Latest image released by NASA of the spatter of white spots in the 57-mile-wide crater on the dwarf planet Ceres. Scientists with the Dawn mission believe they're highly reflective material, likely ice. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
The latest views of Ceres’ enigmatic white spots are sharper and clearer, but it’s obvious that Dawn will have to descend much lower before we’ll see crucial details hidden in this overexposed splatter of white dots. Still, there are hints of interesting things going on here.
Comparison of the most recent photos of the white spots taken Dawn’s current 4,500 miles vs. 8,400 miles on May 4. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
The latest photo is part of a sequence of images shot for navigation purposes on May 16, when the spacecraft orbited 4,500 miles (7,200 km) over the dwarf planet. Of special interest are a series of troughs or cracks in Ceres crust that appear on either side of the crater housing the spots.
While the exact nature of the spots continues to baffle scientists, Christopher Russell, principal investigator for the Dawn mission, has narrowed the possibilities: “Dawn scientists can now conclude that the intense brightness of these spots is due to the reflection of sunlight by highly reflective material on the surface, possibly ice.”
The bright material in both photos was excavated from below the surface and deposited nearby by a 2008 impact that dug a crater about 26 feet (8 meters) in diameter. The extent of the bright patch was large enough for the Compact Reconnaissance Imaging Spectrometer for Mars, an instrument on NASA’s Mars Reconnaissance Orbiter, to obtain information confirming it as water ice. Credit: NASA/JPL-Caltech/University of Arizona
We’ve seen ice exposed by meteorite / asteroid impact before on Mars where recent impacts have exposed fresh ice below the surface long hidden by dust. In most cases the ice gradually sublimates away or covered by dust over time. But if Ceres’ white spots are ice, then we can reasonably assume they must be relatively new features otherwise they would have vaporized or sublimated into space like the Martian variety.
NASA’s Hubble Space Telescope took these images of the asteroid 1 Ceres over a 2-hour and 20-minute span, the time it takes the Texas-sized object to complete one quarter of a rotation. The observations were made in visible and in ultraviolet light. Hubble took the snapshots between December 2003 and January 2004. Credit: NASA, ESA, J. Parker, P. Thomas and L. McFadden
Much has been written – including here – that these spots are the same as those photographed in much lower resolution by the Hubble Space Telescope in 2004. But according the Phil Plait, who writes the Bad Astronomy blog, that’s false. He spoke to Joe Parker, who was part of the team that made the 2004 photos, and Parker says the Dawn spots and Hubble spots are not the same.
Could the spots have formed post-2004 or were they simply too small for Hubble to resolve them? That seems unlikely. The chances are slim we’d just happen to be there shortly after such a rare event occurred? And what happened to Hubble’s spot – did it sublimate away?
Video compiled from Dawn’s still frames of Ceres by Tom Ruen. Watch as the spots continue to reflect light even at local sunset.
Watching the still images of Ceres during rotation, it’s clear that sunlight still reflects from the spots when the crater fills with shadow at sunset and sunrise. This implies they’re elevated, and as far as I can tell from the sunrise photo (see below), the brightest spots appear to shine from along the the side of a hill or mountain. Could we be seeing relatively fresh ice or salts after recent landslides related to impact or tectonic forces exposed them to view?
Single from from the video shows the white spots shortly after sunrise. The brightest appear to be located on a central mountain peak. It’s unclear if the pair of spots below the bright pair are situated on a rise or the flat floor. Credit: NASA
Let’s visit another place in the Solar System with an enigmatic white spot, or should I say, white arc. It’s Wunda Crater on Uranus’ crater-blasted moon Umbriel. The 131-mile-wide crater, situated on the moon’s equator, is named for Wunda, a dark spirit in Aboriginal mythology. But on its floor is a bright feature about 6 miles (10 km) wide. We still don’t know what that one is either!
The moon Umbriel, 727 miles in diameter, with Wunda Crater and its bright internal ring of unknown origin. The moon’s equator is vertical in this photo. Credit: NASA
The hunt is on in the satellite tracking community, as the U.S. Air Force’s super-secret X-37B space plane rocketed into orbit today atop an Atlas V rocket out of Cape Canaveral. This marks the start of OTV-4, the X-37B’s fourth trip into low Earth orbit. And though NORAD won’t be publishing the orbital elements for the mission, it is sure to provide an interesting hunt for backyard satellite sleuths on the ground.
Previous OTV missions were placed in a 40 to 43.5 degree inclination orbit, and the current NOTAMs cite a 61 degree azimuth angle for today’s launch out of the Cape which suggests a slightly shallower 39 degree orbit. Such variability speaks to the versatile nature of the second stage Centaur motor.
A capture of the X-37B in orbit. Image credit and copyright: Luke (Catching up)
There’s also been word afoot that future X-37B missions may return to Earth at the Kennedy Space Center, just like the Space Shuttle. To date, the X-37B has only landed at Vandenberg Air Force Base in California.
But there’s also another high interest payload being released along with a flock of CubeSats aboard AFPSC-5: The Planetary Society’s Lightsail-1.
The UltraSat P-POD CubeSat dispenser. Image credit: United Launch Alliance
About the size of a loaf of bread and the result of a successful Kickstarter campaign, LightSail is set to demonstrate key technologies in low Earth orbit before the Planetary Society’s main solar sail demonstrator takes to space in 2016.
