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Thursday, April 24, 2014

X-Ray View of the COSMOS Survey


When we gaze up at the night sky, we are only seeing part of the story. Unfortunately, some of the most powerful and energetic events in the Universe are invisible to our eyes – and to even the best optical telescopes.

Luckily, these events are not lost; they appear vividly in the high-energy sky, making them visible to space-based telescopes like ESA's XMM-Newton, which observes the Universe in the X-ray part of the spectrum.

This image shows a patch of sky from the COSMOS survey, as viewed by XMM-Newton. COSMOS is a project studying how galaxies form and evolve, gathering observations using a variety of ground- and space-based telescopes. This image alone features about two thousand supermassive black holes, and over a hundred clusters of galaxies.

Small point sources dotted across the frame show supermassive black holes that are hungrily devouring matter from their surroundings. All massive galaxies host a black hole at their core, but not all of these are actively accreting, dragging in surrounding matter and releasing high-energy radiation and powerful jets in the process. As they are so energetic, one of the best ways to hunt these extreme bodies is by using X-ray telescopes.

The larger blobs in this image, mainly red and yellow, reveal another class of cosmic behemoths: galaxy clusters. Containing up to several thousand galaxies, galaxy clusters are the largest cosmic structures to be held together by gravity. The galaxies within these clusters are enveloped by hot gas, which releases a diffuse X-ray glow that can be detected by telescopes like XMM-Newton.

The image combines data collected by the EPIC instrument on board XMM-Newton at energies from 0.5 to 2 keV (shown in red), 2 to 4.5 keV (shown in green) and 4.5 to 10 keV (shown in blue). The observations were taken between 2003 and 2005, and the image spans 1.4 degrees on each side, corresponding to almost three times the diameter of the full Moon.

This image was first published in the paper “The XMM-Newton Wide-Field Survey in the COSMOS Field. I. Survey Description” by G. Hasinger et al. in 2007.

Image credit: ESA/XMM-Newton/Gunther Hasinger, Nico Cappelluti, and the XMM-COSMOS collaboration.

Wednesday, April 23, 2014

Unique Pair of Hidden Black Holes Discovered by XMM-Newton


A pair of supermassive black holes in orbit around one another have been spotted by XMM-Newton. This is the first time such a pair have been seen in an ordinary galaxy. They were discovered because they ripped apart a star when the space observatory happened to be looking in their direction.

Most massive galaxies in the Universe are thought to harbor at least one supermassive black hole at their center. Two supermassive black holes are the smoking gun that the galaxy has merged with another. Thus, finding binary supermassive black holes can tell astronomers about how galaxies evolved into their present-day shapes and sizes.

To date, only a few candidates for close binary supermassive black holes have been found. All are in active galaxies where they are constantly ripping gas clouds apart, in the prelude to crushing them out of existence.

In the process of destruction, the gas is heated so much that it shines at many wavelengths, including X-rays. This gives the galaxy an unusually bright center, and leads to it being called active. The new discovery, reported by Fukun Liu, Peking University, Beijing, China, and colleagues, is important because it is the first to be found in a galaxy that is not active.

"There might be a whole population of quiescent galaxies that host binary black holes in their centers," says co-author Stefanie Komossa, Max-Planck-Institut für Radioastronomie, Bonn, Germany. But finding them is a difficult task because in quiescent galaxies, there are no gas clouds feeding the black holes, and so the cores of these galaxies are truly dark.

The only hope that the astronomers have is to be looking in the right direction at the moment one of the black holes goes to work, and rips a star to pieces. Such an occurrence is called a 'tidal disruption event'. As the star is pulled apart by the gravity of the black hole, it gives out a flare of X-rays.

In an active galaxy, the black hole is continuously fed by gas clouds. In a quiescent galaxy, the black hole is fed by tidal disruption events that occur sporadically and are impossible to predict. So, to increase the chances of catching such an event, researchers use ESA's X-ray observatory, XMM-Newton, in a novel way.

Usually, the observatory collects data from designated targets, one at a time. Once it completes an observation, it slews to the next. The trick is that during this movement, XMM-Newton keeps the instruments turned on and recording. Effectively this surveys the sky in a random pattern, producing data that can be analyzed for unknown or unexpected sources of X-rays.

On 10 June 2010, a tidal disruption event was spotted by XMM-Newton in galaxy SDSS J120136.02+300305.5. Komossa and colleagues were scanning the data for such events and scheduled follow-up observations just days later with XMM-Newton and NASA's Swift satellite.

The galaxy was still spilling X-rays into space. It looked exactly like a tidal disruption event caused by a supermassive black hole but as they tracked the slowly fading emission day after day something strange happened.

The X-rays fell below detectable levels between days 27 and 48 after the discovery. Then they re-appeared and continued to follow a more expected fading rate, as if nothing had happened.

Now, thanks to Fukun Liu, the behavior can be explained. "This is exactly what you would expect from a pair of supermassive black holes orbiting one another," says Liu.

Liu had been working on models of black hole binary systems that predicted a sudden plunge to darkness and then the recovery because the gravity of one of the black holes disrupted the flow of gas onto the other, temporarily depriving it of fuel to fire the X-ray flare. He found that two possible configurations were possible to reproduce the observations of J120136.

In the first, the primary black hole contained 10 million solar masses and was orbited by a black hole of about a million solar masses in an elliptical orbit. In the second solution, the primary black hole was about a million solar masses and in a circular orbit.

