Black Holes in NGC 1313

The magenta spots in this image show two black holes in the spiral galaxy called NGC 1313, or the Topsy Turvy galaxy. Both black holes belong to a class called ultraluminous X-ray sources, or ULXs. The magenta X-ray data come from NASA's Nuclear Spectroscopic Telescopic Array, and are overlaid on a visible image from the Digitized Sky Survey.

ULXs consist of black holes actively accreting, or feeding, off material drawn in from a partner star. Astronomers are trying to figure out why ULXs shine so brightly with X-rays.

NuSTAR's new high-energy X-ray data on NGC 1313 helped narrow down the masses of the black holes in the ULXs: the black hole closer to the center of the galaxy is about 70 to 100 times that of our sun. The other black hole is probably smaller, about 30 solar masses.

Image credit: NASA/JPL-Caltech/IRAP

Note: For more information, see Do Black Holes Come in Size Medium?

NGC 2035

The Large Magellanic Cloud is one of the closest galaxies to our own. Astronomers have now used the power of the ESO’s Very Large Telescope to explore NGC 2035, one of its lesser known regions, in great detail. This new image shows clouds of gas and dust where hot new stars are being born and are sculpting their surroundings into odd shapes. But the image also shows the effects of stellar death — filaments created by a supernova explosion (left).

Photo credit: ESO

Note: For more information, see A Fiery Drama of Star Birth and Death.

Black Holes in Circinus Galaxy

The magenta spots in this image show two black holes in the Circinus galaxy: the supermassive black hole at its heart, and a smaller one closer to the edge that belongs to a class called ultraluminous X-ray sources, or ULXs. The magenta X-ray data come from NASA's Nuclear Spectroscopic Telescopic Array, and are overlaid on a visible/infrared image from the Digitized Sky Survey.

ULXs consist of black holes actively accreting, or feeding, off material drawn in from a partner star. Astronomers are trying to figure out why ULXs shine so brightly with X-rays.

The ULX was spotted serendipitously by NuSTAR, which sees high-energy X-ray light. Further observations with other telescopes, combined with NuSTAR's data, revealed that the black hole is about 100 times the mass of our sun.

The Circinus galaxy is located 13 million light-years from Earth in the Circinus constellation.

Image credit: NASA/JPL-Caltech

Note: For more information, see Do Black Holes Come in Size Medium?

Warped Galaxies

Can you match each galaxy in the top row of figure 1 with its warped counterpart in the bottom row? For example, is the warped version of galaxy A in box D, E, or F? Answers are below.

Such galaxy warping occurs naturally in nature in a phenomenon called strong gravitational lensing. The gravity of matter in front of a more distant galaxy, either dark or normal matter, bends and twists the galaxy's light, resulting in wacky shapes and sometimes multiple versions of the same galaxy. It's like seeing a galaxy in a funhouse mirror. Scientists use these natural lenses to make maps of dark matter, an invisible substance permeating our cosmos. The lenses also help in the study of dark energy, an even more mysterious substance thought to be pushing universe apart at increasing speeds.

This quiz demonstrates extreme cases of gravitational lensing. The warped images have been simulated from original images of galaxies taken by NASA's Hubble Space Telescope. Galaxy E shows what is called an "Einstein ring," named after Albert Einstein, who discovered that gravity bends light. In this case, the mass of one body, a lump of dark matter, has twisted the galaxy's light into a ring. In the other two cases, two lensing sources create double-ringed structures.

In reality, most lenses are not this obvious. In what is called weak gravitation lensing, the effects are subtle and hard to tease out. Scientists have created a competition called GREAT3, which stands for GRavitational lEnsing Accuracy Testing 3, to improve methods for measuring weak lensing. Data scientists from an assortment of fields, including machine learning, are invited to solve galaxy puzzles, in which tiny lensing affects have been artificially introduced by the organizers of the challenge. The goal is to figure out what the lensing affects are, and in doing so, help develop new tools for probing the dark side of our cosmos.

Image credit: NASA/JPL-Caltech/UCL

Answers to quiz: A matches F; B matches D; and C matches E.

Note: For more information, see Scientists Seek Other Scientists for Cosmology Problem

Update on Near-Earth Objects 2013 UQ4, C/2013 US10 (Catalina), and 2013 UP8

Two surprisingly large Near-Earth Asteroids have been discovered in just the last week or so, as well as a third moderately large asteroid which, surprisingly, has also gone undetected until now, even though it can pass close enough to Earth to be classified as "potentially hazardous." Not since 1983 has any near-Earth asteroid been found as large as the approximately 12-mile (20-kilometer) size of the two new large ones. In fact, there are only three other known near-Earth asteroids that are of comparable size or larger than the two new large ones.

It is important to note that none of these three new large near-Earth asteroids can come close enough to Earth to represent a near-term threat to our planet.

The first of the new large near-Earth asteroid discoveries is named 2013 UQ4, and it is perhaps the most unusual. This approximately 12-mile (19-kilometer) wide object was spotted by the Catalina Sky Survey on October 23 when the asteroid was 270 million miles (435 million kilometers) away from Earth. Not only is this object unusually large, it follows a very unusual, highly inclined, retrograde orbit about the sun, which means it travels around the sun in the opposite direction of all the planets and the vast majority of asteroids.

The only objects usually found in retrograde orbits are comets, which suggests that 2013 UQ4 may be the remains of an old comet that no longer possesses the near-surface ices required for it to become active while near the sun. Comets that have exhausted most, or all, of their volatile ices do not spew dust during sweeps through the inner-solar system like their less-seasoned, more hyperactive space kin. Without the telltale comet tails or atmospheres, dead comets look like, and in fact for all practical purposes are, asteroids.

