Mercury is the closest planet to the Sun — so from our point of view, it spends nearly all its time either hidden by the Sun's blinding glare or out of sight below the horizon when the Sun is gone too. But from now through the weekend, you can spot Mercury glittering at its best above the southwest horizon in twilight.
To spot Mercury this coming week, look for a bright "star" along the horizon after sunset, well to the lower left of Altair.
Sky & Telescope diagram
The best time to look will be from about 30 to 60 minutes after your local sunset time. Earlier than that the sky will still be very bright, and later than that Mercury will be sinking very low. But during that window, you should have no trouble if your southwestern sky is clear.
There's a legend that Copernicus himself never saw Mercury. It's almost certainly false, even given his high latitude and foggy weather (on the north coast of what is now Poland) that would have made Mercury more difficult than for most of us. But the story does highlight Mercury's elusiveness. It's in this good an evening view for just two or three weeks a year, and even then for less than an hour out of every 24.
You'll need to find an open view to the southwest. If Mercury is hidden behind buildings or trees, spot Altair higher in the west-southwest. Hold your fist out at arm's length. The area of sky you want to see is lower left of Altair by about three fists at arm's length (30°).
After Sunday January 3rd, Mercury will remain almost as high in twilight for another week, but it will fade very rapidly. It shines at magnitude –0.5 to 0.0 from December 30th through January 3rd, but dims to a mere 2nd magnitude by January 8th.
Mercury is the only bright planet these evenings, but bigger things await later at night. By midnight, Jupiter is up and blazing low in the east. And after the midnight celebrations on New Year's Eve, you'll find the Moon shining eerily below it.
Comet Catalina Encounters Solar Magnetic Storm! (December 13, 2015) by Tony Philips
Earth isn't the only place with geomagnetic storms. Comets can have them, too. Such a storm appears to be underway in the sinuous blue ion tail of Comet Catalina (C/2013 US10). Note the bright blobs of plasma at various points in the tail of the comet in this photo taken by Michael Jäger of Jauerling, Austria on Dec 11th:
These blobs are a sign of stormy space weather. Observers of comets frequently witness plasma blobs and 'disconnection events' in response to CMEs and gusts of solar wind. In extreme cases, a comet's tail can be completely torn off
The underlying physics is akin to terrestrial geomagnetic storms. When magnetic fields around a comet bump into oppositely-directed magnetic fields in a CME, those fields can link together or "reconnect." The resulting burst of magnetic energy can make waves, blobs, or even ruptures in the comet's tail. When CMEs hit Earth, a similar process takes place in the planet's magnetosphere powering, among other things, the aurora borealis.
Comet Catalina is brightening in the eastern pre-dawn sky, not yet visible to the naked eye, but an easy target for backyard telescopes.
Supermassive Black Hole Chows Down (December 1, 2015)
Don't ask me to pick up the tab for S5 0716+71
— no way can I afford its voracious appetite. With no warning, this otherwise fastidious and faint stellar pinpoint in the circumpolar constellation Camelopardalis rose from magnitude +13.7 to +12.5 within a week. A sure sign it's feeding again.
The cause of this sudden surge in brightness is a supermassive black hole
feasting on matter from its host galaxy, an invisible bit of fluff located 3.75 billion
light-years from home in Camelopardalis.
This artist's concept shows a "feeding," or active, supermassive black hole, accretion disk, and a jet streaming outward at nearly the speed of light. Not all black holes have jets, but when they do, the jets can be pointed in any direction. If a jet happens to shine at Earth, the object is called a blazar. When seen from the side, it's a quasar.
NASA / JPL-Caltech
S5 0716+71 belongs to a class of violently-variable, active galactic nuclei
(AGN) called blazars
. Like quasars
, blazars begin with a supermassive black hole at the center of a distant galaxy feeding on interstellar dust, rogue planets, and the occasional stray star. As the doomed object falls into the gravitational trap, it's shredded, compressed, and heated to millions of degrees to join its cohorts in a swirling vortex or accretion disk centered on the black hole.
S5 0716+71 is the blue star-like object at center of this 14′ x 14′ wide photo chart. Its current bright outburst started at the end of October. Its host galaxy, 5.4 arcseconds in diameter, is too faint to see even in large telescopes.DSS2 / Stefan Karge
Much of the material within the disk ultimately spirals down the hole, but some of it gets whipped up by powerful magnetic fields generated within the rapidly spinning disk into a pair of relativistic jets. Any matter caught within a jet gets blasted hundreds of thousands of light years into space at 95 to 99% the speed of light.
S5 0716+71 is the blue star-like object at center of this 14′ x 14′ wide photo chart. Its current bright outburst started at the end of October. Its host galaxy, 5.4 arcseconds in diameter, is too faint to see even in large telescopes.
DSS2 / Stefan Karge
We now understand blazars and quasars as two sides of the same coin: In a quasar, we view the AGN from the side; in a blazar we stare directly or nearly so into the jet. Observing a blazar is akin to someone shining a flashlight right in your face.
Because we see the jet almost square on, blobs of material within it can exhibit superluminal motion
. As they travel toward us at nearly the speed of light, they keep pace with the light they emit. From our perspective, the difference in time of arrival between the two happens over a much shorter time frame, creating the illusion of faster-than-light travel. In October 2011
, a team of astronomers observed a superluminal knot of material in S5 0716+71 traveling at an apparent speed ~21 times light speed!
