Picture of The Week
A Galactic Portal
Mon, 14 Oct 2019 06:00:00 +0200

The galaxy NGC 4380 looks like a special effect straight out of a science fiction or fantasy film in this Hubble Picture of the Week, swirling  like a gaping portal to another dimension. 

In the grand scheme of things, though, the galaxy is actually quite ordinary. Spiral galaxies like NGC 4380 are one of the most common types of galaxy in the Universe. These colossal collections of stars, often numbering in the hundreds of billions, are shaped like a flat disc, sometimes with a rounded bulge in the centre. Graceful spiral arms outlined by dark lanes of dust wind around the bulging core, which glows brightly and has the highest concentration of stars in the galaxy.

A Spiral in Profile
Mon, 07 Oct 2019 06:00:00 +0200

The NASA/ESA Hubble Space Telescope sees galaxies of all shapes, sizes, brightnesses, and orientations in the cosmos. Sometimes, the telescope gazes at a galaxy oriented sideways — as shown here. The spiral galaxy featured in this Picture of the Week is called NGC 3717, and it is located about 60 million light-years away in the constellation of Hydra (The Sea Serpent)

Seeing a spiral almost in profile, as Hubble has here, can provide a vivid sense of its three-dimensional shape. Through most of their expanse, spiral galaxies are shaped like a thin pancake. At their cores, though, they have bright, spherical, star-filled bulges that extend above and below this disc, giving these galaxies a shape somewhat like that of a flying saucer when they are seen edgeon.

NGC 3717 is not captured perfectly edge-on in this image; the nearer part of the galaxy is tilted ever so slightly down, and the far side tilted up. This angle affords a view across the disc and the central bulge (of which only one side is visible). 

Snakes and Stones
Mon, 30 Sep 2019 06:00:00 +0200

The galaxy pictured in this Hubble Picture of the Week has an especially evocative name: the Medusa merger. 

Often referred to by its somewhat drier New General Catalogue designation of NGC 4194, this was not always one entity, but two. An early galaxy consumed a smaller gas-rich system, throwing out streams of stars and dust out into space. These streams, seen rising from the top of the merger galaxy, resembles the writhing snakes that Medusa, a monster in ancient Greek mythology, famously had on her head in place of hair, lending the object its intriguing name. 

The legend of Medusa also held that anyone who saw her face would transform into stone. In this case, you can feast your eyes without fear on the centre of the merging galaxies, a region known as Medusa's eye. All the cool gas pooling here has triggered a burst of star formation, causing it to stand out brightly against the dark cosmic backdrop.

The Medusa merger is located about 130 million light-years away in the constellation of Ursa Major (The Great Bear)

Beacon of Light
Mon, 23 Sep 2019 06:00:00 +0200

This image from the NASA/ESA Hubble Space Telescope shows the galaxy Messier 86. Despite its being discovered over 235 years ago by astronomer Charles Messier, the morphological classification of Messier 86 remains unclear; astronomers are still debating over whether it is either elliptical or lenticular (the latter being a cross between an elliptical and spiral galaxy).

Messier 86 is part of the Virgo Cluster of galaxies and is situated about 50 million light-years from Earth. The galaxy is moving through space remarkably quickly  — its current trajectory is bringing it in our direction, back towards the centre of its cluster from the far side, at the incredible speed of over 875 000 kilometres per hour! Because of the speed with which it is moving through the cluster, Messier 86 is undergoing a process known as ram-pressure stripping; the resistive material filling the gaps between individual cluster galaxies is pulling at the gas and dust in Messier 86 and stripping them out as the galaxy moves, creating a long trail of hot gas that is emitting X-ray radiation.

Astronomers are using Hubble observations such as this to study elliptical and lenticular galaxies, both of which are often found at the centres of galaxy clusters. By studying the cores of these galaxies, astronomers hope to determine details of the central structure and to analyse both the history of the galaxy and the formation of its core.

