Thursday, February 26, 2015

Aurora over Maine

Aurora over Maine: APOD: 2014 September 17 - Aurora over Maine


Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2014 September 17


See Explanation. Clicking on the picture will download the highest resolution version available.
Explanation: It has been a good week for auroras. Earlier this month active sunspot region 2158 rotated into view and unleashed a series of flares and plasma ejections into the Solar System during its journey across the Sun's disk. In particular, a pair of Coronal Mass Ejections (CMEs) impacted the Earth's magnetosphere toward the end of last week, creating the most intense geomagnetic storm so far this year. Although power outages were feared by some, the most dramatic effects of these impacting plasma clouds were auroras seen as far south as Wisconsin, USA. In the featured image taken last Friday night, rays and sheets of multicolored auroras were captured over Acadia National Park, in Maine, USA. Since another CME plasma cloud is currently approaching the Earth, tonight offers another good chance to see an impressive auroral display.

Cocoon Nebula Wide Field

Cocoon Nebula Wide Field: APOD: 2014 September 18 - Cocoon Nebula Wide Field


Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2014 September 18
See Explanation. Clicking on the picture will download the highest resolution version available.
Explanation: In this crowded starfield covering over 2 degrees within the high flying constellation Cygnus, the eye is drawn to the Cocoon Nebula. A compact star forming region, the cosmic Cocoon punctuates a long trail of obscuring interstellar dust clouds. Cataloged as IC 5146, the nebula is nearly 15 light-years wide, located some 4,000 light years away. Like other star forming regions, it stands out in red, glowing, hydrogen gas excited by the young, hot stars and blue, dust-reflected starlight at the edge of an otherwise invisible molecular cloud. In fact, the bright star near the center of this nebula is likely only a few hundred thousand years old, powering the nebular glow as it clears out a cavity in the molecular cloud's star forming dust and gas. But the long dusty filaments that appear dark in this visible light image are themselves hiding stars in the process of formation that can be seen seen at infrared wavelengths.

Potentially Habitable Moons

Potentially Habitable Moons: APOD: 2014 September 19 - Potentially Habitable Moons


Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2014 September 19


See Explanation. Clicking on the picture will download the highest resolution version available.
Explanation: For astrobiologists, these may be the four most tantalizing moons in our Solar System. Shown at the same scale, their exploration by interplanetary spacecraft has launched the idea that moons, not just planets, could have environments supporting life. The Galileo mission to Jupiter discovered Europa's global subsurface ocean of liquid water and indications of Ganymede's interior seas. At Saturn, the Cassini probe detected erupting fountains of water ice from Enceladus indicating warmer subsurface water on even that small moon, while finding surface lakes of frigid but still liquid hydrocarbons beneath the dense atmosphere of large moon Titan. Now looking beyond the Solar System, new research suggests that sizable exomoons, could actually outnumber exoplanets in stellar habitable zones. That would make moons the most common type of habitable world in the Universe.

Dawn is showing us exotic scenery on a world

Dawn Journal | February 25:

Dear Fine and Dawndy Readers,

The Dawn spacecraft is performing flawlessly as it conducts the first exploration of the first dwarf planet. Each new picture of Ceres reveals exciting and surprising new details about a fascinating and enigmatic orb that has been glimpsed only as a smudge of light for more than two centuries. And yet as that fuzzy little blob comes into sharper focus, it seems to grow only more perplexing.

Dawn is showing us exotic scenery on a world that dates back to the dawn of the solar system, more than 4.5 billion years ago. Craters large and small remind us that Ceres lives in the rough and tumble environment of the main asteroid belt between Mars and Jupiter, and collectively they will help scientists develop a deeper understanding of the history and nature not only of Ceres itself but also of the solar system.

Ceres Op Nav 3 animated gif

Dawn observed Ceres for three hours, or one third of a Cerean day, on Feb. 3-4. The spacecraft was 91,000 miles (146,000 kilometers) from the dwarf planet in this imaging session, known as OpNav 3. More detail on that one big bright spot is shown in another image below. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
Even as we discover more about Ceres, some mysteries only deepen. It certainly does not require sophisticated scientific insight to be captivated by the bright spots. What are they? At this point, the clearest answer is that the answer is unknown. One of the great rewards of exploring the cosmos is uncovering new questions, and this one captures the imagination of everyone who gazes at the pictures sent back from deep space.

Other intriguing features newly visible on the unfamiliar landscape further assure us that there will be much more to see and to learn — and probably much more to puzzle over — when Dawn flies in closer and acquires new photographs and myriad other measurements. Over the course of this year, as the spacecraft spirals to lower and lower orbits, the view will continue to improve. In the lowest orbit, the pictures will display detail well over one hundred times finer than the RC2 pictures returned a few days ago (and shown below). Right now, however, Dawn is not getting closer to Ceres. On course and on schedule for entering orbit on March 6, Earth’s robotic ambassador is slowly separating from its destination.