Comet Catalina C/2013 Finally Visible for Northern Observers! (November 20, 2015)
by Bob King
Click on the image for a better view. Comet Catalina C/2013 has finally popped into view in deep morning twilight in the eastern sky after passing through its closest approach to the sun back on November 15th. In this image, the comet was photographed from high atop the Himalayas by Ajay Talwar with a 200mm lens on a tracking mount early on the morning of Nov. 20, 2015. Copyright: Ajay Talwar
If you love watching comets and live north of the equator, you’ve been holding your breath a l-o-n-g time for C/2013 US10 Catalina to make its northern debut. I’m thrilled to report the wait is over. The comet just passed perihelion on Nov. 15th and has begun its climb into morning twilight.
The first post-perihelion photo, taken on Nov. 19th by astrophotographer Ajay Talwar from Devasthal Observatory high in the Indian Himalayas, show it as a starry dot with a hint of a tail only 1° above the eastern horizon at mid-twilight. Additional photos made on the following mornings show the comet inching up from the eastern horizon into better view. Estimates of its current brightness range from magnitude +6.8-7.0.
Sometimes black and white is better. This is the same chart as above but in a handier version for use at the telescope. Source: Chris Marriott’s SkyMap
Talwar, who teaches astrophotography classes and is a regular contributor to The World at Night (TWAN), drove 9 hours from his home to the Himalaya mountains, then climbed up the observatory dome to get enough horizon to photograph the comet. The window of opportunity was very narrow; Talwar had only 10 minutes to bag his images before the comet was overwhelmed by zodiacal light and twilight glow. When asked if it was visible in binoculars, he thought it would be but had too little time to check despite bringing a pair along.
Even before perihelion, Comet Catalina was a beautiful thing. This photo was taken on October 1, 2015 by Jose Chambo.
A difficult object at the moment, once it frees itself from the horizon haze in about a week, Catalina should be easily visible in ordinary binoculars. Watch for it to gradually brighten through the end of the year, peaking around magnitude +5 in late December and early January, when it will be well-placed high in the northeastern sky near the star Arcturus (see map). Matter of fact, on the first morning of the new year, it creeps only 1/2° southwest of the star for a splendid conjunction.
Comet C/2013 US10 Catalina will slice through the plane of the Solar System at an angle of 149° never to return. It comes closest to Earth on Jan. 12, 2016. After that time, the comet will recede and fade. Credit: JPL Horizons
Halloween 2013 was an auspicious one. That’s when Comet C/2013 US10 was first picked up by the Catalina Sky Survey. The “US10” part comes from initial observations that suggested it was an asteroid. Additional photos and observations instead revealed a fuzzy comet on a steeply tilted orbit headed for the inner Solar System after a long sojourn in the Oort Cloud.
Its sun-ward journey has been nothing short of legendary, requiring several million years of inbound travel from the frigid fringe to the relative warmth of the inner Solar System. Catalina will pass closest to Earth on Jan. 12th at 66.9 million miles (107.7 million km) before buzzing off into interstellar space. Yes, interstellar. Perturbations by the planets have converted its orbit into a one-way ticket out of here.
Check this out! Look to the east at the start of dawn on Dec. 7th to see a remarkable pairing of comet, Venus and the waning lunar crescent with earthshine. Source: Stellarium
When using the maps above, keep in mind they show the comet’s changing position, but the constellations and planets can only be shown for the one date, Nov. 21st. Like the comet, they’ll also be slowly sliding upward in the coming days and mornings due to Earth’s revolution around the Sun; stars that are near the horizon on Nov. 21 at 5:30 or 6 a.m. will be considerably higher up in a darker sky by the same time in December. Adding the shift of the stars to that of the comet, Catalina gains about 1° of altitude per day in the coming two weeks.
When you go out to find Catalina in binoculars, note its location on the map and then use the stars as steppingstones, starting with a bright obvious one like Spica and “stepping” from there to the next until you arrive at the one closest to the comet.
I’m so looking forward to finding Catalina. Nothing like a potentially naked eye comet to warm up those cold December mornings. Mark your calendar for the morning of Dec. 7th, when this rare visitor will join Venus and the crescent Moon in the east at the start of morning twilight. See you in spirit at dawn!
Artificial Object in Trans-lunar Orbit to Impact Earth on November 13 (November 2, 2015)
by Bob King
Get ready for a man-made fireball. A object discovered by the Catalina Sky Survey on Oct 3rd temporarily designated WT1190F is predicted to impact the Earth about 60 miles (100 km) of the southern coast of Sri Lanka around 6:20 Universal Time (12:20 a.m CST) on November 13. The objects orbits Earth with a period of about three weeks. Because it was also observed twice in 2013 by the same survey team, astronomers have the data they need to model its orbit and trajectory, and as far anyone can tell, it’s likely man-made.
Solar radiation pressure, the physical “push” exerted by photons of sunlight, is proportional to a space object’s area-to-mass ratio. Small, lightweight objects get pushed around more easily than heavier, denser ones. Taking that factor into account in examining WT1190F’s motion over two years, the survey team has indirectly measured WT1190F’s density at about 10% that of water. This is too low to be a typical asteroid made of rock, but a good fit with a hollow shell, possibly the upper stage of a rocket.
It’s also quite small, at most only about six feet or a couple of meters in diameter. Most or all of it is likely to burn up upon re-entry, creating a spectacular show for anyone near the scene. During the next week and a half, the European Space Agency’s NEO (Near-Earth Object) Coordination Center is organizing observing campaigns to collect as much data as possible on the object, according to a posting on their website. The agency has two goals: to better understand satellite re-entries from high orbits and to use the opportunity to test our readiness for a possible future event involving a real asteroid. The latter happened once before when 2008 TC3 (a real asteroid) was spotted on October 6, 2008 and predicted to strike Earth the very next day. Incredibly, it did and peppered the Sudan with meteorites that were later recovered.
