Stellar slingshot

Sometimes there's a scientific discovery that's just such an "oh, wow!" that I have to tell you about it.

Like the research that I ran into in the Astrophysical Journal recently.  "Origin of a Massive Hyper-runaway Subgiant Star LAMOST-HVS1: Implication from Gaia and Follow-up Spectroscopy," by Kohei Hattori, Monica Valluri, Norberto Castro, Ian U. Roederer, Guillaume Mahler, and Gourav Khullar, of the University of Michigan - Ann Arbor, describes a star that was ejected from our galaxy at a speed that boggles the imagination.

This star -- the euphoniously-named LAMOST-HVS1 -- is traveling at about 570 kilometers per second, on a trajectory almost perpendicular to the plane of the Milky Way Galaxy.  (If it helps, that's over a million miles an hour.)  It was initially thought that the star might have been evicted from the center of the galaxy, where there is an enormous black hole -- only something that massive, scientists thought, could impart enough energy to a star to get it traveling that fast. But tracking its path backward showed that it didn't come from the center, but from a region called the Norma Spiral Arm.

[Image is in the Public Domain, courtesy of NASA/JPL]

What this seems to indicate is that there are massive black holes scattered throughout the galaxy, not concentrated at the center.  Which is vaguely terrifying.  The scenario is apparently that a binary star was drawn in toward the black hole, and as it fell toward the event horizon, one of the two gained enough energy to be flung free -- what's called the "gravitational slingshot effect."  This phenomenon has been used to get countless television and movie spacefarers out of sticky situations, most notably in the 1998 film Lost in Space, wherein we learn that something being a truly awful television show is not sufficient to stop producers from turning it into an even worse movie.  I say "worse," even though the 1960s Lost in Space television show was uncategorically abysmal, because the movie took itself so damn seriously.  When the television show brought out space vikings or space cowboys or space hippies or a space motorcycle gang -- none of which, by the way, I'm making up -- at least they knew they were being campy.

But here, we're actually supposed to believe the intrepid crew of the Jupiter 2, having just escaped from Gary Oldman as a Dr. Smith who has turned into a giant humanoid spider (for the record, I'm not making that up, either), realizes that they don't have enough oomph to escape from the planet that's disintegrating around them, so Matt LeBlanc as Major Don West decides to use the "gravity well" of the planet to fling them free.  So he puts the Jupiter 2 into a power dive, and somehow they go all they way through the planet, miraculously dodging all of the rocks and debris, not to mention an entire mantle and core's worth of molten lava, and get squirted out of the other side like someone spitting out a grapefruit pit.

But I digress.

In any case, the writers of the script actually were referencing a real phenomenon, but one which would be unlikely to save you if you are ever in the situation of having your spaceship run out of gas while trying to escape from an exploding planet.  "This discovery dramatically changes our view on the origin of fast-moving stars," said study co-author Monica Valluri, in a press release.  "The fact that the trajectory of this massive fast-moving star originates in the disk rather that at the Galactic center indicates that the very extreme environments needed to eject fast-moving stars can arise in places other than around supermassive black holes."  (The press release also has a nice gif showing the star's path, which you should all check out.)

All of which is pretty cool, especially since there have only been around thirty of these "hyper-runaway" stars ever observed.  Given its current position, it's interesting to think about what the sky would look like to a denizen of one of its planets (yes, I know, any denizens it may have had surely wouldn't have survived a close encounter with a black hole, but just bear with me here).  I'm reminded of Carl Sagan's comment about a star in that position experiencing not a sunrise but a galaxy-rise -- from where it is, the disc and arms of the Milky Way would fill the entire night sky.

So there's some awe-inspiring research from the astronomers.  I don't see how anyone would not find this astonishing.  Maybe if you were like the Robinson family, meeting hordes of aliens every week, you'd get inured, but I can't help but think I'd still be pretty blown away even so.

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Dark arrow

The more we find out about how the universe works, the weirder it gets.

We've come a long way from Isaac Newton's vision of a mechanistic "clockwork cosmos" -- where everything is governed by a handful of simple mathematical laws, and where if you knew the mass, velocity, and acceleration of every particle in the universe, you could backtrack that knowledge and find out everything that had happened in the past, or extrapolate it and figure out everything that will happen in the future.  The one-two punch of relativity and quantum mechanics put paid to that idea; because of phenomena like nonlocality, entanglement, quantum indeterminacy, and the Heisenberg Uncertainty Principle, it turns out that this isn't even theoretically possible.

