Starship Asterisk*

[img3="Credit: ESO/G. Beccari"]http://cdn.eso.org/images/screen/eso1526a.jpg[/img3][hr][/hr]

This rich view of an array of colourful stars and gas was captured by the Wide Field Imager (WFI) camera, on the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile. It shows a young open cluster of stars known as NGC 2367, an infant stellar grouping that lies at the centre of an immense and ancient structure on the margins of the Milky Way.

Discovered from England by the tireless observer Sir William Herschel on 20 November 1784, the bright star cluster NGC 2367 lies about 7000 light-years from Earth in the constellation Canis Major. Having only existed for about five million years, most of its stars are young and hot and shine with an intense blue light. This contrasts wonderfully in this new image with the silky-red glow from the surrounding hydrogen gas.

Open clusters like NGC 2367 are a common sight in spiral galaxies like the Milky Way, and tend to form in their host’s outer regions. On their travels about the galactic centre, they are affected by the gravity of other clusters, as well as by large clouds of gas that they pass close to. Because open clusters are only loosely bound by gravity to begin with, and because they constantly lose mass as some of their gas is pushed away by the radiation of the young hot stars, these disturbances occur often enough to cause the stars to wander off from their siblings, just as the Sun is believed to have done many years ago. An open cluster is generally expected to survive for a few hundred million years before it is completely dispersed.

In the meantime, clusters serve as excellent case studies for stellar evolution. All the constituent stars are born at roughly the same time from the same cloud of material, meaning they can be compared alongside one another with greater ease, allowing their ages to be readily determined and their evolution mapped. ...

[img3="Credit: ESA/Hubble & NASA"]http://cdn.spacetelescope.org/archives/ ... w1526a.jpg[/img3][hr][/hr]

This NASA/ESA Hubble Space Telescope picture shows a galaxy named SBS 1415+437 or SDSS CGB 12067.1, located about 45 million light-years from Earth. SBS 1415+437 is a Wolf–Rayet galaxy, a type of starbursting galaxy with an unusually high number of extremely hot and massive stars known as Wolf–Rayet stars.

These stars can be around 20 times as massive as the Sun, but seem to be on a mission to shed surplus mass as quickly as possible — they blast substantial winds of particles out into space, causing them to dwindle at a rapid rate. A typical star of this type can lose a mass equal to that of our Sun in just 100 000 years!

These massive stars are also incredibly hot, with surface temperatures some 10 to 40 times that of the Sun, and very luminous, glowing at tens of thousands to several million times the brightness of the Sun. Many of the brightest and most massive stars in the Milky Way are Wolf–Rayet stars.

Because these stars are so intense they do not last very long, burning up their fuel and blasting their bulk out into the cosmos on very short timescale ‒ only a few hundred thousand years. Because of this it is unusual to find more than a few of these stars per galaxy — except in Wolf–Rayet galaxies, like the one in this image.

[img3="Credit: ESA/Hubble & NASA
Acknowledgement: Matej Novak"]http://cdn.spacetelescope.org/archives/ ... w1525a.jpg[/img3][hr][/hr]

This NASA/ESA Hubble Space Telescope image shows a planetary nebula named NGC 6153, located about 4000 light-years away in the southern constellation of Scorpius (The Scorpion). The faint blue haze across the frame shows what remains of a star like the Sun after it has depleted most of its fuel. When this happens, the outer layers of the star are ejected, and get excited and ionised by the energetic ultraviolet light emitted by the bright hot core of the star, forming the nebula.

NGC 6153 is a planetary nebula that is elliptical in shape, with an extremely rich network of loops and filaments, shown clearly in this Hubble image. However, this is not what makes this planetary nebula so interesting for astronomers.

Measurements show that NGC 6153 contains large amounts of neon, argon, oxygen, carbon and chlorine — up to three times more than can be found in the Solar System. The nebula contains a whopping five times more nitrogen than the Sun! Although it may be that the star developed higher levels of these elements as it grew and evolved, it is more likely that the star originally formed from a cloud of material that already contained lots more of these elements.

A version of this image was entered into the Hubble’s Hidden Treasures image processing competition by contestant Matej Novak.