Assuming WT1190F is artificial, its trans-lunar orbit (orbit that carries it beyond the Moon) hints at several possibilities. Third stages from the Saturn-V rockets that launched the Apollo missions to the Moon are still out there. It could also be a stage from one of the old Russian or more recent Chinese lunar missions. Even rockets used to give interplanetary probes a final push are game.
Case in point. What was thought initially to be anew asteroid discovered by amateur astronomer Bill Yeung on September 3, 2002 proved a much better fit with an Apollo 12 S-IVB (third) stage after University of Arizona astronomers found that spectra taken of the object strongly correlated with absorption features seen in a combination of man-made materials including white paint, black paint, and aluminum, all consistent with Saturn V rockets.
Apollo 13’s booster was the first deliberately crashed into the Moon, where it blew out it a crisp, 98-foot-wide (30-meter) crater. Why do such a crazy thing? What better way to test the seismometers left by the Apollo 12 crew? All subsequent boosters ended their lives similarly in the name of seismography. Third stages from earlier missions — Apollos 8, 10 and 11 — entered orbit around the Sun, while Apollo 12, which orbiting Earth, briefly masqueraded as asteroid J002E3.
Bill Gray at Project Pluto has a page up about the November 13 impact of WT1190F with more information. Satellite and asteroid watchers are hoping to track the object before and right up until it burns up in the atmosphere. Currently, it’s extremely faint and moving eastward in Orion. You can click HERE for an ephemeris giving its position at the JPL Horizons site. How exciting if we could see whatever’s coming down before its demise on Friday the 13th!
Planets Meet in the Morning Sky
(September 29, 2015)
Planets are gathering in the morning sky. Venus and Jupiter have recently emerged as morning "stars," rising in the east ahead of the sun, joining Mars in an array of lights that lets early risers view 1/3rd of the solar system at a glance. The display will continue--and improve--as autumn unfolds. This was the view on Sept. 10th:
Jean-Baptiste Feldmann took the picture from Nuits-Saint-Georges, France, just before sunrise on Thursday. At the time, the crescent Moon was passing by Venus en route to Jupiter, adding its luster to that of the planets. "It was a beautiful view," says Feldmann.
More scenes like this are in the offing. On Oct. 8th the crescent Moon will have another close encounter with Venus (sky map), followed one day later by a near miss of Jupiter and Mars (sky map). Every morning thereafter, the planets will converge until Oct. 24th - Oct. 29th when they fit within a circle only 5o wide (sky maps: #1, #2, #3, #4, #5, #6). Typical binoculars can see a patch of sky about 6o or 7o degrees wide. So when the triangle of planets shrinks to 5o, they will fit together inside a binocular field of view. Imagine looking through the eyepiece and seeing three planets--all at once.
By the time October comes to an end, the planetary triangle will start breaking apart. But there are still two dates of special interest: Nov. 6th and 7th (sky maps:#1, #2). On those increasingly wintry mornings, the crescent Moon will swoop in among the dispersing planets for a loose but beautiful conjunction.
Look east before sunrise. There's a lot to see.
Comet 67P Churyumov-Gerasimenko Reaching Peak Brightness - Visible in Amateur Telescopes! (August 24, 2015)
We've waited a long time for this. Looked at hundreds of close-up photos of Comet 67P/Churyumov-Gerasimenko taken by the Rosetta spacecraft since it arrived at the comet a year ago this month. Now it's time to put real comet photons in our eyes. Right here. On Earth.
During this perihelion week up through early next month, 67P/C-G will crest at around magnitude +12 in the pre-dawn sky. This week, the pesky but ravishing crescent Moon transitions to the evening sky, leaving mornings free to track down the comet under dark skies.
67P/C-G canters across Gemini this month and early next, favoring Northern Hemisphere skywatchers, though not by much! Observers with big Dobs will more than likely have to assume the "praying position" with knees on the ground for a good look. I know I did. But it was worth every bit of strain.
Comet 67P/Churyumov-Gerasimenko photographed on August 9, 2015. The comet is a small, 12th magnitude, moderately condensed fuzzball in amateur telescopes. Photographs show a short tail trailing to the west.
Amateur astronomers participating in the Pro-Amateur Collaborative Astronomy (PACA) campaign have been following the comet since March 2014 when it glowed at an anemic magnitude +21. After solar conjunction on Feb. 10, 2015, it was recovered in mid-April low in the morning sky at 17th magnitude. 67P/C-G continued to slowly brighten through the spring and early summer en route to its August 13th perihelion. One of the first visual observations of the comet was made by Chris Wyatt of Walcha, New South Wales, Australia, who called it diffuse, about 30″ across, and magnitude 14.2 on June 23rd.Since then, the trickle of Earth-based observations has quickly become a flood as amateurs and professionals alike take advantage of the incredible opportunity to coordinate their visual observations, photos and spectra with Rosetta's in-situ measurements. If you'd like to join the campaign, there's no time like now. Sign up right here.
Comet 67P/Churyumov-Gerasimenko's path parallels the ecliptic. This map shows its location from mid-July to late November as seen from the northern hemisphere. The comet remains a morning sky object throughout.
Source: Chris Marriott's SkyMap
From my latitude of +42°, long summer twilights, a small elongation, and extreme faintness kept the comet off-limits until last weekend. But from here on out, it's smooth sailing as the famed fuzzy iceberg climbs higher and higher up the dark sky ladder during late summer and fall. The moonless periods from August 12-27 and Sept. 10-26 will be your best times to look. By late September, 67P/C-G will still be visible but fading, as its distance from the Sun continues to increase.
Light curve and prediction of Comet 67P's brightness from Seiichi Yoshida's Weekly Comet Information site. In his updated analysis, the comet will peak around magnitude +12 later this month. The horizontal axis shows the date; the vertical the magnitude.
