ARTEMIS Orbits a Magnetic Moon

Launched in 2007, NASA's five THEMIS spacecraft have now successfully completed their 2 year mission to determine the cause of geomagnetic substorms. Because they are continuing to work perfectly, NASA is re-directing the outermost two spacecraft to special orbits at and around the Moon. This new mission, which is called ARTEMIS, uses some very complex maneuvers over two years (2009-2010) to get both spacecraft into position.

As the Moon orbits the Earth, it passes in and out of the Earth's magnetic field and the million-mile per hour stream of particles emitted by the Sun known as the solar wind. While in these regions, the two ARTEMIS spacecraft will seek evidence for turbulence, particle acceleration, and magnetic reconnection, three fundamental phenomena that control the nature of the solar wind's interaction with the Earth's magnetosphere. Employing their full complement of instruments and unique two-point vantage points, the spacecraft will study the vacuum the Moon carves out in the solar wind, and the processes that eventually fill this lunar wake. Nearer the Moon, they will observe the effects of surface electric fields, ions sputtered off the lunar surface, and determine the internal structure of the Moon from transient variations in its magnetic field induced by external changes.

Video credit: NASA/Goddard Space Flight Center

Reflection Nebula IRAS 12116-6001 in Crux

NASA's Wide-field Infrared Survey Explorer, or WISE, captured this colorful image of the reflection nebula IRAS 12116-6001. This cloud of interstellar dust cannot be seen directly in visible light, but WISE's detectors observed the nebula at infrared wavelengths.

In images of reflection nebulae taken with visible light, clouds of dust reflect the light of nearby stars. The dust is warmed to relatively cool temperatures by the starlight and glows with infrared light, which WISE can detect. Reflection nebulae are of interest to astronomers because they are often the sites of new star formation.

The bright blue star on the right side of the image is the variable star Epsilon Crucis. In the Bayer system of stellar nomenclature, stars are given names based on their relative brightness within a constellation. The Greek alphabet is used to designate the star's apparent brightness compared to other stars in the same constellation. "Alpha" is the brightest star in the constellation, "beta" the second brightest, and so on. In this case, "epsilon" is the fifth letter of the Greek alphabet, so Epsilon Crucis is the fifth brightest star in the constellation Crux.

Crux is a well-known constellation that can be easily seen by observers in the Southern Hemisphere and from low northern latitudes. Also known as the Southern Cross, Crux is featured in many country's flags, including Australia, Brazil and New Zealand (although New Zealand's flag does not include Epsilon Crucis).

The colors used in this image represent specific wavelengths of infrared light. The blue color of Epsilon Crucis represents light emitted at 3.4 and 4.6 microns. The green-colored star seen beside Epsilon Crucis is emitting light at 12 microns. This star is IRAS 12194-6007, a carbon star that is near the end of its lifecycle. Since the infrared wavelengths emitted by this star are longer than those from Epsilon Crucis, it is cooler. The green and red colors seen in the reflection nebula represent 12- and 22-micron light coming from the nebula's dust grains warmed by nearby stars.

Photo credit: NASA/JPL-Caltech/UCLA

Future Star Movements in Omega Centauri

The multi-color snapshot (top), taken with the Wide Field Camera 3 aboard the NASA/ESA Hubble Space Telescope, captures the central region of the giant globular cluster Omega Centauri. All the stars in the image are moving in random directions, like a swarm of bees. Astronomers used Hubble's exquisite resolving power to measure positions for stars in 2002 and 2006.

From these measurements, they can predict the stars' future movement. The lower illustration charts the future positions of the stars highlighted by the white box in the top image. Each streak represents the motion of the stars over the next 600 years. The motion between the dots corresponds to 30 years.

Photo credit: NASA, ESA, J. Anderson and R. van der Marel (STScI)

Note: For more information, see Hubble Data Used to Look 10,000 Years into the Future.

Monoceros R2

This dramatic infrared image shows the nearby star formation region Monoceros R2, located some 2,700 light-years away in the constellation of Monoceros (the Unicorn). The picture was created from exposures in the near infrared bands Y, J and Ks taken by the VISTA survey telescope at ESO’s Paranal Observatory. Monoceros R2 is an association of massive hot young stars illuminating a beautiful collection of reflection nebulae, embedded in a large molecular cloud.

