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Our solar system contains two major classes of planets. Earth is a rocky terrestrial planet, as are Mercury, Venus, and Mars. At about the distance of the asteroid belt, there is a "frost line" where space is so cold more volatile material, like water, can remain frozen. Out here live the gas giants–Jupiter, Saturn, Uranus, and Neptune–which have bulked up on hydrogen and helium and other volatiles. Astronomers are curious about a new class of planet not found in the Solar System. Weighing in at 12.6 Earth masses the planet is more massive than Earth, but less massive than Neptune (hence, intermediate between the rocky and gaseous planets in the Solar System). What's more, the planet, GJ 3470 b, is so close to its red dwarf star that it completes one orbit in just three days! As odd as it seems, planets in this mass range are likely the most abundant throughout the galaxy, based on surveys by NASA's Kepler space telescope. But they are not found in our own solar system. Astronomers enlisted the combined multi-wavelength capabilities of NASA's Hubble and Spitzer space telescopes to assemble for the first time a "fingerprint" of the chemical composition of GJ 3470 b's atmosphere, which turns out to be mostly hydrogen and helium, and surprisingly, largely lacking heavier elements. One possible explanation is that the planet formed as a 10-Earth-mass rocky core that then accumulated hydrogen very close to its star, rather than migrated in which is the conventional wisdom for star-hugging planets. View the full article

In the mid-1800s, mariners sailing the southern seas navigated at night by a brilliant star in the constellation Carina. The star, named Eta Carinae, was the second brightest star in the sky for more than a decade. Those mariners could hardly have imagined that by the mid-1860s the brilliant orb would no longer be visible. Eta Carinae was enveloped by a cloud of dust ejected during a violent outburst. Stars don't normally play vanishing acts unless they are undergoing rapid and violent activity. Observations by the Hubble Space Telescope and other observatories have helped astronomers piece together the story of this unique star's petulant behavior. During part of its adult life, Eta Carinae has undergone a series of eruptions, becoming extremely bright during each episode, before fading away. One explanation for the monster star's antics is that the convulsions were caused by a complex interplay of as many as three stars, all gravitationally bound in one system. The most massive member – weighing in at 150 times our Sun's mass – swallowed one of the stars. This violent event ignited the massive outburst of the mid-1800s. Evidence for that event, dubbed the Great Eruption, lies in the huge, expanding bipolar lobes of hot gas surrounding the system. Because of Eta Carinae's violent history, astronomers have kept watch over its activities. Although Hubble has monitored the volatile superstar for 25 years, it still is uncovering new revelations. Using Hubble to map the ultraviolet-light glow of magnesium embedded in warm gas, astronomers were surprised to discover the gas in places they had not seen it before. The newly revealed gas is important for understanding how the eruption began, because it represents the fast and energetic ejection of material that may have been expelled by the star shortly before the expulsion of the bipolar bubbles. One of the most massive known stars in the Milky Way galaxy, Eta Carinae is destined to finally meet its end by exploding as a supernova. View the full article

Finding common table salt — sodium chloride — on the surface of a moon is more than just a scientific curiosity when that moon is Europa, a potential abode of life. If the salt came from the briny subsurface ocean of Europa, a satellite of Jupiter, that ocean may chemically resemble Earth's oceans more than previously thought. Because Europa's solid, icy crust is geologically young it has been suspected that whatever salts exist on the surface may come from the ocean below, which might host microorganisms. Using visible-light spectral analysis, planetary scientists at Caltech and NASA's Jet Propulsion Laboratory discovered that the yellow color visible on portions of the surface of Europa is sodium chloride. They reached this conclusion with spectroscopic data from NASA's Hubble Space Telescope. Researchers were able to identify a distinct absorption in the visible spectrum which matches how salt would look when irradiated by the Sun. Tara Regio is the yellowish area to left of center, in this NASA Galileo image of Europa’s surface. This region of geologic chaos is the area researchers identified an abundance of sodium chloride. The finding was published in Science Advances on June 12. View the full article

In order to grow to Jupiter size or larger, a gas giant planet must slurp large quantities of hydrogen and other gases from the disk in which it forms. Astronomers have looked for evidence of this process, but direct observations are challenging because planets become lost in the glare of their star. A team has succeeded in making ground-based observations of two planets accreting matter from a disk. It represents only the second multi-planet system to be directly imaged. View the full article