The idea of using solar wind pressure for space travel is an enticing one. A big plus is the fact that unlike chemical propulsion, a solar sail does not need to contend with hauling the mass of its own fuel. The idea of using a solar sail plus a focused laser to propel an interstellar spacecraft has long been a staple of science fiction. But light-sailing technology has had a troubled history—the Planetary Society lost its Cosmos-1 mission launched from a Russian submarine in 2001. JAXA has fared better with its Venus-bound IKAROS, also equipped with a solar sail. To date, the IKAROS solar sail is the largest that has been deployed, at 20-metres on the diagonal.
Another use for space sail technology is the commanded reentry of spacecraft at the end of their mission life, as demonstrated by NanoSail-D2 in 2011.
Prospects of seeing LightSail may well be similar to what we had hunting for NanoSail-D2. Unfolded, LightSail will be 32 square meters in size, or about 5.6 meters on a side. NanoSail-D2 measured 3.1 meters on a side, and the reflective panels on the Iridium satellites which produce brilliant Iridium flares exceeding Venus in brightness measure about the size of a large rectangular door at 1 x 3 meters. Even the Hubble Space Telescope can flare on occasion as seen from the ground if one of its massive solar arrays catches the Sun just right.
Hubble can flare too! Image credit: David Dickinson
The 39 degree orbital inclination angle will also limit visible passes to from about 45 degrees north to 45 degrees south latitude.
Hunting down X-37B and LightSail will push ground observing skills to the max. Like NanoSail-D2, LightSail probably won’t be visible to the naked eye until it flares. What we like to do is note when a faint satellite is set to pass by a bright star, then sit back with our trusty 15x 45 image-stabilized binoculars and watch. We caught sight of the ‘tool bag’ lost during an ISS EVA in 2009 in this fashion. There it was, drifting past Spica as a +7th magnitude ‘star’. The key to this method is an accurate prediction—Heavens-Above now overlays orbital satellite passes on all-sky charts—and an accurate time source. We prefer to have WWV radio running in the background, as it’ll call out the time signal so we don’t have to take our eyes off the sky.
The orbital trace of OTV-3. Image credit: Orbitron
Veteran satellite watcher Ted Molczan recently discussed the prospects for spotting LightSail once it’s deployed. “By then, the orbit will be visible from the northern hemisphere during the middle of the night. The southern hemisphere may have marginal evening passes. Note that the high area to mass ratio with the sail deployed, combined with the low perigee height, is expected to result in decay as soon as a couple days after deployment.”
Read a further discussion concerning OTV-4 and associated payloads by Mr. Molczan on the See-Sat message board here.
The Planetary Society’s Jason Davis confirmed for Universe Today that LightSail will deploy 28 days after launch. But we may only have a slim two day observation window for LightSail between deployment and reentry.
A deployment of LightSail 28 days after launch would put it in the June 16th timeframe.
“That’s the nominal mission time, yes,” Davis told Universe Today. “Our orbital models predict 2-10 days. For our 2016 flight, the mission will last at least four months.”
The Planetary Society plans to have a live ‘mission control center’ to track LightSail after P-POD deployment, complete with a Google Map showing pass predictions.
Satellite spotting can be a fun and addictive pastime, where part of the fun is sleuthing out what you’re seeing. Hey, some relics of space history such as the early Vanguards, Telstars, and Canada’s first satellite Alouette-1 are still up there! Nabbing these photographically are as simple as plopping your DSLR on a tripod, setting the focus and doing a time exposure as the satellite passes by.
The X-37B undergoing encapsulation in preparation for launch. Image credit: USAF
Here’s to smooth solar sailing and clear skies as we embark on our quest to track down the X-37B and LightSail-1 in orbit.
-Follow us as @Astroguyz on Twitter, as we’ll be providing further info on orbits and visibility passes as they are made public.
Sunset photographed from Gale Crater by the Mars Curiosity rover on April 15, 2015. The four images shown in sequence here were taken over a span of 6 minutes, 51 seconds using the left eye of the rover's Mastcam. Credit: NASA/JPL-Caltech
Even robots can’t tear their eyes from a beautiful sunset. NASA’s Mars Curiosity rover pointed its high resolution mast camera at the setting Sun to capture this 4-image sequence on April 15 at the conclusion of the mission’s 956th Martian day. While it resembles an earthly sunset, closer inspection reveals alien oddities.
A day on Mars lasts 24 hours and 39 minutes, so sunrise and sunset follow nearly the same rhythm as they do on Earth. When we eventually establish a base there, astronauts should be able to adjust to the planet’s day-night rhythm with relative ease. Jet lag would be worse.
But sunsets and sunrises offer a different palette of colors than they would on Earth. For starters, the Sun only radiates the equivalent of a partly cloudy afternoon’s worth of light. That’s because Mars’ average distance from the Sun is 141.6 million miles or about half again Earth’s distance. Increased distance reduces the intensity of sunlight.
Not only that, but the solar disk shrinks from the familiar 0.5° across we see from Earth to 0.35° at Mars. Here on the home planet, your little finger extended at arm’s length would cover the equivalent of two Suns. On Mars it would be three!
Wide view of sunset over Gusev Crater taken by NASA’s Spirit Rover in 2005. Both blue aureole and pink sky are seen. Because of the fine nature of Martian dust, it can scatter blue light coming from the Sun forward towards the observer. Credit: NASA/JPL-Caltech
What about color? Dust and other fine particles in the atmosphere scatter the blues and greens from the setting or rising Sun to color it yellow, orange and red. When these tints are reflected off clouds, sunset colors are amplified and spread about the sky, making us reach for that camera phone to capture the glory.
