Spiral-Arms

Barred Spiral Galaxy NGC 1300

(via APOD; Image Credit: Hubble Heritage Team, ESA, NASA )

Big, beautiful, barred spiral galaxy NGC 1300 lies some 70 million light-years away on the banks of the constellation Eridanus. This Hubble Space Telescope composite view of the gorgeous island universe is one of the largest Hubble images ever made of a complete galaxy. NGC 1300 spans over 100,000 light-years and the Hubble image reveals striking details of the galaxy’s dominant central bar and majestic spiral arms. In fact, on close inspection the nucleus of this classic barred spiral itself shows a remarkable region of spiral structure about 3,000 light-years across. Like other spiral galaxies, including our own Milky Way, NGC 1300 is thought to have a supermassive central black hole.

Barred Spiral Galaxy NGC 1300

NGC 1300 is 61 million light-years away from earth in the constellation Eridanus. The galaxy is about 110,000 light-years across which makes it just slightly larger than the Milky Way. NGC 1300 is a member a cluster of 200 galaxies known as the Eridanus Cluster. In the core of the larger spiral structure of NGC 1300, the nucleus shows its own extraordinary and distinct “grand-design” spiral structure that is about 3,300 light-years long. Only galaxies with large-scale bars appear to have these grand-design inner disks.

Credit: NASA/Hubble

New insights on how spiral galaxies get their arms

Spiral galaxies are some of the most beautiful and photogenic residents of the universe. Our own Milky Way is a spiral. Our solar system and Earth reside somewhere near one of its filamentous arms. And nearly 70 percent of the galaxies closest to the Milky Way are spirals.

But despite their common shape, how galaxies like ours get and maintain their characteristic arms has proved to be an enduring puzzle in astrophysics. How do the arms of spiral galaxies arise? Do they change or come and go over time?

The answers to these and other questions are now coming into focus as researchers capitalize on powerful new computer simulations to follow the motions of as many as 100 million “stellar particles” as gravity and other astrophysical forces sculpt them into familiar galactic shapes. A team of researchers from the University of Wisconsin-Madison and the Harvard-Smithsonian Center for Astrophysics reports simulations that seem to resolve long-standing questions about the origin and life history of spiral arms in disk galaxies.

“We show for the first time that stellar spiral arms are not transient features, as claimed for several decades,” says UW-Madison astrophysicist Elena D'Onghia, who led the new research along with Harvard colleagues Mark Vogelsberger and Lars Hernquist. “The spiral arms are self-perpetuating, persistent, and surprisingly long lived,” adds Vogelsberger.

The origin and fate of the emblematic spiral arms in disk galaxies have been debated by astrophysicists for decades, with two theories predominating. One holds that the arms come and go over time. A second and widely held theory is that the material that makes up the arms – stars, gas and dust – is affected by differences in gravity and jams up, like cars at rush hour, sustaining the arms for long periods.

The new results fall somewhere in between the two theories and suggest that the arms arise in the first place as a result of the influence of giant molecular clouds – star forming regions or nurseries common in galaxies. Introduced into the simulation, the clouds act as “perturbers” and are enough to not only initiate the formation of spiral arms but to sustain them indefinitely.

“We find they are forming spiral arms,” explains D'Onghia. “Past theory held the arms would go away with the perturbations removed, but we see that (once formed) the arms self-perpetuate, even when the perturbations are removed. It proves that once the arms are generated through these clouds, they can exist on their own through (the influence of) gravity, even in the extreme when the perturbations are no longer there.”

NGC 2787

NGC 2787 is a lenticular galaxy located about 25 million light years away towards the constellation Ursa Major. It is about 45,000 light years across, and has an interestingly structured central region.

Lenticular galaxies are less studied, relatively, than other structures. They are odd in that they are something between a spiral and elliptical galaxy. Like spirals, they have a disk structure, but like ellipticals, they have less gas and dust and no spiral arms.

Image and information from NASA.

