Hubble Discovers 'Planetary Graveyard' Around White Dwarf 26
astroengine send this interesting excerpt from Discovery: "The Hubble Space Telescope has discovered rocky remains of planetary material 'polluting' the atmospheres of two white dwarfs — a sign that these stars likely have (or had) planetary systems and that asteroids are currently being shredded by extreme tidal forces. Although white dwarfs with polluted atmospheres have been observed before, this is the first time evidence of planetary systems have been discovered in stars belonging to a relatively young cluster of stars. 'We have identified chemical evidence for the building blocks of rocky planets,' said Jay Farihi of the University of Cambridge in a Hubble news release. 'When these stars were born, they built planets, and there's a good chance that they currently retain some of them. The signs of rocky debris we are seeing are evidence of this — it is at least as rocky as the most primitive terrestrial bodies in our Solar System.'"
Re:don't get it (Score:4, Interesting)
It says a relatively young cluster of stars. That doesn't mean that some members of the cluster aren't old enough to have gone nova. Also, larger hotter stars (than the Sun) don't stay in the main sequence nearly as long, so it's possible that some were just under the threshold to become neutron stars. There is no contradiction there.
poor science reporting (Score:2, Interesting)
The article doesn't explain why there is rocky material close enough to the white dwarfs to be tidally ripped apart. It makes a brief comment about the extreme tidal stresses ripping apart anything orbiting it. But superdense objects don't exert stronger gravity for their mass than less dense objects. If the sun spontaneously magically became a white dwarf, or even a black hole, the earth would continue in its orbit unperturbed. The only thing that would cause a former planet of this white dwarf to be tidally ripped apart is if the star gained magical mass (which it wouldn't as a white dwarf has less mass than the star it used to be, as the rest is now in the planetary nebula), or if the planet survived the red giant stage and was somehow pulled in to a closer orbit in the white dwarf stage. I could imagine an earth like planet being enveloped in the hazy outer atmosphere of the expanding red giant, and the star's atmosphere causing enough drag to slow the planet down and fall to a lower orbit. But that requires a planet survive passing through a star's atmosphere without being incinerated right there and receiving just enough drag to fall to a lower orbit but not plunge into the heart of the star. That is all pretty amazing stuff if true, and the article mentions none of it - choosing rather to go down the bad science "it's denser so it must magically suck harder because that's how gravity really works" route.
Re:Too bad for any life (Score:4, Interesting)
that's probably the answer to the Fermi Paradox. For billions of years the earth had life, but only in the last few decades the technology that *might* have detected or made a signal to another star. In less than 350 million years, the earth will be too hot to support multicellular life due to expansion of the sun. what if every billion years or so an intelligent species arises within 10,000 light-years of any other place that has the same thing happen once at some random time over the life of the universe? they find themselves alone...