As reported on Circular No. 9262 of the International Astronomical Union, the Massachusett's Institute of Technology's Richard Binzel, David Polishook and Rachel Bowens-Rubin observed this object on October 31 with NASA's 3-meter Infrared Telescope Facility in Hawaii and determined this object belongs to the so-called X-type spectral class and exhibits no obvious comet-like activity. This implies about a 4 percent reflectivity, from which they estimate a diameter of approximately 12 miles (19 kilometers).

The second very large near-Earth object, named 2013 US10, was discovered on October 31 by the Catalina Sky Survey. While the reflectivity of this object has not yet been determined, and hence its diameter is still uncertain, it is also likely to be about 12 miles (20 kilometers) in size. Only three near-Earth asteroids (1036 Ganymed, 433 Eros and 3552 Don Quixote) are of comparable size or larger.

Why has it taken so long to discover these large near-Earth asteroids? The delay in discovering 2013 UQ4 is more easily understood because it has a very long orbital period that has kept it out of Earth's neighborhood for centuries. But the delayed discovery of 2013 US10 is a bit harder to explain, since current population models suggest that almost all near-Earth asteroids of this size and orbit should have already been found. A contributing factor may be that this object's orbit does not allow it to get closer than 50 million miles (80 million kilometers) of Earth's orbit, so the asteroid seldom gets close enough to Earth to become easily detectable. However, NASA-supported telescopic surveys are now covering more sky and looking "deeper" than they ever have before, and in fact, 2013 US10 was first detected where it spends much of its time, well beyond the orbit of Jupiter.

The third of the recent discoveries is the approximately 1.2-kilometer (two-kilometer) near-Earth asteroid 2013 UP8, found on October 25 by the Pan-STARRS group in Hawaii. This asteroid can approach quite close to Earth's orbit, within 3.4 million miles (5.5 million kilometers), which makes it a "potentially hazardous asteroid" (PHA). 2013 UP8 is in the top 5th percentile of the largest PHAs, most of which were found much earlier during NASA's asteroid survey program. Like the other new discoveries, this asteroid has gone undetected for a long time because it has not approached Earth closely for decades. But the increasingly capable NASA-supported asteroid surveys finally found this object while it was still at a large distance from Earth, well beyond the orbit of Mars.

Update: Near-Earth Object 2013 US10 is a Long-Period Comet

While initial reports from the Minor Planet Center in Cambridge, Massachusetts, categorized object 2013 US10 as a very large near-Earth asteroid, new observations now indicate that it is, in fact, a long-period comet, and it is now designated C/2013 US10 (Catalina). The comet was discovered by the Catalina Sky Survey near Tucson, Arizona, on Oct. 31, 2013, and linked to earlier pre-discovery Catalina observations made on September 12. The initial orbit suggested this object is a large, short period, near-Earth asteroid, as reported here yesterday. An updated orbit, issued today by the Minor Planet Center, removed the September 12 observations that belong to another object and include earlier pre-discovery August and September observations made by the Catalina Sky Survey, the ISON-HD observatory in Russia and Hawaii's Pan-STARRS group. The new orbit indicates that this object is in a long-period, near parabolic orbit about the sun. Furthermore, observations made last night at the Canada-France-Hawaii telescope indicate the object is showing modest cometary activity, which means that yesterday's rough estimate for the object's size (about 12 miles, or 20 kilometers) must now be completely revised. A new size estimate is not yet available, but the object could very well be much smaller than yesterday's estimate.

Illustration credit: NASA/JPL-Caltech

Artist's Concept of Merging Black Holes

Merging black holes ripple space and time in this artist's concept. Pulsar-timing arrays -- networks of the pulsing cores of dead stars -- are one strategy for detecting these ripples, or gravitational waves, thought to be generated when two supermassive black holes merge into one.

Throughout our universe, tucked inside galaxies far, far away, giant black holes are pairing up and merging. As the massive bodies dance around each other in close embraces, they send out gravitational waves that ripple space and time themselves, even as the waves pass right through our planet Earth.

Scientists know these waves, predicted by Albert Einstein's theory of relativity, exist but have yet to directly detect one. In the race to catch the waves, one strategy -- called pulsar-timing arrays -- has reached a milestone not through detecting any gravitational waves, but in revealing new information about the frequency and strength of black hole mergers.

"We expect that many gravitational waves are passing through us all the time, and now we have a better idea of the extent of this background activity," said Sarah Burke-Spolaor, co-author of a new Science paper published October 18, which describes research she contributed to while based at NASA's Jet Propulsion Laboratory in Pasadena, California. Burke-Spolaor is now at the California Institute of Technology in Pasadena.

Gravitational waves, if detected, would reveal more information about black holes as well as one of the four fundamental forces of nature: gravity.

The team's inability to detect any gravitational waves in the recent search actually has its own benefits, because it reveals new information about supermassive black hole mergers -- their frequency, distance from Earth and masses. One theory of black hole growth to hit the theorists' cutting room floors had stated that mergers alone are responsible for black holes gaining mass.

The results come from the Commonwealth Scientific and Industrial Research Organization's (CSIRO) Parkes radio telescope in eastern Australia. The study was jointly led by Ryan Shannon of CSIRO, and Vikram Ravi, of the University of Melbourne and CSIRO.

Pulsar-timing arrays are designed to catch the subtle gravitational waves using telescopes on the ground, and spinning stars called pulsars. Pulsars are the burnt-out cores of exploded stars that send out beams of radio waves like lighthouse beacons. The timing of the pulsars' rotation is so precise that researchers say they are akin to atomic clocks.

When gravitational waves pass through an array of multiple pulsars, 20 in the case of the new study, they set the pulsars bobbing like buoys. Researchers recording the radio waves from the pulsars can then piece together the background hum of waves.

"The gravitational waves cause the space between Earth and pulsars to stretch and squeeze," said Burke-Spolaor.

