David Dickinson, Author at Universe Today

April 7, 2015December 23, 2015 by David Dickinson

Was This Past Weekend’s Lunar Eclipse Really Total?

Totality... or not? Image credit and copyright: Héctor Barrios

Millions of viewers across the western United States and across the Pacific, to include Australia and New Zealand were treated to a fine Easter weekend lunar eclipse on Saturday. And while this was the third of the ongoing tetrad of four lunar eclipses, it was definitely worth getting up early for and witnessing firsthand.

But was it truly total at all?

To Recap: The April 4th eclipse featured the shortest advertised duration for totality for the 21^st century, clocking in at just four minutes and 43 seconds in length. In fact, you’d have to go all the way back to 1529 to find a shorter span of totality, at one minute and 42 seconds. And you’ll have to wait until September 11^th, 2155 to find one that tops it in terms of brevity.

The April 4th lunar eclipse over the Las Vegas strip. Image credit and copyright: John Lybrand

We wrote recently about the saros cycle, and how this past weekend’s eclipse was the first in lunar saros series 132 to feature totality.

A fascinating discussion as to whether this was a de facto total lunar eclipse has recently sprung up on the message boards and a recent Sky and Telescope article online.

The geometry that creates a total lunar eclipse. Credit: NASA

It all has to do with how you gauge the shape and size of the Earth’s shadow.

This is a surprisingly complex affair, as the Earth’s atmosphere gives the umbra a ragged and indistinct edge. If you’ve ever taken our challenge to determine your longitude using a lunar eclipse — just as mariners such as Christopher Columbus did while at sea — then you know how tough it is to get precise contact timings. There has been an ongoing effort over the years to model the size changes in Earth’s shadow using crater contact times during a lunar eclipse.

Many observers have commented in forums and social media that the northern limb of the Moon stayed pretty bright throughout the brief stretch of totality for Saturday’s eclipse.

What happens (in the skies over) Vegas... the lunar eclipse captured from the Luxor Hotel. Image credit and copyright: Rob Sparks — What happens (in the skies over) Vegas… the lunar eclipse captured from the Luxor Hotel. Image credit and copyright: Rob Sparks

“There are 3 ways of computing the magnitude of a lunar eclipse,” Eclipse expert David Herald mentioned in a recent Solar Eclipse Message List (SEML) posting:

The ‘traditional’ way as used in the Astronomical Almanac is attributed to Chauvenet – where the umbral radius is increased by a simple 2% – with the radius being based on the Earth’s radius at 45 deg latitude (and otherwise the oblateness of the Earth is ignored). For this eclipse the Chauvenet magnitude was 1.005.

The second way (used in the French Almanac, and more recently by Espenak & Meeus in their ‘Five Millennium Canon of Lunar Eclipses’ is the Danjon method. It similarly uses the Earth’s radius at 45 deg (and otherwise the oblateness is ignored), and increases the Earth’s radius by 75km. For this eclipse the Danjon magnitude is 1.001

The most recent approach (Herald & Sinnott JBAA 124-5 pgs 247-253, 2014) is based on the Danjon approach; however it treats the Earth as oblate, allows for the varying inclination of the Earth relative to the Sun during the year, and increases the Earth’s radius by 87km – being the best fit to 22,539 observations made between 1842 and 2011. For this eclipse the magnitude is computed as 1.002.

“As for eclipses, to me it is total when sliver of light comes through the edge of the Earth’s profile,” eclipse chaser Patrick Poitevin told Universe Today. “Once a minimum of light passes through any of the lunar dales (as it does during a total solar eclipse) I do not concede it as a total. Same for a lunar eclipse.”

A partial phase for the April 4th lunar eclipse above a silo. Image credit and copyright: Brian who is called Brian

Michael Zeiler at the Great American Eclipse also had this to say to Universe Today about the subject:

This is a complex question because the shape of the Earth’s umbra upon the Moon is diffuse due to the effects of the Earth’s atmosphere. The various models used (with corrected radii for the Earth) are empirically based on crater timings of past lunar eclipses, of which there is some uncertainty. I’m sure this accounted for the difference between the USNO duration of eclipse and NASA.

The comment (in the recent Sky & Telescope post online) by Curt Renz is valid; correcting for the Earth’s flattening (meaning that the Earth’s radius from pole to pole is about a third of a percent shorter than the radius across the equator) might influence whether this very low magnitude eclipse is total or not. I haven’t made the calculation whether the Earth’s flattening tips this eclipse from total to partial, but it’s plausible.

Totality! Image credit and copyright: Rolf Wahl Olsen

There is another wrinkle: due to parallactic shifts of the Moon when observing from either pole of the Earth, it might be that for a lunar eclipse right on the knife edge of total/partial, that it may indeed be total from one polar region and partial from another. This is a kind of libration, but it would be a very subtle difference and probably unobservable.

It is only possible to conclusively define Saturday’s eclipse as total or partial if you define a brightness threshold for the Sun’s photosphere illuminating an edge of the Moon. The problem here is that this line is indistinct and fuzzy. I watched the lunar eclipse carefully with this question in mind and I could not decide for myself whether this lunar eclipse was total or partial. I think it would require a photometer to make this distinction.

Certainly, there’s little record of just how the 102 second long lunar eclipse of 1529 appeared. Ironically, it too was a total eclipse near sunrise as seen from Europe. On the other side of the coin, the deep partial eclipse of August 26^th, 1961 just missed totality at 98.6% obscuration… and the two lunar eclipses in 2021 have similar circumstances, with a barely total lunar eclipse just 15 minutes long on May 26^th and a 97.4% partial lunar eclipse on November 19^th.

The circumstances for the 1529 total solar eclipse. Image credit: F.Espenak/NASA/GSFC

So maybe we won’t have to wait until 2155 to see another brief lunar eclipse that blurs the lines and refuses to play by the rules.

The eclipse as seen from Coral Towers Observatory. Image credit and copyright: Joseph Brimacombe

What do you, the readers think? What did you see last Saturday morn, a bright total lunar eclipse, or a deep partial?

April 2, 2015October 10, 2016 by David Dickinson

Adventures in Satspotting: Why Are Different Orbits Needed for Satellites?

Congratulations: perhaps you’re a new space-faring nation, looking to place a shiny new payload around the planet Earth. You’ve assembled the technical know-how, and seek to break the surly bonds and join an exclusive club that thus far, only contains 14 nations capable of indigenous spaceflight. Now for the big question: which orbit should you choose?

