Galaxies

Galaxies
Spiral galaxy NGC 3982. Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)

Hello, is there anyone out there? With all of the galaxies in the Universe, is it possible that there is cognizant life somewhere else? Well, I can not answer that question for you, but I can offer you a great deal of information about galaxies so that you can make your own informed decision on the matter.

Our’s is a spiral galaxy. A spiral galaxy is shaped like a flat disk with a thicker bulge in the center. Bright spiral arms start from the center and then coil outward like a pinwheel. All spirals rotate very slowly. The Milky Way completes a single revolution once every 250 million years.

Most galaxies are billions of years old. The youngest known galaxy is 1 Zwicky 18. At an estimated age of a mere 500 million years, it is a babe in diapers compared to the Milky Way at 10-14 billion years, which is the average age of the known galaxies.

Scientists think that galaxy formation was led by dark matter. This invisible material clumped together and it attracted regular mass with its gravity, channeling material together into larger and larger collections. This process of matter accretion led to the first proto-galaxies.

The Canis Major Dwarf Galaxy is the closest galaxy to ours. It is actually contained within the Milky Way and only 42,000 light years form the galactic core.

In the links below you will find thousands of facts, figures, and images that will help you understand many things about galaxies in general and some specific types. Enjoy your reading.

Confirmed: Chocolate and Astronomy Go Together

Chocolate astronomy sculpture. Credit: Museo de Chocolate.

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Two of my greatest loves are coming together at the Museo de Chocolate (Chocolate Museum) of Barcelona. To celebrate the International Year of Astronomy 2009, this year’s International Contest of Chocolate Figures has chosen astronomy as its theme. And the fourteen sculptures that are part of the competition –in which the designers use chocolate to embody creative astronomical interpretations, as the one seen here — will be on display at the Museo de Chocolate starting on May 7 in a new temporary exhibition, “Los Mundos Celestes-400 años del descubrimiento del sistema solar” (Celestial Worlds – 400 years since the discovery of the Solar System). I understand the exhibition as being temporary, but my question is, who gets to eat them?

Source: Pasteleria.com

Nearsighted No More: Astronomers Resolve Milky Way’s Mysterious X-Ray Glow

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The map above details the Galactic ridge X-ray emission, first detected 25 years ago and observed recently by NASA’s Rossi X-ray Timing Explorer (RXTE) observatory. The inset shows the zoomed Chandra image of the region, close to the center of the galaxy. 

The mysterious — and formerly blurry — X-ray source puzzled astronomers for a quarter century, but a new paper release today by the journal Nature has helped to clear the air.

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Region close to the Galactic Center obtained by Spitzer infrared telescope in three spectral band. The field of view of CHANDRA is shown by the white square. Credit: M. Revnivtsev

 

Lead author Mikhail Revnivtsev, of Munich Technical University in Garching, Germany, and his colleagues report that the formerly unresolved X-ray glow has a spectrum characteristic of a hot (100 million degrees Kelvin) optically thin plasma, with a prominent iron emission line.

But the gravitational well of the Galactic disk is far too shallow to confine such a hot interstellar medium; it would flow away at a velocity of a few thousand kilometers per second, exceeding the speed of sound in the gas.

Replenishing such energy losses would require a source that exceeds all plausible energy sources in the Milky Way — including supernovae — by orders of magnitude, they write.

Based on their observations, the team is proposing that the hot plasma is instead bound to many faint sources: plain old stars.

“Here we report that at energies of 6–7 keV, more than 80 percent of the seemingly diffuse X-ray emission is resolved into discrete sources, probably accreting white dwarfs and coronally active stars,” they write.

“Such stellar X-ray sources are of the common ‘garden variety’ in the Sun’s neighbourhood,” writes Michael Shull, an astrophysicist at the University of Colorado at Boulder, in an accompanying editorial. “However, at the distance of the Galactic ridge from Earth, their combined light becomes a diffuse blur, the X-ray equivalent of the many stars that make up the Milky Way, as Galileo first saw with his telescope in visible light.”