Photo credit: ESO/J. Emerson/VISTA. Acknowledgment: Cambridge Astronomical Survey Unit

Note: For more information and additional photos, see VISTA Reveals the Secret of the Unicorn.

Growing Galaxies Gently

New observations from ESO’s Very Large Telescope have, for the first time, provided direct evidence that young galaxies can grow by sucking in the cool gas around them and using it as fuel for the formation of many new stars. In the first few billion years after the Big Bang the mass of a typical galaxy increased dramatically and understanding why this happened is one of the hottest problems in modern astrophysics. The results appear in the 14 October issue of the journal Nature.

The first galaxies formed well before the Universe was one billion years old and were much smaller than the giant systems — including the Milky Way — that we see today. So somehow the average galaxy size has increased as the Universe has evolved. Galaxies often collide and then merge to form larger systems and this process is certainly an important growth mechanism. However, an additional, gentler way has been proposed.

A European team of astronomers has used ESO’s Very Large Telescope to test this very different idea — that young galaxies can also grow by sucking in cool streams of the hydrogen and helium gas that filled the early Universe and forming new stars from this primitive material. Just as a commercial company can expand either by merging with other companies, or by hiring more staff, young galaxies could perhaps also grow in two different ways — by merging with other galaxies or by accreting material.

The team leader, Giovanni Cresci (Osservatorio Astrofisico di Arcetri) says: “The new results from the VLT are the first direct evidence that the accretion of pristine gas really happened and was enough to fuel vigorous star formation and the growth of massive galaxies in the young Universe.” The discovery will have a major impact on our understanding of the evolution of the Universe from the Big Bang to the present day. Theories of galaxy formation and evolution may have to be re-written.

The group began by selecting three very distant galaxies to see if they could find evidence of the flow of pristine gas from the surrounding space and the associated formation of new stars. They were very careful to make sure that their specimen galaxies had not been disturbed by interactions with other galaxies. The selected galaxies were very regular, smoothly rotating discs, similar to the Milky Way, and they were seen about two billion years after the Big Bang (at a redshift of around three).

In galaxies in the modern Universe the heavy elements [1] are more abundant close to the center. But when Cresci’s team mapped their selected distant galaxies with the SINFONI spectrograph on the VLT [2] they were excited to see that in all three cases there was a patch of the galaxy, close to the center, with fewer heavy elements, but hosting vigorously forming stars, suggesting that the material to fuel the star formation was coming from the surrounding pristine gas that is low in heavy elements. This was the smoking gun that provided the best evidence yet of young galaxies accreting primitive gas and using it to form new generations of stars.

Notes:
[1] The gas filling the early Universe was almost all hydrogen and helium. The first generations of stars processed this primitive material to create heavier elements such as oxygen, nitrogen and carbon by nuclear fusion. When this material was subsequently spewed back into space by intense particle winds from massive young stars and supernova explosions the amounts of heavy elements in the galaxy gradually increased. Astronomers refer to elements other than hydrogen and helium as “heavy elements.”

[2] By carefully splitting up the faint light coming from a galaxy into its component colors using powerful telescopes and spectrographs, astronomers can identify the fingerprints of different chemicals in remote galaxies, and measure the amounts of heavy elements present. With the SINFONI instrument on the VLT astronomers can go one better and get a separate spectrum for each part of an object. This allows them to make a map that shows the quantity of heavy elements present in different parts of a galaxy and also determine where in the galaxy star formation is occurring most vigorously.

Illustration credit: ESO/L. Calçada

The Era of Reionization

Astronomers using ESO’s Very Large Telescope (VLT) have measured the distance to the most remote galaxy so far, UDFy-38135539, existing when the Universe was only about 600 million years old (a redshift of 8.6). At this early time, the Universe was not fully transparent and much of it was filled with a hydrogen fog that absorbed the fierce ultraviolet light from young galaxies. The transitional period when the fog was still being cleared by this ultraviolet light is known as the era of reionization, illustrated with this still from a representative scientific simulation (see Alvarez et al. (2009) for more details).