Things are a little different on Mars. The ever-present fine dust in the Martian atmosphere absorbs blue light and scatters the warmer colors, coloring the sky well away from the Sun a familiar ruddy hue. At the same time, dust particles in the Sun’s direction scatter blue light forward to create a cool, blue aureole near the setting Sun. If you were standing on Mars, you’d only notice the blue glow when the Sun was near the horizon, the time when its light passes through the greatest depth of atmosphere and dust.
This was the first sunset observed in color by Curiosity. The color has been calibrated and white-balanced to remove camera artifacts. Mastcam sees color much the way the human eye does, although it’s a little less sensitive to blue. The Sun’s disk itself appears pink because all the cooler colors have been scattered away, similar to why the Sun on Earth appears orange or red when near the horizon. Notice the individual rocks poking up from the ridge in the foreground. Credit: NASA/JPL-Caltech/MSSS/Texas A&M Univ.
On Earth, blue light from the Sun is scattered by air molecules and spreads around the sky to create a blue canopy. Mars has less the 1% of Earth’s atmosphere, so we only notice the blue when looking through the greatest thickness of the Martian air (and dust) around the time of sunset and sunrise.
Sunset on Mars photographed by the Opportunity Rover released earlier this year
The video above of the setting Sun was made using stills taken by Opportunity, NASA’s “other” rover that’s been trekking across the Martian landscape for more than 10 years now. You can see a bit of pink in the Sun just before it sets as in the Curiosity photos, but there’s something else going on, too. Or not going on.
Sunrise of Lake Superior. Atmospheric refraction – bending of the Sun’s light – flattens the disk into an oval shape. Credit: Lyle Anderson
When the Sun sets or rises on Earth, it’s squashed like a melon due to atmospheric refraction. Much thicker air adjacent to the horizon bends the Sun’s light upward, pushing the bottom of the solar disk into the top half which is less affected by refraction because it’s slightly higher. Once the Sun rises high enough, so we’re looking at it through less atmosphere, refraction diminishes and it becomes a circle again.
I’ve looked at both the Opportunity sunset and Curiosity sunset videos many times, and as far as I can tell, the Sun’s shape doesn’t change. At least it’s not noticeable to the casual eye. I bet you can guess why — the air is too thin to for refraction to make much of a difference.
Twilights linger longer on the Red Planet as well because dust lofted high into the stratosphere by storms continues to reflect the Sun’s light for two hours or more after sundown.
So you can see that sunset phenomena on Mars are different from ours because of the unique qualities of its atmosphere. I trust someone alive today will be the first human to see and photograph a Martian sunset. Hope I’m still around when that awesome pic pops up on Twitter.
Andromeda's halo is gargantuan. Extending millions of light years, if we could see in our night sky it would be 100 times the diameter of the Moon or 50 degrees across! Credit: NASA
The merger of the Milky Way and Andromeda galaxy won’t happen for another 4 billion years, but the recent discovery of a massive halo of hot gas around Andromeda may mean our galaxies are already touching. University of Notre Dame astrophysicist Nicholas Lehner led a team of scientists using the Hubble Space Telescope to identify an enormous halo of hot, ionized gas at least 2 million light years in diameter surrounding the galaxy.
The Andromeda Galaxy is the largest member of a ragtag collection of some 54 galaxies, including the Milky Way, called the Local Group. With a trillion stars — twice as many as the Milky Way — it shines 25% brighter and can easily be seen with the naked eye from suburban and rural skies.
Six examples of quasars photographed with the Hubble. Quasars are distant, brilliant sources of light, believed to occur when a massive black hole in the center of a galaxy feeds on gas and stars. As the black hole consumes the material, it emits intense radiation, which is then detected as a quasar. Lehner and team measured Andromeda’s halo by studying how its gas affected the light from 18 different quasars. Credit: NASA/ESA
Think about this for a moment. If the halo extends at least a million light years in our direction, our two galaxies are MUCH closer to touching that previously thought. Granted, we’re only talking halo interactions at first, but the two may be mingling molecules even now if our galaxy is similarly cocooned.
Lehner describes halos as the “gaseous atmospheres of galaxies”. Despite its enormous size, Andromeda’s nimbus is virtually invisible. To find and study the halo, the team sought out quasars, distant star-like objects that radiate tremendous amounts of energy as matter funnels into the supermassive black holes in their cores. The brightest quasar, 3C273 in Virgo, can be seen in a 6-inch telescope! Their brilliant, pinpoint nature make them perfect probes.
To detect Andromeda’s halo, Lehner and team studied how the light of 18 quasars (five shown here) was absorbed by the galaxy’s gas. Credit: NASA
“As the light from the quasars travels toward Hubble, the halo’s gas will absorb some of that light and make the quasar appear a little darker in just a very small wavelength range,” said J. Christopher Howk , associate professor of physics at Notre Dame and co-investigator. “By measuring the dip in brightness, we can tell how much halo gas from M31 there is between us and that quasar.”
Astronomers have observed halos around 44 other galaxies but never one as massive as Andromeda where so many quasars are available to clearly define its extent. The previous 44 were all extremely distant galaxies, with only a single quasar or data point to determine halo size and structure.
Andromeda’s close and huge with lots of quasars peppering its periphery. The team drew from about five years’ worth of observations of archived Hubble data to find many of the 18 objects needed for a good sample.
