ESO LaSilla Observatory Captures A spectacular landscape of star formation

This mosaic of images from the Wide Field Imager on the MPG/ESO 2.2-metre telescope at ESO's La Silla Observatory in Chile shows two dramatic star formation regions in the southern Milky Way. 

The first of these, on the left, is dominated by the star cluster NGC 3603, located about 20 000 light-years away, in the Carina-Sagittarius spiral arm of the Milky Way galaxy. 

The second object, on the right, is a collection of glowing gas clouds known as NGC 3576 that lies only about half as far from Earth. 

Credit: ESO/G. Beccari

This image, captured by the Wide Field Imager at ESO's La Silla Observatory in Chile, shows two dramatic star formation regions in the Milky Way.

The first, on the left, is dominated by the star cluster NGC 3603, located 20 000 light-years away, in the Carina-Sagittarius spiral arm of the Milky Way.

The second, is a collection of glowing gas clouds known as NGC 3576 that lies about half as far from Earth.

NGC 3603 is a very bright star cluster and is famed for having the highest concentration of massive stars that have been discovered in our galaxy so far.

At the centre lies a Wolf–Rayet multiple star system, known as HD 97950. Wolf–Rayet stars are at an advanced stage of stellar evolution, and start off with around 20 times the mass of the Sun.

But, despite this large mass, Wolf–Rayet stars shed a considerable amount of their matter due to intense stellar winds, which blast the star's surface material off into space at several million kilometres per hour, a crash diet of cosmic proportions.

NGC 3603 is in an area of very active star formation. Stars are born in dark and dusty regions of space, largely hidden from view.

But as the very young stars gradually start to shine and clear away their surrounding cocoons of material they become visible and create glowing clouds in the surrounding material, known as HII regions.

HII regions shine because of the interaction of ultraviolet radiation given off by the brilliant hot young stars with the hydrogen gas clouds.

HII regions can measure several hundred light-years in diameter, and the one surrounding NGC 3603 has the distinction of being the most massive in our galaxy.

The cluster was first observed by John Herschel on 14 March 1834 during his three-year expedition to systematically survey the southern skies from near Cape Town.

He described it as a remarkable object and thought that it might be a globular star cluster. Future studies showed that it is not an old globular, but a young open cluster, one of the richest known.

This zoom sequence takes the viewer deep into the spectacular southern Milky Way in the constellation of Carina (The Keel). 

We see two regions where stars are forming, the very rich cluster NGC 3603 and its surroundings and the strange glowing gas clouds known as NGC 3576. 

The final detailed views come from images taken with the Wide Field Imager on the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile. 

Credit: ESO/G. Beccari/N. Risinger (skysurvey.org). Music: movetwo 

NGC 3576, on the right of the image, also lies in the Carina–Sagittarius spiral arm of the Milky Way, but it is located only about 9000 light-years from Earth, much closer than NGC 3603, but appearing next to it in the sky. NGC 3576 is notable for two huge curved objects resembling the curled horns of a ram.

These odd filaments are the result of stellar winds from the hot, young stars within the central regions of the nebula, which have blown the dust and gas outwards across a hundred light-years.

Two dark silhouetted areas known as Bok globules are also visible in this vast complex of nebulae. These black clouds near the top of the nebula also offer potential sites for the future formation of new stars.

NGC 3576 was also discovered by John Herschel in 1834, making it a particularly productive and visually rewarding year for the English astronomer.

Jansky Very Large Array (VLA): Solving a 30-year-old problem in massive star formation

This false-colour Very Large Array image of the ionized gas in the star forming region Sgr B2 Main was used to detect small but significant changes in brightness of several of the sources. 

The spots and filaments in this image are regions of ionized gas around massive stars. 

The changes in brightness detected support a model that could solve a 30-year-old question in high mass star formation. 

Credit: NRAO /Agnes Scott College

An international group of astrophysicists has found evidence strongly supporting a solution to a long-standing puzzle about the birth of some of the most massive stars in the universe.

Young massive stars, which have more than 10 times the mass of the Sun, shine brightly in the ultraviolet, heating the gas around them, and it has long been a mystery why the hot gas doesn't explode outwards.

Now, observations made by a team of researchers using the Jansky Very Large Array (VLA), a radio astronomy observatory in New Mexico, have confirmed predications that as the gas cloud collapses, it forms dense filamentary structures that absorb the star's ultraviolet radiation when it passes through them. As a result, the surrounding heated nebula flickers like a candle.

