Scars on Mars fade … sometimes / Comet-cluster mashup

Curiosity descent and heat shield impact. Best heat shield images are at the end.

It’s only been a couple years, but the blast marks left by the descent stage that delivered the Curiosity rover to Mars as well as it heat shield that protected it have changed markedly in appearance. But not exactly the way you’d think.

This sequence of images shows a blast zone where the sky crane from NASA's Curiosity rover mission hit the ground after setting the rover down in August 2012, and how that dark scar's appearance changed over the subsequent 30 months. Image Credit: NASA/JPL-Caltech/Univ. of Arizona

This sequence of images shows a blast zone where the sky crane from NASA’s Curiosity rover mission hit the ground after setting the rover down in August 2012, and how that dark scar’s appearance changed over the past 30 months. Credit: NASA/JPL-Caltech/Univ. of Arizona

Curiosity was carefully lowered to the Martian surface in August 2012 by a powered descent stage that blasted away bright Mars dust to expose darker material beneath. Shortly before it landed, the probe ejected its heat shield which slammed into the crust some distance away. Once Curiosity landed, the descent stage or sky crane shot away and crash landed as well. Since that time, the winds crisscrossing the Red Planet have gradually re-coated the darkened areas with bright dust.

sequence shows where the rover itself landed. Curiosity disappears after the first two of the seven frames because it drove away. Its wheel tracks heading generally east (toward the left) can be seen in subsequent frames, and they also fade over time. Credit: NASA/JPL

sequence shows where the rover itself landed. Curiosity disappears after the first two of the seven frames because it drove away. Its wheel tracks heading generally east (toward the left) can be seen in subsequent frames, and they also fade over time. Credit: NASA/JPL

You might assume that accumulating dust would erase the scars, and this was true at first. Lately however, the process appears to have reversed itself.

“We expected to see them fade as the wind moved the dust around during the months and years after landing, but we’ve been surprised to see that the rate of change doesn’t appear to be consistent,” said Ingrid Daubar, a HiRISE camera team scientist at NASA’s Jet Propulsion Laboratory who studied images of the blemishes taken by the Mars Reconnaissance Orbiter.

After fading for two years, the rate of change slowed with some areas re-darkening. Scientists are repeatedly checking the blast zones to compare their models against reality, revealing that we still don’ t fully understand how Martian dust is transported around the planet.

MarsBlast Heat shield

Five-frame sequence of the location where the spacecraft’s heat shield hit the ground. Credit: NASA/JPL-Caltech/Univ. of Arizona

Daubar’s work on this aids preparations for NASA’s next Mars lander, InSight, expected to launch in March 2016. The InSight mission will deploy a heat probe that will hammer itself a few yards, or meters, deep into the ground to monitor heat coming from the interior of the planet.

The brightness of the ground affects temperature below ground, because a dark surface warms in sunshine more than a bright one does.

Comet Siding Spring cruises past the bright globular star cluster M92 in Hercules on March 29, 2015. Credit: Rolando Ligustri

Comet Siding Spring cruises past the bright globular star cluster M92 in Hercules on March 29, 2015. Credit: Rolando Ligustri

Now that you’re brain’s completely flickered out after viewing three animations, let me share one additional photo from the weekend that has a Mars connection. It shows the comet C/2013 A1 Siding Spring passing very close in a beautiful way to the globular cluster M92 in the constellation Hercules. Siding Spring swept so close to Mars last fall it created a meteor shower in the planet’s atmosphere. Now it’s juxtaposed again, this time in the foreground of a star cluster that’s 26,700 light years from Earth.

Galaxies, galaxies and more galaxies – 225 billion and counting!

The mysterious old spiral galaxy NGC 524 that has evolved into what astronomers call a lenticular galaxy. Credit: NASA/ESA/Hubble

The mysterious old spiral galaxy NGC 524 that has evolved into what astronomers call a lenticular galaxy. Credit: ESA/Hubble & NASA/Judy Schmidt

Like a spinning hypnotic disk, who can’t resist the spiral swirls of dust that draw your gaze to the core of galaxy NGC 524? It’s one of billions of galaxies that populate the observable universe. Located 90 million light away in the constellation Pisces, this mysterious-looking object is known as a lenticular galaxy.