Shull notes that the results are a testament to the increased power of telescopes like Chandra, which de-mystified the source of the X-ray glow — and he cautions astronomers about describing faint backgrounds at all wavelengths, before getting a good look.

“As Revnivtsev and colleagues’ work demonstrates, sometimes the exotic explanation can be set aside by more accurate imaging and spectroscopy,” he writes.

LOWER IMAGE CAPTION: Region close to the Galactic Center obtained by Spitzer infrared telescope in three spectral band. The field of view of CHANDRA is shown by the white square. Credit: M. Revnivtsev

Source: Nature

In Your Eyes – The NGC 4486 Jet by JP Metsavainio

Parallel NGC 4486 Jet by JP Metsavainio

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We’re all familiar with the photo of the jet of material emanating from the core of the Virgo A galaxy as imaged by the Hubble Space Telescope, but this 5,000 light year long streamer coming from the nucleus of M87 has never been more “in your eyes” than it is through the stereo magic visualizations produced by Jukka Metsavainio. Are you ready to take a closer look at this relativistic jet of extremely powerful plasma emerging from one of the best studied radio galaxies around? Then step inside…

Whenever we present a dimensional visualization it is done in two fashions. The first is called “Parallel Vision” and it is much like a magic eye puzzle. When you open the full size image and your eyes are the correct distance from the screen, the images will seem to merge and create a 3D effect. However, for some folks, this doesn’t work well – so Jukka has also created the “Cross Version”, where you simply cross your eyes and the images will merge, creating a central image which appears 3D. As we learned with the last image, it might not always work for all people, but there are a few other tricks you can try. Now sit back and prepare to be blown away…

Cross NGC 4486 Jet by JP Metsavainio
Cross NGC 4486 Jet by JP Metsavainio

The year is 1918, and high on top of Mt. Hamilton at Lick Observatory an astronomer named Herbert Curtis is busy studying Messier Object 87. But, Mr. Curtis isn’t your ordinary garden-variety astronomer. In just two more years, he and a man named Harlow Shapely were going to have it out publicly about the nature of these “distant fuzzies” and Curtis was going to be eventually proved correct: Spiral “nebulae” were indeed galaxies just like our own. However, good old Herbert was noticing something about M87 that would take nearly 8 decades to discover its true nature… a “curious straight ray” coming straight from its heart. Now, you’ve got to give Herbert some very big credit for being an astute visual observer, because this was back in the day long before wide field imaging camera, infra-red technology, x-ray photography, radio studies and more. Heck, it would be 2 more years before Hubble began identifying Cepheid variables and 10 more years before interstellar absorption was discovered!

Are you ready to fast forward to 1977? Because it would be about that long before another noble name in galaxy studies would again reveal astonishing visual things about M87’s jet by resolving knots and clouds – Halton C. Arp of Mt. Palomar and J. Lorre of JPL. “The shred itself, however, is the object of most significance for establishing the reality of the ejection of the radio source. It is difficult to make a quantitative statement, but objects of this nature are not frequently seen. The inference is plain that the radio source has either left a wake behind it, (i.e. condensations along its track) or that this is some kind of jet or material associated with the ejection of the radio source form the parent peculiar galaxy.”

It wasn’t long until the discovery of a disk of rapidly rotating gas around the nucleus of M87 occurred and thanks to the Hubble Space telescope, we were taking closer than ever looks into the violent active nucleus of this galaxy. “We see almost a dozen clouds which appear to be moving out from the galaxy’s center at between four and six times the speed of light. These are all located in a narrow jet of gas streaming out from the region of the black hole at the galaxy’s center,” said Dr. John Biretta of the Space Telescope Science Institute. “We believe this apparent speed translates into an actual velocity just slightly below that of light itself.”

