Heads up: NASA says 4,700 potentially hazardous asteroids are out there

The little asteroid 2012 KA passes near Earth today before heading back out into space. Credit: JPL

This afternoon around 3 o’clock Central time, asteroid 2012 KA will fly silently past Earth at a distance of about 139,433 miles. That’s a little more than halfway to the moon and well out of harm’s way. 2012 KA was discovered only yesterday by the Mt. Lemmon Observatory as part of the larger Catalina Sky Survey. The survey’s goal is to find and determine orbits of larger, potentially hazardous near-Earth asteroids (PHAs) from 100 meters (330 feet) on up. PHAs are a subset of a larger group of near-Earth asteroids or NEAs.

This fly speck of an asteroid is only 25 feet across. Even if it were to hit the Earth – which it isn’t – most of it would burn up on entry. Any fragments left over would be insignificant in terms of causing damage on the ground.

Tiny asteroids like this one are discovered routinely, sometimes only days before closest approach. There are a couple reasons for that. Being small, they’re very faint. To spot one, the asteroid has to get close enough to be detectable. That doesn’t allow much lead time between discovery and flyby. They also may approach Earth from the direction of the sun and be lost in the glare of daytime. Only when an asteroid appears at night are astronomers able to find, photograph and determine an orbit. At that point, only days or hours may remain before the rock buzzes the planet.

This diagram shows an edge-on view of our solar system. The dots represent the NEAs and PHAs that scientists think are likely to exist based on the survey. Positions of a simulated population of PHAs are shown in bright orange, and the simulated NEAs are blue. Earth's orbit is green. Notice how the PHAs tend to be more closely aligned with the plane of Earth's orbit, or less tilted above and below the plane, than the NEAs. Credit: NASA/JPL-Caltech

The results of a new study based on data gathered by NASA’s Wide-field Infrared Survey Explorer (WISE) have led to a better assessment of potentially hazardous asteroids (PHAs). These are the ones measuring 330 feet across or larger that pass within 5 million miles of Earth and have the potential to cause significant destruction in the event of a collision.

Asteroids are warmed by the sun and radiate heat. WISE studied the sky in the light of infrared or heat waves and was able to see both light and dark asteroids (ones that might be missed by regular telescopes), resulting in a more representative look at the entire population.  Based on studies of 107 PHAs with WISE, astronomers estimate there are roughly 4,700 PHAs, plus or minus 1,500, with diameters larger than 330 feet. To date, an estimated 20 to 30 percent of these objects have been found. Obviously, many remain to be discovered and orbits determined. Considering that we’ve only recently begun faint asteroid surveys with large telescopes, we’ve come a long way.

This diagram shows the difference between the orbits of typical NEAs and PHAs. PHAs orbit closer to Earth and in nearly the same plane as our planet, making them potentially hazardous. The asteroid orbits are simulations of what a typical object's path around the sun might look like. Credit: NASA/JPL-Caltech

“The new analysis also suggests that about twice as many PHAs as previously thought are likely to reside in “lower-inclination” orbits, which are more aligned with the plane of Earth’s orbit. These lower-inclination objects appear to be somewhat brighter and smaller than the other near-Earth asteroids that spend more time far away from Earth,” according to the study.

Because of their similar size and brightness, it’s suggested that a collision between two asteroids with low-inclination orbits in the main asteroid belt liberated fragments that drifted into Earth’s vicinity to become PHAs.

The diagrams, which are simulations based on real data, look very crowded. That’s only because they squeeze an enormous volume of space into a box six inches wide. It’s important to keep in mind there’s a great deal of space between those dots!

Comet Garradd has its last hurrah in the constellation Cancer in the western sky at the end of twilight. For the next week it will be near Iota Cancri, one of the prettiest double stars of spring. Stars show to 8.5 magnitude. Inset photo: Rolando Ligustri. Map created with Chris Marriott's SkyMap

While we’re on the topic of small solar system bodies, Comet Garradd, the comet that’s been visible in small telescopes and binoculars for more than a year, will soon disappear in twilight and fade away as it travels into the deep southern sky. It’s still 9th magnitude and viewable in 4-inch and larger scopes. Larger instruments will show its faint dust tail pointing east. Garradd will slowly trek through the constellation Cancer the Crab through June. Get a last look while you can. It’s still the brightest comet in the sky.