Not So Dead After All
Mon, 16 Sep 2019 06:00:00 +0200

Many of the best-loved galaxies in the cosmos are remarkably large, close, massive, bright, or beautiful, often with an unusual or intriguing structure or history. However, it takes all kinds to make a Universe — as demonstrated by this Hubble Picture of the Week of Messier 110.

Messier 110 may not look like much, but it is a fascinating near neighbour of our home galaxy, and an unusual example of its type. It is a member of the Local Group, a gathering of galaxies comprising the Milky Way and a number of the galaxies closest to it. Specifically, Messier 110 is one of the many satellite galaxies encircling the Andromeda Galaxy, the nearest major galaxy to our own, and is classified as a dwarf elliptical galaxy, meaning that it has a smooth and almost featureless structure. Elliptical galaxies lack arms and notable pockets of star formation — both characteristic features of spiral galaxies. Dwarf ellipticals are quite common in groups and clusters of galaxies, and are often satellites of larger galaxies.

Because they lack stellar nurseries and contain mostly old stars, elliptical galaxies are often considered ‘dead’ when compared to their spiral relatives. However, astronomers have spotted signs of a population of young, blue stars at the centre of Messier 110 — hinting that it may not be so dead after all.

Dark Matter in the Belly of the Whale
Mon, 09 Sep 2019 06:00:00 +0200

This image, taken with the NASA/ESA Hubble Space Telescope, focuses on an object named UGC 695, which is located 30 million light-years away within the constellation Cetus (The Sea Monster), also known as The Whale.

UGC 695 is a low-surface-brightness (LSB) galaxy. These galaxies are so faint that their brightness is less than the background brightness of Earth’s atmosphere, which makes them tricky to observe. This low brightness is the result of the relatively small number of stars within them — most of the baryonic matter in these galaxies exists in the form of huge clouds of gas and dust. The stars are also distributed over a relatively large area.

LSB galaxies, like dwarf galaxies, have a high fraction of dark matter relative to the number of stars they contain. Astronomers still debate about how LSB galaxies formed in the first place.

Hubble’s Legacy
Mon, 02 Sep 2019 06:00:00 +0200

This Picture of the Week shows a dwarf galaxy named UGC 685. Such galaxies are small and contain just a tiny fraction of the number of stars in a galaxy like the Milky Way. Dwarf galaxies often show a hazy structure, an ill-defined shape, and an appearance somewhat akin to a swarm or cloud of stars — and UGC 685 is no exception to this. Classified as an SAm galaxy — a type of unbarred spiral galaxy — it is located about 15 million light-years from Earth.

These data were gathered under the NASA/ESA Hubble Space Telescope’s LEGUS (Legacy ExtraGalactic UV Survey) Program, the sharpest and most comprehensive ultraviolet survey of star-forming galaxies in the nearby Universe. 

LEGUS is imaging 50 spiral and dwarf galaxies in our cosmic neighbourhood in multiple colours using Hubble’s Wide Field Camera 3. The survey is picking apart the structures of these galaxies and resolving their constituent stars, clusters, groups, and other stellar associations. Star formation plays a huge role in shaping its host galaxy; by exploring these targets in detail via both new observations and archival Hubble data, LEGUS will shed light on how stars form and cluster together, how these clusters evolve, how a star’s formation affects its surroundings, and how stars explode at the end of their lives

A Passing Fancy
Mon, 26 Aug 2019 06:00:00 +0200

This Picture of the Week from the NASA/ESA Hubble Space Telescope shows NGC 5307, a planetary nebula which lies about 10000 light years from Earth. It can be seen in the constellation Centaurus (The Centaur), which can be seen primarily in the southern hemisphere.  A planetary nebula is the final stage of a Sun-like star. As such, planetary nebulae allow us a glimpse into the future of our own Solar System. A star like our Sun will, at the end of its life, transform into a red giant. Stars are sustained by the nuclear fusion that occurs in their core, which creates energy. The nuclear fusion processes constantly try to rip the star apart. Only the gravity of the star prevents this from happening. 

