Monicks: Unleashed

Tag: cometary globule

Astronomy Picture Of The Day | GRO J1655-40: Evidence for a Spinning Black Hole

GRO J1655-40: Evidence for a Spinning Black Hole
Credit: April Hobart, CXC

Explanation: In the center of a swirling whirlpool of hot gas is likely a beast that has never been seen directly: a black hole. Studies of the bright light emitted by the swirling gas frequently indicate not only that a black hole is present, but also likely attributes. The gas surrounding GRO J1655-40, for example, has been found to display an unusual flickering at a rate of 450 times a second. Given a previous mass estimate for the central object of seven times the mass of our Sun, the rate of the fast flickering can be explained by a black hole that is rotating very rapidly. What physical mechanisms actually cause the flickering — and a slower quasi-periodic oscillation (QPO) — in accretion disks surrounding black holes and neutron stars remains a topic of much research.

via antwrp.gsfc.nasa.gov

September 6, 2010
Astronomy Picture Of The Day | Hoags Object: A Strange Ring Galaxy

Hoag’s Object: A Strange Ring Galaxy
Credit: R. Lucas (STScI/AURA), Hubble Heritage Team, NASA

Explanation: Is this one galaxy or two? This question came to light in 1950 when astronomer Art Hoag chanced upon this unusual extragalactic object. On the outside is a ring dominated by bright blue stars, while near the center lies a ball of much redder stars that are likely much older. Between the two is a gap that appears almost completely dark. How Hoag’s Object formed remains unknown, although similar objects have now been identified and collectively labeled as a form of ring galaxy. Genesis hypotheses include a www.ipac.caltech.edu/level5/Struck/frames.html“>galaxy collision billions of years ago and the gravitational effect of a central bar that has since vanished. The above photo taken by the Hubble Space Telescope in July 2001 reveals unprecedented details of Hoag’s Object and may yield a www.ipac.caltech.edu/level5/Rings/Rings17_2.html“>better understanding. Hoag’s Object spans about 100,000 light years and lies about 600 million light years away toward the constellation of the Snake (Serpens). Coincidentally, visible in the gap (at about one o’clock) is yet another ring galaxy that likely lies far in the distance.

via antwrp.gsfc.nasa.gov

September 4, 2010
Astronomy Picture of the Day | M27: Not a Comet

M27: Not a Comet
Credit & Copyright: Matthew T. Russell

Explanation: While hunting for comets in the skies above 18th century France, astronomer Charles Messier diligently kept a list of the things he encountered that were definitely not comets. This is number 27 on his now famous not-a-comet list. In fact, 21st century astronomers would identify it as a planetary nebula, but it’s not a planet either, even though it may appear round and planet-like in a small telescope. Messier 27 (M27) is an excellent example of a gaseous emission nebula created as a sun-like star runs out of nuclear fuel in its core. The nebula forms as the star’s outer layers are expelled into space, with a visible glow generated by atoms excited by the dying star’s intense but invisible ultraviolet light. Known by the popular name of the Dumbbell Nebula, the beautifully symmetric interstellar gas cloud is over 2.5 light-years across and about 1,200 light-years away in the constellation Vulpecula. This impressive color composite highlights details within the well-studied central region and fainter, seldom imaged features in the nebula’s outer halo. It includes narrowband images recorded using filters sensitive to emission from oxygen atoms, shown in blue-green hues, and hydrogen atoms in red.

via antwrp.gsfc.nasa.gov

September 3, 2010