All-Sky Radio Image in 60 Seconds, No Moving Parts

This image is a software-calibrated image with high signal-to-noise ratio at a frequency of 120 MHz, of the radio sky above Effelsberg, Germany, on November10, 2009. It has North at the top and East at the left, just as a person would have seen the entire sky when lying on their back on a flat field near Effelsberg late in the afternoon on November 10, if their eyes were sensitive to radio waves.

The two bright (yellow) spots are Cygnus A – a giant radio galaxy powered by a supermassive black hole – near the center of the image, and Cassiopeia A – a bright radio source created by a supernova explosion about 300 years ago – at the upper-left in the image. The plane of our Milky Way galaxy can also be seen passing by both Cassiopeia A and Cygnus A, and extending down to the bottom of the image. The North Polar Spur, a large cloud of radio emission within our own galaxy, can also be seen extending from the direction of the Galactic center in the South, toward the western horizon in this image. “We made this image with a single 60 second “exposure” at 120 MHz using our high-band LOFAR field in Effelsberg”, says James Anderson, project manager of the Effelsberg LOFAR station.

“The ability to make all-sky images in just seconds is a tremendous advancement compared to existing radio telescopes which often require weeks or months to scan the entire sky,” Anderson went on. This opens up exciting possibilities to detect and study rapid transient phenomena in the universe.

LOFAR, the LOw Frequency ARray, was designed and developed by ASTRON (Netherlands Institute for Radio Astronomy) with 36 stations centered on Exloo in the northeast of The Netherlands. It is now an international project with stations being built in Germany, France, the UK and Sweden connected to the central data processing facilities in Groningen (NL) and the ASTRON operations center in Dwingeloo (NL). The first international LOFAR station (IS-DE1) was completed on the area of the Effelsberg radio observatory next to the 100-m radio telescope of the Max-Planck-Institut für Radioastronomie (MPIfR).

Operating at relatively low radio frequencies from 10 to 240 MHz, LOFAR has essentially no moving parts to track objects in the sky; instead digital electronics are used to combine signals from many small antennas to electronically steer observations on the sky. In certain electronic modes, the signals from all of the individual antennas can be combined to make images of the entire radio sky visible above the horizon.

IS-DE1: Some of the 96 low-band dipole antennas, Effelsberg LOFAR station (foreground); high-band array (background) (Credit: James Anderson, MPIfR)

LOFAR uses two different antenna designs, to observe in two different radio bands, the so-called low-band from 10 to 80 MHz, and the high-band from 110 to 240 MHz. All-sky images using the low-band antennas at Effelsberg were made in 2007.

Following the observation for the first high-band, all-sky image, scientists at MPIfR made a series of all-sky images covering a wide frequency range using both the low-band and high-band antennas at Effelsberg.

Effelsberg sky through LOFAR eyes (Credit: James Anderson, MPIfR)

The movie of these all-sky images has been compiled and is shown above. The movie starts at a frequency of 35 MHz, and each subsequent frame is about 4 MHz higher in frequency, through 190 MHz. The resolution of the Effelsberg LOFAR telescope changes with frequency. At 35 MHz the resolution is about 10 degrees, at 110 MHz it is about 3.4 degrees, and at 190 MHz it is about 1.9 degrees. This change in resolution can be seen by the apparent size of the two bright sources Cygnus A and Cassiopeia A as the frequency changes.

Scientists at MPIfR and other institutions around Europe will use measurements such as these to study the large-sky structure of the interstellar matter of our Milky Way galaxy. The low frequencies observed by LOFAR are ideal for studying the low energy cosmic ray electrons in the Milky Way, which trace out magnetic field structures through synchrotron emission. Other large-scale features such as supernova remnants, star-formation regions, and even some other nearby galaxies will need similar measurements from individual LOFAR telescopes to provide accurate information on the large-scale emission in these objects. “We plan to search for radio transients using the all-sky imaging capabilities of the LOFAR telescopes”, says Michael Kramer, director at MPIfR, in Bonn. “The detection of rapidly variable sources using LOFAR could lead to exciting discoveries of new types of astronomical objects, similar to the discoveries of pulsars and gamma-ray bursts in the past decades.”

