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Astronomers using NASA's Hubble Space Telescope have ruled out an alternate theory on the nature of dark energy after recalculating the expansion rate of the universe to unprecedented accuracy. The universe appears to be expanding at an ever-increasing rate, and one explanation is that the universe is filled with a dark energy that works in the opposite way of gravity. One alternative to that hypothesis is that an enormous bubble of relatively empty space eight billion light-years across surrounds our galactic neighborhood. If we lived near the center of this void, observations of galaxies being pushed away from each other at accelerating speeds would be an illusion. This hypothesis has been invalidated because astronomers have refined their current understanding of the universe's present expansion rate to an uncertainty of just 3.3 percent. The new measurement reduces the error margin by 30 percent over Hubble's previous best measurement in 2009. The results are reported in the April 1 issue of The Astrophysical Journal. Amongst the myriad stars in spiral galaxy NGC 5584, imaged in visible light with Hubble's Wide Field Camera 3 between January and April 2010, are pulsating stars called Cepheid variables and one recent Type Ia supernova, a special class of exploding stars. Astronomers used Cepheid variables and Type Ia supernovae as reliable distance markers to measure the universe's expansion rate. NGC 5584 lies 72 million light-years away in the constellation Virgo and was one of the eight galaxies astronomers studied to measure the universe's expansion rate. In those galaxies, astronomers analyzed more than 600 Cepheid variables, including 250 in NGC 5584. Cepheid variables pulsate at a rate matched closely by their intrinsic brightness, making them ideal for measuring distances to relatively nearby galaxies. Type Ia supernovae flare with the same brightness and are brilliant enough to be seen from relatively longer distances. Astronomers search for Type Ia supernovae in nearby galaxies containing Cepheid variables so they can compare true brightness of both types of stars. That brightness information is used to calibrate the measurement of Type Ia supernova in far-flung galaxies and calculate their distance from Earth. Once astronomers know accurate distances to galaxies near and far, they can determine the universe's expansion rate. View the full article

Adam Riess, an astronomer at the Space Telescope Science Institute (STScI) and a professor in physics and astronomy at The Johns Hopkins University, today was awarded the 2011 Einstein Medal by the Albert Einstein Society, located in Bern, Switzerland. The Society recognized him for leadership in the High-z Supernova Search Team's 1998 discovery that the expansion rate of the universe is accelerating, a phenomenon widely attributed to a mysterious, unexplained "dark energy" filling the universe. Riess will receive the medal at a ceremony in Bern in May 2011. View the full article

NASA's Hubble Space Telescope reveals a majestic disk of stars and dust lanes in this view of the spiral galaxy NGC 2841, which lies 46 million light-years away in the constellation of Ursa Major (The Great Bear). This image was taken in 2010 through four different filters on Hubble's Wide Field Camera 3. Wavelengths range from ultraviolet light through visible light to near-infrared light. View the full article

How far is far? And, when do you know when you get there? This is not a Dr. Seuss riddle, but the ultimate "final frontier" confronting astronomers. We are on the cusp of seeing nearly as far as we ever can into the universe of stars and galaxies. The question can be better phrased: How young is young? And how do you know when you've seen the earliest objects that ever existed? That's because the farther we look into space the further back into time we see. We're accustomed to instantaneous communications on Earth, but starlight carries a roaming fee. It takes billions of years for information to reach us from the remote universe. Now astronomers have pushed the Hubble Space Telescope to its limits by finding what they believe is the most distant object ever seen in the universe. Its light traveled 13.2 billion years to reach Hubble. The dim object is a compact galaxy of blue stars that existed 480 million years after the Big Bang, only four percent of the universe's current age. It is tiny. Astronomers were surprised to discover that these observations offer evidence that the rate at which the universe was forming stars grew precipitously in about a 200-million-year time span. This huge change in the rate of star birth means that if astronomers can probe a little further back in time they are going to see even more dramatic changes. This will require the power of the James Webb Space Telescope, the planned successor to Hubble, which will be launched later this decade. View the full article

These images by NASA's Hubble Space Telescope show off two dramatically different face-on views of the spiral galaxy M51, dubbed the Whirlpool Galaxy. The image at left, taken in visible light, highlights the attributes of a typical spiral galaxy, including graceful, curving arms, pink star-forming regions, and brilliant blue strands of star clusters. In the image at right, most of the starlight has been removed, revealing the Whirlpool's skeletal dust structure, as seen in near-infrared light. This new image is the sharpest view of the dense dust in M51. The narrow lanes of dust revealed by Hubble reflect the galaxy's moniker, the Whirlpool Galaxy, as if they were swirling toward the galaxy's core. These images will be presented on Jan. 13, 2011, at the American Astronomical Society meeting in Seattle, Wash. View the full article

