Tag Archives: supernova

Amateur astronomers eye new supernova in galaxy NGC 4414

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The new supernova 2013df is 32″ east and 14″ north of the center of the spiral galaxy NGC 4414 in Coma Berenices. This photo was taken on June 10, 2013. Credit: Joseph Brimacombe

A new gem sparkles in Berenice’s hair. Supernova 2013 df burst to light in the spiral galaxy NGC 4414 in the constellation Coma Berenices (Queen Berenice’s Hair). The exploding star was discovered on June 7 by four Italian amateur astronomers who are members of the Italian Supernova Search Project (ISSP).

NGC 4414, host of the new supernova, is located near the star Gamma in Coma Berenices. Use the detailed map below to get you in for a closer look. The moon is shown for tonight June 13. Created with Stellarium

The supernova shimmers at about 13th magnitude – on the brighter side for a star going boom 62 million light years away – and is visible from dark skies in telescopes 8 inches or larger. The host galaxy is moderately small but bright at 10th magnitude and very easy to spot in smaller scopes. Pinned to its northeast side along the outer rim of the galaxy’s hazy disk, the supernova is hard to miss. You can try for it anytime starting at the end of evening twilight until 2 or 3 a.m. Earlier is better because the galaxy’s higher in the sky. I caught a view of this “new star” two nights ago around 11 o’clock in my 15-inch scope. Very easy to see.

Illustration of a massive star ending its life as a Type II supernova. Credit: ESO

Tagged as a Type IIb supernova, 2013df star-like appearance only hints at the enormous violence involved in its creation. Type II supernova explosions 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 pressure from heat 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.

Closeup map showing NGC 4414, surrounding galaxies and the star Gamma in Coma Berenices to help you point your telescope. Click image for an even more detailed finder chart. Credit: made by Jan Wisniewski with Guide 7.0 software

The enormous energy released makes the former supergiant suddenly brighten by millions of times. That’s why even amateur telescopes can pick up this titanic event across millions of light years.

The “b” in Type IIb indicates a star that’s lost hydrogen gas in its outer atmosphere before the catastrophe.

For more information, updates and photos on 2013df, check out Dave Bishop’s Latest Supernovae site.

New supernova in M65 plays game of hide-and-seek

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M65 (top right) joins M66 (bottom) right and NGC 3628 in the constellation Leo the Lion. The three, nicknamed the Leo Triplet, are all easily visible in small telescopes and approximately 35 million light years from Earth. Credit: Hunter Wilson

Hundreds of supernovas are discovered every year, most in dim galaxies with names like UGC 10610 or NGC 2554. It takes a good star chart and a determined amateur astronomer to find these little buggers concealed in their galactic hideouts. That’s why when news comes of a supernova in a Messier galaxy, we get excited.

All 110 Messiers objects. M1 at upper left; M110 at lower right. M65 is boxed in red. Click for large version. Credit: Rolando Ligustri

Galaxies in the catalog prepared by 18th century French comet hunter Charles Messier are bright and relatively close. After all, those were the only ones astronomers could see at the time using the technology of the day. Messier’s favorite scope had a mirror only 7.5 inches (19 cm) in diameter, barely equivalent to one of today’s common 6-inch reflecting telescopes, but with it, he discovered numerous new star clusters and galaxies.

Supernova 2013am shines forth on March 28, 2013 in the galaxy M65.  The explosion is a Type II supernova that happens when a supergiant star runs out of fuel at the end of its life. With no energy to push back the force of gravity, the star collapses in on itself,  rebounds with explosive force and rips itself to shreds. Credit: William Wiethoff

So when news came on March 21 that M. Sugano, of Kakogawa, Japan had spotted a new supernova in the galaxy M65 – the 65th entry in Messier’s catalog of 110 objects – amateur astronomers expected the star to brighten to magnitude 11 or 12, shiny enough to nab in even a pedestrian 4.5-inch reflector.

Fine and good, but thanks to dust, that may never happen. Now known officially as supernova 2013am, the new star was very faint when Sugano first spotted it. Nothing unusual there. Both amateur and professional astronomers keep such a close eye on the sky these days with nightly vigils and automated surveys, most supernovas are discovered near the start of their eruptions when they’re still dim.

Within a week, a typical nearby supernova beams brightly enough to show in amateur telescopes. Not 2013am. It’s been 10 days and the star remains stubbornly faint. Professional astronomers examined the light of the supernova on March 22 and gleaned a couple interesting tidbits. First, the blast is tearing the it apart, sending debris into space at over 4,300 miles (7,000 km) per second. Second, the star’s light is “reddened” or dimmed by dust along our line of sight.

This color photo taken on March 31 clearly shows the red hue of the new supernova (arrowed) in M65. Just to the right and below the star is a small, dark patch of interstellar dust. Credit: Bill Williams

Looking at photos of M65 you can see that the supernova lies along or inside a dark patch of interstellar dust, so called because it’s sprinkled among and between the stars. The dust originates from current and previous generations of stars that have lost material to space both gently as they evolve and through supernova explosions.

Sunsets are red for a similar reason stars are reddened by interstellar dust. Dust and other fine aerosols in the atmosphere scatter away the blues and greens of light while the red and oranges penetrate without difficulty. Photo: Bob King

My hunch is that this dusty redoubt blocks and reddens the light of 2013am much the way a volcanic dust or a sand storm absorbs and reddens the light of the sun. Astronomers called the phenomenon extinction. When it comes to dimming stars, all colors of light are not created equal. Fine dust preferentially scatters away more blue light than red, giving otherwise hot blue stars a warm red tone shown so well in Bill’s photo.

2013am is laying low and playing hard to see for now. It’s possible the star may still brighten enough to show in small telescopes. We’ll just have to wait and see. You can monitor Dave Bishop’s M65 supernova page for further developments.

Last night under a very dark sky I glimpsed it in a 15-inch (37 cm) telescope at the limit of my vision at around magnitude 16. It reminded me of finding one of my daughters hidden behind the closet door in a game of hide-and-seek. Gotcha!

Hey, where are all the Milky Way supernovas?

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The scene witnessed by Johannes Kepler after sunset on Oct. 17, 1604. While he wasn’t the first to see the supernova, Kepler studied it like no one else. To recognize his detailed observations, we now call it Kepler’s Supernova. Created with Stellarium

Hard to believe it’s been over 400 years since anyone’s seen a supernova in the Milky Way galaxy. Amateur and professional astronomers spot them all the time in galaxies external to our own. In 2012 alone 1,048 supernovas were discovered thanks to numerous, mostly-automated searches that photograph hundreds of galaxies each night looking for signs of exploding stars. Given such a large sample, it should come as no surprise that dedicated supernovae searches turn up these “new stars” routinely.

Johannes Kepler in 1610

The last person to see one with his own eyes was astronomer Johannes Kepler, famous as the first person to explain the Laws of Planetary Motion. The new star blazed forth on October 9, 1604 in southern Ophiuchus, a summertime constellation visible in the southwestern sky during early fall. Observing from Prague, overcast skies prevented his from seeing it until the 17th.

When the clouds parted, Kepler got an eyeful. The supernova, which soon waxed as brilliant as Jupiter (mag. -2.5), shone in the company of three bright planets – Mars, Saturn and Jupiter. He must have been beside himself with amazement at the gathering of so many shiny objects together in one corner of the sky.

Kepler relentlessly observed the new star every clear night until at dusk and in the winter months at dawn until it finally faded from view in March 1606. Not long after, he penned a book with his observations titled De Stella Nova. In it Kepler compared the new star with the Star of the Magi and speculated that it might lead to the conversion of the Indians in America. You can flip through a digital version of the tome HERE.

Only 3 years later Galileo would turn one of his early telescopes to the sky. Had the telescope been invented just a few years earlier, Kepler could have continued his supernova observations much longer.

The expanding supernova remnant Cassiopeia A is located near the place John Flamsteed recorded a star in 1680. Working back from the currently observed expansion point to an explosion indicates the supernova would have been visible in the sky around 1667. Photo made with the Hubble Space Telescope. Credit: NASA / ESA

In 1680 English astronomer John Flamsteed recorded a faint 6th magnitude star in the constellation Cassiopeia during his compilation of a new star catalog. Labeled 3 Cassiopeiae, the star was omitted from later catalogs since it couldn’t be found again. 300 years later astronomers discovered a faintly-glowing husk of light called a supernova remnant – the leftover, expanding clouds of gas and debris near the position of Flamsteed’s star. It’s possible he may have seen it during its explosive phase or simply made a mistake in a star position.