“The low-frequency sky is now truly open in Effelsberg and we have the capability at the observatory to observe in a wide frequency range from 10 MHz to 100 GHz”, says Anton Zensus, also director at MPIfR. “Thus we can cover four orders of magnitude in the electromagnetic spectrum.”

Source: Max-Planck-Institut für Radioastronomie

Milky Way Has a “Squashed Beachball”-Shaped Dark Matter Halo

This illustration shows the visible Milky Way galaxy surrounded by a "squashed beachball"-shaped dark matter halo. Source: UCLA

This illustration shows the visible Milky Way galaxy surrounded by a “squashed beachball”-shaped dark matter halo. Source: UCLA

Our galaxy is shaped like a flat spiral right? Not if you’re talking about dark matter. Astronomers announced today that the Milky Way’s dark matter halo, which represents about 70% of the galaxy’s mass, is actually shaped like a squashed beachball.

Dark matter is completely invisible, but it still obeys the law of gravity, so the existence of dark matter haloes, and their shape, can be inferred by monitoring the orbits of dwarf galaxies orbiting the much larger Milky Way.

Unfortunately, to determine the orbit of an object, you have to measure its position at several points in that orbit, and dwarf galaxies take about a billion years to go around the Milky Way. Astronomers just haven’t been around long enough to watch even a fraction of a complete orbit. Luckily, they don’t have to.

Dwarf galaxies, just like their full-sized counterparts, and made of billions of stars. When the tidal forces from a big galaxy like the Milky Way act on a dwarf galaxy, the result is a streamer of stars that trace out the dwarf galaxy’s orbit. By using data from huge all-sky surveys, a group of astronomers led by David Law at UCLA were able to reconstruct the orbit of the Sagittarius Dwarf Galaxy. There was just one problem: different parts of the dwarf galaxy had different orbits, which led to wildly different dark matter halo shapes.

Law and his colleagues Steven Majewski (University of Virginia) and Kathryn Johnston (Columbia University) solved this problem by allowing models of the dark matter halo to be “triaxial” – in other words, have different lengths in all three dimensions. The best model solution results in a halo shaped like a beach ball that has been squashed sideways.

“We expected some amount of flattening based on the predictions of the best dark-matter theories,” said Law, “but the extent, and particularly the orientation, of the flattening was quite unexpected. We’re pretty excited about this, because it begs the question of how our galaxy formed in its present orientation.”

Sagittarius is not the only dwarf galaxy orbiting the Milky Way, and Law and his colleagues plan to study the orbits of other dwarf galaxies to refine their model. “It will be important to see if these results hold up as precise orbits are measured for more of these galaxies. In the meantime, such a squashed dark-matter halo is one of the best explanations for the observed data.”

This illustration shows the visible Milky Way galaxy (blue spiral) and the streams of stars represent the tidally shredded Sagittarius dwarf galaxy. Click the image for a flyaround view. Source: UCLA

This illustration shows the visible Milky Way galaxy (blue spiral) and the streams of stars represent the tidally shredded Sagittarius dwarf galaxy. Source: UCLA

Get the Big Picture of the Milky Way at the Adler Planetarium

Astronomy is all about getting the big picture of our place in the cosmos, but some pictures are bigger than others. This one is really big. The world’s largest image of our Milky Way galaxy went on display today at the Adler Planetarium in Chicago. The image spans an area of 37 meters (120 feet) long by 1 meter (3 feet) wide at its sides, bulging to 2 meters (6 feet) to show the center of our humongous galaxy. The panorama represents 800,000 separate images taken by the Spitzer Space Telescope over a five-year period.

“This is the highest-resolution, largest, most sensitive infrared picture ever taken of our Milky Way,” said Sean Carey of NASA’s Spitzer Science Center, speaking when the image was unveiled in 2008 at the American Astronomical Society meeting in St. Louis (see our article and image of the unveiling). “Where previous surveys saw a single source of light, we now see a cluster of stars. With this data, we can learn how massive stars form, map galactic spiral arms and make a better estimate of our galaxy’s star-formation rate.”