The lenticular galaxy 4866 seen close to edge-on. Lenticulars have a bright disk of old stars with weak or absent spiral features and a central core or bulge rich in ancient stars. Credit: NASA/ESA/Hubble

The lenticular galaxy NGC 4866 in Virgo seen close to edge-on. Lenticulars have a bright disk of old stars with weak or absent spiral features and a central core or bulge rich in ancient stars. Astronomers classify lenticulars. Credit: NASA/ESA/Hubble

It used to be a spiral galaxy resembling other spirals like our own Milky Way or the Andromeda Galaxy with their vast, pinwheeling arms. Spirals are dotted with hot pink clouds of gas and dust that are the sites of new star formation. Within their folds, gravity hammers dust into new generations of stars. All we have to do to see that our galaxy is actively forming stars is to look to the Orion Nebula below Orion’s Belt. Thousands of newborn stars have recently lit up within this massive interstellar cloud.

At left is the elliptical galaxy M87 in Virgo. The wisp of light near the core is a jet of material powered by a black hole in the galaxy's center. At right is a classic spiral galaxy, M74. Credit: NASA/ESA/Hubble

At left is the elliptical galaxy M87 in Virgo. The wisp of light near the core is a jet of matter ejected by a black hole in the galaxy’s center. At right is a classic spiral galaxy, M74, also located in Pisces. Credit: NASA/ESA/Hubble

Not so in lenticulars. Over time, they either use up or lose to space much of their interstellar dust — the material used to make stars — leaving a nearly featureless disk filled with old red stars and a bright bulge of even older stars in the middle. They’re intermediate in form between spirals and that other major class of galaxies, the ellipticals. Elliptical galaxies are disk-free and comprised almost purely of stars gathered into spheres and ovoids. You can think of them as naked bulges.

Astronomer Edwin Hubble created this diagram in his quest to classify galaxies' diverse forms. The ellipticals (letter "E") are at left, while lenticulars (S0) lie at the juncture of two different branches of spirals, ones without bars (top) and ones with. The Milky Way is a barred spiral galaxy. Credit: Wikipedia

Astronomer Edwin Hubble created this diagram in his quest to classify and understand galaxies’ diverse forms. The ellipticals (letter “E”) are at left. The higher the number, the more flattened their appearance. Lenticulars (S0) lie at the juncture of two different branches of spirals, ones without bars (top) and ones with. The Milky Way is an SBc barred spiral galaxy. Credit: Wikipedia

American astronomer Edwin Hubble wasn’t the first to observe that galaxies have a variety of shapes, but in trying to understand their evolution, he was the first to classify their forms in his famous “tuning fork” diagram in 1926. Although a simplification of the full scheme of galaxies, it’s still the most popular classification system used to this day.

NGC 2787 is an example of a lenticular galaxy with visible dust absorption. While this galaxy has been classified as an S0 galaxy, one can see the difficulty in differentiating between spirals, ellipticals, and lenticulars. Credit: HST

NGC 2787 is an lovely example of a lenticular or S0 galaxy with visible dust absorption. It lies 25 million light years from Earth in Ursa Major. Credit: HST

Hubble thought that galaxies evolved from ellipticals through lenticulars and into spirals. He called ellipticals “early galaxies” and spirals “late galaxies”. While these terms are still used by astronomers, we now know that ellipticals can’t evolve into spirals. Ellipticals appear to arise from mergers of two or more galaxies, and they’re slow rotators. Spirals form from the collapse of massive clouds of dust and gas that rotate rapidly as they flatten into disks.

Spirals, ellipticals, irregulars - 170 billion in all. Credit: NASA/ESA/Hubble

Spirals, ellipticals, irregulars – 170 billion in all! Credit: NASA/ESA/Hubble

Whatever their classification, galaxies possess a delightful array of shapes that show what nature can do when handed a parcel containing little more than interstellar dust and dark matter. It’s estimated that the observable universe contains some 225 billion galaxies. Click the image above for close-ups of a small sample.

Scientists attempt to contact frozen Philae comet lander

You can see one of Philae's landing legs in this photo taken by the probe from the side of a cliff back in November. With more sunlight now flooding the site, there's hope we'll hear from Philae again. Credit: ESA/Rosetta/Philae/CIVA

You can see one of Philae’s landing legs in this photo taken by the probe from the side of a cliff back in November. With more sunlight now flooding the site, there’s hope we’ll hear from Philae again. Credit: ESA/Rosetta/Philae/CIVA

Remember Philae? The little lander has been sitting in a hole between cliffs on Comet 67P/Churyumov-Gerasimenko, but as George Harrison sang – Here Comes the Sun.

Philae (FEE-lay) bounced off the comet’s surface twice while attempting to touch down. On the first bounce, it rebounded at a speed of 15 inches per second, sending it sailing over half a mile above 67P’s surface. Had the lander exceeded 17 inches per second it would have escaped the comet’s gravity!