In both cases, the separation between the black holes was relatively small: 0.6 milliparsecs, or about 2 thousandths of a light year. This is about the width of our Solar System.

Being this close, the fate of this newly discovered black hole pair is sealed. They will radiate their orbital energy away, gradually spiraling together, until in about two million years time they will merge into a single black hole.

Now that astronomers have found this first candidate for a binary black hole in a quiescent galaxy, the search is inevitably on for more. XMM-Newton will continue its slew survey. This detection will also spur interest in a network of telescopes that search the whole sky for tidal disruption events.

"Once we have detected thousands of tidal disruption events, we can begin to extract reliable statistics about the rate at which galaxies merge," says Komossa.

There is another hope for the future as well. When binary black holes merge, they are predicted to release a massive burst of energy into the Universe but not mostly in X-rays. "The final merger is expected to be the strongest source of gravitational waves in the Universe," says Liu.

Gravitational waves are ripples in the space-time continuum. Astronomers around the world are currently building a new type of observatory to detect these ripples. ESA are also involved in opening this new window on the Universe. In 2015, ESA will launch LISA Pathfinder, which will test the necessary technology for building a space-based gravitational wave detector that must be placed in space. The search for elusive gravitational waves is also the theme for one of ESA's next large science missions, the L3 mission in the Cosmic Vision program.

In the meantime, XMM-Newton will continue to look out for the tidal disruption events that betray the presence of binary supermassive black holes candidates.

"The innovative use of XMM-Newton's slew observations made the detection of this binary supermassive black hole system possible," says Norbert Schartel, ESA's XMM-Newton Project Scientist. "This demonstrates the important role that long-lasting space observatories have in detecting rare events that can potentially open new areas in astronomy."


Background Information

The results described in this article are reported in "A milli-parsec supermassive black hole binary candidate in the galaxy SDSS J120136.02+300305.5", by F.K. Liu, Shuo Li, and S. Komossa, published in the May 10 issue of The Astrophysical Journal, 2014, Volume 786; doi:10.1088/0004-637X/786/2/103

Illustration credit: ESA - C. Carreau

Monday, April 21, 2014

The Grand Canyon


The Grand Canyon in northern Arizona is a favorite for astronauts shooting photos from the International Space Station, as well as one of the best-known tourist attractions in the world. The steep walls of the Colorado River canyon and its many side canyons make an intricate landscape that contrasts with the dark green, forested plateau to the north and south.

The Colorado River has done all the erosional work of carving away cubic kilometers of rock in a geologically short period of time. Visible as a darker line snaking along the bottom of the canyon, the river lies at an altitude of 715 meters (2,345 feet), thousands of meters below the North and South Rims. Temperatures are furnace-like on the river banks in the summer. But Grand Canyon Village, the classic outlook point for visitors, enjoys a milder climate at an altitude of 2,100 meters (6,890 feet).

The Grand Canyon has become a geologic icon — a place where you can almost sense the invisible tectonic forces within the Earth. The North and South Rims are part of the Kaibab Plateau, a gentle tectonic swell in the landscape. The uplift of the plateau had two pronounced effects on the landscape that show up in this image. First, in drier parts of the world, forests usually indicate higher places; higher altitudes are cooler and wetter, conditions that allow trees to grow. The other geologic lesson on view is the canyon itself. Geologists now know that a river can cut a canyon only if the Earth surface rises vertically. If such uplift is not rapid, a river can maintain its course by eroding huge quantities of rock and forming a canyon.

This astronaut photograph (ISS039-E-5258) was taken on March 25, 2014 by the Expedition 39 crew, with a Nikon D3S digital camera using a 180 millimeter lens, and is provided by the ISS Crew Earth Observations Facility and the Earth Science and Remote Sensing Unit, Johnson Space Center. It has been cropped and enhanced to improve contrast, and lens artifacts have been removed.

Image credit: NASA

Sunday, April 20, 2014

Apollo 12 and Surveyor 3


On April 17, 1967, NASA's Surveyor 3 spacecraft launched from Cape Canaveral Air Force Station, Florida, on a mission to the lunar surface. A little more than two years after it landed on the moon with the goal of paving the way for a future human mission, the Surveyor 3 spacecraft got a visit from Apollo 12 Commander Charles Conrad Jr. and astronaut Alan L. Bean, who snapped this photo on November 20, 1969.

After Surveyor 1's initial studies of the lunar surface in 1966, Surveyor 3 made further inroads into preparations for human missions to the moon. Using a surface sampler to study the lunar soil, Surveyor 3 conducted experiments to see how the lunar surface would fare against the weight of an Apollo lunar module. The moon lander, which was the second of the Surveyor series to make a soft landing on the moon, also gathered information on the lunar soil's radar reflectivity and thermal properties in addition to transmitting more than 6,000 photographs of its surroundings.

The Apollo 12 Lunar Module, visible in the background at right, landed about 600 feet from Surveyor 3 in the Ocean of Storms. The television camera and several other pieces were taken from Surveyor 3 and brought back to Earth for scientific examination. Here, Conrad examines the Surveyor's TV camera prior to detaching it. Astronaut Richard F. Gordon Jr. remained with the Apollo 12 Command and Service Modules (CSM) in lunar orbit while Conrad and Bean descended in the LM to explore the moon.

