Tokyo, Kantō, Japan
May 20, 2012
Image Credit: Itsuo Inouye/AP Photo
Jumat, 31 Maret 2017
Phoenicis Lacus region of Mars
Mars digital-image mosaic merged with color of the MC-17 quadrangle, Phoenicis Lacus region of Mars. Two of the four largest shield volcanoes on Mars are within the northwestern part, the south half of Pavonis Mons and Arsia Mons. The eastern part includes Syria and Sinai Plana. Most of the quadrangle forms the Tharsis plateau--the highest plateau on Mars; its elevation, 10 km, is twice that of the Tibetan Plateau, the highest plateau on Earth. Also in the northeastern part is Noctis Labyrinthus, a complex system of fault valleys at the west end of Valles Marineris. The south-central part is marked by the large fault system, Claritas Fossae. Latitude range -30 to 0 degrees, longitude range 90 to 135 degrees.
Image Credit: NASA/JPL/USGS
Explanation from: http://photojournal.jpl.nasa.gov/catalog/pia00177
Kepler-10b: A Scorched World
Kepler-10b is a scorched world, orbiting at a distance that's more than 20 times closer to its star than Mercury is to our own Sun. The daytime temperature's expected to be more than 2,500 degrees Fahrenheit, hotter than lava flows here on Earth. Intense radiation from the star has kept the planet from holding onto an atmosphere. Flecks of silicates and iron may be boiled off a molten surface and swept away by the stellar radiation, much like a comet's tail when its orbit brings it close to the Sun.
Image Credit: NASA/Kepler Mission/Dana Berry
Explanation from: https://www.nasa.gov/mission_pages/kepler/multimedia/images/kepler10_3.html
Lenticular Galaxy NGC 4526
This neat little galaxy is known as NGC 4526. Its dark lanes of dust and bright diffuse glow make the galaxy appear to hang like a halo in the emptiness of space in this new image from the NASA/ESA Hubble Space Telescope.
Although this image paints a picture of serenity, the galaxy is anything but. It is one of the brightest lenticular galaxies known, a category that lies somewhere between spirals and ellipticals. It has hosted two known supernova explosions, one in 1969 and another in 1994, and is known to have a colossal supermassive black hole at its centre that has the mass of 450 million Suns.
NGC 4526 is part of the Virgo cluster of galaxies. Ground-based observations of galaxies in this cluster have revealed that a quarter of these galaxies seem to have rapidly rotating discs of gas at their centres. The most spectacular of these is this galaxy, NGC 4526, whose spinning disc of gas, dust, and stars reaches out uniquely far from its heart, spanning some 7% of the galaxy's entire radius.
This disc is moving incredibly fast, spinning at more than 250 kilometres per second. The dynamics of this quickly whirling region were actually used to infer the mass of NGC 4526’s central black hole — a technique that had not been used before to constrain a galaxy’s central black hole.
This image was taken using Hubble’s Wide Field Planetary Camera 2.
Image Credit: ESA/Hubble & NASA, Judy Schmidt
Explanation from: https://www.spacetelescope.org/images/potw1442a/
The Lagoon Nebula
Like a Dali masterpiece, this image of Messier 8 from the NASA/ESA Hubble Space Telescope is both intensely colourful and distinctly surreal. Located in the constellation of Sagittarius (The Archer), this giant cloud of glowing interstellar gas is a stellar nursery that is also known as the Lagoon Nebula.
Although the name definitely suits the beauty of this object, “lagoon” does suggest tranquillity and there is nothing placid about the high-energy radiation causing these intricate clouds to glow. The massive stars hiding within the heart of the nebula give off enormous amounts of ultraviolet radiation, ionising the gas and causing it to shine colourfully, as well as sculpting the surrounding nebula into strange shapes. The result is an object around four to five thousand light-years away which, on a clear night, is faintly visible to the naked eye.
Since it was first recorded back in the 1747 this object has been photographed and analysed at many different wavelengths. By using infrared detectors it is possible to delve into the centre of these dusty regions to study the objects within. However, while this optical image, taken with the Advanced Camera for Surveys (ACS) on the Hubble Space Telescope, cannot pierce the obscuring matter it is undoubtedly one of the most visually impressive.
Messier 8 is an enormous structure — around 140 by 60 light-years in extent — to put this in perspective the orbit of Neptune stretches only about four light-hours from our own Sun.
This picture was created from exposures taken with the Wide Field Channel of the Advanced Camera for Surveys on Hubble. Light from glowing hydrogen (through the F658N filter) is coloured red. Light from ionised nitrogen (through the F660N filter) is coloured green and light through a yellow filter (F550M) is coloured blue. The exposure times through each filter are 1560 s, 1600 s and 400 s respectively. The blue-white flare at the lower left of the image is scattered light from a bright star just outside the field of view. The field of view is about 3.3 by 1.7 arcminutes.
Image Credit: ESA/Hubble & NASA
Explanation from: https://www.spacetelescope.org/images/potw1120a/
Kamis, 30 Maret 2017
NGC 4424 & LEDA 213994 Galaxies
Some astronomical objects have endearing or quirky nicknames, inspired by mythology or their own appearance. Take, for example, the constellation of Orion (The Hunter), the Sombrero Galaxy, the Horsehead Nebula, or even the Milky Way. However, the vast majority of cosmic objects appear in astronomical catalogues, and are given rather less poetic names based on the order of their discovery.
Two galaxies are clearly visible in this Hubble image, the larger of which is NGC 4424. This galaxy is catalogued in the New General Catalogue of Nebulae and lusters of Stars (NGC), which was compiled in 1888. The NGC is one of the largest astronomical catalogues, which is why so many Hubble Pictures of the Week feature NGC objects. In total there are 7840 entries in the catalogue and they are also generally the larger, brighter, and more eye-catching objects in the night sky, and hence the ones more easily spotted by early stargazers.