“Slowly” is the key. Dawn is in the vicinity of Ceres and is not leaving. The adventurer has traveled more than 900 million miles (1.5 billion kilometers) since departing from Vesta in 2012, devoting most of the time to using its advanced ion propulsion system to reshape its orbit around the sun to match Ceres’ orbit. Now that their paths are so similar, the spacecraft is receding from the massive behemoth at the leisurely pace of about 35 mph (55 kilometers per hour), even as they race around the sun together at 38,700 mph (62,300 kilometers per hour). The probe is expertly flying an intricate course that would be the envy of any hotshot spaceship pilot. To reach its first observational orbit — a circular path from pole to pole and back at an altitude of 8,400 miles (13,500 kilometers) — Dawn is now taking advantage not only of ion propulsion but also the gravity of Ceres.

On Feb. 23, the spacecraft was at its closest to Ceres yet, only 24,000 miles (less than 39,000 kilometers), or one-tenth of the separation between Earth and the moon. Momentum will carry it farther away for a while, so as it performs the complex cosmic choreography, Dawn will not come this close to its permanent partner again for six weeks. Well before then, it will be taken firmly and forever into Ceres’ gentle gravitational hold.

The photographs Dawn takes during this approach phase serve several purposes. Besides fueling the fires of curiosity that burn within everyone who looks to the night sky in wonder or who longs to share in the discoveries of celestial secrets, the images are vital to engineers and scientists as they prepare for the next phase of exploration.



These two views of Ceres were acquired by NASA's Dawn spacecraft on Feb. 12, 2015


Dawn acquired these two pictures of Ceres on Feb. 12 at a distance of 52,000 miles (83,000 kilometers) during the first “rotation characterization,” or RC1. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA






These two views of Ceres were acquired by NASA's Dawn spacecraft on Feb. 12, 2015


Dawn acquired these two pictures of Ceres on Feb. 19 at a distance of 28,000 miles (46,000 kilometers) in RC2. Dawn’s trajectory took it north between RC1 and RC2, so the terrain within view of its camera is farther north here than in RC1. The angle of the sunlight is different as well. Nevertheless, each of these two perspectives is close in longitude to the two above, so some features apparent here are also visible in the RC1 photos. The careful observer will note that these pictures are very cool, especially when compared with earlier ones from Dawn and the best from Hubble Space Telescope, as shown in last month’s Dawn Journal. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
The primary purpose of the pictures is for “optical navigation” (OpNav), to ensure the ship accurately sails to its planned orbital port. Dawn is the first spacecraft to fly into orbit around a massive solar system world that had not previously been visited by a spacecraft. Just as when it reached its first deep-space target, the fascinating protoplanet Vesta, mission controllers have to discover the nature of the destination as they proceed. They bootstrap their way in, measuring many characteristics with increasing accuracy as they go, including its location, its mass and the direction of its rotation axis.

Let’s consider this last parameter. Think of a spinning ball. (If the ball is large enough, you could call it a planet.) It turns around an axis, and the two ends of the axis are the north and south poles. The precise direction of the axis is important for our mission because in each of the four observation orbits (previews of which were presented in February, May, June and August), the spacecraft needs to fly over the poles. Polar orbits ensure that as Dawn loops around, and Ceres rotates beneath it every nine hours, the explorer eventually will have the opportunity to see the entire surface. Therefore, the team needs to establish the location of the rotation axis to navigate to the desired orbit.



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Dawn took this picture in RC2. The improved resolution shows that the intriguing bright spot from earlier pictures is actually two bright spots. What a wonderful mystery this is!

Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
We can imagine extending the rotation axis far outside the ball, even all the way to the stars. Current residents of Earth, for example, know that their planet’s north pole happens to point very close to a star appropriately named Polaris (or the North Star), part of an asterism known as the Little Dipper in the constellation Ursa Minor (the Little Bear). The south pole, of course, points in exactly the opposite direction, to the constellation Octans (the Octant), but is not aligned with any salient star.

With their measurements of how Ceres rotates, the team is zeroing in on the orientation of its poles. We now know that residents of (and, for that mater, visitors to) the northern hemisphere there would see the pole pointing toward an unremarkable region of the sky in Draco (the Dragon). Those in the southern hemisphere would note the pole pointing toward a similarly unimpressive part of Volans (the Flying Fish). (How appropriate it is that that pole is directed toward a constellation with that name will be known only after scientists advance their understanding of the possibility of a subsurface ocean at Ceres.)

The orientation of Ceres’ axis proves convenient for Dawn’s exploration. Earthlings are familiar with the consequences of their planet’s axis being tilted by about 23 degrees. Seasons are caused by the annual motion of the sun between 23 degrees north latitude and 23 degrees south. A large area around each pole remains in the dark during winter. Vesta’s axis is tipped 27 degrees, and when Dawn arrived, the high northern latitudes were not illuminated by the sun. The probe took advantage of its extraordinary maneuverability to fly to a special mapping orbit late in its residence there, after the sun had shifted north. That will not be necessary at Ceres. That world’s axis is tipped at a much smaller angle, so throughout a Cerean year (lasting 4.6 Earth years), the sun stays between 4 degrees north latitude and 4 degrees south. Seasons are much less dramatic. Among Dawn’s many objectives is to photograph Ceres. Because the sun is always near the equator, the illumination near the poles will change little. It is near the beginning of southern hemisphere winter on Ceres now, but the region around the south pole hidden in hibernal darkness is tiny. Except for possible shadowing by local variations in topography (as in deep craters), well over 99 percent of the dwarf planet’s terrain will be exposed to sunlight each day.

