Dwarf Dark Matter Galaxy Hides In Einstein Ring

The large blue light is a lensing galaxy in the foreground, called SDP81, and the red arcs are the distorted image of a more distant galaxy. By analyzing small distortions in the red, distant galaxy, astronomers have determined that a dwarf dark galaxy, represented by the white dot in the lower left, is companion to SDP81. The image is a composite from ALMA and the Hubble. Image: Y. Hezaveh, Stanford Univ./ALMA (NRAO/ESO/NAOJ)/NASA/ESA Hubble Space Telescope

Everybody knows that galaxies are enormous collections of stars. A single galaxy can contain hundreds of billions of them. But there is a type of galaxy that has no stars. That’s right: zero stars.

These galaxies are called Dark Galaxies, or Dark Matter Galaxies. And rather than consisting of stars, they consist mostly of Dark Matter. Theory predicts that there should be many of these Dwarf Dark Galaxies in the halo around ‘regular’ galaxies, but finding them has been difficult.

Now, in a new paper to be published in the Astrophysical Journal, Yashar Hezaveh at Stanford University in California, and his team of colleagues, announce the discovery of one such object. The team used enhanced capabilities of the Atacamas Large Millimeter Array to examine an Einstein ring, so named because Einstein’s Theory of General Relativity predicted the phenomenon long before one was observed.

An Einstein Ring is when the massive gravity of a close object distorts the light from a much more distant object. They operate much like the lens in a telescope, or even a pair of eye-glasses. The mass of the glass in the lens directs incoming light in such a way that distant objects are enlarged.

Einstein Rings and gravitational lensing allow astronomers to study extremely distant objects, by looking at them through a lens of gravity. But they also allow astronomers to learn more about the galaxy that is acting as the lens, which is what happened in this case.

If a glass lens had tiny water spots on it, those spots would add a tiny amount of distortion to the image. That’s what happened in this case, except rather than microscopic water drops on a lens, the distortions were caused by tiny Dwarf Galaxies consisting of Dark Matter. “We can find these invisible objects in the same way that you can see rain droplets on a window. You know they are there because they distort the image of the background objects,” explained Hezaveh. The difference is that water distorts light by refraction, whereas matter distorts light by gravity.

As the ALMA facility increased its resolution, astronomers studied different astronomical objects to test its capabilities. One of these objects was SDP81, the gravitational lens in the above image. As they examined the more distant galaxy being lensed by SDP81, they discovered smaller distortions in the ring of the distant galaxy. Hezaveh and his team conclude that these distortions signal the presence of a Dwarf Dark Galaxy.

But why does this all matter? Because there is a problem in the Universe, or at least in our understanding of it; a problem of missing mass.

Our understanding of the formation of the structure of the Universe is pretty solid, at least in the larger scale. Predictions based on this model agree with observations of the Cosmic Microwave Background (CMB) and galaxy clustering. But our understanding breaks down somewhat when it comes to the smaller scale structure of the Universe.

One example of our lack of understanding in this area is what’s known as the Missing Satellite Problem. Theory predicts that there should be a large population of what are called sub-halo objects in the halo of dark matter surrounding galaxies. These objects can range from things as large as the Magellanic Clouds down to much smaller objects. In observations of the Local Group, there is a pronounced deficit of these objects, to the tune of a factor of 10, when compared to theoretical predictions.

Because we haven’t found them, one of two things needs to happen: either we get better at finding them, or we modify our theory. But it seems a little too soon to modify our theories of the structure of the Universe because we haven’t found something that, by its very nature, is hard to find. That’s why this announcement is so important.

The observation and identification of one of these Dwarf Dark Galaxies should open the door to more. Once more are found, we can start to build a model of their population and distribution. So if in the future more of these Dwarf Dark Galaxies are found, it will gradually confirm our over-arching understanding of the formation and structure of the Universe. And it’ll mean we’re on the right track when it comes to understanding Dark Matter’s role in the Universe. If we can’t find them, and the one bound to the halo of SDP81 turns out to be an anomaly, then it’s back to the drawing board, theoretically.

It took a lot of horsepower to detect the Dwarf Dark Galaxy bound to SDP81. Einstein Rings like SDP81 have to have enormous mass in order to exert a gravitational lensing effect, while Dwarf Dark Galaxies are tiny in comparison. It’s a classic ‘needle in a haystack’ problem, and Hezaveh and his team needed massive computing power to analyze the data from ALMA.

ALMA will consist of 66 individual antennae like these when it is complete. The facility is located in the Atacama Desert in Chile, at 5,000 meters above sea level. Credit: ALMA (ESO / NAOJ / NRAO)
ALMA will consist of 66 individual antennae like these when it is complete. The facility is located in the Atacama Desert in Chile, at 5,000 meters above sea level. Credit: ALMA (ESO / NAOJ / NRAO)

ALMA, and the methodology developed by Hezaveh and team will hopefully shed more light on Dwarf Dark Galaxies in the future. The team thinks that ALMA has great potential to discover more of these halo objects, which should in turn improve our understanding of the structure of the Universe. As they say in the conclusion of their paper, “… ALMA observations have the potential to significantly advance our understanding of the abundance of dark matter substructure.”

SpaceX Dragon Launches on Science Supply Run to Station, Booster Hard Lands on Barge

KENNEDY SPACE CENTER, FL – After a 24 hour delay due to threatening clouds, a SpaceX Falcon 9 rocket soared spectacularly to orbit from the Florida Space coast today, April 14, carrying a Dragon on a science supply run bound for the the International Space Station that will help pave the way for deep space human missions to the Moon, Asteroids and Mars.

Meanwhile, SpaceX’s bold attempt to land and recover the 14 story tall first stage of the Falcon 9 rocket successfully reached a tiny ocean floating barge in the Atlantic Ocean, but tilted over somewhat over in the final moments of the approach, and tipped over after landing and broke apart. Here’s a Vine video posted on Twitter by Elon Musk:

See the video of the launch, below.

SpaceX will continue with attempt to soft land and recover the rocket on upcoming launches, which was a secondary goal of the company. SpaceX released some imagery and video with a few hours of the landing attempt.

“Looks like Falcon landed fine, but excess lateral velocity caused it to tip over post landing,” tweeted SpaceX CEO Elon Musk.

Falcon 9 first stage approaches Just Read the Instructions. Image of SpaceX Falcon 9 first start booster in final moments of hard landing on ocean going barge after CRS-6 launch. Credit: SpaceX
Falcon 9 first stage approaches Just Read the Instructions. Image of SpaceX Falcon 9 first start booster in final moments of hard landing on ocean going barge after CRS-6 launch. Credit: SpaceX

The Falcon 9 first stage was outfitted with four landing legs and grid fins to enable the landing attempt, which is a secondary objective of SpaceX.

The top priority was to safely launch the Falcon 9 and deliver critical supplies to the station with the Dragon cargo vessel.

“Five years ago this week, President Obama toured the same SpaceX launch pad used today to send supplies, research and technology development to the ISS,” said NASA Administrator Charles Bolden.

“Back then, SpaceX hadn’t even made its first orbital flight. Today, it’s making regular flights to the space station and is one of two American companies, along with The Boeing Company, that will return the ability to launch NASA astronauts to the ISS from U.S. soil and land then back in the United States. That’s a lot of progress in the last five years, with even more to come in the next five.”

“Looks like Falcon landed fine, but excess lateral velocity caused it to tip over post landing,” tweeted SpaceX CEO Elon Musk.

A chase plane captured dramatic footage of the landing on the ocean going platform known as the ‘autonomous spaceport drone ship’ (ASDS).

It was pre-positioned some 200 to 250 miles offshore of the Carolina coast in the Atlantic Ocean along the rockets flight path flying along the US Northeast coast to match that of the ISS.

The ASDS measures only 300 by 100 feet, with wings that extend its width to 170 feet.

SpaceX Falcon 9 and Dragon blastoff from Space Launch Complex 40 at Cape Canaveral Air Force Station in Florida on April 14, 2015 at 4:10 p.m. EDT  on the CRS-6 mission to the International Space Station. Credit: Ken Kremer/kenkremer.com
SpaceX Falcon 9 and Dragon blastoff from Space Launch Complex 40 at Cape Canaveral Air Force Station in Florida on April 14, 2015 at 4:10 p.m. EDT on the CRS-6 mission. to the International Space Station. Credit: Ken Kremer/kenkremer.com

Overall CRS-6 is the sixth SpaceX commercial resupply services mission and the seventh trip by a Dragon spacecraft to the station since 2012.

CRS-6 marks the company’s sixth operational resupply mission to the ISS under a $1.6 Billion contract with NASA to deliver 20,000 kg (44,000 pounds) of cargo to the station during a dozen Dragon cargo spacecraft flights through 2016 under NASA’s original Commercial Resupply Services (CRS) contract.

The SpaceX Falcon 9 with the Dragon vessel for the CRS-6 launch lifts off for the International Space Station at 4:10 PM eastern time on 4/14/15 from Cape Canaveral.  Credit: Alex Polimeni/AmericaSpace
The SpaceX Falcon 9 with the Dragon vessel for the CRS-6 launch lifts off for the International Space Station at 4:10 PM eastern time on 4/14/15 from Cape Canaveral. Credit: Alex Polimeni/AmericaSpace

Dragon is packed with more than 4,300 pounds (1915 kilograms) of scientific experiments, technology demonstrations, crew supplies, spare parts, food, water, clothing and assorted research gear for the six person Expedition 43 and 44 crews serving aboard the ISS.

After a three day orbital chase, the Dragon spacecraft with rendezvous with the million post Earth orbiting outpost Friday morning April 17.

After SpaceX engineers on the ground maneuver the Dragon close enough to the station, European Space Agency (ESA) astronaut Samantha Cristoforetti will use the station’s 57.7-foot-long (17-meter-long) robotic arm to reach out and capture Dragon at approximately 7 a.m. EDT on April 17.

Cristoforetti will be assisted by fellow Expedition 43 crew member and NASA astronaut
Terry Virts, as they work inside the stations seven windowed domed cupola to berth Dragon at the Earth-facing port of the Harmony module.

The series of images shows the journey the SpaceX Falcon 9 rocket and Dragon spacecraft from its launch at 4:10 p.m. EDT on Tuesday April 14, 2015 from Space Launch Complex 40 at Cape Canaveral Air Force Station in Florida, to solar array deployment. Credit: NASA TV
The series of images shows the journey the SpaceX Falcon 9 rocket and Dragon spacecraft from its launch at 4:10 p.m. EDT on Tuesday April 14, 2015 from Space Launch Complex 40 at Cape Canaveral Air Force Station in Florida, to solar array deployment. Credit: NASA TV

Watch for Ken’s continuing onsite coverage of the CRS-6 launch from the Kennedy Space Center and Cape Canaveral Air Force Station.

Stay tuned here for Ken’s continuing Earth and planetary science and human spaceflight news.

Ken Kremer

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Learn more about SpaceX, Mars rovers, Orion, Antares, MMS, NASA missions and more at Ken’s upcoming outreach events:

Apr 18/19: “Curiosity explores Mars” and “NASA Human Spaceflight programs” – NEAF (NorthEast Astronomy Forum), 9 AM to 5 PM, Suffern, NY, Rockland Community College and Rockland Astronomy Club

Peer Into the Distant Universe: How to See Quasars With Backyard Telescopes

“How far can you see with that thing?”

It’s a common question overhead at many public star parties in reference to telescopes.

In the coming weeks as the Moon passes Full and moves out of the evening sky, we’d like to challenge you to hunt down a bright example of one of the most distant and exotic objects known: a quasar.

To carry out this feat, you’ll need a ‘scope with at least an aperture of 20 centimetres or greater, dark skies, and patience.

Although more than 200,000 of quasars are currently known and they’re some of the most luminous objects in the universe, they’re also tremendously distant. A very few are brighter than magnitude +14, about the brightness of Pluto. Most quasars have an absolute magnitude rivaling our Sun, though if you plopped one down 33 light years away, we’d definitely have other things to worry about.
Continue reading “Peer Into the Distant Universe: How to See Quasars With Backyard Telescopes”

What is Gravitational Lensing?

Gravity’s a funny thing. Not only does it tug away at you, me, planets, moons and stars, but it can even bend light itself. And once you’re bending light, well, you’ve got yourself a telescope.

Everyone here is familiar with the practical applications of gravity. If not just from exposure to Loony Tunes, with an abundance of scenes with an anthropomorphized coyote being hurled at the ground from gravitational acceleration, giant rocks plummeting to a spot inevitably marked with an X, previously occupied by a member of the “accelerati incredibilus” family and soon to be a big squish mark containing the bodily remains of the previously mentioned Wile E. Coyote.

Despite having a very limited understanding of it, Gravity is a pretty amazing force, not just for decimating a infinitely resurrecting coyote, but for keeping our feet on the ground and our planet in just the right spot around our Sun. The force due to gravity has got a whole bag of tricks, and reaches across Universal distances. But one of its best tricks is how it acts like a lens, magnifying distant objects for astronomy.

Continue reading “What is Gravitational Lensing?”

Astronomers Discover First Mulitiple-image Gravitationally-lensed Supernova

How about four supernovae for the price of one? Using the Hubble Space Telescope, Dr. Patrick Kelly of the University of California-Berkeley along with the GLASS (Grism Lens Amplified Survey from Space) and Hubble Frontier Fields teams, discovered a remote supernova lensed into four copies of itself by the powerful gravity of a foreground galaxy cluster. Dubbed SN Refsdal, the object was discovered in the rich galaxy cluster MACS J1149.6+2223 five billion light years from Earth in the constellation Leo. It’s the first multiply-lensed supernova every discovered and one of nature’s most exotic mirages.

The rich galaxy cluster MACS J1149+2223 gained notoriety in 2012 when the most distant galaxy when the most distant galaxy found to date was discovered there through gravitational lensing.
The lensed supernova was discovered far behind the rich galaxy cluster MACS J1149.6+2223. The cluster is one of the most massive known and gained notoriety in 2012 when astronomers harnessed its powerful lensing ability to uncover the most distant galaxy known at the time. Credit: NASA/ESA/M. Postman STScI/CLASH team

Gravitational lensing grew out of Einstein’s Theory of Relativity wherein he predicted massive objects would bend and warp the fabric of spacetime. The more massive the object, the more severe the bending. We can picture this by imagining a child standing on a trampoline, her weight pressing a dimple into the fabric. Replace the child with a 200-pound adult and the surface of the trampoline sags even more.

Massive objects like the sun and even the planets warp the fabric of space. Here a planet orbits the sun but does not fall in because of its sideways orbital motion.
Massive objects like the Sun and even the planets warp the fabric of space. Here a planet orbits the Sun but doesn’t fall in because of its sideways orbital motion.

Similarly, the massive Sun creates a deep, but invisible dimple in the fabric of spacetime. The planets feel this ‘curvature of space’ and literally roll toward the Sun. Only their sideways motion or angular momentum keeps them from falling straight into the solar inferno.

Curved space created by massive objects also bends light rays. Einstein predicted that light from a star passing near the Sun or other massive object would follow this invisible curved spacescape and be deflected from an otherwise straight path. In effect, the object acts as a lens, bending and refocusing the light from the distant source into either a brighter image or multiple and distorted images. Also known as the deflection of starlight, nowadays we call it gravitational lensing.

This illustration shows how gravitational lensing works. The gravity of a large galaxy cluster is so strong, it bends, brightens and distorts the light of distant galaxies behind it. The scale has been greatly exaggerated; in reality, the distant galaxy is much further away and much smaller. Credit: NASA, ESA, L. Calcada
This illustration shows how gravitational lensing works. The gravity of a large galaxy cluster is so strong, it bends, brightens and distorts the light of distant galaxies behind it. The scale has been greatly exaggerated; in reality, the distant galaxy is much further away and much smaller. Credit: NASA, ESA, L. Calcada


Simulation of distorted spacetime around a massive galaxy cluster over time

Turns out there are lots of these gravitational lenses out there in the form of massive clusters of galaxies. They contain regular matter as well as vast quantities of the still-mysterious dark matter that makes up 96% of the material stuff in the universe. Rich galaxy clusters act like telescopes – their enormous mass and powerful gravity magnify and intensify the light of galaxies billions of light years beyond, making visible what would otherwise never be seen.

Here we see a central slice of the MACS cluster. A massive elliptical galaxy is responsible for splitting SN Refsdal into four images. It also distorts and lenses the purple-toned spiral galaxy that's host to the supernova. Credit:
This cropped image shows the central slice of the MACS J1149 galaxy cluster. A massive elliptical galaxy lenses the light of SN Refsdal into four separate images. It also distorts the purplish spiral galaxy that’s host to the supernova. Credit: NASA/ESA/M. Postman STScI/CLASH team

Let’s return to SN Refsdal, named for Sjur Refsdal, a Norwegian astrophysicist who did early work in the field of gravitational lensing.  A massive elliptical galaxy in the MACS J1149 cluster “lenses” the  9.4 billion light year distant supernova and its host spiral galaxy from background obscurity into the limelight. The elliptical’s powerful gravity’s having done a fine job of distorting spacetime to bring the supernova into view also distorts the shape of the host galaxy and splits the supernova into four separate, similarly bright images. To create such neat symmetry, SN Refsdal must be precisely aligned behind the galaxy’s center.

What looks like a galaxy with five nuclei really has just one (at center) surrounded by a mirage of four images of a distant quasar. The galaxy lies 400 million light years away; the quasar about 8 billion. Credit: NASA/ESA/Hubble
What looks like a galaxy with five nuclei really has just one (at center) surrounded by a mirage of four images of a distant quasar. The galaxy lies 400 million light years away; the quasar about 8 billion. Credit: NASA/ESA/Hubble

The scenario here bears a striking resemblance to Einstein’s Cross, a gravitationally lensed quasar, where the light of a remote quasar has been broken into four images arranged about the foreground lensing galaxy. The quasar images flicker or change in brightness over time as they’re microlensed by the passage of individual stars within the galaxy. Each star acts as a smaller lens within the main lens.

Color-composite image of lensing elliptical galaxy and distorted background  host spiral (top).The green circles show the locations of images S1–S4, while another quadruply imaged segment of the spiral arm is marked in  red. The bottom panels show two additional lensed images of the spiral host galaxy visible in the galaxy cluster field. Credit: S.L. Kelly et. all
Color-composite image of the lensing elliptical galaxy and distorted background host spiral (top). The green circles, S1-4, show the locations of the supernova images, while another quadruply imaged segment of the spiral arm is marked in red. The bottom panels show two additional lensed images of the spiral host galaxy visible in the galaxy cluster field.  Talk about a funhouse mirror! Credit: P.L. Kelly/GLASS/Hubble Frontier Fields

Detailed color images taken by the GLASS and Hubble Frontier Fields groups show the supernova’s host galaxy is also multiply-imaged by the galaxy cluster’s gravity. According to their recent paper, Kelly and team are still working to obtain spectra of  the supernova to determine if it resulted from the uncontrolled burning and explosion of a white dwarf star (Type Ia) or the cataclysmic collapse and rebound of a supergiant star that ran out of fuel (Type II).

The time light takes to travel to the Earth from each of the lensed images is different because each follows a slightly different path around the center of the lensing galaxy. Some paths are shorter, some longer. By timing the brightness variations between the individual images the team hopes to provide constraints not only on the distribution of bright matter vs. dark matter in the lensing galaxy and in the cluster but use that information to determine the expansion rate of the universe.

You can squeeze a lot from a cosmic mirage!

Searching for Alien Worlds and Gravitational Lenses from the Arctic

The quest for optimal sites to carry out astronomical observations has taken scientists to the frigid Arctic.  Eric Steinbring, who led a team of National Research Council Canada experts, noted that a high Arctic site can, “offer excellent image quality that is maintained during many clear, calm, dark periods that can last 100 hours or more.”  The new article by Steinbring and colleagues conveys recent progress made to obtain precise observations from a 600 m high ridge near the Eureka research base on Ellesmere Island, which is located in northern Canada.

The new telescope that Steinbring and his colleagues tested was located at the Polar Environment Atmospheric Research Laboratory (PEARL).  The observatory can be accessed in winter by 4 x 4 trucks via a 15 km long road from a base facility at sea-level. That base camp is operated by Environment Canada and serviced by an airstrip and resupply ship in summer.  Recently, wide-field cameras developed at the University of Toronto were deployed near Eureka to monitor thousands of stars, with the objective of expanding the exoplanet database.

Earlier work by Steinbring and colleagues indicated that data obtained from PEARL imply that clear weather prevails 68% of the time. After significant testing, the team concluded that the site “can allow reliable, uninterrupted temporal coverage during successive dark periods, in roughly 100 hour blocks with clear skies and good seeing.”

The Polar Environment Atmospheric Research Laboratory (PEARL) is located on Ellesmere Island (image credit: Left,  , right, Tobias Kerzenmacher).
The Polar Environment Atmospheric Research Laboratory (PEARL) is located on Ellesmere Island (image credit: left, wikimedia commons, right, Tobias Kerzenmacher).

However, the optimal conditions can be interrupted by brief but potentially intense storms. In the article the team added that, “the primary issue is wind rather than the cold temperatures.” The PEARL facility is equipped with an important weather probe that conveys on-site conditions at 10 minute intervals, thanks to the Canadian Network for the Detection of Atmospheric Change (CANDAC).

There are numerous challenges that arise when observing from the Arctic, but scientists like Steinbring have worked to overcome them, potentially enabling new studies of gravitational lenses and other pertinent phenomena. Indeed, astronomical observations are likewise being obtained from Antarctica. For example, there is the Antarctic Search for Transiting Exoplanets (ASTEP) 40 cm telescope at Dome C, and three 50 cm Antarctic Survey Telescopes (AST3) at Dome A, Antarctica. Steinbring remarked that floorspace is potentially available for up to 5 more telescopes at PEARL, if the compact design they studied was adopted.

E. Steinbring and his colleagues B. Leckie and R. Murowinski are associated with the National Research Council Canada, Herzberg Astronomy and Astrophysics in Victoria, Canada. An electronic preprint of their article is available on arXiv, and the findings were presented recently at the Adapting to the Atmosphere Conference in Durham, UK.

 

New Simulation Offers Stunning Images of Black Hole Merger

A black hole is an extraordinarily massive, improbably dense knot of spacetime that makes a living swallowing or slinging away any morsel of energy that strays too close to its dark, twisted core. Anyone fortunate (or unfortunate) enough to directly observe one of these beasts in the wild would immediately notice the way its colossal gravitational field warps all of the light from the stars and galaxies behind it, a phenomenon known as gravitational lensing.

Thanks to the power of supercomputers, a curious observer no longer has to venture into outer space to see such a sight. A team of astronomers has released their first simulated images of the lensing effects of not just one, but two black holes, trapped in orbit by each other’s gravity and ultimately doomed to merge as one.

Astronomers have been able to model the gravitational effects of a single black hole since the 1970s, but the imposing mathematics of general relativity made doing so for a double black-hole system a much larger challenge. Over the last ten years, however, scientists have improved the accuracy of computer models that deal with these types of calculations in an effort to match observations from gravitational wave detectors like LIGO and VIRGO.

The research collaboration Simulating Extreme Spacetimes (SXS) has begun using these models to mimic the lensing effects of high-gravity systems involving objects such as neutron stars and black holes. In their most recent paper, the team imagines a camera pointing at a binary black hole system against a backdrop of the stars and dust of the Milky Way. One way to figure out what the camera would see in this situation would be to use general relativity to compute the path of each photon traveling from every light source at all points within the frame. This method, however, involves a nearly impossible number of calculations.  So instead, the researchers worked backwards, mapping only those photons that would reach the camera and result in a bright spot on the final image – that is, photons that would not be swallowed by either of the black holes.

A binary black hole system, viewed from above. Image Credit: Bohn et al. (see http://arxiv.org/abs/1410.7775)
The same binary black hole system, viewed from above. Image Credit: Bohn et al. (see http://arxiv.org/abs/1410.7775)

As you can see in the image above, the team’s simulations testify to the enormous effect that these black holes have on the fabric of spacetime. Ambient photons curl into a ring around the converging binaries in a process known as frame dragging. Background objects appear to multiply on opposite sides of the merger (for instance, the yellow and blue pair of stars in the “northeast” and the “southwest” areas of the ring). Light from behind  the camera is even pulled into the frame by the black holes’ mammoth combined gravitational field. And each black hole distorts the appearance of the other, pinching off curved, comma-shaped regions of shadow called “eyebrows.” If you could zoom in with unlimited precision, you would find that there are, in fact, an infinite number of these eyebrows, each smaller than the last, like a cosmic set of Russian dolls.

In case you thought things couldn’t get any more amazing, SXS has also created two videos of the black hole merger: one simulated from above, and the other edge-on.
 



 



The SXS collaboration will continue to investigate gravitationally ponderous objects like black holes and neutron stars in an effort to better understand their astronomical and physical properties. Their work will also assist observational scientists as they search the skies for evidence of gravitational waves.

Check out the team’s ArXiv paper describing this work and their website for even more fascinating images.

A Cosmic Collision: Our Best View Yet of Two Distant Galaxies Merging

An international team of astronomers has obtained the best view yet of two galaxies colliding when the universe was only half its current age.

The team relied heavily on space- and ground-based telescopes, including the Hubble Space Telescope, the Atacama Large Millimeter/submillimeter Array (ALMA), the Keck Observatory, and the Karl Jansky Very Large Array (VLA). But the greatest asset was a chance cosmic alignment.

“While astronomers are often limited by the power of their telescopes, in some cases our ability to see detail is hugely boosted by natural lenses created by the universe,” said lead author Hugo Messias of the Universidad de Concepción in Chile and the Centro de Astronomia e Astrofísica da Universidade de Lisboa in Portugal.

Such a rare cosmic alignment plays visual tricks, where the intervening lens (be it a galaxy or a galaxy cluster) appears to bend and even magnify the distant light. This effect, called gravitational lensing, allows astronomers to study objects which would not be visible otherwise and to directly compare local galaxies with much more remote galaxies, seen when the universe was significantly younger.

The distant object in question, dubbed H-ATLAS J142935.3-002836, was originally spotted in the Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS). Although very faint in visible light pictures, it is among the brightest gravitationally lensed objects in the far-infrared regime found so far.

The Hubble and Keck images reveal that the foreground galaxy is a spiral galaxy, seen edge-on. Although the galaxy’s large dust clouds obscure part of the background light, both ALMA and VLA can observe the sky at longer wavelengths, which are unaffected by dust.

Using the combined data, the team discovered that the background system was actually an ongoing collision between two galaxies.

The Antennae galaxies. Credit: Hubble / ESA
The Antennae galaxies. Credit: Hubble / ESA

First, the team noticed that these two galaxies resembled a much closer system: the Antennae galaxies, two galaxies that have spent the past few hundred million years in a whirling embrace as they merge together. The similarity suggested a collision, but ALMA — with its high sensitivity and spatial resolution — was able to verify it.

ALMA has the unique ability to detect the emission from carbon monoxide, as opposed to other telescopes, which might only be able to probe the absorption along the line of sight. This allowed astronomers to measure the velocity of the gas in the more distant object. With this information, they were able to show that the lensed galaxy is indeed an ongoing galactic collision.

Such collisions naturally enhance star formation. Any gas within the galaxies will feel a headwind, much as a runner feels a wind even on the stillest day, and become compressed enough to spark star formation. Sure enough, ALMA shows that the two galaxies are forming hundreds of new stars each year.

“ALMA enabled us to solve this conundrum because it gives us information about the velocity of the gas in the galaxies, which makes it possible to disentangle the various components, revealing the classic signature of a galaxy merger,” said ESO’s Director of Science and coauthor of the new study, Rob Ivison. “This beautiful study catches a galaxy merger red handed as it triggers an extreme starburst.”

The findings have been published in the Aug. 26 issue of Astronomy & Astrophysics and is available online.

Merging Giant Galaxies Sport ‘Blue Bling’ in New Hubble Pic

On a summer night, high above our heads, where the Northern Crown and Herdsman meet, a titanic new galaxy is being born 4.5 billion light years away. You and I can’t see it, but astronomers using the Hubble Space Telescope released photographs today showing the merger of two enormous elliptical galaxies into a future  heavyweight adorned with a dazzling string of super-sized star clusters. 

The two giants, each about 330,000 light years across or more than three times the size of the Milky Way, are members of a large cluster of galaxies called SDSS J1531+3414. They’ve strayed into each other’s paths and are now helpless against the attractive force of gravity which pulls them ever closer.

A few examples of merging galaxies. NASA, ESA, the Hubble Heritage Team (STScI/AURA)-ESA/Hubble Collaboration and A. Evans (University of Virginia, Charlottesville/NRAO/Stony Brook University), K. Noll (STScI), and J. Westphal (Caltech)
A few examples of merging galaxies. NASA, ESA, the Hubble Heritage Team (STScI/AURA)-ESA/Hubble Collaboration and A. Evans (University of Virginia, Charlottesville/NRAO/Stony Brook University), K. Noll (STScI), and J. Westphal (Caltech)

Galactic mergers are violent events that strip gas, dust and stars away from the galaxies involved and can alter their appearances dramatically, forming large gaseous tails, glowing rings, and warped galactic disks. Stars on the other hand, like so many pinpoints in relatively empty space, pass by one another and rarely collide.

Elliptical galaxies get their name from their oval and spheroidal shapes. They lack the spiral arms, rich reserves of dust and gas and pizza-like flatness that give spiral galaxies like Andromeda and the Milky Way their multi-faceted character. Ellipticals, although incredibly rich in stars and globular clusters, generally appear featureless.

The differences between elliptical and spiral galaxies is easy to see. M87 at left and M74, both photographed with the Hubble Space Telescope. Credit: NASA/ESA
The differences between elliptical and spiral galaxies is easy to see. M87 at left and M74, both photographed with the Hubble Space Telescope. What look like stars around M87 are really globular star clusters. Credit: NASA/ESA

But these two monster ellipticals appear to be different. Unlike their gas-starved brothers and sisters, they’re rich enough in the stuff needed to induce star formation. Take a look at that string of blue blobs stretching across the center – astronomers call it a great example of ‘beads on a string’ star formation. The knotted rope of gaseous filaments with bright patches of new star clusters stems from the same physics which causes rain or water from a faucet to fall in droplets instead of streams. In the case of water, surface tension makes water ‘snap’ into individual droplets; with clouds of galactic gas, gravity is the great congealer.

Close up of the two elliptical galaxies undergoing a merger. The blue blobs are giant star clusters forming from gas colliding and collapsing into stars during the merger. Click for the scientific paper on the topic. Credit: NASA/ESA/Grant Tremblay
Close up of the two elliptical galaxies undergoing a merger. The blue blobs are giant star clusters forming from gas colliding and collapsing into stars during the merger. Click to read the scientific paper on the topic. Credit: NASA/ESA/Grant Tremblay

Nineteen compact clumps of young stars make up the length of this ‘string’, woven together with narrow filaments of hydrogen gas. The star formation spans 100,000 light years, about the size of our galaxy, the Milky Way. Astronomers still aren’t sure if the gas comes directly from the galaxies or has condensed like rain from X-ray-hot halos of gas surrounding both giants.

The blue arcs framing the merger have to do with the galaxy cluster’s enormous gravity, which warps the fabric of space like a lens, bending and focusing the light of more distant background galaxies into curvy strands of blue light. Each represents a highly distorted image of a real object.


Simulation of the Milky Way-Andromeda collision 4 billion years from now

Four billion years from now, Milky Way residents will experience a merger of our own when the Andromeda Galaxy, which has been heading our direction at 300,000 mph for millions of years, arrives on our doorstep. After a few do-si-dos the two galaxies will swallow one another up to form a much larger whirling dervish that some have already dubbed ‘Milkomeda’. Come that day, perhaps our combined galaxies will don a string a blue pearls too.

New Hubble View Shows Objects a Billion Times Fainter Than Your Eyes Can See

This 14-hour exposure from the Hubble Space Telescope zooms in on a galaxy cluster and shows objects around a billion times fainter than can be seen with the naked eye. Credit: NASA/ESA.

While this image isn’t as deep as the Hubble Deep Field, this 14-hour exposure by the Hubble Space Telescope shows objects around a billion times fainter than what can be seen with the human eyes alone. Astronomers say this image also offers a remarkable depth of field that lets us see more than halfway to the edge of the observable Universe.

As well, this image also provides an extraordinary cross-section of the Universe in both distance and age, showing objects at different distances and stages in cosmic history, and ranges from some of our nearest neighbors to objects seen in the early years of the Universe.

Annotated image of the field around CLASS B1608+656. Credit: NASA/ESA.
Annotated image of the field around CLASS B1608+656. Credit: NASA/ESA.

Most of the galaxies visible here are members of a huge cluster called CLASS B1608+656, which lies about five billion light-years away. But the field also contains other objects, both significantly closer and far more distant, including quasar QSO-160913+653228 which is so distant its light has taken nine billion years to reach us, two thirds of the time that has elapsed since the Big Bang.

Since the Hubble Deep Field combined 10 days of exposure and the eXtreme Deep Field, or XDF was assembled by combining ten years of observations (with over 2 million seconds of exposure time), this image at 14 hours of exposure may seem “small.” But it shows the power of the Hubble Space Telescope.

Also of note is that this image was “found” in the Hubble Hidden Treasures vault — where members of the public are able to search Hubble’s science for the best overlooked images that have never been seen by a general audience. This image of CLASS B1608+656 has been well-studied by scientists over the years, but this is the first time it has been published in full online.

Take a zooming view through the image in the video below and read more about this image here.

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Source: Hubble ESA