Spitzer Survey image compiled.  Credit: NASA/JPL
Spitzer Survey image compiled. Credit: NASA/JPL

Data from Spitzer’s Infrared Array Camera (IRAC) and the Multiband Imaging Photometer were used to create the image.

If you want to download a very large version of this image (2400 x 3000) click here — warning: very big file.

From our vantage point on Earth, we see the Milky Way as a blurry, narrow band of light that stretches across the sky. In the visible, we only see about 5% of what’s actually out there. But with Spitzer’s dust-piercing infrared eyes, astronomers have peered 60,000 light-years away into this fuzzy band, called the galactic plane, and saw all the way to the other side of the galaxy.

The panorama reveals star formation as never seen before on both the large and small scale. Most of the star forming regions had not been seen before this project was undertaken.

I had the good fortune of seeing the image in St. Louis, and I highly recommend taking the opportunity to go see it at the Adler Planetarium if you are in Chicago. Here’s a video that explains how astronomers took the images and put them all together to form this gigantic panorama.

*Serendipitously, I am currently at the dotAstronomy conference where Eli Bressert from the Chandra X-Ray Center talked about the GLIMPSE Viewer. Here’s the link to see the Spitzer image with GLIMPSE (Galactic Legacy Infrared Midplane Extraordinaire).

Adler Planetarium is located at 1300 South Lake Shore Drive, Chicago, Ill., 60605. Phone: 312-922-7827. Adler Planetarium website. .

Astronomers Dig Up Relic of the Milky Way’s Central Bulge


Like archaeologists who dig through the layers of dirt to unearth crucial pieces of the history of mankind, astronomers have been gazing through the thick layers of interstellar dust obscuring the central bulge of the Milky Way and have unveiled an extraordinary cosmic relic. Within the bulge is an unusual mix of stars in the stellar grouping known as Terzan 5, and such a mix has never been observed anywhere in the bulge before. This peculiar conglomeration of stars suggests that Terzan 5 is one of the bulge’s primordial building blocks, most likely the relic of a dwarf galaxy that merged with the Milky Way during its very early days.

The new observations of Terzan 5 show that this object, unlike all but a few exceptional globular clusters, does not harbor stars which are all born at the same time — what astronomers call a “single population” of stars. Instead, the multitude of glowing stars in Terzan 5 formed in at least two different epochs, the earliest probably some 12 billion years ago and then again 6 billion years ago.

Dust around Terzan 5. Credit: ESO
Dust around Terzan 5. Credit: ESO

“Only one globular cluster with such a complex history of star formation has been observed in the halo of the Milky Way: Omega Centauri,” says team member Emanuele Dalessandro. “This is the first time we see this in the bulge.”

Using ESO’s Very Large Telescope, equipped with the Multi-conjugate Adaptive Optics Demonstrator (MAD), the astronomers were able to “disperse the fog” of the dust clouds in the central bulge to reveal the myriad of stars.

Through the sharp eye of the VLT, the astronomers also found that Terzan 5 is more massive than previously thought: along with the complex composition and troubled star formation history of the system, this suggests that it might be the surviving remnant of a disrupted dwarf galaxy, which merged with the Milky Way during its very early stages and thus contributed to form the galactic bulge.

The team hopes this is only the first in a series of discoveries on the origin of bulges in galaxies.

“The history of the Milky Way is encoded in its oldest fragments, globular clusters and other systems of stars that have witnessed the entire evolution of our galaxy,” says Francesco Ferraro, lead author of a paper appearing in this week’s issue of the journal Nature. “Our new study opens a new window on yet another piece of our galactic past.”

Source: ESO

1 Milky Way; 3,000 Images

What a gorgeous and immense image! And it’s full of stars! An astronomer from Central Michigan University has put together a new high-resolution panoramic image of the full night sky , with the Milky Way galaxy as its centerpiece. Axel Mellinger stitched together over 3,000 images to create this beautiful image, which also comes in an interactive version, showing stars 1,000 times fainter than the human eye can see, as well as hundreds of galaxies, star clusters and nebulae.