Guiding Dawn from afar, the operations team incorporates the new information about Ceres into occasional updates to the flight plan, providing the spacecraft with new instructions on the exact direction and throttle level to use for the ion engine. As they do so, subtle aspects of the trajectory change. Last month we described the details of the plan for observing Ceres throughout the four-month approach phase and predicted that some of the numbers could change slightly. So, careful readers, for your convenience, here is the table from January, now with minor updates.



Beginning of activity in Pacific Time zone Distance from Dawn to Ceres in miles (kilometers) Ceres diameter in pixels Resolution in miles (kilometers) per pixel Resolution compared to Hubble Illuminated portion of disk Activity
Dec 1, 2014 740,000

(1.2 million)
9 70

(112)
0.25 94% Camera calibration
Jan 13, 2015 238,000

(383,000)
27 22

(36)
0.83 95% OpNav 1
Jan 25 147,000

(237,000)
43 14

(22)
1.3 96% OpNav 2
Feb 3 91,000

(146,000)
70 8.5

(14)
2.2 97% OpNav 3
Feb 12 52,000

(83,000)
122 4.9

(7.8)
3.8 98% RC1
Feb 19 28,000

(46,000)
222 2.7

(4.3)
7.0 87% RC2
Feb 25 25,000

(40,000)
255 2.3

(3.7)
8.0 44% OpNav 4
Mar 1 30,000

(49,000)
207 2.9

(4.6)
6.5 23% OpNav 5
Apr 10 21,000

(33,000)
306 1.9

(3.1)
9.6 17% OpNav 6
Apr 14 14,000

(22,000)
453 1.3

(2.1)
14 49% OpNav 7


In addition to changes based on discoveries about the nature of Ceres, some changes are dictated by more mundane considerations (to the extent that there is anything mundane about flying a spacecraft in the vicinity of an alien world more than a thousand times farther from Earth than the moon). For example, to accommodate changes in the schedule for the use of the Deep Space Network, some of the imaging sessions shifted by a few hours, which can make small changes in the corresponding views of Ceres.

The only important difference between the table as presented in January and this month, however, is not to be found in the numbers. It is that OpNav 3, RC1 and RC2 are now in the past, each having been completed perfectly.

As always, if you prefer to save yourself the time and effort of the multi-billion-mile (multi-billion-kilometer) interplanetary journey to Ceres, you can simply go here to see the latest views from Dawn. (The Dawn project is eager to share pictures promptly with the public. The science team has the responsibility of analyzing and interpreting the images for scientific publication. The need for accuracy and scientific review of the data slows the interpretation and release of the pictures. But just as with all of the marvelous findings from Vesta, everything from Ceres will be available as soon as practicable.)

In November we delved into some of the details of Dawn’s graceful approach to Ceres, and last month we considered how the trajectory affected the scene presented to Dawn’s camera. Now that we have updated the table, we can enhance a figure from both months that showed the craft’s path as it banks into orbit and maneuvers to its first observational orbit. (As a reminder, the diagram illustrates only two of the three dimensions of the ship’s complicated route. Another diagram in November showed another perspective, and we will include a different view next month.)



to be added


Section of Dawn’s approach trajectory. We are looking down on the north pole of Ceres. (Readers who reside in the constellation Draco will readily recognize this perspective). The sun is off the figure far to the left. The spacecraft flies in from the left and then is captured (enters orbit) on the way to the apex of its orbit. It gets closer to Ceres during the first part of its approach but then recedes for a while before coming in still closer at the end. When Dawn is on the right side of the figure, it sees only a crescent of Ceres, because the illumination is from the left. The trajectory is solid where Dawn is thrusting with its ion engine, which is most of the time. The labels show where it pauses to turn, point at Ceres, conduct the indicated observation, turn to point its main antenna to Earth, transmit its precious findings, turn back to the orientation needed for thrusting, and then restart the ion engine. Because RC1 and RC2 observations extend for a full Cerean day of more than nine hours, those periods are longer, both to collect data and to radio the results to Earth. Note that there are four periods on the right side of the figure between capture and OpNav 6 when Dawn pauses thrusting for telecommunications and radio navigation but does not take pictures, as explained here. Credit: NASA/JPL
We can zoom out to see where the earlier OpNavs were.



To be added


All of Dawn’s observations during the approach phase. Note how much shorter this caption is than the one above, despite the similarity of the figures. Credit: NASA/JPL
As the table and figures indicate, in OpNav 6, when Ceres and the sun are in the same general direction from Dawn’s vantage point, only a small portion of the illuminated terrain will be visible. The left side of Ceres will be in daylight, and most of the hemisphere facing the spacecraft will be in the darkness of night. To get an idea of what the shape of the crescent will be, terrestrial readers can use the moon on March 16. It will be up much of the day, setting in the middle of the afternoon, and it will be comparable to the crescent Dawn will observe on April 10. (Of course, the exact shape will depend on your observing location and what time you look, but this serves as a rough preview.) Fortunately, our spacecraft does not have to contend with bad weather, but you might, so we have generously scheduled a backup opportunity for you. The moon will be new on March 20, and the crescent on March 23 will be similar to what it was on March 16. It will rise in the mid morning and be up until well after the sun sets.