The smaller, flatter, bright galaxy sitting just below NGC 4424 is named LEDA 213994. The Lyon-Meudon Extragalactic Database (LEDA) is far more modern than the NGC. Created in 1983 at the Lyon Observatory it contains millions of objects. However, many NGC objects still go by their initial names simply because they were christened within the NGC first. No astronomer can resist a good acronym, and “LEDA” is more appealing than “the LMED”, perhaps thanks to the old astronomical affinity with mythology when it comes to naming things: Leda was a princess in Ancient Greek mythology.
Image Credit: ESA/Hubble & NASA
Explanation from: https://www.spacetelescope.org/images/potw1713a/
Extreme Planets
This artist's concept depicts the pulsar planet system discovered in 1992 using the Arecibo radio telescope in Puerto Rico. Three pulsar planets - the first of any kind ever found outside our Solar System - circling a pulsar called PSR B1257+12. Pulsars are rapidly rotating neutron stars, which are the collapsed cores of exploded massive stars. They spin and pulse with radiation, much like a lighthouse beacon. Here, the pulsar's twisted magnetic fields are highlighted by the blue glow.
All three pulsar planets are shown in this picture; the farthest two from the pulsar (closest in this view) are about the size of Earth. Radiation from charged pulsar particles would probably rain down on the planets, causing their night skies to light up with auroras similar to our Northern Lights. One such aurora is illustrated on the planet at the bottom of the picture.
Since this landmark discovery, more than 160 extrasolar planets have been observed around stars that are burning nuclear fuel. These planets are still the only ones around a dead star. They also might be part of a second generation of planets, the first having been destroyed when their star blew up. The Spitzer Space Telescope's discovery of a dusty disk around a pulsar might represent the beginnings of a similarly "reborn" planetary system.
Image Credit: NASA/JPL-Caltech
Explanation from: http://photojournal.jpl.nasa.gov/catalog/PIA08042
The south pole of Jupiter
This enhanced-color image of Jupiter's south pole and its swirling atmosphere was created by citizen scientist Roman Tkachenko using data from the JunoCam imager on NASA's Juno spacecraft.
Juno acquired the image, looking directly at the Jovian south pole, on February 2, 2017, at 6:06 a.m. PST (9:06 a.m. EST) from an altitude of about 63,400 miles (102,100 kilometers) above Jupiter's cloud tops. Cyclones swirl around the south pole, and white oval storms can be seen near the limb -- the apparent edge of the planet.
Image Credit: NASA/JPL-Caltech/SwRI/MSSS/Roman Tkachenko
Explanation from: http://photojournal.jpl.nasa.gov/catalog/PIA21381
Rabu, 29 Maret 2017
Cyclone Debbie
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| On March 28 at 03:42 UTC (1:42 p.m. AEST Queensland local time /Mar. 27 at 11:42 p.m. EST) NASA-NOAA's Suomi NPP satellite captured this visible image of Tropical Cyclone Debbie over eastern Australia. |
Before Debbie made landfall, NASA's Aqua satellite analyzed the temperatures in the storm on Mar. 27 at 0347 UTC (Mar. 26 at 11:47 pm. EST). The infrared imagery showed a large area of cloud top temperatures in thunderstorms around Debbie's eye as cold as near minus 63.1 degrees Celsius or minus 81.6 degrees Fahrenheit. Cloud top temperatures that cold have been shown to produce heavy rainfall.
Cyclone Debbie made landfall north of Proserpine at Airlie Beach on March 28, shortly after noon AEST/Queensland local time (0200 UTC/March 27 at 10 p.m. EST). The Australian Bureau of Meteorology noted wind gusts stronger than 160 mph (260 kph) were recorded near landfall.
The strong winds downed trees and powerlines. Power losses occurred in a large area between the towns of Bowen and Mackay, according to Ergon Energy. The Townsville airport and ocean ports were closed.
Shortly after Debbie's 30-mile-wide (50 km) eye made landfall, the VIIRS instrument aboard NASA-NOAA's Suomi NPP satellite captured a visible image of the storm at 03:42 UTC (1:42 p.m. AEST Queensland local time /Mar. 27 at 11:42 p.m. EST). The image showed a thick band of powerful thunderstorms wrapped around the cloud-filled eye.
At 11:58 p.m. AEST/Queensland local time (9:58 a.m. EST/U.S.), the Australian Bureau of Meteorology (ABM) noted that the Warning Zone extended from Bowen to St Lawrence, including Mackay and the Whitsunday Islands, and extending inland to Mount Coolon and Moranbah.
At that time, ABM noted that maximum sustained winds near Debbie's center were near 52.8 mph (85 kph) with higher gusts. Debbie was centered near 20.8 degrees south latitude and 147.5 degrees east longitude, about 71.4 miles (115 kilometers) west southwest of Proserpine and 24.8 miles (40 kilometers) southwest of Collinsville. Debbie continued to move inland in a west-southwesterly direction at (9.3 mph) 15 kph.
ABM noted "Tropical cyclone Debbie is expected to weaken further to a tropical low during the next few hours. During the day today, this remnant low will curve from the current southwesterly motion to a more southerly track over inland Queensland.
Although the peak winds near Debbie's center are weakening rapidly tonight, heavy rainfall is expected to continue across the region for the next 12 to 24 hours, gradually contracting southwards with the system."