Photo credit: NASA


Saturday, April 19, 2014

Galaxy Cluster CLASS B1608+656


An image of a galaxy cluster taken by the NASA/ESA Hubble Space Telescope gives a remarkable cross-section of the Universe, showing objects at different distances and stages in cosmic history. They range from cosmic near-neighbors to objects seen in the early years of the Universe. The 14-hour exposure shows objects around a billion times fainter than can be seen with the naked eye.

Hubble's images might look flat, but this one shows a remarkable depth of field that lets us see more than halfway to the edge of the observable Universe. Most of the galaxies visible here are members of a huge cluster called CLASS B1608+656, which lies about five billion light-years away. But the field also contains other objects, both significantly closer and far more distant, including quasar QSO-160913+653228 which is so distant its light has taken nine billion years to reach us, two-thirds of the time that has elapsed since the Big Bang.


Photo credit: NASA, ESA

Note: For more information, see A Cross-Section of the Universe.

Friday, April 18, 2014

Kepler-186f


This artist's concept depicts Kepler-186f, the first validated Earth-size planet to orbit a distant star in the habitable zone -- a range of distance from a star where liquid water might pool on the planet's surface. The discovery of Kepler-186f confirms that Earth-size planets exist in the habitable zones of other stars and signals a significant step closer to finding a world similar to Earth.

The size of Kepler-186f is known to be less than ten percent larger than Earth, but its mass, composition and density are not known. Previous research suggests that a planet the size of Kepler-186f is likely to be rocky. Prior to this discovery, the "record holder" for the most "Earth-like" planet went to Kepler-62f, which is 40 percent larger than the size of Earth and orbits in its star's habitable zone.

Kepler-186f orbits its star once every 130 days and receives one-third the energy that Earth does from the sun, placing it near the outer edge of the habitable zone. If you could stand on the surface of Kepler-186f, the brightness of its star at high noon would appear as bright as our sun is about an hour before sunset on Earth.

Kepler-186f resides in the Kepler-186 system about 500 light-years from Earth in the constellation Cygnus. The system is also home to four inner planets, seen lined up in orbit around a host star that is half the size and mass of the sun.

The artistic concept of Kepler-186f is the result of scientists and artists collaborating to imagine the appearance of these distant worlds.

Illustration credit: NASA/Ames/SETI Institute/JPL-Caltech

Note: For more information, see PIA18000: Kepler-186 and the Solar System, NASA's Kepler Telescope Discovers First Earth-Size Planet in 'Habitable Zone', and Earth-Size Planet Found In The 'Habitable Zone' of Another Star.

Thursday, April 17, 2014

Gum 41


This new image from the Wide Field Imager (WFI) on the MPG/ESO 2.2-meter telescope at the La Silla Observatory in Chile reveals a cloud of hydrogen and newborn stars called Gum 41. In the middle of this little-known nebula, brilliant hot young stars emit energetic radiation that causes the surrounding hydrogen to glow with a characteristic red hue.

Image credit: ESO

Note: For more information, see A Study in Scarlet.

Wednesday, April 16, 2014

IRAS 20324+4057, The Tadpole, and The Wriggler


A bright blue tadpole appears to swim through the inky blackness of space. Known as IRAS 20324+4057, but dubbed "the Tadpole," this clump of gas and dust has given birth to a bright, "protostar," one of the earliest steps in building a star. This image was taken by NASA's Hubble Space Telescope, and released publicly, in 2012.

There are actually multiple protostars within this tadpole's 'head," but the glowing yellow one in this image is the most luminous and massive. When this protostar has gathered together enough mass from its surroundings, it will eventually emerge as a fully-fledged young star.

The intense blue glow is caused by nearby stars firing ultraviolet radiation at IRAS 20324+4057, which also sculpts its tail into a long, wiggly shape. In total, this clump spans roughly a light-year from head to tail-tip, and contains gas weighing almost four times the mass of the sun.

Framed against a background of distant stars, IRAS 20324+4057 is making its way through the Cygnus OB2 association, a loose cluster of stars some 4,700 light-years from Earth in the constellation Cygnus. This association is one of the largest clusters known, and is famed for its heavyweight members. It contains some of the hottest, most massive and most luminous stars known, some of which are about two million times more luminous than the sun.

The Tadpole is not alone in this interstellar pond. Just out of view, to the bottom right of this image, lies another curious object dubbed "the Goldfish" by astronomers. The Goldfish is about half the length of IRAS 20324+4057, and is also thought to be a globule of gas that is being both lit up and sculpted by radiation from cluster stars.

Completing this trio is a small clump of blue gas, informally nicknamed "the Wriggler" by some astronomers, visible in the bottom left of this Hubble image. All three objects have the same orientation in the sky and appear to be brighter on their northern sides, leading astronomers to believe they are being shaped by aggressive winds and radiation flowing from hot Cygnus OB2 stars towards the top right of the frame.

Image credit: NASA/JPL-Caltech/ESA, the Hubble Heritage Team (STScI/AURA) and IPHAS

Note: For more information, see The Tadpole and The Wriggler.

Tuesday, April 15, 2014

Possible New Moon Forming Around Saturn


The disturbance visible at the outer edge of Saturn's A ring in this image from NASA's Cassini spacecraft could be caused by an object replaying the birth process of icy moons.

The image is adapted from one in a paper in the journal Icarus, reporting the likely presence of an icy body causing gravitational effects on nearby ring particles, producing the bright feature visible at the ring's edge. The object, informally called "Peggy," is estimated to be no more than about half a mile, or one kilometer, in diameter. It may be in the process of migrating out of the ring, a process that one recent theory proposes as a step in the births of Saturn's several icy moons.

