NightSky.ie » Image of the Week

A Bow Shock Near a Young Star

paul — Tue, 29 Jun 2010 22:58:03 +0000

The bow shock around the very young star, LL Ori.

Named for the crescent-shaped wave made by a ship as it moves through water, a bow shock can be created in space when two streams of gas collide. LL Ori emits a vigorous solar wind, a stream of charged particles moving rapidly outward from the star. Our own Sun has a less energetic version of this wind that is responsible for auroral displays on the Earth.

The material in the fast wind from LL Ori collides with slow-moving gas evaporating away from the center of the Orion Nebula, which is located to the lower right in this Heritage image. The surface where the two winds collide is the crescent-shaped bow shock seen in the image.

Unlike a water wave made by a ship, this interstellar bow shock is a three-dimensional structure. The filamentary emission has a very distinct boundary on the side facing away from LL Ori, but is diffuse on the side closest to the star, a characteristic common to many bow shocks.

A second, fainter bow shock can be seen around a star near the upper right-hand corner of the Heritage image. Astronomers have identified numerous shock fronts in this complex star-forming region and are using this data to understand the many complex phenomena associated with the birth of stars.

This image was taken in February 1995 as part of the Hubble Orion Nebula mosaic. A close visitor in our Milky Way galaxy, the nebula is only 1,500 light-years from Earth. The filters used in this color composite represent oxygen, nitrogen, and hydrogen emissions.

Young Star Cluster Westerlund 2

admin — Sun, 27 Jun 2010 15:47:12 +0000

Dusty stellar nursery RCW 49 surrounds young star cluster Westerlund 2 in this remarkable composite skyscape from beyond the visible spectrum of light. Infrared data from the Spitzer Space Telescope is shown in black and white, complimenting the Chandra X-ray image data (in false color) of the hot energetic stars within the cluster’s central region. Looking toward the grand southern constellation Centaurus, both views reveal stars and structures hidden from optical telescopes by obscuring dust. Westerlund 2 itself is a mere 2 million years old or less, and contains some of our galaxy’s most luminous, massive and therefore short-lived stars. The infrared signatures of proto-planetary disks have also been identified in the intense star forming region. At the cluster’s estimated distance of 20,000 light-years, the square marking the Chandra field of view would be about 50 light-years on a side.Credit: X-ray; Y.Nazé, G.Rauw, J.Manfroid (Université de Liège), CXC, NASA

Starry Night of Alamut

paul — Fri, 25 Jun 2010 21:18:07 +0000

A meteor’s streak and the arc of the Milky Way hang over the imposing mountain fortress of Alamut in this starry scene. Found in the central Alborz Mountains of Iran, Alamut Castle was built into the rock in the 9th century. The name means Eagle’s Nest. Home of the legendary Assassins featured in the adventure movie Prince of Persia, Alamut was also historically a center for libraries and education. For a time, it was the residence of important 13th century Persian scholar and astronomer Nasir al-Din al-Tusi. To identify the stars in a night sky Tusi certainly pondered, just slide your cursor over the image. Highlights include bright white stars Deneb (in Cygnus), Vega, and Altair, nebulae near the Galactic Center, and the dark obscuring dust clouds of the Milky Way also known as the Great Rift. Lights at the lower right are from small villages and the capital Tehran, over 100 kilometers away to the southwest.

Image Credit & Copyright: Babak Tafreshi (TWAN)

the Mexican hat

admin — Fri, 25 Jun 2010 08:48:11 +0000

Image of the famous early-type spiral galaxy Messier 104, widely known as the “Sombrero” (the Mexican hat) because of its particular shape. The “Sombrero” is located in the constellation Virgo (The Virgin), at a distance of about 50 million light-years.

Messier 104 is the 104th object in the famous catalogue of nebulae by French astronomer Charles Messier (1730 – 1817). It was not included in the first two editions (with 45 objects in 1774; 103 in 1781), but Messier soon thereafter added it by hand in his personal copy as a “very faint nebula”. The recession velocity, about 1000 km/sec, was first measured by American astronomer Vesto M. Slipher at the Lowell Observatory in 1912; he was also the first to detect the galaxy’s rotation.

Heart and Soul Nebulae

paul — Mon, 24 May 2010 20:22:49 +0000

The Heart and Soul nebulae are seen in this infrared mosaic from NASA’s Wide-field Infrared Survey Explorer, or WISE. The image covers an area of the sky over ten times as wide as the full moon and eight times as high (5.5 x 3.9 degrees) in the constellation Cassiopeia.

Located about 6,000 light-years from Earth, the Heart and Soul nebulae form a vast star-forming complex that makes up part of the Perseus spiral arm of our Milky Way galaxy. The nebula to the left is the Heart, designated IC 1805 and named after its resemblance to a human heart. To the right is the Soul nebula, also known as the Embryo nebula, IC 1848 or W5. The Perseus arm lies further from the center of the Milky Way than the arm that contains our sun. The Heart and Soul nebulae stretch out nearly 580 light-years across, covering a small portion of the diameter of the Milky Way, which is roughly 100,000 light-years across.

The two nebulae are both massive star-making factories, marked by giant bubbles that were blown into surrounding dust by radiation and winds from the stars. WISE’s infrared vision allows it to see into the cooler and dustier crevices of clouds like these, where gas and dust are just beginning to collect into new stars. These stars are less than a few million of years old — youngsters in comparison to stars like the sun, which is nearly 5 billion years old.

Also visible near the bottom of this image are two galaxies, Maffei 1 and Maffei 2. Both galaxies contain billions of stars and, at about 10 million light-years away, are well outside our Milky Way yet relatively close compared to most galaxies. Maffei 1 is the bluish elliptical object and Maffei 2 is the spiral galaxy.

All four infrared detectors aboard WISE were used to make this image. Color is representational: blue and cyan represent infrared light at wavelengths of 3.4 and 4.6 microns, which is dominated by light from stars. Green and red represent light at 12 and 22 microns, which is mostly light from warm dust.

Image credit: NASA/JPL-Caltech/UCLA

The Heart and Soul nebulae are seen in this infrared mosaic from NASA's Wide-field Infrared Survey Explorer, or WISE. Image credit: NASA/JPL-Caltech/UCLA

Spiral Galaxy NGC 3190

paul — Mon, 03 May 2010 15:04:10 +0000

I find images of Spiral Galaxies stunning. Here is an image from the Hubble Legacy Archive of NGC 3190 which is not quite edge on.

“Some spiral galaxies are seen almost sideways. NGC 3190, one such galaxy, is the largest member of the Hickson 44 Group, one of the nearer groups of galaxies to our own Local Group of galaxies. Pictured below, finely textured dust lanes surround the brightly glowing center of this picturesque spiral. Gravitational tidal interactions with other members of its group have likely caused the spiral arms of NGC 3190 to appear asymmetric around the center, while the galactic disk also appears warped. NGC 3190 spans about 75,000 light years across and is visible with a small telescope toward the constellation of the Lion (Leo). “

NGC 3190: Credit: Data - Hubble Legacy Archive, ESA, NASA Processing - Robert Gendler

Wide Angle: The Cat’s Paw Nebula

paul — Sat, 24 Apr 2010 21:36:53 +0000

Nebulae are perhaps as famous for being identified with familiar shapes as perhaps cats are for getting into trouble. Still, no known cat could have created the vast Cat’s Paw Nebula visible in Scorpius. At 5,500 light years distant, Cat’s Paw is an emission nebula with a red color that originates from an abundance of ionized hydrogen atoms. Alternatively known as the Bear Claw Nebula or NGC 6334, stars nearly ten times the mass of our Sun have been born there in only the past few million years. Pictured above, a wide angle, deep field image of the Cat’s Paw nebula was culled from the second Digitized Sky Survey.

Wide Angle: The Cat's Paw Nebula

Never before seen stars in the Rosette Nebula

paul — Tue, 13 Apr 2010 20:46:45 +0000

Another stunning image from Herschel reveals the formation of previously unseen large stars, each one up to ten times the mass of our Sun. These are the stars that will influence where and how the next generation of stars are formed. The image is a new release of ‘OSHI’, ESA’s Online Showcase of Herschel Images.

The Rosette Nebula resides some 5000 light-years from Earth and is associated with a larger cloud that contains enough dust and gas to make the equivalent of 10 000 Sun-like stars. The Herschel image shows half of the nebula and most of the Rosette cloud. The massive stars powering the nebula lie to the right of the image but are invisible at these wavelengths. Each colour represents a different temperature of dust, from –263ºC (only 10ºC above absolute zero) in the red emission to –233ºC in the blue. The bright smudges are dusty cocoons hiding massive protostars. These will eventually become stars containing around ten times the mass of the Sun. The small spots near the centre and in the redder regions of the image are lower mass protostars, similar in mass to the Sun.

