A Guide to Help You See Comet PANSTARRS at its Brightest

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, now finally comes to a sky near us northerners!

Sky watchers in Australia and southern South America report it looks like a fuzzy star a little brighter than 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. That’s about 8 million miles closer than the orbit of Mercury.

Though very low in the western sky after sundown, the comet should be visible across much of the U.S., southern Canada and Europe beginning tonight March 8.

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
Comet PANSTARRS will be visible 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

PANSTARRS’ low altitude presents a few challenges. Approaching clouds, general haziness and the extra thickness of the atmosphere near the horizon absorbs the comet’s light, causing it to appear fainter than you’d expect. A casual sky watcher may not even notice its presence. That’s why I recommend bringing along a pair of binoculars and using the map that best fits your latitude. Find a place with a wide open view to the west, focus your binoculars on the most distant object you can find (clouds are ideal) and then slowly sweep back and forth across the sky low above the western horizon

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.
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.

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 and thin crescent moon should be a striking site about a half hour to 45 minutes after sunset on March 12. Stellarium
Comet PANSTARRS and the thin crescent Moon should make a striking sight together about a half hour to 45 minutes after sunset on March 12. Stellarium

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
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. This weekend PANSTARRS will be 2-3 “fingers” high around 25 minutes after sunset when the sky is dark enough to go for it.

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.
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 you don’t find it one night, don’t give up. Go out the next clear night and try again. While Comet PANSTARRS will fade over the next few weeks, it will also rise higher into a darker sky and become – for a time – easier to see. I also encourage you to take out your telescope for a look. You’ll see more color in the comet’s head, details in its tail and an intensely bright nucleus (center of the comet), a sign of how fiercely sunlight and solar heating are beating up on this tender object.

Sound good? Great – now have at it!

Comet PANSTARRS Crosses Paths With Zodiacal Light

With the much-anticipated PANSTARRS comet emerging into the evening sky this week, we might keep our eyes open to another sight happening at nearly the same time. If you live where the sky to the west is very dark, look for the zodiacal light, a tapering cone of softly-luminous light slanting up from the western horizon toward the bright planet Jupiter near twilight’s end.

It makes its first appearance about 75 minutes after sunset and lingers for an hour and a half. Sunlight reflected from countless dust particles shed by comets and to a lesser degree by colliding asteroids is responsible for this little-noticed phenomenon. Comets orbiting approximately in the plane of the solar system between Jupiter and the sun are its key contributors. Jupiter’s gravity stirs the works into a pancake-like cloud that permeates the inner solar system.

The zodiacal is formed of dust left behind by comets orbiting between Jupiter and the sun and forms a pancake-like structure in the plane of the planets. Illustration: Bob King
The zodiacal is formed of dust left behind by comets orbiting between Jupiter and the sun and forms a pancake-like structure in the plane of the planets. Illustration: Bob King

More of us would be more aware of the zodiacal light if we knew better when and where to look. While a dark sky is essential, you don’t have to move to the Atacama Desert. I live 9 miles from a moderate-sized, light-polluted city; the western sky is terrible but the east is plenty dark and ideal for watching the morning zodiacal light in the fall months.

Near its base, the cone easily matches the summer Milky Way in brightness and spans about two fists held horizontally at arm’s length. At first glance you’d be tempted to think it was the lingering glow of twilight until you realize it’s nearly two hours after sunset. The farther you follow up the cone, the fainter and narrower it becomes. From top to bottom the light pyramid measures nearly five fists long. In other words, it’s HUGE.

The pyramid-shaped zodiacal light cone is centered on the same path the sun and planets take across the sky called the ecliptic. This map shows the sky 90 minutes after sunset in early March facing west. Created with Stellarium
The pyramid-shaped zodiacal light cone is centered on the same path the sun and planets take across the sky called the ecliptic. This map shows the sky facing west 90 minutes after sunset in early March. Created with Stellarium

The zodiacal light is centered on the same path the sun and planets take through the sky called the ecliptic, an imaginary circle that runs through the familiar 12 constellations of the zodiac. Every spring, that path intersects the western horizon at dusk at a steep angle, tilting the light cone up into clear view. A similar situation happens in the eastern sky before dawn in October. Of course the light’s there all year long, but we don’t notice it because it’s slanted at a lower angle and blends into the hazy air near the horizon.