To get a feel for the alien beauty of Comet 67P, press play to take a flyover.

It finally came to rest on November 12, 2014 after a second bounce. Had the lander’s harpoons worked properly, it would have affixed itself upright on the surface on its first attempt.

After two bounces, Philae landed at an angle in a hole between cliffs on Comet 67P last November. Credit: ESA

After two bounces, Philae (in blue)  landed at an angle in a hole between cliffs on Comet 67P last November. Credit: ESA

Unfortunately, Philae landed in the shadows of cliffs with its solar panels steeped in shadow most of day. With too little sunlight to provide the energy to charge the lander’s batteries, the probe’s primary battery provided only 60 hours power before it shut down. Philae conducted as much data-gathering as it could and then powered down into hibernation mode on Nov. 15. No one’s heard from it since.

Comet 67P photographed with Rosetta's navigation camera on March 21. he image is lightly processed to bring out the details of the outflowing material. Copyright: ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0

Comet 67P photographed with Rosetta’s navigation camera on March 21. The image is lightly processed to bring out the details of streams of dust, water and gas leaving the comet. Copyright: ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0

That might be the end of the story, but mission scientists are hopeful that as seasons change as 67P orbits the Sun (just like they do on Earth), sunlight will filter down between the steep hills at Philae’s location and provide the needed energy for the solar panels to power up the lander’s batteries.  The intensity of sunlight has also been increasing as 67P gets closer to the Sun. A few days of sunlight on the solar panels is all it would take to resume collecting data according to Philae landing manager Stephan Ulmanec.

Same as photo above but this version provides context photos for the close-up images below. Credit: ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0

Same as photo above but this version provides context for the close-up photos featured below, which are newly-released but taken last fall. Credit: ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0

Already the lander is receiving twice as much solar energy as it did last November. Optimistic mission managers recently switched on the communication unit on the Rosetta orbiter to call the lander.

Philae’s like a hibernating black bear during its winter sleep. Before the craft wakes up, its interior temperature has to “warm up” to -49° F (-45° C). Since the mean temperature of the comet’s nucleus is -94° F (-70° C), this bear will sleep a while longer.

The triple cheeseburger feature is a slabby outcropping with a 98-foot (30-meter) boulder perched on its edge. Credit: Same as photo above but this version provides context photos for the close-up images below. Credit: ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0

This slabby outcropping, which reminds me of  a triple cheeseburger, has a 98-foot (30-meter) boulder perched on its edge. Credit: ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0

At its landing site, named Abydos, after one of the oldest cities in ancient Egypt, only a little sunlight shines down each day. Once the solar panels can generate 5.5 watts – less than a typical night light uses – the probe will finally have enough power to begin the wake-up process.

Once the sleep is gone from its eyes, Philae’s next task is to switch on its receiver to listen for Rosetta’s signal. True two-way communication can’t begin until the panels can generate 19 watts of power. Once the link has been reestablished, Rosetta will send the good news back to Earth. For all we know, Philae’s back up in low-power mode but doesn’t have the energy yet for a two-way conversation.

This close-up image has been processed to emphasise the faint nebulosity above the horizon on the right, to show the 'peaks' on the horizon silhouetted against this nebulosity, and to see the deeper, darker shadows they're casting onto the nucleus. Credit: ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0

This close-up has been processed to emphasize the peaks projected against the comet’s hazy atmosphere on the right compared to the deeper, darker shadows they’re casting onto the nucleus. Credit: ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0

Rosetta tried signaling the lander and listening for a response during a favorable alignment between starting March 12th and ending on the 20th. The next chance to hear a possible signal from the lander will be during the first half of April.

Before it went dark, Philae did a stellar job deploying its instruments and gathering as much information as it could about the comet’s alien surface and atmosphere. On its first touchdown attempt and also at its present site, the probe discovered a large amount of water ice beneath the dust-covered surface.

This photo captures some of the smooth Anubis region on the comet's larger lobe. the smooth portions of Anubis appear faulted or folded in some places, and scattered boulders may be the products of mass wasting. Credit: ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0

This photo captures some of the smooth Anubis region on the comet’s larger lobe. Some of the terrain appears faulted or folded, and scattered boulders may have dropped or rolled away from collapsed slopes and cliffs. Credit: ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0

Attempts were made to drill into the crust, gather a sample of soil and deliver it to the lander’s ovens for analysis, but nothing was ever turned up. It’s thought that the lander’s cockeyed position prevented the drill from making contact with the surface. Another instrument, which banged the surface with a hammer, suggest that a veneer of dust 4-8 inches (10-20 cm) thick overlays a thick layer of ice. Organic molecules with carbon and hydrogen were found in the comet’s atmosphere, too.