Welcome to the wonderful world of orbital mechanics. Sure, satellites in orbit have to follow Newton’s laws of motion, as they perpetually ‘fall’ around the Earth without hitting it. But it’ll cost you in fuel expended and technical complexity to achieve different types of orbits. Different types of orbits can, however, be used to accomplish different goals.

The first artificial moon to be placed in low-Earth orbit was Sputnik 1 launched on October 4^th, 1957. But even before the dawn of the Space Age, visionaries such as futurist and science fiction author Arthur C. Clarke realized the value of placing a satellite in a geosynchronous orbit about 35,786 kilometres above the Earth’s surface. Placing a satellite in such an orbit keeps it in ‘lockstep’ with the Earth rotating below it once every twenty four hours.

Here are some of the more common orbits targeted by modern satellites and their uses:

Low-Earth Orbit (LEO): Placing a satellite 700 km above the surface of the Earth moving 27,500 km per hour will cause it to orbit the Earth once every 90 minutes. The International Space Station is in just such an orbit. Satellites in LEO are also subject to atmospheric drag, and must be boosted periodically. Launching from the equator of the Earth gives you an initial free maximum 1,670 km/per hour boost into orbit eastward. Incidentally, the high 52 degree inclination orbit of the ISS is a compromise that assures that it is reachable from various launch sites worldwide.

Low Earth orbit is also becoming crowded with space junk, and incidents such as the successful 2007 anti-satellite missile test by China, and the 2009 collision of Iridium 33 and the defunct Kosmos-2251 satellite both showered low Earth orbit with thousands of extra pieces of debris and didn’t help the situation much. There have been calls to make reentry technology standard on future satellites, and this will become paramount with the advent of flocks of nano and CubeSats in LEO.

Sun-Synchronous Orbit: This is a highly inclined retrograde orbit that assures that the illumination angle of the Earth below is consistent on multiple passes. Though it takes a fair amount of energy to reach a Sun-synchronous orbit—plus a complex deployment maneuver known as a ‘dog leg’—this type of orbit is desirable for Earth observing missions. It’s also a favorite for spy satellites, and you’ll notice that many nations aiming to put up their first satellites will use the stated goal of ‘Earth observation’ to field spy satellites of their own.

Molyina orbit: A highly inclined elliptical orbit designed by the Russians, a Molyina orbit takes 12 hours to complete, placing the satellite over one hemisphere for 2/3rds of its orbit and returning it back over the same geographical point once every 24 hours.

A semi-synchronous orbit: A 12-hour elliptical orbit similar to a Molyina orbit, a semi-synchronous orbit is favored by Global Positioning Satellites.

Geosynchronous orbit: The aforementioned point 35,786 km above the Earth’s surface where a satellite stays fixed over a particular longitude.

Geostationary orbit: Place a GEO satellite in orbit with a zero degree orbit, and it is considered Geostationary. Also sometimes referred to as a Clarke orbit, this location is extremely stable, and satellites placed there may remain in orbit for millions of years.

In 2012, the EchoStar XVI satellite was launched headed to GEO with the time capsule disk The Last Pictures for just that reason. It is quite possible that millions of years from now, GEO sats might be the primary artifacts remaining from the early 20th/21st century civilization.

Lagrange point orbits: 18th century mathematician Joseph-Louis Lagrange made the observation that several stable points exist in any three body system. Dubbed Lagrange points, these locales serve as great stable positions to place observatories. The Solar Heliospheric Observatory (SOHO) sits at the L1 point to afford it a continuous view of the Sun; the James Webb Space Telescope is bound in 2018 for the L2 point beyond the Moon. To stay on station near a LaGrange point, a satellite must enter a Lissajous or Halo orbit around the imaginary Lagrange point in space.

All of these orbits have pros and cons. For example, atmospheric drag isn’t an issue in geosynchronous orbit, though it takes several boosts and transfer orbit maneuvers to attain. And as with any plan, complexity also adds more chances for things to fail, stranding a satellite in the wrong orbit. Russia’s Phobos-Grunt mission suffered just such a fate after launch in 2011 when its Fregat upper stage failed to operate properly, stranding the interplanetary spacecraft in Earth orbit. Phobos-Grunt crashed back to Earth over the Southern Pacific on January 15^th, 2012.

Space is a tough business, and it’s imperative to place things in the right orbit!

-Looking to hunt for satellites from your backyard? A great online resource to start with in Heavens-Above.

March 31, 2015December 23, 2015 by David Dickinson

Seeking Ceres: Following the Brave New World Through 2015

A little world is making big headlines in 2015. NASA’s Dawn spacecraft entered orbit around 1 Ceres on March 6^th, 2015, gaving us the first stunning images of the ~900 kilometre diameter world. But whether you refer to Ceres as a dwarf planet, minor planet, or the king of the asteroid belt, this corner of the solar system’s terra incognita is finally open for exploration. It has been a long time coming, as Ceres has appeared as little more than a wandering, star-like dot in the telescopes of astronomers for over two centuries since discovery.

Untitled — The orbit of 1 Ceres. Credit: NASA/JPL

And the good news is, you can observe Ceres from your backyard if you know exactly where to look for it with binoculars or a small telescope. We’ll admit, we had an ulterior motive on pulling the trigger on this post three months prior to opposition on July 24th, as Dawn will soon be exiting its ‘shadow phase’ and start unveiling the world to us up close. The first science observations for Dawn begin in mid-April.

Ceres spends all of 2015 looping through the constellations of Capricornus, Microscopium and Sagittarius. This places it low to the south for northern hemisphere observers on April 1^st in the early morning sky. Ceres will pass into the evening sky by mid-summer. Ceres orbits the Sun once every 4.6 years in a 10.6 degree inclination path relative to the ecliptic that takes it 2.6 AU to 3 AU from the Sun. The synodic period of Ceres is, on average, 467 days from one opposition to the next.

Shining at magnitude +8, April 1^st finds Ceres near the Capricornus/Sagittarius border. Ceres can reach magnitude +6.7 during a favorable opposition. Note that Ceres is currently only 20 degrees east of the position of Nova Sagittarii 2015 No. 2, currently still shining at 4th magnitude. June 29th and November 25th are also great times to hunt for Ceres in 2015 as it loops less than one degree past the 4^th magnitude star Omega Capricorni.

June 30 — Ceres meets up with Omega Capricorni on June 29th. Credit: Stellarium.

You can nab Ceres by carefully noting its position against the starry background from night to night, either by sketching the suspect field, or photographing the region. Fans of dwarf planets will recall that 1 Ceres and 4 Vesta fit in the same telescopic field of view last summer, and now sit 30 degrees apart. Ceres is now far below the ecliptic plane, but will resume getting occulted by the passing Moon on February 3^rd, 2017.

