June 11, 2016

Hubble finds clues to the birth of supermassive black holes

supermassive black holes

Astrophysicists have taken a major step forward in understanding how supermassive black holes formed. Using data from Hubble and two other space telescopes, Italian researchers have found the best evidence yet for the seeds that ultimately grow into these cosmic giants.

For years astronomers have debated how the earliest generation of supermassive black holes formed very quickly, relatively speaking, after the Big Bang. Now, an Italian team has identified two objects in the early Universe that seem to be the origin of these early supermassive black holes. The two objects represent the most promising black hole seed candidates found so far.

The group used computer models and applied a new analysis method to data from the NASA Chandra X-ray Observatory, the NASA/ESA Hubble Space Telescope, and the NASA Spitzer Space Telescope to find and identify the two objects. Both of these newly discovered black hole seed candidates are seen less than a billion years after the Big Bang and have an initial mass of about 100 000 times the Sun.

“Our discovery, if confirmed, would explain how these monster black holes were born,” said Fabio Pacucci, lead author of the study, of Scuola Normale Superiore in Pisa, Italy.

This new result helps to explain why we see supermassive black holes less than one billion years after the Big Bang.

There are two main theories to explain the formation of supermassive black holes in the early Universe. One assumes that the seeds grow out of black holes with a mass about ten to a hundred times greater than our Sun, as expected for the collapse of a massive star. The black hole seeds then grew through mergers with other small black holes and by pulling in gas from their surroundings. However, they would have to grow at an unusually high rate to reach the mass of supermassive black holes already discovered in the billion years young Universe.

The new findings support another scenario where at least some very massive black hole seeds with 100 000 times the mass of the Sun formed directly when a massive cloud of gas collapses [2]. In this case the growth of the black holes would be jump started, and would proceed more quickly.

“There is a lot of controversy over which path these black holes take,” said co-author Andrea Ferrara also of Scuola Normale Superiore. “Our work suggests we are converging on one answer, where black holes start big and grow at the normal rate, rather than starting small and growing at a very fast rate.”

Andrea Grazian, a co-author from the National Institute for Astrophysics in Italy explains: “Black hole seeds are extremely hard to find and confirming their detection is very difficult. However, we think our research has uncovered the two best candidates so far.”

Even though both black hole seed candidates match the theoretical predictions, further observations are needed to confirm their true nature. To fully distinguish between the two formation theories, it will also be necessary to find more candidates.

The team plans to conduct follow-up observations in X-rays and in the infrared range to check whether the two objects have more of the properties expected for black hole seeds. Upcoming observatories, like the NASA/ESA/CSA James Webb Space Telescope and the European Extremely Large Telescope will certainly mark a breakthrough in this field, by detecting even smaller and more distant black holes.

Image Credit: NASA/CXC/M. Weiss
Explanation from: https://www.spacetelescope.org/news/heic1610/

Wide-field view of the Tarantula Nebula and its surroundings

Tarantula Nebula

This ground-based view of the Tarantula Nebula shows the nebula in its entirety. It is the brightest region of star formation in the local Universe. Hubble’s field of view covers just a tiny spot in the upper-right quadrant of this image, though it reveals detail invisible here, including a supernova remnant.

Image Credit: NASA, ESA, Digitized Sky Survey 2, Davide De Martin
Explanation from: https://www.spacetelescope.org/images/heic1105d/

The Flame Nebula (NGC 2024)

The Flame Nebula (NGC 2024)

The Flame Nebula sits on the eastern hip of Orion the Hunter, a constellation most easily visible in the northern hemisphere during winter evenings. This view of the nebula was taken by WISE, NASA's Wide-field Infrared Survey Explorer.

This image shows a vast cloud of gas and dust where new stars are being born. Three familiar nebulae are visible in the central region: the Flame Nebula, the Horsehead Nebula and NGC 2023. The Flame Nebula is the brightest and largest in the image. It is lit by a star inside it that is 20 times the mass of the sun and would be as bright to our eyes as the other stars in Orion's belt if it weren't for all the surrounding dust, which makes it appear 4 billion times dimmer than it actually is.

