STEREO probe snaps portrait of Earth and Comet PANSTARRS

Comet PANSTARRS joins Mercury and our own planet in this photo taken by STEREO-B on March 10, 2013. Click for large version. Credit: NASA / courtesy Karl Battams

Wow, now isn’t that the coolest! The STEREO-B spacecraft took this photo of Comet C/2011 L4 PANSTARRS and two planets to boot on March 10. NASA’s dual STEREO sun-watching observatories are positioned in Earth’s orbit, one ahead of the planet and one behind. From these two locations they’re able to monitor both the front and backsides of the sun, something otherwise impossible to do from the ground. Their eyes also see background stars down to 13th magnitude, planets and the occasional comet like PANSTARRS.

Animation of photos taken by STEREO-B over an approximately 20 hour period on March 10, 2013. The vertical line below the comet’s head is an artifact. Credit: NASA

Look closely at the comet. Uncompromised by Earth’s atmosphere, we can see four tails.One of the two short spikes is electrified carbon monoxide gas carried away by the solar wind. The other might be made of iron atoms from the iron-sulfur mineral troilite (common in meteorites) blown back by sunlight itself. Two additional tails glow by sunlight reflecting off dust particles released from the comet’s ices as they’re vaporized by the heat of the sun.

Click HERE for maps to help you find Comet PANSTARRS –  from Earth – tonight.

Tough time finding Comet PANSTARRS? Crescent moon to the rescue!

Comet C/2011 L4 PANSTARRS over the lights of San Diego, Calif. on March 10, 2013. Kevin caught the comet in an open spot between bands of haze. Credit: Kevin Baird

Comet PANSTARRS is proving harder to see with the naked eye than expected. Many sky watchers have either been thwarted by clouds or frustrated by haze. Even hard-core comet followers have had difficulty, so you’re not alone. While most experienced observers estimate its brightness at about 1st magnitude – equal to that of the brighter stars – haze, clouds and bright twilight have made finding it with the naked eye tricky to impossible to see.

The 1-day-old moon lines up with PANSTARRS in the western sky tonight March 12.. This map shows the sky from mid-northern latitudes about 25 minutes past sunset when the comet and moon will both be 8 degrees high slightly south of due west. Maps created with Stellarium. See end of blog to learn how to get this free program and make your own comet map.

OK, now for the good news. We’re all going to get some help tonight and tomorrow night from the crescent moon. Like a celestial fishing guide, the moon will take you to the right spot where all you need do is drop your line in the water and wait for a bite. We’re hoping your patience nets you a comet this time around.

Tomorrow night March 13 the moon will be higher and easier to see and still be useful to locating the comet. This map shows the sky about 25 minutes after sunset looking west. The moon will be 20 degrees high, the comet 10 degrees.

Tonight (March 12) look about 4 degrees to the left of the moon with binoculars beginning about 25 minutes after sunset. Assuming the sky is clear, you should see a fuzzy pinkish star. Trouble focusing? Just point the binoculars at the moon and focus sharply. You can also use clouds for focusing. Either way, once they’re sharp, the comet will be too.

As the sky darkens, the “star” will sprout a short tail. That’s it – Comet PANSTARRS. The color by the way is not intrinsic to the comet but caused looking through so much thick atmosphere. It’s the same reason the sun and moon glow red when near the horizon; blues and greens are scattered by dense and dusty air, leaving only oranges and reds. The comet-moon combo should be visible for about a half hour until setting.

Tomorrow March 13 the moon will be further up and easier to see but still near enough the comet to once again serve as an able guide.

A pair of binoculars along with the moon should help you find Comet PANSTARRS tonight. Credit: Kevin Baird

Again, I can’t emphasize enough how useful binoculars are in extending the reach of your vision. For many, they’re absolutely necessary to get a fix on the object in the first place. Once found with binoculars, PANSTARRS with be easier to pin down with the naked eye because you’ll know exactly where to look. 7×35, 7×50, 10×50 or 8×40’s combine ease of use with good light-gathering capability and are widely available.

Comet PANSTARRS caught in a clear gap between clouds yesterday March 11 from Austria. Credit: Michael Jaeger

Once found with binoculars, you’ll find it easier to pick out PANSTARRS with the naked eye because you know exactly where to look. 7×35, 7×50, 10×50 or 8×40’s combine ease of use with good light-gathering capability and are widely available.

