Tag: galaxies

A galaxy’s structure of gas and dust, as seen in the infrared by Webb

10:04 am

NGC 1433 as seen in the infrared
NGC 1433 as seen in the infrared. Click for original image.

Scientists have now released 21 papers on the gas and dust structures in nearby galaxies, based on infrared images from the Webb Space Telescope, used in collaboration with other telescopes looking in other wavelengths.

The largest survey of nearby galaxies in Webb’s first year of science operations is being carried out by the Physics at High Angular resolution in Nearby Galaxies (PHANGS) collaboration, involving more than 100 researchers from around the globe. The Webb observations are led by Janice Lee, Gemini Observatory chief scientist at the National Science Foundation’s NOIRLab and affiliate astronomer at the University of Arizona in Tucson.

The team is studying a diverse sample of 19 spiral galaxies, and in Webb’s first few months of science operations, observations of five of those targets – M74, NGC 7496, IC 5332, NGC 1365, and NGC 1433 – have taken place.

The image to the right is Webb’s infrared image of NGC 1433, estimated to be 46 million light years away. The bright areas extending outward in the spiral arms are believed to be star-forming regions. From the caption:

At the center of the galaxy, a tight, bright core featuring a unique double ring structure shines in exquisite detail with Webb’s extreme resolution. In this case, that ‘double ring’ is actually tightly wrapped spiral arms that wind into an oval shape along the galaxy’s bar.

NGC 1433 is a Seyfert galaxy, which are typically relatively close to Earth and has a supermassive black hole at the center eating material at a high rate. The brightness and lack of dust in the MIRI image of NGC 1433 could hint at a recent collision with another galaxy.

When comparing Webb’s infrared view with Hubble’s optical view, taken in 2014 and found here, the differences are definitely striking. Webb sees the gas and dust that is dark in Hubble’s images, while Hubble sees things at much higher resolution and thus sees more fine detail.

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Trio of colliding galaxies

9:32 am

Trio of colliding galaxies
Click for original image.

Cool image time! The picture above, cropped and reduced to post here, was taken by the Hubble Space Telescope and released today. From the caption:

Three galaxies stand together just right of centre. They are close enough that they appear to be merging into one. Their shapes are distorted, with strands of gas and dust running between them. Each is emitting a lot of light. Further to the left is an unconnected, dimmer spiral galaxy. The background is dark, with a few smaller, dim and faint galaxies and a couple of stars.

Astronomers estimate the colliding galaxies are about 50,000 light years from each other, which for galaxies is quite close. Eventually gravity will cause all three to merge into a single very large galaxy, its shape distorted by the merger. What that shape will be is one of the things astronomers are trying to figure out. At present their theories for galaxy evolution states that as galaxies grow by absorbing smaller nearby neighbors, they evolve from spirals to ellipticals, giant blobs lacking a distinct obvious structure.

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A long-armed galaxy

8:51 am

Galaxy with long and faint tidal streams
Click for full image.

Cool image time! The photo to the right, cropped, enhanced, and reduced to post here, was taken by the Hubble Space Telescope as part of a survey of peculiar looking galaxies.

The peculiar spiral galaxy ESO 415-19, which lies around 450 million light-years away, stretches lazily across this image from the NASA/ESA Hubble Space Telescope. While the centre of this object resembles a regular spiral galaxy, long streams of stars stretch out from the galactic core like bizarrely elongated spiral arms. These are tidal streams caused by some chance interaction in the galaxy’s past, and give ESO 415-19 a distinctly peculiar appearance.

ESO 415-19’s peculiarity made it a great target for Hubble. This observation comes from an ongoing campaign to explore the Arp Atlas of Peculiar Galaxies, a menagerie of some of the weirdest and most wonderful galaxies that the Universe has to offer. These galaxies range from bizarre lonesome galaxies to spectacularly interacting galaxy pairs, triplets, and even quintets. These space oddities are spread throughout the night sky, which means that Hubble can spare a moment to observe them as it moves between other observational targets.

I have intentionally brightened the galaxy to make the two faint two tidal streams more obvious. That they are so faint compared to the galaxy itself is in itself a mystery.

