ALMA Turns its Eyes to Centaurus A

A new image of the centre of the distinctive galaxy Centaurus A, made with the Atacama Large Millimeter/submillimeter Array (ALMA). Centaurus A is a massive elliptical radio galaxy and is the most prominent, as well as by far the nearest, radio galaxy in the sky. Its very luminous centre hosts a supermassive black hole with a mass of about 100 million times that of the Sun.

In visible light, a characteristic feature of the galaxy is the dark band that obscures its centre. This dust lane harbours large amounts of gas, dust and young stars. These features, together with the strong radio emission, are evidence that Centaurus A is the result of a collision between a giant elliptical galaxy, and a smaller spiral galaxy whose remains form the dusty band.

The new ALMA observations, shown in a range of green, yellow and orange colours, reveal the position and motion of the clouds of gas in the galaxy. ALMA was tuned to detect signals with a wavelength around 1.3 millimetres, emitted by molecules of carbon monoxide gas. The motion of the gas in the galaxy causes slight changes to this wavelength, due to the Doppler effect.

The motion is shown in this image as changes in colour. Greener features trace gas coming towards us while more orange features depict gas moving away. We can see that the gas to the left of the centre is moving towards us, while the gas to the right of the centre is moving away from us, indicating that the gas is orbiting around the galaxy.

The clear ring of stars and clusters glowing in a golden colour is the tattered remains of the spiral galaxy being ripped apart by the gravitational pull of the giant elliptical galaxy.

X-ray ‘Echoes’ Probe Habitat of Monster Black Hole

Astronomers using data from the ESA’s XMM-Newton satellite have found a long-sought X-ray signal from NGC 4151, a galaxy that contains a supermassive black hole. When the black hole’s X-ray source flares, its accretion disk reflects the emission about half an hour later. The discovery promises a new way to unravel what’s happening in the neighborhood of these powerful objects.

Write Your Name In Galaxies!

My Galaxies is a website created by UK astronomer Steven Bamford that allows you to type messages using actual images of galaxies acquired through the Sloan Digital Sky Survey and Galaxy Zoo projects.

Create yours here: http://mygalaxies.co.uk/

Stellar Archaeology Traces Milky Way’s History

Unfortunately, stars don’t have birth certificates. So, astronomers have a tough time figuring out their ages. Knowing a star’s age is critical for understanding how our Milky Way galaxy built itself up over billions of years from smaller galaxies. Astronomers from the Space Telescope Science Institute and The Johns Hopkins University’s Center for Astrophysical Sciences have found the next best thing to a star’s birth certificate.

Using a new technique, Kalirai probed the burned-out relics of Sun-like stars, called white dwarfs, in the inner region of our Milky Way galaxy’s halo. The halo is a spherical cloud of stars surrounding our galaxy’s disk. Those stars are 11.5 billion years old, younger than the first generation of Milky Way stars.

They formed more than 2 billion years after the birth of the universe 13.7 billion years ago. Previous age estimates, based on analyzing normal stars in the inner halo, ranged from 10 billion to 14 billion years. The new study reinforces the emerging view that our galaxy’s halo is composed of a layer-cake structure that formed in stages over billions of years.

Above: This illustration shows the Milky Way galaxy’s inner and outer halos. A halo is a spherical cloud of stars surrounding a galaxy. Astronomers have proposed that the Milky Way’s halo is composed of two populations of stars. The age of the stars in the inner halo is 11.5 billion years old. The measurements suggest the inner-halo stars are younger than the outer-halo population, some of which could be 13.5 billion years old.

At the Edge of NGC 891

This sharp cosmic portrait features NGC 891. The spiral galaxy spans about 100 thousand light-years and is seen almost exactly edge-on from our perspective. In fact, about 30 million light-years distant in the constellation Andromeda, NGC 891 looks a lot like our Milky Way.

At first glance, it has a flat, thin, galactic disk and a central bulge cut along the middle by regions of dark obscuring dust. The combined image data also reveals the galaxy’s young blue star clusters and telltale pinkish star forming regions.

And remarkably apparent in NGC 891’s edge-on presentation are filaments of dust that extend hundreds of light-years above and below the center line. The dust has likely been blown out of the disk by supernova explosions or intense star formation activity. Faint neighboring galaxies can also been seen near this galaxy’s disk.

A Pinwheel Galaxy Rainbow

This multi-spectral view of the Pinwheel Galaxy (M101) shows that both young and old stars are evenly distributed along its tightly-wound spiral arms. Such composite images allow astronomers to see how features in one part of the spectrum match up with those seen in other parts.

The Pinwheel Galaxy is in the constellation of Ursa Major. It is about 70% larger than our own Milky Way Galaxy, with a diameter of about 170,000 light years, and sits at a distance of 21 million light years from Earth.

