Irregular Galaxy NGC 55. Credit: ESO. Click for larger version.
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As part of the International Year of Astronomy project, 100 Hours of Astronomy, the ambitious “Around the World in 80 Telescopes” event had a live webcast, going around the globe to some of the most advanced observatories on and off the planet. In celebration of this world tour of observatories, many of the telescopes are releasing wonderful, and previously unseen, astronomical images. Here are two observed by telescopes at the La Silla and Paranal observatories. Above is the irregular galaxy NGC 55, a galaxy that is about 70,000 light-years across, just a tad smaller than our own Milky Way, and below is NGC 7793, about half that size.
NGC 55 is a member of the prominent Sculptor group of galaxies in the southern constellation of Sculptor. By studying about 20 planetary nebulae in this image, a team of astronomers found that NGC 55 is located about 7.5 million light-years away. Planetary nebulae are the final blooming of Sun-like stars before their retirement as white dwarfs.
This striking image of NGC 55, obtained with the Wide Field Imager on the 2.2-metre MPG/ESO telescope at La Silla, is dusted with a flurry of reddish nebulae, created by young, hot massive stars. A large number of individual stars that can be counted within NGC 55. Spiral Galaxy NGC 7793. Credit: ESO. Click for larger version.
The second image shows another galaxy belonging to the Sculptor group. This is NGC 7793, which has a chaotic spiral structure, unlike the class of grand-design spiral galaxies to which our Milky Way belongs. The image shows how difficult it is to identify any particular spiral arm in these chaotic structures, although it is possible to guess at a general rotating pattern. NGC 7793 is located slightly further away than NGC 55, about 12.5 million light-years from us.
NGC 7793 was observed with one of the workhorses of the ESO Paranal Observatory, the FORS instrument, attached to the Very Large Telescope.
The Triangulum Galaxy. Image credit: NASA/JPL-Caltech/University of Arizona
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NASA’s Spitzer Space Telescope has captured this new image of M33, also known as the Triangulum Galaxy, and released it as part of the “Around the World in 80 Telescopes” event for the International Year of Astronomy.
Besides the pretty colors, the new image reveals something else about M33: it’s more than meets the eye.
M33 is located about 2.9 million light-years away in the constellation Triangulum. It is a member of what’s known as our Local Group of galaxies. Along with our own Milky Way and Andromeda, the group of about 50 galaxies travels together in the universe, bound to one another by gravity. In fact, M33 is one of the few galaxies that is moving toward the Milky Way despite the fact that space is expanding, causing most galaxies in the universe to grow farther and farther apart.
The new image reveals M33 to be surprising large – bigger than its visible-light appearance would suggest. With its ability to detect cold, dark dust, Spitzer can see emission from cooler material well beyond the visible range of M33’s disk. Exactly how this cold material moved outward from the galaxy is still a mystery, but winds from giant stars or supernovas may be responsible.
The image is a three-color composite showing infrared observations from two of Spitzer instruments. Stars appear as glistening blue gems (several of which are actually foreground stars in our own galaxy), while dust rich in organic molecules glows green. The diffuse orange-red glowing areas indicate star-forming regions, while small red flecks outside the spiral disk of M33 are probably distant background galaxies.
As for the technical details, the blue parts of the image represents combined 3.6- and 4.5-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.
Earlier this week, the Hubble Space Telescope photographed the winning target in the Space Telescope Science Institute’s “You Decide” competition in celebration of the International Year of Astronomy.
The winning object, above, received 67,021 votes out of the nearly 140,000 votes cast for the six candidate targets.
Arp 274, also known as NGC 5679, is a system of three galaxies that appear to be partially overlapping in the image, although they may be at somewhat different distances. The spiral shapes of two of these galaxies appear mostly intact. The third galaxy (to the far left) is more compact, but shows evidence of star formation.
Two of the three galaxies are forming new stars at a high rate. This is evident in the bright blue knots of star formation that are strung along the arms of the galaxy on the right and along the small galaxy on the left.
The largest component is located in the middle of the three. It appears as a spiral galaxy, which may be barred. The entire system resides at about 400 million light-years away from Earth in the constellation Virgo.
Hubble’s Wide Field Planetary Camera 2 was used to image Arp 274. Blue, visible, and infrared filters were combined with a filter that isolates hydrogen emission. The colors in this image reflect the intrinsic color of the different stellar populations that make up the galaxies. Yellowish older stars can be seen in the central bulge of each galaxy. A bright central cluster of stars pinpoint each nucleus. Younger blue stars trace the spiral arms, along with pinkish nebulae that are illuminated by new star formation. Interstellar dust is silhouetted against the starry population. A pair of foreground stars inside our own Milky Way are at far right.
