Tycho’s Supernova: An Explosive Change to the Universe as We Knew It

Chandra X-Ray Telescope image of Tycho's Supernova Remnant.

“Oh thick wits. Oh blind watchers of the sky.” This is the tone with which Tycho Brahe, the greatest naked-eye astronomer to ever live, began his landmark work, De Nova Stella, On the New Star*. It was this work that coined the modern term “nova” and later earned the naming of “Tycho’s Supernova”, which I have chosen as the 9th object in my top 10 favorites countdown. Around 9,000 years after the supernova explosion occurred, its light first arrived at Earth in November of 1572. It appeared beside the constellation Cassiopeia, The Queen, and at its peak brightness was visible even during the day.

Star map of Cassiopeia from De Nova Stella. The nova is the brightest star, labeled I.

On seeing the nova for the first time, Tycho wrote: “I was so astonished by this sight that I was not ashamed to doubt the trustworthiness of my own eyes. But when I observed that others, on having the place pointed out to them, could see that there was really a star there, I had no further doubts.” He was so impressed by the sight that he would devote the rest of his life to astronomy, and by excruciatingly careful observations, would be the first to meaningfully undermine the notion of the immutable heavens. For at the time, it was almost universally accepted that the stars and planets were eternally unchanging. To suggest otherwise would not just challenge prevailing opinions, but also the theology of the day.

An engraving of Tycho observing the supernova, which appeared in the 1884 book Astronomie Populaire by Camille Flammarion.

And so the thinkers of the late 1500’s deemed the new star a “tailless comet”, a mere atmospheric effect. Comets in those days were thought to be combustions in the upper atmosphere, as were any unexpected dynamics in the night sky. Since the heavens were assumed to be changeless, the only possible explanation left was in the atmosphere. But Tycho realized that if this were true, then he should observe a parallax, a slight shift between dusk and dawn in the position of the nova with respect to the background stars, which depends on the distance between object and observer. Such a shift is observed for the Moon, so when Tycho found no parallax, he rightly concluded that the new star must be at least more distant than the Moon.

He also found that the object moved in perfect synchronization with the stars, and eventually decided that this was no atmospheric effect. Rather, it truly was a new star and a major upheaval in our understanding of the cosmos. As you might expect, this idea was not met with open minds, and thus we return to the insult in the preface of his book. A tame response from Tycho, though, who was a man willing to literally die defending the integrity of his ideas. He once lost much of his nose to a sword duel fought over the legitimacy of a mathematical formula. Admirable or foolhardy, you decide.

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Sunday Funnies: Interstellar Dust

Photos of cosmic dust after the jump.

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The bone-breaking Lammergeier: a truly awesome avian

Number 9 on my top ten animal countdown goes to the Lammergeier, a denizen of the high mountains in Europe, Africa, and the Himalayan region. German for “lamb vulture,” this enormous bird was so named for the belief that it preyed on domesticated animals. With upwards of a nine-foot wingspan, it’s not hard to imagine a Lammergeier flying off with even a small child, and in fact, they were once hunted in large numbers for this very fear. Of course, like in so many cases, our fears turned out to be baseless. We now know this silent giant, otherwise known as the Bearded Vulture, to be relatively harmless.

Despite the eagle-esque build, the Lammergeier, like all vultures, is mainly a scavenger. It belongs to a group of so-called “Old World” vultures, which are part of the same taxonomic family as hawks, eagles, and the other diurnal birds of prey. “New World” vultures, like the Turkey Vultures of America, have long been thought to comprise their own independent branch of the bird family tree. One of the main points in support of this is a stark contrast in how each group finds food. Old World vultures like the Lammergeier rely exclusively on sight, while their New World counterparts have evolved a keen sense of smell, something quite rare among birds. However, a recent and influential paper in the Journal Science has reshuffled a number of avian lineages in light DNA analyses, which included reclassifying the New World vultures into the same family as their raptor brethren, Accipitridae.

