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 24th 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.
Even in light pollution conscious Flagstaff, Arizona, the problem persists. Image credit: Dave Dickinson
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.
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 13th 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 14th at 4:10 PM EDT is the backup date if the launch does not occur on Monday.
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 13th. 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 10th, 2015. Universe Today science writer Bob King also noted that observers spotted what was probably a venting maneuver over Minnesota on the 2nd pass on the same date.
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 13th for North America include a key pass for the US northeast at 1:04UT (on the 14th)/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.
Our ad-hoc satellite imaging rig. Image credit: David Dickinson
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!
Venus glides up to the Pleiades or Seven Sisters star cluster this week. This was the view at dusk on April 4. Credit: Bob King
If you’ve ever been impressed by the brilliance of Venus or the pulchritude of the Pleiades, you won’t want to miss what’s happening in the western sky this week. Venus has been inching closer and closer to the star cluster for months. Come Friday and Saturday the two will be only 2.5° apart. What a fantastic sight they’ll make together — the sky’s brightest planet and arguably the most beautiful star cluster side by side at dusk.
No fancy equipment is required for a great view of their close conjunction. The naked eye will do, though I recommend binoculars; a pair of 7 x 35s or 10 x 50s will increase the number of stars you’ll see more than tenfold.
Map showing Venus’ path daily from April 6-15, 2015 as it makes a pass at the Pleiades. The close pairing will make for great photo opportunities . Created with Chris Marriott’s SkyMap
Just step outside between about 8:30 and 10 p.m. local time, face west and let Venus be your guide. At magnitude -4.1, it’s rivaled in brightness only by the Moon and Sun. Early this week, Venus will lie about 5° or three fingers held together at arm’s length below the Pleiades. But each day it snuggles up a little closer until closest approach on Friday. Around that time, you’ll be able to view both in the same binocular field. Outrageously bright Venus makes for a stunning contrast against the delicate pinpoint beauty of the star cluster.
Venus on April 3, 2012, when it last passed right in front of the Seven Sisters. The Pleiades is a young cluster dominated by hot, blue-white stars located 444 light years from Earth. Credit: Bob King
Every 8 years on mid-April evenings, Venus skirts the Pleiades just as it’s doing this week. Think back to April 2007 and you might remember a similar passage; a repeat will happen in April 2023. Venus’ cyclical visits to the Seven Sisters occur because the planet’s motion relative to the Sun repeats every 8 years as seen from Earth’s skies. No matter where and when you see Venus – morning or evening, high or low – you’ll see it in nearly the same place 8 years from that date.
But this is where it gets interesting. On closer inspection, we soon learn that not every Venus-Pleiades passage is an exact copy. There are actually 3 varieties:
* Close: Venus passes squarely in front of the cluster
* Mid-distance: Venus passes ~2.5° from the cluster
* Far: Venus passes ~3.5° from the cluster
The three varieties of Venus-Pleiades conjunctions . Created with Stellarium
And get this — each has its own 8-year cycle. This week’s event is part of a series of mid-distance passages that recurs every 8 years. Venus last passed directly through Pleiades in April 2012and will again in April 2020. The next most distant meeting (3.5°) happens in April 2018 and will again in 2026.
Venus circles between Earth and the Sun and experiences phases just like the Moon from our perspective. The planet is currently in gibbous phase. It reaches its greatest apparent distance from the Sun on June 6 and inferior conjunction on August 15. Credit: Wikipedia with additions by the author
Why three flavors? Venus’ orbit is tipped 3.4° to the plane of the ecliptic or the Sun-Earth line. During each of it 8-year close passages, it’s furthest north of the ecliptic and crosses within the Pleiades, which by good fortune lie about 4° north of the ecliptic. During the other two cycles, Venus lies closer to the ecliptic and misses the cluster by a few degrees.
Fascinating that a few simple orbital quirks allow for an ever-changing variety of paths for Venus to take around (and through!) one of our favorite star clusters.
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 21st 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 11th, 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
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 Telescopearticle 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
“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.
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 26th, 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 26th and a 97.4% partial lunar eclipse on November 19th.
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?
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 4th, 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:
Different orbits versus altitude. Image credit: Wikimedia Commons/Cmglee, Geo Swan
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.
Satellite constellations, including NASA’s ‘A-Train’ of sun-synchronous Earth-observing satellites. Image credit: NASA
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.