Chance for auroras, North Korea’s shining star and Comet Garradd

The green glow of geomagnetic goodness painted the bottom of the northern sky early this morning. Minor auroras are forecast for tonight for northern regions. Photo: Bob King

The aurora crept up in the north very, very late last night. Just a green glow, not too much. I noticed the light around 11:30 p.m. and watched it slowly intensify into a bright arc speared by occasional faint rays just before 1 a.m. A half hour later, a promising display that almost sent me to the computer to post an alert, collapsed into a faint arc at the bottom of the northern sky. Who let the air of the tires?

The northern lights have much in common with the trickster character of many American Indian myths. He’s the prankster and rule breaker. When we think life is predictable, the trickster keeps us on our toes.

Thanks to a big hole in the sun’s corona (outer atmosphere) a stream of high speed particles is buffeting Earth’s protective magnetic bubble, giving us a chance of auroras. No big storms are expected, but you might want to scan the northern sky around midnight the next couple nights. In the photo above, both the green glow, which was visible with the naked eye, and the much fainter pink, were caused by excitation of oxygen atoms high in Earth’s atmosphere.

A North Korean soldier keeps an eye on things at Sohae Satellite Launch Station. The Unha-3 rocket (background) will carry the Bright Shining Star satellite into space. Credit: AP

Satellite watchers are sitting on pins and needles waiting for the imminent launch of North Korea’s  Kwangmyongsong-3 satellite. Billed as an Earth-observation spacecraft, it would be used to gather weather data and photograph the country’s forest and farmland during its two-year lifetime in orbit. You’re probably more familiar with the backstory that the launch is really about testing ballistic missiles.

The satellite’s name means “Bright Shining Star” and it’s the third in a series that began with Kwangmyongsong-1 in 1998. Although North Korea says the first two launches were successful, no independent observer ever saw them in orbit.

Kwangmyongsong-3 will mark the 100th anniversary of founding of the Democratic People’s Republic of Korea by its founder Kim Il Sung. Once in orbit, the satellite will broadcast two patriotic tunes -  ”The Song of General Kim Il Sung” and “The Song of General Kim Jong Il.” If the launch succeeds, I’ll post times when it might be visible from your town. UPDATE 7 p.m. CDT: The satellite was launched at 7:39 a.m. Korean time but failed to reach orbit. Story HERE.

Comet Garradd passes through the toes (Theta, Kappa, Iota stars) of one of the Dipper's paws the next few nights. The comet's path is marked every five days. Stars shown to 6.5 magnitude. Created with Chris Marriott's SkyMap software

If you have a 6-inch or larger telescope, the next couple nights are ideal for finding the comet observers have been going steady with since last summer –  Comet Garradd. It’s passing through ones of the “paws” of the Great Bear a.k.a the Ursa Major a.k.a. the Big Dipper. It’s faded to 7.5-8 magnitude but I still spotted it last night from a dark sky in 10 x 40 binoculars as a faint, fuzzy glow. The map above is drawn for 9:30 p.m. local time as you face north. Through the telescope, the comet is a fuzzy ball with a brighter center or nucleus. A faint dust tail 1/2 degree long pointing northeast is visible in 10-inch and larger scopes.

Northern lights limbo plus a comet takes on a dragon

Despite a no-show for the light show, many of you noticed the striking pair of Venus and Jupiter in the western sky during twilight last night. Photo: Bob King

You’re not all going to turn your backs on the aurora just yet, are you? Some of us were disappointed that the expected storm didn’t arrive. Even today, there’s no evidence of its arrival. Either it missed us, delivered a much softer blow than anticipated or is still on its way.

Aurora forecasting resembles ordinary weather forecasting in many ways. Forecasters gather the latest information and then use computer modeling to determine a a storm’s track, arrival time and how severe it will be. We’re all familiar with the possible outcomes: meteorologists either nail it, get the idea right but err on the particulars or prove utterly wrong. We must learn to forgive, since nature always has the trump card. To learn more about the sun’s affects on Earth, including the aurora, I think you’ll enjoy this brief primer on space weather.