Left — The Palermo transit instrument used to discover Ceres. From *Della Specola Astronomica* (1792)

Ceres was discovered by Giuseppe Piazzi on the first day of the 19^th century on January 1^st, 1801. Ceres was located on the Aries/Cetus border just seven degrees from Mars during discovery. Piazzi wasn’t even on the hunt for new worlds at the time, but was instead making careful positional measurements of stars with the 7.5 centimetre Palermo Circle transit telescope.

At the time, the discovery of Ceres was thought to provide predictive proof of the Titus-Bode law: here was a new planet, just where this arcane numerical spacing of the planets said it should be. Ceres, however, was soon joined by the likes of Juno, Pallas, Vesta and many more new worldlets, as astronomers soon came to realize that the solar system was not the neat and tidy place that it was imagined to be in the pre-telescopic era.

To date, the Titus-Bode law remains a mathematical curiosity, which fails to hold up to the discovery of brave new exoplanetary systems that we see beyond our own.

The view from Ceres itself would be a fascinating one, as an observer on the Cererian surface would be treated to recurrent solar transits of interior solar system worlds. Mercury would be the most frequent, followed by Venus, which transits the Sun as seen from Ceres 3 times in the 21^st century: August 1^st, 2042, November 19^th, 2058 and February 13^th 2068. Mars actually transits the Sun as seen from Ceres even earlier on June 9^th, 2033. Curiously, we found no transits of the Earth as seen from Ceres during the current millennium from 2000 to 3000 AD!

From Ceres, Jupiter would also appear 1.5’ in diameter near opposition, as opposed to paltry maximum of 50” in size as seen from the Earth. This would be just large enough for Jupiter to exhibit a tiny disk as seen from Ceres with the unaided eye. The four major Galilean moons would be visible as well.

The mysteries of Ceres beckon. Does the world harbor cryovolcanism? Just what are those two high albedo white dots? Are there any undiscovered moons orbiting the tiny world? If a fair amount of surface ice is uncovered, Ceres may soon become a more attractive target for human exploration than Mars.

All great thoughts to ponder, as this stellar speck in the eyepiece of your backyard telescope becomes a brand new world full of exciting possibilities.

March 27, 2015October 10, 2016 by David Dickinson

Living with a Capricious Star: What Drives the Solar Cycle?

Solar energy energizes the drama of life on Earth, such as the bird caught transiting the solar disk as seen here. Image credit and copyright: Roger Hutchinson

You can be thankful that we bask in the glow of a relatively placid star. Currently about halfway along its 10 billion year career on the Main Sequence, our Sun fuses hydrogen into helium in a battle against gravitational collapse. This balancing act produces energy via the proton-proton chain process, which in turn, fuels the drama of life on Earth.

Looking out into the universe, we see stars that are much more brash and impulsive, such as red dwarf upstarts unleashing huge planet-sterilizing flares, and massive stars destined to live fast and die young.

Our Sun gives us the unprecedented chance to study a star up close, and our modern day technological society depends on keeping a close watch on what the Sun might do next. But did you know that some of the key mechanisms powering the solar cycle are still not completely understood?

One of the exceptionally active sunspot groups seen for Cycle #24 in early 2014. Image credit: David Dickinson

One such mystery confronting solar dynamics is exactly what drives the periodicity related to the solar cycle. Follow our star with a backyard telescope over a period of years, and you’ll see sunspots ebb and flow in an 11 year period of activity. The dazzling ‘surface’ of the Sun where these spots are embedded is actually the photosphere, and using a small telescope tuned to hydrogen-alpha wavelengths you can pick up prominences in the warmer chromosphere above.

This cycle is actually is 22 years in length (that’s 11 years times two), as the Sun flips polarity each time. A hallmark of the start of each solar cycle is the appearance of sunspots at high solar latitudes, which then move closer to the solar equator as the cycle progresses. You can actually chart this distribution in a butterfly diagram known as a Spörer chart, and this pattern was first recognized by Gustav Spörer in the late 19^th century and is known as Spörer’s Law.

Sunspot_butterfly_graph — The ‘Butterfly diagram’ of sunspot distribution by latitude over previous solar cycles. Image credit: NASA/Marshall Spaceflight Center

We’re currently in the midst of solar cycle #24, and the measurement of solar cycles dates all the way back to 1755. Galileo observed sunspots via projection (the tale that he went blind observing the Sun in apocryphal). We also have Chinese records going back to 364 BC, though historical records of sunspot activity are, well, spotty at best. The infamous Maunder Minimum occurred from 1645 to 1717 just as the age of telescopic astronomy was gaining steam. This dearth of sunspot activity actually led to the idea that sunspots were a mythical creation by astronomers of the time.

But sunspots are a true reality. Spots can grow larger than the Earth, such as sunspot active region 2192, which appeared just before a partial solar eclipse in 2014 and could be seen with the unaided (protected) eye. The Sun is actually a big ball of gas, and the equatorial regions rotate once every 25 days, 9 days faster than the rotational period near the poles. And speaking of which, it is not fully understood why we never see sunspots at the solar poles, which are tipped 7.25 degrees relative to the ecliptic.

Other solar mysteries persist. One amazing fact about our Sun is the true age of the sunlight shining in our living room window. Though it raced from the convective zone and through the photosphere of the Sun at 300,000 km per second and only took 8 minutes to get to your sunbeam-loving cat here on Earth, it took an estimated 10,000 to 170,000 years to escape the solar core where fusion is taking place. This is due to the terrific density at the Sun’s center, over seven times that of gold.

Another amazing fact is that we can actually model the happenings on the farside of the Sun utilizing a new fangled method known as helioseismology.

Another key mystery is why the current solar cycle is so weak… it has even been proposed that solar cycle 25 and 26 might be absent all together. Are there larger solar cycles waiting discovery? Again, we haven’t been watching the Sun close enough for long enough to truly ferret these ‘Grand Cycles’ out.

Are sunspot numbers telling us the whole picture? Sunspot numbers are calculated using formula that includes a visual count of sunspot groups and the individual sunspots in them that are currently facing Earthward, and has long served as the gold standard to gauge solar activity. Research conducted by the University of Michigan in Ann Arbor in 2013 has suggested that the orientation of the heliospheric current sheet might actually provide a better picture as to the goings on of the Sun.