The zodiacal light we see at dusk is a portion of the larger zodiacal dust cloud that extends at least to Jupiter’s distance (~500 million miles) on either side of the Sun, making it the single biggest thing in the Solar System visible with the naked eye. Under exceptional skies, like those found on distant mountaintops or far from city lights, the cone tapers into the zodiacal band that completely encircles the sky.

The gegenschein is the small, oval glow within the zodiacal band seen in this photo taken at the European Southern Observatory in Chile. Credit: ESO / Yuri Beletsky
The gegenschein is the small, oval glow within the zodiacal band seen in this photo taken at the European Southern Observatory in Chile. Credit: ESO / Yuri Beletsky

Exactly opposite the sun around local midnight, you might see an enhancement in the band called the gegenschein (GAY-gen-shine). This eerie oval glow is caused by sunlight shining directly on interplanetary dust grains and then back to your eye. A similar boost happens for the same reason at the time of full moon.

Deep connections abound throughout the universe. Over time, much of the comet dust in the zodiacal cloud either spirals inward toward the sun or gets pushed outward by solar radiation. The fact that we can still see it today means it’s continually being replenished by the silent comings and goings of comets.

Comet C/2011 L4 PANSTARRS photographed with a 200mm telephoto lens over Bridgetown, Western Australia on March 3. Credit: Jim Gifford
Comet C/2011 L4 PANSTARRS photographed with a 200mm telephoto lens over Bridgetown, Western Australia on March 3.
Credit: Jim Gifford

Consider Comet L4 PANSTARRS. Dribs and drabs of dust sputtered from this comet during its current trip to the inner solar system may find their way into the zodiacal cloud to secure its presence for future sky watchers. How wonderful then the comet and the ghostly light should happen to be at their best the very same time of year.

Zodical light touching the Seven Sisters star cluster also known as the Pleiades March 19, 2012. Credit: Bob King
Zodical light touching the Seven Sisters star cluster also known as the Pleiades March 19, 2012. Credit: Bob King

Now through March 13 is the ideal time for zodiacal light viewing. If you begin your evening with Comet PANSTARRS, stick around until nightfall to spot the light. Face west and cast a wide view across the sky, sweeping your gaze from left to right and back again. Look for a big, hazy glow reaching from the horizon toward the Planet Jupiter. After the 13th, the waxing moon will wash out the subtle light cone for a time. Another “zodiacal window” opens up in late March through mid-April when the moon comes up too late to spoil the view.

As you take in the sight, consider how something as small as a dust mote, when teamed with its mates, can create a jaw-dropping comet’s tail, meet its end in the fiery finale of a meteor shower or span a billion miles of space.

Comet PANSTARRS Cranks up the Volume

Brand new photos from amateur astronomers Michael Mattiazzo and Jim Gifford, both of Australia show the current view of Comet C/2011 L4 PANSTARRS down under, and gives sky watchers in the northern hemisphere hope for great views of in little more than a week. The comet has been brightening steadily and now shines around magnitude 2.6, just a little fainter than the stars of the Big Dipper. More images below:

Comet L4 PANSTARRS on February 28 through an 11-inch telescope. Credit: Michael Mattiazzo
Comet L4 PANSTARRS from Castlemaine, Victoria, Australia on February 28 through an 11-inch telescope. Click for more photos. Credit: Michael Mattiazzo

On February 28, Mattiazzo spotted the comet and a small portion of its dust tail in evening twilight 6 degrees above the western horizon. Using large binoculars he could trace the tail to 1.5 degrees or three lunar diameters. PANSTARRS also has a second fainter dust tail, called a Type III tail, composed of heavier dust particles, dimly visible in the photo below alongside the brighter Type II tail.

Comet L4 PANSTARRS low in the western sky over Western Australia Feb. 27, 2013. Details: 400mm lens
Comet L4 PANSTARRS low in the western sky over Bridgetown, Western Australia Feb. 27, 2013. Click for more photos. Details: 400mm lens, 4-second exposure at ISO 5000. Credit: Jim Gifford

A third ion tail, while not currently visible with the naked eye, shows up well in photographs. Dust tails form when the heat of the sun vaporizes dust-laden ices in the comet’s nucleus; solar photons – literally light itself – gently pushes the dust away from the comet’s head into a long, beautiful tail. Gases like carbon monoxide and cyanogen, which are normally neutral, get their energy levels pumped up by the sun’s ultraviolet light, shed their outer electrons and become “ionized.” The same UV light causes the gases to fluoresce a pale blue.