At the end of the red giant phase of a star, these forces become unbalanced. Without enough energy created by fusion, the core of the star collapses in on itself, while the surface layers are ejected outward. After that, all that remains of the star is what we see here: glowing outer layers surrounding a white dwarf star, the remnants of the red giant star’s core. 

This isn’t the end of this star’s evolution though — those outer layers are still moving and cooling. In just a few thousand years they will have dissipated, and all that will be left to see is the dimly glowing white dwarf.

The Death of a Star
Mon, 19 Aug 2019 06:00:00 +0200

This atmospheric Picture of the Week, taken with the NASA/ESA Hubble Space Telescope, shows a dark, gloomy scene in the constellation of Gemini (The Twins). The subject of this image confused astronomers when it was first studied — rather than being classified as a single object, it was instead recorded as two objects, owing to its symmetrical lobed structure (known as NGC 2371 and NGC 2372, though sometimes referred to together as NGC 2371/2). 

These two lobes are visible to the upper right and lower left of the frame, and together form something known as a planetary nebula. Despite the name, such nebulae have nothing to do with planets; NGC 2371/2 formed when a Sun-like star reached the end of its life and blasted off its outer layers, shedding the constituent material and pushing it out into space to leave just a superheated stellar remnant behind. This remnant is visible as the orange-tinted star at the centre of the frame, sitting neatly between the two lobes.

The structure of this region is complex. It is filled with dense knots of gas, fast-moving jets that appear to be changing direction over time, and expanding clouds of material streaming outwards on diametrically opposite sides of the remnant star. Patches of this scene glow brightly as the remnant star emits energetic radiation that excites the gas within these regions, causing it to light up. This scene will continue to change over the next few thousand years; eventually the knotty lobes will dissipate completely, and the remnant star will cool and dim to form a white dwarf

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The Inky Abyss
Mon, 12 Aug 2019 06:00:00 +0200

Although it looks more like an entity seen through a microscope than a telescope, this rounded object, named NGC 2022, is certainly no alga or tiny, blobby jellyfish. Instead, it is a vast orb of gas in space, cast off by an ageing star. The star is visible in the orb's centre, shining through the gases it formerly held onto for most of its stellar life. 

When stars like the Sun grow advanced in age, they expand and glow red. These so-called red giants then begin to lose their outer layers of material into space. More than half of such a star's mass can be shed in this manner, forming a shell of surrounding gas. At the same time, the star's core shrinks and grows hotter, emitting ultraviolet light that causes the expelled gases to glow. 

This type of object is called, somewhat confusingly, a planetary nebula, though it has nothing to do with planets. The name derives from the rounded, planet-like appearance of these objects in early telescopes.

NGC 2022 is located in the constellation of Orion (The Hunter).

Galactic Creatures at Play
Mon, 05 Aug 2019 06:00:00 +0200

The pair of strange, luminescent creatures at play in this image are actually galaxies — realms of millions upon millions of stars.

This galactic duo is known as UGC 2369. The galaxies are interacting, meaning that their mutual gravitational attraction is pulling them closer and closer together and distorting their shapes in the process. A tenuous bridge of gas, dust, and stars can be seen connecting the two galaxies,, during which they pulled material out into space across the diminishing divide between them. 

Interaction with others is a common event in the history of most galaxies. For larger galaxies like the Milky Way, the majority of these interactions involve significantly smaller so-called dwarf galaxies. But every few aeons, a more momentous event can occur. For our home galaxy, the next big event will take place in about four billion years, when it will collide with its bigger neighbour, the Andromeda Galaxy. Over time, the two galaxies will likely merge into one — already nicknamed Milkomeda.

Feeling Edgy
Mon, 29 Jul 2019 06:00:00 +0200

Believe it or not, this long, luminous streak, speckled with bright blisters and pockets of material, is a spiral galaxy like our Milky Way. But how could that be? 