The red colors in the image show infrared light, as seen by the Spitzer Space Telescope. These areas show the heat emitted by dusty lanes in the galaxy, where stars are forming. The yellow component is visible light, observed by the Hubble Space Telescope. Most of this light comes from stars, and they trace the same spiral structure as the dust lanes seen in the infrared.

The blue areas are ultraviolet light, given out by hot, young stars that formed about 1 million years ago. The Galaxy Evolution Explorer (GALEX) captured this component of the image. Finally, the hottest areas are shown in purple, where the Chandra X-ray observatory observed the X-ray emission from exploded stars, million-degree gas, and material colliding around black holes.

A Spiral Within a Spiral

The Hubble Space Telescope captured this image of the spiral galaxy known as ESO 498-G5, located around 100 million light-years away in the constellation of Pyxis. One interesting feature of this galaxy is that its spiral arms wind all the way into the centre, so that ESO 498-G5’s core looks like a bit like a miniature spiral galaxy.

This sort of structure is in contrast to the elliptical star-filled centres (or bulges) of many other spiral galaxies, which instead appear as glowing masses, as in the case of NGC 6384. Astronomers refer to the distinctive spiral-like bulge of galaxies such as ESO 498-G5 as disc-type bulges, or pseudobulges, while bright elliptical centres are called classical bulges.

Observations from the Hubble Space Telescope have shown that star formation is still going on in disc-type bulges and has ceased in classical bulges. While classical bulges look much like a miniature version of an elliptical galaxy, embedded in the centre of a spiral, disc-type bulges look like a second, smaller spiral galaxy located at the heart of the first.

The similarities between types of galaxy bulge and types of galaxy go beyond their appearance. Just like giant elliptical galaxies, the classical bulges consist of great swarms of stars moving about in random orbits. Conversely, the structure and movement of stars within disc-type bulges mirror the spiral arms arrayed in a galaxy’s disc.

A Star-Bursting Filament

The Herschel Space Observatory has discovered a giant, galaxy-packed filament ablaze with billions of new stars. The filament connects two clusters of galaxies that, along with a third cluster, will smash together in several billion years and give rise to one of the largest galaxy superclusters in the universe.

The three galaxy clusters of the emerging supercluster, known as RCS2319, are seen in visible and X-ray light (purple) to the left. Observations by Herschel in infrared light appear to the right, with colored regions indicating greater infrared emissions. A white circle broadly outlines the 8 million light-year-long intergalactic filament in each image.

The amount of infrared light suggests that the galaxies in the filament are cranking out the equivalent of about 1,000 new Suns in terms of mass per year. For comparison’s sake, our Milky Way galaxy is producing about one Sun’s mass-worth of new stars per year.

‘Ghost of Mirach’ rears its spooky head

The galaxy NGC 404, also known as the Ghost of Mirach is shown in visible light on the left, and in ultraviolet as seen by NASA’s Galaxy Evolution Explorer (GALEX) on the right. The fields of view are identical in both pictures, with NGC 404 seen as the whitish spot in the center of the images.

Mirach is a red giant star that looms large in visible light. Because NGC 404 is lost in the glare of this star, it was nicknamed the Ghost of Mirach. But when the galaxy is viewed in ultraviolet light, it comes to “life,” revealing a never-before-seen ring (blue) which contains new stars. This is a surprise considering that the galaxy was previously thought to be dead.

The field of view spans 55,000 light years across. The Ghost of Mirach is located 11 million light-years from Earth. The star Mirach is very close in comparison—it is only 200 light-years away and is visible with the naked eye.

A Stellar Ripple

This false-color composite image shows the Cartwheel galaxy as seen in ultraviolet (blue) by the Galaxy Evolution Explorer (GALEX); in in visible light (green) by the Hubble Space Telescope; in infrared (red) by the Spitzer Space Telescope; and in X-ray (purple) by the Chandra X-ray Observatory.

Approximately 100 million years ago, a smaller galaxy plunged through the heart of Cartwheel galaxy, creating ripples of brief star formation. In this image, the first ripple appears as an ultraviolet-bright blue outer ring. The blue color reveals that associations of stars 5 to 20 times as massive as our sun are forming in this region.

The clumps of pink along the outer blue ring are regions where both X-rays and ultraviolet radiation are superimposed in the image. These X-ray point sources are very likely collections of binary star systems containing a blackhole (called massive X-ray binary systems). The X-ray sources seem to cluster around optical/ultraviolet-bright supermassive star clusters.

The yellow-orange inner ring and nucleus at the center of the galaxy represents the second ripple created in the collision, with much less star formation activity than the first (outer) ring wave. The wisps of red spread throughout the interior of the galaxy are organic molecules that have been illuminated by nearby low-level star formation. The tints of green are less massive, older visible-light stars.