Additional info: Comet PanSTARRS: How to See it in March 2013

Comets often develop two tails as they near the sun - a curved dust tail and straight, ion tail. Credit: NASA
Comets often develop two tails as they near the sun – a curved dust tail and straight, ion tail.  Dust tails reflect sunlight and appear yellowish. Ion tails glow blue when comet gases are ionized by UV light from the sun and re-emit it as blue. Credit: NASA

Dust tails generally follow the comet’s curving orbit and assume the shape of a gently-curved arc;  ion tails are straight as a stick and point directly away from the sun. Once carbon monoxide molecules have been ionized, they’re susceptible to the magnetic force that flows from the sun as part of the solar wind. The wind with its entrained solar magnetism sweeps by the comet at some 300 miles per second (500 km/sec.) and blows the ion tail straight back exactly opposite the Sun.

With PANSTARRS sprouting tails right and left and peak brightness predictions still around magnitude 1 or 2, get ready for this herald of the new season.

Here’s bascially a naked-eye view of PANSTARRS, taken by Dave Curtis on February 22, 2013 from Dunedin, New Zealand. “The comet was just visible with the naked eye in the twilight,” Dave said. It was taken with a Canon 5D3 and a 70-200mm lens at 70mm:

Comet PanSTARRS on feb. 22, 2013 from Dunedin, New Zealand. Credit: Dave Curtis.
Comet PanSTARRS on feb. 22, 2013 from Dunedin, New Zealand. Credit: Dave Curtis.

Russian Fireball Inspires Journey into the World of Meteorites

A little more than week ago a 7,000 ton, 50-foot (15-meter) wide meteoroid made an unexpected visit over Russia to become the biggest space rock to enter the atmosphere since the Tunguska impact in 1908. While scientists still debate whether it was asteroid or comet that sent a tree-flattening shockwave over the Tunguska River valley, we know exactly what fell last Friday.

Now is a fitting time to get more familiar with these extraterrestrial rocks that drop from out of nowhere.

The Russian meteoroid – the name given an asteroid fragment before it enters the atmosphere – became a brilliant meteor during its passage through the air. If a cosmic rock is big enough to withstand the searing heat and pressure of entry, fragments survive and fall to the ground as meteorites. Most of the meteors or “shooting stars” we see on a clear night are bits of rock the size of apple seeds. When they strike the upper atmosphere at tens of thousands of miles an hour, they vaporize in a flash of light. Case closed.  But the one that boomed over the city of Chelyabinsk was big enough to to survive its last trip around the Sun and sprinkle the ground with meteorites.

The two main smoke trails left by the Russian meteorite as it passed over the city of Chelyabinsk. Credit: AP Photo/Chelyabinsk.ru
The two main smoke trails left by the Russian meteor as it passed over the city of Chelyabinsk. Credit: AP Photo/Chelyabinsk.ru

Ah, but the Russian fireball didn’t get off the hook that easy. The overwhelming air pressure at those speeds combined with re-entry temperatures around 3,000 degrees F (1,650 C) shattered the original space rock into many pieces. You can see the dual trails created by two of the larger hunks in the photo above.

Scientists at Urals Federal University in Yekaterinburg examined 53 small meteorite fragments deposited around a hole in ice-covered Chebarkul Lake 48 miles (77 km) west of Chelyabinsk the following day. Chemical analysis revealed the stones contained 10% iron-nickel metal along with other minerals commonly found in stony meteorites. Since then, hundreds of fragments have been dug out of the snow by people in surrounding villages. As specimens continue to be recovered and analyzed, here’s an overview — and a look at what we know — of these space rocks that pay us a visit from time to time.

Bright fireball breaking up over Yellow Springs, Ohio. Credit: John Chumack
Bright fireball breaking up over Yellow Springs, Ohio. Credit: John Chumack

How many times has a meteor taken your breath away? A brilliant fireball streaking across the night sky ranks among the most memorable astronomical sights most of us will ever see. Like objects in your side view mirror, meteors appear closer than they really are. And it’s all the more true when they’re exceptionally bright. Studies show however that meteors burn up at least 50 miles (80 km) overhead. If big enough to remain intact and land on the ground, the fragments go completely dark 5-12 miles (8-19 km) high during the “dark flight” phase. A meteor passing overhead would be at the minimum distance of about 50 miles (80 km) from the observer.