Image Credit: NASA/JPL-Caltech/UCLA
Explanation from: http://www.nasa.gov/multimedia/imagegallery/image_feature_2317.html

June 10, 2016

England seen from the International Space Station

England seen from the International Space Station

ISS, Orbit of the Earth
April 2016

Image Credit: ESA/NASA

Veil Nebula Detail (IC 340)

Veil Nebula Detail (IC 340)

This is a supernova remnant in the constellation Cygnus approximately 1,470 light years away. It formed from the debris of an star that exploded over 5,000 years ago.

Image Credit & Copyright: J P Metsävainio
Explanation by: Royal Observatory Greenwich

The Fornax Dwarf Spheroidal Galaxy

Fornax Dwarf Spheroidal Galaxy

The Fornax dwarf galaxy is one of our Milky Way’s neighbouring dwarf galaxies. The Milky Way is, like all large galaxies, thought to have formed from smaller galaxies in the early days of the Universe. These small galaxies should also contain many very old stars, just as the Milky Way does, and a team of astronomers has now shown that this is indeed the case. This image was composed from data from the Digitized Sky Survey 2.

Image Credit: ESO/Digitized Sky Survey 2
Explanation from: https://www.eso.org/public/images/eso1007a/

June 9, 2016

Moon seen from the International Space Station

Moon seen from the International Space Station

A gibbous Moon is visible in this view of Earth’s horizon and atmosphere, photographed by an Expedition 16 crewmember on the International Space Station while Space Shuttle Discovery (STS-120) is docked with the station.

Image Credit: NASA

Reflection nebula NGC 1999

Reflection nebula NGC 1999

This image is centred on NGC 1999, an area situated below Orion’s Belt. The scatter of the bright blue stars illuminates the billowing dust and gas clouds dancing across the image.

Image Credit & Copyright: Marco Lorenzi
Explanation by: Royal Observatory Greenwich

Galaxy cluster MACS J0416.1–2403 with dark matter map

MACS J0416.1–2403

This is a NASA/ESA Hubble Space Telescope image of the galaxy cluster MACS J0416.1–2403. Shown in blue on the image is a map of the dark matter found within the cluster. This cluster was part of a study of 72 galaxy cluster collisions which determined that dark matter interacts with other dark matter even less than previously thought.

Image Credit: NASA, ESA, D. Harvey (École Polytechnique Fédérale de Lausanne, Switzerland), R. Massey (Durham University, UK) and HST Frontier Fields
Explanation from: https://www.spacetelescope.org/images/heic1506e/

June 8, 2016

Aurora and British Isles seen from the International Space Station

Aurora and British Isles seen from the International Space Station

ISS, Orbit of the Earth
April 2016

Image Credit: ESA/NASA

Hubble captures spectacular “landscape” in the Carina Nebula

Carina Nebula

The NASA/ESA Hubble Space Telescope captured this billowing cloud of cold interstellar gas and dust rising from a tempestuous stellar nursery located in the Carina Nebula, 7500 light-years away in the southern constellation of Carina. This pillar of dust and gas serves as an incubator for new stars and is teeming with new star-forming activity.

Hot, young stars erode and sculpt the clouds into this fantasy landscape by sending out thick stellar winds and scorching ultraviolet radiation. The low density regions of the nebula are shredded while the denser parts resist erosion and remain as thick pillars. In the dark, cold interiors of these columns new stars continue to form.

In the process of star formation, a disc around the proto-star slowly accretes onto the star's surface. Part of the material is ejected along jets perpendicular to the accretion disc. The jets have speeds of several hundreds of miles per second. As these jets plough into the surrounding nebula, they create small, glowing patches of nebulosity, called Herbig-Haro (HH) objects.

Long streamers of gas can be seen shooting in opposite directions off the pedestal on the upper right-hand side of the image. Another pair of jets is visible in a peak near the top-centre of the image. These jets (known as HH 901 and HH 902, respectively) are common signatures of the births of new stars.