Photographing Ceres as it arcs into orbit atop a blue-green beam of xenon ions, setting the stage for more than a year of detailed investigations with its suite of sophisticated sensors, Dawn is sailing into the history books. No spacecraft has reached a dwarf planet before. No spacecraft has orbited two extraterrestrial destinations before. This amazing mission is powered by the insatiable curiosity and extraordinary ingenuity of creatures on a planet far, far away. And it carries all of them along with it on an ambitious journey that grows only more exciting as it continues. Humankind is about to witness scenes never before seen and perhaps never even imagined. Dawn is taking all of us on a daring adventure to a remote and unknown part of the cosmos. Prepare to be awed.

Dawn is 24,600 miles (39,600 kilometers) from Ceres, or 10 percent of the average distance between Earth and the moon. It is also 3.42 AU (318 million miles, or 512 million kilometers) from Earth, or 1,330 times as far as the moon and 3.46 times as far as the sun today. Radio signals, traveling at the universal limit of the speed of light, take 57 minutes to make the round trip.

Dr. Marc D. Rayman

7:00 a.m. PST February 25, 2015


Wednesday, February 25, 2015

The Rosette Nebula in Hydrogen and Oxygen

The Rosette Nebula in Hydrogen and Oxygen:

ngc2244_rottal_1080.jpg
The Rosette Nebula in Hydrogen and Oxygen

Shoreline of the Universe

Shoreline of the Universe: APOD: 2014 September 20 - Shoreline of the Universe


Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2014 September 20


See Explanation. Clicking on the picture will download the highest resolution version available.
Explanation: Against dark rifts of interstellar dust, the ebb and flow of starlight along the Milky Way looks like waves breaking on a cosmic shore in this night skyscape. Taken with a digital camera from the dunes of Hatteras Island, North Carolina, planet Earth, the monochrome image is reminiscent of the time when sensitive black and white film was a popular choice for dimly lit night- and astro-photography. Looking south, the bright stars of Sagittarius and Scorpius are near the center of the frame. Wandering Mars, Saturn, and Zubenelgenubi (Alpha Librae) form the compact triangle of bright celestial beacons farther right of the galaxy's central bulge. Of course, the evocative black and white beach scene could also be from that vintage 1950s scifi movie you never saw, "It Came From Beyond the Dunes."

Saturn at Equinox

Saturn at Equinox: APOD: 2014 September 21 - Saturn at Equinox


Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2014 September 21


See Explanation. Clicking on the picture will download the highest resolution version available.
Explanation: How would Saturn look if its ring plane pointed right at the Sun? Before August 2009, nobody knew. Every 15 years, as seen from Earth, Saturn's rings point toward the Earth and appear to disappear. The disappearing rings are no longer a mystery -- Saturn's rings are known to be so thin and the Earth is so near the Sun that when the rings point toward the Sun, they also point nearly edge-on at the Earth. Fortunately, in this third millennium, humanity is advanced enough to have a spacecraft that can see the rings during equinox from the side. In August 2009, that Saturn-orbiting spacecraft, Cassini, was able to snap a series of unprecedented pictures of Saturn's rings during equinox. A digital composite of 75 such images is shown above. The rings appear unusually dark, and a very thin ring shadow line can be made out on Saturn's cloud-tops. Objects sticking out of the ring plane are brightly illuminated and cast long shadows. Inspection of these images is helping humanity to understand the specific sizes of Saturn's ring particles and the general dynamics of orbital motion. This week, Earth undergoes an equinox.

NGC 206 and the Star Clouds of Andromeda

NGC 206 and the Star Clouds of Andromeda: APOD: 2014 September 25 - NGC 206 and the Star Clouds of Andromeda


Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2014 September 25
See Explanation. Clicking on the picture will download the highest resolution version available.
Explanation: The large stellar association cataloged as NGC 206 is nestled within the dusty arms of the neighboring Andromeda galaxy. Also known as M31, the spiral galaxy is a mere 2.5 million light-years away. NGC 206 is near top center in this gorgeous close-up of the southwestern extent of Andromeda's disk, a remarkable composite of data from space and ground-based observatories. The bright, blue stars of NGC 206 indicate its youth. In fact, its youngest massive stars are less than 10 million years old. Much larger than the open or galactic clusters of young stars in the disk of our Milky Way galaxy, NGC 206 spans about 4,000 light-years. That's comparable in size to the giant stellar nurseries NGC 604 in nearby spiral M33 and the Tarantula Nebula, in the Large Magellanic Cloud. Star forming sites within Andromeda are revealed by the telltale reddish emission from clouds of ionized hydrogen gas.