This illustration shows a stage in the predicted merger between our Milky Way galaxy and the neighboring Andromeda galaxy, as it will unfold over the next several billion years. In this image, representing Earth’s night sky in 3.75 billion years, Andromeda (left) fills the field of view and begins to distort the Milky Way with tidal pull. Credit: NASA; ESA; Z. Levay and R. van der Marel, STScI; T. Hallas; and A. Mellinger
The halo is estimated to contain half the mass of the stars in the Andromeda galaxy itself, in the form of a hot, diffuse gas. Simulations suggest that it formed at the same time as the rest of the galaxy. Although mostly composed of ionized hydrogen — naked protons and electrons — Andromeda’s aura is also rich in heavier elements, probably supplied by supernovae. They erupt within the visible galaxy and violently blow good stuff like iron, silicon, oxygen and other familiar elements far into space. Over Andromeda’s lifetime, nearly half of all the heavy elements made by its stars have been expelled far beyond the galaxy’s 200,000-light-year-diameter stellar disk.
You might wonder if galactic halos might account for some or much of the still-mysterious dark matter. Probably not. While dark matter still makes up the bulk of the solid material in the universe, astronomers have been trying to account for the lack of visible matter in galaxies as well. Halos now seem a likely contributor.
The next clear night you look up to spy Andromeda, know this: It’s closer than you think!
A map of MAVEN's Imaging Ultraviolet Spectrograph (IUVS) auroral detections in December 2014 overlaid on Mars’ surface. The map shows that the aurora was widespread in the northern hemisphere, not tied to any geographic location. The aurora was detected in all observations during a 5-day period. Credits: University of Colorado
Martian auroras will never best the visual splendor of those we see on Earth, but have no doubt. The Red Planet still has what it takes to throw an auroral bash. Witness the latest news from NASA’s MAVEN atmospheric probe.
In December 2014, it detected widespread auroras across Mars’ northern hemisphere dubbed the “Christmas Lights”. If a similar display happened on Earth, northern lights would have been visible from as far south as Florida.
“It really is amazing,” says Nick Schneider who leads MAVEN’s Imaging Ultraviolet Spectrograph (IUVS) instrument team at the University of Colorado. “Auroras on Mars appear to be more wide ranging than we ever imagined.”
A beautiful curtain of auroral rays spreads across the northern sky last night (May 12) as seen from Duluth, Minn. Aurora colors on Earth are caused by the excitation of nitrogen and oxygen atoms by high-speed particles in the solar wind. Oxygen in particular is responsible for most of the aurora’s greens and reds. Credit: Bob King
Study the map and you’ll see the purple arcs extend to south of 30° north latitude. So what would Martian auroras look like to the human eye? Would we see an arcade of nested arcs if we faced east or west from 30°N? Well, er, yes, if you could see into the ultraviolet end of the spectrum. Mars’ atmosphere is composed mostly of carbon dioxide, so most of the auroral emissions occur when high speed solar wind particles ionize CO2 moleculesand carbon monoxide to produce UV light. Perhaps properly suited-up bees, which can see ultraviolet, would be abuzz at the sight.
High-speed particles from the Sun, mostly electrons, strike oxygen and nitrogen atoms in Earth’s upper atmosphere. As they return to their “relaxed” state, they emit light in characteristic colors. Credit: NASA
That’s not the end of the story however. Martian air does contain 0.13% oxygen, the element that puts the green and red in Earth’s auroras. The “Christmas Lights” penetrated deeply into Mars’ atmosphere, reaching an altitude of just 62 miles (100 km) above its surface. Here, the air is relatively thicker and richer in oxygen than higher up, so maybe, just maybe Christmas came in green wrapping.
Mars has magnetized rocks in its crust that create localized, patchy magnetic fields (left). In the illustration at right, we see how those fields extend into space above the rocks. At their “peaks”, auroras can form. Credit: NASA
Nick Schneider, who leads MAVEN’s Imaging Ultraviolet Spectrograph (IUVS) instrument team, isn’t certain but thinks it’s possible that a diffuse green glow could appear in Mars’ sky during particularly energetic solar storms.
Earth’s magnetosphere, an area of space that’s controlled by the planet’s magnetic field, guides solar wind electrons and protons along magnetic field lines into the atmosphere in the polar regions to create auroras. The planet’s field is created by electric currents generated in its outer nickel-iron core. Credits: NASA
While the solar wind produces auroras at both Earth and Mars, they originate in radically different ways. At Earth, we’re ensconced in a protective planet-wide magnetic field. Charged particles from the Sun are guided to the Earth’s poles by following a multi-lane freeway of global magnetic field lines. Mars has no such organized, planet-wide field. Instead, there are many locally magnetic regions. Particles arriving from the Sun go where the magnetism takes them.
“The particles seem to precipitate into the atmosphere anywhere they want,” says Schneider. “Magnetic fields in the solar wind drape across Mars, even into the atmosphere, and the charged particles just follow those field lines down into the atmosphere.”
Maybe one day, NASA or one of the other space agencies will send a lander with a camera that can shoot long time exposures at night. We’ll call it the “Go Green” initiative.