Auroral storms are still expected today through tomorrow, so it always pays to keep watch. I’ll post an update later today.

Earth's counterclockwise motion around the sun causes the stars and planets to rise 4 minutes earlier in the east each night. Over time, those minutes add up, until current season's constellations are "pushed" off the stage by the next. The cycle comes full circle after a year. Illustration: Bob King

The planets have been a big part of the night sky landscape the past few weeks. Venus and Jupiter dominate the western sky, ruddy Mars is high up in the southeast by mid-evening and Saturn shows up next to Spica in Virgo around 11 o’clock. That used to be 10 o’clock, but no thanks to daylight-saving time, we have to stay up an hour later now to see Saturn.

Not to fret. Earth’s revolution around the sun will conspire to raise the planet in the east 4 minutes earlier each night. In just two weeks that will shave a total of 56 minutes or nearly an hour off its rising time, and we’ll be back to where we started.

Rolando Ligustri compiled four days of photos of Comet Garradd from March 3-6 to show its motion through the sky. The dust tail sticks out to the left; the ion or plasma tail to the right. Credit: Rolando Ligustri

Last night I was excited to see how Comet Garradd’s been doing, so I grabbed my 10×50 binoculars and found it just beyond the Bowl of the Big Dipper in the tail of Draco the Dragon. Since we did our last update, the comet has moved from the morning sky to a very convenient viewing spot right up next to the Dipper. This slow-moving, rather distant but large comet has been hanging around since last summer. All the while, it’s brightness has changed little, remaining around magnitude 6.5. That’s just below the naked eye limit. Garradd was closest to Earth on March 5 at 118 million miles.

In case some of you are wondering why I’m always talking about this comet, it’s the only one in recent months bright enough to enjoy in a small telescope or see in binoculars. The rest are faint.

Last night through binoculars it was a dim, misty patch about 2/3 the size of the moon with a brighter center. Through a 15-inch telescope, Garradd has a bright, fuzzy coma with a small, intense star-like core or nucleus. Two faint, diffuse tails sprout from its head. To see these, you’ll need at least a 6 to 8-inch telescope and dark skies. Garradd will slowly fade through March and April but remain well-placed for viewing. Give it a try now that the moon’s out of the sky.

The Big Dipper, now high in the northeastern sky in the early evening hours, makes it fairly easy to find Comet Garradd. This map shows its position every 3 days through late March. Look for a faint, fuzzy patch in binoculars. The labeled stars, Kappa and Lambda Draconis, are naked eye stars. Other stars shown to about mag. 7. Created with Chris Marriott's SkyMap

One weird-looking comet plus a constellation that can spell

The two-tailed comet photographed through a telescope on February 12. While two tails aren't unusual in a comet, seeing them exactly opposite one another isn't common. Credit: Michael Jaeger

Comet Garradd is one weird-looking comet. At the moment, because we see it high above the plane of our planet’s orbit, the two tails stick straight out of either side of its head. It’s not often you get to see a comet’s tails 180 degrees apart, but Garradd has been visible for so many months now, it’s like an entertainer remaking his image in hopes of rekindling that old fire.

The bluish gas tail points to the right; the dust tail to the left. According to the photographer, Michael Jaeger, the gas tail has been fading recently. You can see the comet as a fuzzy spot in a pair of binoculars under reasonably dark skies. The fainter tails require an 8-inch or larger telescope to see well.

Comet Garradd now never sets for the northern U.S. The map shows its location every five days low in the northern sky during early evening hours. Stars shown to 6th magnitude. Created with Chris Marriott's SkyMap

Recently Comet Garradd became circumpolar for the northern half of the U.S., Canada and much of Europe. A star or comet that’s circumpolar is always visible above the horizon, forever circling around the pole star Polaris. The good news is that you don’t have to get up before dawn to see it; the bad news is that it’s still rather low in the north – at least during the early evening hours.