The findings were published recently in The Astrophysical Journal Letters.

"Massive stars dominate the lives of their host galaxies through their ionizing radiation and supernova explosions," said Mordecai-Mark Mac Low, a curator in the American Museum of Natural History's Department of Astrophysics and an author on the paper.

"All the elements heavier than iron were formed in the supernova explosions occurring at the ends of their lives, so without them, life on Earth would be very different."

Observations of the massive star forming region Sgr B2 were made with the Karl G. Jansky Very Large Array (VLA) in 1989 and 2012. 

The VLA has been operational since 1980 and received a major upgrade that was completed in 2011. 

Credit: NRAO/AUI

Stars form when huge clouds of gas collapse. Once the density and temperature are high enough, hydrogen fuses into helium, and the star starts shining.

The most massive stars, though, begin to shine while the clouds are still collapsing.

Their ultraviolet light ionizes the surrounding gas, forming a nebula with a temperature of 10,000 degrees Celsius. Simple models suggest that at this stage, the gas around massive stars will quickly expand.

But observations from the VLA radio observatory show something different: a large number of regions of ionized hydrogen (so-called HII regions) that are very small.

"In the old theoretical model, a high-mass star forms and the HII region lights up and begins to expand."

Chris De Pree

"Everything was neat and tidy," said lead author Chris De Pree, a professor of astronomy and director of the Bradley Observatory at Agnes Scott College.

"But the group of theorists I am working with were running numerical models that showed accretion was continuing during star formation, and that material was continuing to fall in toward the star after the HII region had formed."

More information: arxiv.org/abs/1312.7768

ALMA and VLA Image: Star Formation Close to Milky Way's Supermassive Black Hole

A combined ALMA and ESO's  Very Large Array (VLA) image of the galactic center. 

The supermassive black hole is marked by its traditional symbol Sgr A*. 

The red and blue areas, taken with ALMA, map the presence of silicon monoxide, an indicator of star formation. 

The blue areas have the highest velocities, blasting out at 150-200 kilometers per second. 

The green region, imaged with the VLA, traces hot gas around the black hole and corresponds to an area 3.5 by 4.5 light-years. 

Credit: Yusef-Zadeh et al., ALMA (ESO, NAOJ, NRAO), NRAO/AUI/NSF.

Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have discovered signs of star formation perilously close to the supermassive black hole at the center of the Milky Way Galaxy.

If confirmed, this would be the first time that star formation was observed so close to the galactic center.

The center of our galaxy, 27,000 light-years away in the direction of the constellation Sagittarius, is home to a monstrous black hole with a mass of four million suns.

Extending outward from this gravitational behemoth for many light-years is a turbulent region of space that is thought to be wracked by such extreme tidal forces that any star-forming clouds of dust and gas would be stretched thin and shredded long before infant stars could emerge.

Yet against these extreme odds, ALMA spotted telltale jets of material bursting out of what appear to be dense cocoons of gas and dust.

These jets, if they were observed in more placid surroundings, would indicate the formation of a young star. The results were accepted for publication in the Astrophysical Journal Letters.

Farhad Yusef-Zadeh

"People think it is very hard to form stars near a supermassive black hole," said Farhad Yusef-Zadeh of Northwestern University.

"This is because the gravity of the black hole produces extreme tidal forces that would stretch and elongate molecular clouds, preventing them from ever accumulating enough mass to trigger star formation. But what we seem to have found are patches of dust and gas that have become so dense that they are able to overcome their inhospitable surroundings."

Yusef-Zadeh and his colleagues speculate that these molecular clouds have become so massive and dense, possibly by colliding together, that they cross the all-important threshold that allows internal gravity to take over, starting a chain of events that inexorably leads to the birth of a new star.

As this process evolves, material in these clouds clumps together and collapses into an ever denser mass that begins to rotate faster and faster.

This rapid rotation, possibly coupled with the star's magnetic field, accelerates some of the material and shoots it out into space along the nascent star's axis of rotation.

The astronomers were able to detect these characteristic jets of material by tracing the presence of the molecule silicon monoxide (SiO), which is relatively abundant in molecular clouds.

When excited during star formation, SiO emits a very specific set of wavelengths of light in the microwave, or millimeter range. This is precisely the window of light that ALMA was designed to study.