I wish I could share my own impressions of PANSTARRS, but it’s been completely overcast here for the past five nights and the next few don’t look any better. Needless to say, I’m chomping at the bit.

By the way, I dug around and discovered how to show the comet’s exact location in the free sky charting software program Stellarium, which is what I used to make the charts in today’s blog.

First, download either the Mac or PC version HERE. Then follow these instructions, provided by Bogdan Marinov with addition tweaks by yours truly. I apologize for the length; readers not interested in plotting the comet’s location can ignore this next section.

Finding a comet with Stellarium

1. Enable the Solar System editor plug-in by clicking on the Configuration window (it will appear as a little box with a wrench icon if you move your pointer to the lower left of the screen.) It will also pop up if you hit “F2″ on your keyboard.
2. Open the Configruation window and go to “Plugins”
3. Select “Solar System Editor” in the left column (the plug-in’s description should appear)
4. If the “load at startup” box is not checked, check it and restart Stellarium.
3. Go to the same plug-in screen, select the same plug-in and click on the “configure” button.
4. In the window that opens, go to the “Solar System” tab, then click on the “Import elements in MPC format window”.
5. In the window that opens, select “Comets”, then “Download a list of objects from the Internet”.
6. If you are using 0.10.6, copy this URL to the “URL” box:
7. If you are using 0.11.0 or higher, just select “MPC’s list of observable comets” from the bookmarks list.
8. Click the “Get orbital elements” button and wait for the file to be downloaded.
9. After it has finished downloading, it should display a list of comets. Find the comet you want to add in the list, check the checkbox in front of it and click the “Add objects” button. In this case, look for C/2011 L4 (PANSTARRS).
10. After the comet has been added, you can find it in the “Search” window: start typing the name of the comet for it to appear in the list of suggestions. The name should be written in the same way as it was displayed in the list as C/2011 L4 (PANSTARRS)
11. Now put in the time and place you want to see the comet and select a horizon with no obstructions. The “Ocean” or “Guereins” views are best. You’ll find them under  “Sky and Viewing Options window/Landscapes”.

It may not show up at first because of the bright twilight sky. To “force” it to appear, go to the “Sky and Viewing Options” box by moving your pointer to the lower left of the screen or hit “F4″. In the “Light Pollution” box, click down to “1”, the least amount of light pollution. The comet should now show up as a point of light just like a star. If not, advance the time a few minutes until the sky gets dark enough for PANSTARRS to appear.

Mercury MESSENGER mission scores 100%

Global maps of Mercury. Half the globe is shown in black & white, the other in color. Each map is composed of thousands of images. Click this and any of the other photos for hi-res versions. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Nice job MESSENGER! After two years in orbit, the entire planet of Mercury has been mapped. Can a cellphone map app be far behind? Prior to MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging), human eyes had seen less than half of the planet up close. No spacecraft had dropped by the solar system’s innermost planet since Mariner 10 sent us the first detailed images of Mercury during three brief flyby loops executed in 1974-75.

Craters (from left) Tolkien, Tryggvadottir and Chesterton are located close to the planet’s north pole and have permanently shadowed floors. MESSENGER found evidence for ice in all three. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Over the past two years the probe has taken more than 168,000 pictures of Mercury’s numerous craters, ridges and enigmatic “hollows”, mapped its topography and determined the makeup of minerals on its surface through examination of the light they reflect from the sun.The probe also revealed water ice coated with organic materials within permanently shadowed craters at the planet’s north pole.

The 20.5-mile-diameter crater Kertesz, named for photographer Andre Kertesz. Mercury craters are named for artists. Kertesz’s floor is pocked by enigmatic “hollows” which could be material boiled off by the sun’s heat and radiation. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

With the probe’s original mission extended from one to two years, it’s now coming to an end. Unless a further extension is approval, March 17 would be the last for data gathering. Principal investigator, Sean Solomon of Columbia University’s Lamont-Doherty Earth Observatory, has submitted a proposal that would keep MESSENGER and mission control in business for another two years, about the time it runs out of fuel and crash lands on Mercury.

