Here’s the latest report from ESO (European Southern Observatory):

Inside the Fiery Furnace 

This new image from the VLT Survey Telescope (VST) at ESO’s Paranal Observatory in Chile captures a spectacular concentration of galaxies known as the Fornax Cluster, which can be found in the southern hemisphere constellation of Fornax (The Furnace). The cluster plays host to a menagerie of galaxies of all shapes and sizes, some of which are hiding secrets.

This video sequence takes us deep into the faint southern constellation of Fornax (The Furnace). Here we find a rich concentration of bright galaxies — the Fornax Galaxy Cluster. The final very detailed image is a new image of the cluster from the VLT Survey Telescope. Credit: ESO/Digitized Sky Survey 2/A. Fujii. Acknowledgement: Aniello Grado and Luca Limatola. Music: Johan B. Monell (www.johanmonell.com)

Galaxies, it seems, are sociable animals and they like to gather together in large groups, known as clusters. Actually it’s gravity that holds the galaxies in the cluster close together as a single entity, with the pull of gravity arising from large amounts of dark matter, as well as from the galaxies we can see. Clusters can contain anything between about 100 and 1000 galaxies and can be between about 5 and 30 million light-years across.

Galaxy clusters do not come in neatly defined shapes so it is difficult to determine exactly where they begin and end. However, astronomers have estimated that the centre of the Fornax Cluster is in the region of 65 million light-years from Earth. What is more accurately known is that it contains nearly sixty large galaxies, and a similar number of smaller dwarf galaxies. Galaxy clusters like this one are commonplace in the Universe and illustrate the powerful influence of gravity over large distances as it draws together the enormous masses of individual galaxies into one region.

The Fornax Galaxy Cluster is one of the closest of such groupings beyond our Local Group of galaxies. This pan sequence, based on a new VLT Survey Telescope image, shows the central part of the cluster in great detail. The field includes the elegant barred-spiral galaxy NGC 1365 and the big elliptical galaxy NGC 1399. Credit:  ESO. Acknowledgement: Aniello Grado and Luca Limatola. Music: Johan B. Monell (www.johanmonell.com)

At the centre of this particular cluster, in the middle of the three bright fuzzy blobs on the left side of the image, is what is known as a cD galaxy — a galactic cannibal. cD galaxies like this one, called NGC 1399, look similar to elliptical galaxies but are bigger and have extended, faint envelopes [1]. This is because they have grown by swallowing smaller galaxies drawn by gravity towards the centre of the cluster [2].

Indeed, there is evidence that this process is happening before our eyes — if you look closely enough. Recent work by a team of astronomers led by Enrichetta Iodice (INAF – Osservatorio di Capodimonte, Naples, Italy)  [3], using data from ESO’s VST, has revealed a very faint bridge of light between NGC 1399 and the smaller galaxy NGC 1387 to its right. This bridge, which has not been seen before (and is too faint to show up in this picture), is somewhat bluer than either galaxy, indicating that it consists of stars created in gas that was drawn away from NGC 1387 by the gravitational pull of NGC 1399. Despite there being little evidence for ongoing interactions in the Fornax Cluster overall, it seems that NGC 1399 at least is still feeding on its neighbours.

Towards the bottom right of this image is the large barred spiral galaxy NGC 1365. This is a striking example of its type, the prominent bar passing through the central core of the galaxy, and the spiral arms emerging from the ends of the bar. In keeping with the nature of cluster galaxies, there is more to NGC 1365 than meets the eye. It is classified as a Seyfert Galaxy, with a bright active galactic nucleus also containing a supermassive black hole at its centre.

This spectacular image was taken by the VLT Survey Telescope (VST) at ESO’s Paranal Observatory in Chile. At 2.6 metres in diameter, the VST is by no means a large telescope by today’s standards, but it has been designed specifically to conduct large-scale surveys of the sky. What sets it apart is its huge corrected field of view and 256-megapixel camera, called OmegaCAM, which was specially developed for surveying the sky. With this camera the VST can produce deep images of large areas of sky quickly, leaving the really big telescopes — like ESO’s Very Large Telescope (VLT) — to explore the details of individual objects.