Volumes 1 and 2 on sale now. Image credit: Willmann-Bell, Inc
Any lover of the night sky knows the value of a good star atlas and an astronomical handbook to guide your exploration of the universe. And while it’s true that more information exists out there than ever before online, much of it is intended for a general armchair astronomical audience, or is scattered about the web in disparate places…
But an exciting new series promises to be an essential must for deep sky observers. Annals of the Deep Sky: A Survey of Galactic and Extragalactic Objects by Jeff Kanipe and Dennis Webb is a through rundown of the night sky constellation-by-constellation which is aimed at the advanced observer. Mr. Kanipe is a science writer with 35 years experience, and Mr. Webb is a NASA engineer and observer with more than 25 years of experience exploring the night sky. If the names are familiar to deep sky fans, it might be because they also teamed up to produce the Arp Atlas of Peculiar Galaxies: A Chronicle and Observer’s Guide in 2006. Volumes 1 and 2 covering constellations in alphabetical order from Andromeda to Caelum are out now from Willmann-Bell, Inc., and the projected 12 volume set will cover all 88 constellations when completed. Volume 3 is due out in early 2016.
Messier 31 deconstructed by the Annals of the Deep Sky. Image credit: NASA/Willmann-Bell, Inc
Annals promises to join the ranks of some of the classic sky guides. Observers from the pre-digital era will recall the paucity of good observing resources available just a few decades ago. Growing up in rural northern Maine, even getting our hands on Sky and Telescope or Astronomy magazine was a daunting challenge, and we often gleaned knowledge of the astronomical goings on for the year from the tables of the Farmer’s Almanac. I remember hearing of the close 0.0312 AU passage past the Earth of Comet IRAS-Araki-Alcock in 1983, days after it had passed by! Contrast this with today, as message boards and Twitter alert us to new discoveries, sometimes within minutes.
Over the years, Ottewell’s yearly Astronomical Calendar has become a crucial resource as well.
Annals of the Deep Sky promises to be this generation’s answer to Burnham’s Celestial Handbook. You have to be of a certain age to remember Burnham’s, but that landmark three volume guide is one of the few hard copy resources that still resides on our desk well into the digital era. And Burnham’s has survived despite its use of now outdated 1950.0 stellar coordinates… that’s the kind of legendary staying power it has had in the amateur astronomy community!
A monument to Burnham’s Celestial Handbook at the Lowell observatory in Flagstaff, Arizona. Image credit: David Dickinson
Annals of the Deep Sky begins with an outline of how to use the books, and a summary of basic observational astronomy and astrophysics. Like Burnham’s, Annals presents the field of observational astronomy beyond the solar system. But unlike Burnham’s—which was mainly text—the true magic of Annals lies in its extensive use of maps, diagrams and charts, all meant for the serious visual and photographic observer, both in planning observation runs and in the field. These also include some innovative ‘3-D’ style views through the constellations themselves as seen from our Earthly perspective. These views take the observer out through the plane of our galaxy and beyond as we peer out into the universe.
Annals of the Deep Sky also incorporates the latest discoveries and our understanding of the universe, as well as how our knowledge of astronomy and astrophysics got to where it is today. Annals not only provides the visual observer with handy field of view overlays for classic objects such as the Andromeda Galaxy (M31), but it also provides charts depicting camera sensor versus focal length and field of view for DLSR photography of key objects. To our knowledge, no other such resource for this specialized level of information exists for astrophotographers. We also enjoyed the graphic depictions of visual and spectroscopic binary star orbits, another tough item to dig up in research, even with today’s modern planetarium programs.
Representative views of visual (top) and spectroscopic binary orbits. Image credit: Willmann-Bell, Inc
The inclusion of history and astronomical lore is also a great touch that really makes the resource ‘pop’ in a vein similar to Burnham’s. This lends a fascinating dimension of astronomical history to the Annals that suits to a casual ‘shotgun’ reading style. Like Burnham’s, I can see discovering something new from a random opening of the Annals for years to come. A fine example is the lingering mystery of the Nova of 1860 in Volume 2 observed by Joseph Baxendell near Arcturus, a fascinating tale we’d never heard of.
We only wish that this awesome resource was also available in digital format so that we could carry this essential reference with us out in the field… we could easily envision cross-referencing information from a laptop planetarium program such as Starry Night or Stellarium at the eyepiece, with Annals of the Deep Sky cued up on the Kindle.
So grab that ‘Dobsonian light bucket’ and the first two volumes of Annals of the Deep Sky. This series promises to be an anticipated gem for many years to come. And hey, you can tell the next generation of hipster backyard observers that you remember what it was like before we had Annals of the Deep Sky to consult!
Getting closer... Saturn as seen on March 25th, 2015. Image credit: Efrain Morales
The month of May generally means the end of star party season here in Florida, as schools let out in early June, and humid days make for thunderstorm-laden nights. This also meant that we weren’t about to miss the past rare clear weekend at Starkey Park. Jupiter and Venus rode high in the sky, and even fleeting Mercury and a fine pass of the Hubble Space Telescope over central Florida put in an appearance.
But the ‘star’ of the show was the planet Saturn as it appeared at nightfall low to the southeast. Currently rising about 9:00 PM local, Saturn is joining the evening skies as it approaches opposition next week.
This also means we’ve got every naked eye planet set for prime time evening viewing this week with the exception of Mars, which reaches solar conjunction on June 14, 2015. Mercury will be the first world to break this streak, as it descends into the twilight glare by mid-May.