Silicon Monoxide (SiO)

"SiO is an excellent tracer of molecular outflows," said Yusef-Zadeh.

"What we see in these images from ALMA are outflows that appear very much like what we see in star-forming regions elsewhere in galaxy. So the environments may be very different, but once you get the right conditions, collapse takes place and you're able to create what we would observe to be run-of-the-mill massive or intermediate mass stars."

For more than a decade, astronomers have puzzled over the origin of stars seen whipping around the black hole that lurks at the center of our galaxy.

These massive, young stars (less than 10 million years old) are rocketing through an area of space where it was thought they had no business being.

Astronomers believe that they either formed elsewhere under more placid conditions and migrated inward or they somehow overcame their turbulent childhoods to emerge as relatively normal and well-adjusted stellar objects.

"Though this question of stars near the galactic center is still open ended, ALMA will definitely have the power and sensitivity to shed more light on the mystery," said Al Wootten, the North America ALMA Project Scientist with the National Radio Astronomy Observatory (NRAO) in Charlottesville, Virginia.

"These latest studies do suggest that the conditions necessary for star formation could extend much closer to the galactic center than we previously believed."

Mystery of Star Formation in Gas Cloud at Heart of Milky Way

Astronomers have finally solved a longstanding cosmic mystery — why a super-dense gas cloud near our Milky Way galaxy's core isn't churning out many new stars.

The gas cloud, known as G0.253+0.016, is simply swirling too fast, researchers said.

It lacks the requisite pockets of even denser material, which eventually collapse under their own gravity to form stars.

The results suggest that star formation is more complex than astronomers had thought and may help them better understand the process, researchers said.

In this image, taken by NASA's Spitzer Space Telescope, the mysterious gas cloud G0.253+0.016 is the black object on the left. The Milky Way's center is the bright spot at right.

CREDIT: NASA/Spitzer/Benjamin et al., Churchwell

APEX Telescope: The Cool Clouds of the Carina Nebula

Observations made with the APEX telescope in submillimetre-wavelength light at a wavelength of 870 µm reveal the cold dusty clouds from which stars form in the Carina Nebula. 

This site of violent star formation, which plays host to some of the highest-mass stars in our galaxy, is an ideal arena in which to study the interactions between these young stars and their parent molecular clouds.

The APEX observations, made with its LABOCA camera, are shown here in orange tones, combined with a visible light image from the Curtis Schmidt telescope at the Cerro Tololo Interamerican Observatory. 

The result is a dramatic, wide-field picture that provides a spectacular view of Carina’s star formation sites. 

The nebula contains stars equivalent to over 25 000 Suns, and the total mass of gas and dust clouds is that of about 140 000 Suns.

Credit: ESO/APEX/T. Preibisch et al. (Submillimetre); N. Smith, University of Minnesota/NOAO/AURA/NSF (Optical)

ESA Herschel - Small Magellanic Star Formation in a Dwarf Galaxy

This image shows the Small Magellanic Cloud galaxy in infrared light from the Herschel Space Observatory, a European Space Agency-led mission, and NASA's Spitzer Space Telescope.

Considered dwarf galaxies compared to the big spiral of the Milky Way, the Large and Small Magellanic Clouds are the two biggest satellite galaxies of our home galaxy.

In combined data from Herschel and Spitzer, the irregular distribution of dust in the Small Magellanic Cloud becomes clear. A stream of dust extends to the left in this image, known as the galaxy's "wing," and a bar of star formation appears on the right.

The colors in this image indicate temperatures in the dust that permeates the Cloud. Colder regions show where star formation is at its earliest stages or is shut off, while warm expanses point to new stars heating surrounding dust.

The coolest areas and objects appear in red, corresponding to infrared light taken up by Herschel's Spectral and Photometric Imaging Receiver at 250 microns, or millionths of a meter.

Herschel's Photodetector Array Camera and Spectrometer fills out the mid-temperature bands, shown here in green, at 100 and 160 microns. The warmest spots appear in blue, courtesy of 24- and 70-micron data from Spitzer.

Image Credit: ESA/NASA/JPL-Caltech/STScI

ESA Herschel: The delicate balance of star formation in the Carina Nebula

A new image from ESA's Herschel Space Observatory reveals the glowing clouds of gas and dust in the Carina Nebula complex, one of the most massive stellar nurseries in the Milky Way.

The image provides a new view on this star-forming region at far-infrared wavelengths, disclosing the intricate structure of filaments, pillars and bubbles that pervades it.