Image Credit: NASA, ESA, and M. Livio, the Hubble Heritage Team
Explanation from: http://www.spacetelescope.org/images/heic1007e/

A star formation laboratory: the NGC 4214 Galaxy

NGC 4214

Hubble has taken an image of galaxy NGC 4214. This galaxy glows brightly with young stars and gas clouds, and is an ideal laboratory to research star formation and evolution.

Dwarf galaxy NGC 4214 may be small, but what it lacks in size it makes up for in content. It is packed with everything an astronomer could ask for, from hot, young star-forming regions to old clusters with red supergiants.

The intricate patterns of glowing ionised hydrogen gas, cavities blown clear of gas by stellar wind, and bright stellar clusters of NGC 4214 can be seen in this optical and near-infrared image, taken using the Wide Field Camera 3 (WFC3) instrument on the NASA/ESA Hubble Space Telescope.

A huge heart-shaped cavity — possibly the galaxy’s most eye-catching feature — can be seen at the centre of the image. Inside this hole lies a large cluster of massive, young stars ranging in temperature from 10 000 to 50 000 degrees Celsius. Their strong stellar winds are responsible for the creation of this hollow area. The resulting lack of gas prevents any further star formation from occurring in this region.

Located around 10 million light-years away in the constellation of Canes Venatici (The Hunting Dogs), the galaxy’s relative close proximity to us, combined with the wide variety of evolutionary stages among the stars, makes it an ideal laboratory to research what triggers star formation and evolution. By chance, there is relatively little interstellar dust between us and NGC 4214, making our measurements of it more accurate.

NGC 4214 contains a large amount of gas, some of which can be seen glowing red in the image, providing abundant material for star formation. The area with the most hydrogen gas, and consequently, the youngest clusters of stars (around two million years old), lies in the upper part of this Hubble image. Like most of the features in the image, this area is visible due to ionisation of the surrounding gas by the ultraviolet light of a young cluster of stars within.

Observations of this dwarf galaxy have also revealed clusters of much older red supergiant stars that we see at a late stage in their evolution. Additional older stars can be seen dotted all across the galaxy. While these are dominant in infrared emission they can only be seen shining faintly in this visible-light image. The variety of stars at different stages in their evolution, indicate that the recent and ongoing starburst periods are by no means the first, and the galaxy’s numerous ionised hydrogen regions suggest they will not be the last.

Image Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)-ESA/Hubble Collaboration
Explanation from: https://www.spacetelescope.org/news/heic1109/

June 7, 2016

Globular Cluster NGC 6496

Globular Cluster NGC 6496

This 10.5-billion-year-old globular cluster, NGC 6496, is home to heavy-metal stars of a celestial kind! The stars comprising this spectacular spherical cluster are enriched with much higher proportions of metals — elements heavier than hydrogen and helium, are in astronomy curiously known as metals — than stars found in similar clusters.

A handful of these high-metallicity stars are also variable stars, meaning that their brightness fluctuates over time. NGC 6496 hosts a selection of long-period variables — giant pulsating stars whose brightness can take up to, and even over, a thousand days to change — and short-period eclipsing binaries, which dim when eclipsed by a stellar companion.

The nature of the variability of these stars can reveal important information about their mass, radius, luminosity, temperature, composition, and evolution, providing astronomers with measurements that would be difficult or even impossible to obtain through other methods.

NGC 6496 was discovered in 1826 by Scottish astronomer James Dunlop. The cluster resides at about 35 000 light-years away in the southern constellation of Scorpius (The Scorpion).

Image Credit: ESA/Hubble, NASA, Judy Schmidt
Explanation from: https://www.spacetelescope.org/images/potw1622a/

The glowing gas cloud LHA 120-N55 in the Large Magellanic Cloud

gas cloud LHA 120-N55 in the Large Magellanic Cloud

In this image from ESO’s Very Large Telescope (VLT), light from blazing blue stars energises the gas left over from the stars’ recent formation. The result is a strikingly colourful emission nebula, called LHA 120-N55, in which the stars are adorned with a mantle of glowing gas. Astronomers study these beautiful displays to learn about the conditions in places where new stars develop.