But the weirdness doesn't end there, and every time it looks like we're getting closer to a Theory of Everything, after which all that'll be left is filling in the details, we find something else that doesn't fit with what we know, that requires us to modify our understanding.  The latest is the discovery of dark matter and dark energy, which together far outweigh the mass of the entire universe's collection of ordinary matter and energy by a significant margin.  We don't know what either of those are, how (or if) they interact with ordinary matter other than gravitationally, and what abstruse laws of physics might govern their properties.  In other words, we know virtually nothing about them at all.  All we see is the gravitational pull they exert on the matter around them, like a shadow somehow cast by an otherwise-invisible figure standing near you.

Astrophysicists recently got another piece of the puzzle, and the discovery was presented at last week's annual meeting of the American Astronomical Society.  After analysis of a stream of stars in our own galaxy, astronomer Ana Bonaca of the Harvard-Smithsonian Center for Astrophysics found evidence that its movement had been altered by a "close encounter with a massive and dense perturber" -- meaning that a clump of dark matter swept through it, creating a slingshot effect that altered the stars' trajectories and flung them out of the stream.

The most amazing part is the size and speed of this dark arrow that shot its way through our galaxy.  According to Bonaca's data, the dark matter blob was equivalent to five million solar masses, and was traveling at 800,000 kilometers per hour.  No wonder it disrupted things.  But despite this, Bonaca calls this clump "slow-moving" -- which seems ridiculous until you recall that light travels at 300,000 kilometers per second.  So as fast as Bonaca's stream disrupter was moving, it was still only traveling at 1/1350 of the speed of light.

"Only."

Bonaca admits that there could have been other causes than dark matter, but still thinks that her explanation is the most plausible.  "Any massive and dense object orbiting in the halo could be the perturber," she said, "so a wandering supermassive black hole is definitely a possibility... The most plausible explanation for the gap-and-spur structure is an encounter with a dark matter substructure, like those predicted to populate galactic halos."

[Image is the Public Domain, courtesy of NASA/JPL]

If true, this indicates a few interesting things -- the first of which is that dark matter interacts with itself strongly enough to form clumps.  What those interactions consist of is completely unknown.  But the coolest thing is how these disruptions in stellar streams could be used as a dark matter telescope -- helping us to "see" what is invisible in every other respect.  most excitingly, these features demonstrate that cold stellar streams are extremely fine-tuned detectors, sensitive at a level that was only hoped for beforehand," Bonaca and her co-authors, David Hogg, Adrian Price-Whelan, and Charlie Conroy, write in a pre-print of their paper.  "In addition to GD-1 [the stellar stream they studied], there are over forty known streams in the Milky Way halo.  In the era of Gaia, we now have both the incentive and the resources to study them all in detail.  With the full network of streams we could learn not only about individual halo substructures, but about the population as a whole."

So this has definitely given the astrophysicists something to chew on.  I still have the feeling that dark matter will turn out to be this century's "luminiferous ether," the hypothesized substance through which light supposedly propagates -- and which was conclusively shown not to exist when Einstein published his paper on the Special Theory of Relativity.  But that's only a hunch, and I'm certainly not an expert.  We'll have to wait to see what the scientists come up with, and whatever that is, I can guarantee it's gonna be interesting.

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This week's Skeptophilia book recommendation is a little on the dark side; Jared Diamond's riveting book Collapse: How Societies Choose to Fail or Succeed.  Starting with societies that sowed the seeds of their own destruction -- such as the Easter Islanders, whose denuding of the landscape led to island-wide ecological collapse -- he focuses the lens on the United States and western Europe, whose rampant resource use, apparent disregard for curbing pollution, and choice of short-term expediency over long-term wisdom seem to be pushing us in the direction of disaster.

It's not a cheerful book, but it's a very necessary one, and is even more pertinent now than when it was written in 2005.  Diamond highlights the problems we face, and warns of that threshold we're approaching toward catastrophe -- a threshold that is so subtle that we may well not notice it until it's too late to reverse course.

[If you purchase this book using the image/link below, part of the proceeds goes to support Skeptophilia!]

Stellar slingshot

Sometimes there's a scientific discovery that's just such an "oh, wow!" that I have to tell you about it.