Carved by winds and highly energetic radiation from massive stars, these features recount the history of star formation in the nebula: a result of the delicate balance between stellar feedback effects that may either halt or trigger the production of new generations of stars.

A site of intense star formation, the Carina Nebula complex is home to some of the brightest and most massive stars in our Galaxy, the Milky Way. The intricate network of clouds that populate this prolific cosmic nursery, where tens of thousands of new stars are forming, is revealed in unprecedented detail in a new image obtained with ESA's Herschel Space Observatory.

Observing the sky at far-infrared wavelengths, Herschel enables us to see the glow of cold material, such as the mixture of gas and dust that pervade the Carina Nebula complex. The image combines data acquired with the PACS instrument at 70 micron (shown in blue) and 160 micron (shown in green) and with the SPIRE instrument at 250 micron (shown in red).

As seen in the image, the complex exhibits a rich assortment of bubbles, filaments and pillars, and the various regions of the nebula span a wide range in densities, from diffuse and loosely bound areas to more compact concentrations of matter. Partly responsible for creating this tangled structure are the numerous high-mass stars hosted within this star-forming region - in the central region alone, the Carina Nebula boasts a census of more than a hundred very massive stars of type O, B and Wolf-Rayet.

These include the famous Eta Carinae, a Luminous Blue Variable star with a mass over 100 times that of the Sun; this highly unstable star gives rise to frequent and violent outbursts and is expected to explode as a supernova in the next few hundred thousand years.

Hubble Archive Image: Old star reveals Arsenic and Selenium

An ultraviolet spectrum taken from the Hubble Space Telescope public archives revealed arsenic and selenium in a 12 billion year-old halo star dubbed HD 160617.

"Arsenic and selenium elements were forged in an even older star, which has long since disappeared, and then-like genes passed on from parent to infant-they were born into the star we see today, HD 160617." reported Ian Roederer, along with co-author James Lawler.

The Big Bang produced lots of hydrogen and helium and a smidgen of lithium.

All heavier elements found on the periodic table have been produced by stars over the last 13.7 billion years. Astronomers analyze starlight to determine the chemical makeup of stars, the origin of the elements, the ages of stars, and the evolution of galaxies and the universe.

Now for the first time, astronomers have detected the presence of arsenic and selenium, neighbouring elements near the middle of the periodic table, in an ancient star in the faint stellar halo that surrounds the Milky Way.

Arsenic and selenium are elements at the transition from light to heavy element production, and have not been found in old stars until now.

Lead author of the Astrophysical Journal paper, Fellow Ian Roederer of the Carnegie Observatories explained: "Stars like our Sun can make elements up to oxygen on the periodic table. Other more massive stars can synthesize heavier elements, those with more protons in their nuclei, up to iron by nuclear fusion-the process in which atomic nuclei fuse and release lots of energy. Most of the elements heavier than iron are made by a process called neutron-capture nucleosynthesis."

"Although neutrons have no charge, they can decay into protons after they're in the nucleus, producing elements with larger atomic numbers. One of the ways that this method can work is by exposure to a burst of neutrons during the violent supernova death of a star."

"We call this process the rapid process (r-process). It can produce elements at the middle and bottom of the periodic table-from zinc to uranium-in the blink of an eye."

Roederer, with co-author James Lawler, looked at an ultraviolet spectrum from the Hubble Space Telescope public archives to find arsenic and selenium in a 12 billion year-old halo star dubbed HD 160617.

"These elements were forged in an even older star, which has long since disappeared, and then-like genes passed on from parent to infant-they were born into the star we see today, HD 160617."

The team also examined data for this star from the public archives of several ground-based telescopes and were able to detect 45 elements. In addition to arsenic and selenium, they found rarely seen cadmium, tellurium, and platinum, all of which were produced by the r-process.

This is the first time these elements have been detected together outside the Solar System. Astronomers cannot replicate the r-process in any laboratory since the conditions are so extreme. The key to modeling the r-process relies on astronomical observations.

"What I find exciting is that arsenic and selenium can be found in other stars, even ones like HD 160617 that we've been studying for decades," remarked Roederer.

"Now that we know where to look, we can go back and study these elements in other stars. Understanding the r-process helps us know why we find certain elements like barium on Earth, or understand why uranium is so rare."