Astronomers are finding that the idiom "can't see the forest for the trees" applies to the universe of galaxies as well. In a paper published today in the science journal Nature, an international team of astronomers predicts that foreground galaxies will affect images of extremely far galaxies. The gravitational fields of the foreground galaxies distort space like a funhouse mirror. This means that a significant fraction of far background galaxies will appear on the sky near foreground galaxies. The good news is that the remote galaxies will appear brighter because of a phenomenon called gravitational lensing. This will need to be factored in when astronomers plan to look for the farthest galaxies in the universe with the planned James Webb Space Telescope. View the full article

A ghostly, glowing, green blob of gas has become one of astronomy's great cosmic mystery stories. The space oddity was spied in 2007 by Dutch high-school teacher Hanny van Arkel while participating in the online Galaxy Zoo project. The cosmic blob, called Hanny's Voorwerp (Hanny's Object in Dutch), appears to be a solitary green island floating near a normal-looking spiral galaxy, called IC 2497. Since the discovery, puzzled astronomers have used a slew of telescopes, including X-ray and radio observatories, to help unwrap the mystery. Astronomers found that Hanny's Voorwerp is the only visible part of a 300-light-year-long gaseous streamer stretching around the galaxy. The greenish Voorwerp is visible because a searchlight beam of light from the galaxy's core illuminated it. This beam came from a quasar, a bright, energetic object that is powered by a black hole. An encounter with another galaxy may have fed the black hole and pulled the gaseous streamer from IC 2497. Now, with the help of NASA's Hubble Space Telescope, astronomers have uncovered a pocket of young star clusters (colored yellow-orange in the image) at the tip of the green-colored Hanny's Voorwerp. Hubble also shows that gas flowing from IC 2497 (the pinkish object with the swirling spiral arms) may have instigated the star birth by compressing the gas in Hanny's Voorwerp. View the full article

A survey of more than 200,000 stars in our Milky Way galaxy has unveiled the sometimes petulant behavior of tiny dwarf stars. These stars, which are smaller than the Sun, can unleash powerful eruptions called flares that may release the energy of more than 100 million atomic bombs. Red dwarfs are the most abundant stars in our universe and are presumably hosts to numerous planets. However, their erratic behavior could make life unpleasant, if not impossible, for many alien worlds. The flares the stars unleash would blast any planets orbiting them with ultraviolet light, bursts of X-rays, and a gush of charged particles called a stellar wind. Studying the light from 215,000 dwarfs collected in observations by NASA's Hubble Space Telescope, astronomers found 100 stellar flares. The observations, taken over a seven-day period, constitute the largest continuous monitoring of red dwarf stars ever undertaken. The illustration shows a red dwarf star unleashing a powerful flare. A hypothetical planet is in the foreground. View the full article

A delicate sphere of gas, photographed by NASA's Hubble Space Telescope, floats serenely in the depths of space. The pristine shell, or bubble, is the result of gas that is being shocked by the expanding blast wave from a supernova. Called SNR 0509-67.5 (or SNR 0509 for short), the bubble is the visible remnant of a powerful stellar explosion in the Large Magellanic Cloud (LMC), a small galaxy about 160,000 light-years from Earth. Ripples in the shell's surface may be caused by either subtle variations in the density of the ambient interstellar gas, or possibly driven from the interior by pieces of the ejecta. The bubble-shaped shroud of gas is 23 light-years across and is expanding at more than 11 million miles per hour (5,000 kilometers per second). Hubble's Advanced Camera for Surveys observed the supernova remnant on Oct. 28, 2006, with a filter that isolates light from glowing hydrogen seen in the expanding shell. These observations were then combined with visible-light images of the surrounding star field that were imaged with Hubble's Wide Field Camera 3 on Nov. 4, 2010. View the full article

Elliptical galaxies were once thought to be aging star cities whose star-making heyday was billions of years ago. But new observations with NASA's Hubble Space Telescope are helping to show that elliptical galaxies still have some youthful vigor left, thanks to encounters with smaller galaxies. Images of the core of NGC 4150, taken in near-ultraviolet light with the sharp-eyed Wide Field Camera 3 (WFC3), reveal streamers of dust and gas and clumps of young, blue stars that are significantly less than a billion years old. Evidence shows that the star birth was sparked by a merger with a dwarf galaxy. The new study helps bolster the emerging view that most elliptical galaxies have young stars, bringing new life to old galaxies. In the large-scale image, the dark strands of dust in the center provide tentative evidence of a recent galaxy merger. The inset image shows a magnified view of the chaotic activity inside the galaxy's core. The blue areas indicate a flurry of recent star birth. The stellar breeding ground is about 1,300 light-years across. The stars in this area are less than a billion years old. View the full article