It turns out that we see this galaxy, named NGC 3432, orientated directly edge-on to us from our vantage point here on Earth. The galaxy’s spiral arms and bright core are hidden, and we instead see the thin strip of its very outer reaches. Dark bands of cosmic dust, patches of varying brightness, and pink regions of star formation help with making out the true shape of NGC 3432 — but it’s still somewhat of a challenge! Because observatories such as the NASA/ESA Hubble Space Telescope have seen spiral galaxies at every kind of orientation, astronomers can tell when we happen to have caught one from the side. 

The galaxy is located in the constellation of Leo Minor (The Lesser Lion). Other telescopes that have had NGC 3432 in their sights include those of the Sloan Digital Sky Survey, the Galaxy Evolution Explorer (GALEX), and the Infrared Astronomical Satellite (IRAS).

Up and Over
Mon, 22 Jul 2019 06:00:00 +0200

Every now and then, the NASA/ESA Hubble Space Telescope glimpses a common object — say, a spiral galaxy — in an interesting or unusual way. A sharply angled perspective, such as the one shown in this Picture of the Week, can make it seem as if we, the viewers, are craning our necks to see over a barrier into the galaxy's bright centre. 

In the case of NGC 3169, this barrier is the thick dust embedded within the galaxy's spiral arms. Cosmic dust comprises a potpourri of particles, including water ice, hydrocarbons, silicates, and other solid material. It has many origins and sources, from the leftovers of star and planet formation to molecules modified over millions of years by interactions with starlight. 

NGC 3169 is located about 70 million light-years away in the constellation of Sextans (The Sextant). It is part of the Leo I Group of galaxies, which, like the Local Group that houses our home galaxy, the Milky Way, is part of a larger galactic congregation known as the Virgo Supercluster

A Beautiful Whorl
Mon, 15 Jul 2019 06:00:00 +0200

Galaxies come in many shapes and sizes. One of the key galaxy types we see in the Universe is the spiral galaxy, as demonstrated in an especially beautiful way by the subject of this Hubble Picture of the Week, NGC 2985. NGC 2985 lies roughly over 70 million light years from the Solar System in the constellation of Ursa Major (The Great Bear).

The intricate, near-perfect symmetry on display here reveals the incredible complexity of NGC 2985. Multiple tightly-wound spiral arms widen as they whorl outward from the galaxy’s bright core, slowly fading and dissipating until these majestic structures disappear into the emptiness of intergalactic space, bringing a beautiful end to their starry splendour. 

Over aeons, spiral galaxies tend to run into other galaxies, often resulting in mergers. These coalescing events scramble the winding structures of the original galaxies, smoothing and rounding their shape. These objects possess a beauty all their own, distinct from the spiral galaxies from whence they came.

Galactic Cherry Blossom
Mon, 08 Jul 2019 06:00:00 +0200

The galaxy NGC 1156 resembles a delicate cherry blossom tree flowering in springtime in this Hubble Picture of the Week. The many bright "blooms" within the galaxy are in fact stellar nurseries — regions where new stars are springing to life. Energetic light emitted by newborn stars in these regions streams outwards and encounters nearby pockets of hydrogen gas, causing it to glow with a characteristic pink hue.

NGC 1156 is located in the constellation of Aries (The Ram). It is classified as a dwarf irregular galaxy, meaning that it lacks a clear spiral or rounded shape, as other galaxies have, and is on the smaller side, albeit with a relatively large central region that is more densely packed with stars. 

Some pockets of gas within NGC 1156 rotate in the opposite direction to the rest of the galaxy, suggesting that there has been a close encounter with another galaxy in NGC 1156's past. The gravity of this other galaxy — and the turbulent chaos of such an interaction — could have scrambled the likely more orderly rotation of material within NGC 1156, producing the odd behaviour we see today.