JCMT: The first detailed image of filamentary structure in Orion A cloud

The first detailed image of filamentary structure traced in the Northern part of the Orion A cloud, showing where the stars are forming from clumps of cold gas and dust. 

The ability to image condensations of cold dust with the earlier SCUBA camera, and more recently with SCUBA-2, has made the JCMT one of the choice instruments in the world for studying the earliest stages of star formation.

Credit: Johnstone et al.

The JCMT Celebrates 25 years at the top of the world

The James Clerk Maxwell Telescope celebrates it's 25th anniversary. Named after the famous Scottish Physicist and Astronomer, James Clerk Maxwell who inspired Newton and other groundbreaking scientists.
 
W51, shown here, is located in the constellation of Aquila. It is one of the most massive regions of star formation within the galaxy. 

It is in stellar nurseries such as this that the stars form with enough mass to go on to end their lives in Supernova explosions. 

The background is a mid-infrared Spitzer image while the blue overlay is 850μm data from JCMT's SCUBA-2 in Hawaii, and is sponsored by the UK STFC.

Credit: Spitzer/GLIMPSE, JAC.

Dusty Stellar Nurseries from the Dark Side of a Galaxy

The red colours in this image show the galaxy M66 as it appears at the sub-mm wavelength of 850 microns, while the white background shows the galaxy as it appears in visible light. 

Regions of cold dust that appear as dark streaks in the white image glow brightly in the red image. 

The center of the galaxy contains much more dust than is obvious from looking at the visible image and the sub-mm image also picks out an unusual compact cloud in the southern part of the galaxy that is a prime site for future star formation. Credit: VLT/ESO, JAC, G. Bendo.

One of the world's most powerful cameras, SCUBA-2 is producing its first detailed images of our neighbouring galaxies, revealing previously undetected vast pockets of star formation where the next generation of stars is being created.

The light from these stars is usually obscured by dust, but at the sub-millimetre wavelengths that the camera is designed for, these dust lanes actually glow brightly. The images are revealed in the week of the 25th anniversary of the James Clerk Maxwell Telescope, in Hawaii on which SCUBA-2 is mounted.

"This exquisite image from the galaxy M66 in the constellation Leo is exactly the promising start we were hoping for," said Dr. Stephen Serjeant, the team's co-leader from The Open University. "This is a wonderfully exciting taste of things to come."

When looking up at the Milky Way, an irregular pattern of dark regions obscures the light of the stars. The dark patches are caused by clouds of dust trailing through the spiral arms and blocking out the starlight that would otherwise reveal vast pockets of star formation, or stellar nurseries. These dark lanes are not exclusive to the Milky Way, but can be found in all spiral galaxies.

SCUBA-2, led by STFC's UK Astronomy Technology Centre in Edinburgh is the most powerful camera ever developed for observing light at sub-milimetre wavelengths, 1000 times longer than we can see with our eyes.

This makes it possible to detect stellar nurseries usually obscured by dust that are so remote the light they emit left them within the first billion years after the big bang.

University of Edinburgh astrophysicist Professor James Dunlop said: "These beautiful new images from SCUBA-2 show energy conservation in action, as the same dust which absorbs the blue optical light (obscuring the stars in the optical images) can be seen to re-emit at the much longer wavelengths accessible to SCUBA-2."

This image promises to be the first of many stunning results from the James Clerk Maxwell Telescope Nearby Galaxy Legacy Survey (NGLS). The main aim of the survey is to understand how the broader environment of a galaxy affects its gas and dust content.

For example, galaxies in dense clusters can lose their gas and dust through interactions with other galaxies in the cluster or simply by the head wind they feel while moving through the hot gas trapped inside the cluster.

The NGLS is an international collaboration led by astronomers from Canada, the Netherlands, and the United Kingdom which is using SCUBA-2 to observe 150 galaxies in the local universe.

The NGLS team has spent much of the last five years studying molecular hydrogen emission using another instrument on the James Clerk Maxwell Telescope.

"It is very exciting to now see the first results from the SCUBA-2 side of our programme starting to come in," says Professor Christine Wilson, the Principal Investigator from McMaster University in Canada.

"We have a unique sample of galaxies that we are studying and having SCUBA-2 data will let us measure their gas and dust content. Gas and dust usually go hand-in-hand in galaxies, but from time to time, you find a surprise."

STFC is the UK sponsor of astronomy and operates the Joint Astronomy Centre in Hawaii.