In the Center of Spiral Galaxy NGC 3521 : This huge swirling mass of stars, gas, and dust occurs near the center of a nearby spiral galaxy. Gorgeous spiral NGC 3521 is a mere 35 million light-years distant, toward the constellation Leo. Spanning some 50,000 light-years, its central region is shown in this dramatic image, constructed from data from the Hubble Space Telescope. The close-up view highlights this galaxy’s characteristic multiple, patchy, irregular spiral arms laced with dust and clusters of young, blue stars. In contrast, many other spirals exhibit grand, sweeping arms. A relatively bright galaxy in planet Earth’s sky, NGC 3521 is easily visible in small telescopes, but often overlooked by amateur imagers in favor of other Leo spiral galaxies, like M65 and M66. via NASA

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NASA Astronomy Picture of the Day 2016 January 29 

Hidden Galaxy IC 342 

Similar in size to large, bright spiral galaxies in our neighborhood, IC 342 is a mere 10 million light-years distant in the long-necked, northern constellation Camelopardalis. A sprawling island universe, IC 342 would otherwise be a prominent galaxy in our night sky, but it is hidden from clear view and only glimpsed through the veil of stars, gas and dust clouds along the plane of our own Milky Way galaxy. Even though IC 342’s light is dimmed by intervening cosmic clouds, this deep telescopic image traces the galaxy’s obscuring dust, blue star clusters, and glowing pink star forming regions along spiral arms that wind far from the galaxy’s core. IC 342 may have undergone a recent burst of star formation activity and is close enough to have gravitationally influenced the evolution of the local group of galaxies and the Milky Way.

Massive Stars Show the Way:
Our Galaxy Has Four, not Two, but Four Spiral Arms
17 December 2013

On a personal note: Today I spent some time putting together an overview of the previous (2007/8) new findings - that there are only two spiral arms and not four. With stunning graphics, too. Then I see this on the Science magazine news page!  

A 12-year study of massive stars has reaffirmed that our Galaxy has four spiral arms, following years of debate sparked by images taken by NASA’s Spitzer Space Telescope that only showed two arms.

The new research, which is published online in the Monthly Notices of the Royal Astronomical Society, is part of the RMS Survey, which was launched by academics at the University of Leeds.

Read the rest of the press release from the Royal Astronomical Society …

IMAGE:  This artist’s impression shows our Galaxy, the Milky Way, as the spiral shape in the background. The massive stars referred to in the new study are indicated by red circles. The position of the Solar System is marked by a black dot and circle at the top centre. Credit: J. Urquhart et al.
Background image by Robert Hurt of the Spitzer Science Center.  (via Massive stars mark out Milky Way’s ‘missing arms’)
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The new work appears in the paper “The RMS survey: galactic distribution of massive star formation”, J. S. Urquhart, et al – Monthly Notices of the Royal Astronomical Society, published by Oxford University Press.

The Whirlpool Galaxy

M51, also known as NGC 5194 or the Whirlpool Galaxy, is having a close encounter with a nearby companion galaxy, NGC 5195, just off the upper edge of this image. The companion’s gravitational pull is triggering star formation in the main galaxy, as seen in brilliant detail by numerous, luminous clusters of young and energetic stars. The bright clusters are highlighted in red by their associated emission from glowing hydrogen gas.

The Whirlpool galaxy, M51, has been one of the most photogenic galaxies in amateur and professional astronomy. Easily photographed and viewed by smaller telescopes, this celestial beauty is studied extensively in a range of wavelengths by large ground- and space-based observatories. This Hubble composite image shows visible starlight as well as light from the emission of glowing hydrogen, which is associated with the most luminous young stars in the spiral arms.

Credit: NASA/Hubble

Milky Way’s Spiral Arms Are the Product of an Intergalactic Collision Course

A dwarf galaxy named Sagittarius loaded with dark matter has careened twice through our much larger home galaxy in the past two billion years,and is lined up to do it again. As the galaxies collide, the force of the impact sends stars streaming from both in long loops. Those continue to swell with stars and are gradually tugged outward by the Milky Way’s rotation into a familiar ringed arm.

It’s the weighty dark matter from Sagittarius that provided the initial push. The smaller galaxy pays a steep price though – sucked inward repeatedly by the Milky Way’s mightier gravity, it’s being ripped apart by the blows, sending huge amounts of its stars and dark matter reeling into the new arms.