Philae first touched down where you see the cross. After bouncing, it landed somewhere in the red oval. Scientists still don't know precisely where. Credit: ESA

Philae first touched down where you see the cross. After bouncing, it landed somewhere in the red oval. Scientists still don’t know precisely where. Credit: ESA

We’re eager to hear more from Philae, but the long winter of its discontent must first yield to what passes for spring on a comet.

Auroras may return tonight, Saturday

Aurora near Yellowknife, Northwest Territory, Canada during the big St. Patrick's Day display. Credit: Joe Culler

Amazing curtains of aurora breaking up into rays near Yellowknife, Northwest Territory, Canada during the big St. Patrick’s Day display. Credit: Joe Culler

Thanks to a change-up in the solar wind called a co-rotating interaction region (CIR) followed by more gusty winds from a hole in the Sun’s corona, we have a shot at seeing auroras both tonight and Saturday night. CIRs are compression regions between a slow-flowing solar wind and a fast one. Material can pile up in a CIR, creating delicious auroral havoc upon its arrival at Earth.

Multiple curtains of northern lights float over conifers near Yellowknife during the mid-March aurora storm widely seen across the central and northern U.S. Credit: Joe Culler

Multiple curtains of northern lights float over conifers near Yellowknife during the mid-March aurora storm widely seen across the central and northern U.S. Credit: Joe Culler

NOAA space weather experts are calling for G1 minor geomagnetic storms during the hours leading up to midnight both nights. Minor storms usually mean auroras across the northern parts of the northern states and southern Canada, but as you’re probably aware, the magnetic direction of material coming our way makes a big difference as to whether it creates a storm.

If the south pole of the cloud brushes our magnetic domain, it’s far more likely to connect with Earth’s northward-pointing field. Like magnets snapping together, cloud and Earth-field are drawn to each other. Particles from the Sun can then follow Earth’s magnetic field lines into the polar regions where they strike and excite the atoms that produce the aurora.

ACE plot of magnetic field direction or Bz from last night. You can see how the storm dissipated once the magnetic direction of the cloud changed from south (during the storm) to north (above the white horizontal line). Credit: NASA

ACE plot of magnetic field direction or Bz from a storm last September. You can see how the storm dissipated once the magnetic direction of the cloud changed from south (during the storm) to north (above the white horizontal line). Credit: NASA

I always check the Bz, a measure of whether the arriving solar wind is pointing north or south. When the Bz drops below the centerline and especially if it’s at -10 or lower (south), there’s a fair chance you’ll see northern lights. Click over the ACE satellite page to check to get the lowdown on the Bz. Use the topmost graph with the red squiggly line.

The 8-day-old moon will fill your eyes with craters. Credit: Bob King

The 8-day-old moon will fill your eyes with craters. Credit: Bob King

Unlike the recent St. Patrick’s Day display, which happened in a moonless sky, we have an 8-day-moon to contend with tonight. That’s not an aurora killer but it will reduce contrast. Also, don’t be fooled by a lighter horizon in the northern sky. Normally, that’s a sign of aurora, but moonlight can also make the sky near the horizon appear brighter.

Not that there’s anything wrong with the moon. Now’s the best time to see it in a telescope – it’s high in the south and its current phase shows off a spectacular diversity of craters and land forms.

Let’s hope we get a nice aurora sometime this weekend.

One other tidbit for those following the nova in Sagittarius (Nova Sagittarii 2015 No.2). After fading early this week to around 6th magnitude, it’s rebrightened! I was surprised to see it back up to 5.0 this morning.

G2 cloud survives terror of Milky Way’s black hole

Composite image of the dusty cloud G2 shows it first closing in and then passing the supermassive black hole at the center of the Milky Way. The cloud survived its encounter. The blobs have been colorized to show the motion of the cloud, red for receding and blue for approaching. The cross marks the position of the black hole. Credit: ESO/A. Eckart

Composite image of the dusty cloud G2 shows it first closing in and then passing the supermassive black hole at the center of the Milky Way. The cloud survived its encounter. The blobs have been colorized to show the motion of the cloud, red for receding and blue for approaching. The cross marks the position of the black hole. Credit: ESO/A. Eckart

In the center of the Milky Way galaxy resides a supermassive black hole 4 million times more massive than the Sun. More than enough gravitational might to shred and devour so wispy a thing as a gas cloud orbiting nearby. Yet somehow the cloud survived.

