Tuesday, November 19, 2019

Spiral Galaxy NGC 4380

Spiral Galaxy NGC 4380
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The galaxy NGC 4380 looks like a special effect straight out of a science fiction or fantasy film in this Hubble picture like a gaping portal to another dimension.
In the grand scheme of things, though, the galaxy is actually quite ordinary. Spiral galaxies like NGC 4380 are one of the most common types of galaxy in the Universe. These colossal collections of stars, often numbering in the hundreds of billions, are shaped like a flat disc, sometimes with a rounded bulge in the center. Graceful spiral arms outlined by dark lanes of dust wind around the bulging core, which glows brightly and has the highest concentration of stars in the galaxy.
Image Credit: ESA/Hubble and NASA, P. Erwin
Image enhancement: Jean-Baptiste Faure

Saturday, November 16, 2019

Dwarf Galaxy UGC 1281

Dwarf Galaxy UGC 1281
Click on the image for higher resolution (8.9 MB)

The galaxy cutting dramatically across the frame of this Hubble Space Telescope image is a slightly warped dwarf galaxy known as UGC 1281. Seen here from an edge-on perspective, this galaxy lies roughly 18 million light-years away in the constellation of Triangulum (The Triangle). The bright companion to the lower left of UGC 1281 is the small galaxy PGC 6700, officially known as 2MASX J01493473+3234464. Other prominent stars belonging to our own galaxy, the Milky Way, and more distant galaxies can be seen scattered throughout the sky.
The side-on view we have of UGC 1281 makes it a perfect candidate for studies into how gas is distributed within galactic halos – the roughly spherical regions of diffuse gas extending outwards from a galaxy's center. Astronomers have studied this galaxy to see how its gas vertically extends out from its central plane, and found it to be a quite typical dwarf galaxy. However, it does have a slightly warped shape to its outer edges, and is forming stars at a particularly low rate. A version of this image was entered into the Hubble's Hidden Treasures image processing competition by contestant Luca Limatola.
Image Credit: ESA/Hubble and NASA
Acknowledgement: Luca Limatola
Image enhancement: Jean-Baptiste Faure

Barred Spiral Galaxy NGC 4394

Barred Spiral Galaxy NGC 4394
Click on the image for higher resolution (8.4 MB)

Discovered in 1784 by the German–British astronomer William Herschel, NGC 4394 is a barred spiral galaxy situated about 55 million light-years from Earth. The galaxy lies in the constellation of Coma Berenices (Berenice's Hair), and is considered to be a member of the Virgo Cluster.
NGC 4394 is the archetypal barred spiral galaxy, with bright spiral arms emerging from the ends of a bar that cuts through the galaxy's central bulge. These arms are peppered with young blue stars, dark filaments of cosmic dust, and bright, fuzzy regions of active star formation. At the center of NGC 4394 lies a region of ionised gas known as a LINER. LINERs are active regions that display a characteristic set of emission lines in their spectra – mostly weakly ionised atoms of oxygen, nitrogen and sulphur.
Although LINER galaxies are relatively common, it's still unclear where the energy comes from to ionise the gas. In most cases it is thought to be the influence of a black hole at the center of the galaxy, but it could also be the result of a high level of star formation. In the case of NGC 4394, it is likely that gravitational interaction with a nearby neighbour has caused gas to flow into the galaxy's central region, providing a new reservoir of material to fuel the black hole or to make new stars.
Image Credit: ESA/Hubble and NASA
Acknowledgement: Judy Schmidt (Geckzilla)
Image enhancement: Jean-Baptiste Faure

Colliding Galaxy Clusters MACS J0416.1-2403

Colliding Galaxy Clusters MACS J0416.1-2403
Click on the image for higher resolution (5.8 MB)

At first glance, this cosmic kaleidoscope of purple, blue and pink offers a strikingly beautiful – and serene – snapshot of the cosmos. However, this multi-coloured haze actually marks the site of two colliding galaxy clusters, forming a single object known as MACS J0416.1-2403 (or MACS J0416 for short).
MACS J0416 is located about 4.3 billion light-years from Earth, in the constellation of Eridanus. This new image of the cluster combines data from three different telescopes: the NASA/ESA Hubble Space Telescope (showing the galaxies and stars), the NASA Chandra X-ray Observatory (diffuse emission in blue), and the NRAO Jansky Very Large Array (diffuse emission in pink). Each telescope shows a different element of the cluster, allowing astronomers to study MACS J0416 in detail.
As with all galaxy clusters, MACS J0416 contains a significant amount of dark matter, which leaves a detectable imprint in visible light by distorting the images of background galaxies. In this image, this dark matter appears to align well with the blue-hued hot gas, suggesting that the two clusters have not yet collided; if the clusters had already smashed into one another, the dark matter and gas would have separated. MACS J0416 also contains other features – such as a compact core of hot gas – that would likely have been disrupted had a collision already occurred.
Together with five other galaxy clusters, MACS J0416 is playing a leading role in the Hubble Frontier Fields programme, for which this data was obtained. Owing to its huge mass, the cluster is in fact bending the light of background objects, acting as a magnifying lens. Astronomers can use this phenomenon to find galaxies that existed only hundreds of million years after the big bang.
Image Credit: NASA, ESA, CXC, NRAO/AUI/NSF, STScI, and G. Ogrean (Stanford University)
Acknowledgment: NASA, ESA, and J. Lotz (STScI), and the HFF team