Two Black Holes Dancing in 3C 75

Two Black Holes Dancing in 3C 75: APOD: 2014 September 28 - Two Black Holes Dancing in 3C 75


Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2014 September 28


See Explanation. Clicking on the picture will download the highest resolution version available.
Explanation: What's happening at the center of active galaxy 3C 75? The two bright sources at the center of this composite x-ray (blue)/ radio (pink) image are co-orbiting supermassive black holes powering the giant radio source 3C 75. Surrounded by multimillion degree x-ray emitting gas, and blasting out jets of relativistic particles the supermassive black holes are separated by 25,000 light-years. At the cores of two merging galaxies in the Abell 400 galaxy cluster they are some 300 million light-years away. Astronomers conclude that these two supermassive black holes are bound together by gravity in a binary system in part because the jets' consistent swept back appearance is most likely due to their common motion as they speed through the hot cluster gas at 1200 kilometers per second. Such spectacular cosmic mergers are thought to be common in crowded galaxy cluster environments in the distant universe. In their final stages the mergers are expected to be intense sources of gravitational waves.

A Full Circle Rainbow over Australia

A Full Circle Rainbow over Australia: APOD: 2014 September 30 - A Full Circle Rainbow over Australia


Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2014 September 30


See Explanation. Clicking on the picture will download the highest resolution version available.
Explanation: Have you ever seen an entire rainbow? From the ground, typically, only the top portion of a rainbow is visible because directions toward the ground have fewer raindrops. From the air, though, the entire 360 degree circle of a rainbow is more commonly visible. Pictured here, a full circle rainbow was captured over Cottesloe Beach near Perth, Australia last year by a helicopter flying between a setting sun and a downpour. An observer-dependent phenomenon primarily caused by the internal reflection of sunlight by raindrops, the 84-degree diameter rainbow followed the helicopter, intact, for about 5 kilometers. As a bonus, a second rainbow that was more faint and color-reversed was visible outside the first.

The Butterfly Nebula from Hubble

The Butterfly Nebula from Hubble: APOD: 2014 October 1 - The Butterfly Nebula from Hubble


Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2014 October 1


See Explanation. Clicking on the picture will download the highest resolution version available.
Explanation: The bright clusters and nebulae of planet Earth's night sky are often named for flowers or insects. Though its wingspan covers over 3 light-years, NGC 6302 is no exception. With an estimated surface temperature of about 250,000 degrees C, the dying central star of this particular planetary nebula has become exceptionally hot, shining brightly in ultraviolet light but hidden from direct view by a dense torus of dust. This sharp close-up of the dying star's nebula was recorded in 2009 by the Hubble Space Telescope's Wide Field Camera 3, and is presented here in reprocessed colors. Cutting across a bright cavity of ionized gas, the dust torus surrounding the central star is near the center of this view, almost edge-on to the line-of-sight. Molecular hydrogen has been detected in the hot star's dusty cosmic shroud. NGC 6302 lies about 4,000 light-years away in the arachnologically correct constellation of the Scorpion (Scorpius).

The Bubble Nebula

The Bubble Nebula: APOD: 2014 October 2 - The Bubble Nebula


Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2014 October 2
See Explanation. Clicking on the picture will download the highest resolution version available.
Explanation: Blown by the wind from a massive star, this interstellar apparition has a surprisingly familiar shape. Cataloged as NGC 7635, it is also known simply as The Bubble Nebula. Although it looks delicate, the 10 light-year diameter bubble offers evidence of violent processes at work. Below and left of the Bubble's center is a hot, O star, several hundred thousand times more luminous and around 45 times more massive than the Sun. A fierce stellar wind and intense radiation from that star has blasted out the structure of glowing gas against denser material in a surrounding molecular cloud. The intriguing Bubble Nebula and associated cloud complex lie a mere 11,000 light-years away toward the boastful constellation Cassiopeia. This tantalizing view of the cosmic bubble is composed from narrowband image data, recording emission from the region's ionized hydrogen and oxygen atoms. To create the three color image, hydrogen and oxygen emission were used for red and blue and combined to create the green channel.

Aurora and Milky Way in a Little Sky

Aurora and Milky Way in a Little Sky: APOD: 2014 October 3 - Aurora and Milky Way in a Little Sky


Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2014 October 3


See Explanation. Clicking on the picture will download the highest resolution version available.
Explanation: Stepping stones seem to lead to the Milky Way as it stretches across this little sky. Of course, the scene is really the northern hemisphere's autumnal equinox night. Water and sky are inverted by a top to bottom, around the horizon stereographic projection centered on the zenith above Lake Storsjön in Jämtland, Sweden. In the north the Milky Way arcs from east to west overhead as fall begins, but the season is also a good time for viewing aurora. Geomagnetic storms increase in frequency near the equinox and produce remarkable displays of northern lights at high latitudes, like the eerie greenish glow reflected in this watery cosmos.

NASA's Chandra Finds Intriguing Member of Black Hole Family Tree

NASA's Chandra Finds Intriguing Member of Black Hole Family Tree:

NGC 2276*

A newly discovered object in the galaxy NGC 2276 may prove to be an important black hole that helps fill in the evolutionary story of these exotic objects, as described in our latest press release. The main image in this graphic contains a composite image of NGC 2766 that includes X-rays from NASA's Chandra X-ray Observatory (pink) combined with optical data from the Hubble Space Telescope and the Digitized Sky Survey (red, green and blue). The inset is a zoom into the interesting source that lies in one of the galaxy's spiral arms. This object, called NGC 2276-3c, is seen in radio waves (red) in observations from the European Very Long Baseline Interferometry Network, or EVN.

