A Partial Solar Eclipse Down Under

partial solar eclipse
partial solar eclipse
A partial solar eclipse as seen from New York City on November 3rd, 2013. Image credit and copyright: Valentin Lyakhovich

Eclipse season in nigh… though most of us won’t notice the start this week. The second eclipse season for 2018 commences with the arrival of New Moon and Brown Lunation number 1182 at 3:01 Universal Time on (triskaidekaphobics take note) Friday July 13th, 2018. This eclipse is a shallow partial, just skimming the southern hemisphere of the Earth between the Australian and Antarctic continents.

The Eclipse

We doubt many eclipse chasers will make the pilgrimage to Tasmania to see such a slim partial, though we know of at least one, veteran eclipse chaser Jay Pasachoff who has expressed intent on the Yahoo! Solar Eclipse Message List (SEML) message board to head southward this week.

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The course of the July 13th, 2018 partial solar eclipse. NASA/A.T. Sinclair/GSFC

Tasmania gets the best view, with a maximum 9.5% obscuration of Sol as seen from the capital Hobart around 3:25 UT. The upper limit of the eclipse path just skims the southern coast of Australia across the Great Australian Bight and the southern Indian Ocean, and nicks the very southern tip of the south island of New Zealand and Steward Island at 3:48 UT with a barely discernible 1% eclipse before the lunar penumbra departs the Earth. If skies are clear, the very best view just might come along the coast of Antarctica, as the 33% eclipsed Sun rolls along the northern horizon.

Antarctic view
Looking northward along the Antarctic coast on July 13th. Credit: Stellarium

Perhaps a few lone penguins will notice, if they bother to look at the Sun filtered through the murk of the atmosphere along the horizon. France does have one permanently occupied research station in Antarctica named Dumont D’urville along the coast that will see a 30% eclipsed Sun on the horizon right around 3:00-3:15 UT.

We say that this heralds the start of eclipse season, as the ascending node where the Moon’s orbit intersects the ecliptic plane is very near the current position of the Sun. In fact, node crossing occurs at 18:50 UT on July 13th, just 24 hours after New Moon. Eclipses always occur in at least pairs, and the Full Moon two weeks later is close enough to the descending node for a nearly central total lunar eclipse on July 27th (more on that in a bit). This season, however, is special, with a third eclipse ending the cycle on August 11th, 2018, this time gracing the Arctic pole of the Earth along with Scandinavia and Russia.

We’re already seeing some hype surrounding this event as a “Supermoon eclipse,” as the Moon reaches perigee 5 hours 27 minutes past maximum eclipse. Note that this also sets us up for a Minimoon total lunar eclipse two weeks later, as the Moon is near apogee on July 27th.

The Moon’s orbit is tilted 5.145 degrees relative to the plane of the ecliptic, and the nodes make one full revolution around the Earth relative to the equinoctial points once every 18.6 years in what’s known as the precession of the line of apsides.

Viewing a Partial

A partial solar eclipse means that all safety precautions must be taken throughout all phases of the eclipse. This means using approved solar filters that fit snugly over the aperture of a telescope, and solar glasses with the approved ISO 12312-2 rating for solar viewing. We built a safe binocular filter out of a set of spare eclipse safety glasses for the August 21st, 2017 total solar eclipse last year.

Eclipse Safety
Practicing eclipse safety at the Pisgah Astronomical Research Institute in North Carolina during the August 21st, 2017 Great American Eclipse. Image credit: Myscha Theriault

Unfortunately as of writing this, the disk of Sol is blank in terms of Earthward facing sunspots, and may be so on eclipse day. We’re currently headed towards a profound solar minimum and the Sun has already been spotless for more than half of 2018 thus far.

Don’t own a solar filter, safety glasses or a telescope? You can always use our tried and true method of projecting the eclipse using a spaghetti strainer.

It’s all in the gamma. This eclipse is partial only, because the dark inner shadow or umbra misses the Earth by 35.4% of the radius of the planet or about 1,400 miles. The gamma for an eclipse states how many Earth radii an eclipse deviates from central (where the Moon’s umbra is aimed straight at the center of the Earth) and Friday’s eclipse has a gamma value of 1.3541.