LHA 120-N55, or N55 as it is usually known, is a glowing gas cloud in the Large Magellanic Cloud (LMC), a satellite galaxy of the Milky Way located about 163 000 light-years away. N55 is situated inside a supergiant shell, or superbubble called LMC 4. Superbubbles, often hundreds of light-years across, are formed when the fierce winds from newly formed stars and shockwaves from supernova explosions work in tandem to blow away most of the gas and dust that originally surrounded them and create huge bubble-shaped cavities.

The material that became N55, however, managed to survive as a small remnant pocket of gas and dust. It is now a standalone nebula inside the superbubble and a grouping of brilliant blue and white stars — known as LH 72 — also managed to form hundreds of millions of years after the events that originally blew up the superbubble. The LH 72 stars are only a few million years old, so they did not play a role in emptying the space around N55. The stars instead represent a second round of stellar birth in the region.

The recent rise of a new population of stars also explains the evocative colours surrounding the stars in this image. The intense light from the powerful, blue–white stars is stripping nearby hydrogen atoms in N55 of their electrons, causing the gas to glow in a characteristic pinkish colour in visible light. Astronomers recognise this telltale signature of glowing hydrogen gas throughout galaxies as a hallmark of fresh star birth.

While things seem quiet in the star-forming region of N55 for now, major changes lie ahead. Several million years hence, some of the massive and brilliant stars in the LH 72 association will themselves go supernova, scattering N55’s contents. In effect, a bubble will be blown within a superbubble, and the cycle of starry ends and beginnings will carry on in this close neighbour of our home galaxy.

Image Credit: ESO
Explanation from: https://www.eso.org/public/news/eso1616/

The Helix Nebula

The Helix Nebula

The Helix Nebula (NGC 7293) is a challenging stargazing target for amateur astronomers. It is one of the closest planetary nebulas -- a type of nebula formed from gas ejected by a dying sunlike star. Yet it is so large and spread out in the sky that it appears very dim in a telescope eyepiece. Long-exposure photographs unveil the true beauty of this celestial wonder.

Although named for its resemblance to a coiling spiral seen face on, the Helix Nebula has a more complex three-dimensional structure. Previous studies showed that it consists of two gaseous disks nearly perpendicular to each other. Observers on Earth view the main disk nearly face on, making it appear more ring-shaped.

In addition to its overall structure, the Helix proved to be surprisingly complex even at the smallest scale visible to Spitzer.

"Most planetary nebulas look diffuse and uniform through telescopes," explained Joseph Hora of the Harvard-Smithsonian Center for Astrophysics (CfA), who leads the team that took the image. "Because the Helix is so close, we can see more details of its fine structure. Spitzer shows that the Helix is clumpy at very small scales."

The most striking feature of the Helix, first revealed by ground-based images, is its collection of thousands of distinct blobs that resemble comets due to their compact heads and long, streaming tails. Each "cometary knot" is much larger than an actual comet, spanning about twice the size of our solar system. Each knot holds about an Earth-mass of hydrogen and other gases that were expelled from the nebula's central star thousands of years ago.

In the Spitzer image, the cometary knots show peculiar color-coding with blue-green heads and reddish tails. The bluer, more energetic radiation at the tips comes from molecular hydrogen that has been excited by ultraviolet radiation from the nebula's central star or shocked from its fast-moving stellar wind. The tails lie behind the main body of the knots and are relatively shielded. As a result, they emit redder, less energetic radiation.

The Spitzer image shows a clear trend for the nebula as a whole to become redder at greater distances from the central star. The clumpy appearance extends beyond the innermost part of the nebula, although the distinct cometary features disappear. Overall, the Spitzer image displays a constantly changing region where powerful radiation from a hot stellar core is blasting outward and eroding surrounding material. Eventually, the beautiful gaseous streamers of the Helix will vanish, destroyed by the star that created them in the first place.