Astronomers have combined the X-ray and radio data to determine that NGC 2766-3c is likely an intermediate-mass black hole (IMBH). As the name suggests, IMBHs are black holes that are larger than stellar-mass black holes that contain about five to thirty times the mass of the Sun, but smaller than supermassive black holes that are millions or even billions of solar masses. The researchers estimated the mass of NGC 2766-3c using a well-known relationship between how bright the source is in radio and X-rays, and the mass of the black hole. The X-ray and radio brightness were based on observations with Chandra and the EVN. They found that NGC 2276-3c contains about 50,000 times the mass of the Sun.

IMBHs are interesting to astronomers because they may be the seeds that eventually evolve into supermassive black holes. They also may be strongly influencing their environment. This latest result on NGC 2276-3c suggests that it may be suppressing the formation of new stars around it. The EVN radio data reveal an inner jet that extends about 6 light years from NGC 2276-3c. Additional observations by the NSF's Karl Jansky Very Large Array (VLA) show large-scale radio emission extending out to over 2,000 light years away from the source.

A region along the jet extending to about 1,000 light years away from NGC 2766-3c is devoid of young stars. This might provide evidence that the jet has cleared out a cavity in the gas, preventing new stars from forming there. The VLA data also reveal a large population of stars at the edge of the radio emission from the jet. This enhanced star formation could take place either when the material swept out by the jet collides with dust and gas in between the stars in NGC 2276, or when triggered by the merger of NGC 2276 with a dwarf galaxy.

More information at http://chandra.harvard.edu/photo/2015/ngc2276/index.html

-Megan Watzke, CXC

Winds of Supermassive Black Holes Can Shape Galaxy-Wide Star Formation

Winds of Supermassive Black Holes Can Shape Galaxy-Wide Star Formation:



An illustration that shows the powerful winds driven by a supermassive black hole at the centre of a galaxy. The schematic figure in the inset depicts the innermost regions of the galaxy where a black hole accretes, that is, consumes, at a very high rate the surrounding matter (light grey) in the form of a disc (darker grey). At the same time, part of that matter is cast away through powerful winds. (Credits: XMM-Newton and NuSTAR Missions; NASA/JPL-Caltech;Insert:ESA)


An illustration that shows the powerful winds driven by a supermassive black hole at the centre of a galaxy. The schematic figure (inset) depicts the innermost regions of the galaxy where a black hole accretes, effectively consumes, at a very high rate the surrounding matter (light grey) in the form of a disc (darker grey). At the same time, part of that matter is cast away through powerful winds. (Credits: XMM-Newton and NuSTAR Missions; NASA/JPL-Caltech;Insert:ESA)
The combined observations from two generations of X-Ray space telescopes have now revealed a more complete picture of the nature of high-speed winds expelled from super-massive black holes. Scientist analyzing the observations discovered that the winds linked to these black holes can travel in all directions and not just a narrow beam as previously thought. The black holes reside at the center of active galaxies and quasars and are surrounded by accretion discs of matter. Such broad expansive winds have the potential to effect star formation throughout the host galaxy or quasar. The discovery will lead to revisions in the theories and models that more accurately explain the evolution of quasars and galaxies.



This plot of data from NASA's Nuclear Spectroscopic Telescope Array (NuSTAR) and the European Space Agency's (ESA's) XMM-Newton determines for the first time the shape of ultra-fast winds from supermassive black holes, or quasars. The winds blow in every direction, in a nearly spherical fashion, coming from both sides of a galaxy (Credit: NASA/JPL-Caltech/Keele Univ.;XMM-Newton and NuSTAR Missions)


This plot of data from NASA’s Nuclear Spectroscopic Telescope Array (NuSTAR) and the European Space Agency’s (ESA’s) XMM-Newton determines for the first time the shape of ultra-fast winds from supermassive black holes, or quasars. The winds blow in every direction, in a nearly spherical fashion, coming from both sides of a galaxy (Credit: NASA/JPL-Caltech/Keele Univ.;XMM-Newton and NuSTAR Missions, [Ref])
The observations were by the XMM-Newton and NuSTAR x-ray space telescopes of the quasar PDS 456. The observations were combined into the graphic, above. PDS 456 is a bright quasar residing in the constellation Serpens Cauda (near Ophiuchus). The data graph shows both a peak and a trough in the otherwise nominal x-ray emission profile as shown by the NuSTAR data (pink). The peak represents X-Ray emissions directed towards us (i.e.our telescopes) while the trough is X-Ray absorption that indicates that the expulsion of winds from the super-massive black hole is in many directions – effectively a spherical shell. The absorption feature caused by iron in the high speed wind is the new discovery.