Waters crater was recently named in honor of blues legend “Muddy Waters” (a.k.a. McKinley Morganfield). The “mud” pouring out below it is melted rock from the impact. A color image at upper right shows it’s appropriately blue-toned. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Keeping the mission running would let scientists continue targeted studies of various features and shoot photos at incredibly high resolution as MESSENGER’s decaying orbit carries it closer and closer to the surface. Not only that, but the spacecraft is ideally placed to study and photograph Comet ISON when it makes it grazes the sun later this fall.

An oblique view of a 174-mile-long escarpment cutting through a crater. The slope is a geologic fault resembling an “overbite” that formed when the planet shrunk due to cooling of its interior. The left side is 1.2 miles higher than the right. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

To celebrate MESSENGER’s milestone, I thought you’d enjoy a selection of images from recent photo shoots.We’ll know in April whether the mission will continue once a science commission makes its decision. Click HERE to browse more photos in the archive.

A closeup view of hollows in an unnamed crater. The pits almost always occur within or surrounding impact features. They’re about 100 feet to a couple miles wide and lack rims. Hollows might be volcanic vents or created when sulfur and other volatile materials escape from the surface during solar wind bombardment. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Comet PANSTARRS finally sails into northern skies

Comet C/2011 L4 PANSTARRS photographed through a small 4-inch telescope last night March 9 from Sparks, Nevada by amateur astronomer Jay Lawson. Lawson described the comet as difficult to see until near setting, when he finally found it in 7×35 binoculars. Credit: Jay Lawson

We’ve been dogged by clouds, so no Comet L4 PANSTARRS update from my backyard. Others across the U.S. have had better luck, spotting it just a few degrees above the western horizon a half hour after sunset. Despite its current magnitude of around 0 (bright as Vega in the Summer Triangle) the thick, hazy air near the horizon combined with the bright twilight glow have made it difficult to see with the naked eye. That should change in the coming nights as the comet inches upward into a darker sky.

Airplane contrails seen from afar can be easily confused with a comet like PANSTARRS low in the twilight sky. They form when water vapor from burning engine fuel condenses in the cold air at high altitudes.  Binoculars will also often show the plane at the head of the trail. Photo: Bob King

Most observers say PANSTARRS is easy to see in binoculars with a very pretty tail. While you’re out hunting, don’t be fooled by airplane contrails. Sherrie of Ohio shared a photo of a very comet-like object with a bright head and short tail she saw low in the western sky on Friday night the 9th. After looking at several of her photos it became clear she had seen a “tail” of water vapor from a distant jet. In one of the photos, the sun briefly reflected off the plane creating a bright comet “head”. Very convincing.

An airplane contrail masquerading as a comet photographed Friday after sunset from northwestern Ohio. In the photo at left, sunlight briefly glints off the airplane at the head of the trail. At right, the glint is gone. The tilt of the trail also doesn’t match PANSTARRS’ tail angle. Credit: Sherrie Duris

You can tell the difference between a distant contrail and the comet after a few minutes. The contrail will change in length, brightness and overall appearance (or even disappear altogether) while PANSTARRS will look the same from the time you first spot it until setting. That goes for the angle of the tail, too. The comet’s tail is tipped up about 30-40 degrees to the upper right of horizontal. Contrails can appear at a variety of angles.

Video of Comet PANSTARRS setting over the Sierra Nevada Mts. from Sparks, Nevada by Jay Lawson

Today March 10, PANSTARRS reaches perihelion, when it will be closest to the sun at a distance of 28 million miles. This is when the comet feels the sun’s heat most intensely and waxes brightest. Dust-imbedded ices vaporized by sunlight create the comet’s fuzzy head and long tail. Once it leaves the sun’s vicinity, PANSTARRS will slowly fade but appear farther from the sun in a darker sky. With an orbital period of approximately 106,000 years, this will be the first and last chance any of us will behold this messenger from deep space.

Comet PANSTARRS (top center) from Uttarakhand, India at latitude 30 degrees north (same as New Orleans) on March 9. It was not visible with the naked eye but apparent in binoculars . Ajay Talwar joined members of the Amateur Astronomers Association Delhi to view the comet. Credit and copyright: Ajay Talwar

I’m optimistic the best views for the northern hemisphere are yet to come. Use these maps to help you find it. To see more PANSTARRS photos taken from the U.S. and other locales, click HERE.