Composite of photos showing an all-sky view of the Milky Way. The dark blobs are cosmic dust within the galaxy that blocks the light of stars behind it. Copyright: Axel Mellinger

Previous to Kepler’s supernova was the great daylight supernova of 1572 studied by Kepler’s mentor Tycho Brahe. That’s two in 32 years and nothing since. What gives? Astronomers estimate a star goes boom in the Milky Way galaxy about once every 50 years. Shouldn’t we have seen another in 400 years? Blame it on cosmic dust.

Stardust shed by supernovae and through gentler means permeates space and concentrates in the plane of the galaxy where most of the Milky Way’s approximately 400 billion stars reside. To stare across a few light years of space, you’d never notice it. But over hundreds of light years the dust adds up, effectively screening billions of stars from view and greatly reducing chances of seeing a supernova anytime soon.

Supergiant stars like Betelgeuse in Orion and Antares in Scorpius are both extremely large and extremely rare.

There’s another factor, too. One class of supernovas, called Type II, happen when a supergiant star runs out of fuel to burn. With no heat to hold back the inward pull of gravity, it implodes and then explodes.

These monsters are rare. 80% of stars are tiny, long-lived red dwarfs; 3.5% are stars like our sun and supergiants account for measly 0.001% of known stars. With so few to pick from and dust an issue, it’s yet another way the odds are stacked against seeing a local supernova.

Radio images made by the VLA of supernova remnant G1.9+0.3 show it expanding about 15% over a period of 23 years. Credit: NRAO / VLA / D. A. Green

Not that the galaxy’s been slacking off. The most recent Milky Way supernova was announced in May 2008 by a team of astronomers using the dust-busting Very Large Array (VLA) radio telescope in New Mexico, and confirmed in X-ray images from the Chandra X-ray Observatory in orbit. Both telescopes study the sky at wavelengths of light than can penetrate dust to see what lurks beyond.

G1.9+0.3 is another supernova remnant like Cas A – the expanding remains of the exploded star. It’s located close to the center of the galaxy and utterly obscured from visual view by thick clouds of interstellar dust. Working backward from now to the point of explosion, astronomers estimate the star went supernova about 140 years ago. Were it not for dust, citizens of the Victorian era would have marveled at their new star.

This is the remnant of Kepler’s Supernova. The red, green and blue colors show low, intermediate and high energy X-rays observed with NASA’s Chandra X-ray Observatory, and the star field is from the Digitized Sky Survey. The remnant resulted for Type Ia explosion, where a tiny, dense white dwarf star pulls material from a close companion star onto its surface, becomes unstable and explodes. Other supernovas happen when a supergiant star runs out of fuel at the end of its life and implodes-explodes. Click photo for more info.  Credit: NASA/CXC/NCSU/M.Burkey

Somewhere out there a Milky Way star has self-destructed in a supernova explosion. Light from the cataclysm is streaming our way at this very minute. Will it pass unscathed and surprise us tonight or be foiled by dust once again?

Former supergiant star in Whirlpool Galaxy goes missing

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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.

Meet Rigel in Orion, a star with supernova potential

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Both Betelgeuse and Rigel are potential supernova candidates. The view shows the sky facing southeast around 8 p.m. local time in early January.  Maps created with Stellarium

Everybody’s always worried about Betelgeuse in Orion blowing up as a supernova. There’s a good chance that may happen one day, but no need to panic. The star’s too far away to trouble earthlings with its future fireworks. Opposite Betelgeuse and below the winsome triad of stars that form Orion’s Belt, another potential supernova star sparks and sputters on winter nights – Rigel. The name comes from ancient Arabic and refers to the foot or leg of Orion.

Like Betelgeuse, Rigel (RYE-jel) is also a supergiant star but one of a different color and temperature. Astronomers classify it as a blue supergiant with a surface temperature of over 20,000 degrees, twice that of the sun and 3 1/2 times hotter than Betelgeuse.