While the comet rises by 3:30 AM now, it is best to wait for it to rise out of the eastern horizon haze. By the time dawn's light first makes its faint presence known early these mornings (~4:50 AM) the comet is now a user-friendly 16° high and the view has sharpened with the comet much more distinct. Using a magnification to 245x with my 8" Schmitt-Cassegrain reflector on Sunday morning, I saw a moderately condensed, round, milky glow about 0.7′ across with a magnitude of +12.5. That lovely little tadpole tail that shows so well in recent photos was sadly beyond my scope and these eyes.
Comet observers often describe how dense or bright a comet appears using a degree of condensation (DC) scale numbered from 0 to 9, with a DC of 0 being a flat profile coma with no central brightening and a DC of 9 being a completely stellar object. 67P/C-G's current DC is 4 or 5, depending on the observer and equipment.
Back on August 6th, the comet joined Gemini's bright star cluster M35.
Realizing that the Rosetta spacecraft was buried somewhere within the comet's coma gave me the greatest thrill. That and watching it crawl eastward among the stars like some fuzzy caterpillar looking for a meal. To my surprise, high power revealed motion in just 20 minutes. Watching an object like a comet or asteroid move against the stars adds excitement to an observation and makes it that much more real.
As of August 24th, the comet is located near the center of the constellation Gemini and is moving eastward.
Here is a more detailed finder chart of the comet's location for the last half of August 2015. Click on the image for a much larger PDF version.
Jupiter and Venus Hook Up! (June 30, 2015)
Look up! The brightest and best planet pairing of the year is underway in the western sky at dusk. Venus and Jupiter have been near one another for months; they’ll finally squeeze closest together tomorrow night (June 30). But you needn’t wait till then. Tonight, the dynamic duo will be just over 1/2° apart, the width of a full moon. Plenty tight.
Seeing the the solar system’s two brightest planets side by side will make for a fantastic sight at dusk. You can start watching shortly after sunset, but they’ll appear most dramatic in a darker sky an hour to 75 minutes later.
Closest approach occurs tomorrow evening when Venus and Jupiter will be just two-thirds of a moon diameter apart. Your little finger extended at arm’s length covers 1° of sky or twice the width of a full moon. Not until Friday will the two planets pull far enough apart again to fit your pinkie between them. Give it a try.
The view facing west-northwest about 50 minutes after sunset on June 30 when Venus and Jupiter will be at their closest. Two celestial bodies are said to be in conjunction when they have the same right ascension or “longitude”and line up one atop the other. Source: Stellarium
When two planets or a combination of moon and planets align closely in the sky, they’re in conjunction. Lots of conjunctions happen every year. Heck, the moon’s in conjunction with each of the seven planets once a month. What makes this one special is that it involves the two brightest planets in an especially close conjunction. These happen more rarely, and we can’t help but be drawn in. Shiny alignments catch the eye. More than that, they’re beautiful to behold like wild orchids in the forest.
Clouds expected tomorrow night? The conjunction will be nearly as fine tonight and July 1. Times and separations shown for central North America at 10 p.m. CDT. 30 minutes of arc or 30′ equals one Full Moon diameter. Source: Stellarium - CLICK TO ENLARGE.
You can take in the conjunction with the naked eye, binoculars or telescope. Because Venus and Jupiter are so close, those with even the smallest telescopes will experience the unique pleasure of seeing both in the same magnified field of view. Though Jupiter is currently 11 times farther from Earth than Venus, they have the same apparent size because Jove is so much larger.
Venus goes through phases like the moon and will look like a brilliant white crescent. Be sure to look for Jupiter’s four brightest moons on eithe side of the planet tomorrow evening.
The view through a small telescope of Jupiter (top) and Venus on June 30 around 9:30 p.m. CDT. Jupiter’s moons are G = Ganymede, E = Europa, I = Io and C = Callisto. Source: Stellarium
To capture an image of our planetary pals try using your cellphone. First, find a pretty scene to frame the pair. Hold your phone rock-solid steady against a post or building and click away starting about an hour after sundown when the two planets have good contrast with the sky, but with light still about. If your pictures appear too dark or light, manually adjust the exposure. Here’s a youtube video on how to do it with an iPhone.
Point-and-shoot camera owners should place their camera on a tripod, adjust the ISO or sensitivity to 100, open the aperture or f/stop to its widest setting (f/2.8 or f/4), autofocus on the planets and expose from 5-10 seconds in mid-twilight or about 1 hour to 90 minutes after sunset. The low ISO is necessary to keep the images from turning grainy. High-end digital SLR cameras have no such limitations and can be used at ISO 1600 or higher. As always, review the back screen to make sure you’re exposing properly.
Wishing you clear skies as always!
Mystery of Bright Spots on Asteroid Ceres Solved? (December 12, 2015) by Kelly Beatty
A patchwork of bright splashes inside Occator crater on Ceres continues to puzzle planetary scientists. NASA's Dawn spacecraft recorded this composite view in August 2015.
NASA / JPL / UCLA / MPS / DLR / IDA
Everyone loves a good mystery, planetary scientists included. For the past decade they've wondered about a solitary white spot seen on the surface of asteroid 1 Ceres. It first appeared in infrared views acquired from the ground
with the Keck II telescope in 2002, then in Hubble images taken in 2005
Aside from its brightness, researchers didn't have much to go on, so they put the puzzle aside knowing thatNASA's Dawn spacecraft
would eventually reveal the spot in glorious detail. Dawn arrived at Ceres last March, and that solitary spot became evident
in its onboard camera months before that.