One doesn't need a Ph.D. in astrophysics to recognize there is something odd-looking about this otherwise beautiful galaxy, NCG 4485. Like the Batman character Two-Face, one side looks normal, but the other side looks contorted with a firestorm of star formation going on. Why the colorful asymmetry in an island star city many thousands of light-years across? The clue is off the edge of the photo. It's another galaxy, NGC 4490, that swept by NGC 4485 millions of years ago. The gravitational taffy pull between the two galaxies compressed interstellar gas to trigger a flurry of new star birth as seen in the abundance of young blue stars and pinkish nebulas. So, out of a near-collision between two galaxies comes stellar renewal and birth. It's a trademark of our compulsive universe where even things as big as galaxies can go bump in the night. View the full article

How far is far? And, how do you know when you get there? In 1995, astronomers decided to use the Hubble Space Telescope to conduct a bold and daring experiment to address this puzzle. For 10 consecutive days, Hubble stared at one tiny, seemingly empty patch of sky for 1 million seconds. The gamble of precious telescope time paid off. Hubble captured the feeble glow of myriad never-before-seen galaxies. Many of the galaxies are so far away it has taken billions of years for their light to reach us. Therefore, the view is like looking down a "time corridor," where galaxies can be seen as they looked billions of years ago. Hubble became astronomy's ultimate time machine. The resulting landmark image is called the Hubble Deep Field. At the time, the image won the gold medal for being the farthest peek into the universe ever made. Its stunning success encouraged astronomers to pursue a series of Hubble deep-field surveys. The succeeding surveys uncovered more galaxies at greater distance from Earth, thanks to new cameras installed on Hubble during astronaut servicing missions. The cameras increased the telescope's power to look even deeper into the universe. These surveys provided astronomers with a huge scrapbook of images, showing how, following the big bang, galaxies built themselves up over time to become the large, majestic assemblages seen today in the nearby universe. Among the most notable deep-field surveys are the Great Observatories Origins Deep Survey (GOODS), in 2003; the Hubble Ultra Deep Field (HUDF), in 2004; and the eXtreme Deep Field (XDF), in 2012. Now, astronomers are releasing a new deep-field image by weaving together exposures from several of these previous galaxy "fishing expeditions." Their efforts have produced the largest, most comprehensive “history book” of galaxies in the universe. The snapshot, a combination of nearly 7,500 separate Hubble exposures, represents 16 years' worth of observations. The ambitious endeavor is called the Hubble Legacy Field. The new view contains about 30 times as many galaxies as in the HUDF. The wavelength range stretches from ultraviolet to near-infrared light, capturing all the features of galaxy assembly over time. The image mosaic presents a wide portrait of the distant universe and contains roughly 265,000 galaxies. They stretch back through 13.3 billion years of time to just 500 million years after the universe's birth in the big bang. View the full article

There is something wrong with our universe. Or, more specifically, it is outpacing all expectations for its present rate of expansion. Something is amiss in astronomers' efforts to measure the past and predict the present, according to a discrepancy between the two main techniques for measuring the universe's expansion rate – a key to understanding its history and physical parameters. The inconsistency is between the Hubble Space Telescope measurements of today's expansion rate of the universe (by looking at stellar milepost markers) and the expansion rate as measured by the European Space Agency's Planck satellite. Planck observes the conditions of the early universe just 380,000 years after the big bang. For years, astronomers have been assuming this discrepancy would go away due to some instrumental or observational fluke. Instead, as Hubble astronomers continue to "tighten the bolts" on the accuracy of their measurements, the discordant values remain stubbornly at odds. The chances of the disagreement being just a fluke have skyrocketed from 1 in 3,000 to 1 in 100,000. Theorists must find an explanation for the disparity that could rattle ideas about the very underpinnings of the universe. View the full article

This Hubble image shows the results of two stellar companions in a gravitational waltz, several thousand light-years from Earth in the southern constellation Centaurus. The stellar duo, consisting of a red giant and white dwarf, are too close together to see individually in this view. But the consequences of their whirling about each other are two vast shells of gas expanding into space like a runaway hot air balloon. Both stars are embedded in a flat disk of hot material that constricts the outflowing gas so that it only escapes away above and below the stars. This apparently happens in episodes because the nebula has two distinct nested hourglass-shaped structures. The bubbles of gas and dust appear brightest at the edges, giving the illusion of crab legs. The rich colors correspond to glowing hydrogen, sulfur, nitrogen, and oxygen. This image was taken to celebrate Hubble's 29th anniversary since its launch on April 24, 1990. View the full article

NASA has selected 24 new Fellows for its prestigious NASA Hubble Fellowship Program (NHFP). The program enables outstanding postdoctoral scientists to pursue independent research in any area of NASA Astrophysics, using theory, observation, experimentation, or instrument development. Each fellowship provides the awardee up to three years of support. View the full article