What we know now is the jet in M87 connects the innermost black hole to the outer parts of the source. It supplies the radio source and the surrounding region with energy and relativistic plasma. The speeds reported are two to three times faster than the fastest motions previously recorded in M87, the only nearby galaxy to show evidence for superluminal motion. “This discovery goes a long way towards confirming that radio galaxies, quasars and exotic BL Lac objects are basically the same beast, powered by super massive black holes, and differ only in orientation with respect to the observer,” Biretta said.

And this time the orientation is right in your eyes…

Many thanks to JP Metsavainio of Northern Galactic for his magic with Hubble Space Telescope images and allowing us this incredible look inside another mystery of space.

Hubble Discovers a Strange Collection of White Dwarf… Dwarfs

Small helium white dwarfs can be caused by a binary partner (NASA)

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A collection of very odd white dwarfs have been discovered in a local globular cluster. Twenty-four white dwarfs (18 of them are new discoveries) have been spotted. Although these degenerate stars aren’t exactly an uncommon (they are the small sparkling remnants left over after star death), this particular set are unique; they are made from helium, rather than the “standard” carbon and oxygen. And they are small, even smaller than the smallest dwarfs.

How did this dense cluster of old stars evolve? It turns out their stellar material is being stolen, stifling their development…

Helium-core white dwarfs have only about half the mass of typical white dwarfs, but they are found concentrated in the center of the cluster,” said Prof. Adrienne Cool, from San Francisco State University, in a paper to be published in the Astrophysical Journal in July. “With such low masses, the helium-core white dwarfs ought to be floating all around the cluster, according to theory. The fact that we find them only in the central regions suggests that they have heavy companions — partner stars that anchor them to the cluster center.”

The Hubble observations show 18 previously undiscovered helium-core white dwarfs (Jay Anderson / Space Telescope Science Institute)
The Hubble observations show 18 previously undiscovered helium-core white dwarfs (Jay Anderson / Space Telescope Science Institute)
Cool and co-author Rachel R. Strickler believe they are seeing a case of stellar plasma theft by companion binary stars in the NGC 6397 cluster, approximately 7,200 light years away. These binary partners not only anchor these strange-looking white dwarfs in the centre of the cluster, they also have a huge role to play during the dwarfs evolution.

Before a white dwarf emerges from a planetary nebula, the parent star will have gone through the red giant phase (a phase our Sun is expected to go through in 4-5 billion years time). If this red giant has a binary partner (which seems to be the case of the 24 white dwarfs in this study), the outer layers of the puffed-up giant will be stripped away by the partner, stifling the red giant’s evolution. As mass is lost, the giant never gets the chance to burn helium and then progressively heavier elements such as carbon and oxygen in and around its core. Helium then becomes the key component of these smaller-than-usual white dwarfs.

This is the first time that helium-core white dwarf stars have been discovered in partnerships with other white dwarfs in a globular cluster,” Cool said. “This large sample allows us to answer questions about the mass and nature of the partner stars, and the prevalence of these kinds of binaries in the globular cluster.”

Binary stars are known to affect their partners fairly radically, they are even known to slow or even stop the development of black holes, stripping the outer layers of the dying star, stifling black hole development by removing mass from the parent star. However, not all questions have been answered.

From Cool’s calculations, 5% of the stars found in NGC 6397 should end their lives as dim helium-core white dwarf stars, but after studying Hubble data, many of these tiny dwarfs are missing. “It’s possible that these helium-core white dwarfs cool so slowly that they haven’t had time to get very faint yet,” Cool said.

There remains the possibility that the oldest binaries containing helium-core white dwarfs have actually been destroyed by interactions with other stars in the cluster. Regardless, this is a fascinating area of study. To understand how these ancient stars evolve will not only aid the development of globular cluster models, but it will provide an invaluable insight to how binary stars influence their partners.

Source: EurekAlert!