In time, as the spacecraft drew nearer, mission scientists realized that Ceres veritably bristled with more than 130 bright spots, most associated with impact craters. But none was as large, as bright, or as distinctive as the Big One, which turned out to lie inside a 90-km-wide crater now named Occator. Close-up views show the spot to be more of a splash, with its bright core corresponding to a pit about 10 km across. ("Bright" is relative: the big spot's core has a reflectivity of 25%, compared to less than 4% for the carbon-infused material covering the rest of Ceres.)
But what is
that stuff? Speculation has run wild. Contests have sprung up.
One pundit proposedeight possible causes
, among them "aliens' solar concentrators."Well, not likely. But a new analysis in December 10th's Nature
certainly narrows the possibilities. A team led by Andreas Nathues (Max Planck Institute for Solar System Research) started with three possibilities: water ice, iron-depleted clay minerals, or salt deposits.
Water ice has had the inside track for some time. Ground-based spectroscopists had detected water-containing minerals more than a decade ago, and Ceres' relatively low density (2.1 g/cm3
) and shape suggest that it contains plenty of water ice and that pretty much all of it must be on the outside
. Back in July, Dawn principal investigator Chris Russell even divulged that the spacecraft had been noticing occasional hazes inside Occator
dense enough to shroud its interior.
The Case for SaltsNathues and his colleagues base their analysis on views from Dawn's Framing Camera, which has seven narrowband filters at visible and near-infrared wavelengths. That's a useful but not particularly diagnostic spectroscopic capability. In fact, the team notes their identification of specific compounds "must be considered tentative."
Still, a modest dip near 0.8 micron in the spectrum of the Occator spot's center isn't a good match for either water ice (which is spectrally bland at those wavelengths) or likely clay minerals. But it's a better fit to hexahydrite,
a magnesium-sulfate salt that locks up six water molecules for each molecule of salt.
Compositional differences are accentuated in this false-color composite of blue, red, and near-infrared images taken by NASA's Dawn spacecraft. Bright spots, like those inside Occator crater and elsewhere, appear more bluish than their surroundings. Preliminary evidence suggests that salts are concentrated in the spots. Click here to see a video that shows this map as a rotating globe and a close-in flyover of Occator crater.
Nature / A. Nathues et al.
Apparently briny fluids are oozing from the interior onto the floor of Occator, whose estimated age is only 78 million years. There's no real gushing — Dawn hasn't detected any geyser-like plumes. Instead, the Sun-warmed brines give up their water through sublimation. The vapor gently lifts away from the surface, carrying with it fine dust particles. It's not much, perhaps a bucketful of water per second during daylight, but enough to form the hazes seen inside the crater. And the brine's salts are largely left behind as bright stains on the otherwise dark surface.
Of course, how Ceres manages to keep the salty fluids in liquid form below the surface — and yet not very far down — is perhaps an even bigger question. Does a briny ocean lie hidden beneath Ceres' dark exterior? If so, what keeps it from freezing, since there's nothing near Ceres to pump tidal energy into its interior.
More confident answers might be coming soon. First, Dawn is just days away from reaching its final and lowest mapping orbit, and from an altitude of 375 km (233 miles) it will circle Ceres every 5½ hours. So even more detailed images of the bright spot are coming soon.
Second, the compositional questions will get easier once Dawn's visible and infrared spectrometer (VIR) can probe the spots individually. VIR obtains spectra in 432 channels from 0.95 to 5.0 microns — the kind of spectral horsepower that should make disentangling the composition of the bright spots much easier.
In fact, in a companion Nature paper
, Maria Cristina De Sanctis (INAF/IAPS, Rome) and others use Dawn's VIR spectra to reveal that clay minerals called ammoniated phyllosilicates are widespread across Ceres' surface — yet the instrument has yet to detect any exposed water ice.
Eventually we'll hear from Dawn's third instrument, a gamma-ray and neutron spectrometer called GRaND, which can detect buried water ice. But GRaND's field of view is very wide, and it needs to be close to Ceres to get meaningful results.
So the mysteries continue — does anyone still want to bet that the spots are aliens' solar concentrators?
Moon Pays a Visit to Venus and Comet Catalina on Monday (December 3, 2015)
by Bob King
The Moon joins Venus prior to the occultation in the company of Comet Catalina (C/2013 US10) just before the start of dawn on December 7th.
Mark your calendars. In less than a week, we're in for a double treat. Before dawn on Monday, December 7, 2015, the crescent Moon parks right next to Venus with Comet Catalina
a stone's throw away. From the central United States, the comet lies just 4° northeast of Venus and 5° from the lunar crescent. Hours later, the Moon occults
Venus for most of North and Central America and the Caribbean.
With a nearby Moon and the comet currently around magnitude +6, you're not likely to see it with the naked eye, but it will be an easy sight in binoculars from suburban and rural skies. Bonus! Wide-field glasses will corral all three celestial bodies in one field of view.
To make sure you see Catalina, first focus sharply on the Moon then ease it just outside the field of view to the right; now look for a fuzzy spot with a brighter center on the opposite (left) side of the field.
Now go back to bed and get some rest. Or have breakfast and go to work, but don't forget to sneak out for a coffee break shortly that morning or early afternoon (depending on your time zone) when the bright limb of the waning crescent Moon begins to nibble away at the gibbous Venus. It will take just under a minute for Venus to "set" behind the Moon, a sight reserved for those with a small telescope or large binoculars. You'll find the Moon about 40° west of the Sun and either in the southwestern sky (from the eastern half of the viewing area) or in the south-southeastern sky (from the western half).
Simulated view of the crescent Moon closing in on Venus shortly before the start of Monday's occultation. Venus will be 69% illuminated and 16.6″ across.