Still up there: The orbital trace of China’s space station Tiangong-1: Image credit: Orbitron
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.
The launch of SpaceX’s CRS2 resupply mission headed to the ISS. Image credit: David Dickinson
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 15th, 2012.
Space is a tough business, and it’s imperative to place things in the right orbit!
A little world is making big headlines in 2015. NASA’s Dawn spacecraft entered orbit around 1 Ceres on March 6th, 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.
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 1st 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.
Ceres, Vesta and Mars group together in 2014. Image credit and copyright: Mary Spicer
Shining at magnitude +8, April 1st 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 4th magnitude star Omega Capricorni.
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 3rd, 2017.
Ceres was discovered by Giuseppe Piazzi on the first day of the 19th century on January 1st, 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.
A 1802 publication by Piazzi describing his discovery of Ceres. Credit: Image in the Public Domain.
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.
Piazzi’s 1801 log describing the motion of Ceres against the starry background. Credit: Monatliche Correspondenz
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 21st century: August 1st, 2042, November 19th, 2058 and February 13th 2068. Mars actually transits the Sun as seen from Ceres even earlier on June 9th, 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.
The phases of a total lunar eclipse. Credit: Keith Burns / NASA
Get ready for one awesome total lunar eclipse early Saturday morning April 4th. For the third time in less than a year, the Moon dips into Earth’s shadow, its dazzling white globe turning sunset red right before your eyes. All eclipses are not-to-miss events, but Saturday’s totality will be the shortest in a century. Brief but beautiful – just like life. Read on to find out how to make the most of it.
Four total lunar eclipses in succession with no partials in between is called a tetrad. The April 4th eclipse is part of a tetrad that started last April and will wrap up on September 28. During the 21st century there will be eight sets of tetrads. Credit: NASA
Lunar eclipses don’t usually happen in any particular order. A partial eclipse is followed by a total is followed by a penumbral and so on. Instead, we’re in the middle of a tetrad, four total eclipses in a row with no partials in between. The final one happens on September 28. Even more remarkable, part or all of them are visible from the U.S. Tetrads will be fairly common in the 21st century with eight in all. We’re lucky — between 1600 and 1900 there were none! For an excellent primer on the topic check out fellow Universe Today writer David Dickinson’s “The Science Behind the Blood Moon Tetrad“.
The partially eclipsed Moon on October 8, 2015. For skywatchers across the eastern half of North America, this is about how the Moon will appear shortly before it sets. Those living further west will see totality. Credit: Bob King
Lots of people have taken to calling the tetrad eclipses Blood Moons, referring to the coppery color of lunar disk when steeped in Earth’s shadow and the timing of both April events on the Jewish Passover. Me? I prefer Bacon-and-Eggs Moon. For many of us, the eclipse runs right up till sunrise with the Moon setting in bright twilight around 6:30 a.m. What better time to enjoy a celebratory breakfast with friends after packing away your gear?
Map showing where the April 4 lunar eclipse will be penumbral, partial and total. World map shown in inset. Credit: Larry Koehn / shadowandsubstance.com Inset: Fred Espenak
But seriously, Saturday morning’s eclipse will prove challenging for some. While observers in far western North America, Hawaii, Japan, New Zealand and Australia will witness the entire event, those in the mountain states will see the Moon set while still in totality. Meanwhile, skywatchers in the Midwest and points East will see only the partial phases in a brightening dawn sky. Here are the key times of eclipse events by time zone:
A total lunar eclipse occurs only during full moon phase when the Sun, Earth and Moon lie in a straight line. The Moon slips directly behind Earth into its shadow. The outer part of the shadow or penumbra is a mix of sunlight and shadow and only partially dark. From the inner shadow, called the umbra, the Sun is completely blocked from view. A small amount of sunlight refracted or bent by Earth’s atmosphere into the umbra, spills into the shadow, coloring the eclipsed Moon red.
Eclipse Events EDT CDT MDT PDT
Penumbra eclipse begins
5:01 a.m.
4:01 a.m.
3:01 a.m.
2:01 a.m.
Partial eclipse begins
6:16 a.m.
5:16 a.m.
4:16 a.m.
3:16 a.m.
Total eclipse begins
——–
——–
5:58 a.m.
4:58 a.m.
Greatest eclipse
——–
——–
6:00 a.m.
5:00 a.m.