This image is a portion of an observation recorded by the narrow-angle camera of Cassini's imaging science subsystem on April 15, 2013. The bright feature at the edge of the A ring is about 750 miles (about 1,200 kilometers) long.

This view looks toward the illuminated side of the rings from about 53 degrees above the plane of the rings. It was obtained from a distance of approximately 775,000 miles (1.2 kilometers) from Saturn, with a sun-Saturn-spacecraft, or phase, angle of 31 degrees. The scale is about 4 miles (about 7 kilometers) per pixel.

Photo credit: NASA/JPL-Caltech/Space Science Institute

Note: For more information, see NASA Cassini Images May Reveal Birth of a Saturn Moon and Possible New Moon Forming Around Saturn.

Sunday, April 13, 2014

Supernova Remnant G352.7-0.1


G352.7-0.1: A supernova remnant about 24,000 light years from Earth.

Supernova remnants are created when a massive star explodes and its remains are hurled into space. Astronomers have found a supernova remnant that it is sweeping up a remarkable amount of material -- equivalent to 45 times the mass of the Sun – as it expands. This supernova remnant is called G352.7-0.1 and is seen in this composite image containing X-rays from Chandra (blue), radio waves from the VLA (pink), infrared data from Spitzer (orange), and optical data from the DSS (white).

Scale: Image is about 14.5 arcmin across (1000 light years).

Image credit: X-ray: NASA/CXC/Morehead State Univ/T.Pannuti et al.; Optical: DSS; Infrared: NASA/JPLCaltech; Radio: NRAO/VLA/Argentinian Institute of Radioastronomy/G.Dubner

Note: For more information, see G352.7-0.1: Supernova Cleans Up its Surroundings.

Saturday, April 12, 2014

Possible Exomoon Found



Researchers have detected the first "exomoon" candidate -- a moon orbiting a planet that lies outside our solar system. Using a technique called "microlensing," they observed what could be either a moon and a planet -- or a planet and a star. This artist's conception depicts the two possibilities, with the planet/moon pairing on the top, and star/planet on the bottom. If the moon scenario is true, the moon would weigh less than Earth, and the planet would be more massive than Jupiter.

The scientists can't confirm the results partly because microlensing events happen once, due to chance encounters. The events occur when a star or planet happens to pass in front of a more distant star, causing the distant star to brighten. If the passing object has a companion -- either a planet or moon -- it will alter the brightening effect. Once the event is over, it is possible to study the passing object on its own. But the results would still not be able to distinguish between a planet/moon duo and a faint star/planet. Both pairings would be too dim to be seen.

In the future, it may be possible to enlist the help of multiple telescopes to watch a lensing event as it occurs, and confirm the presence of exomoons.

Illustration credit: NASA/JPL-Caltech

Note: For more information, see Faraway Moon or Faint Star? Possible Exomoon Found.

Friday, April 11, 2014

Abell 33


Astronomers using ESO’s Very Large Telescope in Chile have captured this eye-catching image of planetary nebula Abell 33. Created when an aging star blew off its outer layers, this beautiful blue bubble is, by chance, aligned with a foreground star, and bears an uncanny resemblance to a diamond engagement ring. This cosmic gem is unusually symmetric, appearing to be almost perfectly circular on the sky.

Photo credit: ESO

Note:
For more information, see Chance Meeting Creates Celestial Diamond Ring.

Thursday, April 10, 2014

Bright Spot in the Distance at Gale Crater


This image from the Navigation Camera (Navcam) on NASA's Curiosity Mars rover includes a bright spot near the upper left corner. The sun is in the same direction, west-northwest, above the frame. Bright spots appear in images from the rover nearly every week. Typical explanations for them are cosmic rays hitting the light detector or sunlight glinting from rocks.

The right-eye camera of the stereo Navcam recorded this frame during the afternoon of the 589th Martian day, or sol, of Curiosity's work on Mars (April 3, 2014), from the site where the rover reached a waypoint called "the Kimberley" by that sol's drive. An image taken by the Navcam's left-eye camera within one second of the same time (http://mars.jpl.nasa.gov/msl/multimedia/raw/?rawid=NLB_449790582EDR_F0310000NCAM00262M_&s=589) does not include a bright spot of this type. A pair of Navcam images in the same direction from the previous afternoon has a bright spot similarly located in the right-eye image (http://mars.jpl.nasa.gov/msl/multimedia/raw/?rawid=NRB_449700848EDR_F0301254NCAM00252M_&s=588) but not in the left-eye image (http://mars.jpl.nasa.gov/msl/multimedia/raw/?rawid=NLB_449700848EDR_F0301254NCAM00252M_&s=588).

One possible explanation for the bright spot in this image is a glint from a rock surface reflecting the sun. Another is a cosmic ray hitting the camera's light detector, a CCD (charge-coupled device). Cosmic ray patterns in Mars rover images vary from a dot to a long line depending on the angle at which the ray strikes the detector.

Photo credit: NASA/JPL-Caltech

Note: For more information, see Images From NASA Mars Rover Include Bright Spots.

Wednesday, April 9, 2014

Liftoff of Sentinel-1A


Cameras mounted on the Soyuz Fregat upper stage that sent Sentinel-1A into space on 3 April 2014 captured this footage from liftoff to separation.