The apparent path of Saturn from May to November 2015. Image credit: Starry Night Education software
Saturn reaches opposition for 2015 on May 23rd at 1:00 Universal Time (UT), which equates to 9:00 PM EDT the evening prior on May 22 at nearly 9 astronomical units (AU) distant. Oppositions of Saturn are getting slightly more distant to the tune of 10 million kilometers in 2015 versus last year as Saturn heads towards aphelion in 2018. Saturn crosses eastward from the astronomical constellation of Scorpius in the first week of May, and spends most of the remainder of 2015 in Libra before looping back into the Scorpion in mid-October. The first of June finds Saturn just over a degree southward of the +4th magnitude star Theta Librae. Saturn takes nearly 30 Earth years to complete one orbit, meaning that it was right around the same position in the sky in 1985, and will appear so again in 2045. Relatively speedy Jupiter also overtakes Saturn as seen from the Earth about once every 20 years, as it last did on 2000 and is set to do so again in 2020.
And though series of occultations of Saturn by the Moon wrapped up in 2014 and won’t resume again until December 9, 2018, there’s also a good chance to spy Saturn two degrees away from the daytime Moon with binoculars on June 1st just 24 hours prior to Full:
Looking east on the evening of June 1st just before sunset. Image credit: Stellarium
The tilt of the rings of Saturn is also slowly widening from our Earthbound perspective. At opposition, Saturn’s rings subtend 43” across, and the ochre disk of Saturn itself spans 19”. Incidentally, on a good pass, the International Station has a visual span roughly equivalent to Saturn plus rings. In 2015, the rings are tilted 24 degrees wide and headed for a maximum approaching 27 degrees in 2017. The rings appeared edge on in 2009 and will do so again in 2025.
Getting wider… our evolving view of Saturn’s rings. Image credit and copyright: Andrew Symes
Also, keep an eye out for the Seeliger effect. Also sometimes referred to as the ‘opposition surge,’ this is a retroreflector-style effect that causes an outer planet to brighten up substantially on the days approaching opposition. In the case of Saturn and its rings, this effect can be especially dramatic. Not only is the disk of Saturn and the billions of icy snowballs casting shadows nearly straight back as seen from our vantage point near opposition, but a phenomenon known as coherent backscatter serves to increase the collective brightness of Saturn as well. You see the same effect at work as you drive down the Interstate at night, and highway signs and retroreflector markers down the center of the road bounce your high-beams back at you.
Highway retroreflectors in action. Image credit: Wikimedia Commons/Public Domain
We’ve seen some pretty nifty image comparisons demonstrating the Seeliger effect on Saturn, but as of yet, we haven’t seen an animation of the same. Certainly, such a feat is well within the capacities of amateur astronomers out there… hey, we’re just throwing that possibility out into the universe.
The changing face of Saturn. Image credit: Stellarium
Through a small telescope, the moons of Saturn become readily apparent. The brightest of them all is Titan at magnitude +9, orbiting Saturn once every 16 days. Discovered by Dutch astronomer Christiaan Huygens on March 25, 1655 using a 63 millimeter refractor with an amazing 337 centimeter focal length, Titan would easily be a planet in its own right were it directly orbiting the Sun. Titan also marks the most distant landing of a spacecraft ever carried out by our species, with the descent of the European Space Agency’s Huygens lander on January 14, 2005. Huygens hitched a ride to Saturn aboard NASA’s Cassini spacecraft, which is slated to end its mission with a destructive reentry over the skies of Saturn in 2017. Saturn has 62 known moons in all, and Enceladus, Mimas, Tethys, Dione, Rhea and two-faced Iapetus are all visible from a backyard telescope.
The scale of the orbits of Saturn’s moons. Image credit: Starry Night Education software
You can check out the current position of Saturn’s major moons (excluding Iapetus) here.
And speaking of Iapetus, the outer moon would make a fine Saturn-viewing vantage point, as it is the only major moon with an inclined orbit out of the ring plane of Saturn:
Expect our Saturn observing resort to open there one day soon.
Up for a challenge? Standard features to watch for include: the shadow of the rings on the planet, and the shadow of the planet across the rings, as well as the Cassini division between the A and B ring… but can you see the disk of the planet through the gap? High magnification and steady seeing are your friends in this feat of visual athletics… catching sight of it definitely adds a three dimensional quality to the overall view.
Photos of the white spots within the 57-mile-wide on Ceres photographed on May 3 and 4 by NASA's Dawn spacecraft. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA / montage by Tom Ruen
We don’t know exactly what those mysterious white spots on Ceres are yet, but we’re getting closer to an explanation. Literally. The latest images from the Dawn spacecrafttaken a mere 8,400 miles from the dwarf planet Ceres reveal that the pair of spots are comprised of even more spots.
“Dawn scientists can now conclude that the intense brightness of these spots is due to the reflection of sunlight by highly reflective material on the surface, possibly ice,” said Christopher Russell, principal investigator for the Dawn mission from the University of California, Los Angeles.
This animation shows a sequence of images taken by NASA’s Dawn spacecraft on May 4, 2015, from a distance of 8,400 miles (13,600 km), in its RC3 or science mapping orbit. The image resolution is 0.8 mile (1.3 km) per pixel. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
Dawn recently concluded its first science orbit, making a 15-day full circle around Ceres while gathering data with its suite of science instruments. This past Saturday, May 9, its ion engine fired once again to lower the spacecraft to its second science orbit which it will enter on June 6. On that date, the probe will hover just 2,700 miles (4,400 km) above the dwarf planet and begin a comprehensive mapping of the surface. Scientists also hope the bird’s eye view will reveal clues of ongoing geological activity.
Check out this great video compiled from Dawn’s still frames of Ceres by Tom Ruen. Almost feels like you’re there.
There’s no doubt a lot’s been happening on Ceres. One look at all those cracks hint at either impact-related stresses some kind of crustal expansion. Geological processes may still make this little world rock and roll.