Notes
[1] The image captures only the central regions of the Fornax Cluster; it extends over a larger region of sky.

[2] The central galaxy is often the brightest galaxy in a cluster, but in this case the brightest galaxy, NGC 1316, is situated at the edge of the cluster, just outside the area covered by this image. Also known as Fornax A, it is one of the most powerful sources of radio waves in the sky. The radio waves, which can be seen by specialised telescopes sensitive to this kind of radiation, emanate from two enormous lobes extending far into space either side of the visible galaxy. The energy that powers the radio emission comes from a supermassive black hole lurking at the centre of the galaxy which is emitting two opposing jets of high-energy particles. These jets produce the radio waves when they plough into the rarefied gas which occupies the space between galaxies in the cluster.

[3] “The Fornax Deep Survey with VST. I. The extended and diffuse stellar halo of NGC1399 out to 192 kpc” by E. Iodice, M. Capaccioli , A. Grado , L. Limatola, M. Spavone, N.R. Napolitano, M. Paolillo, R. F. Peletier, M. Cantiello, T. Lisker, C. Wittmann, A. Venhola , M. Hilker , R. D’Abrusco, V. Pota, and P. Schipani has been published in the Astrophysical Journal.

NASA JPL posts its latest report on highlights in the night sky for the coming month:

Where to look in the night sky this month for Jupiter, Mars, the Lyrid meteor shower and 2016’s best views of Mercury.

A new report from ESO (European Southern Observatory):

ALMA’s Most Detailed Image of a Protoplanetary Disc

This new image from the Atacama Large Millimeter/submillimeter Array (ALMA) shows the finest detail ever seen in the planet-forming disc around the nearby Sun-like star TW Hydrae. It reveals a tantalising gap at the same distance from the star as the Earth is from the Sun, which may mean that an infant version of our home planet, or possibly a more massive super-Earth, is beginning to form there.

The star TW Hydrae is a popular target of study for astronomers because of its proximity to Earth (only about 175 light-years away) and its status as an infant star (about 10 million years old). It also has a face-on orientation as seen from Earth. This gives astronomers a rare, undistorted view of the complete protoplanetary disc around the star.

“Previous studies with optical and radio telescopes confirm that TW Hydrae hosts a prominent disc with features that strongly suggest planets are beginning to coalesce,” said Sean Andrews with the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, USA and lead author on a paper published today in the Astrophysical Journal Letters. “The new ALMA images show the disc in unprecedented detail, revealing a series of concentric dusty bright rings and dark gaps, including intriguing features that may indicate that a planet with an Earth-like orbit is forming there.”

Other pronounced gaps that show up in the new images are located three billion and six billion kilometres from the central star, similar to the average distances from the Sun to Uranus and Pluto in the Solar System. They too are likely to be the results of particles that came together to form planets, which then swept their orbits clear of dust and gas and shepherded the remaining material into well-defined bands.

For the new TW Hydrae observations, astronomers imaged the faint radio emission from millimetre-sized dust grains in the disc, revealing details on the order of the distance between the Earth and the Sun (about 150 million kilometres). These detailed observations were made possible with ALMA’s high-resolution, long-baseline configuration. When ALMA’s dishes are at their maximum separation, up to 15 kilometres apart, the telescope is able to resolve finer details. “This is the highest spatial resolution image ever of a protoplanetary disc from ALMA, and that won’t be easily beaten in the future!” said Andrews [1].

“TW Hydrae is quite special. It is the nearest known protoplanetary disc to Earth and it may closely resemble the Solar System when it was only 10 million years old,” adds co-author David Wilner, also with the Harvard-Smithsonian Center for Astrophysics.

Earlier ALMA observations of another system, HL Tauri, show that even younger protoplanetary discs — a mere 1 million years old — can display similar signatures of planet formation. By studying the older TW Hydrae disc, astronomers hope to better understand the evolution of our own planet and the prospects for similar systems throughout the Milky Way.

The astronomers now want to find out how common these kinds of features are in discs around other young stars and how they might change with time or environment.

