![contemplatingmadness:
The North Star, a celestial beacon to navigators for centuries, may be slowly shrinking, according to a new analysis of more than 160 years of observations. The data suggest that the familiar fixture in the northern sky is shedding an Earth’s mass worth of gas each year. Some researchers caution, however, that the conclusion depends on certain assumptions about exactly where the star is in its several-billion-year life cycle.
Also known as Polaris, the North Star always sits over the North Pole because it is aligned with Earth’s axis. Find it in the night sky, at the end of the Little Dipper’s handle, and you don’t need a compass to orient yourself. To weigh Polaris, astrophysicist Hilding Neilson of the University of Bonn in Germany and colleagues essentially took its pulse. The star grows dimmer and brighter over a roughly 4-day cycle, and the team studied variation in the length of that cycle. Like all stars, Polaris is made of gas in layers around a core, where nuclear fusion occurs. As its gravity pulls the outermost gas inward, Polaris develops an opaque layer just under the surface that doesn’t let light through easily, dimming its glow. Light then builds up beneath this layer and pushes on it like water vapor boiling up under the lid on a saucepan. That light heats the opaque layer, causing it to expand and making it more transparent. The star becomes bigger and brighter until those outer layers of gas fall inward again and the cycle begins anew.
Even that 4-day pulsation isn’t constant: In 1844, it was about 12 minutes slower than it is now. Previously, astronomer David Turner of St. Mary’s University in Halifax, Canada, who was not involved in the new analysis, and colleagues compiled an archive including historical measurements of the pulse. Their data set ended in 2004. Neilson and collaborators, including two citizen astronomers, have now added their own observations from the past decade. This long record, from 1844 to the present, shows that the pulse of Polaris runs about 4.5 seconds slower every year.
The changing rate suggests that the structure of the star is evolving. If, as Neilson and collaborators assume, Polaris is an older star that is fusing or “burning” helium nuclei in its core, then its pulse is decreasing too quickly to match the standard model for stellar evolution. “Only if the star is losing a lot of mass can that [discrepancy] be resolved,” Neilson says. This mass may leave Polaris’s surface in waves, pushed outward as the pent-up light bursts through the opaque layer, and the loss would slow down the star’s pulse rate. To account for the relatively lethargic pulse, Polaris must be losing nearly the equivalent of Earth’s mass—or a little under a millionth of its own mass—each year, the team reports in the 1 February issue of The Astrophysical Journal Letters. But never fear, Neilson doesn’t think our beacon is hurtling toward oblivion. “Odds are [the mass loss] is episodic,” he says.
Done deal? Maybe not, Turner says. The mass-loss argument hinges on the internal behavior of the pulsing star, and Neilson’s team assumes that its layers are moving out of sync—when the outer layers are falling in, the inner layers are pushing out and vice versa. Turner suspects that Polaris is pulsing in a simpler way, with both inner and outer layers moving in the same direction, a hypothesis that his team revived in 2005. In this picture, he says, the North Star’s changing pulse can fit the models without hemorrhaging mass because the star is in an earlier stage of its evolution—it’s not yet burning helium but is instead preparing to blow up as red giant when the core runs out of hydrogen. On the other hand, if Polaris pulses the way Neilson’s team describes it, then the North Star would be past the red giant stage and now burning helium in its core.
Polaris’s distance from Earth is the key to figuring out which way it pulsates—and its place in stellar evolution. The more complicated pulse would mean that Polaris shines brighter in absolute terms, so to match its observed brightness in the sky, it would have to be farther away than if the pulse was simple. The Hubble telescope should be able to determine whether the North Star is closer to 325 light-years away, supporting Turner’s case, or 425 light-years away, supporting Neilson’s. “There are many mysteries about Polaris that defy simple explanation,” Turner says. “I think I will sit on the fence in this case and await further observational results.”](http://25.media.tumblr.com/tumblr_lyh0u7JHBy1qcyo2po1_250.jpg)
The North Star, a celestial beacon to navigators for centuries, may be slowly shrinking, according to a new analysis of more than 160 years of observations. The data suggest that the familiar fixture in the northern sky is shedding an Earth’s mass worth of gas each year. Some researchers caution, however, that the conclusion depends on certain assumptions about exactly where the star is in its several-billion-year life cycle.
Also known as Polaris, the North Star always sits over the North Pole because it is aligned with Earth’s axis. Find it in the night sky, at the end of the Little Dipper’s handle, and you don’t need a compass to orient yourself. To weigh Polaris, astrophysicist Hilding Neilson of the University of Bonn in Germany and colleagues essentially took its pulse. The star grows dimmer and brighter over a roughly 4-day cycle, and the team studied variation in the length of that cycle. Like all stars, Polaris is made of gas in layers around a core, where nuclear fusion occurs. As its gravity pulls the outermost gas inward, Polaris develops an opaque layer just under the surface that doesn’t let light through easily, dimming its glow. Light then builds up beneath this layer and pushes on it like water vapor boiling up under the lid on a saucepan. That light heats the opaque layer, causing it to expand and making it more transparent. The star becomes bigger and brighter until those outer layers of gas fall inward again and the cycle begins anew.