Total eclipse ends
——–
——–
6:03 a.m.
5:03 a.m.
Partial eclipse ends
———
——–
——–
6:45 a.m.
Penumbra eclipse ends
———
———
——–
——–
* During the penumbral phase, shading won’t be obvious until ~30 minutes before partial eclipse.
Partial eclipse, when the Moon first enters Earth’s dark umbral shadow, begins at 5:16 a.m. CDT near the start of morning twilight. Totality begins at 6:58 a.m. with the Moon already set for the eastern half of the country. Credit: Fred Espenak
This eclipse will also be the shortest total eclipse of the 21st century; our satellite spends just 4 minutes and 43 seconds inside Earth’s umbra or shadow core. That’s only as long as a typical solar eclipse totality. Ah, the irony.
Better have your camera ready or you’ll miss it. The maps below show the maximum amount of the Moon visible shortly before setting from two eastern U.S. cities and the height of the totally eclipsed Moon from two western locations. Click each panel for more details about local circumstances.
The Earth’s shadow will take only a small bite out of the Moon before sunrise (6:47 a.m.) as seen from Washington D.C. From all mainland U.S. locations Virgo’s brightest star Spica will appear about 10° to the left of the Moon. Source: StellariumHere’s the view from Chicago where sunrise occurs at 6:27 a.m. Source: StellariumTotality will be visible From Denver, Colorado with the Moon low in the western sky in morning twilight. Sunrise is 6:42 a.m. Source: StellariumSeattle and the West Coast get a great view of totality in a dark sky. The final partial phases will also be visible. Sunrise there is 6:40 a.m. Source: Stellarium
Now that you know times and shadow coverage, let’s talk about the fun part — what to look for as the event unfolds. You’ll need to find a location in advance with a good view to the southwest as most of the action happens in that direction. Once that detail’s taken care of and assuming clear weather, you can kick back in a folding chair or with your back propped against a hillside and enjoy.
During the early partial phases you may not see the shadowed portion of the Moon with the naked eye. Binoculars and telescopes will show it plainly. But once the Moon is about 50% covered, the reddish-orange tint of the shadowed half becomes obvious. During total eclipse (right), the color is intense. Credit: Jim Schaff
The entire eclipse can be enjoyed without any optical aid, though I recommend a look through binoculars now and then. The eclipsed Moon appears distinctly three-dimensional with only the slightest magnification, hanging there like an ornament among the stars. The Earth’s shadow appears to advance over the Moon, but the opposite is true; the Moon’s eastward orbital motion carries it deeper and deeper into the umbra.
Nibble by nibble the sunlit Moon falls into shadow. By the time it’s been reduced to half, the shaded portion looks distinctly red even to the naked eye. Notice that the shadow is curved. We live on a spherical planet and spheres cast circular shadows. Seeing the globe of Earth projected against the Moon makes the roundness of our home planet palpable.
A simulated view looking back at Earth from the Moon during a total lunar eclipse on Earth. Sunlight grazing Earth’s circumference gets filtered by our atmosphere in exactly the same way the setting or rising Sun looks red. All the cooler colors have been scattered away by air and Red light, bent into the umbra by atmospheric refraction, bathes the lunar surface in red. As you might have guessed, when we see a total lunar eclipse on Earth, lunar inhabitants see a total eclipse of the Sun by Earth. Source: Stellarium
When totality arrives, the entire lunar globe throbs with orange, copper or rusty red. These sumptuous hues originate from sunlight filtered and bent by Earth’s atmosphere into the umbral shadow. Atmospheric particles have removed all the cooler colors, leaving the reds and oranges from a billion sunrises and sunsets occurring around the planet’s circumference. Imagine for a moment standing on the Moon looking back. Above your head would hang the black disk of Earth, nearly four times the size of the Moon in our sky, ringed by a narrow corona of fiery light.
Color varies from one eclipse to the next depending on the amount of water, dust and volcanic ash suspended in Earth’s atmosphere. The December 30, 1982 eclipse was one of the darkest in decades due to a tremendous amount of volcanic dust from the eruption of the Mexican volcano El Chichon earlier that year.
The more particles and haze, the greater the light absorption and darker the Moon. That said, this eclipse should be fairly bright because the Moon does not tread deeply into Earth’s shadow. It’s in for a quick dip of totality and then resumes partial phases.