Image Credit: NASA/NOAA
Explanation from: https://www.nasa.gov/feature/goddard/2017/91p-southern-pacific-ocean
Stars Born in Winds from Supermassive Black Holes
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| Artist’s impression of a galaxy forming stars within powerful outflows of material blasted out from supermassive black holes at its core. Results from ESO’s Very Large Telescope are the first confirmed observations of stars forming in this kind of extreme environment. The discovery has many consequences for understanding galaxy properties and evolution. |
Observations using ESO’s Very Large Telescope have revealed stars forming within powerful outflows of material blasted out from supermassive black holes at the cores of galaxies. These are the first confirmed observations of stars forming in this kind of extreme environment. The discovery has many consequences for understanding galaxy properties and evolution. The results are published in the journal Nature.
A UK-led group of European astronomers used the MUSE and X-shooter instruments on the Very Large Telescope (VLT) at ESO’s Paranal Observatory in Chile to study an ongoing collision between two galaxies, known collectively as IRAS F23128-5919, that lie around 600 million light-years from Earth. The group observed the colossal winds of material — or outflows — that originate near the supermassive black hole at the heart of the pair’s southern galaxy, and have found the first clear evidence that stars are being born within them.
Such galactic outflows are driven by the huge energy output from the active and turbulent centres of galaxies. Supermassive black holes lurk in the cores of most galaxies, and when they gobble up matter they also heat the surrounding gas and expel it from the host galaxy in powerful, dense winds.
“Astronomers have thought for a while that conditions within these outflows could be right for star formation, but no one has seen it actually happening as it’s a very difficult observation,” comments team leader Roberto Maiolino from the University of Cambridge. “Our results are exciting because they show unambiguously that stars are being created inside these outflows.”
The group set out to study stars in the outflow directly, as well as the gas that surrounds them. By using two of the world-leading VLT spectroscopic instruments, MUSE and X-shooter, they could carry out a very detailed study of the properties of the emitted light to determine its source.
Radiation from young stars is known to cause nearby gas clouds to glow in a particular way. The extreme sensitivity of X-shooter allowed the team to rule out other possible causes of this illumination, including gas shocks or the active nucleus of the galaxy.
The group then made an unmistakable direct detection of an infant stellar population in the outflow. These stars are thought to be less than a few tens of millions of years old, and preliminary analysis suggests that they are hotter and brighter than stars formed in less extreme environments such as the galactic disc.
As further evidence, the astronomers also determined the motion and velocity of these stars. The light from most of the region’s stars indicates that they are travelling at very large velocities away from the galaxy centre — as would make sense for objects caught in a stream of fast-moving material.
Co-author Helen Russell (Institute of Astronomy, Cambridge, UK) expands: “The stars that form in the wind close to the galaxy centre might slow down and even start heading back inwards, but the stars that form further out in the flow experience less deceleration and can even fly off out of the galaxy altogether.”
The discovery provides new and exciting information that could better our understanding of some astrophysics, including how certain galaxies obtain their shapes; how intergalactic space becomes enriched with heavy elements; and even from where unexplained cosmic infrared background radiation may arise.
Maiolino is excited for the future: “If star formation is really occurring in most galactic outflows, as some theories predict, then this would provide a completely new scenario for our understanding of galaxy evolution.”
Image Credit: ESO/M. Kornmesser
Explanation from: https://www.eso.org/public/news/eso1710/
Milky Way Galaxy seen over VLT’s four 8.2-metre Unit Telescopes
ESO's Very Large Telescope (VLT) looks more like a very small telescope in this image! From this perspective, it is difficult to make out the silhouettes of the VLT’s four 8.2-metre Unit Telescopes, which sit atop Cerro Paranal in the Chilean Atacama Desert.
The VLT’s location was very carefully selected. It is vital for the site to be as dry as possible, as water vapour can absorb infrared light and degrade observations. In order to reduce the effects of Earth’s atmosphere as far as possible, the VLT is at 2600 metres above sea level, minimising the amount of atmosphere sitting between it and the stars.
Due to its remote location, Paranal manages to be mostly undisturbed and light-free. Even the winding roads that lead through the Atacama Desert to the observation site are dimly lit to avoid unnecessary light pollution.
In this image, a trail of stars cuts across the the night sky like smoke rising from a celestial chimney. This is our home galaxy, the Milky Way. Towards the top of the image you can see a brighter and wider section — this is the star-filled galactic bulge, which sits at the heart of the Milky Way.
Image Credit: ESO/B. Tafreshi
Explanation from: https://www.eso.org/public/images/potw1713a/
Was 49 Galaxy Merger
A supermassive black hole inside a tiny galaxy is challenging scientists' ideas about what happens when two galaxies become one.
Was 49 is the name of a system consisting of a large disk galaxy, referred to as Was 49a, merging with a much smaller "dwarf" galaxy called Was 49b. The dwarf galaxy rotates within the larger galaxy's disk, about 26,000 light-years from its center. Thanks to NASA's Nuclear Spectroscopic Telescope Array (NuSTAR) mission, scientists have discovered that the dwarf galaxy is so luminous in high-energy X-rays, it must host a supermassive black hole much larger and more powerful than expected.
"This is a completely unique system and runs contrary to what we understand of galaxy mergers," said Nathan Secrest, lead author of the study and postdoctoral fellow at the U.S. Naval Research Laboratory in Washington.
Data from NuSTAR and the Sloan Digital Sky Survey suggest that the mass of the dwarf galaxy's black hole is huge, compared to similarly sized galaxies, at more than 2 percent of the galaxy's own mass.
"We didn't think that dwarf galaxies hosted supermassive black holes this big," Secrest said. "This black hole could be hundreds of times more massive than what we would expect for a galaxy of this size, depending on how the galaxy evolved in relation to other galaxies.”