Since most sightings are well off toward one direction or another, you have to add your horizontal distance to the meteor’s height to get a true distance. While some meteors are bright enough to trick us into thinking they landed just over the next hill, nearly all are many miles away. Even the Russian meteor, which put on a grand show and blasted the city of Chelyabinsk with a powerful shock wave, dropped fragments dozens of miles to the west. We lack the context to appreciate meteor distances, perhaps unconsciously comparing what we see to an aerial fireworks display.


Very cute Youtube video of  Sasha Zarezina, 8, who lives in a small Siberian village, as she hunts for meteorite fragments in the snow after Friday’s meteor over Russia. Credit: Ben Solomon/New York Times

An estimated 1,000 tons (907 metric tons) to more than 10,000 tons (9,070 MT) of material from outer space lands on Earth every day delivered free of charge from the main Asteroid Belt.  Crack-ups between asteroids in the distant past are nudged by Jupiter into orbits that cross that of Earth’s. Most of the stuff rains down as micrometeoroids, bits of grit so small they’re barely touched by heating as they gently waft their way to the ground. Many larger pieces – genuine meteorites – make it to Earth but are missed by human eyes because they fall in remote mountains, deserts and oceans. Since over 70% of Earth’s surface’s is water, think of all the space rocks that must sink out of sight forever.

A fragment of the Sikhote-Alin iron meteorite that fell over eastern Russia (then the Soviet Union) on Feb. 12, 1947. Some of the dimpling are pockets on the meteorite's surface called regmeglypts. Credit: Bob King
A fragment of the Sikhote-Alin iron meteorite that fell over eastern Russia (then the Soviet Union) on Feb. 12, 1947. Credit: Bob King

About 6-8 times a year however, a meteorite-producing fireball streaks over a populated area of the world. Using eyewitness reports of time, direction of travel along with more modern tools like video surveillance cameras and Doppler weather radar, which can ping the tracks of falling meteorites, scientists and meteorite hunters have a great many clues on where to look for space rocks.

Since most meteorites break into pieces in mid-air, the fragments are dispersed over the ground in a large oval called the strewnfield. The little pieces fall first and land at the near end of the oval; the bigger chunks travel farthest and fall at the opposite end.

When a new potential meteorite falls, scientists are eager to get a hold of pieces as soon as possible. Back in the lab, they measure short-lived elements called radionuclides created when high-energy cosmic rays in space alter elements in the rock. Once the rock lands on Earth, creation of these altered elements stops. The proportions of radionuclides tell us how long the rock traveled through space after it was ejected by impact from its mother asteroid. If a meteorite could write a journal, this would be it.

Other tests that examine the decay of radioactive elements like uranium into lead tells us the age of the meteorite. Most are 4.57 billion years old. Hold a meteorite and you’ll be whisked back to a time before the planets even existed. Imagine no Earth, no Jupiter.

10x closeup of a very thin section through a chondrule in the meteorite NWA 4560. Crystals of olivine (bright colors) and pyroxene are visible. Credit: Bob King
10x closeup of a very thin slice through a chondrule in the meteorite NWA 4560. Crystals of olivine (bright colors) and pyroxene (grays) are visible. Credit: Bob King

Many meteorites are jam-packed with tiny rocky spheres called chondrules. While their origin is still a topic of debate, chondrules (KON-drools) likely formed when blots of  dust in the solar nebula were flash-heated by the young sun or perhaps by powerful bolts of static electricity. Sudden heating melted the motes into chondrules which quickly solidified. Later, chondrules agglomerated into larger bodies that ultimately grew into planets through mutual gravitational attraction. You can always count on gravity to get the job done. Oh, just so you know, meteorites are no more radioactive than many common Earth rocks. Both contain trace amounts of radioactive elements at trifling levels.

A stunning slice of the Glorieta pallasite meteorite cut thin enough to allow light to shine through its many olivine crystals. Click to see more of Mike's photos. Credit: Mike Miller
A stunning slice of the Glorieta pallasite meteorite cut thin enough to allow light to shine through its many olivine crystals. Click to see more of Mike’s photos. Credit: Mike Miller

Meteorites fall into three broad categories – irons (mostly metallic iron with smaller amounts of nickel), stones (composed of rocky silicates like olivine, pyroxene and plagioclase and iron-nickel metal in form of tiny flakes) and stony-irons (a mix of iron-nickel metal and silicates). The stony-irons are broadly subdivided into mesosiderites, chunky mixes of metal and rock, and pallasites.

