Artist's impression of cosmic rays striking Earth (Simon Swordy/University of Chicago, NASA)
Quick, do you have an Android phone in your pocket? A few small changes and you could help physicists probe more of the curious nature of cosmic rays, high-energy particles that emanate from outside our solar system.
Just download an app, cover up your phone’s camera with duct tape, then place it somewhere (running idle) with the screen facing up. If a particle “event” happens, the information will be logged in a central database.
The project (called Distributed Electronic Cosmic-ray Observatory or DECO) aims to record secondary particles called muons that occur when cosmic rays hit the Earth’s atmosphere. Scientists believe cosmic rays are created in black holes and supernovas, but more studies are needed.
Screenshot of an Android app developed at the University of Wisconsin-Madison that aims to capture cosmic rays. Credit: Justin Vandenbroucke
Researchers at the Wisconsin IceCube Particle Astrophysics Center (WIPAC), led by Justin Vandenbroucke, note that there are things about cosmic rays that confuse physicists. Their paths in space change as they go across magnetic fields, and it makes searching for other astronomy events difficult. That’s where they hope the phone study will be useful.
“Smartphone cameras use silicon chips that work through what is called the photoelectric effect, in which particles of light, or photons, hit a silicon surface and release an electric charge,” the University of Wisconsin-Madison wrote in a press release.
“The same is true for muons. When a muon strikes the semiconductor that underpins a smartphone camera, it liberates an electric charge and creates a signature in pixels that can be logged, stored and analyzed.”
For more details on how to run and use the app, consult this page (it’s the second item).
A view from the Opportunity rover on Mars, which is exploring the rim of Endeavour Crater. Picture taken on Sol 3,798 in October 2014, while the rover was en route to a small crater called Ulysses. Credit: NASA/JPL-Caltech/Cornell Univ./Arizona State Univ.
NASA’s Opportunity rover is still experiencing frequent memory resets as it roams the Martian terrain near Endeavour Crater, even though the agency performed a reset a few weeks ago.
Officials, however, say the rover is healthy otherwise and ready for its next science goals: reaching a small crater dubbed Ulysses, and watching a comet pass by Mars in mid-October.
Opportunity is approaching its eleventh anniversary of working on Mars this coming January. The hardy rover has driven 25.34 miles (40.78 kilometers) as of late September, almost a marathon’s worth of exploration. Its original mandate was to last just 90 Earth days on Mars.
In late August, however, science was getting derailed because the aging rover’s Flash memory experienced frequent resets. This kind of memory stores information even while the rover is turned off. NASA did a reformat from afar and said at the time that the procedure worked perfectly, but in the weeks since Opportunity has experienced several resets. The agency is investigating what to do next.
Tracks from the Curiosity rover across Martian terrain on Sol 3,798 in September 2014. Credit: NASA/JPL-Caltech/Cornell Univ./Arizona State Univ.
NASA’s Opportunity update archive reports memory resets on Sept. 17, 20, 22, 23, 24 and 26. The agency is calling these events “benign” and the rover is performing drives and science amid the issues.
Among its work, in late September the rover did a twilight test of its panoramic camera to get ready for observations of Comet Siding Spring, which is skimming the Red Planet on Oct. 19, 2014.
On the surface, the rover has been examining ejecta of the small crater Ulysses and doing close-up observations of a rock surface nicknamed “Hoover”. Opportunity’s long-term science goal is to reach a zone dubbed Marathon Valley, where there could be clay minerals that formed in water.
Artist's impression of a flare erupting from binary star sytem DG CVn. Credit: NASA's Goddard Space Flight Center/S. Wiessinger
Don’t get too close to this little star! In April, a red dwarf star sent out a series of explosions that peaked at 10,000 times as powerful as the largest solar flare ever recorded.
The tiny star packs a powerful punch because its spin is so quick: it rotates in less than a day, or 30 times faster than the Sun does. Astronomers believe that in the distant past, when the Sun was young, it also was a fast turner — and could have produced “superflares”, as NASA terms the explosions, of its own.
“We used to think major flaring episodes from red dwarfs lasted no more than a day, but Swift detected at least seven powerful eruptions over a period of about two weeks,” stated Stephen Drake, an astrophysicist at NASA’s Goddard Space Flight Center in Maryland. “This was a very complex event.”