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Distant interacting galaxies

11:25 am

Interacting galaxies
Click for original image.

Cool image time! The picture to the right, cropped and reduced to post here, was taken by the Hubble Space Telescope as part of a survey of known “weird and wonderful galaxies.” This particular pair is dubbed Arp 248, and is estimated to be about 200 million light years away.

Two spiral galaxies are viewed almost face-on; they are a mix of pale blue and yellow in colour, crossed by strands of dark red dust. They lie in the upper-left and lower-right corners. A long, faint streak of pale blue joins them, extending from an arm of one galaxy and crossing the field diagonally. A small spiral galaxy, orange in colour, is visible edge-on, left of the lower galaxy.

The connecting stream indicates that these galaxies are interacting with each other, gravity drawing stars and gas from the upper galaxy towards the lower.

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Interacting galaxies

9:02 am

Interacting galaxies
Click for full image.

The news is light this morning, so this cool image will be the first of three. The picture to the right, cropped and reduced to post here, was taken by the Hubble Space Telescope and released today. From the caption:

The two interacting galaxies making up the pair known as Arp-Madore 608-333 seem to float side by side in this image from the NASA/ESA Hubble Space Telescope. Though they appear serene and unperturbed, the two are subtly warping one another through a mutual gravitational interaction that is disrupting and distorting both galaxies.

I did a search for any research of this galaxy pair, and found that its identification was only part of a larger survey, with only a little research done on its spectroscopy. Thus, I can’t tell you the size or distance, or how far apart from each other these galaxies lie.

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A galaxy slowly being eaten by its black hole

10:16 am

Spiral galaxy
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Cool image time! The photo to the right, rotated and reduced to post here, was taken by the Hubble Space Telescope. From the caption:

NGC 5495, which lies around 300 million light-years from Earth in the constellation Hydra, is a Seyfert galaxy, a type of galaxy with a particularly bright central region. These luminous cores — known to astronomers as active galactic nuclei — are dominated by the light emitted by dust and gas falling into a supermassive black hole. This image is drawn from a series of observations captured by astronomers studying supermassive black holes lurking in the hearts of other galaxies.

Essentially Seyfert galaxies are galaxies whose central supermassive black hole has become dominant, large enough that its gravity is slowly eating up the rest of the galaxy. As it increasingly swallows stars and gas, the black hole emits more and more energy, thus becoming an active galactic nuclei.

Two stars from our own galaxy also dominate this picture, one inside and to the right of the galaxy’s center, and the other the bright star at the bottom of the picture, both identified by the diffraction spikes.

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A galaxy with swirling arms

9:17 am

A galaxy with swirling arms
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Cool image time! The picture to the right, cropped and reduced to post here, was released yesterday by the science team that operates the Hubble Space Telescope. It captures a galaxy about 520 million light years away that appears to have been reshaped due to a galaxy merger.

That merger somehow distorted the disk of the inner galaxy, the brightest area, while also producing two sweeping spiral streams in the surrounding periphery.

Despite its unusual shape, astronomers did not choose to study this galaxy. From the caption:

This observation is a gem from the Galaxy Zoo project, a citizen science project involving hundreds of thousands of volunteers from around the world who classified galaxies to help scientists solve a problem of astronomical proportions: how to sort through the vast amounts of data generated by telescopes. A public vote selected the most astronomically intriguing objects for follow-up observations with Hubble. CGCG 396-2 is one such object, imaged here by Hubble’s Advanced Camera for Surveys.

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A giant elliptical galaxy

3:14 pm

A giant elliptical galaxy
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Cool image time! The image to the right, reduced to post here, was taken by the Hubble Space Telescope of the giant elliptical galaxy NGC 474.

Located some 100 million light-years from Earth, NGC 474 spans about 250,000 light-years across – that’s 2.5 times larger than our own Milky Way galaxy! Along with its enormous size, NGC 474 has a series of complex layered shells that surround its spherical-shaped core. The cause of these shells is unknown, but astronomers theorize that they may be the aftereffects of the giant galaxy absorbing one or more smaller galaxies. In the same way a pebble creates ripples on a pond when dropped into the water, the absorbed galaxy creates waves that form the shells.