Rigel, a blue supergiant star, is 18 times more massive than the sun and 74 times its size. Credit: CWitte with minor alterations by Bob King

At a distance of 860 light years, Rigel is big enough and close enough to have its diameter measured directly. As you might guess, it’s huge – 74 times the size of our sun.

Placed where the sun is now, this stellar beast would extend nearly to the orbit of Mercury. From Earth, Rigel would span 35 degrees of sky and shine at a blinding -38 magnitude. We’re talking a powerful sunburn in a minute or two.

Great distance tames Rigel’s true ferocity as a young, energy gobbling star into a pretty blue-white twinkle reminiscent of sunlight on snowflakes. Rigel shines at 0.1 magnitude or about as bright as Capella in Auriga and Vega in Lyra.

Being extremely hot, blue supergiants burn up their energy stores quickly. At the tender age of 10 million years (young for a star), Rigel has already depleted its core of hydrogen fuel and has moved on to burning hydrogen in a surrounding shell.

If put in place of the sun 93 million miles from Earth, Rigel would cover 35 degrees or sky or about twice the area of the constellation Orion.

Helium “ash” created from hydrogen burning will one day ignite and serve as fuel as will progressively heavier elements like oxygen, neon and silicon over time. Rigel will puff up and redden just like Betelgeuse in those far-off days.

Just before a supergiant star blows it has a core made of iron that cannot “burn” to create energy to push back the force of gravity. Gravity takes hold and the star collapses.

Unfortunately, supergiant stars reach the end of the line once all the remaining silicon fuel has undergone nuclear fusion to create a core of iron. Iron requires more energy to fuse than the energy it releases, so it won’t burn like the other elemental fuels. With no burning to push back against the crushing force of gravity in so large a star, the core collapses and sends out shock waves that rip it apart in a supernova explosion.

Rigel is a close double star in a small telescope. Use 100x and up to split it cleanly. Credit: Fresno State University Observatory

When will this happen? Probably millions of years down the road. Since Rigel’s 300 light years farther from Earth than Betelgeuse, we needn’t worry about it either. Instead, our future descendants should prepare for a wondrous light show. Jim Kaler, professor emeritus at the University of Illinois, estimates that Rigel will become as bright as the half-moon when it finally blows up. Picture all that light concentrated in a tiny point of light. We’d easily see our shadows at night by supernova light!

If you have a small telescope 4.5 inches or larger, point it at Rigel some night. It’s one of the finest, if challenging, double stars in the sky. The 7th magnitude companion peaks out from under the glare of the main star a very short distance (9 arc seconds) to its south. On a night with steady air and good seeing, this pair is a beautiful sight.

NASA pings asteroid 2007 PA8; bright supernova pops in Great Barred Galaxy

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This composite image of asteroid 2007 PA8 was obtained using data taken by NASA’s 230-foot-wide (70-meter) Deep Space Network antenna at Goldstone, Calif.  on Oct. 28, 29 and 30, 2012. Credit: NASA/JPL-Caltech/Gemini

Most asteroids look like stars in nearly every telescope because they’re too small and too far away to register as anything more than dots.  Radio waves work better. Given a close pass, NASA’s 230-foot-wide Deep Space Network radio telescope at Goldstone, Calif. can synthesize an image of an Earth-approaching asteroid by bouncing radio waves off it and recording the “echo” of the returning waves. The pictures it provides are surprisingly  detailed given how small most of these objects are.

The mile-wide 2007 PA8 flew only 5.6 million miles from Earth on Oct. 30 and got its portrait taken on Oct. 28, 29 and 30. Pictures show a rough-looking, elongated “boulder” with ridges and possible craters. JPL scientists chose to image asteroid due to a favorable combination of size and relative proximity to Earth at the point of closest approach.

The date also indicate that 2007 PA8 is rotating rather slowly, spinning just once approximately every 3-4 days. Good thing NASA made the most of this opportunity – this flyby was the closest Earth approach by this asteroid for at least the next 200 years.

Earth-approaching asteroid discoveries are fairly common nowadays thanks to the many surveys underway at observatories around the world. In the next week alone, four recently-discovered tiny asteroids – 2012 VB5, 2012 UV136, 2012 VQ6 and 2012 UY68 -  ranging in size from 56 to 144 feet will zip by Earth between 432,000 and 1.6 million miles away. None poses any danger to the planet.