Astronomers once thought asteroids were boring, wayward space rocks that simply orbit around the Sun. These objects were dramatically presented only in science fiction movies. But recent observations show that asteroids are anything but dull. In reality they are dynamic, active worlds that can ultimately disintegrate due to the long-term subtle effects of sunlight, which can slowly spin them up until they begin to shed material. Several telescopes, including NASA's Hubble Space Telescope, have caught the gradual self-destruction of the asteroid (6478) Gault. Images from Hubble show two narrow, comet-like tails of dusty debris streaming from the diminutive asteroid. For Gault, a mass of rubble a few miles across, mere sunlight set the stage for its gradual demise. The force of sunlight, in concert with Gault's own asymmetrical shape, speeded up the asteroid's rotation over a period of more than 100 million years. The estimated spin-up rate is 1 second every 10,000 years. Today, the asteroid is rotating once every two hours, a speed so fast that it can no longer hold its surface material. The slightest disturbance — perhaps the impact of a pebble, or just a failure of the stressed material — may have set off a collapse. The dust left the asteroid's surface in gentle, short bursts, perhaps due to landslides lasting anywhere from a few hours to a few days. The particles are drifting away from Gault's surface at the speed of a strolling human. The gentle process is like scattering flour into the air, where wind — or sunlight, in the case of Gault — stretches the debris into a long streamer. Astronomers will monitor the asteroid for future events. About 800,000 known asteroids reside between Mars and Jupiter, and they may fly apart at the rate of roughly one per year. View the full article

We live in a gigantic star city. Our Milky Way galaxy contains an estimated 200 billion stars. But that's just the bare tip of the iceberg. The Milky Way is surrounded by vast amounts of an unknown material called dark matter that is invisible because it doesn't release any radiation. Astronomers know it exists because, dynamically, the galaxy would fly apart if dark matter didn't keep a gravitational lid on things. Still, astronomers would like to have a precise measure of the galaxy's mass to better understand how the myriad galaxies throughout the universe form and evolve. Other galaxies can range in mass from around a billion solar masses to 30 trillion solar masses. How does our Milky Way compare? Curious astronomers teamed up the Hubble Space Telescope and European Space Agency's Gaia satellite to precisely study the motions of globular star clusters that orbit our galaxy like bees around a hive. The faster the clusters move under the entire galaxy's gravitational pull, the more massive it is. The researchers concluded the galaxy weighs 1.5 trillion solar masses, most of it locked up in dark matter. Therefore, the Milky Way is a "Goldilocks" galaxy, not too big and not too small. Just right! View the full article

NASA has recovered the Hubble Space Telescope's Advanced Camera for Surveys instrument, which suspended operations on Thursday, Feb. 28, 2019. The final tests were conducted and the instrument was brought back to its operational mode on March 6. View the full article

At 8:31 p.m. EST on February 28, 2019, the Advanced Camera for Surveys (ACS) aboard NASA's Hubble Space Telescope suspended operations after an error was detected as the instrument was performing a routine boot procedure. The error indicated that software inside the camera had not loaded correctly. A team of instrument system engineers, flight software experts, and flight operations personnel quickly organized to download and analyze instrument diagnostic information. This team is currently working to identify the root cause and then to construct a recovery plan. View the full article

The phrase "a chip off the old block" apparently also applies to the outer moons of our solar system. A tiny moon whirling around Neptune that was uncovered in Hubble Space Telescope photographs taken in 2013 has puzzled astronomers ever since then because it is very close to a much larger moon named Proteus. The orbits of the two moons are presently 7,500 miles apart. Proteus, at 260 miles in diameter, is roughly the size of the state of Ohio. By contrast, Hippocamp is just 20 miles across, or the size of metropolitan Columbus, Ohio. Proteus should have gravitationally swept aside or swallowed the moon while clearing out its orbital path. Smoking-gun evidence for Hippocamp's origin comes from NASA Voyager 2 images from 1989 that show a large impact crater on Proteus, almost large enough to have shattered the moon. Apparently, a little piece of Proteus got kicked off and has slowly migrated away from the parent body. Neptune's satellite system has a violent and tortured history. Many billions of years ago, Neptune captured the large moon Triton from the Kuiper Belt. Triton's gravity would have torn up Neptune's original satellite system. Triton settled into a circular orbit and the debris from shattered Neptunian moons re-coalesced into a second generation of natural satellites. However, comet bombardment continued to tear things up, leading to the birth of Hippocamp, which might be considered a third-generation satellite. View the full article