When the Universe cooled down after the Big Bang, about 13.7 billion years ago, electrons and protons combined to form neutral hydrogen gas. This cool dark gas was the main constituent of the Universe during the so-called Dark Ages, when there were no luminous objects. This phase eventually ended when the first stars formed and their intense ultraviolet radiation slowly made the hydrogen fog transparent again by splitting the hydrogen atoms back into electrons and protons, a process known as reionization. This epoch in the Universe’s early history lasted from about 150 million to 800 million years after the Big Bang. In this visualization, ionized regions are blue and translucent, ionization fronts are red and white, and neutral regions are dark and opaque.

The new study shows that the glow from UDFy-38135539 seems not to be strong enough on its own to clear out the hydrogen fog. There must be other galaxies, probably fainter and less massive nearby companions of UDFy-38135539, which also helped make the space around the galaxy transparent.

Illustration credit: M. Alvarez, R. Kaehler, and T. Abel

Furthest Galaxy (to date) UDFy-38135539

This image shows the infrared Hubble Ultra Deep Field taken by the NASA/ESA Hubble Space Telescope in 2009, in which several robust candidate distance-record-breaking objects were discovered. Confirming the distances to such faint and remote objects is however an enormous challenge and can only reliably be done using spectroscopy from very large ground-based telescopes by measuring the redshift of the galaxy’s light.

Astronomers using ESO’s Very Large Telescope (VLT) have now measured the distance to the most remote galaxy so far, UDFy-38135539 (the faint object shown in the excerpt on the left), which we see as it was when the Universe was only about 600 million years old (a redshift of 8.6). These are the first confirmed observations of a galaxy whose light is clearing the opaque hydrogen fog that filled the cosmos at this early time.

Photo credit: NASA, ESA, G. Illingworth (UCO/Lick Observatory and University of California, Santa Cruz) and the HUDF09 Team

Note: For more information, see Clearing the Cosmic Fog.

Ultraviolet Sun

This image shows the solar disc as observed by SOHO's Extreme Ultraviolet Imaging Telescope (EIT) at a wavelength of 171 Å, corresponding to emission lines by highly ionized iron atoms (Fe IX/X). This filter probes material in the lower corona, at a temperature of about 1 million Kelvin.

Spots and loops are clearly visible throughout the solar disc, yielding a lot of information about the Sun's magnetic field: loops correspond to closed magnetic field lines, whereas dark spots correspond to open magnetic field lines, extending into outer space.

Photo credit: ESA/NASA - SOHO/EIT

IC 5416 - The Cocoon Nebula

The aptly named Cocoon Nebula is featured in this image from NASA's Wide-field Infrared Survey Explorer, or WISE. This cloud of dust and gas, cataloged as IC 5416 and located in the constellation Cygnus, is wrapped in a dark cloud of dust called Barnard 168. Within this cocoon of dust and gas, new stars are forming and beginning to emerge into the wild.

In the heart of the nebula, which looks surprisingly like a Valentine's heart in WISE's view, massive new stars are emerging. The intense radiation from these stars heats up the cloud. The highest-energy light from the stars rips electrons from hydrogen atoms, which then recombine with the atoms and emit visible light.

Pictures of the Cocoon Nebula taken with visible light see only the inner most part of this cloud glowing red and surrounded by an eerie darkness. That darkness appears as an absence of stars, but it is actually a dense cloud of dust obscuring stars behind it. This dense cloud is being heated by the young stars within. The dust absorbs the high-energy radiation from the newborn stars and then glows in infrared light, captured by WISE in this view. The dusty cocoon extends over 45 light-years across, which is more than three times larger than the inner, glowing portion of the nebula.

The colors used in this image represent specific wavelengths of infrared light. Blue and cyan represent light emitted at wavelengths of 3.4 and 4.6 microns, which is predominantly from stars. Green and red represent light from 12 and 22 microns, respectively, which is mostly emitted by dust.

Photo credit: NASA/JPL-Caltech/UCLA

Light Curve of Upsilon Andromedae B

This graph of data from NASA's Spitzer Space Telescope shows how astronomers located a hot spot on a distant gas planet named Upsilon Andromedae b -- and learned that it was in the wrong place.