View an interactive version at Mellinger’s website.

Mellinger spent 22 months and traveled over 26,000 miles to take digital photographs at dark sky locations in South Africa, Texas and Michigan. After the photographs were taken, “the real work started,” Mellinger said.

Simply cutting and pasting the images together into one big picture would not work. Each photograph is a two-dimensional projection of the celestial sphere. As such, each one contains distortions, in much the same way that flat maps of the round Earth are distorted. In order for the images to fit together seamlessly, those distortions had to be accounted for. To do that, Mellinger used a mathematical model—and hundreds of hours in front of a computer.

Another problem Mellinger had to deal with was the differing background light in each photograph.

“Due to artificial light pollution, natural air glow, as well as sunlight scattered by dust in our solar system, it is virtually impossible to take a wide-field astronomical photograph that has a perfectly uniform background,” Mellinger said.

To fix this, Mellinger used data from the Pioneer 10 and 11 space probes. The data allowed him to distinguish star light from unwanted background light. He could then edit out the varying background light in each photograph. That way they would fit together without looking patchy.

The result is an image of our home galaxy that no star-gazer could ever see from a single spot on earth. Mellinger plans to make the giant 648 megapixel image available to planetariums around the world.

Source: EurekAlert

Herschel Sees Hidden Stars in the Southern Cross


Science observations have begun in earnest for the Herschel Space Telescope, and this spectacular image is the first produced by combining data from two cameras aboard Herschel, the Spectral and Photometric Imaging REceiver (SPIRE), and the Photoconductor Array Camera and Spectrometer (PACS). It shows a tumultuous region in the Southern Cross, visible only because the instruments are tuned to “see” in five different infrared wavelengths. Stunning vistas of cold gas clouds lying near the plane of the Milky Way reveal intense, unexpected activity. The dark, cool region is dotted with stellar factories, like pearls on a cosmic string.

Herschel, one of the largest telescopes in space, was launched in May. For this image, the two instruments were aimed at an area in the plane of the Milky Way about 60° from its center. It covers around 16 times the area of the Full Moon as seen in the sky.

The images were taken on September 3, 2009 during the first trial run with the two instruments working together. Herschel will go on to survey large areas of our galaxy.

Herschel SPIRE (left) and PACS images.  Credit:  ESA
Herschel SPIRE (left) and PACS images. Credit: ESA

The five original infrared wavelengths have been color-coded to allow scientists to differentiate extremely cold material (red) from the surrounding, slightly warmer stuff (blue).

The images reveal structure in cold material in our Galaxy, as we have never seen it before, and even before a detailed analysis, scientists have gleaned information on the quantity of the material, its mass, temperature, composition and whether it is collapsing to form new stars.

Beautiful evidence that our galaxy keeps giving birth to new generations of stars!

Source: ESA

New Chandra Deep X-ray Image of the Galactic Center

Chandra has done it again in creating some of the most visually stunning images of our Universe. This time, Chandra’s X-ray eyes show a dramatic new vista of the center of the Milky Way galaxy. This mosaic from 88 different images exposes new levels of the complexity and intrigue in the Galactic center, providing a look at stellar evolution, from bright young stars to black holes, in a crowded, hostile environment dominated by a central, supermassive black hole.

Permeating the region is a diffuse haze of X-ray light from gas that has been heated to millions of degrees by winds from massive young stars – which appear to form more frequently here than elsewhere in the Galaxy – explosions of dying stars, and outflows powered by the supermassive black hole – known as Sagittarius A* (Sgr A*). Data from Chandra and other X-ray telescopes suggest that giant X-ray flares from this black hole occurred about 50 and about 300 years earlier.

See this link for an animation that provides greater detail of the galactic center.