When all that dark matter first smacked into the Milky Way, 80% to 90% of it was stripped off. That first impact triggered instabilities that were amplified, and quickly formed spiral arms and associated ring-like structures in the outskirts of our galaxy.

The Sagittarius galaxy is due to strike the southern face of the Milky Way disk fairly soon, Purcell said – in another 10 million years or so.

Image: Computer model of the Milky Way and its smaller neighbor, the Sagittarius dwarf galaxy. The flat disk is the Milky Way, and the looping stream of material is made of stars torn from Sagittarius as a result of the strong gravity of our galaxy. The spiral arms began to emerge about two billion years ago, when the Sagittarius galaxy first collided with the Milky Way disk.

Messier 81

Messier 81 is a grand design spiral galaxy located about 11.6 million light years away towards the constellation Ursa Major, the Great Bear. Its spiral arms trace beautifully all the way to its center core, the hallmark of a grand design galaxy.

The arms contain many younger, blue stars formed in the past few million years, along with a population of stars formed in a period of star formation starting about 600 million years ago. The core contains older, redder stars, and is much larger than our Milky Way’s central bulge. The central black hole is also larger than our galaxy’s, about 15 times so. Research has shown that the size of the central black hole is proportional to the mass of the central bulge.

Image from NASA, information from ESA.

NASA Astronomy Picture of the Day 2016 February 3 

Galaxy Wars: M81 versus M82 

In the lower left corner, surrounded by blue spiral arms, is spiral galaxy M81. In the upper right corner, marked by red gas and dust clouds, is irregular galaxy M82. This stunning vista shows these two mammoth galaxies locked in gravitational combat, as they have been for the past billion years. The gravity from each galaxy dramatically affects the other during each hundred million-year pass. Last go-round, M82’s gravity likely raised density waves rippling around M81, resulting in the richness of M81’s spiral arms. But M81 left M82 with violent star forming regions and colliding gas clouds so energetic the galaxy glows in X-rays. This big battle is seen from Earth through the faint glow of an Integrated Flux Nebula, a little studied complex of diffuse gas and dust clouds in our Milky Way Galaxy. In a few billion years only one galaxy will remain.

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Bode’s Galaxy - A Grand Design Spiral Galaxy

“A grand design spiral galaxy is a type of spiral galaxy with prominent and well-defined spiral arms, as opposed to multi-arm and flocculent spirals which have subtler structural features. The spiral arms of a grand design galaxy extend clearly around the galaxy through many radians and can be observed over a large fraction of the galaxy’s radius. Approximately 10 percent of spiral galaxies are classified as grand design type spirals.

Bode’s Galaxy, also known as M81 or NGC3031, is about 12 million light-years away in the constellation Ursa Major. Due to its proximity to Earth, large size and active galactic nucleus (which harbors a 70 million M(Solar Mass) super-massive black hole), M81 has been studied extensively by professional astronomers. The galaxy’s large size and relatively high brightness also make it a popular target for amateur astronomers.”

Credit: NASA, ESA, Hubble, Spitzer, Wikipedia

NGC 2082

NGC 2082 is a spiral galaxy located about 60 million light years away towards the constellation Dorado, the Swordfish, in the southern hemisphere. It hosted a supernova that was visible in 1992.

NGC 2082’s spiral arms are somewhat ragged in comparison to many other spirals, but individual blue stars can be seen shining brightly. The galaxy is also laced with dense dust clouds spreading through the spiral arms and the central bulge.

image and information from ESA.

A Ticking Time Bomb and a Hidden Galaxy

A Ticking Time Bomb and a Hidden Galaxy

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There are many types of objects in space that just can’t be seen with visible light, and many more that have very different features when observed across the electromagnetic spectrum.  A prime example of the former is a molecular cloud.  Cold, incredibly huge, and full of low density Hydrogen, these clouds are the raw material for star forming galaxies.  If stars begin to form within them, they…

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Hubble is so important to our understanding (universe of cats)

Hubble is so important to our understanding (universe of cats)

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Spiral Galaxy 

A spiral galaxy is a certain kind of galaxy originally described by Edwin Hubble in his 1936 work The Realm of the Nebulae and, as such, forms part of the Hubble sequence. Spiral galaxies consist of a flat, rotating disc containing stars, gas and dust, and a central concentration of stars known as the bulge. These are surrounded by a much fainter haloof stars, many of which reside…

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Galactic wreckage in Stephan’s Quintet:

A clash among members of a famous galaxy quintet reveals an assortment of stars across a wide colour range, from young, blue stars to aging, red stars.