The new study used the Parkes Pulsar Timing Array, which got its start in the 1990s. According to the research team, the array, at its current sensitivity, will be able to detect a gravitational wave within 10 years.

Researchers at JPL are currently developing a similar precision pulsar-timing capability for NASA's Deep Space Network, a system of large dish antennas located around Earth that tracks and communicates with deep-space spacecraft. During gaps in the network's tracking schedules, the antennas can be used to precisely measure the timing of pulsars' radio waves. Because the Deep Space Network's antennas are distributed around the globe, they can see pulsars across the whole sky, which improves sensitivity to gravitational waves.

"Right now, the focus in the pulsar-timing array communities is to develop more sensitive technologies and to establish long-term monitoring programs of a large ensemble of the pulsars," said Walid Majid, the principal investigator of the Deep Space Network pulsar-timing program at JPL. "All the strategies for detecting gravitational waves, including LIGO [Laser Interferometer Gravitational-Wave Observatory], are complementary, since each technique is sensitive to detection of gravitational waves at very different frequencies. While some might characterize this as a race, in the end, the goal is to detect gravitational waves, which will usher in the beginning of gravitational wave astronomy. That is the real exciting part of this whole endeavor."

The ground-based LIGO observatory is based in Louisiana and Washington. It is a joint project of Caltech and the Massachusetts Institute of Technology, Cambridge, Massachusetts, with funding from the National Science Foundation. The European Space Agency is developing the space-based LISA Pathfinder (Laser Interferometer Space Antenna), a proof-of-concept mission for a future space observatory to detect gravitational waves. LIGO, LISA and pulsar-timing arrays would all detect different frequencies of gravitational waves and thus are sensitive to various types of merger events.

A video about the new Parkes findings from Swinburne University of Technology in Melbourne, Australia, is online at: http://astronomy.swin.edu.au/production/blackhole/.

Text credit: NASA/JPL-Caltech; image credit: Swinburne Astronomy Productions

New Galaxy Found Through AllWISE Program

The new AllWISE catalog will bring distant galaxies that were once invisible out of hiding, as illustrated in this image.

NASA's AllWISE project is providing the astronomy community with new and improved images and data taken by NASA's Wide-field Infrared Survey Explorer, or WISE, which surveyed the skies in infrared light in 2010. This is the first time that data from the entire mission so far, including two full scans of the sky, has been fully processed and made available to the public. The new catalog includes three-quarters of a billion objects, and will help with studies of nearby stars and galaxies.

The image on the right shows a portion of the sky available before the AllWISE project; the left image shows the same part of the sky in a new AllWISE image. The circle shows where a galaxy that might have gone undetected before now stands out. (The light we are seeing from this galaxy left the object 8 billion years ago, when the universe was only about 5 billion years old.) Images taken during the second sky scan were stacked up, thereby doubling the exposure time and revealing objects like this galaxy.

The image was taken at a wavelength of 4.6 microns.

Image credit: NASA/JPL-Caltech/UCLA

Note: For more information, see WISE Catalog Just Got Wiser.

Himiko Galaxies

The big blob-like structure shown here, named Himiko after the legendary ancient queen of Japan, turns out to be three galaxies thought to be in the process of merging into one. In this image, infrared data from NASA's Spitzer Space Telescope are red; visible data from NASA's Hubble Space Telescope are green; and ultraviolet data from Japan's Subaru telescope on Mauna Kea, Hawaii are blue.

Himiko is located nearly 13 billion light-years from Earth, dating back to a time when galaxies were first forming.

Image credit: NASA/JPL-Caltech/STScI/NAOJ/Subaru

Note: For more information, see Infant Galaxies Merge Near 'Cosmic Dawn'.

Virtual Guide to the Milky Way

This virtual journey shows the different components that make up our home galaxy, the Milky Way, which contains about a hundred billion stars.

It starts at the black hole at the center of the Milky Way and with the stars that orbit around it, before zooming out through the central Galactic Bulge, which hosts about ten billion stars.

The journey continues through a younger population of stars in the stellar disc, home to most of the Milky Way's stars, and which is embedded in a slightly larger gaseous disc. Stars in the disc are arranged in a spiral arm pattern and orbit the center of the Galaxy.

The discs and bulge are embedded in the stellar halo, a spherical structure that consists of a large number of globular clusters – the oldest population of stars in the Galaxy – as well as many isolated stars. An even larger halo of invisible dark matter is inferred by its gravitational effect on the motions of stars in the Galaxy.

Looking at a face-on view of the Galaxy we see the position of our Sun, located at a distance of about 26,000 light-years from the Galactic Center.

Finally, the extent of the stellar survey conducted by ESA’s Hipparcos mission is shown, which surveyed more than 100,000 stars up to 300 light-years away from the Sun. In comparison, ESA’s Gaia survey will study one billion stars out to 30,000 light-years away.

Video credit: ESA

Sagittarius A*

Sagittarius A*: The supermassive black hole at the center of the Milky Way.

New evidence has been uncovered for the presence of a jet of high-energy particles blasting out of the Milky Way's supermassive black hole known as Sagittarius A* (Sgr A*). This image of Sgr A* and the region around it contains some of the data used in the study, with X-rays from Chandra (purple) and radio emission from the Very Large Array (blue). Jets of high-energy particles are found throughout the Universe on large and small scales. The likely discovery of a jet from Sgr A* helps astronomers learn more about the giant black hole, including how it is spinning.

Scale: Image is 1.2 arcmin across. (about 9 light years).

Image credit: X-ray: NASA/CXC/UCLA/Z.Li et al; Radio: NRAO/VLA

Note: For more information, see Sagittarius A*: New Evidence For A Jet From Milky Way's Black Hole.