Tales of the Saros

Friday’s eclipse is part of an older saros series, member 69 of 71 eclipses for saros series 117. This saros started waaaaaay back on June 24th, 792 AD, and produced its last total solar eclipse on May 9th, 1910. This was also the last total solar eclipse for Tasmania until June 25th, 2131. This series only has two more eclipses to go, with its last event occurring briefly over the Antarctic on August 3rd, 2054. Perhaps, Friday’s event will be the very last one witnessed by human eyes for saros 117.

Tasmania eclipse
Mr. E. Carns Driffield’s drawing of Total Solar Eclipse of the Sun on 9 May 1910. Image credit: Joy Olney.

This also sets us up for the best of the three eclipses this season, the total lunar eclipse at the end of the month on July 27th. This eclipse will be widely visible across Africa, Europe, Asia and Australia—only the Americas miss out.

A Possible Views… “From Spaaaaaaace…”

The International Space Station also threads its way through the outer shadow of the Moon towards the end of the event Friday at ~3:50 UT. ESA’s solar observing Proba-2 spacecraft might just get a very brief view as well from its vantage point in low Earth orbit, around 3:09 UT.

proba-2
Proba-2’s brief view of the eclipse on July 13th at 3:08 UT. Credit: Starry Night.

And although most of us miss out on Friday’s eclipse, you can still try and spot the slender crescent Moon on the evening of Friday, July 13th. The U.S. East Coast is particularly well placed to try and spy the slim Moon low to the west, only 22 hours after New. After that, the Moon tours all of the naked eye planets, passing Mercury and Venus this weekend and passing Jupiter, Saturn and Mars en route to the July 27th total lunar eclipse.

Will anyone webcast the eclipse live? So far, no webcasts (not even from the venerable Slooh site) have surfaced… if anyone else is planning on featuring the July 13th partial solar eclipse, let us know!

It’s the biggest question when it comes to solar eclipses. When’s the next total? Well, just under a year from now, the next total solar eclipse crosses Chile and Argentina on July 2nd, 2019. Note that this event crosses over several major astronomical observatories at La Silla. How many newly minted eclipse chasers fresh off last year’s Great American Eclipse experience can’t wait until totality next visits the United States on April 8th , 2024 and plan to head to South America next summer?

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Partial eclipse rising over the Vehicle Assembly Building at the Kennedy Space Center on the morning of November 3rd, 2013. Image credit: Dave Dickinson.

A partial eclipse may not inspire many eclipse chasers to hop on a plane, but we can still marvel at the celestial ticks of a clockwork Universe carry on, right on schedule.

-Got the eclipse chasing bug? Read all about eclipse chasing, observing and photography in our new book, the Universe Today Guide to Viewing the Cosmos: Everything You Need to know to Become and Amateur Astronomer out on October 23rd.

Get Set For a “Super Blue Blood Moon Total Lunar Eclipse”

total lunar eclipse
total lunar eclipse
Totality! Not a “Super Blue Blood Moon Total Lunar Eclipse,” but the “Winter Solstice Total Lunar Eclipse” of December, 2010. Dave Dickinson

Can you feel the tremor in the Force? Early next Wednesday morning internet astro-memes collide, in one of the big ticket sky events of the year, with a total lunar eclipse dubbed as — get ready — a Super Blue Blood Moon total lunar eclipse.

Specifics on the eclipse: That’s a mouthful, for sure. This is the first eclipse of 2018, and only one of two featuring totality, lunar or solar. Wednesday morning’s eclipse favors the region centered on the Pacific Rim, with regions of Asia and Australia seeing the evening eclipse at moonrise, while most of North America will see totality early Wednesday morning at moonset. Only the regions of the Canadian Maritimes and the United States east of the Mississippi misses out on the spectacle’s climax, catching a partially eclipsed Moon setting in the west at sunrise.