About 10% of elliptical galaxies have shell structures, but unlike the majority of elliptical galaxies, which are associated with galaxy clusters, shelled ellipticals usually lie in relatively empty space. It may be that they’ve cannibalized their neighbors.

NGC 474 is no exception, also located in a relatively empty region of space.

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Colliding galaxies

1:11 pm

Merging galaxies

The string of amazing galaxy images coming from the Hubble Space Telescope continues. The photo to the right, cropped and reduced to post here, was released today and shows an object dubbed VV-689 that is believed to be two galaxies in the process of colliding and merging.

The angelic image comes from a set of Hubble observations that took a closer look at “Zoo Gems,” interesting galaxies from the Galaxy Zoo citizen science project. This crowdsourced program relies on hundreds of thousands of volunteers to classify galaxies and help astronomers wade through a deluge of data from robotic telescopes. In the process, volunteers discovered a gallery of weird and wonderful galaxy types, some not previously studied.

This image will lay the groundwork for more detailed research. Right now it appears no one has even estimated its distance.

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A galactic starship Enterprise

3:30 pm

A galactic starship Enterprise
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Cool image time! The image to the right, cropped and reduced to post here, was taken by cameras on the Hubble Space Telescope. From the caption:

The subject of this image is a group of three galaxies, collectively known as NGC 7764A. They were imaged by the NASA/ESA Hubble Space Telescope, using both its Advanced Camera for Surveys and Wide Field Camera 3. The two galaxies in the upper right of the image appear to be interacting with one another. The long trails of stars and gas extending from them give the impression that they have both just been struck at great speed, thrown into disarray by the bowling-ball-shaped galaxy to the lower left of the image. In reality, interactions between galaxies happen over very long time periods, and galaxies rarely collide head-on with one another. It is also unclear whether the galaxy to the lower left is interacting with the other two, although they are so relatively close in space that it seems possible that they are.

This galaxy group is estimated to be about 425 million light years away, though that number might be different for the galaxy in the lower left.

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A lopsided spiral galaxy

12:54 pm

Losided spiral galaxy
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For a change, today’s cool image is not from Mars, but instead goes deep into space. The photo to the right, reduced to post here, was taken by the Hubble Space Telescope of the relatively nearby spiral galaxy NGC 2276, located about 120 million light years away. As the caption explains:

The magnificent spiral galaxy NGC 2276 looks a bit lopsided in this Hubble Space Telescope snapshot. A bright hub of older yellowish stars normally lies directly in the center of most spiral galaxies. But the bulge in NGC 2276 looks offset to the upper left.

In reality, a neighboring galaxy to the right of NGC 2276 (NGC 2300, not seen here) is gravitationally tugging on its disk of blue stars, pulling the stars on one side of the galaxy outward to distort the galaxy’s normal fried-egg appearance. This sort of “tug-of-war” between galaxies that pass close enough to feel each other’s gravitational pull is not uncommon in the universe. But, like snowflakes, no two close encounters look exactly alike.

The scientists also note that the bright edge along the galaxy’s north and west perimeter mark regions of intense star-formation. In those same regions astronomers six years ago identified the first medium-sized black hole ever found.

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Colliding galaxies!

2:19 pm

Colliding galaxies!
Click here and here to see full images.

Cool images from Hubble! The two photos to the right, cropped and reduced to post here, shows two different galaxies undergoing a collision with another galaxy. Both images are from of a montage of six galaxy merger images from the Hubble Space Telescope, released yesterday.

To celebrate a new year, the NASA/ESA Hubble Space Telescope has published a montage of six beautiful galaxy mergers. Each of these merging systems was studied as part of the recent HiPEEC survey to investigate the rate of new star formation within such systems. These interactions are a key aspect of galaxy evolution and are among the most spectacular events in the lifetime of a galaxy.

It is during rare merging events that galaxies undergo dramatic changes in their appearance and in their stellar content. These systems are excellent laboratories to trace the formation of star clusters under extreme physical conditions.

The first galaxy merger to the right is dubbed NGC 6052, and is located in the constellation of Hercules about 230 million light-years away. This pair of colliding galaxies, according to the caption, “were first discovered in 1784 by William Herschel and were originally classified as a single irregular galaxy because of their odd shape. However, we now know that NGC 6052 actually consists of two galaxies that are in the process of colliding.”

The second image shows two galaxies, IC 694 and NGC 3690, about 700 millions after they had completed a close pass of each other. From the caption: “As a result of this interaction, the system underwent a fierce burst of star formation. In the last fifteen years or so six supernovae have popped off in the outer reaches of the galaxy, making this system a distinguished supernova factory.”

You can see all six merger images here, though to my eye these two are the most impressive.

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Hubble maps giant gas halo around Andromeda

11:38 am

Astronomers using the Hubble Space Telescope’s ability to observe in ultraviolet wavelengths have now mapped the giant halo of gas that surrounds the Andromeda galaxy 2.5 million light years away.

The work found that the halo appears to have both an inner and outer shell.

“We find the inner shell that extends to about a half million light-years is far more complex and dynamic,” explained study leader Nicolas Lehner of the University of Notre Dame in Indiana. “The outer shell is smoother and hotter. This difference is a likely result from the impact of supernova activity in the galaxy’s disk more directly affecting the inner halo.”

A signature of this activity is the team’s discovery of a large amount of heavy elements in the gaseous halo of Andromeda. Heavier elements are cooked up in the interiors of stars and then ejected into space—sometimes violently as a star dies. The halo is then contaminated with this material from stellar explosions.

The Andromeda galaxy, also known as M31, is a majestic spiral of perhaps as many as 1 trillion stars and comparable in size to our Milky Way. At a distance of 2.5 million light-years, it is so close to us that the galaxy appears as a cigar-shaped smudge of light high in the autumn sky. If its gaseous halo could be viewed with the naked eye, it would be about three times the width of the Big Dipper. This would easily be the biggest feature on the nighttime sky.

Though there is of course uncertainty here, this research is confirming earlier work, making its conclusions more robust.

A side note: Ultraviolet observations can only be done in space, as the atmosphere blocks it. Hubble I think is the only telescope in space right now with this capability. There used to be others, the most noteworthy of all being the International Ultraviolet Explorer, which functioned from 1978 to 1996 but was then decommissioned because neither NASA nor ESA were willing to fund its operation any longer.

No replacements have been launched because the budget for space astronomy has almost entirely been eaten by the overbudget and long delayed James Webb Space Telescope, with future budgets to be eaten similarly by the Roman.Space Telescope.

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Astronomers discover three merging supermassive black holes

9:03 am

Using telescopes on Mauna Kea in Hawaii, astronomers have discovered three different galaxies that have pairs of supermassive black holes at their center, with all three likely to merge at some point in the future.

First the scientists used the Subaru Telescope to survey more than 34,000 known quasars, high energy supermassive black holes.

The team identified 421 promising cases. However, there was still the chance many of these were not bona-fide dual quasars but rather chance projections such as starlight from our own galaxy. Confirmation required detailed analysis of the light from the candidates to search for definitive signs of two distinct quasars.

Using Keck Observatory’s Low Resolution Imaging Spectrometer (LRIS) and Gemini Observatory’s Near-Infrared Integral Field Spectrometer, Silverman and his team identified three dual quasars, two of which were previously unknown. Each object in the pair showed the signature of gas moving at thousands of kilometers per second under the influence of a supermassive black hole.

From this survey work they now tentatively estimate that only 0.3% of all known quasars are likely made up of a binary, which in turn gives them a rough estimate of how often galaxies with such supermassive black holes collide and merge. This in turn helps them develop theories on galaxy formation.

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The magnetic field of a spiral galaxy

9:05 am

Magnetic field of a spiral galaxy
Click for full image.

Using a variety of telescopes, especially the Jansky Very Large Array radio telescope, astronomers have successfully mapped the magnetic field lines of a spiral galaxy seen edge on and 67 million light years away.

The image to the right, cropped and reduced to post here, shows what they have found.

The magnetic field lines extend as much as 22,500 light-years beyond the galaxy’s disk. Scientists know that magnetic fields play an important role in many processes, such as star formation, within galaxies. However, it is not fully understood how such huge magnetic fields are generated and maintained. A leading explanation, called the dynamo theory, suggests that magnetic fields are generated by the motion of plasma within the galaxy’s disk. Ideas about the cause of the kinds of large vertical extensions seen in this image are more speculative, and astronomers hope that further observations and more analysis will answer some of the outstanding questions.

Our understanding of these kinds of gigantic magnetic fields is poor, to put it mildly. This data really only begins the research.

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First detection of extended galactic magnetic field

9:51 am

Whale galaxy with magnetic filaments
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Astronomers have made the first detection in another galaxy of a magnetic field that extends out into the galaxy’s halo.

The image above, based on data from the Jansky radio telescope, illustrates what they found..

The spiral galaxy is seen edge-on, with its disk of stars shown in pink. The filaments, shown in green and blue, extend beyond the disk into the galaxy’s extended halo. Green indicates filaments with their magnetic field pointing roughly toward us and blue with the field pointing away. This phenomenon, with the field alternating in direction, has never before been seen in the halo of a galaxy.

“This is the first time that we have clearly detected what astronomers call large-scale, coherent, magnetic fields far in the halo of a spiral galaxy, with the field lines aligned in the same direction over distances of a thousand light-years. We even see a regular pattern of this organized field changing direction,” said Marita Krause, of the Max-Planck Institute for Radioastronomy in Bonn, Germany.

The galaxy, dubbed the Whale by the astronomers, is about 35 million light years away, and has a diameter of about 80,000 light years, slightly smaller than the Milky Way.

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Astronomers roughly map out Andromeda’s history

10:40 am

The uncertainty of science: Astronomers have now roughly mapped out the history of the Andromeda galaxy, identifying two major events whereby it had absorbed nearby dwarf galaxies.

“It’s been known for 10 to 15 years that Andromeda has a vigorous history of accumulating and destroying its neighbours,” Mackey says. In fact, he says, “It seems to have a much more intense history of that than the Milky Way.”

…[New data] “tells us there were two main events that formed the halo of Andromeda,” Mackey says. “One occurred very long ago. The other must have happened relatively recently.”

Not that Andromeda couldn’t also have eaten innumerable smaller galaxies. ”We can’t trace them with galactic clusters, because they didn’t have any to begin with,” Mackey says.

Most of the news reports about this new research have been very overwrought (Andromeda is “violent” and is going to “eat us!”) and very unaware that the assimilation of nearby small galaxies by Andromeda is not really news. Astronomers have known for years that big galaxies like Andromeda and the Milky Way absorb the dwarf galaxies around them. All this story does is postulate a more detailed though very rough timeline.

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New analysis throws wrench in formation theory of spirals in galaxies

8:29 am

The uncertainty of science: A new analysis of over 6000 galaxies suggests that a long-held model for the formation of spirals in galaxies is wrong.

[Edwin] Hubble’s model soon became the authoritative method of classifying spiral galaxies, and is still used widely in astronomy textbooks to this day. His key observation was that galaxies with larger bulges tended to have more tightly wound spiral arms, lending vital support to the ‘density wave’ model of spiral arm formation.

Now though, in contradiction to Hubble’s model, the new work finds no significant correlation between the sizes of the galaxy bulges and how tightly wound the spirals are. This suggests that most spirals are not static density waves after all.

Essentially, we still have no idea why spirals form in galaxies.

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New sky survey uncovers hundreds of thousands of previously unknown galaxies

11:02 am

Galaxies without end: A new radio telescope sky survey has discovered hundreds of thousands of previously unknown galaxies.

This discovery is part of a major release of papers outlining a number of discoveries made by this new sky survey.

I could of course also subheaded this post “The uncertainty of science.” Wanna bet that even with this discovery we have only seen the tip of the iceberg of the number of galaxies out there?

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Astronomers detect matter falling into black hole at 30% of the speed of light

9:05 am

Using the XMM-Newton X-ray space telescope astronomers have detected matter falling into the central supermassive black hole at 30% of the speed of light in a galaxy a billion light years away.

Using data from XMM-Newton, Prof. Pounds and his collaborators looked at X-ray spectra (where X-rays are dispersed by wavelength) from the galaxy PG211+143. This object lies more than one billion light years away in the direction of the constellation Coma Berenices, and is a Seyfert galaxy, characterised by a very bright AGN [active galactic nucleus] resulting from the presence of the massive black hole at its nucleus.

The researchers found the spectra to be strongly red-shifted, showing the observed matter to be falling into the black hole at the enormous speed of 30 per cent of the speed of light, or around 100,000 kilometres per second. The gas has almost no rotation around the hole, and is detected extremely close to it in astronomical terms, at a distance of only 20 times the hole’s size (its event horizon, the boundary of the region where escape is no longer possible).

Astronomers have theorized for several decades that the reason Seyfert galaxies have such active nuclei is exactly because matter is falling into the central black hole. This observation appears to confirm that theory.

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Ten times more galaxies than previously believed

9:44 am

The uncertainty of science: A new analysis from Hubble and other telescope data suggests that the universe actually contains ten times more galaxies than previously estimated, several trillion instead of the past estimate of 100 to 200 billion.

I would not bet much money on this conclusion. I suspect that further research will find even more galaxies, since our deep observations of the universe are at the moment confined to a mere handful of Hubble deep field images that cover only a few tiny specks of space.

This new analysis however did confirm previous estimates that suggest the universe has evolved and changed significantly over time.

In analysing the data the team looked more than 13 billion years into the past. This showed them that galaxies are not evenly distributed throughout the Universe’s history. In fact, it appears that there were a factor of 10 more galaxies per unit volume when the Universe was only a few billion years old compared with today. Most of these galaxies were relatively small and faint, with masses similar to those of the satellite galaxies surrounding the Milky Way.

These results are powerful evidence that a significant evolution has taken place throughout the Universe’s history, an evolution during which galaxies merged together, dramatically reducing their total number. “This gives us a verification of the so-called top-down formation of structure in the Universe,” explains Conselice.

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“They can’t be real.”

8:56 am

The uncertainty of science: Astronomers have now detected and measured a new class of large but very dim galaxy that previously was not expected to exist.

‘Ultradiffuse’ galaxies came to attention only last year, after Pieter van Dokkum of Yale University in New Haven, Connecticut, and Roberto Abraham of the University of Toronto in Canada built an array of sensitive telephoto lenses named Dragonfly. The astronomers and their colleagues observed the Coma galaxy cluster 101 megaparsecs (330 million light years) away and detected 47 faint smudges.

“They can’t be real,” van Dokkum recalls thinking when he first saw the galaxies on his laptop computer. But their distribution in space matched that of the cluster’s other galaxies, indicating that they were true members. Since then, hundreds more of these galaxies have turned up in the Coma cluster and elsewhere.

Ultradiffuse galaxies are large like the Milky Way — which is much bigger than most — but they glow as dimly as mere dwarf galaxies. It’s as though a city as big as London emitted as little light as Kalamazoo, Michigan.

More significantly, they have now found that these dim galaxies can be as big and as massive as the biggest bright galaxies, suggesting that, surprise!, there are a lot more stars and mass hidden out there and unseen than anyone had previously predicted.

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Astronomers find no evidence of nearby alien civilizations

8:33 am

New observations of the best candidate galaxies now suggests that very advanced civilizations are very rare or don’t exist in the local universe.

They looked at several hundred nearby galaxies that emitted a high amount of mid-infrared radiation, which could possibly be produced as the waste heat from civilizations using energy on galactic scales.

Professor Michael Garrett (ASTRON & University of Leiden) has used radio measurements of the very best candidate galaxies and discovered that the vast majority of these systems present emission that is best explained by natural astrophysical processes. In particular, the galaxies as a sample, follow a well-known global relation that holds for almost all galaxies – the so-called “Mid-Infrared Radio correlation”. The presence of radio emission at the levels expected from the correlation, suggests that the mid-IR emission is not heat from alien factories but more likely emission from dust – for example, dust generated and heated by regions of massive star formation.
As Professor Garrett explains: “the original research at Penn State has already told us that such systems are very rare but the new analysis suggests that this is probably an understatement, and that advanced Kardashev Type III civilisations basically don’t exist in the local Universe. In my view, it means we can all sleep safely in our beds tonight – an alien invasion doesn’t seem at all likely!”.

Joking aside, Professor Garrett is still looking at a few candidate galaxies that lie off of the astrophysical correlation: “Some of these systems definitely demand further investigation but those already studied in detail turn out to have a natural astrophysical explanation too. It’s very likely that the remaining systems also fall into this category but of course it’s worth checking just in case!”

Obviously, the uncertainty of these results is quite high. Nonetheless, the results indicate that either humanity really is the only intelligent species in this part of the universe, or advanced civilizations are far more efficient in their use of energy than is reasonable to assume.

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Is it dark matter, or a previously unrecognized failure of Newton?

9:42 am

Dark matter?

The uncertainty of science: Using new data gathered by the 10-meter Keck telescope in Hawaii, astronomers have found that the outer stars of elliptical galaxies exhibit the same behavior as the outer stars of spirals, suggesting once again the existence of dark matter.

One of the most important scientific discoveries of the 20th century was that the spectacular spiral galaxies, such as our own Milky Way, rotate much faster than expected, powered by [the] extra gravitational force of invisible “dark matter” as it is now called. Since this discovery 40 years ago, we have learned that this mysterious substance, which is probably an exotic elementary particle, makes up about 85 percent of the mass in the Universe, leaving only 15 percent to be the ordinary stuff encountered in our everyday lives. Dark matter is central to our understanding of how galaxies form and evolve – and is ultimately one of the reasons for the existence of life on Earth – yet we know almost nothing about it.

“The surprising finding of our study was that elliptical galaxies maintain a remarkably constant circular speed out to large distances from their centers, in the same way that spiral galaxies are already known to do,” said Cappellari. “This means that in these very different types of galaxies, stars and dark matter conspire to redistribute themselves to produce this effect, with stars dominating in the inner regions of the galaxies, and a gradual shift in the outer regions to dark matter dominance.”

What is most fascinating about this press release, however, is that it also noted that dark matter is only one explanation for the data, and that the failure of Newtonian physics at large distances, instead of dark matter, might also provide an explanation.

However, the [solution] does not come out naturally from models of dark matter, and some disturbing fine-tuning is required to explain the observations. For this reason, the [problem] even led some authors to suggest that, rather than being due to dark matter, it may be due to Newton’s law of gravity becoming progressively less accurate at large distances. Remarkably, decades after it was proposed, this alternative theory (without dark matter) still cannot be conclusively ruled out.

Physicists call this other theory MOND, for modified Newtonian dynamics. It is not a very popular theory, however, and is almost always ignored, even though it appears to work as well as dark matter to explain the motion of stars in galaxies. Instead, most scientists favor dark matter.

For this press release to mention it as suggests the new data favors it over dark matter, which would make this a significant discovery.

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No obvious evidence of advanced civilizations in 100,000 galaxies

10:57 pm

A search for evidence of advanced civilizations in the WISE orbiting telescope database has come up mostly empty.

Theoretical physicist Freeman Dyson proposed in the 1960s that advanced alien civilizations beyond Earth could be detected by the telltale evidence of their mid-infrared emissions. It was not until space-based telescopes like the WISE satellite that it became possible to make sensitive measurements of this radiation emitted by objects in space.

Roger Griffith, a postbaccalaureate researcher at Penn State and the lead author of the paper, scoured almost the entire catalog of the WISE satellite’s detections — nearly 100 million entries — for objects consistent with galaxies emitting too much mid-infrared radiation. He then individually examined and categorized around 100,000 of the most promising galaxy images. Wright reports, “We found about 50 galaxies that have unusually high levels of mid-infrared radiation. Our follow-up studies of those galaxies may reveal if the origin of their radiation results from natural astronomical processes, or if it could indicate the presence of a highly advanced civilization.”

Though the spin of the article is that no clear evidence of alien civilizations was found, I am most intrigued by those 50 candidate galaxies.

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A giant black hole in a tiny galaxy

10:13 am

The uncertainty of science: Astronomers have unexpectedly discovered a supermassive black hole in the center of a nearby tiny galaxy, comprising almost 18% of the galaxy’s entire mass.

To weigh the beast, the researchers measured the velocity of stars whipping about the galaxy’s centre using an infrared spectrometer on the Gemini North telescope atop Mauna Kea in Hawaii. The high velocity of the stars is best explained by a central black hole that tips the scales at 21 million times the Sun’s mass, concluded Seth’s team. That is more than five times heavier than the black hole at the centre of the Milky Way — even though M60-UCD1 has an estimated diameter of about one-six-hundredth that of our home galaxy.

Previously astronomers had believed that the size of a galaxy would predict the size of its central black hole, and that a galaxy this small would not house such a supermassive object. This find upsets those theories.

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The Milky Way’s most distant stars

11:18 pm

Astronomers have discovered the two most distant stars of the Milky Way.

Both stars are red giants, aging suns that shine so brightly observers can see them from afar. One star is about 890,000 light-years from Earth in the constellation Pisces—33 times farther from the Milky Way’s center than we are and well beyond the edge of the galactic disk. The only other Milky Way member at a comparable distance is a small galaxy named Leo I, which orbits ours at a distance of 850,000 light-years. If the star in Pisces revolves on a circular path as fast as we do, it takes some eight billion years to complete a single orbit around the galaxy. That’s more than half the age of the universe.

The other newfound star is about 780,000 light-years distant in the constellation Gemini and more than a million light-years from the other star. For comparison, the previous record-breaking individual star was only about half a million light-years from Earth.

Both stars are so far outside the galaxy’s disk that it is quite possible that they are not part of the Milky Way at all.

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The Milky Way shrinks

9:49 pm

The uncertainty of science: New research by astronomers suggests that the Milky Way is about half as massive as previously estimated.

In the sixties I remember astronomers claiming that the Milky Way was twice as big as Andromeda. Then it was considered half as big. Most recently it was considered about the same size. This new research makes it half as big as Andromeda again.

In other words, the data is very uncertain, and the scientists really don’t have a good handle on it. None of these conclusions should be taken very seriously. All we really know at this point is that the Milky Way and Andromeda are approximately comparable.

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Telescope teamwork produces spectacular galaxy image

11:55 am

M106

Combining images from a host of space and ground-based telescopes, astronomers have created a spectacular image of the galaxy M106.

This galactic fireworks display is taking place in NGC 4258 (also known as M106), a spiral galaxy like the Milky Way. This galaxy is famous, however, for something that our Galaxy doesn’t have – two extra spiral arms that glow in X-ray, optical, and radio light. These features, or anomalous arms, are not aligned with the plane of the galaxy, but instead intersect with it.

The anomalous arms are seen in this new composite image of NGC 4258, where X-rays from NASA’s Chandra X-ray Observatory are blue, radio data from the NSF’s Karl Jansky Very Large Array are purple, optical data from NASA’s Hubble Space Telescope are yellow and blue, and infrared data from NASA’s Spitzer Space Telescope are red.

A new study of these anomalous arms made with Spitzer shows that shock waves, similar to sonic booms from supersonic planes, are heating large amounts of gas – equivalent to about 10 million Suns. What is generating these shock waves? Radio data shows that the supermassive black hole at the center of NGC 4258 is producing powerful jets of high-energy particles. Researchers thinkthat these jets strike the disk of the galaxy and generate shock waves. These shock waves, in turn, heat some of the gas – composed mainly of hydrogen molecules – to thousands of degrees.

The astronomers also used the Herschel Space Observatory to confirm the data from Spitzer.

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