The Moon’s color can vary from yellow-orange to dark, smoky brown during totality depending on the state of the atmosphere. You can also see lots of stars in the sky right up to the Moon’s edge when it’s in Earth’s shadow. This photo from last April’s eclipse. Spica is below the Moon and Mars to the right. Credit: Bob King
It’s northern edge, located close to the outer fringe of Earth’s umbra, should appear considerably brighter than the southern, which is closer to the center or darkest part of the umbra.
Earth’s shadow exposed! When a lunar eclipse occurs at dusk or dawn we have the rare opportunity to see Earth’s shadow on the distant Moon at the same time it’s visible as a dark purple band cast on the upper atmosphere as seen here on October 8, 2015. Credit: Bob King
Besides the pleasure of seeing the Moon change color, watch for the sky to darken as totality approaches. Eclipses begin with overwhelming moonlight and washed out, star-poor skies. As the Moon goes into hiding, stars return in a breathtaking way over a strangely eerie landscape. Don’t forget to turn around and admire the glorious summer Milky Way rising in the eastern sky.
Lunar eclipses remind us we live in a Solar System made of these beautiful, moving parts that never fail to inspire awe when we look up to notice.
In case you can’t watch the eclipse from your home due to weather or circumstance, our friends at the Virtual Telescope Project and SLOOHwill stream it online.
Short time exposure of the star Sirius with the camera attached to a small telescope. I tapped the tube to make the star bounce around, recording the star's rapid color changes as it twinkled. All photos by the author
We all have cameras, and the sky’s an easy target, so why not have a little fun? Ever since I got my first camera at age 12 I wanted to shoot time exposures of the night sky. That and a tripod are all you need. Presented here for your enjoyment are a few oddball and yet oddly informative images of stars and planets. Take the word “art” loosely!
Colorless mess. This is the companion to the Sirius image and shows Jupiter through the telescope. Notice how blandly white it appears. That’s because Jupiter’s disk is large enough to not show twinkling (and color changes) caused by atmospheric turbulence as in the case of point-like Sirius. Credit: Bob KingPleasing parallels. Orion’s Belt and Sword trail in this time exposure made with a 200mm lens. The fuzzy pink streak is the Orion Nebula. They’re trails are nearly parallel because the stars all lie close to the celestial equator and were crossing the meridian at the time. Credit: Bob KingStar Trek Effect. I centered Jupiter in the viewfinder, pressed the shutter button for a 20-second time exposure and slowly hand-zoomed the lens from 70mm to 200mm. It took a few tries because I was shooting blind, but even the rejects weren’t too bad. Credit: Bob KingColor by Fog. The colors of stars are accentuated when spread into a glowing disk by fog or light cloud. Orion is at right with the crescent moon at lower left. Credit: Bob KingSnow flies. During a time exposure taken on a snowy but partly cloudy night, snowflakes, illuminated by a yard light, streak about beneath a Full Moon earlier this winter. Credit: Bob KingStuttering Stars. For this image of the Big Dipper the camera was on a tracking mount. I left the shutter open for about 25 minutes with the tracking turned off so the stars would trail. Then the lens was covered with a black cloth for a few minutes to create a gap between this exposure and the next. After the cloth was removed, I started the tracking motor and kept the exposure running for a few minutes. A diffusion filter was used in front of the lens to soften and enlarge the brightest stars. Credit: Bob King
Nova Sagittarii 2015 No. 2 photographed this morning when it was easily visible to the naked eye at magnitude +4.4. The nova has been on the upswing since its discovered less than a week ago. Credit: Bob King
Great news about that new nova in Sagittarius. It’s still climbing in brightness and now ranks as the brightest nova seen from mid-northern latitudes in nearly two years. Even from the northern states, where Sagittarius hangs low in the sky before dawn, the “new star” was easy to spy this morning at magnitude +4.4.
While not as rare as hen’s teeth, novae aren’t common and those visible without optical aid even less so. The last naked eye nova seen from outside the tropics was V339 Del (Nova Delphini), which peaked at +4.3 in August 2013. The new kid on the block could soon outshine it if this happy trend continues.
This view shows the sky facing south-southeast shortly before the start of dawn in late March from the central U.S. The nova is centrally located within the Teapot. Source: Stellarium
Now bearing the official title of Nova Sagittarii 2015 No. 2, the nova was discovered on March 15 by amateur astronomer and nova hunter John Seach of Chatsworth Island, NSW, Australia. At the time it glowed at the naked eye limit of magnitude +6. Until this morning I wasn’t able to see it with the naked eye, but from a dark sky site, it’s there for the picking. So long as you know exactly where to look.