NGC 5044

Galaxies are social beasts that are mostly found in groups or clusters – large assemblies of galaxies that are permeated by even larger amounts of diffuse gas. With temperatures of 10 million degrees or more, the gas in galaxy groups and clusters is hot enough to shine brightly in X-rays and be detected by ESA’s XMM-Newton X-ray observatory.

As galaxies speed through these gigantic cauldrons, they occasionally jumble the gas and forge it into lop-sided shapes. An example is revealed in this composite image of the galaxy group NGC 5044, the brightest group in X-rays in the entire sky.

The group is named after the massive and bright elliptical galaxy at its center, surrounded by tens of smaller spiral and dwarf galaxies. The galaxies are shown in a combination of optical images from the Digitized Sky Survey with infrared and ultraviolet images from NASA’s WISE and Galex satellites, respectively. Foreground stars are also sprinkled across the image.

The large blue blob shows the distribution of hot gas filling the space between NGC 5044’s galaxies as imaged by XMM-Newton. From the X-ray observations, astronomers can also see the glow of iron atoms that were forged in stellar explosions within the galaxies of the group but streamed beyond. The distribution of iron atoms is shown in purple.

Embedded within the hot gas are clouds of even more energetic plasma that emit radio waves – a reminder of the past activity of a supermassive black hole lurking at the center of the group. These are the green filament extending from the central galaxy to the lower right and the larger green region to its lower left, which were imaged with the Giant Metrewave Radio Telescope, near Pune in India.

The distribution of the intergalactic gas and its ingredients is asymmetric, with a larger splotch in the upper right part of the image and a smaller one in the lower left.

Astronomers believe that gas in NGC 5044 is sloshing as a consequence of a galaxy that passed through it several millions of years ago. The culprit is the spiral galaxy NGC 5054, which is not visible here, instead hiding beyond its lower left corner.

The transit of NGC 5054 through the center of the group may have also caused the twisted shape of the radio-bright filament.

This image was first published in the XMM-Newton Image Gallery in October 2013. The analysis is reported in the paper by E. O’Sullivan et al. “The impact of sloshing on the intra-group medium and old radio lobe of NGC 5044.”

Image credit: E. O’Sullivan & ESA

UGC 10288

The edge-on spiral galaxy UGC 10288 appeared to be a single object in previous observations. However, new detailed radio data from the NRAO's Jansky Very Large Array (VLA) revealed that the large perpendicular extension of UGC 10288's halo (blue) is really a distant background galaxy with radio jets.

This image of UGC 10288 in the foreground is created with data spanning optical, infrared and radio energies. Radio data are blue, and infrared observations from NASA's Spitzer Space Telescope and Wide-field Infrared Survey Explorer (WISE) are yellow and orange, respectively. Optical data from the Sloan Digital Sky Survey are purplish blue and show starlight; and optical data from the Kitt Peak National Observatory are rose and show heated gas.

Image credit: NASA/JPL-Caltech/NRAO/SDSS/NOAO/University of Manitoba

Note: For more information, see Nature Pulls a Fast One on Astronomers.

Supernova Remnant Cassiopeia A

Cassiopeia A: A supernova remnant located about 10,000 light years from Earth.

This new version of Chandra's image of the Cassiopeia A supernova remnant has been specially processed to show with better clarity the appearance of Cas A in different bands of X-rays. This will aid astronomers in their efforts to reconstruct details of the supernova process such as the size of the star, its chemical makeup, and the explosion mechanism. The color scheme used in this image is the following: low-energy X-rays are red, medium-energy ones are green, and the highest-energy X-rays detected by Chandra are colored blue.

Scale: Image is 8.91 arcmin across (about 29 light years).

Image credit: NASA/CXC/SAO

Note: For more information, see Cassiopeia A: Exploring the Third Dimension of Cassiopeia A.

Messier 15

This cluster of stars is known as Messier 15, and is located some 35,000 light-years away in the constellation of Pegasus (The Winged Horse). It is one of the oldest globular clusters known, with an age of around 12 billion years.

Both very hot blue stars and cooler golden stars can be seen swarming together in the image, becoming more concentrated towards the cluster's bright center. Messier 15 is one of the densest globular clusters known, with most of its mass concentrated at its core. As well as stars, Messier 15 was the first cluster known to host a planetary nebula, and it has been found to have a rare type of black hole at its center.

This new image is made up of observations from Hubble's Wide Field Camera 3 and Advanced Camera for Surveys in the ultraviolet, infrared, and optical parts of the spectrum.

Photo credit: NASA, ESA

Note: For more information, see Hubble Views an Old and Mysterious Cluster.

NGC 4038/4039 - The Antennae Galaxies

The NASA/ESA Hubble Space Telescope has snapped the best ever image of the Antennae Galaxies. Hubble has released images of these stunning galaxies twice before, once using observations from its Wide Field and Planetary Camera 2 (WFPC2) in 1997, and again in 2006 from the Advanced Camera for Surveys (ACS). Each of Hubble’s images of the Antennae Galaxies has been better than the last, due to upgrades made during the famous servicing missions, the last of which took place in 2009.

The galaxies — also known as NGC 4038 and NGC 4039 — are locked in a deadly embrace. Once normal, sedate spiral galaxies like the Milky Way, the pair have spent the past few hundred million years sparring with one another. This clash is so violent that stars have been ripped from their host galaxies to form a streaming arc between the two. In wide-field images of the pair the reason for their name becomes clear — far-flung stars and streamers of gas stretch out into space, creating long tidal tails reminiscent of antennae.

This new image of the Antennae Galaxies shows obvious signs of chaos. Clouds of gas are seen in bright pink and red, surrounding the bright flashes of blue star-forming regions — some of which are partially obscured by dark patches of dust. The rate of star formation is so high that the Antennae Galaxies are said to be in a state of starburst, a period in which all of the gas within the galaxies is being used to form stars. This cannot last forever and neither can the separate galaxies; eventually the nuclei will coalesce, and the galaxies will begin their retirement together as one large elliptical galaxy.

