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The unique ringed entrance of the Wallace Emerson Community Centre--subject of an extended 2009 photo post of mine--is quite striking looking at it from the east side of Dufferin Street.
Aug. 31st, 2011
The unique ringed entrance of the Wallace Emerson Community Centre--subject of an extended 2009 photo post of mine--is quite striking looking at it from the east side of Dufferin Street.
The news that the bacterium Yersinia pestis has been identified as the cause of the Black Death of the 14th century impresses me for two reasons. The first is the subtlety of the study.
The second is the apparently very minor change it took for Yersinia pestis to become a mass killer.
Details matter. Clearly.
The researchers studied DNA from the remains of 109 skeletons, now more than 650 years old, that were buried in the East Smithfield grave outside London’s old walls during the plague.
Poinar and his team took bone and teeth samples to get a hold of whatever small bits of DNA they could find. They then used a unique technique to look for Yersinia pestis among the morass of viruses, bacteria and human genes.
The researchers launched a protein-laced fishing line into this genetic pool designed to attract Yersinia pestis. Once the bacterium attached itself to the fishing line, the researchers used magnets to separate it out so they could map its genetic makeup.
Poinar said his team was only able to pull a small amount of the bacterium’s genetic markers. In all, the genetic string reaches more than 4.6 million units and Poinar’s team was able to capture about 50 to 60 units.
The second is the apparently very minor change it took for Yersinia pestis to become a mass killer.
The differences between Yersinia pestis and its soil-based cousin are small, said Hendrik Poinar, one of the lead authors on the study from McMaster University in Hamilton.
The task now is to determine how a harmless microbe turned into a deadly killer and better prepare for a future pandemic, Poinar said.
“The question is, can we identify what made the pathogen so bad?”said Poinar, an evolutionary geneticist at McMaster’s Michael G. DeGroote Institute for Infectious Disease Research.
“That’s the million-dollar question and we don’t have an answer yet, but that’s what we’re targeting.”
The study also suggests that the Black Plague was one of three pandemics beginning with the Plague of Justinian in 541 AD and culminating with the modern bubonic plague that is driven by international travel and trade.
Yersinia pestis is responsible worldwide for the deaths of approximately 2,000 people annually from the bubonic plague, but it is not nearly as powerful as the Black Death. Poinar said that no outbreak has been as deadly as Black Death.
“We’ve been relatively disease free,” Poinar says. “We’ve had infections such as HIV/AIDS that have killed millions of people, but not to the same extent.”
Details matter. Clearly.
The youngest star in our stellar neighbourhood has been found! AP Columbae, 27 light years away, is apparently a mere 40 million years old, closer to us in time than the dinosaurs.
Proxima Centauri is the outermost star of the Alpha Centauri trinary, the two largest and most Sol-like stars of which are 4.3 light years away.
AP Columbae is an obscure star very much like Proxima Centauri, in fact, in being a comparatively low-mass star prone to flares. (The paired capital letters of "AP" is standard nomenclature for variable stars). They differ in that whereas Proxima Centauri is a mature star some five billion years old, AP Columbae is formally classified as a pre-main sequence star, a star that has moved past the phase of generating most of its energy through gravitational attraction but has not yet begun to generate energy consistently through nuclear fusion like mature stars. Listed as AP Columbae at Wolfram Alpha but found under the additional label of LP 949-15 at the SIMBAD database, the star is in the rough direction of Sirius and Canopus in the northern hemisphere, but can be viewed only with fairly powerful telescopes.
The team's paper can be read here at ArXiv. As co-author Murphy points out, besides the novelty value the discovery is useful for those astronomers searching for young planets, worlds which should still be glowing hot from their formation.
The star, called AP Columbae, is closer to Earth than previously thought and is around 40 million years old - a stellar newborn when compared to our own Sun which was created 4.6 billion years ago.
"The star has been known about and studied for the past 15 years, but it wasn't realised it was so young and so close, until now," says co-author Simon Murphy, a PhD student from the Australian National University in Canberra. He says that highly accurate measurements from telescopes in Coonabarabran, NSW, and Chile, Hawaii and California, allowed the international team to build a much better picture of the star.
AP Columbae is classed as a red-dwarf star because it is relatively small - about a third the size of the Sun - and comparatively cool, with a surface temperature of about 3500ºC as opposed to the Sun's 6000ºC.
To measure the distance of the young star to Earth was relatively simple, Simon told Australian Geographic. As the Earth moved around in its natural orbit, the team observed how the position of AP Columbae changed in relation to stars in the background. "It's similar to when you're in a car, and the trees you see on the side of the road move at a different rate to the mountains in the background, depending on how far away they are," he says. "So with enough observations you can tie down the distance to a nearby star very accurately. But measuring the age is a little more tricky."
To calculate the approximate age of AP Columbae, the team - which included scientists from Georgia State University and the University of California, San Diego - analysed the amount of lithium in the star's atmosphere. Stars are born with a high level of lithium, but this declines rapidly with age.
A distance of 27 light-years seems vast on a human scale, but on the scale of the stars it is a relatively short distance. The Milky Way itself spans 100,000 light-years from end-to-end, and our nearest neighbouring star of any age is Proxima Centauri, at just 4.2 light-years away.
Proxima Centauri is the outermost star of the Alpha Centauri trinary, the two largest and most Sol-like stars of which are 4.3 light years away.
AP Columbae is an obscure star very much like Proxima Centauri, in fact, in being a comparatively low-mass star prone to flares. (The paired capital letters of "AP" is standard nomenclature for variable stars). They differ in that whereas Proxima Centauri is a mature star some five billion years old, AP Columbae is formally classified as a pre-main sequence star, a star that has moved past the phase of generating most of its energy through gravitational attraction but has not yet begun to generate energy consistently through nuclear fusion like mature stars. Listed as AP Columbae at Wolfram Alpha but found under the additional label of LP 949-15 at the SIMBAD database, the star is in the rough direction of Sirius and Canopus in the northern hemisphere, but can be viewed only with fairly powerful telescopes.
The team's paper can be read here at ArXiv. As co-author Murphy points out, besides the novelty value the discovery is useful for those astronomers searching for young planets, worlds which should still be glowing hot from their formation.
The close proximity of AP Columbae makes it a prime candidate to hunt for orbiting gas giants, says Simon. "With any luck there'll be some newly formed planets around it...and [looking for them is] something we hope to do later in the year with telescopes in Chile."
If planets are found orbiting AP Columbae, it could help our understanding of how gas giants form. But it won't tell us much about Earth-like planets, says Simon, because they are too small to be spotted so far away.