This video shows ALMA’s best image of a protoplanetary disc to date. The picture of the nearby young star TW Hydrae reveals the classic rings and gaps that signify planets are in formation in this system.

Notes

[1] The angular resolution of the images of HL Tauri was similar to these new observations, but as TW Hydrae is much closer to Earth, finer details can be seen.

The latest report from the European Southern Observatory (ESO)

The Wilds of the Local Group

This scene, captured by ESO’s OmegaCAM on the VLT Survey Telescope, shows a lonely galaxy known as Wolf-Lundmark-Melotte, or WLM for short. Although considered part of our Local Group of dozens of galaxies, WLM stands alone at the group’s outer edges as one of its most remote members. In fact, the galaxy is so small and secluded that it may never have interacted with any other Local Group galaxy — or perhaps even any other galaxy in the history of the Universe.

Rather like an uncontacted tribe living deep in the Amazon rainforest or on an island in Oceania, WLM offers a rare insight into the primordial nature of galaxies that have been little disturbed by their environment.

This sequence starts with a broad view of the rather faint constellation of Cetus (The Sea Monster). As we zoom, we close in on a faint galaxy, known as WLM. The final detailed image, captured with the OmegaCAM camera on ESO’s VLT Survey Telescope in Chile, shows the galaxy in great detail, including many of its component stars and some glowing clouds of hydrogen. Credit: ESO/A. Fujii/Digitized Sky Survey 2. Music: Johan B. Monell (www.johanmonell.com). Acknowledgement: VST/Omegacam Local Group Survey

WLM was discovered in 1909 by German astronomer Max Wolf, and identified as a galaxy some fifteen years later by astronomers Knut Lundmark and Philibert Jacques Melotte — explaining the galaxy’s unusual moniker. The dim galaxy is located in the constellation of Cetus (The Sea Monster) about three million light-years away from the Milky Way, which is one of the three dominant spiral galaxies in the Local Group.

WLM is quite small and lacks structure, hence its classification as a dwarf irregular galaxy. WLM spans about 8000 light-years at its greatest extent, a measurement that includes a halo of extremely old stars discovered in 1996 (eso9633).

Astronomers think that comparatively small primeval galaxies gravitationally interacted with each other and in many cases merged, building up into larger composite galaxies. Over billions of years, this merging process assembled the large spiral and elliptical galaxies that now appear to be common in the modern Universe. Galaxies congregating in this manner is similar to the way in which human populations have shifted over thousands of years and intermixed into larger settlements, eventually giving rise to today’s megacities.

WLM has instead developed on its own, away from the influence of other galaxies and their stellar populations. Accordingly, like a hidden human population with limited contact with outsiders, WLM represents a relatively unperturbed “state of nature”, where any changes occurring over its lifetime have taken place largely independent of activity elsewhere.

This small galaxy features an extended halo of very dim red stars, which stretches out into the inky blackness of the surrounding space. This reddish hue is indicative of advanced stellar age. It is likely that the halo dates back to the original formation of the galaxy itself, helpfully offering clues about the mechanisms that spawned the very first galaxies.

This close-up video pan sequence, captured by ESO’s OmegaCAM on the VLT Survey Telescope, shows a lonely galaxy known as Wolf-Lundmark-Melotte, or WLM for short. Although considered part of our Local Group of dozens of galaxies, WLM stands alone at the group’s outer edges as one of its most remote members. In fact, the galaxy is so small and secluded that it may never have interacted with any other Local Group galaxy — or perhaps even any other galaxy in the history of the Universe. Credit: ESO. Music: Johan B. Monell (www.johanmonell.com). Acknowledgement: VST/Omegacam Local Group Survey

The stars at the centre of WLM, meanwhile, appear younger and bluer in colour. In this image, pinkish clouds highlight areas where the intense light from young stars has ionised ambient hydrogen gas, making it glow in a characteristic shade of red.

This detailed image was captured by the OmegaCAM wide-field imager, a huge camera mounted on ESO’s VLT Survey Telescope (VST) in Chile — a 2.6-metre telescope exclusively designed to survey the night sky in visible light. OmegaCAM’s 32 CCD detectors create 256-megapixel images, offering a very detailed wide-field view of the cosmos.