Credit 

Lori Allen, Xavier Koenig (Harvard-Smithsonian CfA) et al., JPL-Caltech, NASA

Explanation: 

Giant star forming region W5 is over 200 light-years across and about 6,500 light-years away in the constellation Cassiopeia. W5’s sculpted clouds of cold gas and dust seem to form fantastic shapes in this impressive mosaic of infrared images from the Spitzer Space Telescope. In fact, the area on the right includes the structures previously dubbed the Mountains of Creation. New evidence indicates that successive generations of stars formed in the W5 region in an expanding pattern of triggered star formation. The older, earlier generations of stars seem to cluster near the middle of the enormous cavities, with younger stars seen near the rims. Winds and radiation from the older, central stars likely carve out and compress surrounding interstellar material, triggering the collapse that gave rise to younger, later generations of stars farther out. In the false-color image, heated dust still within the cavities appears red, while the youngest stars are forming in the whitish areas. W5 is also known as IC 1848, and together with IC 1805 it is part of a complex region popularly dubbed the Heart and Soul Nebulae.

Credit:

X-ray(NASA/CXC/Stanford/S.Allen); Optical/Lensing(NASA/STScI/UC Santa Barbara/M.Bradac)

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Description:

Another powerful collision of galaxy clusters has been captured with NASA’s Chandra X-ray Observatory and Hubble Space Telescope. Like its famous cousin, the so-called Bullet Cluster, this clash of clusters provides striking evidence for dark matter and insight into its properties.

Chandra X-ray Image

Like the Bullet Cluster, this newly studied cluster, officially known as MACS J0025.4-1222, shows a clear separation between dark and ordinary matter. This helps answer a crucial question about whether dark matter interacts with itself in ways other than via gravitational forces.

This finding is important because it independently verifies the results found for the Bullet Cluster in 2006. The new results show the Bullet Cluster is not an exception and that the earlier results were not the product of some unknown error.

Just like the original Bullet Cluster, MACS J0025 formed after an incredibly energetic collision between two large clusters in almost the plane of the sky. In some ways, MACS J0025 can be thought of as a prequel to the Bullet Cluster. At its much larger distance of 5.7 billion light years, astronomers are witnessing a collision that occurred long before the Bullet Cluster’s.

Animation of
Galaxy Cluster

Using optical images from Hubble, the team was able to infer the distribution of the total mass (colored in blue) — dark and ordinary matter — using a technique known as gravitational lensing. The Chandra data enabled the astronomers to accurately map the position of the ordinary matter, mostly in the form of hot gas, which glows brightly in X-rays (pink.)

An important difference between the Bullet Cluster and the new system is that MACS J0025 does not actually contain a “bullet”. This feature is a dense, X-ray bright core of gas that can be seen moving through the Bullet Cluster. Nonetheless, the amount of energy involved in this mammoth collision is nearly as extreme as that found in the Bullet Cluster.

As the two clusters that formed MACS J0025 (each almost a whopping million billion times the mass of the Sun) merged at speeds of millions of miles per hour, the hot gas in each cluster collided with the hot gas in the other and slowed down, but the dark matter did not. The separation between the material shown in pink and blue therefore provides direct evidence for dark matter and supports the view that dark matter particles interact with each other only very weakly or not at all, apart from the pull of gravity.

One of the great accomplishments of modern astronomy has been to establish a complete inventory of the matter and energy content of the Universe. The so-called dark matter makes up approximately 23% of this content, five times more than the ordinary matter that can be detected by telescopes. The latest results with MACS J0025 once again confirms these findings.

The international team of astronomers in this study was led by Marusa Bradac of the University of California Santa Barbara (UCSB), and Steve Allen of the Kavli Institute for Particle Astrophysics and Cosmology at Stanford and SLAC. Their results will appear in an upcoming issue of The Astrophysical Journal. Other collaborators included Tommaso Treu (UCSB), Harald Ebeling (University of Hawaii), Richard Massey (Royal Observatory Edinburgh), and R. Glenn Morris, Anja von der Linden, and Douglas Applegate (Stanford).