Pallasites are the beauty queens of the meteorite world. They contain a mix of pure olivine crystals, better known as the semi-precious gemstone peridot, in a matrix of iron-nickel metal. Sliced and polished to a gleaming finish, a pallasite wouldn’t look out of place dangling from the neck of an Oscar winner.  About 95% of all found or seen-to-fall meteorites are the stony variety, 4.4% are irons and 1% stony-irons.

A slice of the NWA 5205 meteorite from the Sahara Desert displays wall-to-wall chondrules. Credit: Bob King
A slice of the NWA 5205 meteorite from the Sahara Desert displays wall-to-wall chondrules. Credit: Bob King

Earth’s atmosphere  is no friend to space rocks. Collecting them early prevents damage by the two things most responsible for keeping us alive: water and oxygen. Unless a meteorite lands in a dry desert environment like the Sahara or the “cold desert” of Antarctica, most are easy prey to the elements. I’ve seen meteorites collected and sliced open within a week after a fall that already show brown stains from rusting nickel-iron. Antarctica is off-limits to all but professional scientists, but thanks to amateur collectors’ efforts in the Sahara Desert, Oman and other regions, thousands of meteorites including some of the rarest types, have come to light in recent years.

Greg Hupe, renowned meteorite hunter, wears a big smile after finding a fresh 33.7g meteorite of the Mifflin, Wis. fall in 2010. Credit: Greg Hupe
Greg Hupe, renowned meteorite hunter, wears a big smile after finding a fresh 33.7g meteorite of the Mifflin, Wis. fall in 2010. Credit: Greg Hupe

Hunters share their finds with museums, universities and through outreach efforts in the schools. A portion of the material is sold to other collectors to finance future expeditions, pay for plane tickets and sit down to a good meal after the hunt. Finding a meteorite of your own is hard but rewarding work. If you’d like to have a go at it, here’s a basic checklist of qualities that separate space rocks from Earth rocks:

* Attracts a magnet. Most meteorites – even stony ones – contain iron.
* Most are covered with a matt-black, slightly bumpy fusion crust that colors dark brown with age. Look for hints of rounded chondrules or tiny bits of metal sticking up through the crust.
* Aerodynamic shape from its flight through the atmosphere, but be wary of stream-eroded rocks which appear superficially similar
* Some are dimpled with small thumbprint-like depressions called regmaglypts. These form when softer materials melt and stream away during atmospheric entry. Some meteorites also display hairline-thin, melted-rock flow lines rippling across their exteriors.

Beware of imitations! These are chunks of industrial slag that are often confused with real meteorites. Meteorites don't have bubbly surfaces. Credit: Bob King
Beware of imitations! These are chunks of industrial slag that are often confused with real meteorites. Meteorites don’t have bubbly surfaces. Credit: Bob King

Should your rock passes the above tests, file off an edge and look inside. If the interior is pale with shining flecks of pure metal (not mineral crystals), your chances are looking better. But the only way to be certain of your find is to send off a piece to a meteorite expert or lab that does meteorite analysis. Industrial slag with its bubbly crust and dark, smooth volcanic rocks called basalts are the most commonly found meteor-wrongsWe imagine that meteorites must have bubbly crust like a cheese pizza; after all, they’ve been oven-baked  by the atmosphere, right? Nope. Heating only happens in the outer millimeter or two and crusts are generally quite smooth.

 

NWA 3147 is an achondrite eucrite meteorite most likely from the asteroid Vesta. You can see it has no chondrules. Credit: Bob King
Look Ma, no chondrules. NWA 3147 is an achondrite eucrite meteorite that probably originated from the asteroid Vesta. Credit: Bob King

Stony meteorites are further subdivided into two broad types – chondrites, like the Russian fall, and achondrites, so-called because they lack chondrules. Achondrites are igneous rocks formed from magma deep within an asteroid’s crust and lava flows on the surface. Some eucrites (YOU-crites), the most common type of achondrite, likely originated as fragments shot into space from impacts on Vesta. Measurements by NASA’s Dawn space mission, which orbited the asteroid from July 2011 to September 2012, have found great similarities between parts of Vesta’s crust and eucrites found on Earth.