The International Year of Astronomy is the celebration of the 400th anniversary of Galileo’s first observations with a telescope. The ongoing “100 Hours of Astronomy,” April 2 to 5, is part of the fun, geared toward encouraging as many people as possible to experience the night sky.
Image credit: NASA, ESA, and M. Livio and the Hubble Heritage Team (STScI/AURA)
The clustering pattern of about 100,000 nearby galaxies, revealed by the 6dF Galaxy Survey. Each galaxy is shown as a dot. The galaxy we live in is at the centre of the pattern. Credit: Dr Chris Fluke, Centre for Astrophysics and Supercomputing, Swinburne University of Technology.
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A new detailed map of the nearby Universe reveals not only where local galaxies are currently, but where they are heading, how fast and why. “It’s like taking a snapshot of wildebeest on the African plain,” said Dr. Heath Jones of the Anglo-Australian Observatory (AAO), lead scientist for the Six-Degree Field Galaxy Survey (6dFGS), the most detailed survey of nearby galaxies to date. “We can tell which waterholes they’re heading to, and how fast they’re traveling.”
The project was a collaboration between astronomers from Australia, the UK and the USA. The survey was carried out with the 1.2-m UK Schmidt Telescope, which is operated by Siding Spring Observatory in New South Wales, Australia. Broader and shallower than previous comparable surveys (it covered twice as much sky as the Sloan Digital Sky Survey) it has recorded the positions of more than 110,000 galaxies over more than 80% of the Southern sky, out to about two thousand million light-years from Earth, (a redshift of 0.15).
Galaxies are tugged around by each other’s gravity. By measuring the galaxies’ movements, the researchers were able to map the gravitational forces at work in the local Universe, and so show how matter, both seen and unseen, is distributed.
Giant superclusters of galaxies are huge concentrations of mass, but they can’t be weighed accurately by looking at their light alone.
“Light can be obscured, but you can’t hide gravity,” said Dr. Jones.
The UK Schmidt Telescope. Photo: Shaun Amy
The survey shows strings and clusters of nearby galaxies on large scales in unprecedented detail, and has revealed more than 500 voids—”empty” areas of space with no galaxies.
The special aspect of this survey is that it will let the researchers disentangle two causes of galaxy movements.
As well as being pulled on by gravity, galaxies also ride along with the overall expansion of the Universe.
For about 10% of their galaxies, the 6dFGS researchers will tease apart these two velocity components: the one associated with the Universe’s expansion, and the one representing a galaxy’s individual, “peculiar”, motion.
“The peculiar velocities collected as part of this survey number more than five times as many as in any previous survey,” said Professor Elaine Sadler of the University of Sydney, a 6dFGS team member.
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Reminiscent of a telethon or a community fundraiser, Galaxy Zoo has challenged the public to complete one million classification clicks of galaxies from the Sloan Digital Sky Survey during the 100 Hours of Astronomy. The clock started ticking at 12:00 GMT on Wednesday, April 1st, with the challenge ending at 16:00 GMT on Sunday April 5th. The Galaxy Zoo site even includes a thermometer-like gadget called the Zoonometer to provide up-to-the minute ticks on the number of clicks. If you have just returned from a cave on Mars and haven’t heard of Galaxy Zoo, or if you don’t know what the 100 Hours of Astronomy is about, keep reading. Otherwise, head on over to Galaxy Zoo and start clicking!
Galaxy Zoo was launched in July 2007, with a data set of a million galaxies, imaged with a robotic telescope, the Sloan Digital Sky Survey. In order to understand how these galaxies formed, the idea was to get the public to help classify them according to their shapes. The human brain can do this task better than even the fastest computer. With so many galaxies, the team thought that it might take at least two years for visitors to the site to work through them all. Within 24 hours of launch, the site was receiving 70,000 classifications an hour, and more than 50 million classifications were received by the project during its first year, from almost 150,000 people. With the public’s help the Zoo team has published six papers from the findings, and have received viewing time with other, bigger telescopes to clarify the discoveries.
Zoo 2 launched a few months ago, and focuses on the nearest, brightest and most beautiful galaxies, and asks users to make more detailed classifications.
