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Sunday, October 22, 2017

Spiral Galaxy NGC 4424

Spiral Galaxy NGC 4424
Click on the image for full resolution (4.1 MB)

Two galaxies are clearly visible in this Hubble image, the larger of which is NGC 4424. This galaxy is catalogued in the New General Catalogue of Nebulae and Clusters of Stars (NGC), which was compiled in 1888. The NGC is one of the largest astronomical catalogues, which is why so many Hubble Pictures of the Week feature NGC objects. In total there are 7840 entries in the catalogue and they are also generally the larger, brighter, and more eye-catching objects in the night sky, and hence the ones more easily spotted by early stargazers. The smaller, flatter, bright galaxy sitting just below NGC 4424 is named LEDA 213994. The Lyon-Meudon Extragalactic Database (LEDA) is far more modern than the NGC. Created in 1983 at the Lyon Observatory it contains millions of objects. However, many NGC objects still go by their initial names simply because they were christened within the NGC first. No astronomer can resist a good acronym, and "LEDA" is more appealing than "the LMED", perhaps thanks to the old astronomical affinity with mythology when it comes to naming things: Leda was a princess in Ancient Greek mythology.
Image Credit: ESA/Hubble and NASA
Image enhancement: Jean-Baptiste Faure

Saturday, May 20, 2017

Interacting Galaxies NGC 3447

Interacting Galaxies NGC 3447
Click on the image for full resolution (5.9 MB)

Some galaxies are harder to classify than others. Here, Hubble's trusty Wide Field Camera 3 (WFC3) has captured a striking view of two interacting galaxies located some 60 million light-years away in the constellation of Leo (The Lion). The more diffuse and patchy blue glow covering the right side of the frame is known as NGC 3447 – sometimes NGC 3447B for clarity, as the name NGC 3447 can apply to the overall duo. The smaller clump to the upper left is known as NGC 3447A. The trouble with space is that it is, to state the obvious, really, really big. Astronomers have for hundreds of years been discovering and naming galaxies, stars, cosmic clouds and more. Unifying and regulating the conventions and classifications for everything ever observed is very difficult, especially when you get an ambiguous object like NGC 3447, which stubbornly defies easy categorisation. Overall, we know NGC 3447 comprises a couple of interacting galaxies, but we're unsure what each looked like before they began to tear one another apart. The two sit so close that they are strongly influenced and distorted by the gravitational forces between them, causing the galaxies to twist themselves into the unusual and unique shapes seen here. NGC 3447A appears to display the remnants of a central bar structure and some disrupted spiral arms, both properties characteristic of certain spiral galaxies. Some identify NGC 3447B as a former spiral galaxy, while others categorise it as being an irregular galaxy.
Image Credit: ESA/Hubble and NASA
Image enhancement: Jean-Baptiste Faure

Thursday, April 6, 2017

Supernova Remnant N103B

Supernova Remnant N103B
Click on the image for full resolution (5.8 MB)

This image, taken with the Hubble Space Telescope, shows the supernova remnant SNR 0509-68.7, also known as N103B. N103B was a Type Ia supernova, located in the Large Magellanic Cloud – a neighbouring galaxy of the Milky Way. Owing to its relative proximity to Earth, astronomers observe the remnant to search for a potential stellar survivor of the explosion. The orange-red filaments visible in the image show the shock fronts of the supernova explosion. These filaments allow astronomers to calculate the original centre of the explosion. The filaments also show that the explosion is no longer expanding as a sphere, but is elliptical in shape. Astronomers assume that part of material ejected by the explosion hit a denser cloud of interstellar material, which slowed its speed. The shell of expanding material being open to one side supports this idea. The gas in the lower half of the image and the dense concentration of stars in the lower left are the outskirts of the star cluster NGC 1850, which has been observed by Hubble in the past.
Image Credit: ESA/Hubble, NASA
Image enhancement: Jean-Baptiste Faure

Saturday, February 4, 2017

Emission Nebulae NGC 6334 and NGC 6357

Emission Nebulae NGC 6334 and NGC 6357
Click on the image for full resolution (4.3 MB)