The area around Sgr A* also contains several mysterious X-ray filaments. Some of these likely represent huge magnetic structures interacting with streams of very energetic electrons produced by rapidly spinning neutron stars or perhaps by a gigantic analog of a solar flare.

Scattered throughout the region are thousands of point-like X-ray sources. These are produced by normal stars feeding material onto the compact, dense remains of stars that have reached the end of their evolutionary trail – white dwarfs, neutron stars and black holes.

Because X-rays penetrate the gas and dust that blocks optical light coming from the center of the galaxy, Chandra is a powerful tool for studying the Galactic Center. This image combines low energy X-rays (colored red), intermediate energy X-rays (green) and high energy X-rays (blue).

The image is being released at the beginning of the “Chandra’s First Decade of Discovery” symposium being held in Boston, Mass. This four-day conference will celebrate the great science Chandra has uncovered in its first ten years of operations. To help commemorate this event, several of the astronauts who were onboard the Space Shuttle Columbia – including Commander Eileen Collins – that launched Chandra on July 23, 1999, will be in attendance.

Source: Chandra

Milky Way Galaxy Pictures

Here are some beautiful pics of the Milky Way Galaxy. It’s important to remember that we live inside the Milky Way Galaxy, so there’s no way to show a true photograph of what the Milky Way looks like. We can see pictures of the Milky Way from inside it, or see artist illustrations of what the Milky Way might look like from outside.


This Milky Way Galaxy picture shows what our galaxy would look like from above. You can see its spiral arms, dense core and the thin halo. The Milky Way is a common barred spiral galaxy. There are billions more just like it in the Universe.

Milky Way in infrared. Image credit: COBE
Milky Way in infrared. Image credit: COBE

This picture of the Milky Way was captured by NASA’s COBE satellite. This photograph was taken using the infrared spectrum, which allows astronomers to peer through the gas and dust that normally obscures the center of the Milky Way.

The plane of the Milky Way, recorded with the Chandra satellite in three colours: Photons with energies between 0.5 and 1keV appear red, those between 1 and 3keV green, and those between 3 and 7keV blue. Discrete sources are indicated by circles.  Image: Mikhail Revnivtsev
The plane of the Milky Way, recorded with the Chandra satellite in three colours: Photons with energies between 0.5 and 1keV appear red, those between 1 and 3keV green, and those between 3 and 7keV blue. Discrete sources are indicated by circles. Image: Mikhail Revnivtsev

This image of the Milky Way Galaxy was taken with the Chandra X-Ray Observatory, which can see in the X-Ray spectrum. In this view, only high energy emissions are visible, such as the radiation emitted from black holes and other high energy objects.

Artist's concept shows young, blue stars encircling a supermassive black hole at the core of a spiral galaxy like the Milky Way.Credit: NASA, ESA, and A. Schaller (for STScI)
Artist's concept shows young, blue stars encircling a supermassive black hole at the core of a spiral galaxy like the Milky Way.Credit: NASA, ESA, and A. Schaller (for STScI)

Here’s an artist’s impression of what a galaxy like the Milky Way might have looked like early in its history. This image shows a supermassive black hole with young blue stars circling it.

Milky_Way_infrared_mosaic.  Credit:  Spitzer Space Telescope
Milky_Way_infrared_mosaic. Credit: Spitzer Space Telescope

This is a mosaic image of the Milky Way captured by NASA’s Spitzer Space Telescope. It was built up by several photographs taken by Spitzer, which sees in the infrared spectrum, and can peer through obscuring dust.

Fate of the Universe

[/caption]What is the ultimate fate of our universe? A Big Crunch? A Big Freeze? A Big Rip? or a Big Bounce? Measurements made by WMAP or the Wilkinson Microwave Anisotropy Probe favor a Big Freeze. But until a deeper understanding of dark energy is established, the other three still cannot be totally ignored.

Ever since scientists proved the Big Bang to be the most plausible cosmological theory, and since it only focused more on how it might have all began, their attention started to shift to how the Universe would end. Thus, all 4 theories mentioned above (Big Crunch, Big Freeze, etc.) are actually offshoots of the Big Bang.