X-Rays are the signature of the most energetic events in the Cosmos but also are produced from some of the most docile bodies – comets. The leading edge of a comet such as Rosetta’s P67 generates X-Ray emissions from the interaction of energetic solar ions capturing electrons from neutral particles in the comet’s coma (gas cloud). The observations of a super-massive black hole in a quasar billions of light years away involve the generation of x-rays on a far greater scale, by winds that evidently has influence on a galactic scale.



A diagram of the ESA XMM-Newton X-Ray Telescope. Delivered to orbit by a Ariane 5 launch vehicle in 1999. (Illustration Credit: ESA/XMM-Newton)


A diagram of the ESA XMM-Newton X-Ray Telescope. Delivered to orbit by a Ariane 5 launch vehicle in 1999. (Illustration Credit: ESA/XMM-Newton)
The study of star forming regions and the evolution of galaxies has focused on the effects of shock waves from supernova events that occur throughout the lifetime of a galaxy. Such shock waves trigger the collapse of gas clouds and formation of new stars. This new discovery by the combined efforts of two space telescope teams provides astrophysicists new insight into how star and galaxy formation takes place. Super-massive blackholes, at least early in the formation of a galaxy, can influence star formation everywhere.



The NuStar Space Telescope launched into Earth orbit by a Orbital Science Corp. Pegasus rocket, 2012. The Wolter telescope design images throughout a spectral range from 5 to 80 KeV. (Credit: NASA/Caltech-JPL)


The NuStar Space Telescope launched into Earth orbit by a Orbital Science Corp. Pegasus rocket, 2012. The Wolter telescope design – optics in the foreground, 10 meter truss and detectors at back – images throughout a spectral range from 5 to 80 KeV. (Credit: NASA/Caltech-JPL)
Both the ESA built XMM-Newton and the NuSTAR X-Ray space telescope, a SMEX class NASA mission, use grazing incidence optics, not glass (refraction) or mirrors (reflection) as in conventional visible light telescopes. The incidence angle of the X-rays must be very shallow and consequently the optics are extended out on a 10 meter (33 foot) truss in the case of NuSTAR and over a rigid frame on the XMM-Newton.



Diagram of one of three x-ray telescopes of the XMM-Newton design. Only a few of the grazing angle concentric mirrors are shown. Inset: a simplified illustration of how a Wolter telescope works. (Credits: Wikimedia, ESA)


Diagram of one of three x-ray telescopes of the XMM-Newton design. Only a few of the grazing angle concentric mirrors are shown. Inset: a simplified illustration of how a Wolter telescope works. (Credits: Wikimedia, ESA) [click to enlarge]


The spectral ranges of the XMM-Newton and NuSTAR Telescopes. (Credits: NASA, ESA)


The spectral ranges of the XMM-Newton and NuSTAR Telescopes. (Credits: NASA, ESA)
The ESA built XMM-Newton was launched in 1999, an older generation design that used a rigid frame and structure. All the fairing volume and lift capability of the Ariane 5 launch vehicle was needed to put the Newton in orbit. The latest X-Ray telescope – NuSTAR – benefits from tens years of technological advances. The detectors are more efficient and faster and the rigid frame was replaced with a compact truss which required all of 30 minutes to deploy. Consequently, NuSTAR was launched on a Pegasus rocket piggybacked on a L-1011, a significantly smaller and less expensive launch system.

So now these observations are effectively delivered to the theorists and modelers. The data is like a new ingredient in the batter from which a galaxy and stars are formed. The models of galaxy and star formation will improve and will more accurately describe how quasars, with their active super-massive black-holes, transition into more quiescent galaxies such as our own Milky Way.

Reference:

XMM-NEWTON AND NUSTAR SPECTRUM OF THE QUASAR PDS 456

ARTIST’S IMPRESSION OF BLACK-HOLE WIND IN A GALAXY



About 

Contributing writer Tim Reyes is a former NASA software engineer and analyst who has supported development of orbital and lander missions to the planet Mars since 1992. He has an M.S. in Space Plasma Physics from University of Alabama, Huntsville.

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Incredible “Birdman”-like Tracking-Shot Timelapse of Earth from Space

Incredible “Birdman”-like Tracking-Shot Timelapse of Earth from Space:



The Academy Award winning film “Birdman” used what’s called tracking shot to create the sense of a seamless one-shot film. A new timelapse created from imagery captured by astronauts on the International Space Station uses the same technique — which has not been used in previous ISS timelapses — with stunning results. Additionally, the footage is very recent, from January and February 2015. It was compiled by Phil Selmes.

“The footage has been composited and edited to show enhanced camera movement, a day to night transition, and an uninterrupted camera movement which links two timelapse shots seamlessly,” Selmes told Universe Today. “These processes have never been used to present ISS time lapse footage in this way before.”

