Exploding stars whacked ancient Earth + Mars' methane burps pinpointed + H-R diagram

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Hertzsprung-Russell diagram: the most important graph in astrophysics

KEY POINTS: The invention of spectroscopy and photography converted astronomy into astrophysics. With these new tools, astrophysicists gathered untold amounts of data on stars. When these stars were plotted on a graph, amazing patterns emerged. (Hertzsprung–Russell diagram)

INTRO: Like people, stars are born, live, and then die. But how do scientists know that stars are born and die? Where did that knowledge come from? After all, for most of human history, many people thought that stars were eternal and unchanging. What was it that set astronomers on the path to seeing stars as something bound by time and change? The answer comes in the form of a simple and beautiful diagram first made 100 or so years ago... (MORE)

We may finally have the location of mysterious 'alien burps' detected on Mars

EXCERPTS: Methane blips have pinged on Curiosity's detection systems six times since the rover landed in Mars' Gale crater in 2012, but scientists weren't able to find a source for them. Now, with a new analysis, researchers may have traced the methane burps to their origin. [...] they were able to triangulate regions where the methane source is most likely located - with one being just a few dozen miles away from the rover.

"[The findings] point to an active emission region to the west and the southwest of the Curiosity rover on the northwestern crater floor," the researchers wrote in their paper. "This may invoke a coincidence that we selected a landing site for Curiosity that is located next to an active methane emission site."

This prospect is thrilling for scientists, as almost all of the methane in Earth's atmosphere has biological origins, according to the researchers, so that a signature on Mars could be a key signpost for finding life on the ostensibly desolate planet. Even if the methane is being produced by non-biological processes, it could point to geological activity closely tied to the presence of liquid water - a vital ingredient for past or present life to thrive... (MORE - details)

Exploding stars may have assaulted ancient Earth

INTRO: For our Australopithecus ancestors who roamed Africa 2.5 million years ago, the bright new star in the sky surely would have aroused curiosity. As luminous as the full Moon, it would have cast shadows at night and been visible during the day. As the supernova faded over the following months, it probably also faded from memory. But it left other traces, now coming to light.

Over the past 2 decades, researchers have found hundreds of radioactive atoms, trapped in seafloor minerals, that came from an ancient explosion marking the death of a nearby star. Its fusion fuel exhausted, the star had collapsed, generating a shock wave that blasted away its outer layers in an expanding ball of gas and dust so hot that it briefly glowed as bright as a galaxy—and ultimately showered Earth with those telltale atoms.

Erupting from hundreds of light-years away, the flash of x-rays and gamma rays probably did no harm on Earth. But the expanding fireball also accelerated cosmic rays—mostly nuclei of hydrogen and helium—to close to the speed of light. These projectiles arrived stealthily, decades later, ramping up into an invisible fusillade that could have lasted for thousands of years and might have affected the atmosphere—and life.

In a flurry of studies and speculation, astronomers have sketched out their potential effects. A cosmic ray barrage might have boosted mutation rates by eroding Earth’s protective ozone layer and generating showers of secondary, tissue-penetrating particles. Tearing through the atmosphere, the particles would have also created pathways for lightning, perhaps kindling a spate of wildfires.

At the same time, atmospheric reactions triggered by the radiation could have led to a rain of nitrogen compounds, which would have fertilized plants, drawing down carbon dioxide. In that way, the celestial event could have cooled the climate and helped initiate the ice ages 2.5 million years ago, at the start of the Pleistocene epoch. Even taken together, the effects are “not like the dinosaur extinction event—it’s more subtle and local,” says Brian Thomas, an astronomer at Washburn University who has studied the earthly effects of cosmic catastrophes for nearly 2 decades.

Few astronomers are suggesting that the supernovae caused any great extinction at the time, and even fewer paleontologists are ready to believe them. “Death from space is always really cool,” says Pincelli Hull, a paleontologist at Yale University. “The evidence is interesting but has not quite really reached the threshold to incorporate into my mental register.”

Yet the supernova hunters believe other blasts, more distant in time, went off closer to Earth. And they think these supernovae could explain some extinction events that lack customary triggers such as volcanic outbursts or asteroid impacts. Adrian Melott, an astronomer at the University of Kansas, Lawrence, who explores how nearby cosmic cataclysms might affect Earth, says it’s time to more carefully probe Earth’s history for ancient supernova strikes. Not only will that help astrophysicists understand how the blasts shaped the neighborhood of the Solar System and seeded it with heavy elements, but it could also give paleontologists a new way to think about bouts of global change. “This is new and unfamiliar,” Melott says. “It will take time to be accepted.”

Astronomers believe a few supernovae go off in the Milky Way every century. By the law of averages, a handful must have exploded very close to Earth—within 30 light-years—during its 4.5-billion-year lifetime, with potentially catastrophic effects. Even blasts as far as 300 light-years away should leave traces in the form of specks of dust blown out in the shell of debris known as a supernova remnant... (MORE)

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