The surprising activity came from a red dwarf star in a binary system that together is known as DG Canum Venaticorum (DG CVn). Located just 60 light-years away, the two red dwarfs are each about one-third the size and mass of the Sun. Astronomers can’t say for sure which one sent out the eruption because the stars were so close to each other, at about three times the distance of Earth’s average distance to the sun.
The first flare (which sent out a burst of X-rays) caused an alert in NASA’s Swift Space Telescope’s burst alert telescope on April 23. It’s believed to be caused by the same process that creates flares on our Sun — magnetic field lines twisting and then releasing a burst of energy that sends out radiation.
Three hours later came another flare — scientists have seen similar events on the Sun after one active region sets off flares in another — and then came “successively weaker blasts” in the next 11 days, NASA said. Normal X-ray emissions stabilized about 20 days after the first flare. Swift is now monitoring this star for further activity.
Drake presented his results at the August meeting of the American Astronomical Society’s high energy astrophysics division, which was highlighted in a recent release from NASA.
3D view created by Mattias Malmer of the recent ESA image (below) showing multiple jets of gas and dust spraying from Comet 67P/Churyumov-Gerasimenko. Grab your red-blue plastic glasses and prepare to enter another dimension. Malmer created the view by draping a navigation camera image over a 3D model of the comet and then photographing it from two slightly different perspectives. Click for large version. Credit: ESA/Rosetta/NAVCAM/processing by Mattias Malmer
She’s gonna blow! Rosetta’s navigation camera recently grabbed our best view yet of the geyser-like jets spraying from the nucleus of Comet 67P/Churyumov-Gerasimenko. They were taken on September 26 as the spacecraft orbited the comet at a distance of just 16 miles (26 km) and show jets of water vapor and dust erupting from several discrete locations beneath the surface along the neck region of the comet’s nucleus. Mattias Malmer, a 3D technical director, created the spectacular 3D views by draping the navigation camera images over a 3D model of the comet and then photographing it from two slightly different perspectives.
Jets of gas and dust are seen escaping comet 67P/C-G on September 26 in this four-image mosaic. Click to enlarge. Credit: ESA/Rosetta/NAVCAM
Jets form when the sun warms the comet’s coal-black surface, causing ices beneath to sublimate or change directly from solid to gas without becoming liquid. This is possible because of the near-zero atmospheric pressure at the comet. Pressure builds in the pockets of gas until they find escape through cracks or pores as plume-like jets. Comet dust along with the gas fashions the coma and tail over time. Something similar happens when you shake up a bottle of champagne and then loosen the cork. Trapped carbon dioxide (what makes the “fizz”) blasts the cork across the room.
Comet Churyumov-Gerasimenko rotating from darkness into light. (Mattias Malmer)
If you liked the still images, check out these videos by Malmer. He used the same draping technique and then animated the stills. Be sure to stop by his Cascade of Light blog for more images and videos when you get a chance.
Comet Churyumov-Gerasimenko rotating in 3D (Mattias Malmer)
I saved the best for last. What majesty!
3D rotation of Comet 67P/C-G with jets (Mattias Malmer)
October 2014 means eclipse season 2 of 2 for the year is upon us.
Don’t fear the ‘Blood Moon’ that’s currently infecting the web, but if you find yourself on the correct moonward facing hemisphere of the planet, do get out and observe the total lunar eclipse coming right up on the morning of Wednesday, October 8th. This is the second and final total lunar eclipse of 2014, and the second of four in a quartet series of lunar eclipses known as a tetrad.
And the good news is, the eclipse once again favors nearly all of North America. From the western U.S. and Canada, the Moon will be high in the western skies when partial phases begin early in the morning on October 8th. The western U.S., Canada and Alaska will see the entire 61 minute span of totality, just 18 minutes shorter than last April’s lunar eclipse. The Moon will be high in the sky during totality for the Hawaiian Islands, and viewers in Australia and the Pacific Far East will witness the eclipse in the evening hours.
The visibility regions for the total lunar eclipse. Credit: NASA/GSFC/Espenak.