Weekend SkyWatcher’s Forecast – April 24 – 26, 2009

Greetings, fellow SkyWatchers! Are you ready for one grrrrrrreat weekend? Then let’s do a little lion taming while the Moon is out of the picture and hunt down the “Leo Trio”. For you pirates in the crowd, hoist the Jolly Roger, because it’s time we took a look at the “Skull and Crossbones”, too! Prefer to relax? No problem. The Mu Virginid meteor shower will be in town on Saturday night for your kicked back pleasure and Sunday is time for a Herschel challenge. Time to dust off the binoculars and telescopes and I’ll see you in the back yard…

komarovFriday, April 24, 2009 – On this date in 1970, China launched its first satellite. Named Shi Jian 1, it was a successful technological and research craft. This achievement made China the fifth country to have sent a vessel into space. Observe a moment of silence for Vladimir Mikhailovich Komarov, the first man known to have died during a space mission. He was Command Pilot of Voskhod 1 and Soyuz 1. Komarov died during the landing of the Soyuz, when the spacecraft became entangled in its main parachute and fell several miles to Earth.

Tonight let’s do a galaxy hop that’s relatively easy for larger binoculars and small telescopes. You’ll find a pair of galaxies almost perfectly mid-way between Theta and Iota, and their names are M65 (RA 11 18 55 Dec +13 05 32) and M66 (RA 11 20 15 Dec +12 59 21). Discovered by Mechain in March 1780, apparently Messier didn’t notice the bright pair when a comet passed between them in 1773. At around 35 million light-years away, you will find M66 to be slightly brighter than its 200,000 light-year-distant western neighbor, M65. Although both are Sb-class spirals, the two couldn’t appear more different. M65 has a bright nucleus and a smooth spiral structure, with a dark dust lane at its eastern edge. M66 has a more stellar-like core region with thick, bright arms that show knots to larger scopes, as well as a wonderful extension from the southern edge.

leotrio

If you are viewing with a larger scope, you may notice to the north of this famous pair yet another galaxy. NGC 3628 (RA 11 20 16 Dec +13 35 13) is a similar magnitude edge-on beauty with a great dissecting dark dust lane. This pencil-slim, low surface brightness galaxy is a bit of a challenge for smaller scopes, but larger ones will find its warped central disk well worth high-power study. You may also be able to spot the ‘‘Leo Trio’’ and members of Arp’s Peculiar Galaxy Catalog!

hubbleSaturday, April 25, 2009 – Today marks the 19th anniversary of the deployment of the Hubble Space Telescope (HST) . Although everyone in the astronomical community is well aware of what this magnificent telescope ‘‘sees,’’ did you know you could see it with just your eyes? The HST is a satellite that can be tracked and observed. Visit www.heavens-above.com and enter your location. This page will provide you with a list of visible passes for your area. Although you can’t see details of the scope itself, it’s great fun to track it with binoculars or see the Sun glinting off its surface in your scope.

Tonight is the New Moon. You’ve got dark skies ahead and hopefully an itch to see something out of the ordinary with your telescope. If so, let’s go south and locate a fine reflecting nebula – NGC 2467 – in northern Puppis (RA 07 52 19 Dec –26 26 30). Sometimes referred to as the ‘‘Skull and Crossbones Nebula,’’ this billowing cloud of gas and dust is easily found less than a finger-width south-southeast of 3.5 magnitude Xi Puppis.

2467

Even small telescopes will find this expansive, starstudded emission nebula, a real beauty! Large aperture telescopes should look for neighboring splotches of nebulosity illuminated by small groupings of stars, some of which are part of a newly forming open cluster. Keep in mind while observing NGC 2467 that we are seeing it from a great distance. At 17,000 light-years away, this region of star formation is some 10 times farther away than the Great Nebula in Orion. If it were the same distance away, NGC 2467 would dwarf M42!