[b][i]Credit: ESO/John Colosimo[/i][/b]

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Illuminated by the stars of the Milky Way, the majestic fourth Unit Telescope (UT4) of the Very Large Telescope (VLT) sits atop Cerro Paranal, ready to observe the night sky.

The Paranal Observatory, at an altitude of 2635 metres above sea level, is the world”s most advanced ground-based astronomical observatory and ESO’s flagship facility.

UT4 — also known as Yepun (Venus) — has a main mirror 8.2 metres diameter, and is one of four Unit Telescopes that comprise the VLT. The others are known as Antu (Sun), Kueyen (Moon) and Melipal (Southern Cross). The names of the telescopes are words from the language of the Mapuche people who live some 500 kilometres south of Santiago de Chile.

The four Unit Telescopes can work together to form the ESO Very Large Telescope Interferometer (VLTI). The VLTI allows astronomers to measure details up to 16 times finer than with the individual telescopes.

Visible slightly above the plane of the Milky Way and at the heart of Scorpius (The Scorpion) is the bright red star Antares, the sixteenth brightest star in the night sky. Almost all other objects and constellations are impossible to pick out in this sea of stars.

This picture was taken by photographer John Colosimo with an exposure time of 30 seconds, during which the rotation of the Earth caused the stars to appear as little trails.

[img3="Credit: ESA, NASA (HST WFPC2); ESO (NTT MMI)
Acknowledgement: Jane Charlton (PSU)"]http://cdn.spacetelescope.org/archives/ ... c1514a.jpg[/img3][hr][/hr]

This new NASA/ESA Hubble Space Telescope image shows a gathering of four cosmic companions. This quartet forms part of a group of galaxies known as the Hickson Compact Group 16, or HCG 16 — a galaxy group bursting with dramatic star formation, tidal tails, galactic mergers and black holes.

This quartet is composed of (from left to right) NGC 839, NGC 838, NGC 835, and NGC 833 — four of the seven galaxies that make up the entire group. They shine brightly with their glowing golden centres and wispy tails of gas, set against a background dotted with much more distant galaxies.

Compact groups represent some of the densest concentrations of galaxies known in the Universe, making them perfect laboratories for studying weird and wonderful phenomena. Hickson Compact Groups in particular, as classified by astronomer Paul Hickson in the 1980s, are surprisingly numerous, and are thought to contain an unusually high number of galaxies with strange properties and behaviours.

HCG 16 is certainly no exception. The galaxies within it are bursting with dramatic knots of star formation and intensely bright central regions. Within this single group, astronomers have found two LINERs, one Seyfert 2 galaxy and three starburst galaxies. ...

Ann wrote:

Click to view full size image

Adam Block has a fantastic new image of NGC 4414 and its incredibly huge halo.

The picture I'm posting here is relatively small and not as sharp as it should be. I suggest that you follow the link to Adam Block's own page to see the picture in its full size.

Ann

[img3="Credit: ESA/Hubble & NASA"]http://cdn.spacetelescope.org/archives/ ... w1524a.jpg[/img3][hr][/hr]

This NASA/ESA Hubble Space Telescope image shows a galaxy known as UGC 11411. It is a galaxy type known as an irregular blue compact dwarf (BCD) galaxy.

BCD galaxies are about a tenth of the size of a typical spiral galaxy such as the Milky Way, and are made up of large clusters of hot, massive stars that ionise the surrounding gas with their intense radiation. Because these stars are so hot they glow brightly with a blue hue, giving galaxies like UGC 11411 their characteristic blue tint. With these massive stars being less than 10 million years old, they are very young compared to stellar standards. They were created during a starburst, a galaxy-wide episode of furious star formation. UGC 11411 in particular has an extremely high star formation rate, even for a BCD galaxy.

Unusually for galaxies with such intense star-forming regions, BCDs don’t contain either a lot of dust, or the heavy elements that are typically found as trace elements in recently formed stars, making their composition very similar to that of the material from which the first stars formed in the early Universe. Because of this astronomers consider BCD galaxies to be good objects to study to improve our understanding of primordial star-forming processes.

The bright stars in the image are foreground stars in our own Milky Way galaxy.