We also have meteorites from Mars and the Moon. They got here the same way the rest of them did; long-ago impacts excavated crustal rocks and sent them flying into space. Since we’ve studied moon rocks brought back by the Apollo missions and sampled Mars atmosphere with a variety of landers, we can compare minerals and gases found inside potential moon and Mars meteorites to confirm their identity.

Some of the 53 meteorites found around Chebarkul Lake. Many are coated with a thin crust of melted and blackened rock heating by the atmosphere. The sign reads: Meteorite Chebarkul. Credit: AP / The Urals Federal University Press Service, Alexander Khlopotov
Some of the 53 chondrite meteorites found around Chebarkul Lake. Many are coated with a thin crust of melted and blackened rock heating by the atmosphere. The sign reads: Meteorite Chebarkul. Credit: AP / The Urals Federal University Press Service, Alexander Khlopotov

Scientists study space rocks for clues of the Solar System’s origin and evolution. For the many of us, they provide  a refreshing “big picture” perspective on our place in the Universe.  I love to watch eyes light up with I pass around meteorites in my community education astronomy classes. Meteorites are one of the few ways students can “touch” outer space and feel the awesome span of time that separates the origin of the Solar System and present day life.

Bright New Supernova Shines in Southern Skies

I live in the frozen north by choice, but occasionally I yearn for warmer places like Tucson and Key West. These feelings usually start in late February, when after nearly four months of winter, the season feels endless. Today I wish I could head down south for another reason – to see a very bright supernova in a galaxy in Lupus.

Stu Parker. Credit: BOSS
Stu Parker. Credit: BOSS

SN 2013aa popped off in the barred spiral galaxy NGC 5643 in the constellation Lupus the Wolf 34 million years ago, but no one knew its light was wiggling its way across the cosmos to Earth until New Zealand amateur astronomer Stu Parker nailed it during one of his regular supernovae hunts. Parker recorded it on Feb. 13, 2013. Since it was so far from the galaxy, he thought at first it was a hot pixel (electronic artifact) or an asteroid. Another look at the galaxy 5 minutes later confirmed it was really there.

Good thing. It turned out upon confirmation to be the brightest supernova he and his band of supernova hunters had ever discovered.

Stu is a member of a 6-man amateur supernova search team from Australia and New Zealand called BOSS (Backyard Observatory Supernova Search). They’ve been working together since 2008 with the goal of searching for and reporting supernovae in the southern sky. When a member finds a candidate, they contact profession astronomers who follow up using large telescopes. To date the group has found 56 supernovae with Stu discovering or co-discovering 45 of them!

Map showing the sky looking south around 5 a.m. local time from Tuscon, Arizona. The new supernova in galaxy NGC 5643 is low in the southern sky before dawn for observers in the southern U.S. and points south. Created with Stellarium
Map showing the sky looking south around 5 a.m. local time from Tuscon, Arizona. The new supernova in galaxy NGC 5643 is low in the southern sky before dawn for observers in the southern U.S. and points south. Created with Stellarium

From the northern U.S., much of Lupus and especially the supernova never make it above the horizon, but from about 35 degrees north and points south, SN 2013aa is fair game. The “new star” lies southwest of the core of galaxy NGC 5643, which shines at magnitude 10, bright enough to see in a 6-inch telescope from a dark sky. The supernovae is still climbing in brightness and today gleams at about 11.6 magnitude – no problem in that 6-inch if you’re equipped with a good map or photo to help get you there.

In this annotated version of the Joseph Brimacombe's photo, I've suggested a straightforward "star hop" from the galaxy's nucleus to the supernova.
In this annotated version of the Joseph Brimacombe’s photo, I’ve suggested a straightforward “star hop” from the galaxy’s core to 2013aa using brighter foreground stars.

Based on the study of 2013aa’s light, astronomers have classified it as Type Ia. Before the explosion, the star was a white dwarf, a superdense, planet-sized object with the mass of the sun. Tiny but mighty, the white dwarf’s powerful gravity pulled material from a nearby companion star down to its surface. When a dwarf puts on enough pounds to exceed 1.4 times the sun’s mass, the extra material increases the pressure and temperature of the core and the star burns explosively.

In a Type Ia supernova, a white dwarf (left) draws matter from a companion star until its mass hits a limit which leads to collapse and then explosion.
In a Type Ia supernova, a white dwarf (left) draws matter from a companion star until its mass hits a limit which leads to runaway burning and a catastrophic explosion that obliterates the star.