The dwarf galaxy's black hole is the engine of an active galactic nucleus (AGN), a cosmic phenomenon in which extremely high-energy radiation bursts forth as a black hole devours gas and dust. This particular AGN appears to be covered by a donut-shaped structure made of gas and dust. NASA's Chandra and Swift missions were used to further characterize the X-ray emission.
Normally, when two galaxies start to merge, the larger galaxy's central black hole becomes active, voraciously gobbling gas and dust, and spewing out high-energy X-rays as matter gets converted into energy. That is because, as galaxies approach each other, their gravitational interactions create a torque that funnels gas into the larger galaxy's central black hole. But in this case, the smaller galaxy hosts a more luminous AGN with a more active supermassive black hole, and the larger galaxy's central black hole is relatively quiet.
An optical image of the Was 49 system, compiled using observations from the Discovery Channel Telescope in Happy Jack, Arizona, uses the same color filters as the Sloan Digital Sky Survey. Since Was 49 is so far away, these colors are optimized to separate highly-ionized gas emission, such as the pink-colored region around the feeding supermassive black hole, from normal starlight, shown in green. This allowed astronomers to more accurately determine the size of the dwarf galaxy that hosts the supermassive black hole.
The pink-colored emission stands out in a new image because of the intense ionizing radiation emanating from the powerful AGN. Buried within this region of intense ionization is a faint collection of stars, believed to be part of the galaxy surrounding the enormous black hole. These striking features lie on the outskirts of the much larger spiral galaxy Was 49a, which appears greenish in the image due to the distance to the galaxy and the optical filters used.
Scientists are still trying to figure out why the supermassive black hole of dwarf galaxy Was 49b is so big. It may have already been large before the merger began, or it may have grown during the very early phase of the merger.
"This study is important because it may give new insight into how supermassive black holes form and grow in such systems," Secrest said. “By examining systems like this, we may find clues as to how our own galaxy’s supermassive black hole formed.”
In several hundred million years, the black holes of the large and small galaxies will merge into one enormous beast.
Image Credit: DCT/NRL
Explanation from: https://www.nasa.gov/feature/jpl/nustar-probes-puzzling-galaxy-merger
CoRoT-2a: Star Blasts Planet With X-rays
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| This artist's representation shows the CoRoT-2 system, which is found about 880 light years from Earth. The system, which is estimated to be between 100 and 300 million years old, contains a star and a planet in close orbit around it. The separation between the star and the planet is only three percent of the distance between the Earth and the Sun, causing some exotic effects not seen in our solar system. The illustration shows the material, in blue, being stripped off the planet as X-rays from the star pummel the planet. |
- A star is blasting a planet in its orbit with an extremely high level of X-rays.
- This high-energy radiation is eroding the planet at a rate of 5 million tons of material per second.
- The planet, in turn, may be speeding up the star's rotation, which keeps the star's magnetic fields very active.
This graphic contains an image and illustration of a nearby star, named CoRoT-2a, which has a planet in close orbit around it. The separation between the star and planet is only about 3 percent of the distance between the Earth and the Sun, causing some exotic effects not seen in our solar system.
The planet-hosting star is located in the center of the image. Data from NASA's Chandra X-ray Observatory are shown in purple, along with optical and infrared data from the Panchromatic Robotic Optical Monitoring and Polarimetry Telescopes (PROMPT) and the Two Micron All Sky Survey (2MASS). CoRoT-2a is surrounded by a purple glow showing that it is an X-ray source.
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| A nearby star is pummeling a companion planet with a barrage of X-rays a hundred thousand times more intense than the Earth receives from the Sun. New data from NASA's Chandra X-ray Observatory and the European Southern Observatory's Very Large Telescope suggest that high-energy radiation is evaporating about 5 million tons of matter from the planet every second. This result gives insight into the difficult survival path for some planets. This sequence shows images of a nearby star named CoRoT-2a. The composite image contains X-rays from Chandra (purple) of CoRoT-2a along with optical and infrared data of the field of view in which the star is found. Not seen in these images -- but still detectable in the data -- is a planet known as CoRoT-2b in an extremely close orbit around the star. The Chandra data indicate that the planet is being blasted by X-rays with such intensity that some 5 million tons of material are being eroded from CoRoT-2a every second. |
This star is pummeling its companion planet -- not visible in this image -- with a barrage of X-rays a hundred thousand times more intense than the Earth receives from the Sun. Data from Chandra suggest that high-energy radiation from CoRoT-2a is evaporating about 5 million tons of matter from the nearby planet every second, giving insight into the difficult survival path for some planets. The artist's representation shows the material, in blue, being stripped off the planet.
The Chandra observations provide evidence that CoRoT-2a is a very active star, with bright X-ray emission produced by powerful, turbulent magnetic fields. This magnetic activity is represented by the prominences and eruptions on the surface of the star in the illustration.
Such strong activity is usually found in much younger stars and may be caused by the proximity of the planet. The planet may be speeding up the star's rotation, causing its magnetic fields to remain active longer than expected. Support for this idea comes from observations of a likely companion star to CoRoT-2a that orbits at a distance about a thousand times greater than the distance between the Earth and the Sun. This star is visible in the image as the faint, nearby star located below and to the right of CoRoT-2a. It is also shown as the bright background star in the illustration. This star is not detected in X-rays, perhaps because it does not have a close-in planet like CoRoT-2b to cause it to stay active.
The planet, CoRoT-2b, was discovered by the French Space Agency's Convection, Rotation and planetary Transits (CoRoT) satellite in 2008. It is located about 880 light years from Earth and has a mass about 3 time that of Jupiter.