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The path of the Moon through the Earth’s shadow and the circumstances for the January 31st, super blue blood Moon total lunar eclipse. NASA

2018 features four eclipses overall, two lunar and two solar. Paired with this eclipse is a partial solar eclipse on February 15th favoring the very southern tip of South America, followed by another total lunar eclipse this summer on July 27th. The final eclipse for 2018 is a partial solar eclipse on August 11th, favoring northern Europe and northeastern Asia.

What’s all the fuss about? Let’s dissect the eclipse, meme by meme:

Why it’s Super: Totality for this eclipse lasts 1 hour, 16 minutes and 4 seconds, the longest since April 15th, 2014. Full Moon (and maximum duration for this eclipse) occurs at 13:30 Universal Time (UT), just 27 hours after the Moon reaches perigee the day prior on January 30th at 9:55 UT . Note that this isn’t quite the closest perigee of the year in space and time: the January 1st Full Moon perigee beat it out for that title by 2,429 km (1509 miles) and 23 hours.

super blue blood moon
Worldwide circumstances for Wednesday’s super blue blood moon total lunar eclipse. NASA

Why it’s Blue: This is the second Full Moon of the month, making this month’s Moon “Blue” in the modern sense of the term. This definition comes down to us thanks to a misinterpretation in the July 1943 issue of Sky & Telescope. The Maine Farmer’s Almanac once used an even more convoluted definition of a Blue Moon as “the third Full Moon in an astronomical season with four,” and legend has it, used blue ink in the almanac printing to denote that extra spurious Moon… anyone have any old Maine Farmer’s Almanacs in the attic to verify the tale?

Note that Blue Moons aren’t all that rare… the month of March 2018 also hosts two Full Moons, while truncated February 2018 contains none, sometimes referred to as a “Black Moon”.

Why All the Blood: The cone of the Earth’s umbra or dark inner shadow isn’t completely devoid of light. Instead, you’re seeing sunlight from all the Earth’s sunrises and sunsets around its limb, filtered into the shadow of the the planet onto the nearside of the Moon. Standing on the Earthward facing side of the Moon, you would witness a solar eclipse as the Earth passed between the Moon and the Sun. Unlike the neat near fit for solar eclipses on the Earth, however, solar eclipses on the Moon can last over an hour, as the Earth appears about three times larger than the disk of the Sun. And although astronauts have witnessed eclipses from space, no human has yet stood on the Moon and witnessed the ring of fire surrounding the Earth during a solar eclipse.

Tales of the Saros: For saros buffs, this eclipse is member 49 of 74 lunar eclipses for lunar saros cycle 124, stretching all the way back to August 17th, 1152. If you caught the total lunar eclipse on January 21st, 2000, you saw the last eclipse in this cycle. Stick around until April 18th, 2144 AD and you can watch the final total lunar eclipse for saros 124.

Unlike total solar eclipses, lunar eclipses are leisurely affairs. The entire penumbral phase of the eclipse lasts for over 5 hours, though you probably won’t notice the subtle shading on the limb of the Moon until its about halfway immersed in the Earth’s penumbral shadow.

Not all total lunar eclipses are the same. Depending on how deep the Moon passes through the Earth’s shadow and the murkiness of the Earth’s atmosphere, the Moon can appear anywhere from a sickly orange, to a deep brick red during totality… for example, the Moon almost disappeared entirely during a total lunar eclipse shortly after the eruption of Mount Pinatubo in the early 1990s!

The color of the Moon during totality is known as its Danjon Number, with 4 being bright with a bluish cast on the outer limb of the Moon, and 0 appearing dark and deep red.

This is also one of the only times you can see that the Earth is indeed round with your own eyes as the curve of the shadow cast by our homeworld falls back across the Moon. This curve is the same, regardless of the angle, and whether the Moon is high above near the zenith, or close to the horizon.

Don’t miss the first eclipse of 2018 and the (deep breath) super blue blood Moon total lunar eclipse!

-Clouded out, or on the wrong side of the planet? Watch the January 31st eclipse live courtesy of the Virtual Telescope Project.