In Bloom
Mon, 01 Jul 2019 06:00:00 +0200

This NASA/ESA Hubble Space Telescope Picture of the Week shows bright, colourful pockets of star formation blooming like roses in a spiral galaxy named NGC 972. 

The orange-pink glow is created as hydrogen gas reacts to the intense light streaming outwards from nearby newborn stars; these bright patches can be seen here amid dark, tangled streams of cosmic dust

Astronomers look for these telltale signs of star formation when they study galaxies throughout the cosmos, as star formation rates, locations, and histories offer critical clues as to how these colossal collections of gas and dust have evolved over time. New generations of stars contribute to — and are also, in turn, influenced by — the broader forces and factors that mould galaxies throughout the Universe, such as gravity, radiation, matter, and dark matter.

German-British astronomer William Herschel is credited with the discovery of NGC 972 in 1784. Astronomers have since measured its distance, finding it to be just under 70 million light-years.

Trillions of stars
Mon, 24 Jun 2019 06:00:00 +0200

This Hubble Picture of the Week shows the spiral galaxy Messier 98, which is located about 45 million light-years away in the constellation of Coma Berenices (Berenice's Hair). It was discovered in 1781 by the French astronomer Pierre Méchain, a colleague of Charles Messier, and is one of the faintest objects in Messier’s astronomical catalogue.

Messier 98 is estimated to contain about a trillion of stars, and is full of cosmic dust — visible here as a web of red-brown stretching across the frame — and hydrogen gas. This abundance of star-forming material means that Messier 98 is producing stellar newborns at a high rate; the galaxy shows the characteristic signs of stars springing to life throughout its bright centre and whirling arms.

This image of Messier 98 was taken in 1995 with the Wide Field and Planetary Camera 2, an instrument that was installed on the NASA/ESA Hubble Space Telescope from 1993 till 2009. These observations were taken in infrared and visible light as part of a study of galaxy cores within the Virgo Cluster, and feature a portion of the galaxy near the centre.

Spiral, elliptical, irregular
Mon, 17 Jun 2019 06:00:00 +0200

This image shows an irregular galaxy named IC 10, a member of the Local Group — a collectiongrouping of over 50 galaxies inwithin our cosmic neighbourhood that includes the Milky Way.

IC 10 is a remarkable object. It is the closest-known starburst galaxy to us, meaning that it is undergoing a furious bout of star formation fueled by ample supplies of cool hydrogen gas. This gas condenses into vast molecular clouds, which then form into dense knots where pressures and temperatures reach a point sufficient to ignite nuclear fusion, thus giving rise to new generations of stars.  

As an irregular galaxy, IC 10 lacks the majestic shape of spiral galaxies such as the Milky Way, or the rounded, ethereal appearance of elliptical galaxies. It is a faint object, despite its relative proximity to us — justof 2.2 million light-years. In fact, IC 10 only became known to humankind in 1887, when American astronomer Lewis Swift spotted it during an observing campaign. The small galaxy remains difficult to study even today, because it is located along a line-of-sight which is chock-full of cosmic dust and stars.

A version of this image was entered into the Hubble's Hidden Treasures image processing competition by contestant Nikolaus Sulzenauer, and went on to win tenth prize.

An explosive galaxy
Mon, 10 Jun 2019 06:00:00 +0200

When massive stars die at the end of their short lives, they light up the cosmos with bright, explosive bursts of light and material known as supernovae. A supernova event is incredibly energetic and intensely luminous — so much so that it forms what looks like an especially bright new star that slowly fades away over time.

These exploding stars glow so incredibly brightly when they first form that they can be spotted from afar using telescopes such as the NASA/ESA Hubble Space Telescope. The subject of this image, a spiral galaxy named NGC 4051 — about 45 million light-years from Earth — has hosted multiple supernovae in past years. The first was spotted in 1983 (SN 1983I), the second in 2003 (SN 2003ie), and the most recent in 2010 (SN 2010br). These explosive events were seen scattered throughout the centre and spiral arms of NGC 4051.