This planet -- termed an exoplanet because it orbits a star beyond our Sun -- whips around very closely to its star. It is tidally locked, meaning that one side always faces the star. One might think the hottest point of the planet would be smack dab in the middle of this sun-facing side, but previous research has shown that exoplanet hot spots can be offset, or over to the side, by up to 30 degrees.

This plot shows that the hot spot on Upsilon Andromedae b is even farther over to the side -- a whopping 80 degrees. Astronomers figured this out by measuring the total infrared light of the planet and star, as the planet orbits around. (The planet is not transiting or crossing in front of its star, so it doesn't block the star's light.) When the hot spot faces Earth, the total brightness of the system will go up, as measured by Spitzer's heat-seeking, infrared eyes.

The black line shows what the system's light variations, or light curve, would look like if the hot spot were in the middle of the sun-facing side of the planet. The yellow line shows what was actually observed: the light curve is offset by 80 degrees, indicating that the hot spot is, oddly, almost all the way over the side. Astronomers are not sure how this can be.

Illustration credit: NASA/JPL-Caltech/UCLA

Note: For more information on this planet, see PIA13493: Planetary Hot Spot Not Under the Glare of Star (Artist Concept) and PIA13494: Weird Warm Spot on Exoplanet (which includes a video).

The Coma Cluster: Planck vs. Rosat

These images of the Coma cluster (also known as Abell 1656), a very hot and nearby cluster of galaxies, show how it appears through the Sunyaev-Zel'dovich Effect (top left) and X-ray emission (top right).

The top-left panel shows the Sunyaev-Zel'dovich image of the Coma cluster produced by Planck, and the top-right panel shows the same cluster imaged in X-rays by the ROSAT satellite. The colors in both images map the intensity of the measured signals. The X-ray contours are also superimposed on the Planck image as a visual aid.

As a comparison, the images are shown superimposed on a wide-field optical image of the Coma cluster from the Digitized Sky Survey in the two lower panels.

Located at a distance of about 300 million light-years from us, the Coma cluster extends over more than two degrees on the sky, corresponding to over 4 times the angular size of the full Moon. This image of the Coma cluster highlights Planck's ability to observe objects on very large scales, thanks to its all-sky survey strategy.

The region depicted in each image is slightly larger than 2 degrees.

Photo credits: Planck image: ESA/ LFI & HFI Consortia; ROSAT image: Max-Planck-Institut für extraterrestrische Physik; DSS image: NASA, ESA, and the Digitized Sky Survey 2. Acknowledgment: Davide De Martin (ESA/Hubble)

Large-Scale Structure of the Universe

This illustration depicts the large-scale distribution of galaxies as seen by the Sloan Digital Sky Survey, an ambitious project that determined the distances of about one million galaxies.

The two cones on the left of the image are a three dimensional (3D) map of the galaxies with the Earth at the center. Going from the center to the upper/lower edges of the map, more and more distant galaxies are seen, up to distances of about 2 thousand million [billion] light years. The color of the galaxies is related to their luminosity. The clumpiness in the distribution of matter is clearly visible in this representation.

The panel on the right shows a two dimensional (2D) image of galaxies in a small region of the sky. The 3D map is computed by combining the information contained in 2D images such as this one with an estimate of the distances of each individual object visible in it, derived from their spectra.

Illustration credit: Sloan Digital Sky Survey Team, NASA, NSF, DOE

Asteroid P/2010 A2

Hubble Space Telescope images of the asteroid P/2010 A2 taken at eight epochs between 25 January and 29 May 2010 with the Wide Field Camera 3 (WFC3).

The morphology of P/2010 A2 appears to evolve slowly: this is mostly due to the recession of the object from Earth - their relative distance doubled from January to May - but also to slow, intrinsic changes in the object itself. Thanks to the superb resolution of Hubble's WPC3, this very slow evolution can be measured in order to characterize the object.

Originally suspected to be a main belt comet, this bizarre object is in fact the remnant of an asteroid collision that occurred around 10 February 2009, and the dust trail is debris from the impact.

