Introduction

A woman stands small and exposed beneath a clear night sky. As she gazes up at the vast mist of stars, one point suddenly burns immeasurably brighter. She may not realize it, but this pinprick of brilliance hails from the furthermost reaches of our Milky Way Galaxy: a distant exploding star. It has taken nearly a hundred millennia for this light to speed across the void, a vision of the ancient past finally glimpsed by human eyes.

No celestial event stresses the universe’s gulfs of distance and time more than a supernova. These dying stars can burn as bright as a billion suns, outshining whole galaxies and releasing the very energy and materials required to give birth to new cosmic bodies.

The Guest Star (SN 185)

Astronomers estimate that supernovae occur in the Milky Way Galaxy a mere two or three times a century. Even then, catching a glimpse of distant stellar self-destruction is often a matter of being in the right hemisphere at the right time. Curiously enough, despite having studied the sky for thousands of years, the first recorded supernova in human history occurred in A.D. 185.

According to the “Hou Hanshu,” the official history of the Later Han Dynasty, Chinese astronomers spotted a “guest star” in the southern sky. They described it as displaying five colors and gradually vanishing from the heavens seven months later.

Eighteen centuries later, some modern astronomers argue that the guest star was merely a comet, but others stand by the supernova theory. As you might imagine, an exploding star tends to leave a mark on the universe, which we call supernova remnants. When the star explodes, the shockwave from the blast heats up and stirs material it encounters, leaving a kind of heat signature that can emit X-ray radiation for thousands of years to follow.

That’s where supernova remnant RCW 86 enters the picture. Given its location and age, some astronomers believe this vast cloud may be all that remains of the star that became SN 185.

  Tycho’s Supernova (SN 1572)

While stargazers spotted other “guest stars” in the sky between A.D. 185 and the late 16th century, it wasn’t until SN 1572 that a supernova really altered the course of human events.

For 2,000 years, astronomers had held to Aristotle’s notion that the sun, moon and planets revolved around the Earth in concentric circles. The outermost circle was home to the stars. Beyond that, you had the sphere of the “Prime Mover,” or God.

Then in A.D. 1572, Danish astronomer Tycho Brahe noted a brilliant new star in the sky. Fascinatingly, the star did not appear to move in relation to the other stars, indicating that it lay far beyond Aristotle’s starry sphere in what was supposed to be the perfect, unchanging realm of the divine.

This discovery not only helped invalidate Aristotle’s view of the stars, but also launched Tycho’s career to new heights. Soon, kings were buying him observatories and the brilliant astronomer was able to lay the groundwork for many cosmic revelations to follow. His published his observations on the mysterious star in “The Nova Stella” in 1574. Later, the work’s title would serve as the basis for the word “supernova.”

  Kepler’s Supernova (SN 1604)

A student of Tycho Brahe, Johannes Kepler followed fervently in his master’s footsteps. He even managed to find his own supernova as well. He spotted the new light in the sky in October of 1604 and, two years later, addressed its astronomical properties in “De Stella Nova in pede Serpentarii.” This and other works from the dedicated stargazer further helped to discredit the old way of looking at the universe. He proved the planets follow elliptical orbits and worked out the relationship between speed and distance from the sun.

Kepler studied his supernova until it faded from view in 1606. During that time, he was forced to use the naked eye, as the telescope was not invented until 1609. Ironically enough, Kepler’s star would be the last supernova visible without the aid of a telescope for 400 years.

Today, Kepler is known as the father of celestial mechanics and SN 1604 remains the last observable supernova to take place in our galaxy.

   S Andromedae (SN 1885A)

Prior to 1885, the few supernovae we’d observed were all relatively local affairs. Then, in 1885, an Irish amateur astronomer by the name of Isaac Ward reported seeing a bright, reddish object in the sky. Ironically, a French astronomer had noted the star two days earlier, but had attributed it to a telescope defect.

 A Light in the Large Magellanic Cloud (SN 1987A)

For 400 years, not a single supernova was visible to the naked eye. Then, in 1987, the cataclysmic light from a dying star in the Large Magellanic Cloud dwarf galaxy appeared. Located in the Tarantula Nebula, SN 1987A quickly became the most studied supernova in history, due to the huge number of amateur astronomers and the star’s relative closeness to Earth (168,000 light years).

Earth didn’t just get a lightshow out of SN 1987A; we were also showered with subatomic particles from the blast — 25 neutrinos to be exact. Supernovae generate these minute particles in astronomical quantities. As they blast outward from the star’s original location, they typically fly right through normal matter. However, specially-designed neutrino telescopes in Japan, Russian and the United States were able to detect their passing, and recorded data that has help
ed support several theories regarding how stars collapse.