The two major planets beyond Saturn have only been visited once by a spacecraft, albeit briefly. NASA's Voyager 2 spacecraft swung by Uranus in 1986, and Neptune in 1989. Our robotic deep-space tourist snapped the only close-up, detailed images of these monstrous worlds. For Neptune, the images revealed a planet with a dynamic atmosphere with two mysterious dark vortices. Uranus, however, appeared featureless. But these views were only brief snapshots. They couldn't capture how the planets' atmospheres change over time, any more than a single snapshot of Earth could tell meteorologists about weather behavior. And, they go through protracted seasonal changes in their multi-decades-long orbits. Ever since the Voyager encounter, the Hubble Space Telescope has provided an opportunity to monitor these worlds like a diligent weatherman. Since Hubble's launch in 1990, astronomers have used it to amass an album of outer planet images. Yearly monitoring of these giant worlds is now allowing astronomers to study long-term seasonal changes, as well as capture transitory weather patterns. One such elusive event is yet another dark storm on Neptune, shown in the latest Hubble image of the planet (right). The telescope's new snapshot of Uranus (left) shows that the ice giant is not a planetary wallflower. A vast bright polar cap across the north pole dominates the image. The cap, which may form due to seasonal changes in atmospheric flow, has become much more prominent than in previous observations dating back to the Voyager 2 flyby, when the planet, in the throes of winter, looked bland. View the full article

The universe is very cluttered. Myriad island cities of stars, the galaxies, form a backdrop tapestry. Much closer to home are nebulae, star clusters, and assorted other foreground celestial objects that are mostly within our Milky Way galaxy. Despite the vastness of space, objects tend to get in front of each other. This happened when astronomers used the Hubble Space Telescope to photograph the globular star cluster NGC 6752 (located 13,000 light-years away in our Milky Way's halo). In a celestial game of "Where's Waldo?," Hubble's sharp vision uncovered a never-before-seen dwarf galaxy located far behind the cluster's crowded stellar population. The loner galaxy is in our own cosmic backyard, only 30 million light-years away (approximately 2,300 times farther than the foreground cluster). The object is classified as a dwarf spheroidal galaxy because it measures only around 3,000 light-years at its greatest extent (barely 1/30th the diameter of the Milky Way), and it is roughly a thousand times dimmer than the Milky Way. Because of its 13-billion-year-old age, and its isolation — which resulted in hardly any interaction with other galaxies — the dwarf is the astronomical equivalent of a living fossil from the early universe. The international team of astronomers that carried out this study consists of L. Bedin (INAF-Astronomical Observatory of Padua, Italy), M. Salaris (Liverpool John Moores University, Liverpool, England, UK), R. Rich (University of California, Los Angeles, California, USA), H. Richer (University of British Columbia, Vancouver, British Columbia, Canada), J. Anderson (Space Telescope Science Institute, Baltimore, Maryland, USA), B. Bettoni (INAF-Astronomical Observatory of Padua, Italy), D. Nardiello, A. Milone, and A. Marino (University of Padua, Italy), M. Libralato and A. Bellini (Space Telescope Science Institute, Baltimore, Maryland, USA), A. Dieball (University of Bonn, Bonn, Germany), P. Bergeron (University of Montreal, Quebec, Canada), A. Burgasser (University of California, San Diego, California, USA), and D. Apai (University of Arizona, Tucson, Arizona, USA). View the full article

Data from the world's largest digital sky survey is being publicly released today by the Space Telescope Science Institute (STScI) in Baltimore, Maryland, in conjunction with the University of Hawai’i Institute for Astronomy in Honolulu, Hawaii. Data from the Pan-STARRS1 Surveys will allow anyone to access millions of images and use the database and catalogs containing precision measurements of billions of stars and galaxies. This data release contains over 1.6 petabytes of data (a petabyte is one million gigabytes), making it the largest volume of astronomical information ever released. The survey data resides in the Mikulski Archive for Space Telescopes (MAST), which serves as NASA's repository for all of its optical and ultraviolet-light observations. View the full article