Another major mystery is why the Sun has this 22/11 year cycle of activity in the first place. The differential rotation of the solar interior and convective zone known as the solar tachocline drives the powerful solar dynamo. But why the activity cycle is the exact length that it is is still anyone’s guess. Perhaps the fossil field of the Sun was simply ‘frozen’ in the current cycle as we see it today.

There are ideas out there that Jupiter drives the solar cycle. A 2012 paper suggested just that. It’s an enticing theory for sure, as Jupiter orbits the Sun once every 11.9 years.

The motion of the solar barycenter through the last half of the 20th century. Image credit: Carl Smith/Wikimedia Commons

And a recent paper has even proposed that Uranus and Neptune might drive much longer cycles…

Color us skeptical on these ideas. Although Jupiter accounts for over 70% of the planetary mass in the solar system, it’s 1/1000th as massive as the Sun. The barycenter of Jupiter versus the Sun sits 36,000 kilometres above the solar surface, tugging the Sun at a rate of 12.4 metres per second.

Rigs to view the Sun in both hydrogen-alpha and visible light. Credit: David Dickinson

I suspect this is a case of coincidence: the solar system provides lots of orbital periods of varying lengths, offering up lots of chances for possible mutual occurrences. A similar mathematical curiosity can be seen in Bode’s Law describing the mathematical spacing of the planets, which to date, has no known basis in reality. It appears to be just a neat play on numbers. Roll the cosmic dice long enough, and coincidences will occur. A good test for both ideas would be the discovery of similar relationships in other planetary systems. We can currently detect both starspots and large exoplanets: is there a similar link between stellar activity and exoplanet orbits? Demonstrate it dozens of times over, and a theory could become law.

That’s science, baby.

March 26, 2015December 23, 2015 by David Dickinson

Predicting Eclipses: How Does the Saros Cycle Work?

Boy, how about that total solar eclipse last Friday? And there’s more in store, as most of North America will be treated to yet another total lunar eclipse on the morning of April 4^th. This eclipse is member three of four of a quartet of lunar eclipses, known as a tetrad.

Solar and lunar eclipses are predictable, and serve as a dramatic reminder of the clockwork nature of the universe. Many will marvel at the ‘perfect symmetry’ of eclipses as seen from the Earth, though the true picture is much more complex. Yes, the Sun is roughly 400 times larger in diameter than the Moon, but also about 400 times farther away. This distance isn’t always constant, however, as the orbits of both the Earth and Moon are elliptical. And to complicate matters, the Moon is currently moving 3 to 4 centimetres farther away from the Earth per year. Already, annular eclipses are more common in the current epoch than are total solar eclipses, and about 1.4 billion years from now, total solar eclipses will cease to happen entirely.

This has an impact on lunar eclipses as well. The dark inner umbra of the Earth is an average of about 1.25 degrees across at the distance from Earth to the Moon. The Moon’s orbit is inclined 5.1 degrees relative to the ecliptic plane, which traces out the Earth’s path around the Sun. If this inclination was equal to zero, we’d be treated to two eclipses — one solar and one lunar — every 29.5 day synodic month.

This inclination assures that we have, on average, two eclipse seasons year, and that eclipses occur in groupings of 2-3. The maximum number of eclipses that can occur in a calendar year is 7, which next occurs in 2038, and the minimum is 4, as occurs in 2015.

A solar eclipse occurs at New Moon, and a lunar eclipse always occurs at Full — a fact that many works of film and fiction famously get wrong. And while you have to happen to be in the narrow path of a solar eclipse to witness totality, the whole Moonward facing hemisphere of the Earth gets to witness a lunar eclipse. Ancient cultures recognized the mathematical vagaries of the lunar and solar cycles as they attempted to reconcile early calendars. Our modern Gregorian calendar strikes a balance between the solar mean and tropical year. The Muslim calendar uses strictly lunar periods, and thus falls 11 days short of a 365 day year. The Jewish and Chinese calendars incorporate a hybrid luni-solar system, assuring that an intercalculary ‘leap month’ needs to be added every few years.

But trace out the solar and lunar cycles far enough, and something neat happens. Meton of Athens discovered in the 5^th century BC that 235 synodic periods very nearly equals 19 solar years to within a few hours. This means that the phases of the Moon ‘sync up’ every 19-year Metonic cycle, handy if you’re say, trying to calculate the future dates for a movable feast such as Easter, which falls on (deep breath) the first Sunday after the first Full Moon after the March equinox.

But there’s more. Take a period of 223 synodic months, and they sync up three key lunar cycles which are crucial to predicting eclipses;

Synodic month- The time it takes for the Moon to return to like phase (29.5 days).

Anomalistic month- The time it takes for the Moon to return to perigee (27.6 days).

Draconic month- the time it takes for the Moon to return to a similar intersecting node (ascending or descending) along the ecliptic (27.2 days).

That last one is crucial, as eclipses always occur when the Moon is near a node. For example, the Moon crosses ascending node less than six hours prior to the start of the April 4^th lunar eclipse.

And thus, the saros was born. A saros period is just eight hours shy of 18 years and 11 days, which in turn is equal to 223 synodic, 242 anomalistic or 239 draconic months.

The name saros was first described by Edmond Halley in 1691, who took it from a translation of an 11^th century Byzantine dictionary. The plural of saros is saroses.

This also means that solar and lunar eclipses one saros period apart share nearly the same geometry, shifted 120 degrees in longitude westward. For example, the April 4^th lunar eclipse is member number 30 in a cycle of 71 lunar eclipses belonging to saros series 132. A similar eclipse occurred one saros ago on March 24^th, 1997. Stick around until April 14^th, 2033 and you’ll complete a personal triple saros of eclipses, known as an exeligmos.

Dozens of saros series — both solar and lunar — are underway at any particular time.

But there’s something else unique about April’s eclipse. Though saros 132 started with a slim shallow penumbral eclipse way back on May 12^th, 1492, this upcoming eclipse features the very first total lunar eclipse of the series. You can tell, as the duration of totality is a short 4 minutes and 43 seconds, a far cry from the maximum duration of 107 minutes that can occur during a central eclipse.

Created by author. — The evolution of lunar saros 132, showing five key eclipses out of the 71 in the series. Created by author

This particular saros cycle of eclipses will continue to become more central as time goes on. The final total lunar eclipse of the series occurs on August 2^nd, 2213 AD, and the saros finally ends way out on June 26^th, 2754.

Eclipses, both lunar and solar, have also made their way into the annuals of history. A rising partial eclipse greeted the defenders of Constantinople in 1453, fulfilling a prophecy in the mind of the superstitious when the city fell to the Ottoman Turks seven days later. And you’d think we’d know better by now, but modern day fears of the ‘Blood Moon‘ seen during an eclipse still swirl around the internet even today. Lunar eclipses even helped mariners get a onetime fix on longitude at sea: Christopher Columbus and Captain James Cook both employed this method.

All thoughts to ponder as you watch the April 4^th total lunar eclipse. This eclipse will be visible for observers across the Pacific, the Asian Far East, Australia and western North America, after which you’ll have one more shot at total lunar eclipse in 2015 on September 28th. The next total lunar eclipse after that won’t be until January 31^st 2018, favoring North America.

Welcome to the saros!

Read Dave Dickinson’s eclipse-fueled sci-fi tales Exeligmos and Shadowfall.

March 20, 2015December 23, 2015 by David Dickinson

Amazing Views of Today’s Total Solar Eclipse From Earth… and Space

There’s an old Robert Heinlein saying that goes “climate is what you expect, weather is what you get,” And the weather certainly kept folks guessing right up until the start of today’s eclipse. And though much of the UK and tracks along the Faroe Islands were clouded out, folks who made the trek up to Svalbard were treated to a fine view of totality, while observers across Europe caught stages of the eclipse through its partial phases. Many more managed to capture glimpses of the eclipse thanks to our good friends over at Slooh and the Virtual Telescope project.

Here’s a quick sampling of images that have come our way thus far… we’ll be dropping in more as they become available from far flung corners of the globe and beyond:

Totality! Captured from the (thankfully sunny) Svalbard Islands. Credit and Copyright: Tony Hoffman.

Practicing solar eclipse observing safety… Credit and copyright: @johnmason1971

Though the live feed from the International Space Station was unavailable as the astros flirted with the Moon’s umbra, the crew did manage to get some quick shots of the eclipse from low Earth orbit:

They caught it! The eclipse captured from the International Space Station courtesy of @astrosamantha.

The umbra touches down at the start of the total solar eclipse as seen from the ISS. Credit: @Astrosamantha

And while the fake “eclipse seen from SPACE!!!” image made its predictable rounds, ESA’s solar observing Proba-2 spaccraft caught the eclipse from space for real:

No word yet if anyone caught the ‘money shot’ of the International Space Station transiting the Sun during the eclipse as seen from southern Spain.

UPDATE: Scratch that… Theirry Legault did indeed capture the ISS transiting the partially eclipsed Sun:

Awesome!

Totality from a balloon (!) over Svalbard. Courtesy and Credit: zero2infinity. — Totality from a balloon (!) over Svalbard. The team also has an exciting indiegogo project and hopes to make a film of the eclipse. Courtesy and Credit: @flyabloon/zero2infinity.

And while many observers and events were clouded out, many still noted the drop in ambient light levels.

The Sun was relatively blank during the eclipse, with one lone sunspot group currently turned Earthward saving us from spotlessness.

As of this writing, more eclipse pics are still pouring in. Watch this space, as many eclipse chasers —especially those who traveled to distant Svalbard to witness totality in person — are still making their way in from the field and are no doubt hunting for stable internet connections as we speak.

Awaiting clear skies on the roof of the Anton Pannekoek Institute for Astronomy at the University of Amsterdam in the Netherlands. Credit and copyright: @Whereisyvette

And as always, the big question after every eclipse is: when’s the next one? Well, the next total solar occurs over Southeast Asia on March 9th, 2016, and the very next solar eclipse is a partial over South Africa on Sept 13 2015. And North America gets to see another total lunar eclipse in the ongoing tetrad in just two weeks on April 4th, 2015… and we’re well inside two years away now from the total solar eclipse spanning the continental united States on August 21st 2017!

Let the first of two eclipse seasons for 2015 begin!

Read Dave Dickinson’s eclipse-fueled scifi tales Shadowfall and Exeligmos.

Update: although it was cloudy, Marco Langbroek did indeed catch the drop in light levels over the Netherlands:

And check out this amazing Vine of the dark umbra of the Moon crossing the North Atlantic courtesy of Meteosat-9:

Wowsa!

And sometimes, the simplest shots are the easiest to get out over social media immediately, be it at a rocket launch or during a solar eclipse:

A back of the camera shot of the eclipse as seen from northern Scotland. Credit: Edwin Quail.

There also been no word as of yet how Germany’s solar power grid fared during the eclipse, though it will be interesting to see what possible data was generated during the partial phases for future planning.

Partial phases of the solar eclipse today as seen from the United Kingdom. Credit and copyright: Sarah and Simon Fisher.

It was truly inspiring to see how many folks captured images and filled our feeds this morning with pictures of today’s eclipse.

The partial eclipse peeks out from behind the clouds over the Greek Embassy . Credit and copyright: clausdm @cldm_ish

Can’t wait til 2017? NASA’s New Horizons spacecraft is set give us a total solar eclipse from the edge of the solar system this July when it flies through the shadows of Pluto and its giant moon, Charon:

An artist's concept of New Horizons in the shadow on Pluto. Credit: NASA/JPL. — An artist’s concept of New Horizons in the shadow on Pluto. Credit: NASA/JPL.

Hey, maybe if we colonize Pluto by 2017 AD, we could witness said eclipses… in person, once every 6 days:

“Pluto One,” anyone?

Parallax in action: the view from Lahore Pakistan vs Slooh's view shortly before totality. Credit: Roshaan. Lahore Astronomical Society, Pakistan. — Parallax in action: the view from Lahore Pakistan vs Slooh’s view shortly before totality. Credit: Roshaan.
Lahore Astronomical Society, Pakistan.

A 6% partial solar eclipse as seen from Israel. Credit and copyright: Gadi Eidelheit.

The March 20, 2015 solar eclipse taken from Malta with a PST solar telescope in H-alpha. Credit and copyright: Leonard Mercer.

March 17, 2015December 23, 2015 by David Dickinson

Slender Moonspotting, Occultations, Daytime Planets and More

One of nature’s grandest ‘occultations’ of all is coming right up this Friday, as the Moon passes in front of the Sun for viewers in the high Arctic for a total solar eclipse. And although 99.999+% percent of humanity will miss totality, everyone can trace the fascinating path of the Moon as it moves back into the evening sky this weekend.

As of this writing, it looks like the fickle March weather is going to keep us guessing right up to eclipse day. Fear not, as the good folks over at the Virtual Telescope Project promise to bring us views of the eclipse live. Not only does this eclipse fall on the same day as the start of astronomical spring in the northern hemisphere known as the vernal (northward) equinox, but it also marks the start of lunation 1141.

Ever try hunting for the slender crescent Moon in the dawn or dusk sky? The sport of thin Moon-spotting on the days surrounding the New Moon can push visual skills to the very limit. Binoculars are your friend in this endeavor, as you sweep back and forth attempting to see the slim fingernail of a Moon against the low contrast background sky. Thursday morning March 19^th provides a great chance for North American observers to spy an extremely thin Moon about 24 hours prior to Friday’s eclipse.

Unfortunately, most of North America misses the eclipse, though folks on the extreme east coast of Newfoundland might see a partially eclipsed sunrise if the day dawns clear.

The Moon will first be picked up in the evening sky post-eclipse this weekend. On Friday evening, folks in the southern United States might just be able to spy a 15 hour old Moon with optical assistance if skies are clear.

As the Moon fattens, expect to see it at its most photogenic as Ashen light or Earthshine illuminates its nighttime side. What you’re seeing is sunlight from the Earth being reflected back in a reverse (waning gibbous) phase as seen from the earthward side of the Moon. The prominence of Earthshine can vary depending on the amount of cloud and snow cover currently turned moonward, though of course, if it’s cloudy from your location, you won’t see a thing…

Watch that Moon over the coming weeks, as it has a date with destiny.

The Moon occults (passes in front of) two planets and one bright star in the coming week. First up is an occultation of Uranus on March 21^st at around 11:00 UT/7:00 AM EDT. Sure, this one is for the most part purely academic and unobservable, as it occurs over central Africa in the daytime and is only 15 degrees east of the Sun. Still, if you can pick up the Moon on the evenings of March 20^th or March 21^st, you might just be able to spy nearby Uranus shining at +6^th magnitude nearby before it heads towards solar conjunction on April 6th.

Next, the Moon occults Mars on March 21^st at 22:00 UT/6:00 PM EDT for the southern Pacific coast of South America. North America will see an extremely close photogenic pairing of Luna and the Red Planet. This is one of seven occultations of a naked eye planet by the Moon for 2015, and the first of two for Mars for the year, the next falling on December 6^th.

Next up, the Moon has a tryst with brilliant Venus, passing 2.8 degrees from the Cytherean world on March 22nd. Can you spy -4th magnitude Venus near the two day old Moon before sunset? This is the stuff that has inspired astronomically-themed flags and skewed emoticon ‘smiley face conjunctions’ of yore, including the close pairing of Mars, Venus and the Moon seen worldwide last month.

Next up, the 30% illuminated Moon occults the bright star Aldebaran for Alaskan viewers at dusk on March 25^th. This is the third occultation of the star by the Moon in the ongoing cycle, and to date, no one has, to our knowledge, successfully caught an occultation of Aldebaran in 2015… could this streak be broken next week?

And speaking of daytime planet-spotting, Jupiter will sit only five degrees south of the waxing gibbous Moon on the evening of March 30^th. Can you spy the giant planet near the daytime Moon in the afternoon sky using binocs? And finally, watch that Moon, as it heads for the third total lunar eclipse of the last 12 months visible from the Americas and the Pacific region on the morning of April 4^th…

More to come!

March 12, 2015December 23, 2015 by David Dickinson

Will the March 20th Total Solar Eclipse Impact Europe’s Solar Energy Grid?

The first eclipse of 2015 is coming right up on Friday, March 20^th, and may provide a unique challenge for solar energy production across Europe.

Sure, we’ve been skeptical about many of the websites touting a ‘blackout’ and Y2K-like doom pertaining to the March 20th total solar eclipse as of late. And while it’s true that comets and eclipses really do bring out the ‘End of the World of the Week’ -types across ye ole web, there’s actually a fascinating story of science at the core of next week’s eclipse and the challenge it poses to energy production.

But first, a brief recap of the eclipse itself. Dubbed the “Equinox Eclipse,” totality only occurs over a swath of the North Atlantic and passes over distant Faroe and Svalbard Islands. Germany and central Europe can expect an approximately 80% partially obscured Sun at the eclipse’s maximum.

We wrote a full guide with the specifics for observing this eclipse yesterday. But is there a cause for concern when it comes to energy production?

A power grid is a huge balancing act. As power production decreases from one source, other sources must be brought online to compensate. This is a major challenge — especially in terms of solar energy production.

Residential solar panels in Germany. Credit: Wikimedia Commons/ Sideka Solartechnik.

Germany currently stands at the forefront of solar energy technology, representing a whopping quarter of all solar energy capacity installed worldwide. Germany now relies of solar power for almost 7% of its annual electricity production, and during the sunniest hours, has used solar panels to satisfy up to 50% of the country’s power demand.

We recently caught up with Barry Fischer to discuss the issue. Fischer is the Head Writer at Opower, a software company that uses data to help electric and gas utilities improve their customer experience. Based on Opower’s partnerships with nearly 100 utilities worldwide, the company has amassed the world’s largest energy dataset of its kind which documents energy consumption patterns across more than 55 million households around the globe.

A study published last week by Opower highlights data from the partial solar eclipse last October over the western United States. There’s little historical precedent for the impact that an eclipse could have on the solar energy grid. For example, during the August 11^th, 1999 total solar eclipse which crossed directly over Europe, less than 0.1% of utility electricity was generated using solar power.

What they found was intriguing. Although the 2014 partial solar eclipse only obscured 30 to 50% of the Sun, solar electric production dropped over an afternoon span of nearly three hours before returning to a normal pattern.

Examining data from 5,000 solar-powered homes in the western United States, Opower found that during the eclipse those homes sent 41% less electricity back to the grid than normal. Along with a nearly 1,000 megawatt decline in utility-scale solar power production, these drop-offs were compensated for by grid operators ramping up traditional thermal power plants that were most likely fueled by natural gas.

No serious problems were experienced during the October 23^rd, 2014 partial solar eclipse in terms of solar electricity production in the southwestern United States, though it is interesting to note that the impact of the eclipse on solar energy production could be readily detected and measured.

How does the drop and surge in solar power output anticipated for the March 20^th eclipse differ from, say, the kind presented by the onset of night, or a cloudy day? “The impact of an eclipse can register broadly – and unusually rapidly – across an entire region,” Fischer told Universe Today. On a small scale, one area many be cloudy, while on a larger regional scale, other areas of clear or partly sunny skies can compensate. An eclipse — even a partial one — is fundamentally different, because the sudden onset and the conclusion are relatively uniform over a large region.