100 Hours of Astronomy is an event of the International Year of Astronomy that wants to get as many people as possible to look through a telescope – just as Galileo did 400 years ago. This four-day event encompasses astronomy clubs, groups, individuals, observatories, science centers and more around the world as they reach out to the public to achieve this common goal. There’s lots of great events, so check out Tammy’s article to find out more, or check out the 100 Hours of Astronomy website – but hurry – you’ve only got until Sunday April 5th to participate!
New research is casting doubt on the prevailing view that the heaviest galaxies in the universe started out small and gained mass by devouring other matter that ventured too close.
Peering at galaxies two-thirds of the way back in time to the Big Bang, an international team of astronomers is suggesting that some of the giants we see today were just as massive in that earlier age as they are now.
The new findings were released today in the journal Nature.
Lead author Chris Collins, an astronomer at the United Kindgdom’s Liverpool John Moores University, and his colleagues made their discovery using one of the largest optical telescopes in the World, called Subaru (named after the Japanese word for the Pleiades star cluster), located on the Island of Hawaii and owned by the National Observatory of Japan.
They focused on brightest cluster galaxies (BCGs), located at the centers of galaxy clusters. The massive galaxies constitute a separate population from bright elliptical galaxies, and both their predictability and extreme luminosity have motivated their use as standard candles for cosmology, the authors point out.
Analysing the light from these remote galaxies, the astronomers effectively weighed them and found that despite feeding on a constant diet of small galaxies, the heaviest galaxies have not increased their weight over the last 9 billion years. In a universe whose age is 13.7 billion years old, these results spark a debate as to how these galaxies put on so much weight in the first few billion years after the Big Bang.
“Current predictions using simulations run on super computers suggest that at such a young age these galaxies should be only 20 percent of their final weight, so to find galaxies so large suggests that galaxy formation is a much more rapid process than we previously thought,” Collins said, “and perhaps the theories are missing some important physics.”
John Stott, Collin’s colleague at LJMU and a co-author on the paper, said the team was “surprised to find that the largest and brightest galaxies in the Universe have remained essentially unchanged for the last 9 billion years, having grown rapidly soon after the Big Bang.”
One possibility being considered is that the galaxies formed by the collapse of an already massive cloud at the dawn of the universe.
MORE ABOUT LEAD IMAGE: The image shows the central 1.5 x 1.5 arc min of the cluster corresponding to 0.75 Mpc at this distance. The clusters X-ray emission is used to pinpoint the location of the brightest galaxy in the cluster as shown by the green contours which represent the X-ray intensity as measured by the XMM-Newton X-ray satellite.
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A new class of galaxy clusters has been identified by volunteers and astronomers of the Galaxy Zoo project, together with the Sloan Digital Sky Survey. These clusters are rare, and have apparently gone unnoticed before, despite their unusual linear properties. Astronomers believe the identification of these types of clusters depend on the visual inspection of large numbers of galaxies, a feat which has only recently been made possible by the Galaxy Zoo project, and this may explain why they haven’t been discovered until now. “Space is, after all, really big,” said the Galaxy Zoo scientists, “and full of really surprising things.”
These clusters are unusually elongated, possess young and highly dynamic galaxy populations, and most unexpectedly, present neatly typeset, left-justified, messages written in the English language. One sample even includes punctuation similar to an exclamation mark. (See image below.) SDSS colour composite image (vri) for another unusual galaxy cluster, at RA = ?2h61m12s, Dec = +124?17?72?? , identified by Galaxy Zoo participants.
The occurrence of these new galaxy phenomena could potentially lend support to some of the more exotic models for Dark Energy or modified gravity, which one of the Universe Today trolls may find extremely notable. More controversially, as most occurrences of English sentences are considered to be the work of intelligent beings, the existence of these messages might indicate intelligent life beyond our own.
Conversely, however, they could indicate that many phenomena usually attributed to intelligent life on Earth may actually occur spontaneously, without any thought necessarily being involved at all. While these new discoveries may have profound implications for cosmology, the most important thing to consider is the date of this publication, being April 1.
The Galaxy Zoo team stresses that, despite their implausible appearance, the galaxies comprising each individual character in the figures presented here are taken directly from the SDSS multicolour composite imaging. Note, however, that some degree of translation and rotation has been performed to the individual characters, for presentation purposes.
