Feb 08

DARK SPIRAL

 Decaying sunspot AR1667 erupted on Feb. 6th, producing a double-peaked C9-class solar flare that lasted more than ten hours from beginning to end. The slow explosion hurled a twisting, inky-dark plume of plasma into space. NASA’s Solar Dynamics Observatory recorded the spiral:

The darkness of the material is a sign that the plasma was dense and cool relative to the surrounding atmosphere of the sun. This isn’t the first time that the sun has produced a dark explosion. Since the launch of Solar Dynamics Observatory in 2010, researchers have catalogued many instances of cool plasma emerging from flare sites. “Cool” has a special meaning, however, on the sun. The temperature of the dark blobs is “only” about 20,000 K vs. 40,000 K to 1,000,000 K for the gas in the surrounding atmosphere.

Decaying sunspot AR1667 probably won’t erupt again. NOAA forecasters put the odds of a significant (M-class or stronger) flare today at 10% or less.

Source:SpaceWeather.com

Feb 07

Cygnus X-1: NASA’s Chandra Adds to Black Hole Birth Announcement

Cygnus X-1


  • Cygnus X-1 is a black hole about 15 times the mass of the Sun in orbit with a massive blue companion star.
  • Astronomers used several telescopes including Chandra to study Cygnus X-1.
  • The combined data have revealed the spin, mass, and distance of this black hole more precisely than ever before.
  • Stephen Hawking lost a bet – originally placed in 1974 — that Cygnus X-1 did not contain a black hole.


On the left, an optical image from the Digitized Sky Survey shows Cygnus X-1, outlined in a red box. Cygnus X-1 is located near large active regions of star formation in the Milky Way, as seen in this image that spans some 700 light years across. An artist’s illustration on the right depicts what astronomers think is happening within the Cygnus X-1 system. Cygnus X-1 is a so-called stellar-mass black hole, a class of black holes that comes from the collapse of a massive star. The black hole pulls material from a massive, blue companion star toward it. This material forms a disk (shown in red and orange) that rotates around the black hole before falling into it or being redirected away from the black hole in the form of powerful jets.

A trio of papers with data from radio, optical and X-ray telescopes, including NASA’s Chandra X-ray Observatory, has revealed new details about the birth of this famous black hole that took place millions of years ago. Using X-ray data from Chandra, the Rossi X-ray Timing Explorer, and the Advanced Satellite for Cosmology and Astrophysics, scientists were able to determine the spin of Cygnus X-1 with unprecedented accuracy, showing that the black hole is spinning at very close to its maximum rate. Its event horizon — the point of no return for material falling towards a black hole — is spinning around more than 800 times a second.

X-ray 
Chandra X-ray of Cygnus X-1.

Using optical observations of the companion star and its motion around its unseen companion, the team also made the most precise determination ever for the mass of Cygnus X-1, of 14.8 times the mass of the Sun. It was likely to have been almost this massive at birth, because of lack of time for it to grow appreciably.

The researchers also announced that they have made the most accurate distance estimate yet of Cygnus X-1 using the National Radio Observatory’s Very Long Baseline Array (VLBA). The new distance is about 6,070 light years from Earth. This accurate distance was a crucial ingredient for making the precise mass and spin determinations.

Fast Facts for Cygnus X-1:
Credit Optical: DSS; Illustration: NASA/CXC/M.Weiss
Release Date November 17, 2011
Scale Wide field optical image is 4×5 degrees (424×530 light years)
Category Black Holes
Coordinates (J2000) RA 19h 58m 21.70s | Dec +35° 12′ 05.80″
Constellation Cygnus
Instrument ACIS
References arXiv:1106.3690 arXiv:1106.3689 arXiv:1106.3688
Radio
Optical
X-ray
Distance Estimate About 6070 light years

 

Chandra X-ray Observatory

Feb 05

NASA’s Deep Impact Spacecraft Images Comet ISON

This series of images of comet C/2012 S1 (ISON) was taken by the Medium-Resolution Imager of NASA’s Deep Impact spacecraft over a 36-hour period on Jan. 17 and 18, 2013. At the time, the spacecraft was 493 million miles (793 million kilometers) from the comet.
Image credit:

NASA/JPL-Caltech/UMD