In each panel, the image has been rotated so that the tail lies approximately horizontal. Each panel subtends 10 arcseconds in height. The images have 0.04 arcsecond pixels and are combinations of images with total integration times of about 2600 seconds through the F606W filter.

Photo credit: NASA, ESA and D. Jewitt (UCLA)



Video credit: NASA, ESA, and G. Bacon (STScI)

Notes: For more about this asteroid, see: Hubble and Rosetta Unmask Nature of Recent Asteroid Wreck, and Hubble Observes Aftermath of Possible Asteroid Collision.

Magnetar SGR 0418+5729

This illustration represents the recently discovered magnetar SGR 0418+5729.

Magnetars are pulsars (spinning neutron stars) characterized by long rotations periods, occasional episodes of extremely enhanced emission (about 10–100 times the usual value) and intense, short bursts of X-rays and gamma-rays; these highly energetic events are presumed to be powered by an intense magnetic field.

Unlike all other magnetars detected so far, SGR 0418+5729 has a relatively weak dipolar magnetic field, B<7.5 x 1012 Gauss, which is 2–3 orders of magnitude lower than the typical value for a magnetar. Astronomers deduce that the magnetar-like activity of SGR 0418+5729 is powered by a strong, internal magnetic field, B~5 x 1014 Gauss, which is undetectable by observations.

The curves converging at the poles of the magnetar represent the dipolar magnetic field lines, whereas the entangled lines inside the magnetar symbolize the internal magnetic field.

Illustration credit: European Space Agency

Notes: For more information, see Are Most Pulsars Really Magnetars in Disguise? The initials "SGR" stand for "Soft Gamma Repeater."

Derain Crater

In the center of this image is Derain, an impact crater first viewed during MESSENGER's second Mercury flyby and named in 2009. Derain has material within and surrounding the crater that is much darker than the neighboring terrain. In fact, the material associated with Derain appears to have the lowest reflectance yet identified on Mercury's surface. The dark deposits may be material with a mineralogical composition different from the majority of Mercury's visible surface, but more data are needed before any further insight into the composition can be gained. Observations to be acquired during MESSENGER's orbital mission phase will help to identify the uncommonly dark material at Derain and similar occurrences elsewhere on the planet.

Also visible in this image, to the southeast of Derain, is the rayed crater Berkel, which has dark material in its center and in a ring immediately surrounding it. In contrast, two neighboring craters to the north of Berkel have bright rays but lack dark halos. Why do some craters contain dark materials while others do not? MESSENGER's orbital data will be used to investigate that question and to improve our understanding of the nature and structure of Mercury's crust.

Date Acquired: October 6, 2008
Instrument: Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS)
Scale: Derain is 190 km in diameter (118 miles)

Photo credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

NGC 253 - The Sculptor Galaxy in Infrared

The Sculptor galaxy is shown in different infrared hues, in this new mosaic from NASA's Wide-field Infrared Survey Explorer, or WISE. This image is a composite of infrared light captured with all four of the space telescope's infrared detectors.

The red image shows the galaxy's active side. Infant stars are heating up their dusty cocoons, particularly in the galaxy's core, making the Sculptor galaxy burst with infrared light. This light -- color-coded red in this view -- was captured using WISE's longest-wavelength, 22-micron detector. The dusty burst of stars is so intense in the core that it generates diffraction spikes. Diffraction spikes are telescope artifacts normally seen only around very bright stars.

The green image reveals the galaxy's emerging young stars, concentrated in the core and spiral arms. Ultraviolet light from these hot stars is being absorbed by tiny dust or soot particles left over from their formation, making the particles glow with infrared light that has been color-coded green in this view. WISE can see this light with a detector designed to capture wavelengths of 12 microns.

The blue image was taken with the two shortest-wavelength detectors on WISE (3.4 and 4.6 microns). It shows stars of all ages, which can be found not just in the core and spiral arms, but throughout the galaxy.

The Sculptor galaxy, or NGC 253, was discovered in 1783 by Caroline Herschel, a sister and collaborator of the discoverer of infrared light, Sir William Herschel. It was named after the constellation in which it is found, and is part of a cluster of galaxies known as the Sculptor group. The Sculptor galaxy can be seen by observers in the southern hemisphere with a pair of good binoculars.