The Helix Nebula is located about 650 light-years away towards the constellation Aquarius.

Image Credit: NASA/JPL-Caltech/J. Hora (Harvard-Smithsonian CfA)
Explanation from: http://www.spitzer.caltech.edu/news/750-ssc2006-01-Spitzer-Puts-a-New-Spin-on-the-Helix-Nebula

June 6, 2016

Dwarf Galaxy Holmberg IX

Dwarf Galaxy Holmberg IX

This loose collection of stars is actually a dwarf irregular galaxy, called Holmberg IX. It resides just off the outer edge of M81, a large spiral galaxy in Ursa Major. This image was taken with Hubble's Advanced Camera for Surveys in early 2006. Holmberg IX is of the so-called Magellanic type of galaxy, as its size and irregularity in structure are similar to the Small Magellanic Cloud, a neighbour to our own Milky Way. Holmberg IX was first discovered by astronomer Sidney van den Bergh in 1959, and catalogued as DDO 66. The galaxy received its "Holmberg IX" naming when it was discussed in Eric Holmberg's study of groups of galaxies ten years later. It is suspected that the dwarf galaxy was created as a result of a galactic interaction between M81 and neighbouring galaxy M82.

Of the more than 20,000 stars that can be resolved in this Hubble image, only about 10% are considered to be old stars with ages of billions of years. The rest are thought to be young stars with ages of only 10 - 200 million years. Due to the Advanced Camera for Surveys' resolution in this image, astronomers have noted that the old and the young stars have distinct spatial distributions which might be related to their origin.

Simulations predict that the triplet M81, M82, and nearby NGC 3077 had a close passage 200-300 million years ago. This close encounter may have triggered the newer star formation that has occurred in Holmberg IX.

The bluish-white fuzz in the space surrounding M81 and Holmberg IX is new star formation triggered by gravitational interactions between the two galaxies. There are many low mass galaxies that form stars in nearby space. While none of these are as dominated by recently produced stars as Holmberg IX, they might be related to the same family. By understanding how Holmberg IX was formed, scientists hope to understand their role as building blocks of large galaxies.

Image Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA), D. de Mello (Catholic University of America and GSFC)
Explanation from: http://spacetelescope.org/images/heic0801g/

H II Region Gum 15

H II Region Gum 15

The smokey black silhouette in this new image is part of a large, sparse cloud of partially ionised hydrogen — an HII region — known as Gum 15. In wide-field images this nebula appears as a striking reddish purple clump dotted with stars and slashed by opaque, weaving dust lanes. This image homes in on one of these dust lanes, showing the central region of the nebula.

These dark chunks of sky have seemingly few stars because lanes of dusty material are obscuring the bright, glowing regions of gas beyond. The occasional stars that do show up in these patches are actually between us and Gum 15, but create the illusion that we are peering through a window out onto the more distant sky.

Gum 15 is shaped by the aggressive winds flowing from the stars within and around it. The cloud is located near to several large associations of stars including the star cluster ESO 313-13. The brightest member of this cluster, named HD 74804, is thought to have ionised Gum 15’s hydrogen cloud. This ionised hydrogen content is the cause of the red hue permeating the frame.

This image was taken as part of the ESO Cosmic Gems programme using the FORS instrument on the Very Large Telescope at ESO’s Paranal Observatory in Chile. This project has actually produced multiple images of this target — back in July 2014, ESO released a stunning wide-field image of Gum 15 with the Wide Field Imager on the MPG/ESO 2.2-metre telescope at the La Silla Observatory that showed the nebula’s sculpted clouds, murky dust, and brightly shining stars in extraordinary detail. The portion of Gum 15 shown in the new and more detailed VLT image can be seen within the wider frame towards the top left quarter of the 2.2-metre image.

