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October 15, 2019

Look... up in the sky...

From Business Insider:

3.5 million years ago, the Milky Way's central black hole produced a massive explosion that sent cones of radiation (above) shooting through the galaxy and beyond, according to new research.

It was recent in galactic terms — ancient ancestors of modern humans walked the Earth at the time.

The explosion, likely caused by nuclear activity, was so powerful that it stretched to the Magellanic Stream, a cosmic river of gas clouds 200,000 light-years outside the Milky Way. 

A study analyzing the explosion's impacts on the Magellanic Stream was posted in the online repository arXiv, which publishes research that has not yet been peer-reviewed.

The study is awaiting publication in The Astrophysical Journal.

"These results dramatically change our understanding of the Milky Way," the study coauthor Magda Guglielmo said in a press release. "We always thought about our galaxy as an inactive galaxy, with a not-so-bright center. These new results instead open the possibility of a complete reinterpretation of its evolution and nature."

The team analyzed observations from NASA's Hubble Space Telescope to reveal that some clouds in the Magellanic Stream are highly ionized — something removed or added electrons from their molecules to give them an electric charge.

Those ionized clouds are a pivotal piece of evidence for the nuclear explosion that previous findings had only hinted at.

Satellites have detected bubbles of gamma- and X-ray radiation extending up to 50,000 light-years above and below the plane of the galaxy.

In 2013, scientists identified changes in the energy levels of hydrogen electrons along the part of the Magellanic Stream that's in-line with those radiation bubbles.

They could tentatively attribute those changes to activity in the galaxy's black hole, but this new finding makes the picture much more clear.

The explosion created two cones of radiation that shot through the Milky Way, expanding from a tiny point near the central black hole to impact a vast portion of the Magellanic Stream.

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A video (top) created by James Josephides shows the cones (purple) stretching beyond the Milky Way spiral to intersect the Magellanic Stream as it circles the galaxy.

"The flare must have been a bit like a lighthouse beam," Joss Bland-Hawthorn, an astronomer who led the research team, said in the release. "Imagine darkness, and then someone switches on a lighthouse beacon for a brief period of time."

The blast lasted about 300,000 years, the researchers estimated.

On cosmic timescales, that's a short explosion.

On a human timescale, it would have seemed like a permanent fixture in the sky.

At the time of the explosion, one of humans' longest-lived ancestors was spreading across Africa.

Australopithecus was a group of primate species that walked on two legs like us but still had the tiny brains characteristic of apes, and sported teeth somewhere in between.

The group encompassed Australopithecus afarensis, a species of early human that lived in East Africa and included the famously well-preserved fossil Lucy.

They might have noticed the galactic explosion looming overhead, but it likely had no effect on them.

"They may well have looked up towards Sagittarius and seen cones of light shooting sideways from the Milky Way, brighter than any star in the night sky," Bland-Hawthorn wrote in The Conversation. "The lightshow would have appeared as static beams on a human timescale, only flickering on timescales of thousands of years."

It's still unclear what exactly would have caused an explosion on such a huge scale.

How black holes evolve and influence their galaxies remains "an outstanding problem in astrophysics," the researchers said in their paper.

"We don't understand why this activity is intermittent, but it has something to do with how material gets dumped onto the black hole," Bland-Hawthorn wrote in The Conversation. "It might be like water droplets on a hot plate that sputter and explode chaotically, depending on their size."

In an effort to better understand the nature of that activity, the international team of researchers that took the first photograph of a black hole is turning its telescopes to the center of our galaxy.

The team plans to start releasing video footage of the Milky Way's black hole in the next five years.

October 15, 2019 at 04:01 PM | Permalink | Comments (0)

72 books to read before I die — Christopher Kimball

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The founder of Cook's Illustrated wrote, "I love books but I am running out of time."

He was 63 when he published his list as an editorial in the July & August 2014 issue of Cook's Illustrated.

He subdivided his list into three sections: books never read (50); books never finished (8); books I want to reread (14).

October 15, 2019 at 02:01 PM | Permalink | Comments (0)

The Pleasure Principle (Portrait of Edward James) — René Magritte

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Oil on canvas; 31" x 25";' 1937; West Dean House (Edward James Foundation), Sussex, U.K.

October 15, 2019 at 12:01 PM | Permalink | Comments (1)

Experts' Experts: Assessing Artichokes

From Cook's Illustrated:

When selecting fresh artichokes at the market, examine the leaves for some clues that will help you pick the best specimens.

The leaves should look tight, compact, and bright green; they should not appear dried out or feathery at the edges.

If you give the artichoke a squeeze, its leaves should squeak as they rub together (evidence that the artichoke still possesses much of its moisture).

And while we don't advocate abusing the produce in the store, the leaves should also snap off cleanly; if they bend, the artichoke is old.

October 15, 2019 at 10:01 AM | Permalink | Comments (1)

Never trust an atom. They make up everything.

71avdi1DYrL._SL1500_

$13.50.

October 15, 2019 at 08:01 AM | Permalink | Comments (0)

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