Russian BLITS satellite blitzed by Chinese space debris

Video simulations of Russian BLITS satellite orbiting Earth and then being struck by debris from the Chinese Fengyun 1C

Russia’s really getting beat up on lately. First the fireball and now one of its satellites gets whacked by a piece of Chinese space junk. In 2007 China performed an anti-satellite weapons test destroying its Fengyun 1C weather satellite leaving in its place thousands of fragments of Earth-orbiting shrapnel.

The spreading debris cloud from the Chinese anti-satellite test in 2007. Left: one month after the hit. Right: 6 months later. Credit: NASA Orbital Debris Program Office

NASA estimates the test created some 950 objects 4 inches (10 cm) or larger in a debris cloud extending from 125 to nearly 2,300 miles (200-3,850 km) high covering all of low-Earth orbit where a great many satellites – including the space station – circle the planet. At the 1/2-inch level, the garbage totals up to more than 35,000 bits and bolts.

This miasmic cloud of human hubris represents the single greatest danger to orbiting satellites since the beginning of the space age. Much of it is hundreds of miles high and will take many years to “decay” or re-enter Earth’s atmosphere.

BLITS is essentially two spheres (one nested in the other) that measures a mere 6.7 inches in diameter. Half of the outer ball has a reflective coatings. Laser light beamed to the satellite returns to Earth. Timing the pulse gives a precise distance to the satellite. Credit: IPIE

The Russian Ball Lens in The Space (BLITS) nanosatellite, a small 16-lb. satellite used for laser-ranging studies, had been functioning properly when on January 22, 2013 it was hit by Chinese satellite debris according to an analysis by the Colorado-based Center for Space Standards and Innovation. Scientists noticed a sudden change in its orbit, spin period (amount of time it take to turn around its axis) and orientation in space. By Feb. 28 they knew the culprit: a chunk of Fengyun 1C debris.

Satellites need to rotate at a precise rate and orientation to maintain contact with Earth as well as serve as useful platforms for experiments. BLITS, now shattered into at least two pieces, tumbles about like a leaf. The satellite was equipped with mirrors called retroreflectors that reflected back brief pulses of laser light shot from an Earth station. By precisely measuring the time for light takes to make the two-way trip, scientists can determine the satellite’s distance to millimeter accuracy.

Frame grab from the video showing the impact of Fengyun 1C debris on a collision course with Russia’s BLITS satellite.

With that data, they’re able to measure Earth’s gravity field and seasonal height variations of the atmosphere, map the surface of the oceans and even tap into the structure of Earth’s interior.

Pity it was likely destroyed. We can only hope this serves as a lesson to other nations who might contemplate similar anti-satellite tests. Littering is bad whether on Earth or in orbit. Read more about the collision HERE.

Thank Butterflies For Daylight Saving Time

Senate Sergeant at Arms Charles P. Higgins turns forward the Ohio Clock for the first daylight saving time, while Senators William M. Calder (NY), Willard Saulsbury, Jr. (DE), and Joseph T. Robinson (AR) look on, 1918. Credit: Wikipedia

Time is what we make of it, and this weekend citizens of 70 countries across the world will advance their clocks one hour ahead in homage to daylight saving time. For U.S. the transition occurs at 2 a.m. Sunday morning March 10. All states except Arizona and Hawaii observe DST.

If you’re into astronomy, daylight saving time has both pluses and minuses. The sun will set an hour later Sunday or just after 7 p.m. Since I get off work around 6:30 p.m. I’ll not only get to drive home in daylight but also have time to drive to a place to spot Comet L4 PANSTARRS.

Without DST, the sun would set around 6 p.m. and I’d have to hurry to catch the comet before it set. On the minus side, that extra hour carried over into the summer means that the sky doesn’t get dark at my location until after 11:30 p.m., necessitating staying up VERY late to look through a telescope at the night sky.

George Vernon Hudson of New Zealand, the first person to make a public proposal for adopting daylight saving time. Credit: Wikipedia

Historians agree that one George Vernon Hudson was behind the creation of daylight saving time. Born in England in 1867, Hudson loved collecting insects. By age 14 he had published his first paper in the British journal The Entomologist  and exhibited a hermaphrodite moth at a meeting of the Royal Entomological Society of London. In 1881 he moved to New Zealand with his father and pursued his insectivorous interests there.