(...)
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Post tags: Earth, ISS videos, Johnson Space Center, Phil Selmes, Timelapse videos


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A New Sungrazing Comet May Brighten in the Evening Sky, Here’s How to See It

A New Sungrazing Comet May Brighten in the Evening Sky, Here’s How to See It:



Photo taken at 20:00 UT (2 pm. CST) Feb. 19 with the SOHO C2 coronagraph, a device that blocks the Sun, allowing a view of the area close by. Credit: NASA/ESA


Photo taken at 20:00 UT (2 pm. CST) Feb. 19 with the SOHO C2 coronagraph, a device that blocks the Sun, allowing a view of the area close by. A faint tail can be seen just below the comet’s bright head. Credit: NASA/ESA
A newly-discovered comet may soon become bright enough to see from a sky near you. Originally dubbed SOHO-2875, it was spotted in photos taken by the Solar and Heliospheric Observatory (SOHO) earlier this week. Astronomer Karl Battams, who maintains the Sungrazer Project website, originally thought this little comet would dissipate after its close brush with the Sun. To his surprise, it outperformed expectations and may survive long enough to see in the evening sky.



SOHO-2875 seen in a second, wide-field coronograph called LASCO C2 at 2:42 a.m. today Feb. 20. It's already moved a good distance to the west-southwest of the Sun and still displays a short tail. Credit: NASA/ESA


C/2015 D1 (SOHO) seen in a second, wide-field coronograph called LASCO C3 at 2:42 a.m. Feb. 20. Since then it’s well to the east of the Sun into the evening sky. Credit: NASA/ESA
Most sungrazing comets discovered by SOHO are members of the Kreutz family, a group of icy fragments left over from the breakup of a single much larger comet centuries ago. We know they’re all family by their similar orbits. The newcomer, SOHO’s 2,875th comet discovery, is a “non-group” comet or one that’s unrelated to the Kreutz family or any other comet club for that matter. According to Battams these mavericks appear several times a year. As of today (Feb. 24) its official name is C/2015 D1 (SOHO).



Composite of Comet SOHO-2875 crossing the C2 coronagraph field yesterday. Credit: NASA/ESA/Barbara Thompson


Composite of Comet SOHO-2875 crossing the C2 coronagraph field Feb. 19. Credit: NASA/ESA/Barbara Thompson
What’s unusual about #2,875 is how bright it is. At least for now, it appears to have survived the Sun’s heat and gravitational tides and is turning around to the east headed for the evening sky. Before it left SOHO’s field of view on Feb. 21, the comet was still around magnitude +4-4.5.

No one can say for sure whether it has what it takes to hang on, so don’t get your hopes up just yet. Battams and others carefully calculated the comet’s changing position in the SOHO images and sent the data off to the Minor Planet Center, which today published an orbit.

Newly-named Comet C/2015 D1 (SOHO) will share the sky with Venus and Mars at dusk. For the next few nights it will be quite low and nearly impossible to see. Its situation improves over time as the comet moves rapidly northward into Pegasus and Andromeda. Tick marks show the comet's position each evening. Stars are shown to magnitude +6.5. Created with Chris Marriott's SkyMap software
Newly-named Comet C/2015 D1 (SOHO) will share the sky with Venus and Mars at dusk. For the next few nights it will be quite low and nearly impossible to see. Its situation improves over time as the comet moves rapidly northward into Pegasus and Andromeda. Tick marks show the comet’s position each evening. Stars are shown to magnitude +6.5. Created with Chris Marriott’s SkyMap software
Based on this preliminary orbit, I’ve plotted SOHO-2875’s path for the next couple weeks as it tracks up through Pisces and Pegasus during the early evening hours. Given that it’s probably no brighter than magnitude +6 at the moment and very low in the west at dusk, it may still be swamped in twilight’s glow.

Barring an unexpected outburst, there’s no question that the comet will fade in the coming days as its distance from both the Earth and Sun increase. Right now it’s 79 million miles from us and 28 million miles from the Sun. That puts it about 8 million miles closer to the Sun than the planet Mercury.



Comet SOHO-2875 survived its close passage of the Sun and may make an appearance in the evening sky soon. This photo montage was made using the coronagraph (Sun-blocking device) on SOHO. Click to watch a movie of the comet. Credit: NASA/ESA


Comet SOHO-2875 survived its close passage of the Sun and may make an appearance in the evening sky soon. This photo montage was made using the coronagraph (Sun-blocking device) on SOHO. Click to watch a movie of the comet. Credit: NASA/ESA
I drew up the chart for about 75 minutes after sunset in late twilight. Keep in mind that since the comet’s positions were determined via spacecraft imagery, which isn’t as precise as photographing it from ground observatories, its orbit is preliminary. That means it may not be on the precise path shown on the map. Be sure you search up-down and right-left of the plotted locations.

It’s also very possible the comet is in the process of disintegration after perihelion passage, so it may not be a dense, compact object but rather a diffuse cloud of glowing dust. Will it go the way of Comet ISON and fade away to nothing? Who knows? I sure don’t but can’t wait to find out what it’s up to the next clear night.

BTW, if you’ve got a software program that downloads orbital elements for comets to create your own charts, you’ll find the numbers you need in today’s Minor Planet Circular. Be sure to use the “post-perihelion” elements that predict the comet’s location from here on out.



About 

I'm a long-time amateur astronomer and member of the American Association of Variable Star Observers (AAVSO). My observing passions include everything from auroras to Z Cam stars. Every day the universe offers up something both beautiful and thought-provoking. I also write a daily astronomy blog called Astro Bob.

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