This image uses visible and near-infrared observations from Hubble’s Wide Field Camera 3 (WFC3), along with some of the previously-released observations from Hubble’s Advanced Camera for Surveys (ACS).

Photo credit: ESA/Hubble & NASA

Black Hole with Accretion Disk and Binary Jets

Artist's impression of a black hole feasting on matter from its companion star in a binary system. Matter flows from the star towards the black hole and forms an accretion disc with a temperature so high that it emits X-rays. The black hole can be a fussy eater: instead of swallowing all of the material, it sometimes pushes a fraction of it away in the form of two powerful jets of particles.

A team of astronomers studying the jets of the binary system 4U1630-47 have confirmed that black hole jets not only consist of electrons but also contain heavier particles, like protons or atomic nuclei. This means that jets can carry mass and energy away from the black hole in much larger amounts than previously thought.

Illustration credit: ESA/ATG Medialab

Note: For more information, see Black Hole Boasts Heavyweight Jets and Black Hole with Disc and Jets.

NGC 3572

The Wide Field Imager on the MPG/ESO 2.2-meter telescope at ESO’s La Silla Observatory in Chile has captured the best image so far of the star cluster NGC 3572, a gathering of young stars, and its spectacular surroundings. This new image shows how the clouds of gas and dust around the cluster have been sculpted into whimsical bubbles, arcs and the odd features known as elephant trunks by the stellar winds flowing from the bright stars. The brightest of these cluster stars are heavier than the Sun and will end their short lives as supernova explosions.

Image credit: ESO/G. Beccari

Note: For more information, see Young Stars Paint Spectacular Stellar Landscape.

Saturn, with Earth, Venus and Mars

On July 19, 2013, in an event celebrated the world over, NASA's Cassini spacecraft slipped into Saturn's shadow and turned to image the planet, seven of its moons, its inner rings -- and, in the background, our home planet, Earth.

With the sun's powerful and potentially damaging rays eclipsed by Saturn itself, Cassini's onboard cameras were able to take advantage of this unique viewing geometry. They acquired a panoramic mosaic of the Saturn system that allows scientists to see details in the rings and throughout the system as they are backlit by the sun. This mosaic is special as it marks the third time our home planet was imaged from the outer solar system; the second time it was imaged by Cassini from Saturn's orbit; and the first time ever that inhabitants of Earth were made aware in advance that their photo would be taken from such a great distance.

With both Cassini's wide-angle and narrow-angle cameras aimed at Saturn, Cassini was able to capture 323 images in just over four hours. This final mosaic uses 141 of those wide-angle images. Images taken using the red, green and blue spectral filters of the wide-angle camera were combined and mosaicked together to create this natural-color view. A brightened version with contrast and color enhanced (Figure 1), a version with just the planets annotated (Figure 2), and an annotated version (Figure 3) are shown above.

This image spans about 404,880 miles (651,591 kilometers) across.

The outermost ring shown here is Saturn's E ring, the core of which is situated about 149,000 miles (240,000 kilometers) from Saturn. The geysers erupting from the south polar terrain of the moon Enceladus supply the fine icy particles that comprise the E ring; diffraction by sunlight gives the ring its blue color. Enceladus (313 miles, or 504 kilometers, across) and the extended plume formed by its jets are visible, embedded in the E ring on the left side of the mosaic.

At the 12 o'clock position and a bit inward from the E ring lies the barely discernible ring created by the tiny, Cassini-discovered moon, Pallene (3 miles, or 4 kilometers, across). (For more on structures like Pallene's ring, see PIA08328). The next narrow and easily seen ring inward is the G ring. Interior to the G ring, near the 11 o'clock position, one can barely see the more diffuse ring created by the co-orbital moons, Janus (111 miles, or 179 kilometers, across) and Epimetheus (70 miles, or 113 kilometers, across). Farther inward, we see the very bright F ring closely encircling the main rings of Saturn.

Following the outermost E ring counter-clockwise from Enceladus, the moon Tethys (662 miles, or 1,066 kilometers, across) appears as a large yellow orb just outside of the E ring. Tethys is positioned on the illuminated side of Saturn; its icy surface is shining brightly from yellow sunlight reflected by Saturn. Continuing to about the 2 o'clock position is a dark pixel just outside of the G ring; this dark pixel is Saturn's Death Star moon, Mimas (246 miles, or 396 kilometers, across). Mimas appears, upon close inspection, as a very thin crescent because Cassini is looking mostly at its non-illuminated face.

The moons Prometheus, Pandora, Janus and Epimetheus are also visible in the mosaic near Saturn's bright narrow F ring. Prometheus (53 miles, or 86 kilometers, across) is visible as a faint black dot just inside the F ring and at the 9 o'clock position. On the opposite side of the rings, just outside the F ring, Pandora (50 miles, or 81 kilometers, across) can be seen as a bright white dot. Pandora and Prometheus are shepherd moons and gravitational interactions between the ring and the moons keep the F ring narrowly confined. At the 11 o'clock position in between the F ring and the G ring, Janus (111 miles, or 179 kilometers, across) appears as a faint black dot. Janus and Prometheus are dark for the same reason Mimas is mostly dark: we are looking at their non-illuminated sides in this mosaic. Midway between the F ring and the G ring, at about the 8 o'clock position, is a single bright pixel, Epimetheus. Looking more closely at Enceladus, Mimas and Tethys, especially in the brightened version of the mosaic, one can see these moons casting shadows through the E ring like a telephone pole might cast a shadow through a fog.