While you’re out, keep an eye turned toward the sky as the Mu Virginid meteor shower reaches its peak at 7–10 per hour. With dark skies early tonight, you might catch one of these medium-speed meteors radiating from a point near the constellation of Libra.

penzasSunday, April 26, 2009 – On this date in 1920, the Shapely–Curtis debate raged in Washington on the nature of (and distance to) spiral nebulae. Shapely claimed they were part of one huge galaxy to which we all belonged, while Curtis maintained they were distant galaxies of their own. Thirteen years later on the same date, Arno Penzias was born. He went on to become a Nobel Prize winner for his part in the discovery of the cosmic microwave background radiation while he was searching for the source of the ‘‘noise’’ coming from a simple horn antenna. His discovery helped further our understanding of cosmology in ways Shapely and Curtis could never have dreamed of.

2907

Tonight we’re off to study another Herschel object (H II.506) in Hydra that’s a 7 degree drop south of Alpha – NGC 2907 (RA 09 31 42.1 Dec –16 44 04). Although it will require at least a mid-aperture telescope to reveal, this edge-on galaxy is quite worth the trouble. NGC2907 is highly prized because of research done on its dust extinction properties, which greatly resemble those of our own Milky Way Galaxy. For larger telescopes, averted vision will call up a hint of a dark dust lane across a bright core. Although it is neither particularly huge nor particularly bright, this object will present an interesting challenge for those with larger scopes looking for something a bit out of the ordinary.

Until next week, remember… Dreams really do come true when you keep on reaching for the stars!

This week’s awesome images are (in order of appearance): Vladimir Mikhailovich Komarov (historical image), M65, M66 and NGC 3628: the Leo Trio (credit—REU Program/NOAO/AURA/NSF), Hubble SpaceTelescope (credit—NASA), NGC 2467 (credit—Palomar Observatory, courtesy of Caltech), Arno Penzias (widely used public image) and NGC 2907 (credit—Palomar Observatory, courtesy of Caltech). We thank you so much!

Volcanic Mountain

View north into the summit crater of Redoubt volcano where recent eruptions have removed a significant portion of the glacial ice. A remnant shelf of ice remains on the west (right) side of crater, and in this view, fumaroles are rising from near the ice/wall-rock contact. Image Creator: Payne, Allison

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Feel the ground. It’s nice and cool, right? Well, dig down a few kilometers and things really heat up. Once you’re down more than 30 km, and temperatures can reach more than 1,000 degrees C; that’s hot enough to melt rock. The melted rock is called magma, and it collects into vast chambers beneath the Earth’s surface. The molten rock is less dense than the surrounding rock and so it “floats” upwards through cracks and faults. When the magma finds its way to the surface, it erupts as lava, rock, ash and volcanic gases; this is a volcanic mountain.

A volcanic mountain starts out as a simple crack in the Earth called a volcanic vent. Magma erupts out of the ground as lava flows, clouds of ash, and explosions of rock. This material falls back to Earth around the vent, and piles up around it. Over time (and sometimes quite quickly) a volcanic mountain builds up, with the familiar cone shape.

There are different kinds of volcanic mountains. Cinder cone mountains are made up of material blasted out that rains back down. They don’t usually grow too large. Shield volcanoes are built up by many lava flows of low viscosity lava (low viscosity means that it flows more easily). The lava can flow for dozens of kilometers, and the volcano can be very wide. A stratovolcano or composite volcano is made up of many layers of ash, rock and hardened lava. Some of the largest, most impressive volcanoes in the world are stratovolcanoes (think about Mount Fuji or Rainier).

And we don’t just have volcanic mountains here on Earth. The largest mountain in the Solar System is Olympus Mons on Mars. This enormous shield volcano has grown to more than 21 km tall. There are also active volcanoes on Jupiter’s moon Io.

We have written many articles about volcanoes for Universe Today. Here’s an article about the biggest volcano in the Solar System, and here’s an article about different types of volcanoes.

Want more resources on the Earth? Here’s a link to NASA’s Human Spaceflight page, and here’s NASA’s Visible Earth.

We have also recorded an episode of Astronomy Cast about Earth, as part of our tour through the Solar System – Episode 51: Earth.