Image Credit: X-ray: NASA/CXC/Univ of Hamburg/S.Schröter et al; Optical: NASA/NSF/IPAC-Caltech/UMass/2MASS, UNC/CTIO/PROMPT; Illustration: NASA/CXC/M.Weiss
Explanation from: http://chandra.harvard.edu/photo/2011/corot/
Jumat, 24 Maret 2017
Spiral Galaxy Messier 96
Not all spiral galaxies have to be picture-perfect to be striking. Messier 96, also known as NGC 3368, is a case in point: its core is displaced from the centre, its gas and dust are distributed asymmetrically and its spiral arms are ill-defined. But this portrait, taken with the FORS1 instrument on ESO’s Very Large Telescope, shows that imperfection is beauty in Messier 96. The galaxy's core is compact but glowing, and the dark dust lanes around it move in a delicate swirl towards the nucleus. And the spiral arms, patchy rings of young blue stars, are like necklaces of blue pearls.
Messier 96 lies in the constellation of Leo (The Lion). It is the largest galaxy in the Leo I group of galaxies; including its outermost spiral arms, it spans some 100 000 light-years in diameter — about the size of our Milky Way. Its graceful imperfections likely result from the gravitational pull of other members in the group, or are perhaps due to past galactic encounters.
A multitude of background galaxies peers through the dusty spiral. Perhaps the most striking of these objects is an edge-on galaxy that — because of a chance alignment — appears to interrupt the outermost spiral arm to the upper left of Messier 96's core.
The image was made with data taken at visible and infrared wavelengths through B, V, and I filters.
Image Credit: ESO/Oleg Maliy
Explanation from: https://www.eso.org/public/images/potw1143a/
Hubble detects supermassive black hole kicked out of galactic core
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| The galaxy 3C186, located about 8 billion years from Earth, is most likely the result of a merger of two galaxies. This is supported by arc-shaped tidal tails, usually produced by a gravitational tug between two colliding galaxies, identified by the scientists. The merger of the galaxies also led to a merger of the two supermassive black holes in their centres, and the resultant black hole was then kicked out of its parent galaxy by the gravitational waves created by the merger. The bright, star-like looking quasar can be seen in the centre of the image. Its former host galaxy is the faint, extended object behind it. |
An international team of astronomers using the NASA/ESA Hubble Space Telescope have uncovered a supermassive black hole that has been propelled out of the centre of the distant galaxy 3C186. The black hole was most likely ejected by the power of gravitational waves. This is the first time that astronomers found a supermassive black hole at such a large distance from its host galaxy centre.
Though several other suspected runaway black holes have been seen elsewhere, none has so far been confirmed. Now astronomers using the NASA/ESA Hubble Space Telescope have detected a supermassive black hole, with a mass of one billion times the Sun’s, being kicked out of its parent galaxy. “We estimate that it took the equivalent energy of 100 million supernovae exploding simultaneously to jettison the black hole,” describes Stefano Bianchi, co-author of the study, from the Roma Tre University, Italy.
The images taken by Hubble provided the first clue that the galaxy, named 3C186, was unusual. The images of the galaxy, located 8 billion light-years away, revealed a bright quasar, the energetic signature of an active black hole, located far from the galactic core. “Black holes reside in the centres of galaxies, so it’s unusual to see a quasar not in the centre,” recalls team leader Marco Chiaberge, ESA-AURA researcher at the Space Telescope Science Institute, USA.
The team calculated that the black hole has already travelled about 35 000 light-years from the centre, which is more than the distance between the Sun and the centre of the Milky Way. And it continues its flight at a speed of 7.5 million kilometres per hour. At this speed the black hole could travel from Earth to the Moon in three minutes.
Although other scenarios to explain the observations cannot be excluded, the most plausible source of the propulsive energy is that this supermassive black hole was given a kick by gravitational waves unleashed by the merger of two massive black holes at the centre of its host galaxy. This theory is supported by arc-shaped tidal tails identified by the scientists, produced by a gravitational tug between two colliding galaxies.
According to the theory presented by the scientists, 1-2 billion years ago two galaxies — each with central, massive black holes — merged. The black holes whirled around each other at the centre of the newly-formed elliptical galaxy, creating gravitational waves that were flung out like water from a lawn sprinkler. As the two black holes did not have the same mass and rotation rate, they emitted gravitational waves more strongly along one direction. When the two black holes finally merged, the anisotropic emission of gravitational waves generated a kick that shot the resulting black hole out of the galactic centre.
“If our theory is correct, the observations provide strong evidence that supermassive black holes can actually merge,” explains Stefano Bianchi on the importance of the discovery. “There is already evidence of black hole collisions for stellar-mass black holes, but the process regulating supermassive black holes is more complex and not yet completely understood.”
The researchers are lucky to have caught this unique event because not every black hole merger produces imbalanced gravitational waves that propel a black hole out of the galaxy. The team now wants to secure further observation time with Hubble, in combination with the Atacama Large Millimeter/submillimeter Array (ALMA) and other facilities, to more accurately measure the speed of the black hole and its surrounding gas disc, which may yield further insights into the nature of this rare object.
Image Credit: NASA, ESA, and M. Chiaberge (STScI/ESA)
Explanation from: https://www.spacetelescope.org/news/heic1706/
Spotless Sun
The Sun has been virtually spotless, as in no sunspots, over the past 11 days, a spotless stretch that we have not seen since the last solar minimum many years ago. The videos shows the past four days (March 14-17, 2017) with a combination of an extreme ultraviolet image blended with just the filtered Sun. If we just showed the filtered Sun with no spots for reference points, any viewer would have a hard time telling that the Sun was even rotating. The Sun is trending again towards the solar minimum period of its 11 year cycle, which is predicted to be around 2020.