In the non-brightened version of the mosaic, one can see bright clumps of ring material orbiting within the Encke gap near the outer edge of the main rings and immediately to the lower left of the globe of Saturn. Also, in the dark B ring within the main rings, at the 9 o'clock position, one can see the faint outlines of two spoke features, first sighted by NASA's Voyager spacecraft in the early 1980s and extensively studied by Cassini.

Finally, in the lower right of the mosaic, in between the bright blue E ring and the faint but defined G ring, is the pale blue dot of our planet, Earth. Look closely and you can see the moon protruding from the Earth's lower right. (For a higher resolution view of the Earth and moon taken during this campaign, see PIA14949.) Earth's twin, Venus, appears as a bright white dot in the upper left quadrant of the mosaic, also between the G and E rings. Mars also appears as a faint red dot embedded in the outer edge of the E ring, above and to the left of Venus.

For ease of visibility, Earth, Venus, Mars, Enceladus, Epimetheus and Pandora were all brightened by a factor of eight and a half relative to Saturn. Tethys was brightened by a factor of four. In total, 809 background stars are visible and were brightened by a factor ranging from six, for the brightest stars, to 16, for the faintest. The faint outer rings (from the G ring to the E ring) were also brightened relative to the already bright main rings by factors ranging from two to eight, with the lower-phase-angle (and therefore fainter) regions of these rings brightened the most. The brightened version of the mosaic was further brightened and contrast-enhanced all over to accommodate print applications and a wide range of computer-screen viewing conditions.

Some ring features -- such as full rings traced out by tiny moons -- do not appear in this version of the mosaic because they require extreme computer enhancement, which would adversely affect the rest of the mosaic. This version was processed for balance and beauty.

This view looks toward the unlit side of the rings from about 17 degrees below the ring plane. Cassini was approximately 746,000 miles (1.2 million kilometers) from Saturn when the images in this mosaic were taken. Image scale on Saturn is about 45 miles (72 kilometers) per pixel.

This mosaic was made from pictures taken over a span of more than four hours while the planets, moons and stars were all moving relative to Cassini. Thus, due to spacecraft motion, these objects in the locations shown here were not in these specific places over the entire duration of the imaging campaign. Note also that Venus appears far from Earth, as does Mars, because they were on the opposite side of the sun from Earth.

Image credit: NASA/JPL-Caltech/SSI

Note: For more information, see NASA Cassini Spacecraft Provides New View of Saturn and Earth, PIA17679: The Faces of 'Wave at Saturn' and Spectacular New View of Saturn and Earth. From earlier in the year, see Cassini to Photograph Earth From Deep Space and Cassini Releases Image of Earth Waving at Saturn.

HH 46/47

Combined observations from NASA's Spitzer Space Telescope and the newly completed Atacama Large Millimeter/submillimeter Array (ALMA) in Chile have revealed the throes of stellar birth, as never before, in the well-studied object known as HH 46/47.

Herbig-Haro (HH) objects form when jets shot out by newborn stars collide with surrounding material, producing small, bright, nebulous regions. To our eyes, the dynamics within many HH objects are obscured by enveloping gas and dust. But the infrared and submillimeter light seen by Spitzer and ALMA, respectively, pierces the dark cosmic cloud around HH 46/47 to let us in on the action. (Infrared light has longer wavelengths than what we see with our eyes, and submillimeter light has even longer wavelengths.)

In this image, the shorter-wavelength light appears blue and longer-wavelength light, red. Blue shows gas energized by the outflowing jets. The green colors trace a combination of hydrogen gas molecules and dust that follows the boundary of the gas cloud cocooning the young star. The reddish-colored areas, created by excited carbon monoxide gas, reveal that the gas in the two lobes blown out by the star's jets is expanding faster than previously thought. This faster expansion has an influence on the overall amount of turbulence in the gaseous cloud that originally spawned the star. In turn, the extra turbulence could have an impact on whether and how other stars might form in this gaseous, dusty, and thus fertile, ground for star-making.

Image credit: NASA/JPL-Caltech/ALMA

Note: For more information, see Spitzer and ALMA Reveal a Star's Bubbly Birth.

Map of Rock Properties at Vesta

This colorized map from NASA's Dawn mission shows the types of rocks and minerals distributed around the surface of the giant asteroid Vesta. In this color scheme, red shows diogenite, a type of mineral thought to be formed through magmatic processes deep in the crust. Green shows howardite, a type of surface rock that is made of broken bits of different materials that are excavated, ejected and mixed by meteor impacts. These types of rocks are the most abundant observed on Vesta's surface. Blue shows eucrite, a type of rock formed in the crust of Vesta that isn't as deep down as diogenite. For example, Vesta's equatorial region is replete with eucrites. Yellow areas show regions with diogenite and howardite. The yellow and red areas have large quantities of the magnesium-and silicate-rich mineral diogenite, especially in the southern hemisphere. Cyan areas show regions with eucrite and howardite. Many howardite, eucrite and diogenite meteorites have been found on Earth, and earlier work from Dawn confirmed theories that they came from Vesta.

The location of two craters, Arruntia and Bellicia, are noted in the annotated version. At these craters, scientists unexpectedly found the mineral olivine. The outlines of the giant craters Rheasilvia and Veneneia are also noted. Scientists thought they'd find olivine in those locations but have not.

The data for this map were obtained by Dawn's visible and infrared mapping spectrometer (VIR) during Dawn's orbital measurements of Vesta from 2011 to 2012.

Image credit: NASA/JPL-Caltech/UCLA/ASI/INAF

Note: For more information, see PIA17476: Two Craters with Olivine, PIA17477: Contrast-Enhanced Image of Bellicia Crater, PIA17478: Bellicia Crater, in Visible Light, and It's Complicated: Dawn Spurs Rewrite of Vesta's Story.

Hubble Frontier Fields

These (image above) are NASA Hubble Space Telescope natural-color images of four target galaxy clusters that are part of an ambitious new observing program called The Frontier Fields.