Even that 4-day pulsation isn’t constant: In 1844, it was about 12 minutes slower than it is now. Previously, astronomer David Turner of St. Mary’s University in Halifax, Canada, who was not involved in the new analysis, and colleagues compiled an archive including historical measurements of the pulse. Their data set ended in 2004. Neilson and collaborators, including two citizen astronomers, have now added their own observations from the past decade. This long record, from 1844 to the present, shows that the pulse of Polaris runs about 4.5 seconds slower every year.
The changing rate suggests that the structure of the star is evolving. If, as Neilson and collaborators assume, Polaris is an older star that is fusing or “burning” helium nuclei in its core, then its pulse is decreasing too quickly to match the standard model for stellar evolution. “Only if the star is losing a lot of mass can that [discrepancy] be resolved,” Neilson says. This mass may leave Polaris’s surface in waves, pushed outward as the pent-up light bursts through the opaque layer, and the loss would slow down the star’s pulse rate. To account for the relatively lethargic pulse, Polaris must be losing nearly the equivalent of Earth’s mass—or a little under a millionth of its own mass—each year, the team reports in the 1 February issue of The Astrophysical Journal Letters. But never fear, Neilson doesn’t think our beacon is hurtling toward oblivion. “Odds are [the mass loss] is episodic,” he says.
Done deal? Maybe not, Turner says. The mass-loss argument hinges on the internal behavior of the pulsing star, and Neilson’s team assumes that its layers are moving out of sync—when the outer layers are falling in, the inner layers are pushing out and vice versa. Turner suspects that Polaris is pulsing in a simpler way, with both inner and outer layers moving in the same direction, a hypothesis that his team revived in 2005. In this picture, he says, the North Star’s changing pulse can fit the models without hemorrhaging mass because the star is in an earlier stage of its evolution—it’s not yet burning helium but is instead preparing to blow up as red giant when the core runs out of hydrogen. On the other hand, if Polaris pulses the way Neilson’s team describes it, then the North Star would be past the red giant stage and now burning helium in its core.
Polaris’s distance from Earth is the key to figuring out which way it pulsates—and its place in stellar evolution. The more complicated pulse would mean that Polaris shines brighter in absolute terms, so to match its observed brightness in the sky, it would have to be farther away than if the pulse was simple. The Hubble telescope should be able to determine whether the North Star is closer to 325 light-years away, supporting Turner’s case, or 425 light-years away, supporting Neilson’s. “There are many mysteries about Polaris that defy simple explanation,” Turner says. “I think I will sit on the fence in this case and await further observational results.”
A small tribute to the Hubble Space Telescope (http://www.spacetelescope.org)
Music by David Schombert (http://www.jamendo.com/en/artist/david.schombert)
Hey, Who Ripped Open a Hole in the Universe?
This eerie patch of blackness in the middle of a busy star cluster may look like a rather misshapen black hole, but it’s actually something even stranger. It’s also quite possibly the loneliest, darkest, coldest place in the entire cosmos.
This is Barnard 68, and it’s what’s known as a dark molecular cloud. Basically, the dust and gas that makes up Barnard 68 is so tightly packed together that it blocks out all the light behind it. The result might look like some alien civilization tore apart the fabric of the universe and opening up a gateway to the howling void, but thankfully - or unfortunately, I guess, depending on how you feel about the howling void - it’s just gas. Make that a lot of gas.
Here’s some additional info on this particular patch of darkness:
‘With more than 62 vigintillion individual notes, “Mandala” is the longest palindrome in existence. Composed using the first nine partials of the Natural Harmonic Series repeating at the accelerated tempos of our solar system, Mandala would continue without repetition for over 532.25 septendecillion years. In homage to “Art of the Fugue” by J.S. Bach, “Mandala” has been crafted to include the “musical signature” of it’s author: the stereo imaging is arranged to reflect the exact position of the solar system at the moment of his birth, from the perspective of the Sun as it faces the constellation Libra, so that each note chronicles his birthday on every planet.
most amazing thing i have ever heard in my life.
NGC 3582
This fiery photo of the star-forming nebula NGC 3582 was processed by American astrophotographer Joe DePasquale.
“The massive loops of ionized gas expelled by dying stars remind me of solar prominences,” the bright loops of charged plasma that sometimes erupt on the sun, DePasquale said.
The data for the image was taken with the Wide Field Imager on the 2.2-meter telescope at the La Silla Observatory on June 16, 2002.
Image: ESO/Joe DePasquale
this is incredible. it’s hard to imagine how absolutely minuscule we are.
(Source: ktsaur)
beautiful-girlsallovertheworld:
My little sister means the world to me. She forces me to sit down whilst she paints my nails with her favorite colors, pink and purple. She asks me to sit outside and have a picnic with her. She watches me reblog on here and talk to my girlfriend most days, she asked me today to post a gif of us both so I did. She’s possibly the most bossy, annoying, noisy little sister you could have, but she’s amazing, in so many ways and beautiful, she’s almost 4 years old now, and is fighting leukemia. She’s becoming weak, so weak she is unable to go outside and have a picnic, or even paint nails. She’s still smiling though and laughing, like any other 3 year old. She’s going into hospital next week for treatment, if you could all pray for her, it would mean a lot to me, her and my family. She’s the best little sister you could really ask for.
aw
:( I would go crazy and die inside if anything happened to my sister. I am really sorry to hear that and I will make sure to pray for her.
(via strongskinnysuperior)