In this uncropped single frame, not only are multiple white spots visible but also long, roughly parallel cracks or troughs in Ceres’ surface. Are they impact-related or caused by some other stress? Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
Fortunately, we won’t have to wait till next month for more photos. NASA plans to pause the probe twice on the way down to shoot and send fresh images.
Astronomers have been arguing over just how many spiral arms our Galaxy exhibits. Is the Milky Way a four or two-armed spiral galaxy? Astronomers had often assumed the Milky Way was potentially a four-armed spiral galaxy, but comparatively recent observations from NASA’s Spitzer telescope implied the Galaxy had two spiral arms. In 2013, astronomers mapped star forming regions and argued they had found the two missing arms, bringing the total number of arms back to four.
The case for a four-armed Milky Way may have just gotten stronger.
A team of Brazilian astronomers used star clusters embedded in their natal clouds to trace the Galaxy’s structure. “Our results favour a four-armed spiral Galaxy, which includes the Sagittarius-Carina, Perseus, and Outer arms.”, remarked the group from the Universidade Federal do Rio Grande do Sul.
Spiral map of the Galaxy by Urquhart et al. 2013 (image credit: Urquhart et al. 2013, R. Hurt, the Spitzer Science Center, R. Benjamin).
“Despite efforts aimed at improving our understanding of the Galaxy’s structure, questions remain. There is no consensus regarding the number and shape of the Galaxy’s spiral arms.”, noted lead author D. Camargo. He added that the Sun’s location within the obscured disc of the Galaxy was a principal factor hindering our understanding of the Milky Way’s broader structure. In other words, we do not have a bird’s eye view of our Galaxy.
The team remarked that young embedded clusters are excellent tracers of the Galaxy’s structure, “The present results indicate that the Galaxy’s embedded clusters are predominantly located in the spiral arms.” They noted that star formation may occur after the collapse and fragmentation of giant molecular clouds found within spiral arms, and consequently the young embedded star clusters that subsequently emerge are excellent probes of Galactic structure as they have not displaced far from their birthplace.
A projected face-on view of the distribution of embedded star clusters studied by Camargo et al. 2015. The objects appear to lie on the Sagittarius-Carina spiral arm, Perseus arm, and potentially an extension of the Outer arm (image credit: Camargo et al. 2015).
The team used data from NASA’s WISE infrared telescope to identify young clusters still embedded in their natal clouds, which are often encompassed by significant dust. Infrared stellar light is less obscured by dust than visible light, giving the astronomers an unprecedented view. Indeed, the group discovered 7 new embedded clusters, several of which (designated Camargo 441-444) may belong to a larger aggregate that resides in the Perseus arm. They suggested that a giant molecular cloud was compressed by the spiral arm which may have triggered star formation in several clumps, and numerous star clusters with similar ages emerged (an alternative or concurrent scenario is sequential formation).
Astronomer A. Mainzer discusses NASA’s WISE telescope (Wide-Field Infrared Survey Explorer), which was used by Camargo et al. 2015 to identify embedded star clusters.
The team also used near-infrared data from the 2MASS survey to determine distances for the star clusters, once the objects were identified in the WISE images. A primary goal of their work was to establish accurate fundamental cluster parameters, which would bolster any resulting conclusions concerning the Galaxy’s overall structure. An innovative algorithm was therefore adopted to minimize contamination by foreground and background stars along the sight-line, which may otherwise appear as cluster members and degrade the reliability of any distant estimates.
“The embedded clusters in the present sample are distributed along the Sagittarius-Carina, Perseus, and Outer arms.”, concluded the team. They likewise noted that the search for new embedded clusters throughout the entire Galaxy must continue unabated, since such targets may foster our understanding of the Galaxy’s structure.
The discoveries are described in a new study by D. Camargo, C. Bonatto, and E. Bica that is entitled “Tracing the Galactic spiral structure with embedded clusters”. The research has been accepted for publication, and will appear in a forthcoming issue of the Monthly Notices of the Royal Astronomical Society (MNRAS). A preprint of the work is available on arXiv.
Comet G2 MASTER passes near the Helix Nebula in Aquarius on the night of April 21st.
Did you catch the performance of Comet C/2014 Q2 Lovejoy earlier this year? Every year provides a few sure bets and surprises when it comes to binocular comets, and while we may still be long overdue for the next truly ‘Great Comet,’ 2015 has been no exception.
This week, we’d like to turn your attention to two icy visitors to the inner solar system which may present the best bets comet-wise over the next few weeks: Comets C/2014 Q1 PanSTARRS and C/2015 G2 MASTER.
First up is Comet C/2014 Q1 PanSTARRS. Discovered on August 16, 2014 by the Panoramic Survey Telescope & Rapid Response System (PanSTARRS) based atop Mount Haleakala in Hawaii, we’ve known of the potential for Q1 PanSTARRS to put on a decent show this summer for a while. In fact, it made our roundup of comets to watch for in our 101 Astronomical Events for 2015. Q1 PanSTARRS currently sits at +11th magnitude as a morning sky object in the constellation Pisces. On a 39,000 year long parabolic orbit inclined 45 degrees relative to the Earth’s orbit, Q1 PanSTARRS will leap up across the ecliptic on May 17th and perhaps reach +3rd magnitude as it nears perihelion in early July and transitions to the evening sky.
An image of Comet C/2014 Q1 PanSTARRS shortly after discovery. Credit and copyright: Efrain Morales Rivera.