The energy released increases the star’s brightness to 5 billion times that of the sun. Matter from the blast streaks into space at speeds of 3,000-12,000 miles per second. Yes, this is a BIG deal and one of the most energetic events the universe has to offer. No wonder amateurs like myself can’t get enough of them.

NGC 5643 is best placed in the southern sky around 5 a.m. local time. From Lexington, KY. (latitude 38 degrees N.) it’s only 8 degrees high or slightly less than one fist held at arm’s length. Tuscon’s better at 14 degrees and Key West (latitude 25 N) best at 21. Farther south, your views will continue to improve. And the pleasant temperatures can’t hurt either.

You can start with the bright pair of Saturn and Spica midway up in the southern sky. Look about two outstretched fists below them to find Theta Centauri and from there “three fingers” to the lower left (southeast) to Eta Centauri. The galaxy is about 1 1/2 degrees southwest of Eta. The supernova will look like an 11 1/2 magnitude star 74″ west and 180″ south of the galaxy’s bright core. Use the annotated photo to help guide you straight to it.

To keep track of the 2013aa’s progress as well as view many more photos, I highly recommend David Bishop’s Latest Supernovae site.

The Year of the Comets: Three Reasons Why 2013 Could be the Best Ever

2013 could turn out to be a comet bonanza. No fewer than three of these long-tailed beauties are expected to brighten to naked eye visibility. Already Comet C/2011 L4 PANSTARRS has cracked that barrier. Sky watchers in Australia have watched it grow from a telescopic smudge to a beautiful binocular sight low above the horizon at both dusk and dawn. A few have even spotted it without optical aid in the past week. Excited reports of a bright, fan-shaped dust tail two full moon diameters long whet our appetite for what’s to come.

Recent brightness estimates indicate that the comet could be experiencing a surge or “second wind” after plateauing in brightness the past few weeks. If the current trend continues, PanSTARRS might reach 1st or 2nd magnitude or a little brighter than the stars of the Big Dipper when it first becomes visible to northern hemisphere sky watchers around March 7. That’s little more than two weeks away!

Comet Panstarrs will make its first appearance for northern hemisphere sky watchers around March 7 low in the western sky after sundown. Notice that the comet gets no higher than 10 degrees - about one fist held at arm's length - through much of the month. Illustration created using Chris Marriott's SkyMap software
Comet Panstarrs will make its first appearance for northern hemisphere sky watchers around March 7 low in the western sky after sundown. Notice that the comet gets no higher than 10 degrees – about one fist held at arm’s length – through much of the month. Illustration created using Chris Marriott’s SkyMap software

Every day between now and March 10, when PanSTARRS’ orbit takes it closest to the sun, the comet is expected to slowly increase in brightness. Later this month it disappears in the solar glare, but when it re-emerges into evening twilight around Thursday, March 7, northern and southern hemisphere observers alike will get great views. Binoculars should easily show a bright head and swept-back tail pointing away from the sun. And don’t forget to mark your calendar for March 12. On that date the thin lunar crescent will join the comet for a rare photogenic pairing. To locate and keep track of PanSTARRS, you’ll need the following materials and circumstances:

* An unobstructed view of the western horizon
* Clear, haze-free skies at dusk
* Pair of binoculars
* A map

I can’t help you with all of the above, but this map will help point you in the right direction. Once you find a location with a great western view, watch just above the horizon for a fuzzy, star-like object in your binoculars. While it’s possible the comet will be bright enough to see with the naked eye, binoculars will make finding it much easier. They’ll also reveal details of tail structure too subtle to be visible otherwise.

Incredible detail is seen in the gas tail of F6 Lemmon in this photo made with a 19.6-inch telescope Feb. 17, 2013. Credit: Martin Mobberley
Incredible detail is seen in the gas tail of F6 Lemmon in this photo made with a 19.6-inch telescope Feb. 17, 2013. Credit: Martin Mobberley

Comet PanSTARRS has some cometary company.  C/2012 F6 Lemmon is currently plying its way through the constellation Tucana the Toucan, shining right around the naked eye limit at magnitude 5.5. To the unaided eye, Lemmon looks like a dim fuzzy spot. Binoculars show a thin gas tail and big, bright head or coma. Comas develop around the comet’s icy nucleus as sunlight vaporizes dusty ice to create a short-lived atmosphere that in the shape of a luminous teardrop. Long-exposures like the one above reveal richly-detailed streamers of carbon monoxide and other gases fluorescing in sunlight in the comet’s fashionably skinny tail.