This image of a pair of colliding galaxies called NGC 6240 shows them in a rare, short-lived phase of their evolution just before they merge into a single, larger galaxy. Image credit: NASA/JPL-Caltech/STScI-ESA
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An imminent collision of biblical proportions has been captured by the Hubble and Spitzer Space Telescopes. The image here offers a rare view of a collision about to happen between the cores of two merging galaxies, each powered by a black hole with millions of times the mass of the sun. Already this union is considered to be one galaxy: NGC 6240, located 400-million light years away in the constellation Ophiuchus. Millions of years ago, each core was the dense center of its own galaxy before the two galaxies collided and ripped each other apart. Now, these cores are approaching each other at tremendous speeds and preparing for the final cataclysmic collision. They will crash into each other in a just a few million years.
“One of the most exciting things about the image is that this object is unique,” said Stephanie Bush of the Harvard-Smithsonian Center for Astrophysics, Cambridge, Mass., lead author of a new paper describing the observation in an upcoming issue of the Astrophysical Journal. “Merging is a quick process, especially when you get to the train wreck that is happening. There just aren’t many galactic mergers at this stage in the nearby universe.”
Download and extra-large version of this image here.
It combines visible light from NASA’s Hubble Space Telescope and infrared light from Spitzer. It catches the two galaxies during a rare, short-lived phase of their evolution, when both cores of the interacting galaxies are still visible but closing in on each other fast.
NGC 6240 is already putting out huge amounts of infrared light, an indication that a burst of star formation is underway. The extra infrared radiation is common in interacting galaxies; as the two galaxies interact, dust and gas swept up by the collision form a burst of new stars that give off infrared light. Such galaxies are called luminous infrared galaxies. Spitzer’s infrared array camera can image the extra heat from newly formed stars, even though their visible light is obscured by thick dust clouds around them.
The blob-like shape of the galaxy is due to the sustained violence of the collision. Streams of millions of stars are being ripped off the galaxy, forming wispy “tidal tails” that lead off NGC 6240 in several directions. But things are about to get even more violent as the main event approaches and the two galactic cores meld into one.
In the center of NGC 6240, the two black holes in the cores will whip up a frenzy of radiation as they careen towards one another head-on, likely transforming the galaxy into a monster known as an ultra-luminous infrared galaxy, thousands of times as bright in infrared as our Milky Way.
Another fascinating aspect of this rare object is that no two galactic mergers are the same. “Not only are there few objects at this stage, but each object is unique because it came from different progenitor galaxies,” said Bush. “These observations give us another layer of information about this galaxy, and galactic mergers in general.”
Infrared light taken by Spitzer’s infrared array camera at 3.6 and 8.8 microns (red) shows cold dust and radiation from star formation; visible light from Hubble (green and blue) shows hot gas and stars.
The ‘peculiar galaxy’ Arp 261 has been imaged in unprecedented detail, revealing two galaxies in a slow motion — but highly chaotic and disruptive — close encounter.
Arp 261 lies about 70 million light-years distant in the constellation of Libra, the Scales. The new close-up was captured by the ESO’s Very Large Telescope, at the Paranal Observatory in Chile.
Although individual stars are very unlikely to collide in such an interaction, the huge clouds of gas and dust certainly do crash into each other at high speed, leading to the formation of bright new clusters of very hot stars that are clearly seen in the picture. The paths of the existing stars in the galaxies are also dramatically disrupted, creating the faint swirls extending to the upper left and lower right of the image. Both interacting galaxies were probably dwarfs not unlike the Magellanic Clouds orbiting our own galaxy.
Arp 261 is listed in Halton Arp’s catalogue of Peculiar Galaxies that appeared in the 1960s, with the goal of chronicling objects in the sky that appear strange and may tell rewarding science stories.
The images used to create the new picture of Arp 261 were not actually taken to study the interacting galaxies at all, but to investigate the properties of the inconspicuous object just to the right of the brightest part of Arp 261 and close to the center of the image. This is an unusual exploding star, called SN 1995N, that is thought to be the result of the final collapse of a massive star at the end of its life, a so-called core collapse supernova. SN 1995N is unusual because it has faded very slowly — and still shows clearly more than seven years after the explosion took place.
SN 1995N is also one of the few supernovae to have been observed to emit X-rays. It is thought that these unusual characteristics are a result of the exploding star being in a dense region of space so that the material blasted out from the supernova plows into it and creates X-rays.