The Galaxy Next Door

Hot stars burn brightly in this new image from NASA’s Galaxy Evolution Explorer, the Andromeda galaxy (M31), located about 2.5 million light-years away. The entire galaxy spans 260,000 light-years across — a distance so large, it took 11 different image segments stitched together to produce this view of the galaxy next door.

The bands of blue-white making up the galaxy’s striking rings are neighborhoods that harbor hot, young, massive stars. Dark blue-grey lanes of cooler dust show up starkly against these bright rings, tracing the regions where star formation is currently taking place in dense cloudy cocoons.

Eventually, these dusty lanes will be blown away by strong stellar winds, as the forming stars ignite nuclear fusion in their cores. Meanwhile, the central orange-white ball reveals a congregation of cooler, old stars that formed long ago.

Andromeda is so bright and close to us that it is one of only ten galaxies that can be spotted from Earth with the naked eye. This view is two-color composite, where blue represents far-ultraviolet light, and orange is near-ultraviolet light.

Beyond the Borders of a Galaxy

The outlying regions around the Southern Pinwheel galaxy (M83) are highlighted in this composite image from NASA’s Galaxy Evolution Explorer (GALEX) and the National Science Foundation’s Very Large Array (VLA) in New Mexico. The blue and pink pinwheel in the center is the galaxy’s main stellar disk, while the flapping, ribbon-like structures are its extended arms.

While the radio data highlight the galaxy’s long, octopus-like arms stretching far beyond its main spiral disk (red), the ultraviolet data reveal clusters of baby stars (blue) within the extended arms. Some clusters of stars, as well as stars in the very remote reaches of the galaxy, extend to up to 140,000 light-years away from its core.

Baby galaxies grew up quickly

Baby galaxies from the young Universe more than 12 billion years ago evolved faster than previously thought, shows new research from the Niels Bohr Institute. This means that already in the early history of the Universe, there was potential for planet formation and life.

The astronomers studied 10 galaxies 10-12 billion light years away and analysed their light spectra. They expected the galaxies to be relatively primitive and poor in heavier elements, but they discovered somewhat to their surprise that the gas in some of the galaxies and thus the stars in them had a very high content of heavier elements. The gas was just as enriched as our own Sun.

Additionally, they discovered that one of the galaxies had high element content in the outer regions. This suggests that large parts of the galaxy are enriched with a high content of heavier elements and that means that already in the early history of the Universe there was potential for planet formation and life.

A Deeper Look at Centaurus A

The peculiar massive elliptical galaxy Centaurus A (NGC 5128) is pictured in this image taken with by the Wide Field Imager attached to the MPG/ESO 2.2-metre telescope at the La Silla Observatory in Chile. With a total exposure time of more than 50 hours this is probably the deepest view of this peculiar and spectacular object every created.

Centaurus A lies about 12 million light-years away in the southern constellation of Centaurus and has the distinction of being the most prominent radio galaxy in the sky. The bright nucleus, strong radio emission and jet features of Centaurus A are produced by a central black hole with a mass of about 100 million times that of the Sun. Matter from the dense central parts of the galaxy releases vast amounts of energy as it falls towards the black hole.

The galaxy’s elliptical nature shows up as the elongated shape of the fainter outer parts. The glow that fills much of the picture comes from hundreds of billions of cooler and older stars. Unlike most elliptical galaxies, however, Centaurus A’s smooth shape is disturbed by a broad and patchy band of dark material that obscures the galaxy’s centre.

The dark band harbours large amounts of gas, dust and young stars. Bright young star clusters appear at the upper-right and lower-left edges of the band along with the red glow of star-forming clouds of hydrogen, whilst some isolated dust clouds are silhouetted against the stellar background.

These features, and the prominent radio emission, are strong evidence that Centaurus A is the result of a merger between two galaxies. The dusty band is probably the mangled remains of a spiral galaxy in the process of being ripped apart by the gravitational pull of the giant elliptical galaxy.

Edge-on Beauty

Visible in the constellation of Andromeda, NGC 891 is located approximately 30 million light-years away from Earth. The Hubble Space Telescope turned its powerful wide field Advanced Camera for Surveys towards this spiral galaxy and took this close-up of its northern half. The galaxy’s central bulge is just out of the image on the bottom left.

The galaxy, spanning some 100 000 light-years, is seen exactly edge-on, and reveals its thick plane of dust and interstellar gas. While initially thought to look like our own Milky Way if seen from the side, more detailed surveys revealed the existence of filaments of dust and gas escaping the plane of the galaxy into the halo over hundreds of light-years.

They can be clearly seen here against the bright background of the galaxy halo, expanding into space from the disc of the galaxy. Astronomers believe these filaments to be the result of the ejection of material due to supernovae or intense stellar formation activity.

A few foreground stars from the Milky Way shine brightly in the image, while distant elliptical galaxies can be seen in the lower right of the image. NGC 891 is part of a small group of galaxies bound together by gravity.