Dome Mountains

Half dome mountain. Credit: Mila Zinkova

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The interior of the Earth is hot enough to melt rock, and that’s just what happens. Melted rock squeezes together into vast pools of magma beneath the ground. Since it’s less dense than the surrounding rock, it makes its way upward to the surface. If the magma reaches the surface you get a volcano; with the ash, and the lava and the explosions. But if the magma pushes up but doesn’t actually crack through the surface, you can get a dome mountain.

Dome mountains don’t usually get as high as folded mountains because the force of the magma underneath doesn’t push hard enough. Over a long period, the magma cools to become cold, hard rock. The result is a dome-shaped mountain.

Over long periods of time, erosion wipes away the outer layers of the mountain, exposing the dome-shaped cooled magma of harder rock.

An example of a dome-shaped mountain is Half Dome in the Sierra Nevada range in California. It’s made of granite, and was once a large blob of magma pushed up through the Earth. Granite is much harder than other rock, and so it doesn’t erode as easily as the rest of the mountain. The softer layers of sedimentary rock were washed away, leaving the hard granite dome.

Other dome mountains aren’t so easy to spot. You need satellite images to see the circular shape in the Earth’s surface.

We have written many articles about the Earth for Universe Today. Here’s an article about how satellites can measure the movement of the Earth after an earthquake.

Want more resources on the Earth? Here’s a link to NASA’s Human Spaceflight page, and here’s NASA’s Visible Earth.

We have also recorded an episode of Astronomy Cast about Earth, as part of our tour through the Solar System – Episode 51: Earth.

Fault-Block Mountains

Diagram of a fault-block mountain range.

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Fault-block mountains are formed by the movement of large crustal blocks when forces in the Earth’s crust pull it apart. Some parts of the Earth are pushed upward and others collapse down.

To understand a fault-block mountain, or sometimes referred as a “fault mountain”, you need to understand what a fault is. Faults are simply cracks in the Earth’s crust. The surface of the Earth can move along these faults, and displace rock layers on either side. Wherever you have movement along the faults, you can get earthquakes, and over long periods of time mountains form under the intense pressure.

Large blocks of rock along the sides of these faults can be uplifted and tilted sideways by this incredible force. And then, on the opposite sides of the faults, the ground tilts downwards forming a depression. This depression gets filled in and leveled by the erosion of the mountains above.

The Sierra Nevada mountains in California are an example of a fault-block mountain range.

We have written many articles about the Earth for Universe Today. Here’s an article that shows how satellites can calculate the movement of the Earth during earthquakes.

Want more resources on the Earth? Here’s a link to NASA’s Human Spaceflight page, and here’s NASA’s Visible Earth.

We have also recorded an episode of Astronomy Cast about Earth, as part of our tour through the Solar System – Episode 51: Earth.

Fold Mountains

Mount Everest from Kalapatthar. Photo: Pavel Novak

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Some of the most dramatic mountains in the world are fold mountains. These are created when two of the Earth’s tectonic plates crash together – like in a head-on car crash. The edges of the two plates buckle and fold, and the peaks of these folds are mountains. Entire mountain ranges, thousands of kilometers long, are created during these slow motion collisions between tectonic plates.

Some famous examples of fold mountains are the Himalayan mountains in Asia and the Rocky Mountains in North America. Consider the fact that the Earth’s tectonic plates are moving very slowly, just a few centimeters every year. These folding collisions play out in incredibly slow motion, taking millions of years. The Indian subcontinent crashed into Asia 24 million years ago, and since then it has built up the Himalayan mountains – the tallest mountains in the world. In fact, the Himalayans are still growing.

Want to make your own folded mountain range? Take two flat strips of modeling clay and put them side to side. Then slowly push one strip into the other and you’ll see how one or both will crumple up under the pressure. You’ll make your own mini mountain range.

We have written many articles about mountains for Universe Today. Here’s an article about different types of mountains.

Want more resources on the Earth? Here’s a link to NASA’s Human Spaceflight page, and here’s NASA’s Visible Earth.

We have also recorded an episode of Astronomy Cast about Earth, as part of our tour through the Solar System – Episode 51: Earth.