Most of us will either be in school or at work on a Monday, so bring along those binoculars. Finding Venus with the naked eye will be easy thanks to the Moon being so close. Look immediately to the left and a little above (north) of the crescent. Will you be able to see the planet right up to and during occultation? I suspect you will.
Simulated view of the start of the December 7th occultation seen from the central U.S. around 11 a.m. CST. The lunar crescent will appear faint at mid-day. Look about 40° or "four fists" to the right (west) of the Sun to find it.
Overall, the Moon will be brighter at magnitude –8.8 vs. –4.2 for Venus, but the planet always wins out because of its much higher surface brightness; swaddled in clouds, it makes a far better reflector than the Moon's charcoal-toned dust and rocks. The contrast between them is quite striking to the eye.
Venus is pinned to the edge of the waning crescent moments before the start of the April 22, 2009, occultation. Skywatchers in the far northwestern U.S. and Canada will see Monday's event in a similar dark sky.
Some lucky skywatchers will get to see the entire event in a dark sky. If you're reading this from northwestern North America including Alaska, Yukon, British Columbia, and the Northwest Territories, that's you! Darkness will add dramatic contrast to the occultation. A low Moon at those far northern latitudes also means abundant celestial-meets-terrestrial landscape photo opportunities. Don't forget an extra set of fresh (warm) batteries.
This color-coded map shows where the Venus-Moon occultation will be visible. Cyan = occultation at moonrise/moonset; red dotted = daytime occultation; blue = twilight occultation and white = nighttime occultation. Click photo for disappearance and reappearance times for many cities in the far northwest where it will be dark.
Here are occultation start times and end times (in parentheses), accurate to 1-2 minutes, for 20 U.S. cities on December 7th. Venus disappears at the Moon's bright limb and emerges from behind the dark limb as the Moon travels from west to east across the sky. The Moon will be too low to see emersion from cities in the northeastern U.S. and eastern Canada.
Boston, MA — 12:42 p.m. EST (1:46 p.m.)
Atlanta, GA —12:31 p.m. EST (1:57 p.m.)
Miami, FL —12:51 p.m. EST (2:16 p.m.)
Cleveland, OH —12:29 p.m. EST (1:40 p.m.)
Indianapolis, IN —12:22 p.m. EST (1:39 p.m.)
Jackson, MS —11:21 a.m. CST (12:54 p.m.)
Chicago, IL —11:17 a.m. CST (12:32 p.m.)
Minneapolis, MN —11:03 a.m. CST (12:15 p.m.)
New Orleans, LA —11:24 a.m. CST (12:59 p.m.)
Oklahoma City, OK 10:58 a.m. CST (12:35 p.m.)
Denver, CO — 9:35 a.m. MST (11:12 a.m.)
Billings, MT — 9:24 a.m. MST (10:51 a.m.)
Albuquerque, NM — 9:33 a.m. MST (11:19 a.m.)
Tucson, AZ — 9:23 a.m. MST (11:14 a.m.)
Las Vegas, NV — 8:09 a.m. PST (9:58 a.m.)
Seattle, WA — 7:53 a.m. PST (9:25 a.m.)
San Fransisco, CA — 7:52 a.m. PST (9:37 a.m.)
Los Angeles, CA — 8:03 a.m. PST (9:53 a.m.)
Fairbanks, AK — 6:42 a.m. AKST (7:48 a.m.)
Anchorage, AK — 6:34 a.m. AKST (7:46 a.m.)
Composite image of the daylight occultation of Venus by the waning crescent Moon on August 13, 2012. Taken with a130mm Astro-Physics refractor and 2X Barlow for f/12 and focal length of 1600mm, ISO 400, and 1/400 second.
Alan Dyer / AmazingSky.com
Notice how long it takes for Venus to reappear, often more than 90 minutes. There are at least two reasons for this: Venus is also moving east, forcing the Moon to "chase it down," and the Moon is just two days past apogee — the most distant point in its orbit — when it travels at its slowest speed.
Click the image to see the full video of Venus "setting" behind the limb of the Moon during the July 18, 2007, occultation. Michael Vlasov
To summarize, there are three ways to partake of this eye-catching celestial event: See Venus and the Moon in the company of the comet at daybreak; use the Moon to make a daytime sighting of Venus; or be present at just the right time to witness the occultation.
I know what I want to take — half a day off from work so I can see all three! Clear skies to all on Monday.
In the short video above, Venus "rising" from behind the limb of the Moon during the July 18, 2007, occultation.
Scientists See a Full Day on Pluto and Charon (November 19, 2015) by Nancy Atkinson
On approach in July 2015, the cameras on NASA’s New Horizons spacecraft captured Pluto rotating over the course of a full “Pluto day.” The best available images of each side of Pluto taken during approach have been combined to create this view of a full rotation. Credit: NASA/JHUAPL/SwRI.
A day on Pluto is 6.4 Earth days (6 days 9 hours and 36 minutes) long. That’s a lengthy, cold, and rather dark day. But this new image released by the New Horizons spacecraft team gives us a better idea of what a day on Pluto might be like. This montage of images shows Pluto rotating over the course of a full Pluto day.
It is interesting to note that Pluto’s moon Charon is tidally locked around Pluto, so this means that Charon takes 6.4 Earth days to orbit around Pluto – the same amount of time as a day on Pluto. If you were standing on Pluto, Charon would always be at the same place in the sky, or you wouldn’t be able to see it at all. And vise versa if you were on Charon.
New Horizons also captured a full day rotation for Charon, too, which you can see below.
