This image, taken by the Hubble Space Telescope, shows a detailed view of the spiral arms on one side of the galaxy Messier 99, a grand design spiral galaxy with long, large and clearly defined spiral arms — giving it a structure somewhat similar to the Milky Way.
Lying around 50 million light-years away, Messier 99 is one of over a thousand galaxies that make up the Virgo Cluster, the closest cluster of galaxies to us. Messier 99 itself is relatively bright and large, meaning it was one of the first galaxies to be discovered, way back in the 18th century.
In recent years, a number of unexplained phenomena in Messier 99 have been studied by astronomers. Among these is the nature of one of the brighter stars visible in this image. Catalogued as PTF 10fqs, and visible as a yellow-orange star in the top-left corner of this image, the star has so far defied classification: it is brighter than a nova, but fainter than a supernova.
Scientists have offered a number of possible explanations, including the intriguing suggestion that it could have been caused by a giant planet plunging into its parent star.
Crash of the Titans: Andromeda Galaxy and the Milky Way Collision
NASA astronomers announced Thursday they can now predict with certainty the next major cosmic event to affect our galaxy, Sun, and solar system: the titanic collision of our Milky Way galaxy with the neighboring Andromeda galaxy.
The Milky Way is destined to get a major makeover during the encounter, which is predicted to happen four billion years from now. It is likely the Sun will be flung into a new region of our galaxy, but our Earth and solar system are in no danger of being destroyed.
The above illustrations depict the view of the night sky just before the predicted merger between our Milky Way galaxy and the neighboring Andromeda galaxy. About 3.75 billion years from now, Andromeda’s disk fills the field of view and its gravity begins to create tidal distortions in the Milky Way.
The view is inspired by dynamical computer modeling of the future collision between the two galaxies. The two galaxies collide about 4 billion years from now and merge to form a single galaxy about 6 billion years from now.
Above:1. (2 billion years from now) The disk of the approaching Andromeda galaxy is noticeably larger. 2. (3.75 billion years fron now) Andromeda fills the field of view. The Milky Way begins to show distortion due to tidal pull from Andromeda. 3. (4 billion years fron now) After its first close pass, Andromeda is tidally stretched out. The Milky Way, too, becomes warped.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.