Lemmon is slowly receding from Earth this month, but should remain just above the naked eye limit for some time as it continues to approach the sun. Northern hemisphere observers will need to be patient to see this one. After looping around the sun on March 24, the comet will pop back into the morning sky near the familiar Square of Pegasus asterism in early May. If we’re lucky, Lemmon may still be near the naked eye limit and visible in ordinary binoculars.

Cmet C/2012 F6 (Lemmon), imaged on  Feb. 19. 2013 remotely from Q62 (iTelescope Observatory, Siding Spring). Credit: Ernesto Guido and Nick Howes, Remanzacco Observatory.
Cmet C/2012 F6 (Lemmon), imaged on
Feb. 19. 2013 remotely from Q62 (iTelescope Observatory, Siding Spring). Credit: Ernesto Guido and Nick Howes, Remanzacco Observatory.

Before we move on to the comet with the greatest expectations, I want to mention Comet 2P/Encke. Encke was the only the second comet to have its orbit computed – way back in 1819 by German astronomer Johann Encke. This year it’s making its 62nd observed return to Earth’s vicinity. That’s a lot of visits, but when your orbital period is only 3.3 years – the shortest known of any comet – you can’t help but be a regular visitor. While not expected to brighten to naked eye level, the comet will be a fine sight in modest-sized telescopes glowing around 8th magnitude when it tracks between the Big Dipper and Leo the Lion this October.

Comet ISON in the western sky shortly after sunset in late November this year. Illustration created with Chris Marriott's SkyMap software
Comet ISON in the western sky shortly after sunset in late November this year. Illustration created with Chris Marriott’s SkyMap software

Our final comet, Comet C/2012 S1 ISON, was discovered last September by Russian amateurs Vitali Nevski and Artyom Novichonok while making observations for the International Scientific Optical Network (ISON). At the time, it was farther than Jupiter and impossibly faint, but once ISON’s orbit was determined, astronomers realized the comet would pass only 1.1 million miles from center of the sun (680,000 miles above its surface) on November 28, 2013.

Comet ISON belongs to a special category of comets called sungrazers. As the comet performs a hairpin turn around the sun on that date, its ices will vaporize furiously in the intense solar heat. Assuming it defies death by evaporation, ISON is expected to become a brilliant object perhaps 10 times brighter than Venus. Or brighter. Some predict it could put the full moon to shame. If so, that would occur for a brief time around at perihelion (closest approach to the sun) when the comet would only be visible in the daytime sky very close to the sun. When safely viewed, ISON might look like a brilliant, fuzzy star in a blue sky.

A color image of comet Ison taken on February 5, 2013 from northern Arizona. Credit: Chris Schur.
A color image of comet Ison taken on February 5, 2013 from northern Arizona. Credit: Chris Schur.

Most of us won’t risk burning our retinas staring so close to sun. Instead we’ll watch with anticipation as the comet sprouts a long tail while ascending from the western horizon just after sunset in late November and early December. Whatever it does, sky watchers in both southern and northern hemispheres will ringside seats when ISON’s at its best.

Right now the comet’s whiling away its time in the constellation Gemini the Twin and still very faint. Come September, it should be easily visible in small telescopes in the morning sky. The first naked eye sightings could happen in late October. Many of us hope the comet will be one for the record books, a worthy successor to C/2006 P1 McNaught, the last “great comet” to dazzle human eyes. It reached peak magnificence for southern hemisphere sky watchers in January 2007.

C/2006 P1 McNaught became a memorable sight for observers living in southern latitudes in January 2007.  Will Comet ISON do the same? Credit: Wikipedia
C/2006 P1 McNaught became a memorable sight for observers living in southern latitudes in January 2007. Will Comet ISON do the same? Credit: Wikipedia

Three bright comets – and one modestly bright – might be enough for a year, but there could be surprises. Dozens of new comets are discovered each year by professional sky surveys and amateur astronomers. Most are faint and move along their appointed paths unnoticed by 99.9% of the world’s population, but every so often a new one comes along that blossoms into a spectacle. How many of  those are out there tonight waiting to be discovered?