Pulsar Stars to act as a Navigation Aid for Spacecraft

Spacecraft could one day navigate through the cosmos using a particular type of dead star as a kind of GPS.

German scientists are developing a technique that allows for very precise positioning anywhere in space by picking up X-ray signals from pulsars.

These dense, burnt-out stars rotate rapidly, sweeping their emission across the cosmos at rates that are so stable they rival atomic clock performance.

This timing property is perfect for interstellar navigation, says the team.

If a spacecraft carried the means to detect the pulses, it could compare their arrival times with those predicted at a reference location.

This would enable the craft to determine its position to an accuracy of just five kilometres anywhere in the galaxy.

"The principle is so simple that it will definitely have applications," said Prof Werner Becker from the Max-Planck Institute for Extraterrestrial Physics in Garching.

"These pulsars are everywhere in the Universe and their flashing is so predictable that it makes such an approach really straightforward," he told BBC News.

Prof Becker has been describing his team's research here at the UK National Astronomy Meeting in Manchester.

The proposed technique is very similar to that employed in the popular Global Positioning System, which broadcasts timing signals to the user from a constellation of satellites in orbit.

But GPS only works on, or just above, the Earth so it has no use beyond our planet.

Currently, mission controllers wanting to work out the position of their spacecraft deep in the Solar System will study the differences in time radio communications take to travel to and from the satellite. It is a complex process and requires several antennas dotted across the Earth.

It is also a technique that is far from precise, and the errors increase the further away the probe moves.

For the most distant spacecraft still in operation - Nasa's Voyager satellites, which are now approaching the very edge of the Solar System, some 18 billion km away - the errors associated with their positions are on the order of several hundred km.

NASA Hubble Image: El Dorado Galaxies

NASA's Hubble Space Telescope has produced this beautiful image of the galaxy NGC 1483.

NGC 1483 is a barred spiral galaxy located in the southern constellation of Dorado, the dolphinfish (or Mahi-mahi fish) in Spanish.

The nebulous galaxy features a bright central bulge and diffuse arms with distinct star-forming regions.

Many other distant galaxies can be seen in the background.


The constellation Dorado is home to the Dorado Group of galaxies, a loose group comprised of an estimated 70 galaxies and located some 62 million light-years away.

The Dorado group is much larger than the Local Group that includes the Milky Way, which contains around 30 galaxies. It also approaches the size of a galaxy cluster.

Galaxy clusters are the largest groupings of galaxies (and indeed the largest structures of any type) in the universe to be held together by their gravity.

Barred spiral galaxies are so named because of the prominent bar-shaped structures found in their center. They form about two thirds of all spiral galaxies, including the Milky Way.

Recent studies suggest that bars may be a common stage in the formation of spiral galaxies, and may indicate that a galaxy has reached full maturity.

Image Credit: ESA/Hubble & NASA

Notre Dame astrophysicists identify missing fuel for galactic star formation

The Milky Way will have the fuel to continue forming stars, thanks to massive clouds of ionized gas raining down from its halo and intergalactic space.

This is the conclusion of a new study by Nicolas Lehner and Christopher Howk from the University of Notre Dame, Indiana.

Using the Cosmic Origins Spectrograph, one of the newest instruments on the NASA/ESA Hubble Space Telescope, these researchers measured for the first time the distances to fast-moving clouds of ionized gas previously seen covering a large fraction of the sky.

These fast-moving clouds reside in the distant reaches of the Milky Way and contain huge quantities of gas.

The Milky Way would rapidly change its gas into stars if no supply of new matter were available to replenish the gas.

Astronomers have hypothesized that the ionised fast-moving gas clouds could be this reservoir of gas, but it was not known if they were interacting with the Milky Way.

“Our findings explain why the Milky Way can keep having star formation,” Lehner said. “Knowing the distances to these clouds tells us where the gaseous fuel is for forming stars over billions of years.”

Gas clouds can be identified and studied because elements in the cloud absorb small amounts of light from a star or other light source as it passes through a cloud on its way to Earth. The characteristic “fingerprint” left in the spectrum allows astronomers to determine the properties of the gas.

Star formation in the Milky Way
Earlier studies of these fast-moving ionised clouds used light from quasars, which are too far away to mark the clouds’ locations.

To solve the problem, Lehner and Howk identified 27 stars around the Milky Way whose distances were known and used Hubble to take line-of-sight readings of light coming from them.