The 2.3-ton satellite lifted off on a Soyuz rocket from Europe’s Spaceport in Kourou, French Guiana at 21:02 GMT (23:02 CEST). The first stage separated 118 sec later, followed by the fairing (209 sec), stage 2 (287 sec) and the upper assembly (526 sec). After a 617 sec burn, the Fregat upper stage delivered Sentinel into a Sun-synchronous orbit at 693 km altitude. The satellite separated from the upper stage 23 min 24 sec after liftoff.

Sentinel-1 is the first in the family of satellites for Europe’s Copernicus program. It carries an advanced radar to scan Earth’s surface in all weather conditions and regardless of whether it is day or night. This new mission will be used to care for many aspects of our environment, from detecting and tracking oil spills and mapping sea ice to monitoring movement in land surfaces and mapping changes in the way land is used.

Video credit: Arianespace/ESA/Roscosmos; Music written by M. Oldfield/copyright EMI Virgin

Update: A slightly longer version of the video can be found here: Onboard Cameras Show Full Launch and Separation of Sentinel-1A.

Tuesday, April 8, 2014

Titan's Dunes


The moons of our Solar System are brimming with unusual landscapes. However, sometimes they look a little more familiar, as in this new radar image from the Cassini orbiter. The image shows dark streaks carved into dunes reminiscent of those we might find on a beach on Earth, or raked with flowing lines in a Japanese Zen garden — but this scene is actually taking place on Saturn’s moon Titan.

While our sand is composed of silicates, the ‘sand’ of these alien dunes is formed from grains of organic materials about the same size as particles of our beach sand. The small size and smoothness of these grains means that the flowing lines carved into the dunes show up as dark to the human eye.

These grains are shunted around by winds shifting over the moon’s surface. These winds aren’t particularly fast — only moving at around 1 m/s — but they blow in opposing directions throughout the year, causing Titan’s ‘sand’ to pile up in certain places over time.

Titan seems to be full of features and phenomena that are quite familiar to those found on Earth. Since Cassini arrived in the Saturn system in 2004, and dropped off ESA’s Huygens probe in 2005, scientists have been studying the similarities between Titan and Earth by exploring sand dunes, channels and lakes of liquid ethane and methane scattered across its surface.

While previous images have spotted these eerily familiar patterns on Titan’s dunes, this new image shows them in greater detail. The image was obtained by Cassini’s Titan radar mapper on 10 July 2013, by a team led by Steve Wall at NASA’s Jet Propulsion Laboratory in California, USA. The horizontal seam near the center is an artifact of radar image data processing.

Image credit: NASA/JPL-Caltech

Sunday, April 6, 2014

El Gordo Galactic Cluster (ACT-CL J0102-4915)


El Gordo: A galaxy cluster nicknamed "El Gordo" about 7 billion light years from Earth.

When scientists first discovered this galaxy cluster in 2012 with Chandra and ground-based optical telescopes, they nicknamed it "El Gordo" (the "fat one" in Spanish) because of its gigantic mass. New data from Hubble suggest it may weigh 43 percent more - about 3 million billion Suns -- than the original estimate based on the X-ray data and dynamical studies. This composite image of El Gordo contains X-rays from Chandra (pink), a map of where the dark matter is found determined by gravitational lensing (blue), and the individual galaxies in the cluster and stars in the field of view as observed by Hubble.

Scale: Image is about 5 arcmin across (7.72 million light years)

Image credit: NASA, ESA, J. Jee (Univ. of California, Davis), J. Hughes (Rutgers Univ.), F. Menanteau (Rutgers Univ. & Univ. of Illinois, Urbana-Champaign), C. Sifon (Leiden Obs.), R. Mandelbum (Carnegie Mellon Univ.), L. Barrientos (Univ. Catolica de Chile), and K. Ng (Univ. of California, Davis)

Note: For more information, see El Gordo: Monster "El Gordo" Galaxy Cluster is Bigger than Thought.

Saturday, April 5, 2014

NGC 1084


In this new Hubble image, we can see an almost face-on view of the galaxy NGC 1084. At first glance, this galaxy is pretty unoriginal. Like the majority of galaxies that we observe it is a spiral galaxy, and, as with about half of all spirals, it has no bar running through its loosely wound arms. However, although it may seem unremarkable on paper, NGC 1084 is actually a near-perfect example of this type of galaxy — and Hubble has a near-perfect view of it.

NGC 1084 has hosted several violent events known as supernovae — explosions that occur when massive stars, many times more massive than the Sun, approach their twilight years. As the fusion processes in their cores run out of fuel and come to an end, these stellar giants collapse, blowing off their outer layers in a violent explosion. Supernovae can often briefly outshine an entire galaxy, before then fading away over several weeks or months. Although directly observing one of these explosions is hard to do, in galaxies like NGC 1084 astronomers can find and study the remnants left behind.

Astronomers have noted five supernova explosions within NGC 1084 over the past half century. These remnants are named after the year in which they took place — 1963P, 1996an, 1998dl, 2009H, and 2012ec.

The most recent explosion, 2012ec, was detected at the end of NGC 1084’s top right arm in August 2012. It is not visible here as these images were taken in 2001, some eleven years before this supernova exploded. Astronomers at Queen's University Belfast have managed to use these "before" images to directly identify the star that exploded. It appears to be a red supergiant some 10 to 20 times more massive than the Sun, and quite similar to the well-known star Betelguese in Orion.

Photo credit: NASA, ESA, and S. Smartt (Queen's University Belfast)

Friday, April 4, 2014

Enceladus' Ocean


This diagram illustrates the possible interior of Saturn's moon Enceladus based on a gravity investigation by NASA's Cassini spacecraft and NASA's Deep Space Network, reported in April 2014. The gravity measurements suggest an ice outer shell and a low density, rocky core with a regional water ocean sandwiched in between at high southern latitudes.

Views from Cassini's imaging science subsystem were used to depict the surface geology of Enceladus and the plume of water jets gushing from fractures near the moon's south pole.

Enceladus is 313 miles (504 kilometers) in diameter.

Illustration credit: NASA/JPL-Caltech

Note: This is the big story of the day. For more information, see Inside Enceladus, Icy Moon Enceladus Has Underground Sea, NASA Space Assets Detect Ocean inside Saturn Moon, and Deep Ocean Detected Inside Saturn's Moon.

Thursday, April 3, 2014

NGC 1316 and 1317


This new image from the MPG/ESO 2.2-meter telescope at ESO’s La Silla Observatory in Chile shows a contrasting pair of galaxies: NGC 1316, and its smaller companion NGC 1317 (right). Although NGC 1317 seems to have had a peaceful existence, its larger neighbor bears the scars of earlier mergers with other galaxies.

Image credit: ESO

Note: For more information, see Galactic Serial Killer.

Tuesday, April 1, 2014

Solar Cycle 23


It took 10 years to create this image of our changing Sun. Taken from space by the Solar and Heliospheric Observatory (SOHO), it shows a dramatically different picture than the one we receive on Earth.

From Earth’s surface, we are treated to a biased view. Every day our world is bathed in the Sun’s light and heat, and at these visible and infrared wavelengths our luminary shines to within a fraction of a percent of the same energy every day.

At ultraviolet and X-ray wavelengths, this is not true. Launched in 1995, SOHO has been continuously monitoring the Sun since then, in part to study this variation. Back in 2006, one image for each year of the mission until then was chosen and displayed in this montage.

The bright parts of these images correspond to gas in the Sun’s atmosphere at a temperature of about 2 million degrees Celsius.

Unlike visible light, the intensity of the ultraviolet radiation from the Sun varies greatly. This variation becomes more pronounced the shorter the wavelength, especially in the X-ray region of the spectrum. This is governed by solar activity, which runs in an approximately 11-year cycle. It is linked to the generation of the Sun’s magnetic field although our precise understanding of this mechanism remains elusive.

The waxing and waning of cycle-23, counted since 1755 when systematic record-taking began, can be seen clearly in this image. At its peak in 2001, the Sun was a maelstrom of activity, releasing about 10 times more ultraviolet light than at the minimum periods that can be seen in 1996 and 2006.

Now in cycle-24, the Sun is again at a peak of activity, although it is milder than that of 2001.

This image was originally published at the Solar and Heliospheric Observatory website.

Image credit: SOHO (ESA & NASA)

Saturday, March 29, 2014

Comet 67P/Churymov-Gerasimenko Near Messier 107


This is a picture of comet 67P/Churymov-Gerasimenko in the constellation Ophiuchus. The image was taken on March 21, 2014, by the narrow-angle camera of the Rosetta spacecraft's Optical, Spectroscopic and Infrared Remote Imaging System (OSIRIS). The comet is indicated by the small circle next to the bright globular star cluster M107. The image was taken from a distance of about 3 million miles (5 million kilometers).

Image credit: ESA © 2014 MPS for OSIRIS-Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

Note: For more information, see PIA17796: Rosetta Images its Target, Rosetta Sets Sights on Destination Comet, Rosetta’s First Sighting of its Target in 2014 – Narrow Angle View, and Rosetta Sets Sights on Destination Comet.

Friday, March 28, 2014

Rings Around Asteroid 10199 Chariklo


Observations at many sites in South America, including ESO’s La Silla Observatory, have made the surprise discovery that the remote asteroid Chariklo is surrounded by two dense and narrow rings. This is the smallest object by far found to have rings and only the fifth body in the Solar System — after the much larger planets Jupiter, Saturn, Uranus and Neptune — to have this feature. The origin of these rings remains a mystery, but they may be the result of a collision that created a disc of debris.

This artist’s impression shows how the rings might look from close to the surface of Chariklo.

Illustration credit: ESO/L. Calçada/Nick Risinger (skysurvey.org)

Note: For more information, see First Ring System Around Asteroid.

Update: A new video shows how the occultation of a star by Asteroid 10199 Chariklo revealed the two rings that orbit the asteroid.


Thursday, March 27, 2014

NGC 4395


The galaxy NGC 4395 is shown here in infrared light, captured by NASA's Spitzer Space Telescope. This dwarf galaxy is relatively small in comparison with our Milky Way galaxy, which is nearly 1,000 times more massive.

The galaxy is "bulgeless" because it lacks a large collection of stars at its center. Astronomers using NASA's Wide-field Infrared Survey Explorer, or WISE, have found more evidence that bulgeless galaxies, contrary to previous theories, do harbor supermassive black holes at their center. In this image, an actively feeding supermassive black hole resides in the galaxy's nucleus, as seen by the bright red source. The feeding supermassive black hole dominates the infrared light coming from the galaxy's center.

Image credit: NASA/JPL-Caltech

Note: For more information, see The Search for Seeds of Black Holes.

Tuesday, March 25, 2014

Open Cluster Berkeley 87 and Star-Forming Region ON2


Massive stars are born in tumultuous clouds of gas and dust. They lead a brief but intense life, blowing powerful winds of particles and radiation that strike their surroundings, before their explosive demise as supernovas.

The interplay between massive stars and their environment is revealed in this image of the star-forming region ON2. It combines X-ray coverage from ESA’s XMM-Newton X-ray observatory with an infrared view from NASA’s Spitzer Space Telescope.

This stellar cradle is associated with the open cluster of stars named Berkeley 87, some 4000 light-years from Earth. The cluster is home to over 2000 stars, most of which are low-mass stars like our Sun or smaller, but some – a few dozen – are stellar monsters weighing 10–80 times more.

Two glowing clouds of gas and dust – the raw material from which stars form – dominate the center of the image and are shown in red. Scattered across the image are a multitude of protostars – seeds of future stellar generations; these are shown in green. The bright yellow star in the upper part of the image is BC Cygni, a massive star that has puffed up enormously and will eventually explode as a supernova.

Shown in blue is XMM-Newton’s X-ray view of ON2: it reveals individual sources – young, massive stars as well as protostars – and more diffuse regions of X-rays. Two ‘bubbles’ of X-rays can be seen in the upper and lower clouds, respectively, pink against the red background. These two bubbles conceal the cumulative emissions from many protostars, but also light radiated by very energetic particles – a signature of shockwaves triggered by massive stars and their winds.

The image combines observations performed in the X-ray energy range of 0.25–12 keV (blue) and at infrared wavelengths of 3.6 microns (green) and 8 microns (red). It spans about 15 arcminutes on each side; north is up and east is to the left.

This image was first published in the paper “Hard X-Ray Emission in the Star-Forming Region ON 2: Discovery with XMM-Newton” by Oskinova et al. in April 2010.

Image credit: L.M. Oskinova, R.A. Gruendl, Spitzer Space Telescope, JPL, NASA & ESA

Sunday, March 23, 2014

Space Sunflower May Help Snap Pictures of Planets


A spacecraft that looks like a giant sunflower might one day be used to acquire images of Earth-like rocky planets around nearby stars. The prototype deployable structure, called a starshade, is being developed by NASA's Jet Propulsion Laboratory in Pasadena, California.

The hunt is on for planets that resemble Earth in size, composition and temperature. Rocky planets with just the right temperature for liquid water -- not too hot, not too cold -- could be possible abodes for life outside our solar system. NASA's Kepler mission has discovered hundreds of planets orbiting other stars, called exoplanets, some of which are a bit larger than Earth and lie in this comfortable "Goldilocks" zone.

Researchers generally think it's only a matter of time before we find perfect twins of Earth. The next step would be to image and characterize their spectra, or chemical signatures, which provide clear clues about whether those worlds could support life. The starshade is designed to help take those pictures of planets by blocking out the overwhelmingly bright light of their stars. Simply put, the starshade is analogous to holding your hand up to the sun to block it while taking a picture of somebody.

The proposed starshade could launch together with a telescope. Once in space, it would separate from the rocket and telescope, unfurl its petals, then move into position to block the light of stars.

Video credit: NASA/JPL

Saturday, March 22, 2014

The Milky Way in Infrared


When you look up at the Milky Way on a clear, dark night, you'll see a band of bright stars arching overhead. This is the plane of our flat spiral galaxy, within which our solar system lies.

A new, zoomable panorama from NASA's Spitzer Space Telescope shows us our galaxy's plane all the way around us in infrared light. The 360-degree mosaic comes primarily from the GLIMPSE360 project, which stands for Galactic Legacy Infrared Mid-Plane Survey Extraordinaire. It consists of more than 2 million snapshots taken in infrared light over 10 years, beginning in 2003 when Spitzer launched.

This infrared view reveals much more of the galaxy than can be seen in visible-light views. Whereas visible light is blocked by dust, infrared light from stars and other objects can travel through dust to reach Spitzer's detectors. For instance, when looking up at our night skies, we see stars that are an average of 1,000 light-years away; the rest are hidden. In Spitzer's mosaic, light from stars throughout the galaxy -- which stretches 100,000 light-years across -- shines through. This picture covers only about three percent of the sky, but includes more than half of the galaxy's stars and the majority of its star formation activity.

The red color shows dusty areas of star formation. Throughout the galaxy, tendrils, bubbles and sculpted dust structures are apparent. These are the results of massive stars blasting out winds and radiation. Stellar clusters deeply embedded in gas and dust, green jets and other features related to the formation of young stars can also be seen for the first time. Looking toward the galactic center, the blue haze is made up of starlight -- the region is too far away for us to pick out individual stars, but they contribute to the glow. Dark filaments that show up in stark contrast to the bright background are areas of thick, cold dust that not even infrared light can penetrate. If you look closely, it's even possible to spot distant galaxies that lie far beyond the Milky Way.

Scientists are using these images to get to know our galaxy better. They've come up with better maps of its central bar of stars and spiral structure, discovered new remote sites of star formation and even come across new mysteries; for example, the dust grains indicate a higher abundance of carbon in the galaxy than expected. The GLIMPSE360 map will guide astronomers for generations, helping them to further chart the unexplored territories of our own Milky Way.

The image combines data from multiple surveys in addition to GLIMPSE360: GLIMPSE, GLIMPSEII, GLIMPSE3D, Vela-Carina, Deep GLIMPSE, CYGX, GALCEN and SMOG. Twelve-micron data from NASA's Wide-field Infrared Survey Explorer (WISE) was substituted for missing 8-micron data in outer galaxy regions mapped during Spitzer's post-cryogen mission.