NGC 253 is an active galaxy, which means that a significant fraction of its energy output does not come from normal populations of stars within the galaxy. The extraordinarily high amount of star formation occurring in the nucleus of this galaxy has led astronomers to classify it as a "starburst" galaxy. At a distance of approximately 10.5 million light-years away, NGC 253 is the closest starburst galaxy to our Milky Way galaxy. However, the starburst alone cannot explain all the activity observed in the nucleus. One strong possibility is that a giant black hole lurks at the heart of it all, similar to the one that lies at the center of the Milky Way.

In late September of this year, after surveying the sky about one-and-a-half times, WISE exhausted its supply of the frozen coolant needed to chill its longest-wavelength detectors -- the 12- and 22-micron channels. The satellite is continuing to survey the sky with its two remaining detectors, focusing primarily on asteroids and comets. Read more about this survey, called the NEOWISE Post-Cryogenic mission, at:  http://www.jpl.nasa.gov/news/news.cfm?release=2010-320.

Photo credit: NASA/JPL-Caltech/UCLA

The Changing Face of the Sun Over One Solar Cycle

This image shows a sequence of snapshots of the Sun, taken each year over almost an entire, 11-year long solar cycle. The activity clearly peaks around the year 2001.

The images have been taken by SOHO's Extreme ultraviolet Imaging Telescope (EIT) at a wavelength of 284 Å, corresponding to the emission line of fourteen-times ionized iron atoms (Fe XV) and showing material at temperatures of about 2 million Kelvin.

Photo credit: ESA/NASA - SOHO/EIT

Pulsar Wind Nebula G327.1-1.1

G327.1-1.1 is the aftermath of a massive star that exploded as a supernova in the Milky Way galaxy. A highly magnetic, rapidly spinning neutron star called a pulsar was left behind after the explosion and is producing a wind of relativistic particles, seen in X-rays by Chandra and XMM-Newton (blue) as well as in the radio data (red and yellow). This structure is called a pulsar wind nebula. The likely location of the spinning neutron star is shown in the labeled version [below]. The large red circle shows radio emission from the blast wave, and the composite image also contains infrared data from the 2MASS survey (red, green, and blue) that show the stars in the field.

No clear explanation is yet known for the unusual nature of G327.1-1.1, including the off-center position of the pulsar wind nebula seen in the radio data and the comet-like shape of the X-ray emission. One possibility is that we are seeing the effects of a shock wave bouncing backwards off of the shell of material swept up by the blast wave produced by the explosion, the so-called "reverse shock" from the blast wave. The pulsar is moving upwards, away from the center of the explosion, but the pulsar wind nebula is being swept towards the bottom-left of the image by the reverse shock wave that is also traveling towards the bottom-left. The direction of the pulsar's motion and of the reverse shock are shown in the labeled version.

The X-ray observations allow scientists to estimate the energy released during the supernova explosion and the age of the remnant, as well as the amount of material being swept up as the blast wave from the explosion expands. The faint bubble that the pulsar appears to be creating may also be revealing the fresh pulsar wind being blown into the region cleared out by the reverse shock.

Photo credit: X-ray: NASA/CXC/SAO/T.Temim et al. and ESA/XMM-Newton Radio: SIFA/MOST and CSIRO/ATNF/ATCA; Infrared: UMass/IPAC-Caltech/NASA/NSF/2MASS

Vesta

NASA's Hubble Space Telescope snapped these images of the asteroid Vesta in preparation for the Dawn spacecraft's visit in 2011.

Each of the four Hubble images captures views of Vesta during its 5.34-hour rotation period. Hubble's sharp "eye" can see features as small as about 40 kilometers (25 miles) across in these images. Vesta was 211 million kilometers (131 million miles) from Earth when Hubble made the observations.

The images show the difference in brightness and color on the asteroid's surface. These characteristics hint at the large-scale features that the Dawn spacecraft will see when it visits the potato-shaped asteroid.

Vesta is somewhat like our Moon, with ancient lava beds (the dark patches) and powdery debris, the pulverized remains of impacts (the orange-colored areas). The flattened area on one end of Vesta, visible in the top row of images, is a giant impact crater formed by a collision billions of years ago. The crater is 460 kilometers (285 miles) across, which is close to Vesta's roughly 530-kilometer (330-mile) diameter. Vesta is about the size of Arizona.