Sunday Night: Getting Ready For a ‘Super-Harvest-Blood-Moon Total Lunar Eclipse’

So, heard the one about this weekend’s impending ‘Super-Harvest-Blood-Moon eclipse?’ Yeah, us too. Have no fear; fortunately for humanity, the total lunar eclipse transpiring on Sunday night/Monday morning is a harbinger of nothing more than a fine celestial spectacle, clear skies willing.

This final eclipse of the ongoing lunar tetrad has some noteworthy events worth exploring in terms of science and lore.

The Supermoon Total Lunar Eclipse of September 27-28 2015 from Michael Zeiler on Vimeo.

The Specifics: First, you almost couldn’t ask for better timing. This weekend’s total lunar eclipse occurs during prime time Sunday night for North and South America, and early Monday morning for Europe, Africa and most of the Middle East. This means the Atlantic Region and surrounding areas will see totality in its entirety. This eclipse occurs very near the northward equinoctial point occupied by the Sun during the Northern Hemisphere Spring equinox in March. The date says it all: this eclipse coincides with the Harvest Moon for 2015, falling just under five days after the September equinox.

Early cloud cover prospects for Sunday night over the contiguous United States. Image credit: The National Weather Service
Early cloud cover prospects for Sunday night over the contiguous United States. Image credit: The National Weather Service

For saros buffs, Sunday’s eclipse is part of lunar saros series 137, member 28 of 81. This saros started back in 1564 and produced its first total lunar eclipse just two cycles ago on September 6th 1979. Saros 137 runs all the way out to its final eclipse on April 20th, 2953 AD.  

And yes, this upcoming total lunar eclipse occurs very near the closest lunar perigee for 2015. How rare are ‘Supermoon’ lunar eclipses? Well, we took a look at the phenomenon, and found 15 total lunar eclipses occurring near lunar perigee for the current century:

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Perigee eclipses for the 21st century. To make the cut, a total lunar eclipse needed to occur within 24 hours of lunar perigee.  Image credit: Dave Dickinson

You’ll note that four saroses (the plural of saros) are producing perigee or ‘Proxigean’ total lunar eclipses during this century, including saros 137.

Does the perigee Moon effect the length of totality? It’s an interesting question. Several factors come into play that are worth considering for Sunday night’s eclipse. First, the Moon moves a bit faster near perigee as per Kepler’s second law of motion. Second, the Moon is a shade larger in apparent size, 34’ versus 29’ near apogee. Lastly, the conic section of the Earth’s shadow or umbra is a bit larger closer in; you can fit three Moons side-by-side across the umbra around 400,000 kilometers out from the Earth. Sunday night’s perigee occurs 65 minutes after Full Moon at 2:52 UT/10:52 PM EDT. Perigee Sunday night is 356,876 kilometers distant, the closest for 2015 by just 115 kilometers, and just under 500 kilometers short of the closest perigee that can occur. This is, however, the closest perigee time-wise to lunar totality for the 21st century; you have to go all the way back to 1897 to find one closer, at just four minutes apart.

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An 1888 depiction of a total lunar eclipse. Image credit: E. Weib, Bilderatlas de Sternenwelt

Now, THAT was and eclipse!

This all culminates in a period for totality on Sunday night of just under 72 minutes in duration, 35 minutes shy of the maximum possible for a central total lunar eclipse. An eclipse won’t top this weekend’s in terms of duration until January 31st 2018.

 

Here are the key times to watch for on Sunday night:

Penumbral phase begins: 00:12 UT/8:12 PM EDT (on the 27th)

Partial phase begins: 1:07 UT/9:07 PM EDT

Totality begins: 2:11 UT/10:11 PM EDT

Totality ends: 3:23 UT/11:23 PM EDT

Partial phase ends: 4:27 UT/00:27 AM EDT

Penumbral phase ends: 5:22 UT/1:22 AM EDT

Note that one 18 year 11 day and 8 hour saros period later, saros 137 will again produce a perigee eclipse nearly as close as this weekend’s on October 8th, 2033.