The Big Crunch predicts that, after having expanded to its maximum size, the Universe will finally collapse into itself to form the greatest black hole ever.

On the opposite side of the coin, the Big Freeze foretells of a universe that will continue to stretch forever, distributing heat evenly in the process until none is left to be usable enough. Hence, it is also known as the Heat Death.

A more dramatic version of the Big Freeze is the Big Rip. In this scenario, the Universe’s rate of expansion will increase substantially so that everything in it, down to the smallest atom, will be ripped apart.

In a cyclic or oscillatory model of the Universe, there will be no end … for matter and energy, that is. But for us and the Universe that we know of, there will definitely be a conclusion. In an oscillatory model, the Big Bang and Big Crunch form a pair known as the Big Bounce. Essentially, such a universe would simply expand and contract (or bounce) forever.

For astronomers to determine what the ultimate fate of the Universe should be, they would need to know certain information. Its density is supposedly one of the most telling.

You see, if its density is found to be less than the critical density, then only a Big Freeze or a Big Rip would be possible. On the other hand, if it is greater than the said critical value, then a Big Crunch or Big Bounce would most likely ensue.

The most accurate measurements on the cosmic microwave background radiation (CMBR), which is also the most persuasive evidence of the Big Bang, shows a universe having a density virtually equal to the critical density. The measurements also exhibit the characteristics of a flat universe. Right now, it looks like all gathered data indicate that a Big Crunch or a Big Bounce is highly unlikely to occur.

To render finality to these findings however, scientists will need to know the exact behavior of dark energy. Is its strength increasing? Is it diminishing? Is it constant? Only by answering these will they know the ultimate fate of the Universe.

We’ve got a few articles that touch on the fate the universe here in Universe Today. Here are two of them:

NASA also has some more:

Tired eyes? Let your ears help you learn for a change. Here are some episodes from Astronomy Cast that just might suit your taste:

Sources: NASA, Hubblesite

Center of the Universe

Where is the center of the Universe? One of the confusing aspects of the whole Big Bang idea is the notion that the Universe doesn’t have a center. You see, if we associate the Big Bang with just about any typical explosion, then we can be tempted to pinpoint the source of the explosion to be the center.

For example, if a firecracker explodes and we take a snapshot of it, then the outermost debris would mark the boundaries of the whole explosion. Looking at the directions of each debris, whether outermost or not, would give us an idea as to where the explosion first started and, subsequently, the center.

Furthermore, if there was a point of origin (the center) of the Big Bang similar to typical explosions, then that point and all regions near it would be comparatively warmer than all others. That is, as you move further from the center of a typical explosion, you would expect to measure cooler temperatures.

However, when scientists point their detectors to all directions, the readings they obtain indicate that the Universe, in general, is homogeneous. No large region is relatively warmer than the rest. Of course, each star is hotter than the regions away from it.

But if we look at many galaxies, and thus including the stars that comprise them, a homogeneous overall picture is painted. If that were so, then that center or point of origin of the explosion cannot exist.

The favorite analogy used by lecturers to simplify the concept of a universe having no center is that of the behavior of dots on the surface of an expanding balloon; for as we know, the Universe is expanding. If we imagine the dots to be galaxies, we can visualize the Universe’s expansion by observing how the dots are brought away from one another as air is slowly blown into the balloon.

For us to get a near accurate analogy, it is important that the observation be limited to the surface alone. If we try to interpret the expansion as being manifested by the whole balloon, we will be tempted into interpreting the geometric center of the balloon as the center of the expanding Universe.

Going back, if we just focus on the surface, you’ll notice that each and every dot will drift farther away from adjacent ones and that no single dot will appear as the center. Also, if you picture yourself as an ant at the center of a single dot, all the other dots will move away from you as if you were the center, just like in our universe.

We’ve got a few articles that touch on the center of the universe here in Universe Today. Here are two of them:

NASA also has some more:

Tired eyes? Let your ears help you learn for a change. Here are some episodes from Astronomy Cast that just might suit your taste:

Source: NASA Spitzer