Astronomers have been carefully tracking the motion of the dusty gas cloud called G2 for years, waiting for it to be torn to shreds by the monster black’s hole during peribothron or closest approach last May. To their surprise nothing of the sort happened.

This is an artist's view of what was expected to happen when G2 passed near the Milky Way's supermassive black hole last May. Astronomers assumed it would become stretched and eventually end up down the black hole. Credit: ESO/S. Gillessen/MPE/March/Schartmann

This is an artist’s view of what was expected to happen when G2 passed near the Milky Way’s supermassive black hole last May. Astronomers assumed the black hole’s strong gravity would stretch and devour the cloud. Credit: ESO/S. Gillessen/MPE/March/Schartmann

We’d know if G2 bit the dust because material ripped away would spiral down the black hole’s “throat”, heat up through friction and produce a spectacular fireworks show. So far there hasn’t been a peep. The images of infrared light coming from glowing hydrogen in the cloud show it was compact both before and after its closest approach during its slingshot around the hole. Not even a hint of stretching was detected.

Besides the G2 cloud, this small group of bright stars orbits very near the Milky Way's black hole. Credit: ESO/S. Gillessen et al.

Besides the G2 cloud, this small group of bright stars orbits very near the Milky Way’s black hole. By following the motions of the most central stars over more than 16 years, astronomers were able to determine the mass of the supermassive black hole that lurks there. Credit: ESO/S. Gillessen et al.

Before closest approach, the cloud was travelling away from the Earth at more than 6 million mph (10 million km/hr); after zipping around the black hole, it was approaching the Earth at about 7.5 million mph (12 million km/hr). Throughout the time, astronomers monitored the black hole’s eating habits and recorded no unusual flares or burps during peribothron.

When closest last May, G2 passed 150 times Earth's distance from the Sun from the Milky Way's central black hole. That's about  14 billion miles (22.5 billion km). Credit: ESO

When closest last May, G2 passed 150 times Earth’s distance from the Sun from the Milky Way’s central black hole. That’s about 14 billion miles (22.5 billion km). Credit: ESO

The team, led by Andreas Eckart (University of Cologne, Germany), was amazed that the cloud remained intact. Observations strongly suggest that there’s more there than meets the eye. Now astronomers think the cloud is hiding either a star or a dense, massive core. Both could exerted enough gravity to keep G2 whole despite its close brush with the universe’s ultimate vacuum cleaner.

“We looked at all the recent data and in particular the period in 2014 when the closest approach to the black hole took place. We cannot confirm any significant stretching of the source. It certainly does not behave like a coreless dust cloud. We think it must be a dust-shrouded young star,” said Eckert.

How to find Hydra, the largest constellation in the sky

Hydra the Water Snake unfurls across the southern sky during late March and April evenings. The long constellation begins just below the bright planet Jupiter and coils toward the southeast, crossing the entire summer sky. Source: Stellarium

Hydra the Water Snake unfurls across the southern sky during late March and April evenings. The long constellation begins just below the bright planet Jupiter and coils toward the southeast, crossing the entire southern sky. The map shows the sky facing south around 11 p.m. local time in late March. Source: Stellarium

Hydra the Water Snake is not only the largest of the 88 constellations, it’s also the longest and one of the most ancient. This slender winding pattern of stars is named after the nine-headed serpent Hercules fought as part of his twelve labors. For every head he severed from the serpent, two more grew in its place. Some of us have days like that.

Hydra's coils are beautifully illustrated in Urania's Mirror, a star atlas made in 1825.

Hydra’s coils are beautifully illustrated in Urania’s Mirror, a star atlas made in 1825. Also shown are Crater the Cup, Sextans the Sextant and Corvus the Crow. Noctua the Owl (far left) and Felis the Cat (right) are defunct constellations no longer recognized.

You can get started in your quest to tame this sky snake by finding a place with a wide open view to the south. To see the entire constellation, you’ll need to be out around 11 o’clock in late March or 9:30 p.m. in mid-April. Start with the brilliant planet Jupiter due south at that hour. Not quite a fist below the planet you’ll spy the compact arrangement of five stars that form the snake’s head. From there, it’s an easy drop down to Alphard, Hydra’s solitary bright star, shining pale orange at second magnitude.

Photo showing the serpent on the rise below Jupiter and the constellation Leo. Credit: Bob King

Photo showing Hydra on the rise below Jupiter and the constellation Leo earlier this month. Credit: Bob King

The name Alphard comes from the Arabic al-fard meaning “the solitary one”. Appropriate considering it’s the only relatively bright star in a rather empty region of the sky. Alphard’s a orange giant three times as massive as the Sun and located about 177 light years from Earth.

Hydra is an ancient Greek constellation well known to Plato, Archimedes and their cohorts, but its roots dig deeper in time, all the way back to Babylon. The Mul.Apin tablets, compendium of Babylonian astrology and astronomy written about 1000 B.C., includes a serpent-like constellation called “Mush” that resembles our current Hydra.

Many people don’t care for snakes and water snakes in particular, but Hydra’s home to several fine galaxies and star clusters that we’ll get acquainted with as the ground softens and the first flowers appear later this spring.

Wanted: Names for Pluto’s cracks, cliffs and craters

Not much to name in our current view of Pluto (left). That will all change during the July flyby when New Horizons will image features down to 1 mile (1.6 km) across. Credit: NASA

Not much to name in our current view of Pluto (left). That will all change during the July flyby when New Horizons will image features down to 1 mile (1.6 km) across. Credit: NASA

Here’s your chance to suggest and vote on names for all the newly-discovered craters, cliffs, cracks and gosh-knows-what-else New Horizon’s camera will see when the spacecraft flies past the dwarf planet on July 14. In partnership with the NASA mission and the SETI Institute, the International Astronomical Union (IAU) is endorsing a campaign that will allow the public to participate in naming newly discovered features on Pluto and its satellites.

Charon as depicted by Michelangelo in his fresco The Last Judgment in the Sistine Chapel

Charon depicted by Michelangelo in The Last Judgment. Charon ferried the souls of the newly deceased across the river Styx. Credit: Wikipedia

Not only are they looking for names for Pluto but also its five moons (and likely others that will be discovered). Head over to the Our Pluto website, scroll to the bottom and click on your ballot choice. Here’s the full ballot which includes several lists of suggested names you can vote on.

You can also nominate a name of your own. Your nomination has to fit within a set of accepted themes outlined by the IAU’s Working Group for Planetary System Nomenclature (WGPSN) related to mythology and the literature and history of exploration.

For Pluto, those would be: 
* Names for the Underworld from the world’s mythologies
* Gods, goddesses, and dwarfs associated with the Underworld
* Heroes and other explorers of the Underworld
* Writers associated with Pluto and the Kuiper Belt
* Scientists and engineers associated with Pluto and the Kuiper Belt

Charon:
* Destinations and milestones of fictional space and other exploration
* Fictional and mythological vessels of space and other exploration
* Fictional and mythological voyagers, travelers and explorers

Styx:
* River gods

Nix:
* Deities of the night

The three-headed "hellhound" Kerberos (or Cerberus) from Greek and Roman mythology is the name of one of Pluto's five known moons. Credit: Tom Oates

The three-headed “hellhound” Kerberos (or Cerberus) from Greek and Roman mythology is the name of one of Pluto’s five known moons. Its surface features are hungry for your name suggestions. Credit: Tom Oates

Kerberos:
* Dogs from literature, mythology and history

Hydra:
* Legendary serpents and dragons

These are the only categories in which you can make a nomination. The deadline is April 7. After that the New Horizons team will sort through the entries and send them off to the IAU for final selection. Good luck in choosing and suggesting – I hope they pick your selection!

Colliding stars behind 345-year-old stellar mystery

New observations made with APEX and other telescopes reveal that the star that European astronomers saw appear in the sky in 1670 was not a nova, but a much rarer, violent breed of stellar collision. Credit: Royal Society

New observations made with APEX and other telescopes reveal that the star that European astronomers saw appear in the sky in 1670 was not a nova, but a much rarer, violent breed of stellar collision. Credit: Royal Society

Nova sub capite Cygni or “new star below the head of the Swan”.  That’s how lunar cartographer Hevelius described what he saw one evening in 1670 in the little constellation of Vulpeculae the Fox not far from the star Deneb in the Northern Cross.

It must have taken early astronomers aback, for the new star reached magnitude +2.6, bright enough to alter the constellation’s outline. Unlike many novae, Nova Vulpeculae wouldn’t settle down, rollercoastering up and down in brightness for three years.

Known now as CK Vulpeculae, it was thought until recently to be an unusual nova, but still similar to other novae like the one we’re watching right now in Sagittarius. Novae occur in very close double star systems where one of the companions is a super-dense, Earth-sized star called a white dwarf in orbit around a larger, sun-like star.

The gravity of the dwarf draws material from its companion into a disk which spirals down and accumulates on the star’s exceedingly hot surface. Compressed by gravity and heated by high temperatures, the material ignites in a thermonuclear explosion, causing the star to brighten tens of thousands of times. Suddenly, we look up and see a “new star” in the sky. Of course, what we’re actually seeing is the explosion itself.

That’s what we thought was happening with CK Vul. But it turns out that something far more dramatic has been unfolding all these years, according to a new study of the star by Tomasz Kaminski (ESO and the Max Planck Institute for Radio Astronomy, Bonn, Germany):

This picture shows the remains of the new star that was seen in the year 1670. It was created from a combination of visible-light images from the Gemini telescope (blue), a submillimetre map showing the dust from the SMA (green) and finally a map of the molecular emission from APEX and the SMA (red). Credit: ESO / T. Kaminski

This picture shows the remains of the new star that was seen in the year 1670. It was created from a combination of visible-light images from the Gemini telescope (blue), a submillimetre map showing the dust from the Submillimeter Array or SMA (green) and finally a map of the molecular emission from APEX and the SMA (red). Credit: ESO / T. Kaminski

“For many years this object was thought to be a nova, but the more it was studied the less it looked like an ordinary nova — or indeed any other kind of exploding star.” To crack the mystery of its behavior, astronomers trained large telescopes on the nova but couldn’t find a trace of it until the 1980s, when a faint nebula was finally detected at the location.

More recently, Kaminski and his team probed the area with submillimeter and radio waves and discovered the remnant cloud around the former star was steeped in molecules with an unusual chemical composition. Submillimeter refers to a narrow slice of the spectrum tucked between infrared light and radio waves.

Using the Atacama Pathfinder Experiment telescope or APEX along with other submillimeter and radio telescopes, the team was able to fingerprint the chemical composition and measure the ratios of different isotopes in the gas. Isotopes are different versions of the same element like carbon; they vary only in the number of neutrons in their nuclei.

A view of the Atacama Pathfinder Experiment (APEX). The dish acts like a telescope mirror only it sees the light in the submillimeter and millimeter slice of the spectrum. Credit: ESO

A view of the Atacama Pathfinder Experiment (APEX). The dish acts like a telescope mirror and collects light in the submillimeter and millimeter slice of the spectrum. Credit: ESO

What they discovered led them to an exciting conclusion. The mass of the cool leftover material was too great to have been the product of a nova explosion and the mix of isotopes didn’t match either.

They were led to conclude that CK Vul was nothing less than a spectacular collision between two stars that resulted in their merger. Two become one!

Such a rare event, brighter than a nova but not up to the power of a supernova, is called a red transient. For weeks or months, the explosion appears distinctly red through binoculars or a telescope, hence the name. During the merger, material blasted into space from the stars’ interiors leaves behind a faint remnant rich in molecules and dust.

Red transients make for a small group; one of the brightest was discovered in the galaxy M85 in the constellation Coma Berenices in 2006.

Largest recorded explosion on moon excavates 60-ft. crater

Simulation of the flash of impact on March 17, 2013 when a boulder-sized meteorite excavated a 59-foot-wide crater in the moon's Mare Imbrium. Credit: NASA

Simulation of the flash of impact on March 17, 2013 when a boulder-sized meteorite excavated a 59-foot-wide crater in the moon’s Mare Imbrium. Credit: NASA

Two years ago March 17 an object the size of a small boulder hit the surface of the moon in Mare Imbrium and exploded in a flash of light nearly 10 times as bright as anything ever recorded before. Mare Imbrium is a lunar “sea” that forms the left eye in the Man in the Moon face we see at full moon.

NASA video of the meteorite impact that created a new moon crater

The impact and explosion were recorded with a video camera at NASA’s Marshall Space Flight Center. Based on the brightness of the flash, scientists determined a space rock about a foot wide struck the lunar surface, big enough to hollow out a substantial crater. After pinpointing the impact’s coordinates, the information was relayed to NASA’s Lunar Reconnaissance Orbiter (LRO) team, which then directed the probe to take pictures of the area in hopes of finding a fresh impact scar.

Illustration of the pattern of rays the LRO team discovered which led them to the new crater. Credit: NASA

Illustration of the pattern of rays the LRO team discovered which led them to the new crater. Credit: NASA

Nothing was found at first because the low resolution video images didn’t allow for precision targeting. So the team broadened their search to adjacent swaths of terrain. After several attempts, they noticed something unusual – streaks that looked like faint rays. Could it be part of a classic blast pattern left by impact debris showering down on the moon’s surface?

The new moon crater carved out by a meteorite strike last March 17 measures about 62 feet across. A faint blast pattern surrounds it. Credit: NASA

The new moon crater carved out by a meteorite strike last March 17 measures about 62 feet across. A faint blast pattern extends outward from its rim. Credit: NASA

They did the logical thing and traced the rays back to their convergence point. When the LRO was directed to photograph the new coordinates, immediately a fresh, new crater at the center of that pattern was revealed in photographs sent back to Earth.