Results from the stellar sample showed the ionized clouds largely resided in the Milky Way’s halo. The authors concluded that these flows of ionized gas are within about 1 galactic radius (40,000 light-years) of Earth.

The new Hubble observations revealed the presence of ionized gas in half the stellar samples, comparable to the fraction observed toward more distant quasars.

The gas clouds are not uniformly distributed around the galaxy, but rather collected in different areas.

They cover only part of our galactic sky, analogous to the partial coverage of the sky on a partly cloudy day on Earth.

This research also confirmed models that predicted gas falling into the Milky Way slows as it approaches. Clouds closer to the galaxy seem to have been decelerated and do not move as fast as those farther away, much like a meteorite slowing as it enters Earth’s atmosphere.

“We know now where is the missing fuel for galactic star formation,”

Lehner said. “We now have to learn how it got there.”

NASA Hubble Image: ARP 274 - A Tale of Three Galaxies

Arp 274, also known as NGC 5679, is a system of three galaxies that appear to be partially overlapping in the image, although they may be at somewhat different distances.

The spiral shapes of two of these galaxies appear mostly intact. The third galaxy (to the far left) is more compact, but shows evidence of star formation.

Two of the three galaxies are forming new stars at a high rate.

This is evident in the bright blue knots of star formation that are strung along the arms of the galaxy on the right and along the small galaxy on the left.

The largest component is located in the middle of the three. It appears as a spiral galaxy, which may be barred. The entire system resides at about 400 million light-years away from Earth in the constellation Virgo.

Hubble’s Wide Field Planetary Camera 2 was used to image Arp 274 in april 2011. Blue, visible and infrared filters were combined with a filter that isolates hydrogen emission.

The colours in this image reflect the intrinsic colour of the different stellar populations that make up the galaxies.

Yellowish older stars can be seen in the central bulge of each galaxy. A bright central cluster of stars pinpoint each nucleus.

Younger blue stars trace the spiral arms, along with pinkish nebulae that are illuminated by new star formation.

Interstellar dust is silhouetted against the starry population. A pair of foreground stars inside our own Milky Way are at far right.

Credit: NASA, ESA, and M. Livio and the Hubble Heritage Team (STScI/AURA)

NGC 6188 and NGC 6164 Nebulae

Fantastic shapes lurk in clouds of glowing hydrogen gas in NGC 6188.

The emission nebula is found near the edge of a large molecular cloud, unseen at visible wavelengths, in the southern constellation Ara, about 4,000 light-years away.

Massive, young stars of the embedded Ara OB1 association were formed in that region only a few million years ago, sculpting the dark shapes and powering the nebular glow with stellar winds and intense ultraviolet radiation.

The recent star formation itself was likely triggered by winds and supernova explosions, from previous generations of massive stars, that swept up and compressed the molecular gas.

Joining NGC 6188 on this cosmic canvas is rare emission nebula NGC 6164, also created by one of the region's massive O-type stars.

Similar in appearance to many planetary nebulae, NGC 6164's striking, symmetric gaseous shroud and faint halo surround its bright central star at the upper right.

The field of view spans about two full Moons, corresponding to 70 light years at the estimated distance of NGC 6188.

ESO VLT Image: Drama of star formation

This very detailed false-colour image from ESO’s Very Large Telescope shows the dramatic effects of very young stars on the dust and gas from which they were born in the star-forming region NGC 6729.

The baby stars are invisible in this picture, being hidden behind dust clouds at the upper left of the picture, but material they are ejecting is crashing into the surroundings at speeds of that can be as high as one million kilometres per hour.

This picture was taken by the FORS1 instrument and records the scene in the light of glowing hydrogen and sulphur.

ESA Herschel Images: Eagle Constellation

This image is taken looking towards a region of the Galaxy in the Eagle constellation, closer to the Galactic centre than our Sun. Here, we see the outstanding end-products of the stellar assembly line.

At the centre and the left of the image, the two massive star-forming regions G29.9 and W43 are clearly visible. These mini-starbursts are forming, as we speak, hundreds and hundreds of stars of all sizes: from those similar to our Sun, to monsters several tens of times heavier than our Sun.

These newborn large stars are catastrophically disrupting their original gas embryos by kicking away their surroundings and excavating giant cavities in the Galaxy. This is clearly visible in the 'fluffy chimney' below W43.

Credits: ESA/Hi-GAL Consortium