Just how far back vulture ancestry splits is still up for debate, but the apparent visual similarities between the two groups may still prove superficial, a result of a convergent evolution. This is the tendency for a set of advantageous traits to evolve independently in multiple lineages. For vultures of either world, having a sparsely feathered, or bald, head is a must to minimize contamination when tearing flesh from carcasses. The Lammergeier is a bit unusual among the vultures in that it does have a fair amount of cranial feathering. It is as if it evolved toward baldness and then came back the other way. Given what it has come to eat, this notion may not be too farfetched. When a carcass turns up, the Lammergeier is almost always last on the scene. It’s an animal that has dispensed with interspecies squabbles because it’s after something few others can eat: bones.

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Tuesday Time-Lapse: Icy Finger of Death

Here’s yet another first-to-film from the BBC Natural History Unit, the wizards that have consistently produced the world’s best nature programming for the last 50 years, including recent blockbusters like Planet Earth and Human Planet. The magnificence of the descending ice tendril juxtaposed with drama of the invertebrates’ plight, too slow to escape, make this scene perhaps even more spectacular than the similar sequence filmed for Life.

The new documentary series Frozen Planet hits American TV’s on March 18th. Discovery Channel was originally planning to air only 6 of the 7 episodes, as the last deals primarily with the threats facing our planet’s ecosystems from climate change and all too many Americans are hostile to the current scientific consensus. (Meanwhile, the clowns over at the Discovery Network have been working tirelessly to bring us quality science programming like Finding Bigfoot and 700 shows about how fishermen have dangerous jobs – I get it already!) Fortunately, somebody came to their senses, and Discovery has announced that they will indeed be airing all seven episodes.

Bbbut, it’s still narrated by Alec Baldwin. That’s just not okay with this nerd, so I’ve had the original BBC version on preorder from Amazon for almost a month now, which is narrated by the best in the business: David Attenborough. If you’ve had the displeasure of listening to Oprah’s version of Life, I think you might agree that it’ll be worth the extra month or so that I’ll have to wait to see it on Blu-ray.

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Orbiting Saturn: the Solar System’s most interesting planetary surroundings

First up on my top 10 favorite astronomical objects list, the ringed giant. Crown jewel of the backyard astronomer, Saturn’s rings were visible through the first telescope ever turned to the night sky and are often the target of choice when introducing new folks to small telescopes. One guy at an observing night I was helping with was so stunned by the view though a 16” scope that he was initially inclined to think we had played a trick on him with a sticker on the eyepiece!

Earth-Moon system from above image magnified.

Of course the best views these days are right here at your computer, beamed back by the Cassini probe from a minimum of 1.2 billion kilometers away. There is perhaps no more jaw-droppingly awesome image than the one above of Saturn perfectly backlit by the Sun in 2006. The rings lit up so spectacularly that whole new ones were discovered for the first time. And if that wasn’t enough, take a closer look at the little dot on the left, just above the bright main rings. That’s here. That’s home. Zoom in and you can even make out the Moon.

A model illustrating how the pattern of light and dark rings may develop in a tilted disk.

It’s their composition that makes the rings so dazzling – 99.9% good ol’ H2O. Despite being only about 50 billionths of Saturn’s mass, the ice crystals in the rings are spread out over such a massive surface area that they reflect a tremendous amount of sunlight. Alternating light and dark rings create the illusion of gaps, but there are only a few true breaks in the disk. The animation in the upper left shows how a uniform disk of material might develop into a “corrugated” pattern if it becomes a bit titled relative to Saturn’s equatorial plane.

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The delightfully abominable Yeti Crab

Kicking off my favorite fauna list at number ten is the Yeti Crab. Ghostly white and bristling with fine hairs, this species dwells in one of the most interesting habitats on the planet – the hydrothermal vent – and it is partly for this reason that I’m so fond of them. Hydrothermal vents are fissures in the earth’s surface that spew superheated water rich with chemicals dredged up from the beneath the ocean floor.

Hydrothermal Vent from ALVIN

Hydrothermal vent from the cockpit of the Alvin submersible.

Heated by magma below and compressed by over a mile of water above, this variety of H2O is supercritical, brought past the point where distinct liquid and gaseous phases exist. Direct contact with a fluid like this would instantly shatter the glass cockpit of even the sturdiest marine submersible, and if that wasn’t enough of a deterrent to life, hydrothermal vents fill the surrounding waters with toxic chemicals like hydrogen sulfide.

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