Located 61 million light years away in the faint constellation Fornax the Furnace, 9.6 magnitude NGC 1365 is 200,000 light years across and one of the largest spiral galaxies known. Credit: ESO/IDA/Danish 1.5 m/ R. Gendler, J-E. Ovaldsen, C. Thöne, and C. Feron

Like watching stars blow up? A recently discovered supernova in the southern galaxy NGC 1365 is now bright enough for amateur astronomers to spot in small to medium-sized telescopes. The galaxy, nicknamed the Great Barred Spiral Galaxy, is one of the most beautiful in the sky with sharply-etched spiral arms winding about its bar-like center. Droves of youthful stars populate the blue-tinted arms, while older stars illuminate the bar a warm yellow.

SN2012 fr is almost due north of the core of NGC 1365. Exact position is 52″ north, 2″ west. The “new star” is a Type Ia supernova, the violent explosion of a white dwarf star. This photo was taken on Nov. 4, 2012. Credit: Joseph Brimacombe

I only wish this gorgeous galaxy were higher in the sky from the northern U.S. As it is, it never climbs more than 7 degrees (less than one fist held at arm’s length) high in the southern sky. Skywatchers across the central and southern part of the country will find it both higher and easier to see.

The new supernova, dubbed SN2012 fr, was discovered by the automated La Silla TAROT telescope in Chile on Oct. 27, 2012 at 15th magnitude (dim!). It’s since rocketed to about 12th magnitude which puts into the range of a 6-inch telescope, especially for southern observers. It’s still brightening at this time so may become an easier target yet.

Type Ia supernovas occur in close binary stars where one member is a white dwarf. The dwarf’s gravity pulls material from the companion until the dwarf hits a weight limit of 1.38 times the mass of the sun. When that moment occurs, its core burns destructively.

SN2012 fr is the end of the line for a planet-sized but superdense white dwarf star that put on too much weight from munching on a nearby companion star. The material collected on the dwarf’s surface, increasing the pressure on the star’s core and initiating runaway burning. Like an uncontrolled wildfire, the energy released as carbon and oxygen in the core were set aflame blew the star to bits. Astronomers call a white dwarf detonation a Type Ia supernova.

This map shows the sky facing south around midnight local time in mid-November in the northern U.S. Orion is high in the southeast. To his right is the long, gangly constellation Eridanus the River. Follow the river down to the stars g and h Eridani. The supernova and galaxy lie 2 degrees due west of these stars in neighboring Fornax.  Maps created with Stellarium

For more information and pictures of supernova 2012fr please check out Dave Bishop’s Latest Supernovae site.

Use this closeup chart of NGC 1365 and neighborhood to track down the galaxy in your telescope.

Supernova imposter 2009ip finally comes clean

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Discovery photo taken in August 2009 of the supernova imposter in the galaxy NGC 7259. It was 18th magnitude at the time. Credit: CHilean Automatic Supernovas sEarch

Polyjuice. Once swallowed, the magic potion of the Harry Potter movies allows the user to assume the appearance of any person for just one hour. Starting in 2009, astronomers have witnessed something of this “polyjuice factor” in a star in a galaxy 66 million light years away. With one difference. The change appears permanent.

On August 26, 2009 the team of astronomers at the CHilean Automatic Supernovas sEarch (CHASE) discovered what they first thought was a brand new supernova in the galaxy NGC 7259 in the constellation Piscis Austrinus the Southern Fish. It even got one of those cool supernova names – SN 2009ip. But further study of older pictures taken by the Hubble Space Telescope as well as follow up observations revealed that the speed of the material blasted away by the star as well as its intrinsic brightness didn’t match that of a supernova. Astronomers realized they were seeing an outburst of a bright blue star called a luminous blue variable or LBV instead.

Eta Carinae in the southern Milky Way is probably the most famous nearby LBV. A large eruption in 1843, when the star became the second brightest star in the sky, created the curious twin-lobed cloud of gas and dust called the Homunculus Nebula. Eta’s about 8000 light years from Earth. Credit: NASA/ESA

LBVs are brilliant, massive, extremely hot supergiant stars that burn their fuel rapidly and live short lives of several million years compared to the sun’s ~10 billion year lifetime. Just to give you an idea, our supernova imposter packs away 50 to 80 times the mass of the sun and blazes hundreds of thousands of times brighter. Radiation raging from the interiors of LBVs causes the stars to sputter and spew portions their atmosphere into space. Some slough off the equivalent of the sun’s mass in just 10,000 years. Spendthrifts of the universe.