This lunar eclipse is part of saros 127, and marks number 42 of a series of 72 for that particular saros. If you witnessed the total lunar eclipse visible from North America and Europe on September 27th, 1996, you caught the last of the series, and if you catch the next eclipse in the saros on October 18th, 2032, you’ve earned a veteran lunar eclipse-watchers badge of seeing an exeligmos, or “triple saros” of eclipses.
The path of the Moon through the Earth’s umbra on October 8th. Adapted from NASA/GFSC.
Timings for key phases of the eclipse are as follows:
Not all total lunar eclipses are the same when it comes to color. Totality can appear anywhere from a dark brick color, as happened during the December 9th, 1992, eclipse following the eruption of Mount Pinatubo, when the Moon nearly disappeared during totality, to a bright coppery red, as seen during the April eclipse earlier this year. The Moon passes to the north of the dark central core of the Earth’ shadow next Wednesday, so expect a brighter than normal eclipse, especially along the Moon’s northeast limb. Grab a painter’s wheel and compare the eclipsed Moon to swatches of orange through red: what colors do you see? What you’re seeing is the combinations of all the world’s sunsets refracted into the cone of the Earth’s shadow, which is about three times the size of the Moon at its average distance as seen from Earth. Remember, the Moon is experiencing a total solar eclipse as we watch the lunar eclipse unfold!
The October 8th total solar eclipse as seen from the Apollo 11 landing site on the nearside of the Moon. Created using Stellarium.
This color can be quantified and described on what is known as the Danjon Scale, with 0 being a very dark eclipse with the Moon barely visible, to a 4, meaning a very bright eclipse.
And yes, each total lunar eclipse is now receiving the “Blood Moon” meme thanks to ye ole Internet. Expect the conspiracy-minded to note that this eclipse occurs on the Jewish holiday of Sukkot starting at sundown on the 8th, which isn’t really all that wondrous as the Jewish calendar is a luni-solar one, and total lunar eclipses have to occur during a Full Moon by definition. Wait long enough, and an occasional “Sukkot total lunar eclipse” does indeed occur.
The footprint of the October 8th occultation of Uranus by the Moon during totality. (Credit: Occult 4.1.0).
But a truly rare event does occur during this eclipse, as the Moon actually occults (passes in front of) the planet Uranus during totality for observers in northern Alaska and northeast Asia. The rest of us in the observing zone will see a near miss. Can you spy Uranus with binoculars near the lunar limb during totality? Another such rarity occurred during Shakespeare’s time on December 30th, 1591, involving Saturn and the eclipsed Moon, and another such odd occurrence transpires in 2344 A.D.
The circumstances of the 2344 eclipse/occultation. Credit: Starry Night, NASA/GSFC & Occult 4.0.1.
The brightest star to be occulted by the total eclipsed Moon as it crosses the constellation Pisces is +7.9th magnitude HIP 4231 for the northern U.S. and Canada.
And speaking of historical eclipses, there’s a Columbus Day tie-in with the phenomenon as well. Like many mariners of his day, Columbus was well-versed in celestial navigation, and used a total lunar eclipse to get a good one-time fix on his longitude at sea, an experiment that you can easily replicate. Columbus also wasn’t above using prior knowledge of an impending lunar eclipse to get himself and his crew out of a bind with the locals when the need arose.
An outstanding sequence of images taken during the April 15th, 2014, total lunar eclipse. Credit: Michael Zeiler (Eclipse-Maps) Used with permission.
Photographing an eclipse with a DSLR is as easy as shooting an image of the Moon. Try this a few evenings before the big event. A minimum focal length of 200mm is needed to render the Moon larger than a white dot in the image, and remember that the Moon is much darker during total eclipse, and you’ll need to step the exposure times rapidly down from 1/100th of a second to 2 to 4 seconds during totality.
A long-running effort by Sky & Telescope has been looking for amateur observations of precise crater contacts along the rim of the umbra in an effort to measure variations in the diameter of the Earth’s shadow.
The Moon versus Uranus as seen from Napa, California just past mid-eclipse on the morning of October 8th. Credit: Starry Night Education Software.