Credit & Copyright: 

Martin Pugh 

Explanation: 

Astronomers turn detectives when trying to figure out the cause of startling sights like NGC 1316. Their investigation indicates that NGC 1316 is an enormous elliptical galaxy that started, about 100 million years ago, to devour a smaller spiral galaxy neighbor, NGC 1317, just above it. Supporting evidence includes the dark dust lanes characteristic of a spiral galaxy, and faint swirls of stars and gas visible in this wide and deep image. What remains unexplained are the unusually small globular star clusters, seen as faint dots on the image. Most elliptical galaxies have more and brighter globular clusters than NGC 1316. Yet the observed globulars are too old to have been created by the recent spiral collision. One hypothesis is that these globulars survive from an even earlier galaxy that was subsumed into NGC 1316.

Credit & Copyright:

Adam Block, Mount Lemmon SkyCenter, Univ. Arizona

Explanation:

Ten thousand years ago, before the dawn of recorded human history, a new light must suddenly have appeared in the night sky and faded after a few weeks. Today we know this light was an exploding star and record the colorful expanding cloud as the Veil Nebula. Pictured above is the west end of the Veil Nebula known technically as NGC 6960 but less formally as the Witch’s Broom Nebula. The expanding debris cloud gains its colors by sweeping up and exciting existing nearby gas. The supernova remnant lies about 1400 light-years away towards the constellation of Cygnus. This Witch’s Broom actually spans over three times the angular size of the full Moon. The bright star 52 Cygni is visible with the unaided eye from a dark location but unrelated to the ancient supernova.

Credit:

NASA, ESA, Hubble Heritage (STScI/AURA);
A. Fabian (IoA, Cambridge U.), L. Frattare (STScI), CXC, G. Taylor, NRAO,VLA

Explanation:

Active galaxy NGC 1275 is the central, dominant member of the large and relatively nearby Perseus Cluster of Galaxies. A prodigious source of x-rays and radio emission, NGC 1275 accretes matter as entire galaxies fall into it, ultimately feeding a supermassive black hole at the galaxy’s core. This stunning visible light image from the Hubble Space Telescope shows galactic debris and filaments of glowing gas, some up to 20,000 light-years long. The filaments persist in NGC 1275, even though the turmoil of galactic collisions should destroy them. What keeps the filaments together? Recent work indicates that the structures, pushed out from the galaxy’s center by the black hole’s activity, are held together by magnetic fields. To add x-ray data from the Chandra Observatory and radio data from the Very Large Array to the Hubble image, just slide your cursor over the picture. In the resulting composite, x-rays highlight the shells of hot gas surrounding the center of the galaxy, with radio emission filling giant bubble-shaped cavities. Also known as Perseus A, NGC 1275 spans over 100,000 light years and lies about 230 million light years away.

Credit:

NASA/JPL-Caltech/L. Allen & X. Koenig (Harvard-Smithsonian CfA)

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Explanation:

Generations of stars can be seen in this new infrared portrait from NASA’s Spitzer Space Telescope. In this wispy star-forming region, called W5, the oldest stars can be seen as blue dots in the centers of the two hollow cavities (other blue dots are background and foreground stars not associated with the region). Younger stars line the rims of the cavities, and some can be seen as pink dots at the tips of the elephant-trunk-like pillars. The white knotty areas are where the youngest stars are forming. Red shows heated dust that pervades the region’s cavities, while green highlights dense clouds.

W5 spans an area of sky equivalent to four full moons and is about 6,500 light-years away in the constellation Cassiopeia. The Spitzer picture was taken over a period of 24 hours.

Like other massive star-forming regions, such as Orion and Carina, W5 contains large cavities that were carved out by radiation and winds from the region’s most massive stars. According to the theory of triggered star-formation, the carving out of these cavities pushes gas together, causing it to ignite into successive generations of new stars.