Image Credit: NASA/GSFC/Solar Dynamics Observatory
Explanation from: http://photojournal.jpl.nasa.gov/catalog/PIA21569
Supernova Remnant N103B
This image, taken with the NASA/ESA Hubble Space Telescope, shows the supernova remnant SNR 0509-68.7, also known as N103B. N103B was a Type Ia supernova, located in the Large Magellanic Cloud — a neighbouring galaxy of the Milky Way. Owing to its relative proximity to Earth, astronomers observe the remnant to search for a potential stellar survivor of the explosion. This could shed more light on the exact mechanism behind type Ia supernovae.
The actual supernova remnant is the irregular shaped dust cloud, close to the centre of the image.
The gas in the lower half of the image and the dense concentration of stars in the lower left are the outskirts of the star cluster NGC 1850, which has been observed by Hubble in the past.
Image Credit: ESA/Hubble, NASA
Explanation from: https://www.spacetelescope.org/images/heic17xx-n103ba/
Rabu, 22 Maret 2017
Adansonia Grandidieri
Adansonia grandidieri, sometimes known as Grandidier's baobab, is the biggest and most famous of Madagascar's six species of baobabs. This imposing and unusual tree is endemic to the island of Madagascar, where it is an endangered species threatened by the encroachment of agricultural land.
Grandidier's baobabs have massive cylindrical trunks, up to three meters across, covered with smooth, reddish-grey bark. They can reach 25 to 30 m (82 to 98 ft) in height. At certain times of the year the flat-topped crowns bear bluish-green palmate leaves, dark brown floral buds or spectacular flowers with white petals. The large, dry fruits of the baobab contain kidney-shaped seeds within an edible pulp.
This baobab occurs in south-western Madagascar between Lac Ihotry (near Morombe) and Bereboka. Grandidier's baobab used to inhabit dry, deciduous forest, especially near seasonal rivers or lakes. However, today it is mainly found in open, agricultural land or degraded scrubland.
The long-lived Grandidier's baobab is in leaf from October to May, and flowers between May and August. The flowers, said to smell of sour watermelon, open just before or soon after dusk, and all the pollen is released during the first night. The tree is pollinated by nocturnal mammals, such as fork-marked lemurs and insects like the Hawk Moth. The lemurs move through the canopies, inserting their snouts into the white flowers and licking nectar from the petal bases, resulting in pollen being deposited in the lemurs' faces, whereas the moth is slightly more effective at pollination because it is able to fly from tree to tree with most of its body covered in pollen.
The species bears ripe fruit in November and December. Unlike the baobabs of Africa and Australia, it appears that the seeds of the tasty fruit are not dispersed by animals. Lemurs are the only living animals on Madagascar that are capable of acting as seed dispersers, yet seed dispersal by lemurs has never been documented. In the past, however, this could have been very different. There are several species that have gone extinct since human colonization of the island (1,500 to 2,000 years ago) that could very likely have been dispersers of the seeds. This includes species of primates that were thought to be similar to baboons, and the heaviest bird that ever lived, the elephant bird, which had a powerful beak that could have opened large fruit. Today, water may be the means by which the seeds are dispersed.
Lack of water can sometimes be a problem for plants in Madagascar. It appears that the baobab overcomes this by storing water within the fibrous wood of the trunk, as the tree's diameter fluctuates with rainfall.
Explanation from: https://en.wikipedia.org/wiki/Adansonia_grandidieri
Ceres' Shadowed Craters Over Time
This animation shows how the illumination of Ceres' northern hemisphere varies with the dwarf planet's axial tilt, or obliquity.
In the first frame the northern hemisphere is shown when Ceres' obliquity is 2 degrees, which is the minimum tilt. Regions that remain in shadow are shown in blue. The illumination shown is for the northern solstice, which is when the north pole is most illuminated.
The second frame shows the same scene when Ceres' obliquity is 12 degrees. More polar regions are illuminated (this view is also for the northern solstice). The area of the regions that remain in shadow, marked with blue dots, is much smaller.
The third frame shows the same scene when Ceres' obliquity is 20 degrees, which is the maximum tilt. The red circles show the only two craters in this scene that still have permanently shadowed regions. The polar regions are much better illuminated at this high obliquity.
Image Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
Explanation from: http://photojournal.jpl.nasa.gov/catalog/PIA21469
Mars Volcano, Earth’s Dinosaurs Went Extinct About the Same Time
New NASA research reveals that the giant Martian shield volcano Arsia Mons produced one new lava flow at its summit every 1 to 3 million years during the final peak of activity. The last volcanic activity there ceased about 50 million years ago—around the time of Earth’s Cretaceous–Paleogene extinction, when large numbers of our planet’s plant and animal species (including dinosaurs) went extinct.
Located just south of Mars’ equator, Arsia Mons is the southernmost member of a trio of broad, gently sloping shield volcanoes collectively known as Tharsis Montes. Arsia Mons was built up over billions of years, though the details of its lifecycle are still being worked out. The most recent volcanic activity is thought to have taken place in the caldera—the bowl-shaped depression at the top—where 29 volcanic vents have been identified. Until now, it’s been difficult to make a precise estimate of when this volcanic field was active.
“We estimate that the peak activity for the volcanic field at the summit of Arsia Mons probably occurred approximately 150 million years ago—the late Jurassic period on Earth—and then died out around the same time as Earth’s dinosaurs,” said Jacob Richardson, a postdoctoral researcher at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “It’s possible, though, that the last volcanic vent or two might have been active in the past 50 million years, which is very recent in geological terms.”
Measuring about 68 miles (110 kilometers) across, the caldera is deep enough to hold the entire volume of water in Lake Huron, and then some. Examining the volcanic features within the caldera required high-resolution imaging, which the researchers obtained from the Context Camera on NASA’s Mars Reconnaissance Orbiter.