NASA's Hubble, Spitzer and Chandra space telescopes are teaming up to look deeper into the universe than ever before. With a boost from natural "zoom lenses" found in space, they should be able to uncover galaxies that are as much as 100 times fainter than what these three great observatories typically can see.

In an ambitious collaborative program called The Frontier Fields, astronomers will make observations over the next three years of six massive galaxy clusters, exploiting a natural phenomenon known as gravitational lensing, to learn not only what is inside the clusters but also what is beyond them. The clusters are among the most massive assemblages of matter known, and their gravitational fields can be used to brighten and magnify more distant galaxies so they can be observed.

"The Frontier Fields program is exactly what NASA's great observatories were designed to do; working together to unravel the mysteries of the Universe" said John Grunsfeld, associate administrator for NASA's Science Mission Directorate in Washington. "Each observatory collects images using different wavelengths of light with the result that we get a much deeper understanding of the underlying physics of these celestial objects."

The first object they will view is Abell 2744, commonly known as Pandora's Cluster. The giant galaxy cluster appears to be the result of a simultaneous pile-up of at least four separate, smaller galaxy clusters that took place over a span of 350 million years.

Astronomers anticipate these observations will reveal populations of galaxies that existed when the universe was only a few hundred million years old, but have not been seen before.

"The idea is to use nature's natural telescopes in combination with the great observatories to look much deeper than before and find the most distant and faint galaxies we can possibly see," said Jennifer Lotz, a principal investigator with the Space Telescope Science Institute (STScI) in Baltimore, Maryland.

Data from the Hubble and Spitzer space telescopes will be combined to measure the galaxies' distances and masses more accurately than either observatory could measure alone, demonstrating their synergy for such studies.

"We want to understand when and how the first stars and galaxies formed in the universe, and each great observatory gives us a different piece of the puzzle," said Peter Capak, the Spitzer principal investigator for the Frontier Fields program. "Hubble tells you which galaxies to look at and how many stars are being born in those systems. Spitzer tells you how old the galaxy is and how many stars have formed."

The Chandra X-ray Observatory also will peer deep into the star fields. It will image the clusters at X-ray wavelengths to help determine their mass and measure their gravitational lensing power, and identify background galaxies hosting supermassive black holes.

High-resolution Hubble data from the Frontier Fields program will be used to trace the distribution of dark matter within the six massive foreground clusters. Accounting for the bulk of the universe's mass, dark matter is the underlying invisible scaffolding attached to galaxies.

Hubble and Spitzer have studied other deep fields with great success. The Frontier Fields researchers anticipate a challenge because the distortion and magnification caused by the gravitational lensing phenomenon will make it difficult for them to understand the true properties of the background galaxies.

Image credit: NASA/ESA/J. Lotz & M. Mountain,STScI

Note: For more information, see NASA's Great Observatories Begin Deepest-Ever Probe of the Universe.

Boomerang Nebula

The Boomerang nebula, called the "coldest place in the universe," reveals its true shape to the Atacama Large Millimeter/submillimeter Array (ALMA) telescope. The background blue structure, as seen in visible light by NASA's Hubble Space Telescope, shows a classic double-lobe shape with a very narrow central region. ALMA's resolution and ability to see the cold gas molecules reveals the nebula's more elongated shape, as seen in red.

Image credit: NRAO/AUI/NSF/NASA/STScI/JPL-Caltech

Note: For more information, see Ghostly Specter Haunts the 'Coldest Place in the Universe'.

Six-Tailed Asteroid P/2013 P5

This NASA/ESA Hubble Space Telescope image reveals a never-before seen set of six comet-like tails radiating from a body in the asteroid belt.

Now designated P/2013 P5, the asteroid was discovered as an unusually fuzzy-looking object by astronomers using the Pan-STARRS survey telescope in Hawaii. The multiple tails were discovered in Hubble images taken on 10 September 2013.

When Hubble returned to the asteroid on 23 September its appearance had totally changed – it looked as if the entire structure had swung around.

One interpretation is that the asteroid’s spin has increased to the point where dust is being flung off the surface and escaping into space, where it is swept out into tails by the pressure of sunlight.

According to this theory, the asteroid’s rotation has been accelerated by the gentle push of sunlight. The tail’s structure suggests the object has been throwing off dust for at least five months.

These visible-light images were taken with Hubble’s Wide Field Camera 3. The asteroid is seen on the left as viewed on 10 September, and on the right as seen on 23 September.

Read the full news release.

Image credit: NASA, ESA, D. Jewitt (University of California, Los Angeles), J. Agarwal (Max Planck Institute for Solar System Research), H. Weaver (Johns Hopkins University Applied Physics Laboratory), M. Mutchler (STScI) & S. Larson (University of Arizona)

Note: For more information, see When is a Comet Not a Comet? and Hubble Sees an Asteroid with Six Comet-like Tails.

Silicate Worlds vs Carbon Worlds

This artist's concept illustrates the fate of two different planets: the one on the left is similar to Earth, made up largely of silicate-based rocks with oceans coating its surface. The one on the right is rich in carbon -- and dry. Chances are low that life as we know it, which requires liquid water, would thrive under such barren conditions.

New theoretical findings show that planetary systems with carbon-rich stars would host waterless rocky planets. On Earth, it is believed that icy asteroids and comets are the main suppliers of Earth's ocean. But, in star systems rich in carbon, the carbon would snag up oxygen to make carbon monoxide, leaving little oxygen to make water ice. In those systems, the asteroids and comets would be dry.

The most extreme carbon-rich stars, with much more carbon than our sun, are thought to create carbon-based planets, as depicted in this illustration. Those planets would lack oceans due to a lack of icy asteroids and comets serving as water reservoirs.