Hudson was also passionate about astronomy. He observed and took notes on eclipses in both England and New Zealand and was one of the discoverers of Nova Aquilae in June 1918. For a brief time this “new star” shone almost as bright as the star Sirius, gaining fame as the brightest nova of the 20th century. You can still see the star – now called V603 Aquilae – to this day in a 6-inch or larger telescope glowing meekly around 12th magnitude. Click HERE for a chart.

1840 painting titled “Der Schmetterlingsjaeger” (The Butterfly Hunter) by artist Carl Spitzweg

In his adopted country, Hudson worked on a farm and then took a job at the post office where he worked until his retirement in 1918. Routine working hours meant he was free in the evenings to pursue insect collecting. No surprise then that Hudson valued all the sunlight he could get, since it afforded him more time to collect his favorite butterflies and and moths.

That’s when he came up with a truly bright idea. Why not extend daylight hours into summer evenings to allow the public to take advantage of outdoor activities?

On October 15, 1895 Hudson read a paper titled On Seasonal Time before the Wellington Philosophical Society. Here’s the nut of his proposal:

“In order to more fully utilise the long days of summer, it is proposed on the 1st October of each year to put the standard time on two hours by making 12 (midnight) into 2 a.m., whilst on the 1st March the time would be put back two hours by making 2 a.m. into 12 (midnight), thus reverting to the present time arrangements for the winter months. The effect of this alteration would be to advance all the day’s operations in summer two hours compared with the present system. In this way the early-morning daylight would be utilised, and a long period of daylight leisure would be made available in the evening for cricket, gardening, cycling, or any other outdoor pursuit desired.”

As you can see, Hudson proposed a two-hour shift that would be reversed in the winter months when people spent more their time indoors (or, ahem, not collecting insects). Although not well-received at the time,  he outlined in detail the benefits of what has since been widely adopted as daylight saving time. Benjamin Franklin had played around with the idea as an exercise to save money on candles back in 1784 but did not carry it further.

Englishman William Willett independently proposes an alternate form of DST to extend summer evening light by incrementally moving clocks forward 20 minutes each Sunday in April and then switching back to standard time by moving clocks back 20 minutes each Sunday in September. Although the proposal was heard by the British Parliament, it failed mostly because farmers didn’t like the idea.

Saving daylight during the World War II years. Credit: Wikipedia

The first countries to adopt the new time were Germany and Austria during World War I as an austerity measure to reduce energy consumption by artificial lighting. Britain and other countries  including the U.S. followed.

Here are some DST highlights in U.S. history:

* After World War I daylight saving time was repealed because it was unpopular.

* Re-instituted  and called “War Time” by President Franklin D. Roosevelt after the Pearl Harbor bombing that brought the U.S. into World War II. War Time was in effect year-round between February 9, 1942 to September 30, 1945.

* Between 1945 and 1966 states could individually decide when to begin and end DST. This caused great confusion in train, plane, bus and broadcasting schedules until the Uniform Time Act of 1966 that fixed the start of daylight time on the last Sunday of April and end on the last Sunday of October.

* After the Arab oil embargo in 1973, Congress extended DST to 10 months in 1974 and 8 months in 1975, returning to the original fixed times in 1976.

* As part of the Energy Policy Act of 2005 and implemented in 2007, DST starts on the second Sunday in March and ends on the first Sunday in November

The countries shown in blue all use DST though the time it begins and ends varies. Credit: Wikipedia

Today over a billion people across the planet use daylight saving time. What was it I read somewhere that the flap of a butterfly’s wings magnified across time could affect the weather on the opposite side of the globe? Hmmm …

EB, EC and now ET – The Asteroids Keep on Coming

Short movie of the asteroid 2013 ET tracking across the sky made over a half-hour on March 4, 2013

Like cars on a freeway, they come out of nowhere, blow by and disappear in the distance. Asteroid 2013 EB passed within a moon’s distance of Earth on Feb. 28, while 2013 EC did the same four days later. Both spanned between 40-50 feet across or slightly smaller than the object that lit up Russian skies three weeks ago.