This image contains some of the best evidence yet for the triggered star-formation theory. Scientists analyzing the photo have been able to show that the ages of the stars become progressively and systematically younger with distance from the center of the cavities.

This is a three-color composite showing infrared observations from two Spitzer instruments. Blue represents 3.6-micron light and green shows light of 8 microns, both captured by Spitzer’s infrared array camera. Red is 24-micron light detected by Spitzer’s multiband imaging photometer.

Credit:

FORS1, 8.2-meter VLT Antu, ESO

Explanation:

Galaxies are fascinating not only for what is visible, but for what is invisible. Grand spiral galaxy NGC 1232, captured in detail by one of the new Very Large Telescopes, is a good example. The visible is dominated by millions of bright stars and dark dust, caught up in a gravitational swirl of spiral arms rotating about the center. Open clusters containing bright blue stars can be seen sprinkled along these spiral arms, while dark lanes of dense interstellar dust can be seen sprinkled between them. Less visible, but detectable, are billions of dim normal stars and vast tracts of interstellar gas, together wielding such high mass that they dominate the dynamics of the inner galaxy. Invisible are even greater amounts of matter in a form we don’t yet know - pervasive dark matter needed to explain the motions of the visible in the outer galaxy. What’s out there?

Description:

A group of baby stars form a “stellar snowflake” in Spitzer’s observations of a dusty region near the Cone Nebula. (Running Time: 1:56)

Source:

Spitzer Space Telescope’s Hidden Universe HD

Credit & Copyright:

Tony Hallas

Explanation:

NGC 6888, also known as the Crescent Nebula, is a cosmic bubble about 25 light-years across, blown by winds from its central, bright, massive star. This beautiful telescopic view combines a composite color image with narrow band data that isolates light from hydrogen and oxygen atoms in the wind-blown nebula. The oxygen atoms produce the blue-green hue that seems to enshroud the detailed folds and filaments. NGC 6888’s central star is classified as a Wolf-Rayet star (WR 136). The star is shedding its outer envelope in a strong stellar wind, ejecting the equivalent of the Sun’s mass every 10,000 years. The nebula’s complex structures are likely the result of this strong wind interacting with material ejected in an earlier phase. Burning fuel at a prodigious rate and near the end of its stellar life this star should ultimately go out with a bang in a spectacular supernova explosion. Found in the nebula rich constellation Cygnus, NGC 6888 is about 5,000 light-years away.

Credit:

NASA/CXC/NCSU/S.Reynolds et al. (X-ray); (NSF/NRAO/VLA/Cambridge/D.Green et al. (radio)

Description:

What if a star exploded near us and no one noticed? Well, it happened, and not so long ago. The remnant left behind by this explosion, called G1.9+0.3, was observed near the center of our Galaxy by the radio telescopes of the Very Large Array in 1985, but astronomers didn’t know when the explosion occurred, just that it did occur some point in time. Previous Galactic supernova were some of the most spectacular celestial events of all time. One was observed by Tycho Brahe in 1572, and one a few years later by Johannes Kepler in 1604. Two observed by the naked eye within 32 years of each other, then nothing seen by eye since then. G1.9+0.3 is an obscure name for an obscure explosion - no doubt this explosion would have been spectacular too, except for the fact that the star that exploded lay behind an enormous depth of interstellar dust, which made the explosion about a trillion times fainter than it would have been otherwise. But while optical emission can’t penetrate through the dust, radio and X-rays can. The image above is a composite X-ray and radio image of G1.9+0.3. The VLA radio image, in blue, was the image of the remnant from 1985, while a 2007 X-ray image (from the Chandra X-ray Observatory) is in orange. It’s obvious that the X-ray image image is larger than the radio image, showing the expansion of the remnant in the intervening 25 years. Astronomers can estimate the expansion speed of the remnant and how far away it is, so determining the expansion time allows an estimate of the time of explosion. It turns out that the star that created G1.9+0.3 exploded only 140 years ago, making it the most recent Galactic supernova ever discovered