Like the research that was published in the Astrophysical Journal last week.  "Origin of a Massive Hyper-runaway Subgiant Star LAMOST-HVS1: Implication from Gaia and Follow-up Spectroscopy," by Kohei Hattori, Monica Valluri, Norberto Castro, Ian U. Roederer, Guillaume Mahler, and Gourav Khullar, of the University of Michigan - Ann Arbor, describes a star that was ejected from our galaxy at a speed that boggles the imagination.

This star -- the euphoniously-named LAMOST-HVS1 -- is traveling at about 570 kilometers per second, on a trajectory almost perpendicular to the plane of the Milky Way Galaxy.  (If it helps, that's over a million miles an hour.)  It was initially thought that the star might have been evicted from the center of the galaxy, where there is an enormous black hole -- only something that massive, scientists thought, could impart enough energy to a star to get it traveling that fast.  But tracking its path backward showed that it didn't come from the center, but from a region called the Norma Spiral Arm.

[Image is in the Public Domain, courtesy of NASA/JPL]

What this seems to indicate is that there are massive black holes scattered throughout the galaxy, not concentrated at the center.  Which is vaguely terrifying.  The scenario is apparently that a binary star was drawn in toward the black hole, and as it fell toward the event horizon, one of the two gained enough energy to be flung free -- what's called the "gravitational slingshot effect."  This phenomenon has been used to get countless television and movie spacefarers out of sticky situations, most notably in the 1998 film Lost in Space, wherein we learn that something being a truly awful television show is not sufficient to stop producers from turning it into an even worse movie.  I say "worse," even though Lost in Space was uncategorically abysmal, because the movie took itself so damn seriously.  When the television show brought out space vikings or space cowboys or space hippies or a space motorcycle gang -- none of which, by the way, I'm making up -- at least they knew they were being campy.

But here, we're actually supposed to believe the intrepid crew of the Jupiter 2, having just escaped from Gary Oldman as a Dr. Smith who has turned into a giant humanoid spider (for the record, I'm not making that up, either), realizes that they don't have enough oomph to escape from the planet that's disintegrating around them, so Matt LeBlanc as Major Don West decides to use the "gravity well" of the planet to fling them free.  So he puts the Jupiter 2 into a power dive, and somehow they go all they way through the planet, miraculously dodging all of the rocks and debris, not to mention an entire mantle and core's worth of molten lava, and get squirted out of the other side like someone spitting out a grapefruit pit.

But I digress.

In any case, the writers of the script actually were referencing a real phenomenon, but one which would be unlikely to save you if you are ever in the situation of having your spaceship run out of gas while trying to escape from an exploding planet.  "This discovery dramatically changes our view on the origin of fast-moving stars," said study co-author Monica Valluri, in a press release.  "The fact that the trajectory of this massive fast-moving star originates in the disk rather that at the Galactic center indicates that the very extreme environments needed to eject fast-moving stars can arise in places other than around supermassive black holes."  (The press release also has a nice gif showing the star's path, which you should all check out.)

All of which is pretty cool, especially since there have only been around thirty of these "hyper-runaway" stars ever observed.  Given its current position, it's interesting to think about what the sky would look like to a denizen of one of its planets (yes, I know, any denizens it may have had surely wouldn't have survived a close encounter with a black hole, but just bear with me here).  I'm reminded of Carl Sagan's comment about a star in that position experiencing not a sunrise but a galaxy-rise -- from where it is, the disc and arms of the Milky Way would fill the entire night sky.

So there's some awe-inspiring research from the astronomers.  I don't see how anyone would not find this astonishing.  Maybe if you were like the Robinson family, meeting hordes of aliens every week, you'd get inured, but I can't help but think I'd still be pretty blown away even so.

**************************************

This week's Skeptophilia book recommendation is an entertaining one -- Bad Astronomy by astronomer and blogger Phil Plait.  Covering everything from Moon landing "hoax" claims to astrology, Plait takes a look at how credulity and wishful thinking have given rise to loony ideas about the universe we live in, and how those ideas simply refuse to die.

Along the way, Plait makes sure to teach some good astronomy, explaining why you can't hear sounds in space, why stars twinkle but planets don't, and how we've used indirect evidence to create a persuasive explanation for how the universe began.  His lucid style is both informative and entertaining, and although you'll sometimes laugh at how goofy the human race can be, you'll come away impressed by how much we've figured out.

[If you purchase the book from Amazon using the image/link below, part of the proceeds goes to supporting Skeptophilia!]