As always, weather prospects are the big question mark when it comes to eclipses. Typically, the southwestern U.S. experiences 13-20 clear days in the month of October; prospects worsen to the northwest, with an average of 3-12 days. We’ll be looking at resources such as NOAA, Skippy Sky and ClearSkyChart on the evenings leading up to the 8th. The great thing about a lunar eclipse is, you don’t need a 100% clear sky to see it: just a clear view of the Moon!
Up for a challenge? We’ve yet to see a capture of a shadow transit of the International Space Station in front of the eclipsed Moon. This time around, such a capture should be possible across southern coastal California and the Baja peninsula just minutes prior to the onset of totality.
A shadow pass of the International Space Station just prior to the onset of totality. Note the position of the Moon. Created using Orbitron.
Another bizarre catch, known as a selenelion — witnessing the end of lunar totality after sunrise — may just be possible across the northeastern U.S. into the Canadian Maritimes as the eclipsed Moon sets during totality. The more elevation you can get the better! This works because the Moon lingers a bit in the large shadow of the Earth, plus atmospheric refraction gives the low altitude Sun and Moon a slight boost.
Clouded out? On the wrong side of the planet? You can watch the eclipse online at the following links:
– Live views courtesy of Gialuca Masi and the Virtual Telescope starting at 10:00 UT on October 8th.
– A live webcast starting at 9:00 UT courtesy of Slooh:
– A Columbia State University broadcast, (time to be determined).
Planning an ad-hoc broadcast? Let us know!
And as the eclipse wraps up, the biggest question is always: When’s the next one? Well, lunar eclipse number three of the four eclipse tetrad occurs next year on April 4th, 2015… but in just two weeks time, the western United States and Canada will also witness a fine partial solar eclipse on Oct 23rd…
Stay tuned!
Got images of the total lunar eclipse? Send ‘em in to Universe Today’s Flickr forum!
Interested in eclipse sci-fi? Check out our latest short stories Exeligmos and Shadowfall.
Phobos. From where did it arise or arrive? Is it dry or wet? Should we flyby or sample and return? Should it be Boots or Bots? (Photos: NASA, Illus.:T.Reyes)
Ask any space enthusiast, and almost anyone will say humankind’s ultimate destination is Mars. But NASA is currently gearing up to go to an asteroid. While the space agency says its Asteroid Initiative will help in the eventual goal of putting people on Mars, what if instead of going to an asteroid, we went to Mars’ moon Phobos?
Three prominent planetary scientists have joined forces in a new paper in the journal Planetary and Space Science to explain the case for a mission to the moons of Mars, particularly Phobos.
“Phobos occupies a unique position physically, scientifically, and programmatically on the road to exploration of the solar system,” say the scientists. In addition, the moons may possibly be a source of in situ resources that could support future human exploration in circum-Mars space or on the Martian surface. But a sample return mission first could provide details on the moons’ origins and makeup.
The Martian moons are riddles, wrapped in a mystery, inside an enigma.Phobos and its sibling Deimos seem like just two asteroids which were captured by the planet Mars, and they remain the last objects of the inner solar system not yet studied with a dedicated mission. But should the moons be explored with flybys or sample-return? Should we consider “boots or bots”?
The publications and mission concepts for Phobos and Deimos are numerous and go back decades. The authors of “The Value of a Phobos Sample Return,” Murchie, Britt, and Pieters, explore the full breadth of questions of why and how to explore Phobos and Deimos.
Dr. Murchie is the principal investigator of the Mars Reconnaissance Orbiter’s CRISM instrument, a visible/infrared imaging spectrometer. He is a planetary scientist from John Hopkins’ Applied Physics Lab (APL) which has been at the forefront of efforts to develop a Phobos mission. Likewise, authors Dr. Britt, from the University of Central Florida, and Dr. Pieters, from Brown University, have partnered with APL and JPL in Phobos/Deimos mission proposals.
An MRO HiRise image of the Martian moon Phobos. Taken on March 23, 2008. Phobos has dimensions of 27 × 22 × 18 km, while Deimos is 15 × 12.2 × 11 km. Both were discovered in 1877 at the US Naval Observatory in Washington, D.C. (Photo: NASA/MRO/HiRISE)
APL scientists are not the only ones interested in Phobos or Deimos. The Jet Propulsion Laboratory, Ames Research Center and the SETI Institute have also proposed several missions to the small moons. Every NASA center has been involved at some level.