Apart from the interacting galaxy and its supernova, the image also contains several other objects at wildly different distances from us. Starting very close to home, two small asteroids, in our Solar System between the orbits of Mars and Jupiter, happened to cross the images as they were being taken and show up as the red-green-blue trails at the left and top of the picture. The trails arise as the objects are moving during the exposures and also between the exposures through different colored filters. The asteroid at the top is number 14670 and the one to the left number 9735. They are probably less than 5 km (3 miles) across. The reflected sunlight from these small bodies takes about 15 minutes to reach Earth.
The next closest object is probably the apparently bright star at the bottom. It may look bright, but it is still about one hundred times too faint to be seen with the unaided eye. It is most likely a star rather like the Sun and about 500 light-years from us — 20 million times further away than the asteroids. Arp 261 itself, and the supernova, are about 140,000 times farther away than this star, but still in what astronomers would regard as our cosmic neighborhood. Much more distant still, perhaps some fifty to one hundred times further away than Arp 261, lies the cluster of galaxies visible on the right of the picture.
Videos of the unusual system are available here and here.
NASA/ESA Hubble Space Telescope images of the three galaxies studied by a team of astronomers who try to understand how galaxies formed when the Universe was half its current age (upper panels). The same galaxies were then studied with the FLAMES/GIRAFFE instrument on ESO’s Very Large Telescope (VLT) to probe the motions of gas in these objects (lower panels). P
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Once upon a time, before our Sun and Earth existed, distant galaxies were being created. Because this happened so long ago, astronomers know very little about how these galaxies formed. But now, by combining the Hubble Space Telescope’s acute vision with the Very Large Telescope’s spectrograph, astronomers have obtained exceptional 3-D views of distant galaxies, seen when the Universe was half its current age. By looking at this unique “history book” of our Universe, scientists hope to solve the puzzle of how galaxies formed in the remote past.
Hubble allows fine details of galaxies to be seen, while the VLT’s FLAMES/GIRAFFE spectrograph can obtain simultaneous spectra from small areas of extended objects, and resolving the motions of the gas in these distant galaxies.
“This unique combination of Hubble and the VLT allows us to model distant galaxies almost as nicely as we can close ones,” said François Hammer, who led the team. “In effect, FLAMES/GIRAFFE now allows us to measure the velocity of the gas at various locations in these objects. This means that we can see how the gas is moving, which provides us with a three-dimensional view of galaxies halfway across the Universe.”
The team has been reconstructing the history of about one hundred remote galaxies that have been observed with both Hubble and GIRAFFE on the VLT. The first results are coming in and have already provided useful insights for three galaxies. Combining the twin strengths of the NASA/ESA Hubble Space Telescope’s acute eye, and the capacity of ESO’s Very Large Telescope (VLT) to probe the motions of gas in tiny objects. Credit: ESO
In one galaxy, GIRAFFE revealed a region full of ionized gas, that is, hot gas composed of atoms that have been stripped of one or several electrons. This is normally due to the presence of very hot, young stars. However, even after staring at the region for more than 11 days, Hubble did not detect any stars! “Clearly this unusual galaxy has some hidden secrets,” said Mathieu Puech, lead author of one of the papers reporting this study. Comparisons with computer simulations suggest that the explanation lies in the collision of two very gas-rich spiral galaxies. The heat produced by the collision would ionise the gas, making it too hot for stars to form.
Another galaxy that the astronomers studied showed the opposite effect. There they discovered a bluish central region enshrouded in a reddish disc, almost completely hidden by dust. “The models indicate that gas and stars could be spiralling inwards rapidly,” said Hammer. This might be the first example of a disc rebuilt after a major merger.
Finally, in a third galaxy, the astronomers identified a very unusual, extremely blue, elongated structure — a bar — composed of young, massive stars, rarely observed in nearby galaxies. Comparisons with computer simulations showed the astronomers that the properties of this object are well reproduced by a collision between two galaxies of unequal mass.
“The unique combination of Hubble and FLAMES/GIRAFFE at the VLT makes it possible to model distant galaxies in great detail, and reach a consensus on the crucial role of galaxy collisions for the formation of stars in a remote past,” says Puech. “It is because we can now see how the gas is moving that we can trace back the mass and the orbits of the ancestral galaxies relatively accurately. Hubble and the VLT are real ‘time machines’ for probing the Universe’s history,” added Sébastien Peirani, lead author of another paper reporting on this study.
The astronomers are now extending their analysis to the whole sample of galaxies observed. “The next step will then be to compare this with closer galaxies, and so, piece together a picture of the evolution of galaxies over the past six to eight billion years, that is, over half the age of the Universe,” said Hammer.