The chart and photo above will help guide you there. At the moment, the star’s about 15° high at dawn’s start, but it rises a little higher and becomes easier to see with each passing day. Find your sunrise time HERE and then subtract an hour and 45 minutes. That will bring you to the beginning of astronomical twilight, an ideal time to catch the nova at its highest in a dark sky.
Use this AAVSO chart to pinpoint the nova’s location and also to help you estimate its brightness. Numbers shown are star magnitudes with the decimal points omitted. Credit: AAVSO
To see it with the naked eye, identify the star with binoculars first and then aim your gaze there. I hope you’ll be as pleasantly surprised as I was to see it. To check on the nova’s ups and downs, drop by the American Association Variable Star Observers (AAVSO) list of recent observations.
Seeing the nova without optical aid took me back to the time before the telescope when a “new star” in the sky would have been met with great concern. Changes in the heavens in that pre-telescopic era were generally considered bad omens. They were also thought to occur either in Earth’s atmosphere or within the Solar System. The universe has grown by countless light years since then. Nowadays we sweat the small stuff – unseen asteroids – which were unknown in that time.
AAVSO light curve showing the nova’s brightening since discovery. Dates are along the bottom, magnitudes at left. If the trend continues, Nova Sgr #2 could outshine the 2013 nova in Delphinus very soon. Credit: AAVSO
Novae occur in binary star systems where a tiny but gravitationally powerful white dwarf star pulls gases from a close companion star. The material piles up in a thin layer on the dwarf’s hot surface, fuses and burns explosively to create the explosion we dub a nova. Spectra of the expanding debris envelope reveal the imprint of hydrogen gas and as well as ionized iron.
Artist’s view of a nova with an expanding cloud of debris surrounding the central fireball emitting red hydrogen-alpha light.
Shortly after discovery, the nova’s debris shell was expanding at the rate of ~1,740 miles per second (2,800 km/sec) or more than 6.2 million mph (10 million mph). It’s since slowed to about half that rate. Through a telescope the star glows pale yellow but watch for its color to deepen to yellow orange and even red. Right now, it’s still in the fireball phase, with the dwarf star hidden by an envelope of fiery hydrogen gas.
As novae evolve, they’ll often turn from white or yellow to red. Emission of deep red light from hydrogen atoms – called hydrogen alpha – gives them their warm, red color. Hydrogen, the most common element in stars, gets excited through intense radiation or collisions with atoms (heat) and re-emits a ruby red light when it returns to its rest state. Astronomers see the light as bright red emission line in the star’s spectrum. Spectra of the nova show additional emission lines of hydrogen beta or H-beta (blue light emitted by hydrogen) and iron.
There are actually several reasons why novae rouge up over time, according to former AAVSO director Arne Henden:
“Energy from the explosion gets absorbed by the surrounding material in a nova and re-emitted as H-alpha,” said Henden. Not only that but as the explosion expands over time, the same amount of energy is spread over a larger area.
“The temperature drops,” said Henden, “causing the fireball to cool and turn redder on its own.” As the eruption expands and cools, materials blasted into the surrounding space condense into a shell of soot that absorbs that reddens the nova much the same way dusty air reddens the Sun.
Nova Sagittarii’s current pale yellow color results from seeing a mix of light – blue from the explosion itself plus red from the expanding fireball. As for its distance from Earth, I haven’t heard, but given that the progenitor star was 15th magnitude or possibly fainter, we’re probably talking in the thousands of light years.
Wide view of the Sagittarius-Scorpius region with some of the brighter star clusters and nebulae labeled for binocular browsing. Credit: Bob King
In an earlier article on the nova’s discovery I mentioned taking a look at Saturn as long as you made the effort the get up early. Here’s a photo of the Sagittarius region you can use to help you further your dawn binocular explorations. The entire region is rich with star clusters and nebula, many of which were cataloged long ago by French astronomer Charles Messier, hence the “M” numbers.
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. 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.
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!
An Iphone capture of the eclipse. Credit and copyright: @zubenelganubi
Let the first of two eclipse seasons for 2015 begin!
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.
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.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.