This portrait of Stephan’s Quintet, also known as the Hickson Compact Group 92, was taken by the new Wide Field Camera 3 (WFC3) aboard the NASA/ESA Hubble Space Telescope. Stephan’s Quintet, as the name implies, is a group of five galaxies. The name, however, is a bit of a misnomer. Studies have shown that group member NGC 7320, at upper left, is actually a foreground galaxy that is about seven times closer to Earth than the rest of the group.

Three of the galaxies have distorted shapes, elongated spiral arms, and long, gaseous tidal tails containing myriad star clusters, proof of their close encounters. These interactions have sparked a frenzy of star birth in the central pair of galaxies. This drama is being played out against a rich backdrop of faraway galaxies.

The image, taken in visible and near-infrared light, showcases WFC3’s broad wavelength range. The colours trace the ages of the stellar populations, showing that star birth occurred at different epochs, stretching over hundreds of millions of years. The camera’s infrared vision also peers through curtains of dust to see groupings of stars that cannot be seen in visible light.

NGC 7319, at top right, is a barred spiral with distinct spiral arms that follow nearly 180 degrees back to the bar. The blue specks in the spiral arm at the top of NGC 7319 and the red dots just above and to the right of the core are clusters of many thousands of stars. Most of the Quintet is too far away even for Hubble to resolve individual stars.

Continuing clockwise, the next galaxy appears to have two cores, but it is actually two galaxies, NGC 7318A and NGC 7318B. Encircling the galaxies are young, bright blue star clusters and pinkish clouds of glowing hydrogen where infant stars are being born. These stars are less than 10 million years old and have not yet blown away their natal cloud. Far away from the galaxies, at right, is a patch of intergalactic space where many star clusters are forming.

NGC 7317, at bottom left, is a normal-looking elliptical galaxy that is less affected by the interactions.

Sharply contrasting with these galaxies is the dwarf galaxy NGC 7320 at upper left. Bursts of star formation are occurring in the galaxy’s disc, as seen by the blue and pink dots. In this galaxy, Hubble can resolve individual stars, evidence that NGC 7320 is closer to Earth. NGC 7320 is 40 million light-years from Earth. The other members of the Quintet reside about 300 million light-years away in the constellation Pegasus.

These more distant members are markedly redder than the foreground galaxy, suggesting that older stars reside in their cores. The stars’ light also may be further reddened by dust stirred up in the encounters.

Spied by Edouard M. Stephan in 1877, Stephan’s Quintet is the first compact group ever discovered.

WFC3 observed the Quintet in July and August 2009. The composite image was made by using filters that isolate light from the blue, green and infrared portions of the spectrum, as well as emission from ionised hydrogen.

These Hubble observations are part of the Hubble Servicing Mission 4 Early Release Observations. NASA astronauts installed the WFC3 camera during a servicing mission in May to upgrade and repair the 19-year-old Hubble telescope.

Credit:
NASA, ESA and the Hubble SM4 ERO Team

Spiral Galaxy NGC 2841

NASA’s Hubble Space Telescope reveals a majestic disk of stars and dust lanes in this view of the spiral galaxy NGC 2841.

A bright cusp of starlight marks the galaxy’s center. Spiraling outward are dust lanes that are silhouetted against the population of whitish middle-aged stars. Much younger blue stars trace the spiral arms.

Notably missing are pinkish emission nebulae indicative of new star birth. It is likely that the radiation and supersonic winds from fiery, super-hot, young blue stars cleared out the remaining gas (which glows pink), and hence shut down further star formation in the regions in which they were born. NGC 2841 currently has a relatively low star formation rate compared to other spirals that are ablaze with emission nebulae.

NGC 2841 lies 46 million light-years away in the constellation of Ursa Major (The Great Bear). This image was taken in 2010 through four different filters on Hubble’s Wide Field Camera 3. Wavelengths range from ultraviolet light through visible light to near-infrared light.

Credit: NASA, ESA, and the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration