ESA /NASA Hubble: The third way of galaxies - lenticular

Credit: ESA/Hubble & NASA

The subject of this image is NGC 6861, a galaxy discovered in 1826 by the famed Scottish astronomer James Dunlop.

Almost two centuries later we now know that NGC 6861 is the second brightest member of a group of at least a dozen galaxies called the Telescopium Group, otherwise known as the NGC 6868 Group, in the small constellation of Telescopium (The Telescope).

The famed Scottish astronomer James Dunlop Credit: Wiki

This NASA/ESA Hubble Space Telescope view shows some important details of NGC 6861. One of the most prominent features is the disc of dark bands circling the centre of the galaxy.

These dust lanes are a result of large clouds of dust particles obscuring the light emitted by the stars behind them.

Dust lanes are very useful for working out whether we are seeing the galaxy disc edge-on, face-on or, as is the case for NGC 6861, somewhat in the middle. Dust lanes like these are typical of a spiral galaxy.

The dust lanes are embedded in a white oval shape, which is made up of huge numbers of stars orbiting the centre of the galaxy. This oval is, rather puzzlingly, typical of an elliptical galaxy.

So which is it, spiral or elliptical? The answer is neither! NGC 6861 does not belong to either the spiral or the elliptical family of galaxies.

It is a lenticular galaxy, a family which has features of both spirals and ellipticals.

The relationships between these three kinds of galaxies are not yet well understood. A lenticular galaxy could be a faded spiral that has run out of gas and lost its arms, or the result of two galaxies merging.

Being part of a group increases the chances for galactic mergers, so this could be the case for NGC 6861.

Milky Way and Andromeda galaxies set to collide - update 2014

The Andromeda spiral galaxy. 

Image courtesy NASA.

A short time ago, in a galaxy very, very close by, a NASA satellite thought it detected a gamma ray burst in Andromeda.

It was a false alarm, but astronomers used the opportunity as a reminder that our galaxy and Andromeda are set for a head-on collision.

NASA's Swift satellite discovers and measures gamma-ray bursts, the most powerful explosions in the universe, and their afterglow in X-ray, optical, and ultraviolet wavelengths of light.

The space agency says the spacecraft is designed "with powerful telescopes and quick reflexes to capture gamma-ray bursts as they flash and leave a lingering afterglow."

On Wednesday, astronomers and astrophiles alike buzzed with the news that Swift's equipment had captured a powerful flash of gamma rays, believed to be coming from the Andromeda Galaxy.

Those who watch the sky were caught up in the possibility that a clashing pair of neutron stars or a bright X-ray source was acting up a mere 2.5 million light-years away, NBC News reported.

But, alas, the excitement was short-lived. By the time more raw data came in and the initial information was re-analyzed, the project team realized what they thought was a giant burst of radiation was not the dense remnants of dead stars crashing together.

"We... do not believe this source to be in outburst. Instead, it was a serendipitous constant source in the field of view of a BAT subthreshold trigger," Swift team member Kim Page wrote in a NASA message.

The reason scientists (and the Twittersphere) were in such a tizzy was because, "The Andromeda galaxy, known in astronomical parlance as M31, holds a special place in our own future," the New York Times wrote.

NASA astronomers announced in 2012 "with certainty" that the next major cosmic event to hit the Milky Way will quite literally hit the Milky Way.

Our galaxy will have a "titanic collision" with neighbouring Andromeda. Not only that, the Triangulum galaxy, M33, is likely to join in on the action, causing a three-galaxy pile-up (and could even merge with the other two), scientists said in a statement.

The Milky Way and Andromeda are the dominant members of a small family of galaxies called the Local Group. Family ties bind the bevy together in the form of their mutual gravity.

NASA sought to assure the world that the sun and Earth are unlikely to be hit by stars or planets from Andromeda because of the vast emptiness of the two galaxies.

So Earth, they said, should easily survive what will be a 1.9 million kilometer per hour (1.2 million mile per hour) galactic merger. Even at that speed, the event would take about 2 billion years.

"It's like a bad car crash in galaxy-land," Roeland van der Marel, an astronomer with the Space Telescope Science Institute in Baltimore, which operates Hubble, told the media.

Scientists said in 2012 the collision would take place in 4 billion years. But the New York Times reported Wednesday, “Recent measurements with the Hubble Space Telescope have confirmed that they will hit head on in about two billion years.”

Chandra Sagittarius A*: Black holes at centre of galaxies are wormholes

Credit: X-ray: NASA /UMass /D.Wang et al., IR: NASA/STScI

Zilong Li and Cosimo Bambi with Fudan University in Shanghai have come up with a very novel idea, those black holes that are believed to exist at the center of a lot of galaxies, may instead by wormholes.

They've written a paper, uploaded to the preprint server arXiv, describing their idea and how what they've imagined could be proved right (or wrong) by a new instrument soon to be added to an observatory in Chile.

Sagittarius A*: NASA's Chandra Finds Milky Way's Black Hole may be Grazing on Asteroids

Back in 1974, space scientists discovered Sagittarius A* (SgrA ∗), a bright source of radio waves emanating from what appeared to be near the center of the Milky Way galaxy.

Subsequent study of the object led scientists to believe that it was (and is) a black hole, the behaviour of stars nearby, for example, suggested it was something massive and extremely dense.

What we're able to see when we look at SgrA ∗ are plasma gasses near the event horizon, not the object itself as light cannot escape.

That should be true for wormholes too, of course, which have also been theorized to exist by the Theory of General Relativity. Einstein even noted the possibility of their existence.

GRAVITY overview. The beam combiner instrument (bottom right) is located in the VLTI laboratory. 

The infrared wavefront-sensors (bottom left) are mounted to each of the four UTs. 

The laser metrology is launched from the beam-combiner and is detected at each UT/AT (top middle).

Unfortunately, no one has ever come close to proving the existence of wormholes, which are believed to be channels between different parts of the universe, or even between two universes in multi-universe theories.

In their paper, Li and Bambi suggest that there is compelling evidence suggesting that many of the objects we believe to be black holes at the center of galaxies, may in fact be wormholes.

Plasma gases orbiting a black hole versus a wormhole should look different to us, the pair suggest, because wormholes should be a lot smaller.

Plus, the presence of wormholes would help explain how it is that even new galaxies have what are now believed to be black holes, such large black holes would presumably take a long time to become so large, so how can they exist in a new galaxy?

They can't Li and Bambi conclude, instead those objects are actually wormholes, which theory suggests could spring up in an instant, and would have, following the Big Bang.

Making the two's speculation more exciting is the soon to be installed piece of equipment known as GRAVITY, it will be added to the European Space Observatory (ESO) in Chile, giving researchers there an unprecedented view of SgrA ∗ (and other black holes).

In just a couple of years, it should be possible to prove whether Li and Bambi's idea is correct or not, the photon capture sphere of the wormhole should be much smaller than that for a black hole, they note, if that's the case with SgrA ∗, space scientists will have to do some serious rethinking of wormholes and how they might fit in to current theories describing the universe.

More information: Distinguishing black holes and wormholes with orbiting hot spots, arXiv:1405.1883

ESA Hubble image: Hickson Compact groups of Galaxies in constellation of Eridanus

This new ESA Hubble image shows a handful of galaxies in the constellation of Eridanus (The River). 

NGC 1190, shown here on the right of the frame, stands apart from the rest; it belongs to an exclusive club known as Hickson Compact Group 22 (HCG 22).

There are four other members of this group, all of which lie out of frame: NGC 1189, NGC 1191, NGC 1192, and NGC 1199.

The other galaxies shown here are nearby galaxies 2MASS J03032308-1539079 (center), and dCAZ94 HCG 22-21 (left), both of which are not part of HCG 22.

Hickson Compact Groups are incredibly tightly bound groups of galaxies. Their discoverer Paul Hickson observed only 100 of these objects, which he described in his HCG catalog in the 1980s.

To earn the Hickson Compact Group label, there must be at least four members—each one fairly bright and compact.

These short-lived groups are thought to end their lives as giant elliptical galaxies, but despite knowing much about their form and destiny, the role of compact galaxy groups in galactic formation and evolution is still unclear.

These groups are interesting partly for their self-destructive tendencies. The group members interact, circling and pulling at one another until they eventually merge together, signaling the death of the group, and the birth of a large galaxy.

CSIRO Astronomers spy on galaxies in the raw

Antennas of CSIRO's Compact Array telescope. Photo: David Smyth

A CSIRO radio telescope has detected the raw material for making the first stars in galaxies that formed when the Universe was just three billion years old—less than a quarter of its current age.

This opens the way to studying how these early galaxies make their first stars.

The telescope is CSIRO's Australia Telescope Compact Array telescope near Narrabri, NSW.

"It one of very few telescopes in the world that can do such difficult work, because it is both extremely sensitive and can receive radio waves of the right wavelengths," says CSIRO astronomer Professor Ron Ekers.

The raw material for making stars is cold molecular hydrogen gas, H2. It can't be detected directly but its presence is revealed by a 'tracer' gas, carbon monoxide (CO), which emits radio waves.

In one project, astronomer Dr Bjorn Emonts (CSIRO Astronomy and Space Science) and his colleagues used the Compact Array to study a massive, distant conglomerate of star-forming 'clumps' or 'proto-galaxies' that are in the process of coming together as a single massive galaxy.

This structure, called the Spiderweb, lies more than ten thousand million light-years away [at a redshift of 2.16].

Dr Emonts' team found that the Spiderweb contains at least sixty thousand million [6 x 1010] times the mass of the Sun in molecular hydrogen gas, spread over a distance of almost a quarter of a million light-years.

This must be the fuel for the star-formation that has been seen across the Spiderweb. "Indeed, it is enough to keep stars forming for at least another 40 million years," says Emonts.

In a second set of studies, Dr Manuel Aravena (European Southern Observatory) and colleagues measured CO, and therefore H2, in two very distant galaxies [at a redshift of 2.7].

The faint radio waves from these galaxies were amplified by the gravitational fields of other galaxies—ones that lie between us and the distant galaxies. This process, called gravitational lensing, "acts like a magnifying lens and allows us to see even more distant objects than the Spiderweb," says Dr Aravena.

More information: Emonts BHC and 15 co-authors. CO(1-0) detection of molecular gas in the massive Spiderweb Galaxy (z=2). Monthly Notices of the Royal Astronomical Society 430, 3465 (2013). Online at arxiv.org/abs/1301.6012

Aravena M and 28 co-authors. Large gas reservoirs and free-free emission in two lensed star-forming galaxies at z = 2.7. Accepted for publication in Monthly Notices of the Royal Astronomical Society. Online at arxiv.org/abs/1305.0614

Hubble captures the result of a galactic collision

Spiral galaxy in the process of colliding with a lenticular galaxy. 

Credit: ESA/Hubble & NASA, Acknowledgement: Luca Limatola

A new image from the NASA/ESA Hubble Space Telescope captures an ongoing cosmic collision between two galaxies -- a spiral galaxy is in the process of colliding with a lenticular galaxy.

The collision looks almost as if it is popping out of the screen in 3-D, with parts of the spiral arms clearly embracing the lenticular galaxy's bulge.

The image also reveals further evidence of the collision. There is a bright stream of stars coming out from the merging galaxies, extending out towards the top of the image.

The bright spot in the middle of the plume, known as ESO 576-69, is what makes this image unique.

This spot is believed to be the nucleus of the former spiral galaxy, which was ejected from the system during the collision and is now being shredded by tidal forces to produce the visible stellar stream.

ESA ESO ALMA Image: ALMA pinpoints early galaxies at record speed

This video zooms in on some of the galaxies. The large red blobs are the earlier APEX observations and the much sharper views are from ALMA. 

Whereas the APEX images were not sharp enough to identify the emitting galaxies unambiguously the much sharper ALMA images can pin down the emitting galaxies much more precisely. 

The ALMA and APEX observations, at submillimetre wavelengths, are overlaid on an infrared view of the region as seen by the IRAC camera on the Spitzer Space Telescope (coloured blue). 

Credit: ALMA (ESO/NAOJ/NRAO), APEX (MPIfR/ESO/OSO), J. Hodge et al., A. Weiss et al., NASA Spitzer Science Center.

A team of astronomers has used ALMA (the Atacama Large Millimeter/submillimeter Array) to pinpoint the locations of over 100 of the most fertile star-forming galaxies in the early Universe. 

This image shows close-ups of a selection of these galaxies. 

The ALMA observations, at submillimetre wavelengths, are shown in orange/red and are overlaid on an infrared view of the region as seen by the IRAC camera on the Spitzer Space Telescope. 

The best map so far of these distant dusty galaxies was made using the Atacama Pathfinder Experiment (APEX), but the observations were not sharp enough to unambiguously identify these galaxies in images at other wavelengths. 

ALMA needed just two minutes per galaxy to pinpoint each one within a comparatively tiny region 200 times smaller than the broad APEX blobs, and with three times the sensitivity. 

Credit: ALMA (ESO/NAOJ/NRAO), APEX (MPIfR/ESO/OSO), J. Hodge et al., A. Weiss et al., NASA Spitzer Science Center 

A team of astronomers has used the new ALMA (Atacama Large Millimeter/submillimeter Array) telescope to pinpoint the locations of over 100 of the most fertile star-forming galaxies in the early Universe.

ALMA is so powerful that, in just a few hours, it captured as many observations of these galaxies as have been made by all similar telescopes worldwide over a span of more than a decade.

The most fertile bursts of star birth in the early Universe took place in distant galaxies containing lots of cosmic dust.

These galaxies are of key importance to our understanding of galaxy formation and evolution over the history of the Universe, but the dust obscures them and makes them difficult to identify with visible-light telescopes.

To pick them out, astronomers must use telescopes that observe light at longer wavelengths, around one millimetre, such as ALMA.

Jacqueline Hodge

"Astronomers have waited for data like this for over a decade. ALMA is so powerful that it has revolutionised the way that we can observe these galaxies, even though the telescope was not fully completed at the time of the observations," said Jacqueline Hodge (Max-Planck-Institut fur Astronomie, Germany), lead author of the paper presenting the ALMA observations.

The best map so far of these distant dusty galaxies was made using the ESO-operated Atacama Pathfinder Experiment telescope (APEX).

It surveyed a patch of the sky about the size of the full Moon, and detected 126 such galaxies but, in the APEX images, each burst of star formation appeared as a relatively fuzzy blob, which may be so broad that it covered more than one galaxy in sharper images made at other wavelengths.

Without knowing exactly which of the galaxies are forming the stars, astronomers were hampered in their study of star formation in the early Universe.

When Galaxies Collide: The Starry Night Tango - Video

This simulation, which represents a few billion years of evolution, shows two disk galaxies interacting in a graceful gravitational dance. The color represents the temperature of the gas in the galaxies.

The simulation shows how gravity can rearrange the gas and stars in galaxies during these interaction events, fueling the supermassive black holes at the centers of each galaxy.

Radiation from the energized black holes can heat up the gas and blow it away, causing the outbursts seen in the animation.

NASA's Wide-field Infrared Survey Explorer (WISE) is discovering some of the most active, powerful galaxies known, which in some cases may have been fueled by such mergers.

Video courtesy Volker Springel, Heidelberg University, Germany

NASA ESA Hubble: Extreme Deep Field images in the farthest reaches of the universe

NASA scientists have directed the Hubble Space Telescope to inspect a tiny patch of sky with an unusually long exposure time to obtain the deepest image of the sky ever obtained. 

The image, dubbed the "Hubble Extreme Deep Field (XDF)", reveals the faintest and most distant galaxies ever detected, shedding more light on the early history of the universe.

Credit: NASA/ESA Hubble

Nine years ago, NASA decided to point Hubble at a seemingly empty, randomly chosen spot in the sky – no larger than a needle's eye at arm's length – and have it gather data over one millions seconds in total exposure.

The result was the iconic image dubbed the "Hubble Ultra-Deep Field" (HUDF)" which, even in a space that small, revealed in excess of ten thousand galaxies.



Now, NASA has done it again, taking the experiment to new levels. With XDF, NASA took a patch of sky within the original Hubble Ultra Deep Field and doubled the exposure time to a total of two million seconds, or an impressive 23 days.

Despite a much narrower field of view, the new picture shows 5500 galaxies in even greater detail, including the earliest we have ever observed.

Centaurus A: Facing a mid-life crisis!

Centaurus A was facing a midlife crisis.

The giant elliptical galaxy's brightest stars were old and puffy, and it had nearly run out of gas needed to create new ones.

The galaxy was just a featureless blob that had lost its sparkle.

Then a chance encounter allowed boring old Centaurus A to have a fling with a younger, smaller galaxy.

The event revived the elder partner, triggering a fresh round of star birth and creating one of its most notable features: a dark dust lane along its middle.

In a surprise twist, new observations show the cosmic hanky-panky also caused Centaurus A to sprout two spiral arms – something no other elliptical galaxy is known to have.

The discovery offers new insights into how galaxies form and evolve, and hints at a new way for spiral structure to emerge.

Shocking revelation
The bisecting dust lane led astronomers in the early 19th century to think that Centaurus A might be two separate objects lying side by side. More recent studies have shown that the dust is most likely a disc left behind by a galactic merger.

By blocking visible light, the dust also conceals the intimacies of the galaxy's steamy affair. To gather more clues, Daniel Espada of the National Astronomical Observatory of Japan and colleagues looked at Centaurus A in radio wavelengths.

These longer waves emerge from carbon monoxide gas at the galaxy's centre and can pierce the dusty veil, allowing the team to trace otherwise hidden structures. What they saw was shocking.

"We were quite surprised to find what clearly looked like spiral arms," says team member Alison Peck of the Joint ALMA Observatory in Santiago, Chile.

Their images show the tentacles of gas curving around the galaxy's middle, with widths and orientations similar to those of the arms of spiral galaxies like our Milky Way.

What's more, the gas tentacles are "moving in a way that you would expect spiral arms to move", says Peck.

Astronomers Capture Fireworks in the Early Universe

Galaxies in the early universe grew fast by rapidly making new stars. 

Such prodigious star formation episodes, characterized by the intense radiation of the newborn stars, were often accompanied by fireworks in the form of energy bursts caused by the massive central black hole accretion in these galaxies. 

This discovery by a group of astronomers led by Peter Barthel of the Kapteyn Institute of the University of Groningen in the Netherlands was published in The Astrophysical Journal Letters.

Our Milky Way galaxy forms stars at a slow, steady pace: on average one new star a year is born. Since the Milky Way contains about a hundred billion stars, the actual changes are very slight.

The Milky Way is an extremely quiet galaxy; its central black hole is inactive, with only weak energy outbursts due to the occasional capture of a passing star or gas cloud.

This is in marked contrast to the 'active' galaxies of which there are various types and which were abundant in the early universe.

Quasars and radio galaxies are prime examples: owing to their bright, exotic radiation, these objects can be observed as far as the edge of the observable universe.

The light of the normal stars in their galaxies is extremely faint at such distances, but active galaxies can be easily detected through their luminous radio, ultraviolet or X-ray radiation, which results from steady accretion onto their massive central black holes.

Until recently these distant active galaxies were only interesting in their own right as peculiar exotic objects.

Little was known about the composition of their galaxies, or their relationship to the normal galaxy population.

However, in 2009 ESA's Herschel space telescope was launched. Herschel is considerably larger than NASA's Hubble, and operates at far-infrared wavelengths.

This enables Herschel to detect heat radiation generated by the processes involved in the formation of stars and planets at a small scale, and of complete galaxies at a large scale.

Peter Barthel has been involved with Herschel since 1997 and heads an observational program targeting distant quasars and radio galaxies.

His team used the Herschel cameras to observe seventy of these objects. Initial inspection of the observations has revealed that many emit bright far-infrared radiation.


The Astrophysical Journal Letter 'Extreme host galaxy growth in powerful early-epoch radio galaxies', by Peter Barthel and co-authors, describes their project and the detailed analysis of the first three distant radio galaxies.

The fact that these three objects, as well as many others from the observational sample, emit strong far-infrared radiation indicates that vigorous star formation is taking place in their galaxies, creating hundreds of stars per year during one or more episodes lasting millions of years.

The bright radio emission implies strong, simultaneous black hole accretion. This means that while the black holes in the centers of the galaxies are growing (as a consequence of the accretion), the host galaxies are also growing rapidly.

The Herschel observations thereby provide an explanation for the observation that more massive galaxies have more massive black holes.

Astronomers have observed this scaling relationship since the 1990s: the fireworks in the early universe could well be responsible for this relationship.

Says Barthel, "It is becoming clear that active galaxies are not only among the largest, most distant, most powerful and most spectacular objects in the universe, but also among the most important objects; many if not all massive normal galaxies must also have gone through similar phases of simultaneous black hole-driven activity and star formation."

Reference: The Astrophysical Journal Letters, Volume 757, Number 2 "Extreme Host Galaxy Growth in Powerful Early-epoch Radio Galaxies" Peter Barthel, Martin Haas, Christian Leipski, and Belinda Wilkes dx.doi.org/10.1088/2041-8205/757/2/L26

The Milky Way is surrounded by a massive halo of hot gas

An international team of astronomers has combined data from NASA's Chandra X-ray observatory, ESA's XMM-Newton space observatory and Japan's Suzaku satellite to suggest that our galaxy may be surrounded by a halo of hot gas extending in all directions for hundreds of thousands of light-years. 

The finding also offers clues as to why more than half of the ordinary matter in early galaxies has seemingly disappeared without leaving a trace.

Protons and neutrons are classified as "baryons," a type of subatomic particle that interacts strongly to form the nuclei of atoms. Taken together, baryons make up nearly all of the ordinary matter in our universe.

But if you were to tally the number of atoms in the universe, you'd find that something doesn't quite add up.

Astronomers have observed that entire galaxies seem to lose over half of their atoms compared to when they first formed.

All of this matter couldn't have simply disintegrated, so where has it gone? This decade-old question is known as the problem of the "missing baryons."

Now, a team of astronomers led by Dr. Anjali Gupta may have just found the answer, at least for our galaxy.

The baryons, says Gupta, haven't disappeared from the Milky Way. Rather, a mass of up to sixty billion suns – well in excess of the matter contained in the entire galactic disk – is spread out over a halo of hot gas stretching all around us for hundreds of thousands of light-years.

This gas is reaching temperatures in the millions of degrees, and with a density so low that, even if it were present in other galaxies, we would probably have no way of detecting it.

"With reasonable assumptions, our observations imply a huge reservoir of hot gas around the Milky Way," said co-author Smita Mathur of Ohio State University in Columbus.

"It may extend for a few hundred thousand light-years around the Milky Way or it may extend farther into the surrounding local group of galaxies. Either way, its mass appears to be very large."

A paper detailing the study was published on The Astrophysical Journal.

Stars Missing In Action Now Counted

Almost one in five exploding stars in nearby galaxies is simply not seen, astronomers have determined.

For galaxies further out, that fraction doubles. This finding clears the way for these stellar beacons to be used as a good measure of how fast galaxies made stars earlier in the universe's history.

Key evidence for this "body count" of missing supernovae has come from detailed studies of the galaxy Arp 299, made with the 8.2-m Gemini North telescope.

The work is reported in a paper, "Core-Collapse Supernovae Missed by Optical Surveys", published online in the Astrophysical Journal last month.

Massive stars live fast and die young, going out in a blaze of glory as "core-collapse supernovae".

"Because they don't live long, only about 10 million years, the number of massive stars that we can see being born should be essentially identical to the number we see exploding," said the study's lead author, Dr. Seppo Mattila of the University of Turku in Finland.

"The trouble has been, lots of these supernovae just seemed to have gone missing," he said.

"We expected to see more."

Our own Milky Way Galaxy is a case in point.

Two to three supernovae should explode in our galaxy every century. But the last time anyone might - just might - have seen one directly was in 1680.

In 2008, however, NASA's Chandra X-ray Observatory and the Very Large Array radio telescope of the US National Radio Astronomy Observatory found a supernova remnant about 140 years old near the center of our galaxy.

"That's where the supernovae are mostly hiding - in the dusty central parts of galaxies," said Dr. Stuart Ryder of the Australian Astronomical Observatory, one of the new paper's authors.

"That's where most stars in a galaxy congregate, and where most of them die."

ESA Hubble Image: The Tarantula Nebula

European Space Agency: Judy Schmidt

Turning its eye to the Tarantula Nebula, the NASA/ESA Hubble Space Telescope has taken this close-up of the outskirts of the main cloud of the Nebula.

The bright wispy structures are the signature of an environment rich in ionized hydrogen gas, called H II by astronomers.

In reality these appear red, but the choice of filters and colours of this image, which includes exposures both in visible and infrared light, make the gas appear green.

These regions contain recently formed stars, which emit powerful ultraviolet radiation that ionizes the gas around them.

These clouds are ephemeral as eventually the stellar winds from the newborn stars and the ionization process will blow away the clouds, leaving stellar clusters like the Pleiades.

Located in the Large Magellanic Cloud, one of our neighboring galaxies, and situated at a distance of 170,000 light-years away from Earth, the Tarantula Nebula is the brightest known nebula in the Local Group of galaxies.

It is also the largest (around 650 light-years across) and most active star-forming region known in our group of galaxies, containing numerous clouds of dust and gas and two bright star clusters.

Another recent Hubble image shows a large part of the nebula immediately adjacent to this field of view.

The cluster at the Tarantula nebula’s center is relatively young and very bright. While it is outside the field of view of this image, the energy from it is responsible for most of the brightness of the Nebula, including the part we see here.

The nebula is in fact so luminous that if it were located within 1,000 light-years from Earth, it would cast shadows on our planet.

The Tarantula Nebula was host to the closest supernova ever detected since the invention of the telescope, supernova 1987A, which was visible to the naked eye.

When Galaxies Collide: Tinkerbell Triplet

Probably the cutest merger, the Tinkerbell Triplet is the result of three galaxies coming together to form a fey object.

The collision is located about 650 million light-years away and is seen here in both visible and infrared wavelengths.

Image: ESO

When Galaxies Collide: Interacting Strongly

The galaxies seen here — NGC 6621, on the right, and NGC 6622, to the left – are seen about 100 million years into their merger.

Gravitational forces have wrapped a long tail of stars around both galaxies as well as triggering an extensive burst of stellar formation.

The pair are located in the constellation Draco, approximately 300 million light-years from Earth.

Image: NASA, ESA, the Hubble Heritage Team (STScI/AURA)-ESA/Hubble Collaboration and W. Keel (University of Alabama, Tuscaloosa)

When Galaxies Collide: Mirror Image

Two galaxies appear as mirror reflections of one another as they enter the first stages of their collision.

The object is known as NGC 5331 and is located 450 million light-years from Earth in the constellation Virgo.

Image: NASA, ESA, the Hubble Heritage Team (STScI/AURA)-ESA/Hubble Collaboration and A. Evans (University of Virginia, Charlottesville/NRAO/Stony Brook University)

When Galaxies Collide: Middle Merger

The galaxies seen here are caught mid-merger.

The bodies of the two parent galaxies have more or less fused but two independent central nuclei can still be seen in the image.

The collision is thought to have begun approximately 300 million years ago.

This object, known as NGC 520, is one of the brightest galaxy pairs on the sky, and is located about 100 million light-years away toward the constellation Pisces.

Image: NASA, ESA, the Hubble Heritage Team (STScI/AURA)-ESA/Hubble Collaboration and B. Whitmore (STScI)

When Galaxies Collide: Linked Arms

The two galaxies seen here, NGC 6050 and IC 1179, are located about 450 million light-years away in the constellation Hercules.

The spiral bodies are seen crashing together, with an enormous eddy of stars seeming to form between their conjoined arms.

This object is part of the Hercules Galaxy Cluster, itself located within the Great Wall of superclusters, the largest known structure in the universe.

Image: NASA, ESA, the Hubble Heritage Team (STScI/AURA)-ESA/Hubble Collaboration and K. Noll (STScI)

When Galaxies Collide: Cosmic Owl

The odd object, known as ESO 148-2, looks like some weird water bug seen head-on.

Located about 600 million light-years from us, it is the result of two galaxies merging, with their cores located in the central “body” and a great deal of matter sweeping out into two curved “wings.”

Image: NASA, ESA, the Hubble Heritage Team (STScI/AURA)-ESA/Hubble Collaboration and A. Evans (University of Virginia, Charlottesville/NRAO/Stony Brook University)