View Single Post
curiousuburb
Antimatter Man
 
Join Date: May 2004
Location: that interweb thing
 
2011-11-08, 10:49

Today's Coolness: Spiral Stars, Progress plasmic reentry, and Near miss Asteroid tonight ... as always, click pics for teh big

---

Not all stars are spherical, apparently.

Quote:
Researchers using the Subaru telescope in Hawaii have found a star with spiral arms.

Two spiral arms emerge from the gas-rich disk around SAO 206462, a young star in the constellation Lupus. This image, acquired by the Subaru Telescope and its HiCIAO instrument, is the first to show spiral arms in a circumstellar disk. The disk itself is some 14 billion miles across, or about twice the size of Pluto's orbit in our own solar system. (Credit: NAOJ/Subaru) [larger image]
The name of the star is SAO 206462. It's a young star more than four hundred light years from Earth in the constellation Lupus, the wolf. SAO 206462 attracted attention because it has a circumstellar disk--that is, a broad disk of dust and gas surrounding the star. Researchers strongly suspected that new planets might be coalescing inside the disk, which is about twice as wide as the orbit of Pluto.

When they took a closer look at SAO 206462 they found not planets, but arms. Astronomers have seen spiral arms before: they’re commonly found in pinwheel galaxies where hundreds of millions of stars spiral together around a common core. Finding a clear case of spiral arms around an individual star, however, is unprecedented *1.

The arms might be a sign that planets are forming within the disk.

"Detailed computer simulations have shown us that the gravitational pull of a planet inside a circumstellar disk can perturb gas and dust, creating spiral arms,” says Carol Grady, an astronomer with Eureka Scientific, Inc., who is based at NASA's Goddard Space Flight Center. “Now, for the first time, we're seeing these dynamical features."

... continues ... via NASA

*Footnote: (1) "There have been other examples of circumstellar disks imaged with partial spiral arms or blurry spiral arms," notes Marc Kuchner of Goddard, who organized the conference. "So it's not completely unprecedented. But this is really the first clear image of this phenomenon--clear enough that you could trace the arms and possibly use them to make quantitative inferences about what's causing them."
Nitpickers may argue it's technically the circumstellar disk with arms, but still...


---

Progress re-entry video from ISS
Quote:
Originally Posted by BadAstronomy

Holy wow! You can see the trail of plasma starting to blow off the main spacecraft just as the video begins, and if you look carefully you can see bigger chunks of material falling off the main body — just like in the big picture I posted earlier (seen below).


... continues on BadAstronomy


---

How to Spot today's asteroid near-miss (less than Earth-Moon distance)*

*valid for Western Europe and North America - clear skies required.

Quote:
Roll out the red carpet! Earth is about to be visited by the largest close-approaching asteroid on record. Known as 2005 YU55, it comes closest to us on November 8th at 23:28 Universal Time (6:28 p.m. EST), when it passes 198,000 miles (319,000 km) from Earth's surface — closer than the Moon's orbit.

This radar image of asteroid 2005 YU55 was generated from radar data taken on November 7, 2011, using NASA's giant radio dishes in California. At the time the asteroid was 860,000 miles (1,380,000 km) from Earth. Radar illumination is from the top, so only half of the asteroid is apparent.
NASA / JPL
Discovered nearly six years ago by Robert McMillan at Steward Observatory's Spacewatch Telescope in Arizona, 2005 YU55 has been this way before. In April 2010 it passed close enough for detailed radar probing by the giant radio dish at Arecibo, Puerto Rico.

The Arecibo observations showed this asteroidal emissary to be a quarter mile (400 m) across and remarkably round. Given its size and diminutive brightness, the object must be quite dark and thus likely carbon-rich. Its rotation period is relatively long, 18 to 20 hours.

In the grand scheme of things it's more micro-planet than minor planet, but we've never knowingly had something this big come this close before. Were it to strike Earth, 2005 YU55 would deliver a kinetic-energy punch equivalent to several thousand megatons of TNT. It's the kind of potential threat that outer-space sentries lose sleep over.

This animation shows the trajectory of asteroid 2005 YU55 as it cruises past Earth on the night of November 8-9, 2011.
NASA / JPL
But fear not: the Arecibo observations allowed dynamicists to recompute the big rock's orbit with enough accuracy to ensure that it won't strike Earth within the next 100 years. (That said, it will pass just 175,000 miles from Venus in 2029, close enough to alter its orbit slightly. This adds uncertainty to predictions for its next close encounter with Earth in 2041, when the minimum distance could be anywhere from 200,000 to 30 million miles.)


Best seen from North America, the little asteroid 2005 YU55 will race far across the constellations in just 11 hours. Click here for a more detailed chart and instructions.
Sky & Telescope illustration


... continues ... via Sky & Telescope
Damn clouds here... but for the rest of you...



All those who believe in telekinesis, raise my hand.

Last edited by curiousuburb : 2011-11-08 at 11:04. Reason: credits and links tweaked
  quote