Sigma-shaped Cassiopeia is up in the northwestern sky on the opposite side of the North Star from the Big Dipper during late February evenings. Created with Stellarium

You can use the map at any time of night however simply by saving it, printing it and then turning it counterclockwise, so the constellations match your sky view.  The comet will continue to climb higher in the north as it arcs its way through Draco the Dragon and passes between the two Dipper Bowls early next month.

The ancient and modern Greek letter sigma

While you’re out facing north, take a look off to the northwest (to the left of the Little Dipper) at the zigzag of Cassiopeia, now standing on its end. When it first rose in the northeastern sky late last summer, it looked like the letter W. Come December, when it was pitched high overhead, the W was inverted and became the letter M. Now it’s sitting up sideways and resembles the upper case Greek letter sigma.

No matter the season, Queen Cassiopeia always gets our attention not only because of her bright form but also her rudimentary attempts at spelling.

Comet Garradd pays a visit to a Herculean star cluster

Comet Garradd photographed this morning (Feb. 2) near the globular cluster M92 in Hercules. The dust tail points to the left (east) of the comet's bright center called the coma. The gas tail points to the upper right. Credit: Michael Jaeger

Binocular and telescope owners can watch a fine match-up of the sky’s current brightest comet – Comet C/2009 P1 Garradd – and the rich cluster M92 in Hercules tomorrow morning. The cluster belongs to an ancient group of spherical, star-packed clusters called globulars. Some 330,000 stars are jammed into a ball 109 light years in diameter 26,000 light years away. Despite that rather spectacular distance, it still shines brightly enough at magnitude 6.4 to be easily visible in a typical pair of binoculars from moderately light polluted skies. Look for a small fuzzy spot with a brighter center.

Comet Garradd will be another fuzzy patch only a half a degree to the right or west of M92, so both little glows will be close together in the same field of view in any pair of binoculars. As you’d expect, the comet is much closer to Earth at 142.8 million miles. The separation between them will increase in the coming mornings as Garradd tracks slowly northward through Hercules.

Garradd's two tails point away from each from a combination of the comet's location high above the plane of the planets and our perspective of it from Earth. Blue arrows show the direction the comet's moving along its orbit. Credit: NASA/JPL with my own additions

In the diagram above, you can see that the comet has a steeply inclined orbit that takes it well above the plane of the solar system where the planets orbit. That’s why we see it high in the northern sky this month far from the morning planets. Comets that pass relatively close to the sun typically develop two tails – one made of dust carried away by the pressure of sunlight along the comet’s orbit and an ion tail of gases that fluoresce when they’re excited by the ultraviolet energy in sunlight. The dust is released into space as the heat of the sun vaporizes cometary ices.

This map shows Comet Garradd in the coming 10 days as it glides through the constellation Hercules. Stars are shown to 8th magnitude. Click the image for another map showing how to easily find Hercules. Created with Chris Marriott's SkyMap software

Since ion tails always point directly away from the sun, while dust tails lag behind in the curve of a comet’s orbit, the two tails point in different directions. Depending upon the sun-Earth-comet viewing geometry, they sometimes overlap or appear separated from one another by varying degrees. Our current viewing angle – looking up from way down below Garradd’s orbit – accentuates the tails’ separation.

The best time to see Comet Garradd and M92 is about 1 1/2 – 2 hours before sunrise, when it’s highest in the eastern sky before morning twilight begins. A small telescope will show the bright coma and a hint of both tails; telescopes of 8 inches or larger will show both tails stretching faintly more than a degree from comet’s head. Seeing a pile of stardust right next to bright, nearby comet should make for a beautiful sight. Try to get out in the next few mornings before moonlight becomes a problem.

Things to see while waiting for the storm to hit

A very thin moon only a day and a half past new appears in the southwestern sky shortly after sunset this evening. Created with Stellarium

* UPDATE 10:30 p.m. CST: The Kp index, which measures magnetic activity and the potential for auroras, reached storm levels of 5 this afternoon but has since dropped to an “active” but non-storm level of 3 for the past six hours. Earlier, auroras flickered over Scotland, northern Ireland, Scandinavia and the Arctic regions. For now, they appear to have moved further north into Canada. I’ve heard of no sightings YET from the northern U.S. Let us know what you see. Thanks!