The SN 1983I and SN 2010br were both categorised as supernovae of type Ic. This type of supernova is produced by the core collapse of a massive star that has lost its outer layer of hydrogen and helium, either via winds or by mass transfer to a companion. Because of this, type Ic — and also type Ib — supernovae are sometimes referred to as stripped core-collapse supernovae.

NGC 4501 sits in the southern part of a cluster of galaxies known as the Ursa Major I Cluster; this cluster is especially rich in spirals such as NGC 4051, and is a subset of the larger Virgo Supercluster, which also houses the Milky Way.

Galactic maturity
Mon, 03 Jun 2019 06:00:00 +0200

This striking image was taken by the NASA/ESA Hubble Space Telescope’s Wide Field Camera 3, a powerful instrument installed on the telescope in 2009. WFC3 is responsible for many of Hubble’s most breathtaking and iconic photographs, including Pictures of the Week.

Shown here, NGC 7773 is a beautiful example of a barred spiral galaxy. A luminous bar-shaped structure cuts prominently through the galaxy's bright core, extending to the inner boundary of NGC 7773's sweeping, pinwheel-like spiral arms. Astronomers think that these bar structures emerge later in the lifetime of a galaxy, as star-forming material makes its way towards the galactic centre — younger spirals do not feature barred structures as often as older spirals do, suggesting that bars are a sign of galactic maturity. They are also thought to act as stellar nurseries, as they gleam brightly with copious numbers of youthful stars.

Our galaxy, the Milky Way, is thought to be a barred spiral like NGC 7773. By studying galactic specimens such as NGC 7773 throughout the Universe, researchers hope to learn more about the processes that have shaped — and continue to shape — our cosmic home.

Bucking the trend
Mon, 27 May 2019 06:00:00 +0200

This luminous orb is the galaxy NGC 4621, better known as Messier 59. As this latter moniker indicates, the galaxy was listed in the famous catalogue of deep-sky objects compiled by French comet-hunter Charles Messier in 1779. However, German astronomer Johann Gottfried Koehler is credited with discovering the galaxy just days before Messier added it to his collection.   

Modern observations show that Messier 59 is an elliptical galaxy, one of the three main kinds of galaxies along with spirals and irregulars. Ellipticals tend to be the most evolved of the trio, full of old, red stars and exhibiting little or no new star formation. Messier 59, however, bucks this trend somewhat; the galaxy does show signs of star formation, with some newborn stars residing within a disc near the core.

Located in the 2000-strong Virgo Cluster of galaxies within the constellation of Virgo (The Virgin), Messier 59 lies approximately 50 million light-years away from us. This image was taken by the NASA/ESA Hubble Space Telescope’s Advanced Camera for Surveys.

Come a little closer
Mon, 20 May 2019 06:00:00 +0200

This Picture of the Week stars Messier 90, a beautiful spiral galaxy located roughly 60 million light-years from the Milky Way in the constellation of Virgo (The Virgin). The galaxy is part of the Virgo Cluster, a gathering of galaxies that is over 1200 strong.

This image combines infrared, ultraviolet, and visible light gathered by the Wide Field and Planetary Camera 2 on the NASA/ESA Hubble Space Telescope. This camera was operational between 1994 and 2010, producing images with an unusual staircase-like shape as seen here. This is because the camera was made up of four light detectors with overlapping fields of view, one of which gave a higher magnification than the other three. When the four images are combined together in one picture, the high magnification image needs to be reduced in size in order for the image to align properly. This produces an image with a layout that looks like three steps.

Messier 90 is remarkable; it is one of the few galaxies seen to be travelling toward the Milky Way, not away from it. The galaxy’s light reveals this incoming motion in that it is blueshifted. In simple terms, the galaxy is compressing the wavelength of its light as it moves towards us, like a slinky being squashed when you push on one end. This increases the frequency of the light and shifts it towards the blue end of the spectrum. As our Universe is expanding, almost all of the galaxies we see in the Universe are moving away from us, and we therefore see their light as redshifted, but Messier 90 appears to be a rare exception.