The team mapped the boundaries of the lava flows from each of the 29 volcanic vents and determined the stratigraphy, or layering, of the flows. The researchers also performed a technique called crater counting—tallying up the number of craters at least 330 feet (100 meters) in diameter—to estimate the ages of the flows.
Using a new computer model developed by Richardson and his colleagues at the University of South Florida, the two types of information were combined to determine the volcanic equivalent of a batting lineup for Arsia Mons’ 29 vents. The oldest flows date back about 200 million years. The youngest flows probably occurred 10 to 90 million years ago—most likely around 50 million years ago.
The modeling also yielded estimates of the volume flux for each lava flow. At their peak about 150 million years ago, the vents in the Arsia Mons’ caldera probably collectively produced about 1 to 8 cubic kilometers of magma every million years, slowly adding to the volcano’s size.
“Think of it like a slow, leaky faucet of magma,” said Richardson. “Arsia Mons was creating about one volcanic vent every 1 to 3 million years at the peak, compared to one every 10,000 years or so in similar regions on Earth.”
A better understanding of when volcanic activity on Mars took place is important because it helps researchers understand the Red Planet’s history and interior structure.
“A major goal of the Mars volcanology community is to understand the anatomy and lifecycle of the planet’s volcanoes. Mars’ volcanoes show evidence for activity over a larger time span than those on Earth, but their histories of magma production might be quite different,” said Jacob Bleacher, a planetary geologist at Goddard and a co-author on the study. “This study gives us another clue about how activity at Arsia Mons tailed off and the huge volcano became quiet.”
Image Credit: NASA/JPL/USGS
Explanation from: https://www.nasa.gov/feature/goddard/2017/mars-volcano-earths-dinosaurs-went-extinct-about-the-same-time
Selasa, 21 Maret 2017
Interacting Galaxies NGC 3447
Some galaxies are harder to classify than others. Here, Hubble’s trusty Wide Field Camera 3 (WFC3) has captured a striking view of two interacting galaxies located some 60 million light-years away in the constellation of Leo (The Lion). The more diffuse and patchy blue glow covering the right side of the frame is known as NGC 3447 — sometimes NGC 3447B for clarity, as the name NGC 3447 can apply to the overall duo. The smaller clump to the upper left is known as NGC 3447A.
The trouble with space is that it is, to state the obvious, really, really big. Astronomers have for hundreds of years been discovering and naming galaxies, stars, cosmic clouds and more. Unifying and regulating the conventions and classifications for everything ever observed is very difficult, especially when you get an ambiguous object like NGC 3447, which stubbornly defies easy categorisation.
Overall, we know NGC 3447 comprises a couple of interacting galaxies, but we’re unsure what each looked like before they began to tear one another apart. The two sit so close that they are strongly influenced and distorted by the gravitational forces between them, causing the galaxies to twist themselves into the unusual and unique shapes seen here. NGC 3447A appears to display the remnants of a central bar structure and some disrupted spiral arms, both properties characteristic of certain spiral galaxies. Some identify NGC 3447B as a former spiral galaxy, while others categorise it as being an irregular galaxy.
Image Credit: ESA/Hubble & NASA
Explanation from: https://www.spacetelescope.org/images/potw1712a/
Protostar blazes and reshapes its stellar nursery
This image, taken by the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, shows glowing dust inside the protocluster NGC 6334I. Studying this star-forming cloud in the Cat’s Paw Nebula (NGC 6334) with both ALMA and the Submillimeter Array (SMA) in Hawaii astronomers could see that something dramatic had taken place, completely changing a stellar nursery over a surprisingly short period of time.
It is known that young stars form inside protoclusters when pockets of gas become so dense that they begin to collapse under their own gravity. Over time, discs of dust and gas form around these nascent stars and funnel material onto their surfaces helping them grow.
However, this new image from ALMA shows a massive protostar, nestled deep within this dust-filled stellar nursery, that is undergoing an intense growth spurt, most likely triggered by an avalanche of gas falling onto its surface. This new material feeding it is causing the protostar to shine nearly 100 times brighter than before.The discovery of this outburst supports the theory that young stars can undergo intense growth spurts that reshape their surroundings.
Image Credit: ALMA (ESO/NAOJ/NRAO); C. Brogan, B. Saxton (NRAO/AUI/NSF)
Explanation from: https://www.eso.org/public/images/potw1712a/
NASA's Swift Mission Maps a Star's 'Death Spiral' into a Black Hole
 |
| This artist’s rendering shows the tidal disruption event named ASASSN-14li, where a star wandering too close to a 3-million-solar-mass black hole was torn apart. The debris gathered into an accretion disk around the black hole. New data from NASA's Swift satellite show that the initial formation of the disk was shaped by interactions among incoming and outgoing streams of tidal debris. |
Some 290 million years ago, a star much like the sun wandered too close to the central black hole of its galaxy. Intense tides tore the star apart, which produced an eruption of optical, ultraviolet and X-ray light that first reached Earth in 2014. Now, a team of scientists using observations from NASA's Swift satellite have mapped out how and where these different wavelengths were produced in the event, named ASASSN-14li, as the shattered star's debris circled the black hole.
"We discovered brightness changes in X-rays that occurred about a month after similar changes were observed in visible and UV light," said Dheeraj Pasham, an astrophysicist at the Massachusetts Institute of Technology (MIT) in Cambridge, Massachusetts, and the lead researcher of the study. "We think this means the optical and UV emission arose far from the black hole, where elliptical streams of orbiting matter crashed into each other."