But the only mission to actually get off the ground is the Russian Space Agency’s Phobos-GRUNT[ref]. The Russian mission was launched November 9, 2011, and two months later took a bath in the Pacific Ocean. The propulsion system failed to execute the burns necessary to escape the Earth’s gravity and instead, its orbit decayed despite weeks of attempts to activate the spacecraft. But that’s a whole other story.
The Russian-led mission Phobos-Grunt did not end well; under Pacific swells to be exact. Undaunted Russian scientists are pressing for Phobos-Grunt 2 (illus.), an improved lander with sample-return. Proposed for 2020s (Credit: CNES)
“The Value of a Phobos Sample Return” first discusses the origins of the moons of Mars. There is no certainty. There is a strong consensus that Earth’s Moon was born from the collision of a Mars-sized object with Earth not long after Earth’s formation. This is just one possibility for the Martian moons. Murchie explains that the impacts that created the large basins and craters on Mars could have spawned Phobos and Deimos: ejecta that achieved orbit, formed a ring and then coalesced into the small bodies. Alternative theories claim that the moons were captured by Mars from either the inner or outer solar system. Or they could have co-accreted with Mars from the Solar Nebula. Murchie and the co-authors describe the difficulties and implications of each scenario. For example, if captured by Mars, then it is difficult to explain how their orbits came to be “near-circular and near-equatorial with synchronous rotational periods.”
To answer the question of origins, the paper turns to the questions of their nature. Murchie explains that the limited compositional knowledge leaves several possibilities for their origins. They seem like D-type asteroids of the outer asteroid belt. However, the moons of Mars are very dry, void of water, at least on their surfaces as the paper discusses in detail. The flybys of Phobos and Deimos by NASA and ESA spacecraft are simply insufficient for drawing any clear picture of their composition or structure, let alone their origins, Murchie and co-authors explain.
If the moons were captured then they have compositions different from Mars; however if they accreted with or from Mars, then they share similar compositions with the early Mars when forming, or from Martian crustal material, respectively.
The paper describes in some detail the problem that billions of years of Martian dust accumulation presents. Every time Mars has been hit by a large asteroid, a cloud of debris is launched into space. Some falls back to the planet but much ends up in orbit. Each time, some of the debris collided with Phobos and Deimos; Murchie uses the term “Witness plate” to describe what the two moons are to Mars. There is an accumulation of Martian material and also material from the impactors covering the surfaces of the moons. Flyby images of Phobos show a reddish surface similar to Mars, and numerous tracks along the surface as if passing objects struck, plowed or rolled along. However, the reddish hue could be weathering from Solar flux over billions of years.
The paper continues with questions of the composition and how rendezvous missions could go further to understanding the moons makeup and origins, however, it is sample return that would deliver, the pay dirt. Despite how well NASA and ESA engineers have worked to shrink and lighten the instruments that fly, orbit, and land on Mars, returning a sample of Phobos to labs on Earth would permit far more detailed analysis.
SpaceX and Elon Musk claim that they will mount human flight to Mars before 2030. Many others remain less optimistic with hopes of human flights before 2040. (Illustrations: Total Recall, 1990, early artist illustration c.1950s )
Science Fiction writers and mission designers have imagined Phobos, in particular, as a starting point for the human exploration and colonization of Mars. A notable contemporary work is “Red Mars” by Kim Stanley Robinson; however, the story line is dated due to the retirement of the Space Shuttle and the external tanks Robinson clustered to form the colonization vessel. While this paper by Murchie et al. is purely scientific, fiction writers have used the understanding that Phobos is far easier to reach from Earth than is the surface of Mars (see Delta-V chart below).
A diagram showing the stair-step energy needed to travel to places beyond the Earth. Delta-V is the speed in km/sec required to reach a destination. As shown, the Delta-Vs are cumulative. Note that it takes an extra 5 km/sec beyond Phobos to reach the Martian surface; a prime reason for making the journey to the moons of Mars. (Credit: Wikipedia, Delta-V)
Phobos, orbiting at 9,400 kilometers (5,840 miles), and Deimos, at 23,500 km (14,600 miles), above Mars avoids the need for the 7-odd minutes of EDL terror – Entry, Descent, and Landing — and pulling oneself out of the Martian gravity well to return to Earth. Furthermore, there is the interest in using Phobos as a material resource – water, material for rocket fuel or building materials. “The Value of a Phobos Sample Return” discusses the potential of Phobos as a resource for space travelers – “In Situ Resource Utilization” (ISRU), in the context of its composition, how the solar flux may have purged the moons of water or how Martian impact debris covers materials of greater interest and value to explorers.