Radar image of the 230-foot-wide asteroid 2005 YU55 obtained during a flyby of Earth on November 7, 2011. 2013 ET is a tad larger. Both are rocky bodies orbiting the sun in Earth’s vicinity. Credit: NASA / JPL-Caltech

Next up is the heftier 2013 ET which cruises by Earth Saturday morning (6:09 a.m. CST) at a distance of 600,000 miles. That’s about 2 1/2 times the distance of the moon. Astronomers estimate ET’s diameter at 328 feet (100 meters).

None of the earlier flybys posed a threat to Earth and neither will 2013 ET as it diligently follows its path around the sun. You can keep your eyes on the asteroid courtesy of astrophysicist Gianluca Masi and his robotic telescope setup in Italy starting at 1 p.m. (CST) tomorrow March 8. Masi will broadcast the live photos of 2013 ET on WebTV and provide commentary.

Diagram showing the difference in the orbits of typical near-Earth asteroids (in blue) and the smaller subset of potentially hazardous asteroids (PHAs). PHA’s come within 5 million miles of Earth and have the potential, if they survive their flight through the atmosphere, to cause regional or larger-scale damage. Credit: NASA

All three building-sized rocks were discovered very recently. 2013 ET was spotted on March 3 by the Catalina Sky Survey based in the Catalina Mountains north of Tucson, Arizona. Discoveries like these are almost a daily occurrence and highlight the fact that of the estimated one million small near-Earth asteroids out there, we’ve discovered and tracked only 9,754 as of March 4, 2013. That’s less than 1%.

Of these, 861 have diameters of 1 kilometer (0.6 mile) or larger and 1,379 are classified as potentially hazardous, meaning their orbits take them threatening close to our planet. This doesn’t necessarily mean we’ll be hit, just that the potential exists.

Artist’s rendering of the gravity anomaly map of the Chicxulub Crater area. Red and yellow are gravity highs; green and blue are gravity lows. White areas indicate multiple sinkholes. The shaded area is the Yucatán Peninsula. Variations in the density of the rock were used to discover the crater which is buried under several thousand feet of limestone. Credit: Milan Studio

But there’s a silver lining. We’ve already discovered over 90% of the big, kilometer-plus-sized asteroids, greatly reducing the uncertainty of “what’s out there” when it comes to the worst potential impacts. The last really big smack-down of which we’re aware was the impact of a 6-mile-wide asteroid that triggered the mass extinction that wiped out the dinosaurs 65 million years ago. The 110-mile-diameter Chicxulub Crater in the Yucutan Peninsula remains as a testament to this Earth-altering event.

Planetary perspectives inspire appreciation for the little things

Venus is the bright “star” seen among Saturn’s rings in the photo taken by Cassini late last year. The bright arc is Saturn’s atmosphere glowing in backlit sunlight. Light reflected from the rings faintly illuminates the planet. Click to enlarge. Credit: NASA/JPL-CalTech

Nothing beats stepping back to gain a little perspective. NASA recently released a pretty picture of Venus peering through Saturn’s rings. The photo was taken on Nov. 10, 2012 when the Cassini spacecraft orbited the shadowed side of the ringed planet, so we see the rings and atmospheric edge of Saturn backlit by the sun. Venus is a pinprick of light nearly a billion miles away shining through the veil of icy bits that compose the rings.

Venus as seen this morning March 6, 2013 by SOHO’s camera. An opaque disk covers the sun (white circle) allowing astronomers to study the streaky solar atmosphere called the corona.  Venus is currently about 159 million miles from Earth. Credit: NASA/ESA

We also have a more recent photo of Venus taken by the Solar and Heliospheric  Observatory (SOHO) from a different point of view. This picture was taken earlier this morning and shows Venus nearby southwest of the sun. SOHO is parked near the L1 Lagrange point, a spot in space 1 million miles forward of Earth in the direction of the sun. Here the planet’s gravity balances that of the more distant sun allowing the craft to hover in equilibrium with its eye ever focused on the sun. Due to gravitational tugs from the moon and planets, SOHO fires its thrusters every few months to remain in position.