While we’re waiting for the hoped-for light storm, let’s look ahead to things we can see and predict with certainty. Tonight for instance, you can stand outside and face southwest a half hour after sunset to see a temptingly delicate crescent moon in the west below Venus. It’ll be so thin that in bright twilight, it’s barely there. By tomorrow night the 25th, watch for the moon to thicken a bit and brighten further as it scooches up next to Venus.

Comet Garradd shows a pale green coma and two tails in this photo taken on January 16. Ion tail to the upper right (n.west) and dust tail (east). Credit: Erik Bryssinck

Remember Comet Garradd from last summer and fall? With the staying power of a marathon runner, it’s returned to the morning sky still clicking through the stars of Hercules the Strongman. No moon will spoil the darkness for the next 10 nights, so you may want to go out for a look.

Garradd will be easy to pinpoint thanks to some handy guide stars, and at magnitude 6.5-7 it’s bright enough to see in binoculars. A few mornings ago the comet was a small ball of glowing fuzz in 8×40 binoculars, while a look through my 15-inch scope made my eyeballs smile. At low power, the pale green coma with two soft, diffuse tails sticking out either end was a beautiful sight. I figured it was time to share.

Find Vega and then use the star Gamma in Draco and draw an imaginary equilateral triangle that includes Comet Garradd. The map shows the sky facing east around 5 a.m. local time.

The best time to observe Comet Garradd is when Hercules is highest in the east before the start of dawn or around 5-5:30 a.m. You can start by finding the bright star Vega of Summer Triangle fame in the east-northeast. From there, navigate up to the trapezoidal pattern of stars nicknamed the “Keystone” of Hercules. One side of the Keystone features the sumptuous globular cluster M13. The comet lies along the other side and moves slowly northward in the coming weeks. Let us know if you have success in seeing it.

Use this detailed chart to pick your way to the comet with binoculars and telescope. Star shown to 7th magnitude. Positions are at 5 a.m. Central time every five days. Created with Chris Mariott's SkyMap software

Comet Garradd still going strong; Russian Mars probe contacted!

Comet Garradd on November 19 shows a classic dual tail. The longer, blue streak is the ion tail. The dust tail is shorter and glows pale yellow from reflected sunlight. Credit: Michael Jaeger

Remember Comet Elenin? Hopes were high it would become the best comet of 2011, but instead it dissolved into a cloud of dust. Amateur astronomers are still tracking its fading remnants as the comet passes the Pleiades star cluster in Taurus this week.

Use this finder chart to track down Comet Garradd. It inches slowly northward only a few degrees in the coming month. The map shows Hercules at around 6 p.m. at the end of evening twilight in the western sky. M13 is a bright globular cluster and stars are shown to 7th magnitude. Created with Chris Marriott's SkyMap software.

The brightest comet of the year never received the dire publicity that stuck with Elenin to the end. Comet Garradd was well-placed and easily visible in binoculars this summer as it crossed the Milky Way en route to its current residence in the sprawling constellation Hercules. Underdog Garradd remains a 7th magnitude fuzzball in binoculars this month. I looked it up recently on one of the few clear nights we’ve had in November and was thrilled to see two tails sticking out of the comet’s bright, fuzzy head or coma. Both show wonderfully in Michael Jaeger’s photo and were just as pretty in my 15-inch scope though much more subtle.

Comet Garradd is 195 million miles away or about twice our Earth’s distance from the sun. That gap will close to 118 million miles by early next March, when the comet will brighten by a magnitude, placing it within naked-eye range from the countryside. Take a look now before it drops too low in the western sky and the moon returns. The best viewing time is right at the end of evening twilight as soon as the sky gets dark.

Binoculars still show a soft, puffy glow and perhaps a hint of a tail. A modest-sized telescope will show the dust tail and maybe even a hint of the ion tail. Dust tails are formed of smoke-sized particles of dust embedded in cometary ice. Heat from the sun vaporizes the ice and releases the particles which fall behind the comet in the form of a tail measuring between 600,000 and 6 million miles long. Comet dust reflects light just like good old house dust or cigarette smoke. Ion tails fluoresce blue when ultraviolet light in sunlight breaks down carbon monoxide jetted by the comet and are often much longer – up to 100 million miles.

The European Space Agency's Perth, Australia radio telescope that contacted Russia's Phobos-Grunt craft yesterday. Credit: ESA

Just got the news this morning that contact was re-established with the Phobos-Grunt mission that’s been stuck circling the Earth since its November 8th launch. You might recall the probe’s engines failed to fire and send the ship to Mars. Yesterday at 2:25 p.m. CST, the European Space Agency’s (ESA) tracking station at Perth, Australia, picked up a radio signal from the probe. ESA is now working with engineers in Russia on how best to maintain communications with the spacecraft. Another contact will be attempted tonight.

There’s no information on what might have gone wrong with Phobos-Grunt or how it might be remedied. If engineers can establish a solid communications link with the craft and learn how to correct the engine-firing problem, it might still be sent on its Mars-Phobos mission, but probably not anytime soon. The next launch window opens in 2013. Full story HERE.

A well-narrated and illustrated summary of how we’ll study Gale Crater with the Curiosity Rover.
Meanwhile the Mars Science Lab Mission (Curiosity Rover), which was originally scheduled for a Nov. 25 launch, has been delayed one day to replace a battery on the rocket. Blastoff is scheduled for 9:02 a.m. Central time this Saturday. Click this Mars Exploration Family Portrait by Jason Davis for a really cool graphic showing all missions to Mars to date.

Tears for Comet Elenin, but there’s more to life

Seven sunspot groups dot the sun's face in this photo from 8:30 CDT this morning. Credit: NASA/SDO

Time to catch up on the news. The sun is positively peppered with sunspot groups but they’ve been mostly well-behaved with few flares to shows for so much spottiness. Just the same, there’s a good chance for minor auroras across the northern U.S. and Canada this evening from something else in the sun’s bag of tricks – a coronal hole.

Look low along the northern horizon for a greenish glow during the early evening hours . Views will be compromised after about 9 p.m. when the moon is up high enough to spill light across the sky.

Let’s not forget the supernova in the Pinwheel Galaxy in the Handle of the Big Dipper. At magnitude 11.7, it’s still within easy range of 6-inch and larger telescopes. Amazing to think that the supernova, discovered on August 24, is nearly two months “old” and continues to blaze so brightly. Catch it as early as you can at the end of evening twilight before it drops below the trees and roofs. Maps for finding it are here in this earlier blog.

Photo of Comet Elenin's position on October 9 taken through a 10-inch telescope. Stars (long streaks) as faint as 17th magnitude are visible while the red squares are positions of even fainter asteroids in the field of view. No comet cloud or fragments are visible. Click photo to read and see more Elenin attempts. Credit: Ernesto Guido, Giovanni Sostero and Nick Howes

There’s a discussion going on right now among comet observers about whether Comet Elenin is visible or not. Tomorrow, what’s left of the comet makes its closest approach to Earth at 22 million miles. This was the time we’d all been hoping to see it near naked eye brightness, but it crumbled in August and the remaining icy fragments have all but vaporized away in the sun’s heat.

Comet Garradd photographed last night from Italy by ace astrophotographer Rolando Ligustri. Two tails are visible - a blue ion tail at top and a yellowish dust tail below.

Two positive observations of Elenin were made about a week ago by trustworthy observers under excellent skies, but larger telescopes and long time exposures have shown nothing. Other experienced visual observers have also had no success. Granted, they were all battling low altitude and the glow of the zodiacal light. What the two observers would have seen was the faint, residual dust cloud left in the wake of the breakup. The next opportunity to see Comet Elenin will be in about a week, when it will be much better placed in a dark morning sky. Expect lots of amateur astronomers to be out with scopes and cameras for one last attempt. I’ll have more news then.