With so many questions and interests, what missions have been proposed and explored? The Murchie paper describes a half dozen missions but there are several others that have been conceived and proposed to some level over several decades.
At present, there is at least one mission actively pursuing funds. The SETI and Ames proposed “Phobos and Deimos & Mars Environment” (PADME) mission led by Dr. Pascal Lee is competing for Discovery program funding. Such projects must limit cost to $425 million or less and be capable of launching in less than 3 years. They are proposing a launch date of 2018 on a SpaceX Falcon 9. The PADME mission design would reuse Ames LADEE hardware and expertise, however, it does not go so far as what Murchie and co-authors argue – returning a sample from Phobos. PADME would maintain in a synchronized orbit with Phobos and then Deimos foe repeated flybys. The mission is likely to cost in the range of $300 million. Stardust, a relevant mission due to its sample return capsule, launched in 1999 and had costs which likely reached a similar level by end of mission in 2012.
The Russian Space Agency is attempting to gain funding for Phobos-Grunt 2 but possible launch dates continue to be moved back – 2020, 2022, and now possibly 2024.
Return of the Stardust sample inside the Lockheed-Martin developed sample-return capsule. Seen here upon successful landing in the Utah desert. (Credit: NASA/Stardust)
Additionally, each of this papers’ authors has mission proposals described. Dr. Pieters, JPL, and Lockheed-Martin proposed the Aladdin mission; Dr. Britt at APL, also with Lockheed-Martin, proposed the mission Gulliver; both would re-use the Stardust sample-return capsule (photo, above). Dr. Murchie also describes his APL/JPL mission concept called MERLIN (Mars–Moon Exploration, Reconnaissance and Landed Investigation).
Phobos and Deimos are the last two of what one would call major objects of the inner Solar System that have not had dedicated missions of exploration. Several bodies of the Asteroid Belt have been targeted with flybys and Dawn is nearing its second target, the largest of the Asteroids, Ceres.
So sooner rather than later, a spacecraft from some nation (not necessarily the United States) will target the moons of Mars. Targeted Phobos/Deimos missions are also likely to include both flyby missions and one or more sample-return missions. A US-led mission with sample-return in the Discovery program will be strained to meet both criteria – $425 million cost cap and 3 year development period.
Those utilizing the Lockheed-Martin (LM) Stardust design have a proven return capsule and spacecraft buses (structure, mechanisms and avionics) for re-use for cost and time savings. This includes five generations of the LM flight software that holds an incredible legacy of mission successes starting with Mars Odyssey/Genesis/Spitzer to now Maven.
All three proposals by this paper’s authors could be re-vamped and proposed again and compete against each other. All three could use Lockheed-Martin past designs. Cooperation in writing this paper may be an indicator that they will join forces, combine concepts, and share investigator positions on a single NASA-led project. The struggle for federal dollars remains a tough, tight battle and with the human spaceflight program struggling to gain a new footing after Space Shuttle, dollars for inter-planetary missions are likely to remain very competitive. However, it appears a Phobos-Deimos mission is likely within the next ten years.
100 colorful planetary nebulae, at apparent size relative to one another. Image processing and collection by Judy Schmidt.
If you like planetary nebulas, you’re in luck. Multimedia artist Judy Schmidt has put together an amazing collection of 100 of these colorful glowing shells of gas and plasma, all at apparent size relative to one another. There’s even a giant-sized 10,000 pixel-wide version available on Flickr.
How many of these planetary nebulae can you identify?
Judy explained her inspiration for putting together this wonderful ‘poster’:
Inspired by insect illustration posters, this is a large collage of planetary nebulas I put together bit by bit as I processed them. All are presented north up and at apparent size relative to one another–I did not rotate or resize them in order to satisfy compositional aesthetics (if you spot any errors, let me know). Colors are aesthetic choices, especially since most planetary nebulas are imaged with narrowband filters.
Planetary nebulae are formed by certain types of stars at the end of their lives, and actually have nothing to do with planets. They were given the confusing name 300 years ago by William Herschel because in early, rudimentary telescopes, the puffed out balls of gas looked like planets.
Our own Sun will likely undergo a similar process, but not for another 5 billion years or so.
Comet C/2012 K1 PANSTARRS photographed on September 26, 2014 by Rolando Ligustri. Like most comets, we see two tails. K1's dust tails points off to the left, it's gas or ion tail to the right. Credit: Rolando Ligustri
Thank you K1 PanSTARRS for hanging in there! Some comets crumble and fade away. Others linger a few months and move on. But after looping across the night sky for more than a year, this one is nowhere near quitting. Matter of fact, the best is yet to come.
This new visitor from the Oort Cloud making its first passage through the inner solar system, C/2012 K1 was discovered in May 2012 by the Pan-STARRS 1 survey telescope atop Mt. Haleakala in Hawaii at magnitude 19.7. Faint! On its the inbound journey from the Oort Cloud, C/2012 K1 approached with an orbit estimated in the millions of years. Perturbed by its interactions with the planets, its new orbit has been reduced to a mere ~400,000 years. That makes the many observing opportunities PanSTARRS K1 has provided that much more appreciated. No one alive now will ever see the comet again once this performance is over.
Comet C/2012 K1 PanSTARRS’ changing appearance over the past year. Credit upper left clockwise: Carl Hergenrother, Damian Peach, Chris Schur and Rolando Ligustri
Many amateur astronomers first picked up the comet’s trail in the spring of 2013 when it had brightened to around magnitude 13.5. My observing notes from June 2, 2013, read:
“Very small, about 20 arc seconds in diameter. Pretty faint at ~13.5 and moderately condensed but not too difficult at 142x . Well placed in Hercules.” Let’s just say it was a faint, fuzzy blob.
K1 PanSTARRS slowly brightened in Serpens last fall until it was lost in evening twilight. Come January this year it returned to the morning sky a little closer to Earth and Sun and a magnitude brighter. As winter snow gave way to frogs and flowers, the comet rocketedacross Corona Borealis, Bootes and Ursa Major. Its fat, well-condensed coma towed a pair of tails and grew bright enough to spot in binoculars at magnitude 8.5 in late May.
Skywatchers can find C/2012 K1 PanSTARRS in the morning sky in the Hydra and Puppis just before dawn when it’s highest in the southeastern sky. The map shows its location daily with stars to magnitude 8.5. The numbers next to some stars are standard Flamsteed atlas catalog numbers. Click for a larger version. Source: Chris Marriott’s SkyMap
By July, it hid away in the solar glare a second time only to come back swinging in September’s pre-dawn sky. Now in the constellation Hydra and even closer to Earth, C/2012 K1 has further brightened to magnitude 7.5. Though low in the southeast at dawn, I was pleasantly surprised to see it several mornings ago. Through my 15-inch (37-cm) reflector at 64x I saw a fluffy, bright coma punctuated by a brighter, not-quite-stellar nucleus and a faint tail extending 1/4º to the northeast.
Mid-northern observers can watch the comet’s antics through mid-October. From then on, K1 will only be accessible from the far southern U.S. and points south as it makes the rounds of Pictor, Dorado and Horologium. After all this time you might think the comet is ready to depart Earth’s vicinity. Not even. C/2012 K1 will finally make its closest approach to our planet on Halloween (88.6 million miles – 143 million km) when it could easily shine at magnitude 6.5, making it very nearly a naked-eye comet.
PanSTARRS K1’s not giving up anytime soon. Southern skywatchers will keep it in view through the spring of 2015 before it returns to the deep chill from whence it came. After delighting skywatchers for nearly two years, it’ll be hard to let this one go.
Illustration of the Rosetta Missions Philae lander on final approach to a comet surface. (Photo: ESA)
ESA Rosetta mission planners have selected November 12th, one day later than initially planned, for the historic landing of Philae on a comet’s surface. The landing on 67P/Churyumov-Gerasimenko will be especially challenging for the washing machine-sized lander. While mission scientists consider their choice of comet for the mission to be an incredibly good one for scientific investigation and discovery, the irregular shape and rugged terrain also make for a risky landing. The whole landing is not unlike the challenge one faces in shooting a moving target in a carnival arcade game; however, this moving target is 20 kilometers below and it is also rotating.
At 8:35 GMT (3:35 AM EST), the landing sequence will begin with release of Philae by Rosetta at an altitude of 20 kilometers above the comet. The expected time of touchdown is seven hours later – 15:35 GMT (10:35 AM EST). During the descent, Philae’s ROLIS camera will take a continuous series of photos. The comet will complete more than half a rotation during the descent; comet P67’s rotation rate is 12.4 hours. The landing site will actually be on the opposite side of the comet when Philae is released and will rotate around, and if all goes as planned, meet Philae at landing site J.
Before November 12th, mission planners will maintain the option of landing at Site C. If the alternate site is chosen, the descent will begin at 13:04 GMT also on November 12 but from an altitude of 12.5 kilometers, a 4 hour descent time.
NAVCAM image of the comet on 21 September, which includes a view of primary landing site J. Click for more details and link to context image. (Credits: ESA/Rosetta/NAVCAM)
Rosetta will eject Philae with an initial velocity of approximately 2 1/2 kilometers per hour. Because the comet is so small, its gravity will add little additional speed to Philae as it falls to the surface. Philae is essentially on a ballistic trajectory and does not have any means to adjust its path.
The actions taken by Philae’s onboard computer begin only seconds from touchdown. It has a landing propulsion system but unlike conventional systems that slow down the vehicle for soft landing, Philae’s is designed to push the lander snugly onto the comet surface. There is no guarantee that Philae will land on a flat horizontal surface. A slope is probably more likely and the rocket will force the small lander’s three legs onto the slope.
A model of the comet P67/Churyumov-Gerasimenko created using images from the Rosetta OSIRIS narrow field camera. Mouse click on the image to start the animated GIF. (Credit: ESA)
Landing harpoons will be fired that are attached to cables that will be pulled in to also help Philae return upright and attach to the surface. Philae could actually bounce up or topple over if the rocket system and harpoons fail to do their job.
The Philae Lander anchoring harpoon with the integrated MUPUS-accelerometer and temperature sensor. (Credit: “Philae Lander Fact Sheet”, ESA)
However, under each of the three foot pads, there are ice screws that will attempt to drill and secure Philae to the surface. This will depend on the harpoons and/or rockets functioning as planned, otherwise the action of the drills could experience resistance from hard ground and simply push the lander up rather than secure it down. Philae also has a on-board gyro to maintain its attitude during descent, and an impact dampener on the neck of the vehicle which attaches the main body to the landing struts.
Ten landing sites were picked, then down-selected to five, and then finally on September 15th, they selected Site J on the head of the smaller lobe – the head of the rubber duck, with site C as a backup. Uncertainty in the release and the trajectory of the descent to the comet’s surface means that the planners needed to find a square kilometer area for landing. But comet 67P/Churyumov-Gerasimenko simply offered no site with that much flat area clear of cliffs and boulders. Philae will be released to land at Site J which offers some smooth terrain but only about a quarter of the area needed to assure a safe landing. Philae could end up landing on the edge of a cliff or atop a large boulder and topple over.
A ‘color’ view of Comet 67P, from a September 24, 2014 NavCam image. Credits: ESA/Rosetta/NavCam – Processing by Elisabetta Bonora & Marco Faccin.
The Rosetta ground control team will have no means of controlling and adjusting Philae during the descent. This is how it had to be because the light travel time for telecommunications from the spacecraft to Earth does not permit real-time control. The execution time and the command sequence will be delivered to Rosetta days before the November 12th landing. And ground control must maneuver Rosetta with Philae still attached to an exact point in space where the release of Philae must take place. Any inaccuracy in the initial release point will be translated all the way down to the surface and Philae would land some undesired distance away from Site J. However, ground controllers have a month and a half to practice simulations of the landing many times over with a model of the comet’s nucleus. With practice and more observational data between now and the landing, the initial conditions and model of the comet in the computer simulation will improve and raise the likelihood of a close landing to Site J.
Previous Universe Today articles on Rosetta’s Philae:
