Tag Archives: galaxies

Monster Galaxies Gobble Smaller Neighbors to Bulk Up

Massive galaxies have stopped making their own stars and started engulfing little nearby galaxies instead, according to a new survey of 22,000 galaxies. Remnants of cannibalized galaxies can still be seen in our own galaxy, but the Milky Way will ultimately get its comeuppance too: We’ll all be devoured by Andromeda in just 5 billion years or so like some chocolate nougat candy bar.

Smaller galaxies are just very efficient at creating stars from gas, whereas the most massive ones hardly produce any new stars themselves. As galaxies grow, they have more gravity that allows them to easily pull in their neighbors.

“All galaxies start off small and grow by collecting gas and quite efficiently turning it into stars,” says Aaron Robotham from the University of Western Australia node of the International Centre for Radio Astronomy Research (ICRAR). “Then every now and then they get completely cannibalized by some much larger galaxy.”

Star formation slows down in really massive galaxies because of extreme feedback events in the active galactic nucleus, the bright region at the center of a galaxy. Astronomers aren’t sure about the mechanism, but one likely possibility is that the active galactic nucleus basically cooks the gas, preventing it from cooling down to form stars. Ultimately, gravity will cause all the galaxies in bound groups and clusters to merge into super-giant galaxies.

The team collected almost all of the data using the Anglo-Australian Telescope in New South Wales as part of the 7-year-long Galaxy And Mass Assembly (GAMA) survey led by ICRAR’s Simon Driver. The work was published in Monthly Notices of the Royal Astronomical Society this week. 

What’s more, our own Milky Way is at a tipping point and is expected to grow mainly by eating smaller galaxies rather than by collecting gas. “The Milky Way hasn’t merged with another large galaxy for a long time but you can still see remnants of all the old galaxies we’ve cannibalized,” Robotham says in a news release. “We’re also going to eat two nearby dwarf galaxies, the Large and Small Magellanic Clouds, in about four billion years.”

But the Milky Way is eventually going to merge with the nearby Andromeda galaxy in 5 billion years. “Technically, Andromeda will eat us because it’s the more massive one,” he adds.

This simulation shows what will happen when the Milky Way and Andromeda get closer together, collide, and then finally merge into an even bigger galaxy:

 

 

Image: Simon Driver and Aaron Robotham, ICRAR
Video: Chris Power (ICRAR-UWA), Alex Hobbs (ETH Zurich), Justin Reid (University of Surrey), Dave Cole (University of Central Lancashire) and the Theoretical Astrophysics Group at the University of Leicester with video production by Pete Wheeler, ICRAR

Read more: http://www.iflscience.com/space/monster-galaxies-gobble-smaller-neighbors-bulk

Preserving the X-ray Universe for future generations

A collage of the eight images NASA's Chandra X-ray Observatory has released from its archive

October is designated as American Archive Month, to promote an awareness of the importance of historical records. While many think ‘archive’ may only apply to books and letters, there are other important archives. Archives are used for major telescopes and observatories, including NASA’s Chandra X-ray Observatory.

The primary role of the Chandra Data Archive (CDA) is to store and distribute data so the astronomical community, as well as the general public, have access to it. The CDA does this with the aid of powerful search engines. This archive collection will preserve the legacy of the Chandra mission for generations.

In celebration of American Archive Month, the Chandra team chose images from a group of eight objects in the CDA to be released to the public for the first time. These are but a few of the thousands of objects that Chandra’s archive has made permanently available to the public. 

G266.2-1.2

Chandra’s observation of this supernova remnant, located around 2,400 light years away in the constellation Vela, revealed extremely high-energy particles. These particles are produced as the shock wave from the explosion expands into interstellar space. The X-rays from Chandra (purple) have been combined with optical data from the Digitized Sky Survey (red, green, and blue).

3C353

This is a wide and double-lobed jet, generated by a supermassive black hole at the centre of a galaxy about 410 million light years away, in the constellation Ophiuchus. The jet itself is the tiny point in the centre while the giant plumes of radiation can be seen in X-rays from Chandra (purple) and radio data from the Very Large Array (orange).

NGC 3576

This nebula is located around 9,000 light years away from Earth, in the Sagittarius arm of the Milky Way galaxy. The scattered X-ray data detected by Chandra (blue) are probably due to the winds from young, massive stars blowing throughout the nebula. Optical data from ESO are shown in orange and yellow.

NGC 4945

This galaxy is similar in appearance to our own, but contains a much more active supermassive black hole within the white area near the top. NGC 4945 is only about 13 million light years from Earth, in the constellation Centaurus, and is seen edge-on. X-rays from Chandra (blue), have been overlaid on an optical image from the European Space Observatory to reveal the presence of the supermassive black hole at the centre of this galaxy.

IC 1396A

The nebula otherwise known as the Elephant Trunk Nebula is located about 2,800 light years away in the constellation of Cepheus. Radiation and winds from massive young stars seem to be triggering new generations of stars to form. X-rays from Chandra (purple) have been combined with optical (red, green, and blue) and infrared (orange and cyan) to give a more complete picture of this source.

3C 397 (G41.1-0.3)

Also known as G41.1-0.3, this is a Galactic supernova remnant with an unusual shape found around 33,000 light years away in the constellation Aquila. Its box-like shape is possibly produced as the heated remains of the exploded star interacts with the cooler gas enveloping it. The exploded star was detected by Chandra in X-rays (purple) and this composite of the area around 3C 397 also contains infrared emission from Spitzer (yellow) and optical data from the Digitized Sky Survey (red, green, and blue).

SNR B0049-73.6

This supernova is located approximately about 180,000 light years away in the constellation Tucana, within our neighbouring galaxy of the Small Magellanic Cloud. Observations of the dynamics as well as the composition of the debris from the explosion provide evidence that the explosion was produced by the collapse of the central core of a star. In this image, X-rays from Chandra (purple) are combined with infrared data from the 2MASS survey (red, green, and blue).

NGC 6946

Nicknamed the ‘Fireworks Galaxy’, this medium-sized, face-on spiral galaxy is found about 22 million light years away from Earth in the constellation Cygnus. Eight supernovae have been observed to explode in the arms of this galaxy in the last 100 years. Chandra observations (purple) have revealed three of the oldest supernovas ever detected in X-rays. This composite image also includes optical data from the Gemini Observatory in red, yellow, and cyan.

Photo Gallery

Read more: http://www.iflscience.com/space/preserving-x-ray-universe-future-generations

Newly Discovered “Cosmic Wall” Is 1.3 BILLION Light-Years Across

If we could zoom out of the universe, we would see galaxies organized in clusters, and those clusters form superclusters that are distributed along dense filaments between under-dense voids. On the largest scales the universe looks the same everywhere, but looking closer to these filaments we can see peculiar and unique structures.

One of them is the newly discovered BOSS Great Wall. The system consists of 830 galaxies and has a mass of 280 million billion suns. It is about 5 billion light-years away from the Milky Way, and it is 1.3 billion light-years in diameter.

The BOSS Great Wall is not the first cosmic wall discovered. The largest structure in the nearby universe is the Sloan Great Wall, which has about half the mass of theBOSS Great Wall. Claims on these structures are quite contentious, though, as although they appear as a single structure in the sky, they are not bound together by gravity like clusters and superclusters.

“We found two walls of galaxies […]that are larger in volume and diameter than any previously known superclusters. Together they form the system of the BOSS Great Wall, which is more extended than any other known structure,” said the researchers in the paper, which will appear in Astronomy & Astrophysics.

According to our current model of the universe, structures shouldn’tbe larger than 1.2 billion light-years, but this is not the first time that scientists have claimed the existence of structures larger than what the model predicts.

The BOSS Great Wall was discovered by Heidi Lietzen of the Canary Islands Institute of Astrophysics and her team. They were observing a large chunk of the universe between 4.5 to 6.4 billion light-years from Earth.

It was so much bigger than anything else in this volume, Lietzen said to New Scientist.

While this mass grouping is definitely interesting, other scientists are questioning the discovery.

I dont entirely understand why they are connecting all of these features together to call them a single structure, says Allison Coil of the University of California, San Diego to New Scientist. There are clearly kinks and bends in this structure that dont exist, for example, in the Sloan Great Wall.

[H/T: New Scientist]

Read more: http://www.iflscience.com/space/has-new-cosmic-wall-been-found

Fly through distant galaxies with Hubble eXtreme Deep Field

 
Ever wonder what it’d be like to fly through thousands of galaxies spanning back 13.2 billion years in time? Nearly every dot or smear of light you see is a galaxy imaged by NASA’s Hubble Space Telescope, and there’s now a few 3D visualizations for you to explore. 
 
In 2004, the Hubble Ultra Deep Field (HUDF), with its Advanced Camera for Surveys, provided an unprecedented view of distant galaxies in a small patch of space — about one-hundredths the size of the full moon — in the constellation Fornax. It gave us a look at 13 billion years into the past. Then, the Wide Field Camera 3 installed in 2009 extended the vision into near-infrared light. Hubble Ultra Deep Field infrared (HUDF-IR) detected primordial galaxies as they appeared just 600 million years after the Big Bang. These premier cameras took more than 2,000 images of the same field for a total of 50 days, with a total exposure time of 2 million seconds.
 
In September 2012, the Hubble eXtreme Deep Field (HXDF) combined a decade of Hubble images — along with a complete census of archival datasets — to assemble mankind’s deepest-ever view of the universe (pictured above). Even though HXDF is a smaller field of view than HUDF, it can reach fainter galaxies — roughly 5,500. The faintest galaxies are one ten-billionth the brightness of what our eyes can see. 
 
This is a scientific visualization depicting a flight through the HXDF galaxies. Using distances (measured and estimated) for about 3,000 galaxies from a 13-billion-light-year dataset, astronomers and visualizers constructed a 3D model of the galaxy distribution. The video ends in blackness, but HubbleSite is quick to explain how that’s not because more distant galaxies don’t exist — but because those galaxies haven’t been observed yet. 
 
 
Check out the amazing collection of videos at HubbleSite, including one of HUDF
 
[HubbleSite; hat tip io9]
 
Credits:
Visualization: F. Summers, L. Frattare, T. Davis, Z. Levay, and G. Bacon (STScI)
Data: G. Illingworth, P. Oesch, and D. Magee (UCSC)
 

Read more: http://www.iflscience.com/space/fly-through-distant-galaxies-hubble-extreme-deep-field

Largest-Ever Simulated Universe Created With Supercomputers

One of the principles of science is that by repeating experiments we can learn some fundamental laws of nature. This is complicated when we are trying to learn about the secrets of the universe as a whole, though, because we only have one universe. And while we can’t study multiverses, we might be able to do the next best thing.

Using supercomputers, physicists have created the largest-ever simulated universe. They created detailed catalogues of fake galaxies that can be compared with large-scale observations of real galaxies. This makes for a better understanding of the universe, as we can know the cosmological parameters with more precision.

Francisco Kitaura, lead author of the research, said in astatement: “We have developed the necessary techniques to generate thousands of simulated galaxy catalogues, reproducing the statistical properties of the observations.” The research is published inMonthly Notices of the Royal Astronomical Society.

The simulated objects were created with the intention to compare them with the real objects seen in the Baryon Oscillation Spectroscopic Survey, or BOSS, whichhas scanned a large part of the sky and precisely measured the distance of more than 1 million galaxies up to 4.5 billion light-years away.

The distribution of galaxies in the universe is not random. Galaxies and clusters of galaxies are distributed in the so-called cosmic web. The galaxies follow the filaments of the web with large voids between groups of galaxies. The formations of the web happened right after the Big Bang, with its evolution being dictated bydark matter.

Dark matter is a mysterious form of matter that only interacts gravitationally. We can see the effect of it on galaxies, but we are yet to observe it in the lab. Constraining its properties was one of the challenges in preparing this simulation. Other challenges included having a realistic distribution of galaxies and including the correct mass of the galaxies, which strongly depends on their environments.

“Now we understand better the relation between the galaxy distribution and the underlying large-scale dark matter field,”said Kitaura.”We will continue refining our methods to further understand the structures we observe in the universe.”

A 2D map of galaxydistribution. On the left is real observation, and on the right isthe simulated data.F. Kitaura

Photo Gallery

Read more: http://www.iflscience.com/space/simulating-large-scale-universe-supercomputers

Hubble Captures the Glowing Heart of a Spiral Galaxy

Here’s a look deep into the heart of a nearby spiral galaxy. 

NGC 1433 is about 32 million light-years from Earth, and it belongs to a type of active galaxy known as Seyfert galaxies. These are known for their very luminous centers, which can be as bright as the entire Milky Way. They account for 10 percent of all galaxies.

The centers of most galaxies, including ours, are thought to contain a supermassive black hole orbited by a disk of material falling in (called accretion disks). With Seyfert galaxies, ultraviolet light should also emanate from the accretion disk around their central black hole.

Using the Hubble Space Telescope, the Legacy ExtraGalactic UV Survey (LEGUS) will examine a range of properties from 50 nearby galaxies, including NGC 1433. Studying these galaxies in the UV part of the spectrum informs researchers about how gas and dust behave near the black hole. 

Hubble captured this view of NGC 1433 using a mix of UV, visible, and infrared light. 

Earlier observations from the Atacama Large Millimeter/submillimeter Array (ALMA) revealed a surprising spiral structure in the molecular gas close to the center of NGC 1433. Astronomers have also found a jet of material flowing away from its black hole and extending for just 150 light-years — that’s the smallest molecular outflow ever observed in a galaxy beyond our own.

[Via European Space Agency]

Read more: http://www.iflscience.com/space/hubble-captures-glowing-heart-spiral-galaxy

Our Home Supercluster Gets a Map and a Name

Where in the universe is the Milky Way?

Galaxies like ours huddle in clusters, and large-scale systems of galaxies, called superclusters, have vague boundaries that are difficult to define (especially from the inside): They’re all drawn to each other and interconnected in a web of filaments. Now for the first time, astronomers have constructed a map of the local universe. They’ve named our home supercluster Laniakea, Hawaiian for “immeasurable heaven.” The work was published in Nature this week. 

By examining the motions of galaxies, a team of cosmic map makers led by R. Brent Tully from the University of Hawaii charted the distribution of matter in the universe to identify superclusters. A galaxy stuck between two superclusters will be caught in a gravitational tug-of-war. The balance of these forces determines the galaxy’s motion, and measuring the velocity helps define the region of space where each supercluster dominates. With a catalog of 8,000 galaxies’ velocities, the team built a galactic distribution map and located the points where cosmic flows — along which galaxies travel — diverge.

The Laniakea supercluster, they found, is 520 million light-years in diameter and contains the mass of 100 million billion suns within 100,000 galaxies. Its name pays tribute to Polynesian navigators who used knowledge of the heavens to voyage across the Pacific Ocean. 

In the image above, the colors represent density: red for high densities and blue for voids with little matter. Individual galaxies are shown as white dots, and velocity flow streams within the region gravitationally dominated by Laniakea are shown in white. Importantly, the orange line encloses the outer limits of these streams.

The team defined the edge of a supercluster as the boundary at which flow lines diverge: On one side of the line, galaxies flow towards one gravitational center, Nature explains, and beyond it, they flow towards another. “It’s like water dividing at a watershed, where it flows either to the left or right of a height of land,” Tully explains.

After mapping the boundaries of Laniakea, the team discovered that the Milky Way — along with dozens of other galaxies in our Local Group — resides at the outskirts of the supercluster. We’re the blue dot in the picture above. 

“We have finally established the contours that define the supercluster of galaxies we can call home,” Tully says in a news release. “This is not unlike finding out for the first time that your hometown is actually part of much larger country that borders other nations.” 

Laniakea also includes the Virgo cluster (our nearest neighbor, at 55 million light-years away) and Norma-Hydra-Centaurus. The latter is also known as the Great Attractor, which serves as a gravitation focal point that influences the motion of galaxies, Washington Post explains. Our supercluster is flowing towards the Shapley concentration of galaxies, in the upper left corner of the image above.

Image: SDvision interactive visualization software by DP at CEA/Saclay, France

Video: Nature Video

Read more: http://www.iflscience.com/space/our-home-supercluster-gets-map-and-name