David Dickinson, Author at Universe Today

April 14, 2015December 23, 2015 by David Dickinson

Help Researchers Track Comet 67/P Through Perihelion

Calling all light-bucket scope owners: the folks at the European Space Agency want to enlist you in the quest to monitor Comet 67P/Churyumov-Gerasimenko from our Earthbound perspective through perihelion later this summer.

“We are looking to bring an entire community of professional and amateur observers together,” said Rosetta Coordinator of Amateur Observations for Comet 67/P C-G Padma A. Yanamandra-Fisher in a recent press release. “When else can you observe a comet at the same time a spacecraft is viewing it at close proximity and escorting it to perihelion, and be able to correlate both sets of findings?

The Rosetta story thus far has been an amazing tale of discovery. We’ve extensively chronicled the historic approach of the Rosetta spacecraft as the rubber-duck-shaped comet grew in its view here at Universe Today. The world also held its collective breath as the Philae lander, the little washing Euro- washing machine-sized spacecraft that could, descended on to the alien surface. Heck, Philae even knocked a Kardashian out of the top trending spot worldwide, a feat in and of itself.

We also documented the Spinal Tap-esque “None more black” nature of the comet.

Prospects in 2015: As of this writing, Comet 67P/C-G is 1.9 AU from the Sun and closing. The ‘P’ in ‘67/P’ stands for ‘short term (less than 200 years) periodic,’ and the comet orbits the Sun once every 6.44 years. Perihelion for 67/P occurs on August 13^th, 2015 when the comet reaches a distance of 1.24 AU ( 191 million kilometres) from the Sun.

Discovered in 1969 by the Kiev University’s Klim Ivanovych Churyumov while examining a photograph taken by Svetlana Gerasimenko, this is the comet’s seventh apparition. Currently shining at +18th magnitude in the constellation Aquarius, Comet 67P C-G will vault up in the early morning sky for northern hemisphere observers and cross the ecliptic plane in the last week of July, at 43 degrees elongation west of the Sun.

The comet is expected to reach a maximum brightness of +11^th magnitude near perihelion. Historically, 67P – like most comets – tend to under-perform before perihelion, only to have an energetic lingering outburst phase post-perihelion.

“With each apparition we see it (67P) behave differently.” Yanamandra-Fisher said. “These legacy data sets will aid in our knowledge of this comet, especially when used in combination with the data gathered by the Rosetta spacecraft and the new ground observations made this year.”

The path of 67/P through the morning sky as seen from latitude 30 degrees north. Image credit: Starry Night Education software

Time on professional scopes is always chronically in short supply, with more astronomers and targets to observe than there are telescopes available. That’s where amateur observers come in. Many private backyard observatories have instruments that would be the envy of many a major institution. Though the press release suggests that the minimum aperture size needed to observe 67P this summer is 14-inches (35 cm), we urge 10” or 12” inch scope owners – especially those who have the latest generation of Mallincam and faint object CCD imagers – to give it a try. We’ve seen some amazing results with these, even during quick casual observing sessions such as public star parties! The Rosetta team is looking for everything from professional grade images, to sketches and visual observations with magnitude estimations.

Of course, hunting faint comets is a daunting task at best. +10^th magnitude is generally our cut-off for ‘is interesting enough to alert the public’ in terms of novae or comets, though we’ll let 67/P ‘into the club’ due to its celebrity status.

Comet 67/P from June 23rd, 2014. Image credit and copyright: Efrain Morales

To add to the challenge, the comet is only visible against a dark sky during a brief pre-dawn window. You’ll need a planetarium program (we use Starry Night Pro) to generate good finder charts down to 15^th magnitude or so. Keep in mind, comets also typically appear a bit fainter visually than stars of the same magnitude due to the fact that said brightness is spread out over a broad surface area.

ESA also has a great page with an ephemeris generator to help you in your 67/P quest.

“This is truly interactive science that people of all observing levels can participate in- from amateurs to professionals.” Yanamandra-Fischer said in closing.

Other comets to watch for in 2015 include still bright 2014 Q2 Lovejoy, C/2013 US10 Catalina, C/2014 Q1 PanSTARRS, and 19P/Borrelly.

What’ll happen as 67P approaches perihelion? Will those two gigantic lobes crack and separate as Rosetta and the world looks on? Now, I’d pay to see that!

A light bucket scope at the Bruneau Dunes observatory suitable for a faint comet quest. Image credit: David Dickinson

-Register for the Rosetta observation campaign here.

April 13, 2015December 23, 2015 by David Dickinson

Firefly Astronomy

Light makes life, and sometimes, life returns the favor. There’s nothing more magical than watching fireflies flit across a starlit field on a summer’s night. Growing up in Northern Maine, summer was an all-too swiftly passing season, and fireflies had to put on their displays in a brief profusion of frenzied activity around late July and early August before the weather turned once again towards another long harsh winter.

Fireflies remind us of the ephemeral nature of existence, that’s for sure. And they’re much more welcome by summertime campers on vigil for the August Perseids than oh, say the ubiquitous mosquito or vicious black flies…

A recent amazing capture (see the intro image) came to us courtesy of Steed Yu. Shooting from the shores of Lake Natron in Tanzania, he managed to capture an amazing composition of fireflies and those ‘fireflies of the cosmos,’ in the form of a star-dappled southern hemisphere sky.

Taken on February 24^th 2015 just south of the equator, this is simply an amazing image. Don’t forget, though it’s towards the end winter time up here in the northern hemisphere in late February, it’s the tail end of the summer south of the equator.

The photographer had this to say about his ‘Carnival of Fireflies’:

The Night of Lake Natron belongs to the stars. Without any artificial light disturbing the pure sky, one can easily see the Southern Milky Way, as well as sparkling starlights scattered in it, such as the most distinctive constellation Southern Cross and our nearest stellar neighbours Alpha Centauri. The Night of Lake Natron belongs to the firefly too. These glowing elves were flying up and down among the lush grass on both sides of a ravine stream, like a flowing “Firefly Way”, as if to contest with the Milky Way. On the quiet starry night, the fireflies held a grand carnival.

Fireflies shine through a method known as bioluminescence, producing a cold light via a chemical process using the chemical luciferin that causes their abdomen to glow. This aids mating and mate selection, and even firefly larvae have been known to glow. Other deep sea and cave-dwelling species of fish and insects have been known to use a similar signaling method in the absence of ambient light.

You can see the stars of the southern Milky Way and the Southern Cross high above the African night shining in their own particular fashion via nuclear fusion, using the proton-proton chain reaction to shed their ancient photons of light onto the nighttime scene from beyond the cold dust lanes of the Coal Sack.

We’ve managed to observe the sky from the southern hemisphere five times from three different continents over the years, and can attest that all of the ‘good stuff’ is in the southern sky, where the core of our home Milky Way galaxy arcs high overhead.

Such ‘Firefly Time-lapse Astronomy’ is as easy as parking a DSLR with a wide-field of view lens on a tripod and shooting 10-60 second time exposures. Fellow Universe Today writer Bob King wrote a piece last year on his firefly astronomy adventures.

And check out this amazing video sequence by Vincent Brady taken in the summer of 2013 from Lake of the Ozarks, Missouri:

Humans have also mastered the art of creating light and luminescence via technology as well. This has served as a way to ‘push back the night,’ and our 24 hour civilization has come to rely on this mimicry of nature as we demonstrate our prowess at illumination. This often has a cost, however, as we banish the beauty of the night sky to a distant memory. We’ve also had the dubious pleasure of observing and conducting impromptu sidewalk star parties from downtown Tampa and the Las Vegas strip, arguably some of the most light-polluted locales in the world. On such nights, only the Moon, planets and perhaps the odd bright double stars are the only viable targets.

But all is not lost. Perhaps wasteful light pollution is only an adolescent phase that civilizations go through. One SETI search strategy has even suggested that we may be able to detect ET via light pollution from alien cities on the night side of prospective planets … perhaps some race of ‘intelligent fireflies’ straight out of science fiction will use bio-chemical signaling for communication?

All great thoughts to ponder on the star-filled summer nights ahead, as fireflies swarm around us. We move that if we ever become an interstellar species that we bring the noble firefly along for the ride… but please, let’s leave light pollution and mosquitoes behind.

April 9, 2015December 23, 2015 by David Dickinson

Here’s How You Can Watch the SpaceX’s CRS-6 Mission From Your Backyard

Hunting for satellites from your backyard can be positively addicting. Sure, the Orion Nebula or the Andromeda Galaxy appear grand… and they’ll also look exactly the same throughout the short span of our fleeting human lifetimes. Since the launch of Sputnik in 1957, humans also have added their own ephemeral ‘stars’ to the sky. It’s fun to sleuth out just what these might be, as they photobomb the sky overhead. In the coming week, we’d like to turn your attention towards a unique opportunity to watch a high profile space launch approach a well-known orbiting space laboratory.

On Monday, April 13^th 2015, SpaceX will launch its CRS-6 resupply mission headed towards the International Space Station. As of this writing, the launch is set for 20:33 Universal Time (UT) or 4:33 PM EDT. This is just over three hours prior to local sunset. The launch window to catch the ISS is instantaneous, and Tuesday April 14^th at 4:10 PM EDT is the backup date if the launch does not occur on Monday.

Image credit: Andrew — Dragon chasing the ISS over Ottawa. Image credit and copyright: Andrew Symes

Of course, launches are fun to watch up-close from the Kennedy Space Center. To date, we’ve seen two shuttle launches, one Falcon launch, and the MAVEN and MSL liftoffs headed to Mars from up close, and dozens more from our backyard about 100 miles to the west of KSC. We can typically follow a given night launch right through to fairing and stage one separation with binoculars, and we once even had a serendipitous launch occur during a local school star party! We really get jaded along the Florida Space Coast, where space launches are as common as three day weekend traffic jams elsewhere.

And it’s true that you can actually tell when a launch is headed ISS-ward, as it follows the station up the US eastern seaboard along its steep 52 degree inclination orbit.

On Monday, Dragon launches 23 minutes behind the ISS in its orbit. Viewers up should be able to follow CRS-6 up the U.S. East Coast in the late afternoon sky if it’s clear.

The position of the ISS during Monday’s liftoff, plus the trace for the next two orbits, and the position of the day/night terminator at the end of the second orbit. Image credit: Orbitron

And of course, SpaceX will make another attempt Monday at landing its Falcon Stage 1 engine on a floating sea platform, known as the ‘autonomous spaceport drone ship’ (don’t call it a barge) after liftoff.

About 15-20 minutes after liftoff, Europe and the United Kingdom may catch the Dragon and Falcon S2 booster shortly after the ISS pass on the evening of April 13^th. Observers ‘across the pond’ used to frequently catch sight of the Space Shuttle and the external fuel tank shortly after launch; such a sight is not to be missed!

Spotting Dragon ‘and friends’ on early orbits may provide for a fascinating show in the evenings leading up to capture and berthing. Typically, a Dragon launch generates four objects in orbit: the Dragon spacecraft, the Falcon Stage 2 booster, and the two solar panel covers. These were very prominent to us as they passed over Northern Maine on first orbit in the pre-dawn sky on the morning of January 10^th, 2015. Universe Today science writer Bob King also noted that observers spotted what was probably a venting maneuver over Minnesota on the 2^nd pass on the same date.

Image credit: the launch of CRS-2. — The launch of CRS-2. Image credit: David Dickinson

And even after berthing, the Falcon S2 booster and solar panel covers will stay up in orbit, either following or leading the ISS for several weeks before destructive reentry.

Orbits on Monday and Tuesday leading up to capture for Dragon on Wednesday April 15th at 7:14 AM EDT/11:14 UT will be the key times to sight the pair. Capture by the CanadaArm2 will take place over the central Pacific, and the Dragon will be berthed to the nadir Harmony node of the ISS. Dragon will remain attached to the station until May 17th for a subsequent return to Earth. With the end of the U.S. Space Shuttle program in 2011, SpaceX’s Dragon is currently the only vessel with a ‘down-mass’ cargo capability, handy for returning experiments to Earth.

The first few orbits on the night of the 13^th for North America include a key pass for the US northeast at 1:04UT (on the 14^th)/9:04 PM EDT, and subsequent passes at dusk westward about 90 minutes later. NASA’s Spot the Station App usually lists Dragon passes shortly after launch, as does Heavens-Above and numerous other tracking applications. We’ll also be publishing sighting opportunities for Dragon and the ISS, along with maps on Twitter as @Astroguyz as the info becomes available.

Pre-berthing passes next week favor 40-50 degrees north for evening passes, and 40-50 degrees south for morning viewing.

Dragon/CRS-3 passes over the Netherlands. Image credit: Marco Langbroek

The International Space Station has become a busy place since its completion in 2009. To date, the station has been a port of call for the U.S. Space Shuttles, the Soyuz spacecraft with crews, and Progress, HTV, ATV and Dragon resupply craft.

The current expedition features astronaut Scott Kelly and cosmonaut Mikhail Korniyenko conducting a nearly yearlong stay on the ISS to study the effects that long duration spaceflight has on the human body. Kelley will also break the U.S. duration record by 126 days during his 342 stay aboard the station. The future may see Dragon ferrying crews to the ISS as early as 2017.

And you can always watch the launch live via NASA TV starting at 3:30 PM EDT/19:30 UT.

Don’t miss a chance to catch the drama of the Dragon spacecraft approaching the International Space Station, coming to a sky near you!

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 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!