As Venus revolves around the sun, we see it pass through phases just like the moon. Today Venus is near the sun in the sky and appears like a nearly full moon. On the 28th it will be in conjunction and farthest from Earth on the opposite side of the sun. Illustration: Bob King

Venus might look like it’s in the foreground in the SOHO image, but it’s really in the background. On March 28 the planet will pass through superior conjunction when it will appear closest to the sun but located on the farside of its orbit behind it. After that date Venus begins its slow trek back into the evening sky as it comes round to the left or east of the sun. Watch for it to re-appear at dusk in late May.

Venus and Earth are nearly invisible in this wide angle view that includes the sun taken by the Voyager 1 spacecraft in 1990. Click to see the BIG version. Credit: NASA

A tight crop of the wide Voyager 1 photo clearly shows the pale blue dot of Earth. It’s caught in a streak of lens flare caused by the camera pointing directly at the sun. Everything we care about most deeply is contained in that minute fleck of light. Credit: NASA

Let’s pull back a bit more. What do Venus (and Earth) look like from 4 billion miles away, the way the Voyager 1 space probe saw them on Valentine’s Day 1990? Dots of course! Take a close look and you just might be able to see them in the photo. They’re much more obvious the full-resolution image, which can be had for a click.

Earth and the moon from 114 million miles away in the vicinity of Mercury photographed in 2010 by MESSENGER. Click to enlarge. Credit: NASA

Before we wrap up, let’s move in again a little closer and enjoy a picture of the dynamic duo of moon and Earth taken by the Mercury MESSENGER spacecraft from 114 million miles away. While not shot from the planet Mercury, the perspective is nearly identical. Doesn’t it make you feel a little exposed looking at these photos? I mean, there’s so much nothing out there compared to the bits of something. Time to hug my kids again.

Want to see Comet PANSTARRS? We got maps!

Wow! Comet L4 PANSTARRS from Bridgetown, Western Australia on March 3 at dusk. Details: 200mm lens, ISO 1000, 4 secs. at f/4. Credit: Jim Gifford

This is the big week so many of us in the northern hemisphere have been waiting for. Comet C/2011 L4 PANSTARRS, which has put on a splendid show in the southern hemisphere, finally comes to a sky near you.

Sky watchers in Australia report it looks like a fuzzy star as bright as those in the Big Dipper with a short stub of a tail  visible to the naked eye. The comet should brighten further as it wings its way sunward. Closest approach to the sun happens on March 10 at a distance of 28 million miles or about 8 million miles closer than the planet Mercury.

If you live near the equator you can already hunt for PANSTARRS. It will be out tonight March 4 very low in the west-southwest sky 25 minutes after sundown. Depending on your latitude, the comet will make its first appearance over the U.S. March 6-8 assuming the sky at your location is transparent and haze-free.

As described in an earlier blog, PANSTARRS’ low altitude presents a few challenges. Approaching clouds and general haziness near the horizon can make it a tricky to find. The maps should help as will a pair of binoculars. Use them to sweep just above the western horizon later this week to find the comet.

Comet PANSTARRS will be visible tonight through about March 19 for sky watchers living near the equator. Map is drawn for Singapore. All maps created with Chris Marriott’s SkyMap software

As the nights pass, PANSTARRS rises higher in the sky and becomes easier to spot for northern hemisphere observers while disappearing from view in the south. On the 12th, a thin lunar crescent will shine just to the right of the comet. Not only will it make finding this fuzzy visitor easy-peasy, but you’ll have the opportunity to make a beautiful photograph.

Comet PANSTARRS map for the southern U.S. March 6-21. Time shown is about 25 minutes after sunset facing west. Map is drawn for Phoenix, Ariz.

The maps shows the arc of the comet across the western sky in the coming two weeks for three different latitudes. Along the bottom of each map is the comet’s altitude in degrees for the four labeled dates. The sun, which is below the horizon, but whose bright glow you’ll see above its setting point, will help you determine exactly in what direction to look.

One of your best observing tools and the one closest at hand (pun intended) is your hand. Photo: Bob King

A word about altitude. Astronomers measure it in degrees. One degree is the width of your little finger held at arm’s length against the sky. Believe it or not, this covers two full moon’s worth of sky. Three fingers at arm’s length equals 5 degrees or the separation between the two stars at the end of the bowl of the Big Dipper. A fist is 10 degrees.