Astronomers using NASA's Hubble Space Telescope received a boost from a cosmic magnifying glass to construct one of the sharpest maps of dark matter in the universe. They used Hubble's Advanced Camera for Surveys to chart the invisible matter in the massive galaxy cluster Abell 1689, located 2.2 billion light-years away. The cluster contains about 1,000 galaxies and trillions of stars. Dark matter is an invisible form of matter that accounts for most of the universe's mass. Hubble cannot see the dark matter directly. Astronomers inferred its location by analyzing the effect of gravitational lensing, where light from galaxies behind Abell 1689 is distorted by intervening matter within the cluster. Researchers used the observed positions of 135 lensed images of 42 background galaxies to calculate the location and amount of dark matter in the cluster. They superimposed a map of these inferred dark matter concentrations, tinted blue, on a Hubble image of the cluster. The new dark matter observations may yield new insights into the role of dark energy in the universe's early formative years. View the full article

The globular star cluster Omega Centauri has caught the attention of sky watchers ever since the ancient astronomer Ptolemy first catalogued it 2,000 years ago. Ptolemy, however, thought Omega Centauri was a single star. He didn't know that the "star" was actually a beehive swarm of nearly 10 million stars, all orbiting a common center of gravity. The stars are so tightly crammed together that astronomers had to wait for the powerful vision of NASA's Hubble Space Telescope to peer deep into the core of the "beehive" and resolve individual stars. Hubble's vision is so sharp it can even measure the motion of many of these stars, and over a relatively short span of time. Analyzing archived images taken over a four-year period by Hubble's Advanced Camera for Surveys, astronomers have made the most accurate measurements yet of the motions of more than 100,000 cluster inhabitants, the largest survey to date to study the movement of stars in any cluster. A precise measurement of star motions in giant clusters can yield insights into how stellar groupings formed in the early universe, and whether an "intermediate mass" black hole, one roughly 10,000 times as massive as our Sun, might be lurking among the stars. View the full article

This face-on spiral galaxy, called NGC 3982, is striking for its rich tapestry of star birth, along with its winding arms. The arms are lined with pink star-forming regions of glowing hydrogen, newborn blue star clusters, and obscuring dust lanes that provide the raw material for future generations of stars. The bright nucleus is home to an older population of stars, which grow ever more densely packed toward the center. NGC 3982 is located about 68 million light-years away in the constellation Ursa Major. The galaxy spans about 30,000 light-years, one-third of the size of our Milky Way galaxy. This color image is composed of exposures taken by the Hubble Space Telescope's Wide Field Camera 3 (WFC3), the Advanced Camera for Surveys (ACS), and the Wide Field Planetary Camera 2 (WFPC2). The observations were taken between March 2000 and August 2009. View the full article

Last January astronomers thought they had witnessed a fresh collision between two asteroids when images from NASA's Hubble Space Telescope revealed a bizarre X-shaped object. After using Hubble to track the oddball body for five months, astronomers were surprised to find that they had missed the suspected smashup by a year. The science results are reported in the October 14 issue of the science journal Nature. View the full article

NASA's Hubble Space Telescope has captured images of the large asteroid Vesta that will help scientists refine plans for the Dawn spacecraft's rendezvous with Vesta in July 2011. Scientists have constructed a video from the images that will help improve pointing instructions for Dawn as it is placed in a polar orbit around Vesta. Analyses of Hubble images revealed a pole orientation, or tilt, of approximately four degrees more to the asteroid's east than scientists previously thought. View the full article

If you think global warming is bad, 11 billion years ago the entire universe underwent, well, universal warming. The consequence was that fierce blasts of radiation from voracious black holes stunted the growth of some small galaxies for a stretch of 500 million years. Astronomers used the Hubble Space Telescope's Cosmic Origins Spectrograph (COS) to identify an era, from 11.7 to 11.3 billion years ago, when the universe burned off a fog of primeval helium. This heated intergalactic gas was inhibited from gravitationally collapsing to form new generations of stars in some small galaxies. The telltale helium spectral absorption lines were measured in the ultraviolet light from a quasar – the brilliant core of an active galaxy. The quasar beacon shines light through intervening clouds of invisible gas, like a headlight shining through a fog. The beam allows for a core-sample probe of the clouds of gas interspersed between galaxies in the early universe. The universe was a rambunctious place back then. Giant galaxies frequently collided. This engorged supermassive black holes in the cores of galaxies with infalling gas. The black holes furiously converted some of this mass to powerful far-ultraviolet radiation that would blaze out of galaxies. This heated intergalactic helium from 18,000 degrees Fahrenheit to nearly 40,000 degrees. Only after the helium cooled down could small galaxies resume normal assembly. View the full article