Infrared image of the Rosette molecular cloud by the Herschel space observatory. Credits: ESA/PACS & SPIRE Consortium/HOBYS Key Programme Consortia

Spitzer’s Orion

paul — Mon, 12 Apr 2010 22:06:59 +0000

Few cosmic vistas excite the imagination like the Orion Nebula, an immense stellar nursery some 1,500 light-years away. Spanning about 40 light-years across the region, this new infrared image from the Spitzer Space Telescope was constructed from data intended to monitor the brightness of the nebula’s young stars, many still surrounded by dusty, planet-forming disks. Orion’s young stars are only about 1 million years old, compared to the Sun’s age of 4.6 billion years. The region’s hottest stars are found in the Trapezium Cluster, the brightest cluster near picture center. Spitzer’s liquid helium coolant ran out in May 2009, so this false color view is from two channels that still remain sensitive to infrared light at warmer operating temperatures.

IC 418: The Spirograph Nebula

paul — Sun, 11 Apr 2010 21:03:30 +0000

IC 418: The Spirograph Nebula
Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA); Acknowledgement: R. Sahai (JPL) et al.

Credit NASA

Explanation: What is creating the strange texture of IC 418? Dubbed the Spirograph Nebula for its resemblance to drawings from a cyclical drawing tool, planetary nebula IC 418 shows patterns that are not well understood. Perhaps they are related to chaotic winds from the variable central star, which changes brightness unpredictably in just a few hours. By contrast, evidence indicates that only a few million years ago, IC 418 was probably a well-understood star similar to our Sun. Only a few thousand years ago, IC 418 was probably a common red giant star. Since running out of nuclear fuel, though, the outer envelope has begun expanding outward leaving a hot remnant core destined to become a white-dwarf star, visible in the image center. The light from the central core excites surrounding atoms in the nebula causing them to glow. IC 418 lies about 2000 light-years away and spans 0.3 light-years across. This false-color image taken from the Hubble Space Telescope reveals the unusual details.

Protostar HH-34 in Orion

paul — Fri, 09 Apr 2010 06:54:31 +0000

This is a three-colour composite of the young object Herbig-Haro 34 (HH-34), now in the protostar stage of evolution. It is based on CCD frames obtained with the FORS2 instrument in imaging mode, on November 2 and 6, 1999.

This object has a remarkable, very complicated appearance that includes two opposite jets that ram into the surrounding interstellar matter. This structure is produced by a machine-gun-like blast of “bullets” of dense gas ejected from the star at high velocities (approaching 250 km/sec). This seems to indicate that the star experiences episodic “outbursts” when large chunks of material fall onto it from a surrounding disc.

HH-34 is located at a distance of approx. 1,500 light-years, near the famous Orion Nebula, one of the most productive star birth regions. Note also the enigmatic “waterfall” to the upper left, a feature that is still unexplained.

Protostar HH-34 in Orion: Credit ESO

The Milky Way over Ontario Canada

paul — Wed, 07 Apr 2010 17:48:55 +0000

Taken over Ontario, Canada, when part of a spectacular sky is visible in a reflection off a lake. The brightest objects visible are bright stars and the planet Jupiter, seen as the brightest spot on the upper left. A distant town appears as a diffuse glow over the horizon. More faint still, the disk of the Milky Way Galaxy becomes apparent as a dramatic diffuse band across the sky that seems to crash into the horizon far in the distance. In the foreground, a picturesque landscape includes trees, a lake, and a stone wall. Finally, on this serene night in July when the lake water was unusually calm, reflections appear. Visible in the lake are not only reflections of several bright stars, but part of the Milky Way band itself. Careful inspection of the image will reveal, however, that bright stars leave small trails in the lake reflections that do not appear in the sky above. The reason for this is because the above image is actually a digital composite of time-consecutive exposures from the same camera. In the first set of exposures, sky images were co-added with slight rotations to keep the stars in one place.

The Milky Way Over Ontario Credit & Copyright: Kerry-Ann Lecky Hepburn (Weather and Sky Photography)