Astronomers used the images, taken with Hubble's Wide Field Camera 3, to better determine Vesta's spin axis. Based on the Hubble observations, astronomers calculated a slightly different, and more precise, rotation axis for Vesta. The new calculation will change the pattern of sunlight expected to illuminate the asteroid when Dawn arrives.

Determining a more accurate spin axis for Vesta will also help scientists refine the Dawn spacecraft's orbit around the asteroid. Dawn will orbit the rocky object for a year, beginning in July 2011. The spacecraft will then travel to the dwarf planet Ceres, arriving in 2015.

Vesta is one of the largest of a reservoir of about 100,000 asteroids, the leftover material from the formation of our solar system planets 4.6 billion years ago.

Hubble has kept its "eye" on Vesta for more than 15 years, beginning in 1994. Hubble images of Vesta in 1997 helped astronomers discover the asteroid's immense impact crater.

Astronomers combined views of Vesta in near-ultraviolet and blue light to construct these images. The images were taken on February 25, 2010.

Photo credit: NASA/ESA/STScI/UMd

Update: NASA has released a short video of Vesta rotating on its axis; the animation is made up of 146 pictures taken by the Hubble Space Telescope. The Minister cannot upload this video onto this post, but the story about the video can be read here (PIA13427: A New Spin on Vesta), and the video can be watched here.

NGC 1365

A new image taken with the powerful HAWK-I camera on ESO’s Very Large Telescope at Paranal Observatory in Chile shows the beautiful barred spiral galaxy NGC 1365 in infrared light. NGC 1365 is a member of the Fornax cluster of galaxies, and lies about 60 million light-years from Earth.

NGC 1365 is one of the best known and most studied barred spiral galaxies and is sometimes nicknamed the Great Barred Spiral Galaxy because of its strikingly perfect form, with the straight bar and two very prominent outer spiral arms. Closer to the center there is also a second spiral structure and the whole galaxy is laced with delicate dust lanes.

This galaxy is an excellent laboratory for astronomers to study how spiral galaxies form and evolve. The new infrared images from HAWK-I are less affected by the dust that obscures parts of the galaxy than images in visible light (potw1037a) and they reveal very clearly the glow from vast numbers of stars in both the bar and the spiral arms. These data were acquired to help astronomers understand the complex flow of material within the galaxy and how it affects the reservoirs of gas from which new stars can form. The huge bar disturbs the shape of the gravitational field of the galaxy and this leads to regions where gas is compressed and star formation is triggered. Many huge young star clusters trace out the main spiral arms and each contains hundreds or thousands of bright young stars that are less than ten million years old. The galaxy is too remote for single stars to be seen in this image and most of the tiny clumps visible in the picture are really star clusters. Over the whole galaxy, stars are forming at a rate of about three times the mass of our Sun per year.

While the bar of the galaxy consists mainly of older stars long past their prime, many new stars are born in stellar nurseries of gas and dust in the inner spiral close to the nucleus. The bar also funnels gas and dust gravitationally into the very center of the galaxy, where astronomers have found evidence for the presence of a super-massive black hole, well hidden among myriads of intensely bright new stars.

NGC 1365, including its two huge outer spiral arms, spreads over around 200,000 light-years. Different parts of the galaxy take different times to make a full rotation around the core of the galaxy, with the outer parts of the bar completing one circuit in about 350 million years. NGC 1365 and other galaxies of its type have come to more prominence in recent years with new observations indicating that the Milky Way could also be a barred spiral galaxy. Such galaxies are quite common — two thirds of spiral galaxies are barred according to recent estimates, and studying others can help astronomers understand our own galactic home.

Photo credit: ESO/P. Grosbøl

Earth by SMART-1

This photo-montage shows a series of images taken with the AMIE camera on board SMART-1 during the second lunar total eclipse witnessed by the spacecraft.

This eclipse took place on 28 October 2004. At that time, SMART-1 was about 290,000 km away from Earth and at its farthest planned distance from the Moon of about 660,000 km. From its vantage point, SMART-1 could see and photograph, for the first time ever, both the Earth and Moon during a lunar eclipse.