Zoomable, full-resolution and poster versions of the image are online at http://www.spitzer.caltech.edu/glimpse360.

Image credit: NASA/JPL-Caltech/University of Wisconsin

Note: For more information, see NASA's Spitzer Telescope Brings 360-Degree View of Galaxy to Our Fingertips.

Friday, March 21, 2014

Supernova Remnant DEM L241


DEM L241: A supernova remnant in the Large Magellanic Cloud about 160,000 light years from Earth.

This composite image contains data from Chandra (purple) that provides evidence for the survival of a companion star from the blast of a supernova explosion. Chandra’s X-rays reveal a point-like source in the supernova remnant at the location of a massive star. The data suggest that mass is being pulled away from the massive star towards a neutron star or a black hole companion. If confirmed, this would be only the third binary system containing both a massive star and a neutron star or black hole ever found in the aftermath of a supernova. This supernova remnant is found embedded in clouds of ionized hydrogen, which are shown in optical light (yellow and cyan) from the MCELS survey, along with additional optical data from the DSS (white).

Scale: Image is 24 arcmin across (1100 light years).


Image credit: X-ray: NASA/CXC/SAO/F.Seward et al; Optical: NOAO/CTIO/MCELS, DSS

Thursday, March 20, 2014

Lunar North Pole Map


Scientists, using cameras aboard NASA's Lunar Reconnaissance Orbiter (LRO), have created the largest high resolution mosaic of our moon's north polar region. The six-and-a-half feet (two-meters)-per-pixel images cover an area equal to more than one-quarter of the United States.

The images making up the mosaic were taken by the two LRO Narrow Angle Cameras, which are part of the instrument suite known as the Lunar Reconnaissance Orbiter Camera (LROC). The cameras can record a tremendous dynamic range of lit and shadowed areas.

Web viewers can zoom in and out, and pan around an area. Constructed from 10,581 pictures, the mosaic provides enough detail to see textures and subtle shading of the lunar terrain. Consistent lighting throughout the images makes it easy to compare different regions.

To view the image with zoom and pan capability, visit http://lroc.sese.asu.edu/gigapan.

Image credit: NASA/GSFC/Arizona State University

Wednesday, March 19, 2014

Cosmic Dust Survey by Herschel and SDSS


Collage of galaxies in the Herschel Reference Survey at infrared/submillimeter wavelengths by Herschel (left) and at visible wavelengths from the Sloan Digital Sky Survey (SDSS, right). The Herschel image is colored with blue representing cold dust and red representing warm dust; the SDSS image shows young stars in blue and old stars in red. Together, the observations plot young, dust-rich spiral/irregular galaxies in the top left, with giant dust-poor elliptical galaxies in the bottom right.

Image credit: ESA/Herschel/HRS-SAG2 and HeViCS Key Programmes/Sloan Digital Sky Survey/ L. Cortese (Swinburne University)

Note: For more information, see Herschel Completes Largest Survey of Cosmic Dust in Local Universe and Herschel Survey in Infrared.

Tuesday, March 18, 2014

NGC 2174, the Monkey Head Nebula


Each year the NASA/ESA Hubble Space Telescope releases a brand new image to celebrate its birthday. This year, the subject of its 24th celebratory snap is part of the Monkey Head Nebula, last viewed by Hubble in 2001, creating a stunning image released in 2011.

Otherwise known as NGC 2174, this cloud of gas and dust lies about 6400 light-years away in the constellation of Orion (The Hunter). Nebulas like this one are popular targets for Hubble – their colorful plumes of gas and fiery bright stars create ethereally beautiful pictures, such as the telescope’s 22nd and 23rd anniversary images of the Tarantula and Horsehead nebulas.

This region is filled with young stars embedded within bright wisps of cosmic gas and dust. Dark dust clouds billow outwards, framed against a background of bright blue gas. These striking hues were formed by combining several Hubble images taken through different colored filters, revealing a broad range of colors not normally visible to our eyes.

These vivid clouds are actually a violent stellar nursery packed with the ingredients needed for building stars. The recipe for cooking up new stars is quite inefficient, and most of the ingredients are wasted as the cloud of gas and dust disperses. This process is accelerated by the presence of fiercely hot young stars, which triggers high-speed winds that help to blow the gas outwards.

This image marks 24 years of Hubble since April 1990, a milestone that will be celebrated at a conference held in Rome, Italy, this week. The “Science with the Hubble Space Telescope IV” conference will highlight and celebrate the scientific breakthroughs of Hubble over the last two decades, and look to the future at the topics and key questions that will shape the field of astrophysics in the next decade.

Photo credit: NASA/ESA and the Hubble Heritage Team (STScI/AURA)

Note: For more information, see Hubble Revisits the Monkey Head Nebula for 24th Birthday Snap.

Friday, March 14, 2014

Yellow Hypergiant Star HR 5171


This artist’s impression shows the yellow hypergiant star HR 5171. This is a very rare type of star with only a dozen known in our galaxy. Its size is over 1300 times that of our Sun — one of the largest ten stars found so far. Observations with ESO’s Very Large Telescope Interferometer have shown that it is actually a double star, with the companion in contact with the main star.

Illustration credit: ESO

Note: For more information, see VLT Spots Largest Yellow Hypergiant Star.