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Astronomers spy an iron planet stripped of its crust around a burned-out star
- dctoedt 8y agoThe last grafs bring to mind Arthur C. Clarke's Hugo-winning 1955 short story The Star. [0] [0] https://en.wikipedia.org/wiki/The_Star_(Clarke_short_story) https://en.wikipedia.org/wiki/The_Star_(Clarke_short_story)
- arethuza 8y agoIt reminded me of the meeting location at the start of The Hydrogen Sonata by Iain M. Banks. [I seem to remember it was a sliver of a planet held around an exploding star used as a meeting location - largely because doing that kind of thing is cool if you are godlike AIs].
- arethuza 8y ago"The two craft met within the blast-shadow of the planetary fragment called Ablate, a narrow twisted scrue of rock three thousand kilometres long and shaped like the hole in a tornado." https://www.orbitbooks.net/orbit-excerpts/the-hydrogen-sonata/ https://www.orbitbooks.net/orbit-excerpts/the-hydrogen-sonat...
- piker 8y agoAvailable here: https://sites.uni.edu/morgans/astro/course/TheStar.pdf https://sites.uni.edu/morgans/astro/course/TheStar.pdf
- booleandilemma 8y agoAn artist’s impression... Damn it!
- scandinavegan 8y agoI've been reading about space to my six-year old and there are a lot of neat real photographs of the solar system. Then we followed it up with a book on dinosaurs where he proclaimed "That's a drawing!"
- super_mario 8y agoIt's just a rendering artifact (a glitch if you will) in the simulation. Nothing to worry about.
- timdiggerm 8y agoWhat? Why even say this?
- super_mario 8y agoI guess Hacker News community doesn't like jokes.
- srcmap 8y ago"I felt a great disturbance in the Force, as if millions of voices suddenly cried out in terror and were suddenly silenced. I fear something terrible has happened." ―Obi-Wan Kenobi,
- SiempreViernes 8y agoArticle that isn't sullied by an infection of a clickbait title: www.sciencemag.org/news/2019/04/astronomers-spy-iron-planet-stripped-its-crust-around-burned-out-star
- lugg 8y agohttp://www.sciencemag.org/news/2019/04/astronomers-spy-iron-planet-stripped-its-crust-around-burned-out-star http://www.sciencemag.org/news/2019/04/astronomers-spy-iron-...
- e40 8y agoHTTPS version https://www.sciencemag.org/news/2019/04/astronomers-spy-iron-planet-stripped-its-crust-around-burned-out-star https://www.sciencemag.org/news/2019/04/astronomers-spy-iron...
- floatingatoll 8y agoI emailed a link to this comment to the mods using the Contact link in the footer so that they see your comment and edit the post to be better.
- dang 8y agoOK, we've changed to that from https://www.nytimes.com/2019/04/04/science/white-dwarf-fragment.html https://www.nytimes.com/2019/04/04/science/white-dwarf-fragm....
- toddh 8y agoThe title is wonderful. Poetic. It's hard not to imagine a mind drifting into reverie on reading it.
- binaryapparatus 8y ago"Nidavellir is real? Seriously? I mean, that place is a legend. They make the most powerful, horrific weapons to ever torment the universe. I would very much like to go there, please."
- ericol 8y ago> It collapses into a small and dense white dwarf, which cools over trillions of years. Its intense gravity can rip apart any surviving planets that stray too close How is the gravity from the white dwarf different from the previous state (red giants) of the star? Doen't they have basically the same mass? (Actually less, as they burn)
- jvanderbot 8y ago"stray" implies they get closer, eventually coming close enough for tidal effects to get nasty. Everything I understand agrees with a white dwarf not ripping apart planets whose orbits are not distirbed from their previous ones. IANA astronomer/astrophysicist.
- dexen 8y agoTo expand on @jvanderbot excellent reply, there's "Roche Limit" [1] - region of space close to massive bodies where gravitation gradient will break up the orbiting body. Given that white dwarfs remain in the cool-down phase for trillions of years, any orbiting body's orbit will slowly decay and eventually it ends up inside the Roche limit. [1] https://en.wikipedia.org/wiki/Roche_limit https://en.wikipedia.org/wiki/Roche_limit
- Rooster61 8y agoIt's a question of density and tidal forces. The red giant has that mass spread out across a much larger space, so the object that is "straying" has a much more uniform gradient of gravitational attraction across its mass than the white dwarf. An object can only be close to a very small part of the red giant at a time, while an object getting close to a white dwarf is subjected to much more of the gravity well all at once. That makes the gravitational gradient much more pronounced across the object, which means tidal forces are much stronger and more likely to rip the object apart. A good way to think about it is by looking at where the Roche limit exists for a mass of that size. Since the red giant is much larger but has roughly the same mass as the white dwarf, the Roche limit probably exists somewhere behind the surface, while the same orbit would extend far past the surface of the white dwarf. Let's say we have an orbital body around a giant star whose mass dictates that its Roche limit is 0.1AU, and then lets say that the star's diameter is 0.3AU. The object could never get close enough to the star to break apart. Now, that same star collapses while losing a negligible amount of mass, and now is a white dwarf with a diameter of 0.01AU. The object could now approach close enough that it gets pulled apart by tidal forces since its unimpeded by the stars surface all the way down to 0.1AU. https://en.wikipedia.org/wiki/Roche_limit https://en.wikipedia.org/wiki/Roche_limit EDIT: After reading, I realized that I unnecessarily introduced a non-astronomical term in gravitational gradient when I could have just said tidal force. It's the same thing. My apologies to any sticklers out there :)