Supernova Remnant DEM L71

Supernova Remnant DEM L71
Click on the image for higher resolution (3.8 MB)

Several thousand years ago, a star some 160,000 light-years away from us exploded, scattering stellar shrapnel across the sky. The aftermath of this energetic detonation is shown here in this striking image from the Hubble Space Telescope's Wide Field Camera 3.
The exploding star was a white dwarf located in the Large Magellanic Cloud, one of our nearest neighbouring galaxies. Around 97% of stars within the Milky Way that are between a tenth and eight times the mass of the Sun are expected to end up as white dwarfs. These stars can face a number of different fates, one of which is to explode as supernovae, some of the brightest events ever observed in the Universe. If a white dwarf is part of a binary star system, it can siphon material from a close companion. After gobbling up more than it can handle – and swelling to approximately one and a half times the size of the Sun – the star becomes unstable and ignites as a Type Ia supernova.
This was the case for the supernova remnant pictured here, which is known as DEM L71. It formed when a white dwarf reached the end of its life and ripped itself apart, ejecting a superheated cloud of debris in the process. Slamming into the surrounding interstellar gas, this stellar shrapnel gradually diffused into the separate fiery filaments of material seen scattered across this skyscape.
Image Credit: ESA/Hubble and NASA, Y. Chu

Friday, November 15, 2019

Globular Cluster NGC 1898

Globular Cluster NGC 1898
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This glittering ball of stars is the globular cluster NGC 1898, which lies towards the center of the Large Magellanic Cloud – one of our closest cosmic neighbours. The Large Magellanic Cloud is a dwarf galaxy that hosts an extremely rich population of star clusters, making it an ideal laboratory for investigating star formation.
Discovered in November 1834 by British astronomer John Herschel, NGC 1898 has been scrutinised numerous times by the Hubble Space Telescope. Today we know that globular clusters belong to the oldest known objects in the Universe and that they are relics of the first epochs of galaxy formation. While we already have a pretty good picture on the globular clusters of the Milky Way – still with many unanswered questions – our studies on globular clusters in nearby dwarf galaxies just started.
The observations of NGC 1898 will help to determine if their properties are similar to the ones found in the Milky Way, or if they have different features, due to being in a different cosmic environment.
This image was taken by Hubble's Advanced Camera for Surveys (ACS) and Wide Field Camera 3 (WFC3). The WFC3 observes light ranging from near-infrared to near-ultraviolet wavelengths, while the ACS explores the near-infrared to the ultraviolet.
Image Credit: ESA/Hubble and NASA
Image enhancement: Jean-baptiste Faure

Barred Spiral Galaxy NGC 7640

Barred Spiral Galaxy NGC 7640
Click on the image for higher resolution (9.2 MB)

Not to be confused with our neighbouring Andromeda Galaxy, the Andromeda constellation is one of the 88 modern constellations. More importantly for this image, it is home to the pictured NGC 7640.
Many different classifications are used to identify galaxies by shape and structure – NGC 7640 is a barred spiral type. These are recognisable by their spiral arms, which fan out not from a circular core, but from an elongated bar cutting through the galaxy's center. Our home galaxy, the Milky Way, is also a barred spiral galaxy. NGC 7640 might not look much like a spiral in this image, but this is due to the orientation of the galaxy with respect to Earth – or to Hubble, which acted as photographer in this case! We often do not see galaxies face on, which can make features such as spiral arms less obvious.
There is evidence that NGC 7640 has experienced some kind of interaction in its past. Galaxies contain vast amounts of mass, and therefore affect one another via gravity. Sometimes these interactions can be mild, and sometimes hugely dramatic, with two or more colliding and merging into a new, bigger galaxy. Understanding the history of a galaxy, and what interactions it has experienced, helps astronomers to improve their understanding of how galaxies – and the stars within them – form.
Image Credit: ESA/Hubble and NASA
Image enhancement: Jean-Baptiste Faure