Along with losing mass, an LBV’s light varies almost continuously from day to day with bigger variations over longer time spans caused by large outbursts that release lots of matter into an ever-expanding envelope centered on the star.

The LBV in NGC 7259 re-brightened in July this year and became much brighter in September and October as it evolved into a supernova. This picture was taken on October 8 when 2009ip was magnitude 13.5 – bright enough to see in a 6-inch telescope. Credit: Joseph Brimacombe

Continued observation of SN 2009ip turned up a second outburst in 2010. This was further confirmation that the star didn’t destroy itself in a supernova explosion after all but returned to shine another day.

Then in July It re-brightened again, but this time astronomers at several observatories, using spectrographs to tease apart the star’s light, discovered dramatic changes in its appearance. You know what they say – the third time’s the charm.

Not only was it much brighter than the earlier outbursts, but the hotheaded sun was blasting out matter at supernova-style speeds of over 8,000 miles per second. Additional details of the star’s spectrum or light fingerprint all pointed to one thing: 2009ip appears to have become a real supernova right before our eyes!

Its rapid surge in brightness indicates that high-speed material flung from the host star has crashed into the older envelope of matter shed by previous eruptions. What’s driving all this new activity? As described earlier, big stars are the gas-guzzlers of the universe, rapidly consuming every drop of nuclear fuel in their cores. The pressure from burning keeps gravity at bay, but when 2009ip’s needle hit empty, the fire went out and its core caved in to the force of gravity, creating a shock wave that ripped the behemoth to shreds. Bada boom! A star dies, a supernova is born.

During a core collapse or Type II supernova, a shock wave surges from core to surface, tearing the star apart. Sometimes a tiny, dense remnant called a neutron star remains after the explosion. Credit: ESO

Supernovas located in galaxies in the far southern sky are not easy to see from a northern place like Duluth, Minn., yet this one grew bright enough earlier this month to stand out clearly in my 15-inch scope. SN 2009ip is still hanging in there at magnitude 13.9, making it a fine showpiece for enterprising amateurs. To keep tabs on it and see more photos, I recommend a trip to David Bishop’s special page on the object. If you’d like to read a detailed analysis, check out this paper on the topic by a team of astronomers at the Universities of Arizona and California.

Since stars live exceptionally long lives far in excess of the human time scale, we normally have to observe thousands of them and piece the observations together using computer models to build a full picture of a stellar lifetime. Seeing 2009ip flirt with destruction and then finally detonate in the space of three years offers astronomers – amateur and professional – a rare glimpse of stellar evolution in real time.

New supernova in Virgo bright enough for modest telescopes

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Dragon berthed to the Harmony node of the International Space Station. Credit: NASA TV

The hatch between the newly-arrived SpaceX Dragon capsule and the space station was opened early this morning as the crew began today to unload food, clothes and batteries.

Astronaut Don Pettit commented on the “new car smell” and well-designed layout of the ship. They’ll reload the capsule with science equipment and send it back on its way to Earth soon. The commercial craft was designed to be re-useable;  routine flights to the space station are scheduled to begin in August.

Supernova 2012 cg is in the "V" of Virgo west of Epsilon Virginis and not far from Rho and 20 Virginis. Created with Stellarium

On May 17 the automated Lick Supernova Supernova Search (LOSS)  discovered a new supernova in the galaxy NGC 4424 in the constellation Virgo not far from the planet Saturn. Only 18th magnitude at the time of discovery and impossibly faint to see, the star has since skyrocketed to around 12.7, making it a worthy target for amateur telescopes 6 inches and larger.

Last night it outshone the galaxy’s own nucleus, which is comprised of at least several billion stars. That gives you an idea of how brilliant this exploding star truly is. The supernova is embedded within the galaxy’s hazy disk some 17 arc seconds east of center.

Supernova 2012 cg is 17" east and 1.5" north of NGC 4424's nucleus. The picture was taken by amateur astronomer William Wiethoff of Port Wing, Wis. on May 21. The numbers next to the stars below the galaxy are magnitudes. The higher the number, the fainter star. View is shown through a typical telescope with south up and east to the right.