The northern U.S. is favored for this leg of the comet’s journey. Notice how the comet arcs up higher in the sky compared to the southern U.S. and especially the equator. Map drawn for Duluth, Minn. The comet will remain visible for many weeks. Earth is closest to PANSTARRS on March 5 at 102 million miles.

To find PANSTARRS, locate it on the map for a particular date, note its approximate altitude and relation to where the sun set and look in that direction. Assuming your sky to the west is wide open and clear, you should see a comet staring back. If not, sweep back and forth in the area with binoculars. Sound good? Great – now have at it!

Former supergiant star in Whirlpool Galaxy goes missing

Supernova 2011dh photographed in a spiral arm of the Whirlpool Galaxy on July 4, 2011 from Port Wing, Wis. The other stars you see in the photo are foreground stars in our own Milky Way galaxy. Credit: William Wiethoff

On May 31, 2011 a supernova suddenly appeared in M51, a bright spiral galaxy near the end of the Big Dipper’s handle. Better known as the Whirlpool Galaxy, M51 is one of the most picturesque galaxies in the sky and the first in which spiral structure was seen. The Whirlpool is on every amateur astronomer’s “must see” list because it’s bright, close (23 million light years) and one of the few galaxies that shows a spiral shape in smaller telescopes.

A supergiant star collapses and explodes when it runs out the fuel needed to keep gravity at bay. Often the remnant core further collapses into a neutron star or a black hole. Credit: NASA

The supernova, dubbed 2011dh, peaked in brightness several weeks later and then gradually faded from view. Astronomers determined it was a Type II explosion. Type II supernovae occur in supergiant stars at least 8 times more massive than the sun that burn through the nuclear fuel in their cores until it’s exhausted. When the burning stops, so does the heat pressure that counteracts the ever-present force of gravity. Result: the star collapses in upon itself, creating shock waves that blast it to bits in a titanic explosion. The enormous energy released makes the former supergiant suddenly brighten by millions of times.

Relative size of a supergiant down to a black hole. Exploding supergiant stars sometimes leave a remnant neutron star or black hole in their wake. The crushing forces of collapse push electrons into protons to create neutrons, hence the name.

Often the core continues collapsing into a tiny, city-sized neutron star or takes the final plunge and squeezes itself into a black hole. This weekend a team of astronomers using the Hubble Space Telescope report that the yellow supergiant star that went supernova two years ago has vanished. Gone.

Seems obvious, so what makes it interesting? When a star becomes a supernova, one of the first things astronomers do is go back and look at old pictures of the galaxy in which the supernova occurred to identify the original star called the “progenitor”. Because stars in distant galaxies are extremely faint and difficult to separate from others in their neighborhood, they can be hard to identify.

NASA supernova animation

Now that the suspected supergiant star has disappeared,  we’ve clinched the identity of the star before the explosion. That key data point helps astronomers unravel the evolution of supernova 2011dh from a yellow, hydrogen-burning behemoth to its present state as an expanding shock wave riddled with the former star’s innards.

It also throws a bit of a wrench into our understanding of how stars evolve. The progenitor star began its life with 13 times the sun’s mass and became 100,000 times more luminous than the sun by the time it blew. Yellow supergiants aren’t typical supernova candidates unlike the red supergiant class, whose most famous member is Betelgeuse in Orion. That means that once again astronomers will need to reexamine theories. As for remnants of 2011dh, if there are any, they’ve yet to be found.

Pre-supernova image (left) of 2011dh taken by the Hubble Space Telescope and Gemini NIRI post-supernova image (right). Credit: NASA/ESA and Gemini Observatory

As with people, so with stars – to understand the adult, know the child. The animation shows the whole process from supergiant to supernova followed by the expanding blast wave-gas shell and finally a rapidly-rotating neutron star beaming jets of particles into space.

The moon will shine above Antares tomorrow morning March 4, 2013. The map shows the sky facing south around 5:30 a.m. local time. Stellarium

We have several supernova candidate stars easily visible in the sky from Earth. Betelgeuse in Orion is one, so is Antares, the brightest star in the constellation Scorpius the Scorpion. Both are red supergiants. Tomorrow morning March 4 the waning moon pays a visit to Antares in the wee hours before dawn. Take a look if you happen to be out around 5-6 a.m. and consider its fate.