The classic hallmark of any total lunar eclipse is the reddening of the Moon. You’re seeing the combination of all the world’s sunsets, refracted into the inky umbra of the Earth and cast upon the surface of the Moon. To date, no human has stood upon the surface of the Moon and gazed upon the spectacle of a solar eclipse caused by the Earth.

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The orientation of the Sun and Earth as seen from the Moon during Sunday night’s eclipse. Image credit: Stellarium

Not all eclipses are created equal when it comes to hue and color. The amount of dust and aerosols suspended in the atmosphere can conspire to produce anything from a bright, yellowish-orange tint, to a brick dark eclipse where the Moon almost disappears from view entirely. The recent rapid fire tetrad of four eclipses in 18 months has provided a good study in eclipse color intensity. The deeper the Moon dips into the Earth’s shadow, the darker it will appear… last April’s lunar eclipse was just barely inside the umbra, making many observers question if the eclipse was in fact total at all.

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Refraction of sunlight during a total lunar eclipse. Image credit: Raycluster/Public Domain

We the describe color of the eclipsed Moon in terms of its number on the Danjon scale, and recent volcanic activity worldwide suggests that we may be in for a darker than normal eclipse… but we could always be in for a surprise!

Old time mariners including James Cook and Christopher Columbus used positional measurements of the eclipsed Moon at sea versus predictions published in almanac tables for land-based observatories to get a one-time fix on their longitude, a fun experiment to try to replicate today. Kris Columbus also wasn’t above using beforehand knowledge of an impending lunar eclipse to help get his crew out of a tight jam.

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A long timelapse of totality during a 2003 total lunar eclipse, back from the glorious days of film. Image credit: Dave Dickinson

And speaking of the next perigee Moon total lunar eclipse for saros 137 on October 8th, 2033…  if you catch that one, this weekend’s, and saw the September 16th, 1997 lunar eclipse which spanned the Indian Ocean region, you’ll have completed an exeligmos, or a triple saros of eclipses in the same series 54 years and 33 days in length, an exclusive club among eclipse watchers and a great word to land on a triple letter word score in Scrabble…

Exeligmos is also the title of one of our original scifi tales involving eclipses, along with Shadowfall.

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The 2010 winter solstice eclipse. Image credit: Dave Dickinson

Here’s another neat challenge: the International Space Station makes two shadow passes during the lunar eclipse over the contiguous United States. The first one occurs during totality, and spans from eastern Louisiana to central Maine from 2:14 to 2:20 UT; the second pass occurs during the final partial phases of the eclipse spanning from southern Arizona to Lake Superior from 3:47 to 3:54 UT. These are un-illuminated shadow passes of the ISS. Observers have captured transits of the ISS during a partial solar eclipse, but to our knowledge, no one has ever caught a transit of the ISS during a total lunar eclipse; ISS astros should also briefly be able to spy the eclipsed Moon from their orbital vantage point. CALSky will have refined passage times about 48 hours prior to Sunday.

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Projections for ISS shadow passes across the Moon during Sunday night’s eclipse. The first path occurs during totality, and the second during the final partial phases of the eclipse. Image credit: Dave Dickinson/calculations from CALSky

Clouded out? Live on the wrong side of the planet? The good folks at the Virtual Telescope Project have got you covered, with a live webcast of the total lunar eclipse starting at 1:00 UT/9:00 PM EDT.

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Image credit: The Virtual Telescope Project

And as the eclipse draws to an end, the question of the hour always is: when’s the next one? Well, the next lunar eclipse is a dim penumbral on March 23rd, 2016, which follows a total solar eclipse for southeastern Asia on March 9th, 2016… but the next total lunar won’t occur until January 31st, 2018, which also happens to be the second Full Moon of the month… a ‘Blue Blood Moon Eclipse?’

Sorry, we had to go there. Hey, we could make the case for Sunday’s eclipse also occurring on World Rabies Day, but perhaps a ‘Rabies Eclipse’ just doesn’t have the SEO traction. Don’t fear the Blood Moon, but do get out and watch the final lunar eclipse of 2015 on Sunday night!