To find Comet Garradd with binoculars or telescope, face due west and find the two bright stars on the right side of the Summer Triangle - Altair and Vega. Use them to create another triangle with 2nd magnitude Alpha Ophiuchi directly below. Once there, use the map below to navigate the short distance from Alpha to the comet. Created with Stellarium

Despite Elenin’s poor showing, there’s no need to hang your head. Comet Garradd is still going strong at around magnitude 7.5 during the early evening high in the western sky near the border of the constellations Hercules and Ophiuchus (oh-fee-YOU-cuss). From a dark sky it looks like a small, fuzzy puff in binoculars. Telescopes will show a bright comet head or coma and faint tail pointing east. The moon is now rising late enough to provide the dark sky you’ll need for the best view.

Once you're at Alpha Oph, you can star hop up a chain of 5-6 magnitude stars to get to the comet. Nearby Alpha Herculis is also a helpful guide star. This map shows the sky as you face west. Comet positions are shown every five days. The dashed line is the constellation boundary. Created with Chris Marriott's SkyMap software

Don’t forget to look for the X-ray telescope ROSAT tonight we talked about yesterday. Now that its orbit is dropping lower, the doomed satellite has been reported as bright as 1st magnitude! Scroll down to Friday’s blog for links on how to find it.

This image of the asteroid Vesta, calculated from a shape model and based on photos, shows a low angle view of the south polar region. The mountain in the foreground is 13 miles high. Click to enlarge. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/PSI

And finally, I’ll leave you with a couple recent pictures taken by the Dawn spacecraft of a dark-rayed crater and one of the highest mountains in the solar system.These wonders of nature are found 168.5 million miles from your doorstep on the asteroid Vesta.

A fresh 1-mile diameter crater surrounded by dark rays of excavated rock from Vesta's crust. Rays are normally composed of bright material, so more study will be needed to answer why these are dark. Click to enlarge. Credit: NASA

Pinwheel Galaxy supernova at brightest; Comet Garradd beckons

Thomas Nelson of Duluth put together before-and-after photos of the Pinwheel Galaxy to show how what a difference the supernova makes. He took an image in May before the eruption and combined it with one taken this month by William Wiethoff.

I am jazzed up. I finally got a picture of the supernova SN 2011fe in the Pinwheel Galaxy last night using only a telephoto lens on a tracking mount. The moon is now nearly at last quarter and doesn’t flood the sky with light like it does around full phase. This provides us all with another round of opportunities to see the supernova before it fades. For almost a week, it’s been humming along at magnitude 9.9. As you can tell from the before-and-after sequence above, it’s hard to miss!

The path starts at bright Mizar and zigzags its way up to the supernova, which lies just beyond the arrow tip in the Pinwheel Galaxy in this photo taken last night (Sept. 16). Alkaid and Mizar are the two stars at the end of the Big Dipper's Handle. Details: 150mm lens, f/2.8, ISO 800 and 2-minute exposure. Photo: Bob King

Here’s a link to two maps to help you find the SN 2011fe or you can use the photo above. It will soon begin to fade, so take some time the next clear night and treat your eyes to a big blast. You can either use big binoculars (20 x 80mm or 30 x 80mm on up), a small telescope or even a spotting scope to see it.

The life cycle of a star on its way to becoming a Type Ia supernova. This variety of supernova evolves in close double star systems, where the companion is ejected into space after the powerful explosion. Credit: NASA/ESA

Type Ia supernovae like the Pinwheel star are produced when a white dwarf star gobbles matter from a close companion star. When critical mass is reached, the increase in pressure and density within the dwarf initiates the fusion of carbon atoms in the core which releases enough energy to completely and explosively burn through the star. Try to picture a thermonuclear bomb the size of a large city going off to grasp the power of this stellar .

A light curve for a typical Type Ia supernova showing how the star's brightness (left) axis varies with time. Credit: NASA/HST/High-z SN Search Team

The star suddenly rises from invisibility to maximum light in the space of a few weeks then takes several months or more to fade away. Type Ia explosions are bright enough to be visible across billions of light years. That and their similarity to one another allow astronomers to use them as “standard candles” to determine distances to galaxies billions of light years away.