The March 20^th event offers an unprecedented chance to study the effects of an eclipse on large-scale solar production up close. A study (in German) by the University of Applied Sciences in Berlin suggests that solar power production will fall at a rate 2.7 times faster than usual as the eclipse progresses over a span of 75 minutes. This is the equivalent of switching off one medium-sized power plant per minute.

The anticipated slingshot might be just as challenging, as 18 gigawatts of power comes back online at the conclusion of the eclipse in just over an hour. And as opposed to the 2014 eclipse over the U.S. which ended towards sunset, the key rebound period for the March 20^th eclipse will be around local noon and during a peak production time.

Fischer also noted that “the second half of the partial solar eclipse will also pose a notable challenge” for the grid, as it is flooded with solar power production 3.5 times faster than normal. This phenomenon could also serve as a great model for what could occur daily on a grid that’s increasingly solar power reliant in the future, as energy production ramps up daily at sunrise. Such a reality may be only 15 years away, as Germany projects installed solar capacity to top 66 gigawatts by 2030.

What’s the anticipated impact projected for a future eclipse such as, say, the 2017 and 2024 total solar eclipses over the U.S.?

This eclipse may serve as a great dry run for modeling what could occur as reliance on solar energy production grows.

Such is the modern technical society we live in. It’s fascinating to think that eclipses aren’t only a marvelous celestial spectacle, but their effects on power production may actually serve as a model for the smart grids of tomorrow.

March 11, 2015December 23, 2015 by David Dickinson

A Complete Guide to the March 20th Total Solar Eclipse

The first of two eclipse seasons for the year is upon us this month, and kicks off with the only total solar eclipse for 2015 on Friday, March 20^th.

And what a bizarre eclipse it is. Not only does this eclipse begin just 15 hours prior to the March equinox marking the beginning of astronomical spring in the northern hemisphere, but the shadow of totality also beats path through the high Arctic and ends over the North Pole.

Already, umbraphiles — those who chase eclipses — are converging on the two small tracts of terra firma where the umbra of the Moon makes landfall: the Faroe and Svalbard islands. All of Europe, the northern swath of the African continent, north-central Asia and the Middle East will see a partial solar eclipse, and the eclipse will be deeper percentage-wise the farther north you are .

2015 features four eclipses in all: two total lunars and two solars, with one total solar and one partial solar eclipse. Four is the minimum number of eclipses that can occur in a calendar year, and although North America misses out on the solar eclipse action this time ’round, most of the continent gets a front row seat to the two final total lunar eclipses of the ongoing tetrad on April 4^th and September 28^th.

How rare is a total solar eclipse on the vernal equinox? Well, the last total solar eclipse on the March equinox occurred back in 1662 on March 20^th. There was also a hybrid eclipse — an eclipse which was annular along a portion of the track, and total along another — on March 20^th, 1681. But you won’t have to wait that long for the next, as another eclipse falls on the northward equinox on March 20^th, 2034.

Note that in the 21^st century, the March equinox falls on March 20^th, and will start occasionally falling on March 19^th in 2044. We’re also in that wacky time of year where North America has shifted back to ye ‘ole Daylight Saving (or Summer) Time, while Europe makes the change after the eclipse on March 29^th. It really can wreak havoc with those cross-time zone plans, we know…

The March 20^th eclipse also occurs only a day after lunar perigee, which falls on March 19^th at 19:39 UT. This is also one of the closer lunar perigees for 2015 at 357,583 kilometres distant, though the maximum duration of totality for this eclipse is only 2 minutes and 47 seconds just northeast of the Faroe Islands.

This eclipse is number 61 of 71 in solar saros series 120, which runs from 933 to 2754 AD. It’s also the second to last total in the series, with the final total solar eclipse for the saros cycle occurring one saros later on March 30^th, 2033.

And speaking of obscure eclipse terminology, check out this neat compendium we came across in research. What’s an Exeligmos? How many Heptons are in a Gregoriana?

The 462 kilometre wide path of the eclipse touches down south of Greenland at 9:13 UT at sunrise, before racing across the North Atlantic towards the pole and departing the Earth at 10:21 UT. The sedate partial phases for the eclipse worldwide start at 7:40 UT, and run out to 11:51 UT.

What would it look like to sit at the North Pole and watch a total solar eclipse on the first day of Spring? It would be a remarkable sight, as the disk of the Sun skims just above the horizon for the first time since the September 2014 equinox. Does this eclipse occur at sunrise or sunset as seen from the pole? It would be a rare spectacle indeed!

Alas, this unique view from the pole will more than likely go undocumented. A similar eclipse was caught in 2003 from the Antarctic, and a few intrepid eclipse chasers, including author David Levy did manage to make the journey down under to witness totality from the polar continent.

Safety is paramount when observing the Sun and a solar eclipse. Eye protection is mandatory during all partial phases across Europe, northern Asia, North Africa and the Middle East. A proper solar filter mask constructed of Baader safety film is easy to construct, and should fit snugly over the front aperture of a telescope. No. 14 welder’s goggles are also dense enough to look at the Sun, as are safety glasses specifically designed for eclipse viewing. Observing the Sun via projection or by using a pinhole projector is safe and easy to do.

Weather is always the big variable in the days leading up to any eclipse. Unfortunately, March in the North Atlantic typically hosts stormy skies, and the low elevation of the eclipse in the sky may hamper observations as well. From the Faroe Islands, the Sun sits 18 degrees above the horizon during totality, while from the Svalbard Islands it’s even lower at 12 degrees in elevation. Much of Svalbard is also mountainous, making for sunless pockets of terrain that will be masked in shadow on eclipse day. Mean cloud amounts for both locales run in the 70% range, and the Eclipser website hosts a great in-depth climatology discussion for this and every eclipse.

But don’t despair: you only need a clear view of the Sun to witness an eclipse!

Solar activity is also another big variable. Witnesses to the October 23^rd, 2014 partial solar eclipse over the U.S. southwest will recall that we had a massive and very photogenic sunspot turned Earthward at the time. The Sun has been remarkably calm as of late, though active sunspot region 2297 is developing nicely. It will have rotated to the solar limb come eclipse day, and we should have a good grasp on what solar activity during the eclipse will look like come early next week.

And speaking of which: could an auroral display be in the cards for those brief few minutes of totality? It’s not out of the question, assuming the Sun cooperates. Of course, the pearly white corona of the Sun still gives off a considerable amount of light during totality, equal to about half the brightness of a Full Moon. Still, witnessing two of nature’s grandest spectacles — a total solar eclipse and the aurora borealis — simultaneously would be an unforgettable sight, and to our knowledge, has never been documented!