Image Credit: ESO
Explanation from: https://www.eso.org/public/images/potw1444a/

Milky Way Galaxy in the Infrared

Milky Way Galaxy in the Infrared

This composite color infrared image of the center of our Milky Way galaxy reveals a new population of massive stars and new details in complex structures in the hot ionized gas swirling around the central 300 light-years. This sweeping panorama is the sharpest infrared picture ever made of the Galactic core and offers a laboratory for how massive stars form and influence their environment in the often violent nuclear regions of other galaxies.

This view combines the sharp imaging of the Hubble Space Telescope's Near Infrared Camera and Multi-Object Spectrometer (NICMOS) with color imagery from a previous Spitzer Space Telescope survey done with its Infrared Astronomy Camera (IRAC). The Galactic core is obscured in visible light by intervening dust clouds, but infrared light penetrates the dust.

NICMOS shows a large number of these massive stars distributed throughout the region. A new finding is that astronomers now see that the massive stars are not confined to one of the three known clusters of massive stars in the Galactic Center, known as the Central cluster, the Arches cluster, and the Quintuplet cluster. These three clusters are easily seen as tight concentrations of bright, massive stars in the NICMOS image. The distributed stars may have formed in isolation, or they may have originated in clusters that have been disrupted by strong gravitational tidal forces. The winds and radiation from these stars form the complex structures seen in the core, and in some cases, they may be triggering new generations of stars.

Image Credit: Hubble: NASA, ESA, and Q.D. Wang (University of Massachusetts, Amherst); Spitzer: NASA, Jet Propulsion Laboratory, and S. Stolovy (Spitzer Science Center/Caltech)
Explanation from: http://www.nasa.gov/multimedia/imagegallery/image_feature_1578.html

June 5, 2016

The Cat's Eye Nebula

Cat's Eye Nebula

This composite of data from NASA's Chandra X-ray Observatory and Hubble Space Telescope is a new look for NGC 6543, better known as the Cat's Eye nebula. This famous object is a so-called planetary nebula that represents a phase of stellar evolution that the Sun should experience several billion years from now. When a star like the Sun begins to run out of fuel, it becomes what is known as a red giant. In this phase, a star sheds some of its outer layers, eventually leaving behind a hot core that collapses to form a dense white dwarf star. A fast wind emanating from the hot core rams into the ejected atmosphere, pushes it outward, and creates the graceful filamentary structures seen with optical telescopes.

Chandra's X-ray data (colored in blue) of NGC 6543 shows that its central star is surrounded by a cloud of multi-million-degree gas. By comparing where the X-rays lie in relation to the structures seen in optical light by Hubble (red and purple), astronomers were able to deduce that the chemical abundances in the region of hot gas were like those in the wind from the central star and different from the outer cooler material. In the case of the Cat's Eye, material shed by the star is flying away at a speed of about 4 million miles per hour. The star itself is expected to collapse to become a white dwarf star in a few million years.

Image Credit: NASA/CXC/SAO; Optical: NASA/STScI
Explanation from: http://chandra.si.edu/photo/2008/catseye/

Digitized Sky Survey Image of the Omega Nebula (M 17)

Omega Nebula

This image is a colour composite of the Omega Nebula (M 17) made from exposures from the Digitized Sky Survey 2 (DSS2). The field of view is approximatelly 4.7 x 3.7 degrees.

Image Credit: ESO/Digitized Sky Survey 2, Davide De Martin.
Explanation from: http://www.eso.org/public/images/eso0925b/

Artist's Impression of the huge outflow ejected from the Quasar SDSS J1106+1939

SDSS J1106+1939

This artist’s impression shows the material ejected from the region around the supermassive black hole in the quasar SDSS J1106+1939. This object has the most energetic outflows ever seen, at least five times more powerful than any that have been observed to date. Quasars are extremely bright galactic centres powered by supermassive black holes. Many blast huge amounts of material out into their host galaxies, and these outflows play a key role in the evolution of galaxies. But, before this object was studied, the observed outflows weren’t as powerful as predicted by theorists. The very bright quasar appears at the centre of the picture and the outflow spreads about 1000 light-years out into the surrounding galaxy.

Image Credit: ESO/L. Calçada
Explanation from: https://www.eso.org/public/images/eso1247a/