Look for Comet Garradd to the west of the Summer Triangle asterism comprised of Vega, Deneb and Altair. The comet is near a small triangle of faint, naked eye stars in Hercules. The map shows the sky facing south-southwest at nightfall and the comet's position at 5-day intervals. Created with Chris Marriott's SkyMap

I also looked at our good friend Comet Garradd last night which continues shining around 7th magnitude high in the southwestern sky. I’ve prepared the map above you can use to find the comet between now and mid-October.

Because of viewing perspective involving the combined motions of Earth and the comet, Garradd will appear to slow down in the coming weeks, remaining in one small area of the sky near the trio of faint naked eye stars 109,110 and 111 Herculis in the constellation Hercules. It’s faintly visible in binoculars and a pretty sight with a fat tail pointing southeast in a telescope.

Find the Pinwheel Galaxy supernova – part II; the moon meets Dschubba tonight

Beautiful, subtle colors show in this weak aurora visible around midnight last night low in the northern sky. The constellation Auriga and bright star Capella are at right. There is a small chance for more auroras tonight. Photo: Bob King

I hope you had clear skies and were able to see the Coathanger last night along with Comet Garradd. Through a telescope, so many bright stars were near the comet, it looked like fireworks. Garradd will be just west of the asterism tonight and continue to make a fine pairing through binoculars and telescopes.

It was our first clear night after several cloudy ones, and I was eager to check out supernova SN 2011fe in the Pinwheel Galaxy in the Big Dipper. Holy heck – I found it glowing at magnitude 10.2! That means with a a suitable map, it’s bright enough to be seen in any telescope. Even 80mm binoculars will show the star to an experienced eye under dark skies. By the way, it’s now tied with SN 1993J in the galaxy M81 as the 6th brightest supernova ever seen beyond the Milky Way system. And it keeps on rising.

Even you lowest magnification will show the supernova in M101, the Pinwheel Galaxy. Directions, shown at top, are for a typical reflecting telescope. Field of view is about 1/2 degree. Illustration: Bob King

In this new map (right), I’ve expanded the view and made other improvements to help you locate it. Go back to the wide-view map, which you’ll find below,  and “star-hop” to the Pinwheel Galaxy in your telescope. Then use this more detailed sketch to identify the supernova. Two bright stars of 8th and 9th magnitude west of the galaxy form a bright triangle with the supernova. The little star just below the galaxy’s brighter nucleus is dimmer at magnitude 12 1/2.  If you own a scope, go out and look for the exploding star in the next few nights before the moon gets too bright.

Last night it was absolutely unmistakable inside the galaxy – a beacon of radiance compared to the soft, dim galactic fuzz. Although SN 2011fe was easy to spot at my lowest magnification, I cranked up the power to 145x to better visualize how mind-boggling brilliant the event must have appeared to any lifeforms in the galaxy around to see it 25 million years ago. It may only look like a star, but knowing you’re beholding the ultimate cosmic cataclysm kicks it up a notch.

The view tonight looking southwest an hour or two after sunset. Use binoculars to see the moon and Delta snugged up close. Created with Stellarium

After you’ve gotten your supernova and Coathanger-comet buzz, take a look at the moon low in the southwestern sky tonight. It’ll be right in the middle of the head of Scorpius extremely close to the center star in the head called Delta or Dschubba (JOOB-a), its Arabic name.

Delta is 400 light years away and a fascinating variable star 14,000 times brighter and five times larger than the sun. Starting in 2000, the star began to brighten and by 2003 topped out at magnitude 1.6 becoming the second brightest star in the constellation after Antares. It’s still showing activity this year. You can learn more about the Dschubba HERE.

Binoculars and small telescopes will give a cool view of the two together in conjunction. I wonder if you’ll be able to still see Delta without optical aid? Check it out and let us know.

Find Mizar in the bend of the Dipper's Handle and then follow the little road of stars up to the Pinwheel Galaxy. The map shows the Handle as you face northwest at nightfall. I've marked the same 8 and 9 magnitude stars in both maps. Remember that the drawing, made using a typical reflecting telescope, inverts the view with south up and west to the left. Created with Stellarium