Illustration credit: NASA/JPL-Caltech

Note: For more information, see Carbon Worlds May be Waterless, Finds NASA Study.

Proba-2's View of the Hybrid Eclipse

Three partial solar eclipses are seen in this movie from ESA’s Proba-2 Sun-watching satellite as it dipped in and out of the Moon’s shadow during yesterday’s ‘hybrid’ solar eclipse.

A hybrid eclipse comprises a total solar eclipse and an ‘annular eclipse’, depending on an observer’s viewing location on Earth.

During a total solar eclipse, the Moon moves in front of the Sun as seen from Earth, their alignment and separation such that the much closer Moon appears large enough to block out the light from the much more distant Sun.

But from some locations, the apparent size of the Moon is slightly smaller than that of the Sun, leaving a bright ring around the dark disc of the Moon.

Meanwhile, from its vantage point in Earth orbit, Proba-2 saw several partial eclipses.

Proba-2 orbits Earth about 14.5 times per day, dipping in and out of the Moon’s shadow around the time of a solar eclipse.

The video was produced from images taken by Proba-2’s SWAP imager, which snaps the Sun in ultraviolet light. Stormy active regions on the Sun’s face are revealed, including sunspots, the roots of some large solar flares and ‘coronal mass ejections’ that are occasionally directed towards Earth.

Video credit: ESA

NGC 3377

New evidence from NASA's Wide-field Infrared Survey Explorer (WISE) and Galaxy Evolution Explorer (GALEX) missions provide support for the "inside-out" theory of galaxy evolution, which holds that star formation starts at the core of the galaxy and spreads outward.

In this image of a galaxy called NGC 3377, infrared light from WISE is colored red, and ultraviolet light from GALEX is green and blue. The center of the galaxy appears white, where all three wavelengths of light are present and add up. The outside of the galaxy is mostly ultraviolet light, and thus contains more blue and green. The dots in the picture are stars located in the foreground.

NGC 3377 is located 31 million light-years away in the constellation Leo. It is an older galaxy, having already exhausted its stellar fuel supply. The outer regions, while containing more young stars than the core, are bright in ultraviolet light due to a small population of older, extremely hot stars.

WISE and GALEX are both no longer operating, but scientists continue to access their bounties of data through public archives.

Image credit: NASA/JPL-Caltech

Note: For more information, see Galaxy Growth Examined Like Rings of a Tree.

IC 2118 - The Witch Head Nebula

A witch appears to be screaming out into space in this image from NASA's Wide-Field Infrared Survey Explorer, or WISE. The infrared portrait shows the Witch Head nebula, named after its resemblance to the profile of a wicked witch. Astronomers say the billowy clouds of the nebula, where baby stars are brewing, are being lit up by massive stars. Dust in the cloud is being hit with starlight, causing it to glow with infrared light, which was picked up by WISE's detectors.

The Witch Head nebula is estimated to be hundreds of light-years away in the Orion constellation, just off the famous hunter's knee.

WISE was recently "awakened" to hunt for asteroids in a program called NEOWISE. The reactivation came after the spacecraft was put into hibernation in 2011, when it completed two full scans of the sky, as planned.

Image credit: NASA/JPL-Caltech

Note: For more information, see 'Witch Head' Brews Baby Stars.

The Sun in Extreme Ultraviolet Light

Several large, active regions on the Sun burst out with about 20 eruptions between 25 and 28 October 2013. Some were flares; some were coronal mass ejections, and at least one was a prominence eruption.

This is an image of the Sun in extreme UV light from the Solar Dynamic Observatory superimposed on a visible-light image of the solar corona obtained with SOHO's C2 coronagraph. The still was taken on 26 October.

The Sun is about at its maximum level of activity in its 11-year solar cycle, so stormy stretches like this one are to be expected.

Image credit: ESA/NASA

Proxima Centauri

Shining brightly in this Hubble image is our closest stellar neighbor: Proxima Centauri.

Proxima Centauri lies in the constellation of Centaurus (The Centaur), just over four light-years from Earth. Although it looks bright through the eye of Hubble, as you might expect from the nearest star to the Solar System, Proxima Centauri is not visible to the naked eye. Its average luminosity is very low, and it is quite small compared to other stars, at only about an eighth of the mass of the Sun.

However, on occasion, its brightness increases. Proxima is what is known as a “flare star”, meaning that convection processes within the star’s body make it prone to random and dramatic changes in brightness. The convection processes not only trigger brilliant bursts of starlight but, combined with other factors, mean that Proxima Centauri is in for a very long life. Astronomers predict that this star will remain middle-aged — or a “main sequence” star in astronomical terms — for another four trillion years, some 300 times the age of the current Universe.

These observations were taken using Hubble’s Wide Field and Planetary Camera 2 (WFPC2). Proxima Centauri is actually part of a triple star system — its two companions, Alpha Centauri A and B, lie out of frame.

Although by cosmic standards it is a close neighbor, Proxima Centauri remains a point-like object even using Hubble’s eagle-eyed vision, hinting at the vast scale of the Universe around us.

Photo credit: ESA/Hubble & NASA

ATV-4 Albert Einstein Undocks From the ISS

ATV Albert Einstein backs away from the International Space Station shortly after undocking at 09:55 CET (08:55 UT) on 28 October 2013. Albert Einstein is the fourth in the series of ESA’s Automated Transfer Vehicles that delivers supplies to the Station, reboosts its orbit and frees up space on the orbital outpost when it undocks with waste. The spacecraft is scheduled to be sent into Earth’s atmosphere for a planned destructive re-entry over an uninhabited area of the south Pacific Ocean on 2 November.

Photo credit: ESA/NASA

Note: For more information, see ATV-4 Undocking, ATV-4 Free Flight, ATV-4 Over Earth, and ATV-4 Burn.