Though it may put on its best show in July and August, a few caveats are in order. First, we’ll be looking at Q1 PanSTARRS beyond the summer Sun, and like C/2011 L4 PanSTARRS a few years back, it’ll never leave the dusk twilight, and will always appear against a low contrast backdrop.
The May-June path of Comet Q1 PanSTARRS through the dawn sky as seen from latitude 30 degrees north. Credit: Starry Night Education software.
Here are some notable upcoming events for Comet C/2014 Q1 PanSTARRS:
(Unless otherwise noted, a ‘close pass’ is here considered to be less than one degree of arc, about twice the diameter of a Full Moon.)
May 16: Passes into the constellation Aries.
May 16: The waning crescent Moon passes 2 degrees distant.
May 17: Crosses northward through the ecliptic.
May 20: May break +10th magnitude.
June 11: Passes in to the constellation Taurus.
June 12: Passes 2 degrees from M45 (The Pleiades).
June 15: May break 6th magnitude.
June 20: Passes into Perseus.
June 21: Passes into Auriga.
June 23: Passes +2.7 magnitude star Hassaleh (Iota Aurigae).
June 25: Passes the +7.5 magnitude open cluster IC 410.
June 26: Passes +6 magnitude Pinwheel Open Cluster (M36).
The July-August evening path of Q1 PanSTARRS as seen from latitude 30 degrees north. Credit: Starry Night Education software.
July 2: Crosses into Gemini.
July 3: Passes the +3.6 magnitude star Theta Geminorum.
July 5: Passes 10 degrees north of the Sun and into the evening sky.
July 6: Passes midway between Castor and Pollux.
July 6: Reaches perihelion at 0.315 astronomical units (AU) from the Sun.
July 7: May top out at +3rd magnitude.
July 8: Crosses into Cancer.
July 12: Photo Op: passes M44, the Beehive Cluster.
July 13: Sits 30 degrees from Comet C/2015 G2 MASTER (see below).
July 15: May drop below +6th magnitude.
July 15: Crosses the ecliptic southward.
July 17: The waxing crescent Moon passes 1.5 degrees south.
July 19: Crosses into Leo.
July 20: Closest to Earth, at 1.18 AU distant.
July 21: Less than 10 degrees from Jupiter and Venus.
July 22: Crosses into Sextans.
July 26: Crosses the celestial equator southward.
August 4: Crosses into Hydra.
August 5: Crosses into Crater.
August 18: Crosses back into Hydra.
August 30: Crosses into Centaurus.
September 1: Drops below +10th magnitude.
The projected light curve of Q1 PanSTARRS over time. The black dots represent observations. Credit: Weekly Information about Bright Comets.
The next comet on deck is the recently discovered C/2015 G2 MASTER. If you live in the southern hemisphere, G2 MASTER is the comet that perhaps you haven’t heard of, but should be watching in the dawn sky. Discovered last month on April 7 as by MASTER-SAAO (The Russian built Mobile Astronomical System of Telescope-Robots at the South African Astronomical Observatory), this is not only the first comet bagged by MASTER, but the first comet discovery from South Africa since 1978. G2 MASTER has already reached magnitude +7 and is currently crossing the constellation Sculptor. It is also currently only visible in the dawn sky south of 15 degrees north latitude, but images already show a short spiky tail jutting out from G2 MASTER, and the comet may rival Q2 Lovejoy’s performance from earlier this year. Expect G2 MASTER to top out at magnitude +6 as it nears perihelion in mid-May. Observers around 30 degrees north latitude in the southern U.S. should get their first good looks at G2 MASTER in late May, as it vaults up past Sirius and breaks 10 degrees elevation in the evening sky after sunset. Again, as with Q1 PanSTARRS, cometary performance versus twilight will be key!
An April 10th image of Comet C/2015 G2 MASTER, plus an initial projected light curve versus solar elongation over time. Credit: Ernesto Guido & Nick Howes/Remanzacco Observatory
Here are some key dates with astronomical destiny for Comet G2 MASTER over the coming weeks:
May 9: Crosses into Fornax.
May 15: May top out at +6th magnitude.
May 13: Closest to Earth at 0.47 AU.
May 14: Crosses into Eridanus.
May 16: Crosses into Caelum.
May 17: Crosses into Lepus.
May 20: Passes the +3.8 magnitude star Delta Leporis.
May 23: Crosses into Canis Major.
May 23: Reaches perihelion at 0.8 AU from the Sun.
May 27: Crosses into Monoceros.
May 28: Passes the +5.9 magnitude Open Cluster M50.
Comet G2 MASTER imaged on May 7th. Credit and copyright: Adriano Valvasori
June 8: Crosses northward over the celestial equator and into the constellation Canis Minor.
July 1: May drop below 10th magnitude.
G2 MASTER also crosses SOHO’s field of view on July 24th through August 4th, though it may be too faint to see at this point.
Here are the Moon phases for the coming weeks to aid you in your comet quest:
Full Moons: June 2nd, July 2nd, July 31st, August 29th.
New Moons: May 18th, June 16th, July 16th, August 14th.
Binoculars are our favorite ‘weapon of choice’ for comet hunting. Online, Heavens-Above is a great resource for quickly and simply generating a given comet’s sky position in right ascension and declination; we always check out the Comet Observers Database and Seiichi Yoshida’s Weekly Information about Bright Comets to see what these denizens of the outer solar system are currently up to.
Good luck, and be sure to regale us with your comet-hunting tales of tragedy and triumph!
