ecliptic, starting with a close encounter of Regulus on the 9th of July. More drama to come in the next few weeks -- stay tuned!

The Path That Leads to the Earth's Shadow

We are in an "Eclipse Season," a five week period of time when the Moon's orbit around the Earth is aligned in a way that the Full or New Moon crosses the path of the Earth around the Sun. When that happens, we experience a Lunar or Solar Eclipse and right now we have one of each coming up: a partial Lunar Eclipse on Saturday 26th, and a total Solar Eclipse on July 11th. The Solar Eclipse will not be visible from North America so we don't get a chance to experience that, but the Lunar Eclipse will be. More on that next week.
During an Eclipse Season, the Moon's position in the sky is special, as it is moving just above or just below the plane of the planets (the "Ecliptic") in the interval from New Moon to Full Moon. A few days ago as the Moon emerged from the evening glare waxing each evening, you could see it move just below Venus, then below Regulus and Mars, and now it is below Saturn and Spica, all objects on or near the Ecliptic. As it nears Full Moon and the Lunar Eclipse on the 26th, it is moving closer and closer to the Ecliptic and will intersect the Earth's shadow on the 26th.
I like to imagine that there is a dark spot in the sky where the Earth's shadow projects out into space. Every month as the Moon nears Full, it sweeps close to that spot. But only during an Eclipse Season -- every six or twelve months -- does it slip into the shadow of the Earth and display to all of us the curved shadow of the Earth. That is something to look forward to next weekend.

Annular Solar Eclipse of 2010

Eclipses are very exciting events, special moments that provide beautiful visual spectacles in the sky. Every year there are typically two to three eclipses of the Sun ("solar eclipses") and two to three eclipses of the Moon ("lunar eclipses"). And for each eclipse the event can be "total" (where the Sun or Moon is fully blocked out), or "partial" where a portion of the Sun or Moon is blocked out, but a portion is still visible.

Last month there was one such event, a type of solar eclipse called an Annular Eclipse. In this configuration, the Moon's disk appears to block out most the Sun but does not completely block it out. What makes the Annular Eclipse very special, however, is that the disk of the Moon is fully encircled by the Sun. The eclipse in January was not visible here in San Francisco but was seen in the eastern hemisphere. A fellow astronomy blogger and resident of Sri Lanka, Desh, put together an eclipse page that has video footage of the event and lots of great photographs. He organized a major eclipse viewing event for Sri Lanka.

Throughout 2010 there are more eclipses. The biggest event of the year is the Total Solar Eclipse that happens this July 11th, but again will not be visible here in San Francisco. To see this one you will need to travel to the South Pacific. The NASA Eclipse web site is full of details on this and every eclipse and for those of you who want to travel to see a Total Solar Eclipse someday, consult the NASA Total Solar Eclipse Paths map on their website. I think of it as a long-range travel planner!

For those of us in the Bay Area (and the entire Western Hemisphere), mark your calendars for December 21st when we get a beautiful Total Lunar Eclipse on the solstice to welcome in the winter.

Note: for a nice audio description of an eclipse, listen to my recent interview on KALW (just after the stargazing part of the interview).

Total Solar Eclipse in Asia

Today a large part of the eastern hemisphere experienced a solar eclipse, and along a narrow band of Earth viewers were well positioned to experience a Total Solar Eclipse, a rare and beautiful phenomenon. Unfortunately for most, the summer weather was miserable and the skies were cloudy - something that eclipse viewers (and eclipse chasers like me) don't want. Still, there was some limited visibility from a few observing sites. The tour group organized by Sky & Telescope Magazine saw a "murky" total solar eclipse. Better than none, I suppose.

For those of you wishing to see one closer to home, you'll have to wait until 2017 for a Total Solar Eclipse in the USA.