Using a spectrograph, a device that breaks up a star’s light into a rainbow fingerprint of colors, astronomers have determined that 2012 cg is a Type Ia supernova. 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.

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.

When a dwarf puts on enough pounds to exceed 1.4 times the sun’s mass, it can longer support itself and collapses and self-detonates in an explosion that blasts it to bits. Lucky earthlings can witness the incredible event from the comfort of their patios.

NGC 4424 is one of many galaxies in Virgo, so take your time using the map to arrive at the right one.

Star-hop from Epsilon to Rho to 20 and over to a trio of galaxies including NGC 4424. It shines 11th magnitude, and looks like a fuzzy patch. The supernova is the little star blazing inside it. Stars shown to mag. 9.5. Created with Chris Marriott's SkyMap software

Since 2012 cg was discovered early in the explosive phase, it brightened quickly and is still climbing. You can watch it change in the coming days and weeks by using the star magnitudes – direct from the American Association of Variable Star Observers (AAVSO) - shown in the photo above. That’s how I estimated the supernova’s magnitude at 12.7 last night May 25. For more information and photos, please stop by David Bishop’s Latest Supernovae site, the one-stop shop place for what’s shakin’ in the world of exploding stars.

Dueling bright supernovas in M95 and NGC 4790 kick off new season

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Two bright supernovae in galaxies M95 and NGC 4790 are currently visible in small to moderate-sized telescopes. North is up, west to the right in both pictures. Credits: Martin Mobberley (Ieft) and William Wiethoff

60 million years ago a supergiant star exploded in the galaxy NGC 4790 in Virgo. 22 million years later another overgrown and underfed supergiant star ended its life in the galaxy M95. After all that time traveling through space, the light from each explosion arrived within two days of each other in the skies over planet Earth. What a joy to see them both in their final glory.

Supernova 2012 aw has been getting most of the attention lately, because it was discovered in a bright galaxy not far from the planet Mars in Leo. Most supernovae are caught on the rise to maximum light. This one was no exception. 2012 aw was first spotted at 15th magnitude (dim!) by Paolo Fagotti and Alessandro Dimai of the Italian Supernovae Search Project, and independently by Jure Skvarc (Crni Vrh Observatory, Slovenia) on March 16. A day later it rose to 13th magnitude which put it within range of many amateur telescopes. Today March 21, the supernova still hovers at around 13th magnitude, though it’s uncertain if it will brighten further or plateau.

Stay back! An artist's view of a supergiant star undergoing core collapse to become a supernova. Credit: ESO

Studying its light with a spectrograph, an instrument that drags a fine-toothed comb though a star’s light to determine its chemical makeup, speed of rotation and the like, astronomers discovered that M95′s supernova is a Type IIP. Type II tells us this was a supergiant star that used up all the available nuclear fuel in its core. With nothing left to burn, the star’s internal “furnace” shut down, gravity took hold and the whole works collapsed in upon itself at speeds up to 45,000 miles per second.

When the outer layers reached the core, they crushed it into a dense ball of subatomic particles and sent a powerful shock wave back towards the surface that helped tear the star apart, creating a supernova. New radioactive forms of elements like nickel and cobalt were created by the tremendous pressure of the explosion; their decay into stable forms releases energy that contributes to the supernova’s light. The “P” by the way stands for plateau. Type IIP supernovae level off in brightness more slowly, plateauing for a time before fading away.

Galaxies M105, NGC 3384 and NGC 3389 in Leo. Although composed of billions of stars like our Milky Way, most scopes see them as hazy patches. They're too far to resolve into individual stars. Credit: Jim Misiti

A supernova is really the only way beginning and amateur astronomers can see a star in another galaxy. Galaxies beyond the Milky Way system – which includes our nearby satellite galaxies the Magellanic Clouds – are too far away for most telescopes to resolve into stars. All those billions of stars in the thousands of galaxies visible in amateur telescopes look like pale white fuzz that remind me of cocoons. Not so when a supernova blows. We finally get to see across the light years at an individual star waving farewell.