On approach to the Pluto system in July 2015, the cameras on NASA’s New Horizons spacecraft captured images of the largest of Pluto’s five moons, Charon, rotating over the course of a full day. The best currently available images of each side of Charon taken during approach have been combined to create this view of a full rotation of the moon. Credit: NASA/JHUAPL/SwRI.
The images were taken by the Long Range Reconnaissance Imager (LORRI) and the Ralph/Multispectral Visible Imaging Camera as New Horizons zoomed toward the Pluto system, and in the various images the distance between New Horizons and Pluto decreased from 5 million miles (8 million kilometers) on July 7 to 400,000 miles (about 645,000 kilometers) on July 13, 2015.
The science team explained that in the Pluto montage, the more distant images are at the 12 to 3 o’clock position, and so these are the best views we have of the peculiar “bumps” or impact craters on the far side. The side New Horizons saw in most detail – what the mission team calls the “encounter hemisphere” – is at the 6 o’clock position. The most prevalent feature there is the heart-shaped, “Tombaugh Regio” area that made us all love Pluto even more.
The odd shape of Pluto in the 12 and 1 o’clock position images aren’t lumps and deformities, but just artifacts from the way the images were combined to create these composites.
For the Charon montage, the images at the 9 o’clock position were taken from the greatest distance, with few of the signature surface features visible, such as the cratered uplands, canyons, or rolling plains of the region informally named Vulcan Planum. The side New Horizons saw in most detail, during closest approach on July 14, 2015, is at the 12 o’clock position.
As a comparison, below is a timelapse view of the Pluto-Charon orbital dance, which was taken by New Horizons back in January 2015.
Pluto and Charon were observed for an entire rotation of each body, the same 6 days 9 hours and 36 minutes.
Pluto and Charon were observed by the New Horizons spacecraft for an entire rotation of each body; a “day” on Pluto and Charon is 6.4, which is Earth days. The first of the images was taken when New Horizons was about 3 billion miles from Earth, but just 126 million miles (203 million kilometers) from Pluto, on Jan. 25-31, 2015. NASA/APL/Southwest Research Institute.
Numerous Fireballs Reported as Taurid Meteor Stream Impacts Earth's Atmosphere
(November 5, 2015) by Tony Philips
There no longer any doubt. Earth is passing through a stream of gravelly debris from Comet Encke, source of the annual Taurid meteor shower. Meteoroids the size of pebbles, and larger, are disintegrating as they hit our planet's atmosphere at 30 km/s. To see what effect this is having on the night sky, Martin Popek of Nýdek (Czech republic) activated a low-light camera in his backyard and let it run all night long. This is what it recorded:
There were almost a dozen exploding meteors--all brighter than Venus and one as bright as a crescent Moon. "It was a very active night," says Popek.
Earth runs unto the debris zone of Comet Encke every year around this time. Usually, the encounter produces a minor meteor shower, but 2015 is different.
"This is higher than usual activity," says meteor expert Peter Brown of the University of Western Ontario. "The Canadian Meteor Orbit Radar (CMOR
) is seeing stronger Taurid activity than any of the last few years. Our Southern Ontario Meteor Network cameras caught 54 Taurid fireballs from Oct 31 - Nov 4 alone, compared to 22, 18, and 32 Taurids for the entire month
of November in 2014, 2013 and 2012 respectively."
These extra fireballs are coming from a "swarm" of gravelly meteoroids that weaves in and out of Comet Encke's dusty debris zone. In some years, Earth hits the swarm; in other years it misses. 2015 appears to be a hit.
"I would say with some confidence the 2015 Taurid 'swarm' is active as predicted by astronomer David Asher," adds Brown. If those predictions continue to be correct, the fireball display could carry on until Nov. 10th. The best time to look, no matter where you live, is during the hours around local midnight when the constellation Taurus is high in the sky. [meteor radar
On This Date, 150 Years Ago: Solar Mega Storm! (September 2, 2015) by Dr. Tony Philips
On Sept. 2nd, a billion-ton coronal mass ejection (CME) slammed into Earth's magnetic field. Campers in the Rocky Mountains woke up in the middle of the night, thinking that the glow they saw was sunrise. No, it was the Northern Lights. People in Cuba read their morning paper by the red illumination of aurora borealis. Earth was peppered by particles so energetic, they altered the chemistry of polar ice.
Hard to believe? It really happened--exactly 156 years ago. This map shows where auroras were sighted in the early hours of Sept. 2, 1859:
As the day unfolded, the gathering storm electrified telegraph lines, shocking technicians and setting their telegraph papers on fire. The "Victorian Internet" was knocked offline. Magnetometers around the world recorded strong disturbances in the planetary magnetic field for more than a week.
The cause of all this was an extraordinary solar flare witnessed the day before by British astronomer Richard Carrington. His sighting marked the discovery of solar flares and foreshadowed a new field of study: space weather. According to the National Academy of Sciences, if a similar storm occurred today, it would cause a trillion dollars in damage to society's high-tech infrastructure and require four to ten years for complete recovery.
In fact, a similar flare did occur just a few years ago. On July 23, 2012, a CME of rare power rocketed away from the sun. The storm was in all respects at least as strong as the 1859 Carrington event. The only difference is, it missed
. no harm done. The July 2012 event serves as a reminder, however, that extreme space weather is not a thing of the past.
THE SUN SWALLOWS A COMET:
On Friday, Aug.28th, the sun swallowed a comet. The Solar and Heliospheric Observatory (SOHO) spotted the icy vistor from the outer solar system making a headlong plunge into our star. One comet went in; none came out. Click to play the movie:
Heated by the sun at point blank range, the comet's fragile ices vaporized, leaving at most a "rubble pile" of rock and gravel scattered along its sungrazing orbit. Any remains are invisible from Earth.