Astronomers think ASASSN-14li was produced when a sun-like star wandered too close to a 3-million-solar-mass black hole similar to the one at the center of our own galaxy. For comparison, the event horizon of a black hole like this is about 13 times bigger than the sun, and the accretion disk formed by the disrupted star could extend to more than twice Earth's distance from the sun.
When a star passes too close to a black hole with 10,000 or more times the sun's mass, tidal forces outstrip the star's own gravity, converting the star into a stream of debris. Astronomers call this a tidal disruption event. Matter falling toward a black hole collects into a spinning accretion disk, where it becomes compressed and heated before eventually spilling over the black hole's event horizon, the point beyond which nothing can escape and astronomers cannot observe. Tidal disruption flares carry important information about how this debris initially settles into an accretion disk.
Astronomers know the X-ray emission in these flares arises very close to the black hole. But the location of optical and UV light was unclear, even puzzling. In some of the best-studied events, this emission seems to be located much farther than where the black hole's tides could shatter the star. Additionally, the gas emitting the light seemed to remain at steady temperatures for much longer than expected.
ASASSN-14li was discovered November 22, 2014, in images obtained by the All Sky Automated Survey for SuperNovae (ASASSN), which includes robotic telescopes in Hawaii and Chile. Follow-up observations with Swift's X-ray and Ultraviolet/Optical telescopes began eight days later and continued every few days for the next nine months. The researchers supplemented later Swift observations with optical data from the Las Cumbres Observatory headquartered in Goleta, California.
The results show how interactions among the infalling debris could create the observed optical and UV emission.
Tidal debris initially falls toward the black hole but overshoots, arcing back out along elliptical orbits and eventually colliding with the incoming stream.
"Returning clumps of debris strike the incoming stream, which results in shock waves that emit visible and ultraviolet light," said Goddard's Bradley Cenko, the acting Swift principal investigator and a member of the science team. "As these clumps fall down to the black hole, they also modulate the X-ray emission there."
Future observations of other tidal disruption events will be needed to further clarify the origin of optical and ultraviolet light.
Image Credit: NASA's Goddard Space Flight Center
Explanation from: https://www.nasa.gov/feature/goddard/2017/swift-maps-a-stars-death-spiral-into-a-black-hole
Senin, 20 Maret 2017
Spiral Galaxy NGC 221
This image shows the swirling shape of galaxy NGC 2217, in the constellation of Canis Major (The Great Dog). In the central region of the galaxy is a distinctive bar of stars within an oval ring. Further out, a set of tightly wound spiral arms almost form a circular ring around the galaxy. NGC 2217 is therefore classified as a barred spiral galaxy, and its circular appearance indicates that we see it nearly face-on.
The outer spiral arms have a bluish colour, indicating the presence of hot, luminous, young stars, born out of clouds of interstellar gas. The central bulge and bar are yellower in appearance, due to the presence of older stars. Dark streaks can also be seen in places against the galaxy’s arms and central bulge, where lanes of cosmic dust block out some of the starlight.
The majority of spiral galaxies in the local Universe — including our own Milky Way — are thought to have a bar of some kind, and these structures play an important role in the development of a galaxy. They can, for example, funnel gas towards the centre of the galaxy, helping to feed a central black hole, or to form new stars.
Image Credit: ESO
Explanation from: https://www.eso.org/public/images/potw1204a/
Dracaena Cinnabari
Dracaena cinnabari, the Socotra dragon tree or dragon blood tree, is a dragon tree native to the Socotra archipelago, part of Yemen, located in the Arabian Sea. It is so called due to the red sap that the trees produce.
The dragon blood tree has a unique and strange appearance, with an "upturned, densely packed crown having the shape of an uprightly held umbrella". This evergreen species is named after its dark red resin, which is known as "dragon's blood". Unlike most monocot plants, Dracaena displays secondary growth, D. cinnabari even has growth zones resembling tree rings found in dicot tree species. Along with other arborescent Dracaena species it has a distinctive growth habit called "dracoid habitus". Its leaves are found only at the end of its youngest branches; its leaves are all shed every 3 or 4 years before new leaves simultaneously mature. Branching tends to occur when the growth of the terminal bud is stopped, due to either flowering or traumatic events (e.g. herbivory).
Its fruits are small fleshy berries containing between 1 and 3 seeds. As they develop they turn from green to black, and then become orange when ripe. The berries are eaten by birds (e.g. Onychognatus species) and thereby dispersed. The seeds are 4–5 mm in diameter and weigh on average 68 mg. The berries exude a deep red resin, known as dragon’s blood.
Like other monocotyledons, such as palms, the dragon’s blood tree grows from the tip of the stem, with the long, stiff leaves borne in dense rosettes at the end (4, 5, 7). It branches at maturity to produce an umbrella-shaped crown, with leaves that measure up to 60 cm long and 3 cm wide. The trunk and the branches of the dragon blood are thick and stout and display dichotomous branching, where each of the branches repeatedly divides in two sections.
The dragon's blood tree usually produces its flowers around February, though flowering does vary with location. The flowers tend to grow at the end of the branches. The flowers have inflorescences, and they bear small clusters of fragrant, white or green flowers. The fruits take five months to completely mature. The fruits are described as a fleshy berry, which changes from green to black as it gradually ripens. The fleshy berry fruit ends up being an orange-red color that contains one to three seeds. The berries are usually eaten and dispersed by birds and other animals.
The unusual shape of the dragon's blood tree is an adaptation for survival in arid conditions with low amounts of soil, such as in mountaintops. The large, packed crown provides shade and reduces evaporation. This shade also aids in the survival of seedlings growing beneath the adult tree, explaining why the trees tend to grow closer together.
Explanation from: https://en.wikipedia.org/wiki/Dracaena_cinnabari
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