The images of the Moon are shown here in a temporal sequence, from left to right. They were taken with the AMIE camera, in visible light, between 1:14 UTC and 4:44 UTC. The 'totality' phase, in the middle of the sequence when the Moon is completely inside the Earth’s shadow, lasted about an hour from 2:23 UTC and 3:24 UTC.

The images of the Earth shown here were taken just before and after the eclipse. The apparent relative size of the Earth and Moon, as shown in this picture, is exactly as seen by SMART-1.

The relative distance between the two bodies, however, is not to scale. In fact, the Earth and Moon were farther apart than the field of view of AMIE and could not simultaneously fit within a single image.

In reality, the physical size of the Earth is about 3.7 times larger than that of the Moon; their diameters are about 12,800 km and 3,500 km, respectively. As SMART-1 was farther away from the Moon than from Earth, the difference appears exaggerated.

Photo credit: ESA/SMART-1/AMIE

Rhea's Equator

These three enhanced-color views of an equatorial region on Saturn's moon Rhea were made from data obtained by NASA's Cassini spacecraft. The colors have been enhanced to show colorful splotches and bands on the icy moon's surface.

Rhea sports a chain of bluish splotches along the equator that appear where fresh, bluish ice has been exposed on older crater rims. Cassini imaging scientists recently reported that they did not see evidence in Cassini images of a ring around Rhea. However, scientists analyzing these enhanced-color views suggest the bluish material could have been exposed by the crash of orbiting material -- perhaps a ring -- to the surface of Rhea in the not too distant past.

These images were made by processing raw images obtained by Cassini's imaging cameras in September 2007. Scientists analyzed frames shot through visible-light, ultraviolet and infrared filters. The processing enhanced our views of these moons beyond what could be seen by the human eye.

The image on the left shows a composite image made from data in the infrared, green and ultraviolet filters. The middle view shows an image made from data analyzing the ratio of infrared to ultraviolet wavelengths, indicating the relative blueness of the features. The image on the right shows a color-coded topography, where purple is 0 elevation and pink is 6 kilometers (4 miles).

In each of these images, the view is centered on 0 degrees north latitude and 163 degrees west longitude. The area shown covers approximately 16,900 square kilometers (6,500 square miles).

Photo credit: NASA/JPL/SSI/LPI

Orion Nebula Proplyd Atlas

This atlas features 30 proplyds, or protoplanetary discs, that were recently discovered in the majestic Orion Nebula. Using the wide field channel on Hubble's Advanced Camera for Surveys (ACS), astronomers discovered a total of 42 new discs that could be the seeds of planetary systems to come.

Within the awe-inspiring, gaseous folds of Orion, researchers have identified two different types of discs around young and forming stars: those that lie close to the brightest star in the cluster (Theta 1 Orionis C) and those farther away from it. The bright star heats up the gas in the nearby discs, causing them to shine brightly. The discs that are farther away do not receive enough of the energetic radiation from the star to set the gas ablaze; thus, they can only be detected as dark silhouettes against the background of the bright nebula, as the dust that surrounds these discs absorbs background visible light. By studying these silhouetted discs, astronomers are better able to characterize the properties of the dust grains that are thought to bind together and possibly form planets like our own.

In the brighter discs the excited material produces many glowing cusps, which all face the bright star, but from our point of view are randomly oriented through the nebula, so we see some edge on, and others face on, for instance. Other interesting features enhance the look of these captivating objects, such as emerging jets of matter and shock waves. The dramatic shock waves are formed when the stellar wind from the nearby massive star collides with the gas in the nebula, sculpting boomerang shapes or arrows or even, in the case of 181-825, a space jellyfish!

It is relatively rare to see visible images of proplyds, but the high resolution and sensitivity of Hubble and the Orion Nebula's proximity to Earth allow for precise views of these potential planetary systems.

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The full set of individual images of the 30 proplyds can be accessed on the dedicated pages at the spacetelescope.org website. See the related link "Proplyd Atlas - Orion Nebula."

Photo credit: NASA/ESA and L. Ricci (ESO)