Friday, October 31, 2008

A Witch by Starlight

A Witch by Starlight Credit & Copyright: Star Shadows Remote Observatory

By starlight this eerie visage shines in the dark, a crooked profile evoking its popular name, the Witch Head Nebula.

In fact, this entrancing telescopic portrait gives the impression the witch has fixed her gaze on Orion's bright supergiant star Rigel.

Spanning over 50 light-years, the dusty cosmic cloud strongly reflects nearby Rigel's blue light, giving it the characteristic color of a reflection nebula. Cataloged as IC 2118, the Witch Head Nebula is about 1,000 light-years away. Of course, you might see a witch this scary tonight, but don't panic. Have a safe and Happy Halloween!

Monday, October 27, 2008

Great Orion Nebula

Great Orion Nebulae Credit & Copyright: Tony Hallas

The Great Nebula in Orion, also known as M42, is one of the most famous nebulae in the sky. The star forming region's glowing gas clouds and hot young stars are on the right in this sharp and colourful two frame mosaic that includes the smaller nebula M43 near center and dusty, bluish reflection nebulae NGC 1977 and friends on the left.

Located at the edge of an otherwise invisible giant molecular cloud complex, these eye-catching nebulae represent only a small fraction of this galactic neighborhood's wealth of interstellar material.

Within the well-studied stellar nursery, astronomers have also identified what appear to be numerous infant solar systems. The gorgeous skyscape spans nearly two degrees or about 45 light-years at the Orion Nebula's estimated distance of 1,500 light-years.

Tuesday, October 21, 2008

A Dark Pulsar in CTA1

A Dark Pulsar in CTA 1 Credit: NASA, S. Pineault (DRAO)

Previously, the CTA 1 -- supernova remnant -- revealed a compact nebula, a bent jet, and a point source expected to be a pulsar - a rotating neutron star producing pulses at radio energies - all of which are characteristic of energetic, rotation-powered pulsars. But no radio pulses were detected.

Now NASA's recently deployed Fermi Space Telescope has solved the mystery with some of its initial observations indicating that the point source is pulsing at gamma-ray energies.

The strange source is the first of a class that might be dubbed "dark pulsars", rotating neutron stars that appear to pulse only in high-energy radiations. Such pulsars might not be detectable in radio or visible light if they emit those radiations into a narrow beam not seen from Earth. If true, our Galaxy might have more pulsars left for Fermi to discover.

Studying the gamma-ray properties of pulsars gives valuable clues to physics of the emission regions on neutron stars. In this graphic, the pulsar's position is indicated in the wider CTA 1 supernova remnant. An artist's illustration of the pulsar beaming at gamma-ray energies is shown in the inset.

Sunday, October 12, 2008

Bright Bolide

Credit & Copyright: Howard Edin (Oklahoma City Astronomy Club)

On September 30, a spectacular bolide or fireball meteor surprised a group of amateur astronomers enjoying dark night skies over the Oklahoma panhandle's Black Mesa State Park in the Midwestern US. Flashing past familiar constellations Taurus (top) and Orion, the extremely bright meteor was captured by a hillside camera overlooking the 2008 Okie-Tex Star Party.

Astronomy enthusiast Howard Edin reports that he was looking in the opposite direction at the time, but saw the whole observing field light up and at first thought someone had turned on their car headlights. So far the sighting of such a bright bolide meteor, produced as a space rock is vaporized hurtling through Earth's atmosphere, really is a matter of luck. But that could change.

Earlier this week the discovery and follow-up tracking of tiny asteroid 2008 TC3 allowed astronomers to predict the time and location of its impact with the atmosphere. While no ground-based sightings of the fireball seem to have been reported, this first ever impact prediction was confirmed by at least some detections of an air burst and bright flash on October 7th over northern Sudan.

Tuesday, October 07, 2008

The Circinus Galaxy

Credit: X-ray (NASA/CXC/Columbia/F.Bauer et al);
Optical (NASA/STScI/UMD/A.Wilson et al.)

This composite image shows the central regions of the nearby Circinus galaxy, located about 12 million light years away. Data from NASA's Chandra X-ray Observatory is shown in blue and data from the Hubble Space telescope is shown in yellow ("I-band"), red (hydrogen emission), cyan ("V-band") and light blue (oxygen emission). The bright, blue source near the lower right hand corner of the image is the supernova SN 1996cr, that has finally been identified over a decade after it exploded.

Optical images from the archives of the Anglo-Australian Telescope in Australia show that SN 1996cr exploded between February 28, 1995 and March 15, 1996. Among the five nearest supernovas of the last 25 years, SN 1996cr is the only one that was not seen shortly after the explosion. It may not have been noticed by astronomers at the time because it was only visible in the southern hemisphere, which is not as widely monitored as the northern.

The supernova was first singled out in 2001 as a bright, variable object in a Chandra image. Despite some exceptional properties, its nature remained unclear until years later, when scientists were able to confirm this object was a supernova. Clues in data from the European Southern Observatory's Very Large Telescope led the team to search through data archives from 18 different telescopes, both in space and on the ground, nearly all of which was from archives. This is a remarkable example of the new era of `Internet astronomy'.

The Circinus galaxy is a popular target for astronomers because it contains a supermassive black hole that is actively growing, and it shows vigorous star formation. It is also nearby, at only about 4 times the distance of M31.