Astronomers think that this blueshift is likely caused by the cluster’s colossal mass accelerating its members to high velocities on bizarre and peculiar orbits, sending them whirling around on odd paths that take them both towards and away from us over time. While the cluster itself is moving away from us, some of its constituent galaxies, such as Messier 90, are moving faster than the cluster as a whole, making it so that from Earth we see the galaxy heading towards us. However, some are also moving in the opposite direction within the cluster, and thus seem to be streaking away from us at very high velocity.

Settling into old age
Mon, 13 May 2019 06:00:00 +0200

NGC 3384, visible in this image, has many of the features characteristic of so-called elliptical galaxies. Such galaxies glow diffusely, are rounded in shape, display few visible features, and rarely show signs of recent star formation. Instead, they are dominated by old, ageing, and red-hued stars. This stands in contrast to the sprightliness of spiral galaxies such as our home galaxy, the Milky Way, which possess significant populations of young, blue stars in spiral arms swirling around a bright core.

However, NGC 3384 also displays a hint of disc-like structure towards its centre, in the form of a central ‘bar’ of stars cutting through its centre. Many spirals also boast such a bar, the Milky Way included; galactic bars are thought to funnel material through and around a galaxy’s core, helping to maintain and fuel the activities and processes occurring there.

NGC 3384 is located approximately 35 million light-years away in the constellation of Leo (The Lion). This image was taken using the NASA/ESA Hubble Space Telescope’s Advanced Camera for Surveys.

Distant and ancient
Mon, 06 May 2019 06:00:00 +0200

Dotted across the sky in the constellation of Pictor (The Painter’s Easel) is the galaxy cluster highlighted here by the NASA/ESA Hubble Space Telescope: SPT-CL J0615-5746, or SPT0615 for short. First discovered by the South Pole Telescope less than a decade ago, SPT0615 is exceptional among the myriad clusters so far catalogued in our map of the Universe — it is the highest-redshift cluster for which a full, strong lens model is published.

SPT0615 is a massive cluster of galaxies, one of the farthest observed to cause gravitational lensing. Gravitational lensing occurs when light from a background object is deflected around mass between the object and the observer. Among the identified background objects, there is SPT0615-JD, a galaxy that is thought to have emerged just 500 million years after the Big Bang. This puts it among the very earliest structures to form in the Universe. It is also the farthest galaxy ever imaged by means of gravitational lensing.

Just as ancient paintings can tell us about the period of history in which they were painted, so too can ancient galaxies tell us about the era of the Universe in which they existed. To learn about cosmological history, astronomers explore the most distant reaches of the Universe, probing ever further out into the cosmos. The light from distant objects travels to us from so far away that it takes an immensely long time to reach us, meaning that it carries information from the past — information about the time at which it was emitted.

By studying such distant objects, astronomers are continuing to fill the gaps in our picture of what the very early Universe looked like, and uncover more about how it evolved into its current state.

Iconic
Mon, 29 Apr 2019 06:00:00 +0200

Few of the Universe’s residents are as iconic as the spiral galaxy. These limelight-hogging celestial objects combine whirling, pinwheeling arms with scatterings of sparkling stars, glowing bursts of gas, and dark, weaving lanes of cosmic dust, creating truly awesome scenes — especially when viewed through a telescope such as the NASA/ESA Hubble Space Telescope. In fact, this image from Hubble frames a perfect spiral specimen: the stunning NGC 2903.

NGC 2903 is located about 30 million light-years away in the constellation of Leo (The Lion), and was studied as part of a Hubble survey of the central regions of roughly 145 nearby disc galaxies. This study aimed to help astronomers better understand the relationship between the black holes that lurk at the cores of galaxies like these, and the rugby-ball-shaped bulge of stars, gas, and dust at the galaxy’s centre — such as that seen in this image.


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