This image pairing shows a lunar impact crater created on March 17, 2013. The two images are from the LROC instrument aboard NASA's Lunar Reconnaissance Orbiter. The left image is from Feb. 12, 2012, and the right image is from July 28, 2013. The new crater is about 59 feet wide. Click and drag the slider bar to swipe between the two images. Image Credit: NASA/Goddard Space Flight Center/Arizona State University

This paired photos taken by the LRO show a lunar impact crater created on March 17, 2013. The left image is from Feb. 12, 2012, and the right image from July 28, 2013. The new crater is about 62 feet wide. Credit: NASA/Goddard Space Flight Center/Arizona State University

The crater itself is small, measuring 61.7 feet (18.8 meters) in diameter, but its influence large; debris excavated by the sudden release of energy flew for hundreds of meters. More than 200 related changes, including surface material swept away and smaller secondary impacts, were spotted up to 19 miles (30 km) away. Before and after photos clearly show that less than a year prior, no crater was there.

Watch for the thin crescent moon to join brilliant Venus at dusk in the western sky this evening. Created with Stellarium

Watch for the thin crescent moon to join brilliant Venus at dusk in the western sky this evening. Created with Stellarium

Hundreds of changes have been recorded by the Lunar Reconnaissance Orbiter during its four years at the moon by comparing old and new images called “temporal pairs”. More than 25 new impacts have been discovered this way.

While we’re on the topic, the crescent moon will pass just 3° south or left of Venus this evening in the western sky at dusk. They should make for an attention-grabbing scene. Be sure to look up!

Nova in Sagittarius brightens / Aurora keeps on truckin’

Photo of the Teapot constellation Sagittarius this morning March 21 with the nova. The best time to see it is at the start of dawn when the star is highest in a dark sky. Credit: Bob King

Photo of the Teapot constellation Sagittarius this morning March 21 with the nova. The best time to see it is at the start of dawn when the star is highest in a dark sky. Credit: Bob King

The nova in Sagittarius discovered last week is on its way UP! Since then, it’s brightened to around magnitude 4.5, making it relatively easy to see with the naked eye if you know just where to look. It’s also been christened Nova Sagittarii 2015 No. 2, a temporary designation.

It surprised me this morning at +4.4 — easy to see from a dark sky alongside the spectacular southern Milky Way. It’s uncommon to see one of these stellar explosions with the naked eye. That’s why I encourage you to seize the opportunity. The last time one was this bright was back in August 2013 when Nova Delphini (V339 Del) popped off at +4.3.

This AAVSO chart will not only help you pinpoint the nova but also has stars labeled with their magnitudes or brightness. Decimals are omitted, so a star marked 47 is magnitude +4.7. Credit: AAVSO

This AAVSO chart will not only help you pinpoint the nova but also has stars labeled with their magnitudes or brightness. Decimals are omitted, so a star marked 47 is magnitude +4.7. The PNV title refers to Possible Nova. The nova’s has since been confirmed. Credit: AAVSO

You can use the photo and the AAVSO chart to take you right there. The nova’s not so bright that you can just walk outside and look up and see it. Find a location with a wide open view to the southeast, get oriented in the Teapot and then use binoculars. Once you’ve located the nova this way, try spotting it with your eyes alone.

Checking the list of recent observations submitted by observers with the American Association of Variable Star Observers (AAVSO) the nova’s been trending upward in brightness since discovery. Who knows? There’s a good chance it could brighten further.

Telescope users should keep an eye out for changes in the nova’s color. Right now it’s pale yellow as we see a mix of light from the bluish explosion on the surface of the white dwarf and the red-light-emitting expanding cloud of debris around it. Over time, many novae redden as the explosion plays out and they cool. As with Nova Delphini, color changes over time can be striking and worth the extra effort to follow.

A short, featureless, pulsating arc of aurora from last night. Credit: Bob King

A featureless auroral arc slowly pulsed in brightness low in the northern sky last night March 20. Credit: Bob King

I also wanted to revisit the aurora, which we’ve been revisiting for days now, since it won’t quit! Last night’s weird, pulsating patches continued through at least 3 a.m. this morning, and the space weather experts predict more minor storming early tonight and Sunday night. We’re stuck in an awesome auroral groove fueled by streams of electrons and protons whooshing from the holes in the Sun’s corona unconstrained by solar magnetic fields.

No complaints here!