This spectacular image from the VLT Survey Telescope shows the Cat’s Paw Nebula (NGC 6334, upper right) and the Lobster Nebula (NGC 6357, lower left). These dramatic objects are regions of active star formation where the hot young stars are causing the surrounding hydrogen gas to glow red. The very rich field of view also includes dark clouds of dust. With around two billion pixels this is one of the largest images ever released by ESO. A zoomable version of this giant image is available here. Note that the circular features in the image around bright stars are not real, they are due to reflections within the optics of the telescope and camera.
Image Credit: ESO
Image enhancement: Jean-Baptiste Faure

Tuesday, January 31, 2017

Planetary Nebula OH 231.8+04.2

Planetary Nebula OH 231.8+04.2
Click on the image for full resolution

The Calabash Nebula, pictured here – which has the technical name OH 231.8+04.2 – is a spectacular example of the death of a low-mass star like the Sun. This image taken by the Hubble Space Telescope shows the star going through a rapid transformation from a red giant to a planetary nebula, during which it blows its outer layers of gas and dust out into the surrounding space. The recently ejected material is spat out in opposite directions with immense speed – the gas shown in yellow is moving close to a million kilometers an hour. Astronomers rarely capture a star in this phase of its evolution because it occurs within the blink of an eye – in astronomical terms. Over the next thousand years the nebula is expected to evolve into a fully fledged planetary nebula. The nebula is also known as the Rotten Egg Nebula because it contains a lot of sulphur, an element that, when combined with other elements, smells like a rotten egg – but luckily, it resides over 5000 light-years away in the constellation of Puppis (The Poop deck).
Image Credit: ESA/Hubble and NASA
Acknowledgement: Judy Schmidt
Image enhancement: Jean-Baptiste Faure

Saturday, January 28, 2017

Dwarf Spiral Galaxy NGC 4707

Dwarf Spiral Galaxy NGC 4707
Click on the image for full resolution (4.0 MB)

On a clear evening in April of 1789, the renowned astronomer William Herschel continued his unrelenting survey of the night sky, hunting for new cosmic objects – and found cause to celebrate! Lengthening his impressive list of cosmic discoveries yet again, the astronomer spotted this bright spiral galaxy, named NGC 4707, lurking in the constellation of Canes Venatici (The Hunting Dog). NGC 4707 lies roughly 22 million light-years from Earth. Over two centuries later, the Hubble Space Telescope is able to view the same galaxy in far greater detail than Herschel could, allowing us to appreciate the intricacies and characteristics of NGC 4707 as never before. This striking image comprises observations from Hubble's Advanced Camera for Surveys (ACS), one of a handful of high-resolution instruments currently aboard the space telescope. Herschel himself reportedly described NGC 4707 as a "small, stellar" galaxy; while it is classified as a spiral (type Sm), its overall shape, centre, and spiral arms are very loose and undefined, and its central bulge is either very small or non-existent. It instead appears as a rough sprinkling of stars and bright flashes of blue on a dark canvas, as if a pointillist painter had dotted the cosmos with small pinpricks of bright paint. The blue smudges seen across the frame highlight regions of recent or ongoing star formation, with newborn stars glowing in bright, intense shades of cyan and turquoise.
Image Credit: ESA/Hubble and NASA
Image enhancement: Jean-Baptiste Faure

Monday, December 12, 2016

Barred Spiral Galaxy IC 5201

Barred Spiral Galaxy IC 5201
Click on the image for full resolution (7.6 MB)

In 1900, astronomer Joseph Lunt made a discovery: Peering through a telescope at Cape Town Observatory, the British–South African scientist spotted this beautiful sight in the southern constellation of Grus: a barred spiral galaxy now named IC 5201. Over a century later, the galaxy is still of interest to astronomers. For this image, the Hubble Space Telescope used its Advanced Camera for Surveys (ACS) to produce a beautiful and intricate image of the galaxy. Hubble's ACS can resolve individual stars within other galaxies, making it an invaluable tool to explore how various populations of stars have sprung to life, evolved, and died throughout the cosmos. IC 5201 sits over 40 million light-years away from us. As with two thirds of all the spirals we see in the Universe – including the Milky Way, the galaxy has a bar of stars slicing through its center.
Image Credit: ESA/Hubble and NASA
Image enhancement: Jean-Baptiste Faure