The 1987 supernova is also notable in that it didn’t grow dimmer following its initial explosion, but actually emitted greater quantities of X-ray and radio wavelengths. This was due to the explosion’s shockwaves burning though thick clouds of gas and dust.

Champagne Supernova in the Sky (SN 2003fg)

Yes, “Champagne Supernova” is more than a popular track from Oasis, it was also an actual 2003 supernova that rocked our estimations on just how exploding stars behave (insert your own Liam Gallagher joke here).

There are several known varieties of supernovae and the one we named after a late-90s Britpop tune happens to be a type la. This variety occurs when a white dwarf star absorbs matter from a neighboring star before exploding. In studying these, astronomers observed that the dwarf blows when it approaches 1.4 solar masses. We call this the Chandrasekhar limit, named for the 1930s Indian physicist Subrahmanyan Chandrasekhar.

Then came SN 2003fg, blasting through everything we’d come to expect from type Ia supernovae. It shouldn’t have been possible, but the white dwarf swelled to two solar masses before exploding. So much for understanding the stars. As a result, SN 2003fg earned the “Champagne” moniker, as well as such classifications as “rogue supernova” and “super-Chandrasekhar supernova.”

Death of a Cosmic Titan (SN 2006gy)

On Sept. 18, 2006, astronomers enjoyed quite the cosmic light show as the biggest and brightest supernova on record called out to us from the NGC 1260 galaxy in the constellation Perseus. Experts estimate that the blast was roughly 100 times greater than a typical supernova and that the dying star might have been 150 times the size of our own sun — right up there at the theoretical limits.

Many of the universe’s first generation stars are thought to have been this large, which makes SN 2006gy a rather fascinating peek into just how those primordial suns may have worked. Previously, most experts theorized that such large stars inevitably collapsed into black holes.

Prior to detonation, SN 2006gy expelled a great deal of mass — an interesting fact given that the colossal star Eta Carinae, in our own galaxy, is displaying the same activity. Given that SN2006gy occurred 240 million light years away and Eta Carinae is only 7,500 light years away, try to imagine just how bright its death might burn in the sky.

 Twin Supernovae (SN 2007ck and SN 2007co)

What’s more powerful than a supernova? Why, two going off at once, of course. In 2007, NASA’s Swift satellite tuned into this double feature as SN 2007ck and SN 2007co exploded in short succession in the MCG +05-43-16 galaxy. This also marked the first observed supernova in that particular star cluster, located 380 million light-years from Earth.

Upon further investigation, astronomers determined that the two stars had died of different causes. SN 2007ck was a type II, which occurs when the core of a massive star runs out of fuel for the nuclear reactions and collapses under its own gravity. SN 2007co, on the other hand, was a type Ia event (like the Champaign Supernova), which occurs when a white dwarf explodes.

These two cosmic deaths occurred just 16 days apart. Typically, supernovae only occur in a given galaxy every 25 to 100 years. There is no indication that the two events are linked to each other.

The Young Remnants (G1.9+0.3)

So far, we’ve looked at some truly epic spans of time. Even when we’re talking about a supernova spotted in the last few years, the event itself may have occurred hundreds of millions of years ago. This is often the norm when it comes to studying the cosmos, so it should come as no surprise that some of the more exciting supernova news of late concerned the most recent case of a star exploding in our own galaxy.

In 1985, astronomers indentified radio signals from supernova remnant G1.9+0.3. In 2007, NASA’s Chandra X-ray Observatory collected new data on the cloud of heated dust and gas. By comparing the differences in the two observations, scientists were able to calculate exactly when the star had exploded. According to NASA, the explosion occurred about 140 years ago. Prior to this discovery, the most recent known supernova in the Milky Way occurred around 1680.

 Old-school Supernovae

When it comes to dramatic star death scenes, Supernova remnant G1.9+0.3 represents one end of the spectrum: local and recent. On the far end of the spectrum, however, you can find such cosmically ancient explosions as the supernova discovered in 2009 by University of California’s Jeff Cooke and his team of researchers.

The team used an image stacking technique to detect slight flashes of light amid the stars and found two supernovae, each estimated to be 11 billion years old. To put that in the necessary perspective, remember that the universe itself is thought to be only 13.7 billion years old. The findings still await further study and evaluation from other astronomers, but the news has still stirred quite a bit of excitement through professional and amateur stargazers alike.

All of human history is less than a speck of dust compared to the cosmos. Yet while supernovae drive this sobering point home rather succinctly, they also provide a bit of encouragement to a fleeting, small and mortal species. In this universe, one moment in time can ring out across cosmological epochs and achieve a kind of permanence.

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