The comet, R.I.P., was probably a member of the Kreutz family. Kreutz sungrazers are fragments from the breakup of a single giant comet many centuries ago. They get their name from 19th century German astronomer Heinrich Kreutz, who studied them in detail. Several Kreutz fragments pass by the sun and disintegrate every day. Most, measuring less than a few meters across, are too small to see, but occasionally a bigger fragment like this one (~10 m to 50 m) attracts attention.
Because of their common parentage, sungrazers often come in clusters. For this reason, it wouldn't be surprising to find yet another one in the offing. Monitor Karl Battam's Sungrazing Comet twitter feed for more sightings.
New Horizons Sees the Whole Pluto Family for the First Time (May 13, 2015) By Bob King
For the first time, NASA’s New Horizons spacecraft has photographed Pluto’s tiniest and faintest known moons, Kerberos and Styx. Kerberos circles the dwarf planet every 32 days and measures just 6 to 20 miles (~10 to 30 km) in diameter. Styx is even smaller at 4 to 13 miles (~ 7 to 21 km) across and orbits every 20 days. Incredibly, the specks of moons were detected from a distance of more than 55 million miles.
When you toss in Pluto’s largest moon, Charon, first seen by New Horizons in July 2013 and its two other smaller satellites, Nix and Hydra, spotted in July 2014 and January 2015 respectively, we’ve now seen all known members of Pluto’s family.
Anything else that pops up in images from now on will be gravy. That could well include new moons, Pluto rings or satellites of known moons.
“New Horizons is now on the threshold of discovery,” said mission science team member John Spencer, of the Southwest Research Institute in Boulder, Colorado. “If the spacecraft observes any additional moons as we get closer to Pluto, they will be worlds that no one has ever seen before.”
It won’t be long before the probe makes a dramatic flyby of the system on July 14. New Horizons will pass just 6,200 miles (10,000 km) from Pluto while traveling at 30,800 mph (49,600 km/hr) at closest approach at 6:50 a.m. Eastern Time. Because of Pluto’s great distance from the Sun, communications between the probe and Earth will take 4.5 hours, and that’s just one way moving at the speed of light.
Watch Venus Encounter the Pleiades This Week (April 7, 2015)
By Bob King, Astrobob@areavoices.com
Venus glides up to the Pleiades or Seven Sisters star cluster this week. This was the view at dusk on April 4 when they were still about 10° apart. Credit: Bob King
If you’ve ever been impressed by the brilliance of Venus or the pulchritude of the Pleiades, you won’t want to miss what’s happening in the western sky this week. Venus has been inching closer and closer to the star cluster for months. Come Friday and Saturday the two will be only 2.5° apart. What a fantastic sight they’ll make together — the sky’s brightest planet and arguably the most beautiful star cluster side by side at dusk.
No fancy equipment is required for a great view of their close conjunction. The naked eye will do, though I recommend binoculars; a pair of 7 x 35s or 10 x 50s will increase the number of stars you’ll see more than tenfold.
Map showing Venus’ path daily from April 6-15, 2015 as it makes a pass at the Pleiades. The close pairing will make for great photo opportunities . Created with Chris Marriott’s SkyMap
Just step outside between about 8:30 and 10 p.m. local time, face west and let Venus be your guide. At magnitude -4.1, it’s rivaled in brightness only by the Moon and Sun. Early this week, Venus will lie about 5° or three fingers held together at arm’s length below the Pleiades. But each day it snuggles up a little closer until closest approach on Friday. Around that time, you’ll be able to view both in the same binocular field. Outrageously bright Venus makes for a stunning contrast against the delicate pinpoint beauty of the star cluster.
Venus on April 3, 2012, when it last passed right in front of the Seven Sisters. The Pleiades is a young cluster dominated by hot, blue-white stars located 444 light years from Earth. Credit: Bob King
Every 8 years on mid-April evenings, Venus skirts the Pleiades just as it’s doing this week. Think back to April 2007 and you might remember a similar passage; a repeat will happen in April 2023. Venus’ cyclical visits to the Seven Sisters occur because the planet’s motion relative to the Sun repeats every 8 years as seen from Earth’s skies. No matter where and when you see Venus – morning or evening, high or low – you’ll see it in nearly the same place 8 years from that date.
But this is where it gets interesting. On closer inspection, we soon learn that not every Venus-Pleiades passage is an exact copy. There are actually 3 varieties:
* Close: Venus passes squarely in front of the cluster
* Mid-distance: Venus passes ~2.5° from the cluster
* Far: Venus passes ~3.5° from the cluster
And get this — each has its own 8-year cycle. This week’s event is part of a series of mid-distance passages that recurs every 8 years. Venus last passeddirectly through Pleiades in April 2012 and will again in April 2020. The next most distant meeting (3.5°) happens in April 2018 and will again in 2026.
Venus circles between Earth and the Sun and experiences phases just like the Moon from our perspective. The planet is currently in gibbous phase. It reaches its greatest apparent distance from the Sun on June 6 and inferior conjunction on August 15. Credit: Wikipedia with additions by the author
Why three flavors? Venus’ orbit is tipped 3.4° to the plane of the ecliptic or the Sun-Earth line. During each of it 8-year close passages, it’s furthest north of the ecliptic and crosses within the Pleiades, which by good fortune lie about 4° north of the ecliptic. During the other two cycles, Venus lies closer to the ecliptic and misses the cluster by a few degrees.
Fascinating that a few simple orbital quirks allow for an ever-changing variety of paths for Venus to take around (and through!) one of our favorite star clusters.
Click on the links below to find information, finder charts, and observing tips on all the lastest comets visible from your backyard and beyond.