Galaxy Grows Monstrous X-Ray Tail

In a galactic cluster far, far away, a galaxy has grown an unprecedented tail of super-heated gases, providing astronomers with a unique glimpse of an extreme intragalactic environment.
Using the X-ray vision of NASA’s Chandra space telescope, the ghostly glow of a 250,000 light-year long tail has been seen streaming from a galaxy called  deep inside the Zwicky 8338 cluster nearly 700 million light-years from Earth. This tail, a stream of superheated interstellar gases, has been ripped from the galaxy as it interacts with the hotter intragalactic gases inside the cluster.
The temperature of the tail gases has been gauged at around 10 million degrees Kelvin (Celsius), whereas the intragalactic gases in Zwicky 8338 are 3 times hotter.
Of most interest is the gap between the tail and the galaxy, a possible indication that all the available star-forming gases inside the galaxy has been blown away and depleted.
“The large separation between the galaxy and the tail might be telling us that the gas has been completely stripped off the galaxy,” said Thomas Reiprich, University of Bonn in Germany. “In effect, the tail has been cut off from the galaxy.”
Astronomers speculate that the galaxy’s loss may be the cluster’s gain; this tail of gas, that extends over twice the width of our galaxy, could spawn an island of star formation all by itself. Infrared studies of CGCG254-021 have shown that there is very little active star formation underway, likely a symptom of the massive gas loss that formed the tail.
Other characteristics of the tail gases have been studied, including the higher concentration of heavier elements (than helium) in the “head” of the tail (the brighter, cooler blob nearest its parent galaxy). There’s also evidence of a bow shock leading the tail — both galaxy and tail are known to be traveling downward in this observation. The shock is generated by this supersonic motion through the cluster’s intragalactic medium.
“This tail is a vivid example of how dynamic galaxy clusters are, as we may be seeing the transformation of a galaxy as it moves through the cluster,” said Gerrit Schellenberger of the University of Bonn in Germany, who led the study that is published in the November edition of the journal Astronomy and Astrophysics. “Also, the material in the tail includes not only hydrogen but heavier elements, and could spawn a new generation of stars trailing behind the galaxy.”
Galaxy clusters are of huge interest as they are so massive. Often containing hundreds to thousands of individual galaxies, this vast structures are islands of intense gravitational dominance over space-time and known to be reservoirs of dark matter — the invisible stuff that makes up around 85 percent of all mass in the universe. By looking deep into these clusters we can better understand how individual galaxies evolve.
“Since galaxy clusters are so enormous, they play a critical role in understanding how our Universe evolves,” added Schellenberger. “To understand galaxy clusters we need to understand how their galaxies change with time, and these X-ray tails provide an important element.”

Dying sun caught tearing apart its own asteroids (Science)

The Kepler Space Telescope has detected disintegrating asteroids orbiting a white dwarf, the type of burned-out star our sun will become about 8 billion years from now. The discovery explains why some white dwarfs have heavy elements on their surfaces and also gives us a possible preview of Earth's grisly fate.
"It's really amazing," says Jay Holberg, an astronomer at the University of Arizona in Tucson, who was not involved in the discovery. "We've never seen this before for a white dwarf."
A typical white dwarf is nearly as massive as the sun but only slightly larger than Earth, so the star exerts a strong gravitational pull at its surface: Drop a rock from a height of 1 meter and it would hit the star at thousands of kilometers per hour. The strong gravitational force should also yank all elements heavier than helium beneath the star's surface, yet the surfaces of many white dwarfs nevertheless possess heavy elements, suggesting that asteroids deposit elements such as silicon and iron.
Now, for the first time, researchers have seen this scenario unfold. Andrew Vanderburg, an astronomer at the Harvard-Smithsonian Center for Astrophysics, was analyzing data from Kepler, which detects planets when they block the light of their sun. "One of the white dwarfs suddenly popped up with this really intriguing signature," Vanderburg says. As his team reports online today in Nature, the white dwarf, located in the constellation Virgo and named WD 1145+017, has at least one, and probably several, asteroids that are disintegrating. As a debris cloud from each asteroid passes between us and the star, Kepler detects a dimming of the star's light.
"It's fascinating," says astronomer Michael Jura of the University of California, Los Angeles, who was not part of the discovery team. "They've actually caught in the act the process of some asteroid breaking into pieces, being disrupted by the white dwarf host star."
Indeed, the star itself is the asteroids' enemy. Its gravity has torn them asunder, and its light is vaporizing their rock. The asteroids are so close to the star that they revolve in just 4.5 to 4.9 hours; Vanderburg estimates they are roughly the size of Ceres, the largest asteroid between the orbits of Mars and Jupiter.
Billions of years from now, our sun will expand into a red giant, engulfing and incinerating Mercury and possibly Venus and Earth. Then the red sun will eject its outer layers and expose its hot core, which will contract into a white dwarf. Even if the sun never engulfs Earth, the drama may destabilize orbits in the solar system so that asteroids crash into our world and grind it up. Thus, the newly discovered asteroids could conceivably be the wreckage of a planet that once resembled our own.