We also put together some simulations of the eclipse as seen from Earth and space:

Note that an area of southern Spain may witness a transit of the International Space Station during the partial phase of the eclipse. This projection is tentative, as the orbit of the ISS evolves over time. Be sure to check CALSky for accurate predictions in the days leading up to the eclipse.

Can’t make it to the eclipse? Live in the wrong hemisphere? There are already a few planned webcasts for the March 20^th eclipse:

–Astronomia Practica plans to post photos in near real time of the eclipse from northern Scotland.

-Slooh has plans to broadcast the eclipse from the Faroe Islands.

-And here’s another webcast from the Faroe Islands and the path of totality courtesy of Kringvarp Føroya:

-Here’s another broadcast planned of the partial stages of the eclipse as seen from the UK.

-And our friends over at the Virtual Telescope Project also plans on webcasting the solar eclipse:

… and speaking of which, there’s also an exciting new Kickstarter project entitled Chasing Shadows which is headed to the Arctic to follow veteran eclipse chaser Geoff Sims (@beyond_beneath of Twitter):

And stay tuned, as North America and the Pacific region will witness another total lunar eclipse on April 4^th 2015. And we’ve only got one more total solar eclipse across Southeast Asia in 2016 before the total solar eclipse of August 21^st 2017 spanning the U.S.

Let the first eclipse season of 2015 begin!

Next… how will the solar eclipse affect the European solar grid? Expect an article on just that soon!

Be sure to send those eclipse pics in to Universe Today.
Read Dave Dickinson’s tales of eclipse sci-fi, including Exeligmos, Shadowfall, and much more.

March 3, 2015December 23, 2015 by David Dickinson

The Mini-Moon Cometh: Catch the Smallest Full Moon of 2015 This Thursday

Supermoons. Blood Moons. Moons both Black and Blue… by now, you’d think that there was nothing new under the Sun (or Moon, as it were) when it comes to new unofficial lunar terminology.

Sure, the Moon now seems more colorful than controversial viral dress shades. Love it or loathe it, the Internet can sure set a meme in motion. And this week’s Full Moon on Thursday evening offers up one of our faves, as the most distant Full Moon of 2015 occurs on March 5th. Yup, the Mini-Moon is indeed once again upon us, a time when the Full Moon appears slightly smaller than usual as seen from the Earth. But can you really tell the difference?

The third Full Moon of the year occurs this week on Thursday, March 5th. Also known as the Worm or Sap Moon by the Algonquin tribes of New England, the moment of Full phase occurs at 18:07 Universal Time (UT) or 1:07 PM Eastern Standard Time (EST). This is also just over 10 hours after apogee, which occurs at 7:36 UT/2:36 AM EST. This month’s apogee is also an exceptionally distant one, measuring 406,385 kilometres from the center of the Earth to the center of the Moon. This is just 80 kilometres shy of the most distant apogee of 2015 on September 14^th, which occurs when the Moon is near New phase.

Can you spy Jupiter next to the waxing gibbous Moon *before* sunset tonite? Credit: Stellarium.

Apogee for the Moon ranges from 404,000 to 406,700 kilometres distant, and the Full Moon appears 29.3 arc minutes across near apogee versus 34.1’ across near perigee as seen from the Earth.

This is also the closest apogee near a Full Moon time-wise until January 27^th, 2032.

What is a Mini-Moon? As with a Supermoon, we prefer simply defining a Mini-Moon as a Full Moon which occurs within 24 hours of apogee. That’s much more definitive in our book rather than the cryptic and often cited ‘within 90% of its orbit’ refrain for Supermoons.

And speaking of which, we’ve got three ‘Super’ Full Moons in 2015, with the very closest Super (Duper?) Full Moon occurring within an hour of perigee on September 28^th during the final total lunar eclipse of the ongoing tetrad… what will the spin doctors of the Internet make of this? A ‘Super Duper Blood Moon,’ anyone?

The path of the Moon this week also takes it towards the Fall equinoctial point in the astronomical constellation of Virgo, as it crosses Leo and nicks the corner of the non-zodiacal constellation Sextans. The Moon reaches Full two weeks prior to the Vernal Equinox, which falls this year on March 20^th. Keep an eye on the Moon, as the first eclipse of 2015 and this year’s only total solar eclipse also occurs just 13 hours prior to the equinox for observers in the high Arctic. (More on that next week).

Can’t wait til Thursday? Tonight, observers across Canada, northern Maine, and Europe will see a fine occultation of the star Acubens (a.k.a. Alpha Cancri) by the 94% illuminated waxing gibbous Moon:

Alpha Cancri is 175 light years distant, and folks living along the U.S./Canadian border will be treated to a fine grazing occultation as the double star plays hide and seek along the limb of the Moon. This is number 17 in an ongoing series of 21 occultations of the star by the Moon stretching out until June 20th, 2015. There’s a wide separation of 11” between the star’s A and B components, and there are suspicions from previous lunar occultations that Alpha Cancri A may itself be a double star as well.

We caught a similar occultation of the star Lambda Geminorum by the Moon this past Friday:

Ever feel sorry for moonless Venus? This Wednesday night also offers a chance to spy Venus with a brief ‘pseudo-moon,’ as +6^th magnitude Uranus passes just 15’ — less than half the apparent diameter of a Full Moon — from brilliant -4^th magnitude Venus. Neith, the spurious 18th century moon of Venus lives! From the vantage point of Venus on March 4^th, the Earth and Moon would shine at magnitudes -2.3 and +1.5, respectively, and sit about 4 arc minutes apart.

The rising Full ‘Mini-Moon’ of March 5th. Credit: Starry Night Education Software.

Does the rising Full Moon look smaller to you than usual this week? While the apparent change in diameter from apogee to perigee is slight, it is indeed noticeable to the naked eye observers. Remember, the Moon is actually about one Earth radius (6,400 kilometres) more distant on the local horizon than when it’s directly overhead at the zenith. The Moon is also moving away from us at a current rate of 1-2 centimetres a year, meaning that Mini-Moons will get ever more distant in epochs hence.

Already, annular solar eclipses are currently more common than total ones by a ratio of about 11 to 9. The first annular eclipse as seen from the Earth went unheralded some time about 900 million to a billion years ago, and 1.4 billion years hence, the last total solar eclipse will occur.

The rising waxing gibbous Moon against the daytime sky. Photo by author.

Be sure to get out and enjoy the rising Mini-Moon later this week!

-Send those Mini-Moon pics in to Universe Today.

-Looking for eclipse sci-fi? Check out Dave Dickinson’s eclipse-fueled tales Exeligmos and Shadowfall.