Hubble Space Telescope observations of comet 103P/Hartley 2, taken on September 25, are helping in the planning for a November 4 flyby of the comet by NASA's Deep Impact eXtended Investigation (DIXI) on NASA's Deep Impact Spacecraft performing the EPOXI mission. View the full article

Enjoying a frozen treat on a hot summer day can leave a sticky mess as it melts in the Sun and deforms. In the cold vacuum of space, there is no edible ice cream, but there is radiation from massive stars that is carving away at cold molecular clouds, creating bizarre, fantasy-like structures. These one-light-year-tall pillars of cold hydrogen and dust, imaged by the Hubble Space Telescope, are located in the Carina Nebula. This image is a composite of Hubble observations taken of the Carina Nebula region in 2005 in hydrogen light (light emitted by hydrogen atoms) along with observations taken in oxygen light (light emitted by oxygen atoms) in 2010, both times with Hubble's Advanced Camera for Surveys. The immense Carina Nebula is an estimated 7,500 light-years away in the southern constellation Carina. View the full article

This is an artist's concept of a craggy piece of solar system debris that belongs to a class of bodies called trans-Neptunian objects (TNOs). Most TNOs are small and faint, making them difficult to spot. Generally, they are more than 100 million times fainter than objects visible to the unaided eye. The newfound TNOs range from 25 to 60 miles (40-100 km) across. In this illustration, the distant Sun is reduced to a bright star at a distance of over 3 billion miles. Astronomers culling the data archives of NASA's Hubble Space Telescope have added 14 new TNOs to the catalog. Their search method promises to turn up hundreds more. View the full article

An international team of astronomers using the Hubble Space Telescope reports a significant brightening of the emissions from Supernova 1987A. The results, which appear in this week's Science magazine, are consistent with theoretical predictions about how supernovae interact with their immediate galactic environment. View the full article

An international team of astronomers using NASA's Hubble Space Telescope has devised a new method for measuring perhaps the greatest puzzle of our universe – dark energy. This mysterious phenomenon, discovered in 1998, is pushing our universe apart at ever-increasing speeds. The team's results appear in the August 20, 2010 issue of the journal Science. View the full article

A long-exposure Hubble Space Telescope image shows a majestic face-on spiral galaxy located deep within the Coma Cluster of galaxies, which lies 320 million light-years away in the northern constellation Coma Berenices. The galaxy, known as NGC 4911, contains rich lanes of dust and gas near its center. These are silhouetted against glowing newborn star clusters and iridescent pink clouds of hydrogen, the existence of which indicates ongoing star formation. Hubble has also captured the outer spiral arms of NGC 4911, along with thousands of other galaxies of varying sizes. The high resolution of Hubble's cameras, paired with considerably long exposures, made it possible to observe these faint details. This natural-color Hubble image, which combines data obtained in 2006, 2007, and 2009 from the Wide Field Planetary Camera 2 and the Advanced Camera for Surveys, required 28 hours of exposure time. View the full article

A beautiful new image of two colliding galaxies has been released by NASA's Great Observatories. The Antennae galaxies, located about 62 million light-years from Earth, are shown in this composite image from the Chandra X-ray Observatory (blue), the Hubble Space Telescope (gold and brown), and the Spitzer Space Telescope (red). The imaging data were taken in 1999, 2003, 2004, and 2005. The Antennae galaxies take their name from the long antenna-like "arms," seen in wide-angle views of the system. These features were produced by tidal forces generated in the collision. View the full article

A hundred million years ago, a triple-star system was traveling through the bustling center of our Milky Way galaxy when it made a life-changing misstep. The trio wandered too close to the galaxy's giant black hole, which captured one of the stars and hurled the other two out of the Milky Way. Adding to the stellar game of musical chairs, the two outbound stars merged to form a super-hot, blue star. This story may seem like science fiction, but astronomers using NASA's Hubble Space Telescope say it is the most likely scenario for a so-called hypervelocity star, known as HE 0437-5439, one of the fastest ever detected. It is blazing across space at a speed of 1.6 million miles (2.5 million kilometers) an hour, three times faster than our Sun's orbital velocity in the Milky Way. Hubble observations confirm that the stellar speedster hails from our galaxy's core. View the full article

As if the debate over what is and what is not a planet hasn't gotten confusing enough, Hubble Space Telescope astronomers have now confirmed the existence of a tortured, baked object that could be called a "cometary planet." The gas giant planet, dubbed HD 209458b, is orbiting so close to its star that its heated atmosphere is escaping away into space. Now, observations by the new Cosmic Origins Spectrograph (COS) aboard NASA's Hubble suggest that powerful stellar winds are sweeping the castoff material behind the scorched planet and shaping it into a comet-like tail. This artist's illustration shows a view of HD 209458b, as seen from the surface of a hypothetical nearby companion object. View the full article