To get an idea of how bright the supernovae in M95 and NGC 4790 are, take a look at Arcturus, the bright star in the northeastern sky found below the arc of the Big Dipper’s Handle. If you placed either SN 2012 aw or SN 2012 au at Arcturus’ distance of 34 light years, each would shine at better than magnitude -15 or a full magnitude brighter than the full moon. Image all that light squeezed into a point in the sky. Think how bright that would be and the shadows it would cast at night. What power!

Just before a supergiant star blows it has a core made of iron that cannot "burn" to create energy to power the star. Gravity takes hold and the star collapses. Supergiants are several hundred times larger than our sun.

I was asked today whether you can see M95′s supernova in a small, 4-inch telescope, and the answer is yes – if you observe from a dark sky in  good seeing (steady, non-turbulent air) using higher magnifications (150x). The limit for a 4-inch is 13.2 magnitude. A 6-inch scope is better and it should be easy in an 8-inch. By good fortune, the star is far from the galaxy’s center where it might otherwise be camouflaged by a haze of spiral arms.

But what about SN 2012 au? Let’s not pass it by. After all, it’s even brighter than the one blazing in M95. This Type II supernova is nearly dead center in NGC 4790 in Virgo and currently shines at 12.7 magnitude or nearly a half-magnitude brighter than 2012 aw – well within the 4-inch limit. The reason it might be overlooked is that 4790 is a smaller, fainter galaxy and not as easy to find. Try using this finder chart for NGC 4790 from this earlier blog. Once you spot the galaxy, you can’t miss the supernova.

Finder charts and other details on M95 are HERE and HERE. David Bishop, keeper of the Latest Supernovae site, always has updated information on current supernovae bright and faint.

Venus just going through a phase

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Venus (top) and Jupiter together in the western sky at dusk this weekend. Photo: Bob King

It’s hard to let go of Jupiter and Venus. They’re still so fine to look at in the western sky at twilight. Through the telescope, Venus is a near perfect half moon and about as far from the sun as it gets. Greatest eastern elongation  – maximum distance east of the sun – happens next Tuesday the 27th, when the planet will be 46 degrees from our star at sunset or halfway between the horizon and overhead point. It sets four hours later – only a few minutes before midnight – seen from northern Minnesota.

As Venus orbits the sun, it alternates between appearances in the evening and morning sky, spending about 9 1/2 months as a “morning star” and the same amount of time as an “evening star”.  Because we look inside our orbit toward the sun to spy Venus, we see the planet swing from one side of the sun to the other but never straying from it more than 46 degrees. That’s why Venus is only visible during twilight and at most a couple hours beyond nightfall.

Venus looks like a half-moon in a small telescope now into next week when it reaches its greatest elongation from the sun. The changing geometry of Venus, sun and Earth causes the planet to show phases like the moon. Illustration: Bob King

The outer planets like Mars and Jupiter are different. Since they lie outside Earth’s orbit, they can appear behind us directly opposite the sun. We have to “turn around” in a manner of speaking, to see them. When a planet is opposite the sun, it rises at sunset and remains visible all night. You might say the outer planets are capable of elongations of 180 degrees compared to Venus’ 46. Mercury, closer to the sun yet, only manages 28 degrees elongation at best.

In late March, Venus appears as a dazzling half-moon, because it forms a right angle with the Earth and the sun and is equidistant from both. As we head into April, its phase will narrow at the same time it moves closer to Earth. In a month, even 10x binoculars will show the planet as a distinctive crescent. Take a few minutes the next clear night to point a small telescope Venus’ way. Try to catch it during early twilight – the brighter the sky, the easier it will be to see the little half moon without glare.

M95 and the supernova at left. At right is a map of Mars and the galaxies M95 and M96. Mars is shown starting tonight through the 29th. The circle is 5 degrees across. Photo: William Wiethoff. Map created with Chris Marriott's SkyMap

I looked at the supernova in M95 last night and found it very easy to see at 13th magnitude southwest of the galaxy’s core. It’s the only “star” in that spot, so you really can’t confuse it with anything else. As promised, here’s a chart showing Mars’ changing position in relation to the galaxy over the next couple weeks. Amateur astronomer William Wiethoff of Port Wing, Wisconsin battled moths and turbulent air last night to make a nice image of the new supernova. Thank you Will!