Two's company and three's a crowd. But thousands are a mosh pit. That's the case in the giant Coma cluster of more than 1,000 galaxies. Hubble spotted a wayward spiral galaxy losing its gas as it plunges toward the center of the massive cluster and is roughed up as it plows through the intergalactic medium. Telltale evidence lies in a long, thin streamer of material that is stretching like taffy from the galaxy's core and on into intergalactic space. Gas is the lifeblood of a galaxy, fueling the birth of new stars. Once it is stripped of all of its gas, the galaxy, named D100, will enter retirement and shine only by the feeble glow of its aging, red stars. D100 is being stripped of its gas because of the gravitational tug of a grouping of giant "bully" galaxies in the crowded cluster. Their combined gravity is pulling the beleaguered galaxy toward the cluster's center. As D100 falls toward the core, the galaxy barrels through material. This action forces gas from the galaxy. The gas-stripping process in D100 began roughly 300 million years ago. In the massive Coma cluster this violent gas-loss process occurs in many galaxies. But D100 is unique in several ways. Its long, thin tail is its most unusual feature extending nearly 200,000 light-years. But the pencil-like structure is comparatively narrow, only 7,000 light-years wide. Thankfully, our Milky Way galaxy lives in a sparsely populated small corner of the universe, with only one other big galaxy as a companion. View the full article

The Hubble Space Telescope's Wide Field Camera 3 was brought back to full operational status and completed its first science observations just after noon EST today, Jan. 17, 2019. View the full article

NASA has moved closer to conducting science operations again with the Hubble Space Telescope's Wide Field Camera 3 instrument, which suspended operations on Tuesday, Jan. 8, 2019. Today, Jan. 15, the instrument was brought back to its operations mode. After resetting the telemetry circuits and associated boards, additional engineering data were collected and the instrument was brought back to operations. All values were normal. Additional calibration and tests will be run over the next 48 to 72 hours to ensure that the instrument is operating properly. Assuming that all tests work as planned, it is expected that the Wide Field Camera 3 will start to collect science images again by the end of the week. View the full article

NASA continues to work toward recovering the Hubble Space Telescope’s Wide Field Camera 3 instrument, which suspended operations on Tuesday, January 8. A team of instrument system engineers, Wide Field Camera 3 instrument developers, and other experts formed and quickly began collecting all available telemetry and onboard memory information to determine the sequence of events that caused the values to go out of limits. This team is currently working to identify the root cause and then to construct a recovery plan. If a significant hardware failure is identified, redundant electronics built into the instrument will be used to recover and return it to operations. View the full article

Less than a billion years after the big bang, a monster black hole began devouring anything within its gravitational grasp. This triggered a firestorm of star formation around the black hole. A galaxy was being born. A blowtorch of energy, equivalent to the light from 600 trillion Suns, blazed across the universe. Now, 12.8 billion years later, the Hubble Space Telescope captured the beacon from this event. But Hubble astronomers needed help to spot it. The gravitational warping of space by a comparatively nearby intervening galaxy greatly amplified and distorted the quasar's light, making it the brightest such object seen in the early universe. It offers a rare opportunity to study a zoomed-in image of how supermassive black holes accompanied star formation in the very early universe and influenced the assembly of galaxies. View the full article

The Wide Field Camera 3 on the Hubble Space Telescope suspended operations on January 8 due to a hardware problem. Hubble will continue to perform science observations with its other three active instruments, while the Wide Field Camera 3 anomaly is investigated. Wide Field Camera 3, installed during Servicing Mission 4 in 2009, is equipped with redundant electronics should they be needed to recover the instrument. View the full article

Our Sun is not one of the most abundant types of star in our Milky Way galaxy. That award goes to red dwarfs, stars that are smaller and cooler than our Sun. In fact, red dwarfs presumably contain the bulk of our galaxy's planet population, which could number tens of billions of worlds. Surveys by NASA's Kepler Space Telescope and other observatories have shown that rocky planets are common around these diminutive stars. Some of these rocky worlds are orbiting within the habitable zones of several nearby red dwarfs. The temperate climates on such worlds could allow for oceans to exist on their surface, possibly nurturing life. That's the good news. The bad news is that many of these rocky planets may not harbor water and organic material, the necessary ingredients for life as we know it. Earth, which formed as a "dry" planet, was seeded over hundreds of millions of years with icy material from comets and asteroids arriving from the outer solar system. If the same life-nurturing process is needed for planets around red dwarfs, then they may be in trouble. Researchers using the Hubble Space Telescope and the European Southern Observatory’s Very Large Telescope (VLT) in Chile have discovered a rapidly eroding dust-and-gas disk encircling the young, nearby red dwarf star AU Microscopii (AU Mic). The disk is being excavated by fast-moving blobs of material, which are acting like a snowplow by pushing small particles — possibly containing water and other volatiles — out of the system. Astronomers don’t yet know how the blobs were launched. One theory is that powerful mass ejections from the turbulent star expelled them. Such energetic activity is common among young red dwarfs. If the disk around AU Mic continues to dissipate at the current pace, it will be gone in about 1.5 million years, which is the blink of an eye in cosmic time. Smaller bodies, such as comets and asteroids, could be cleared out of the disk within that short time span. Planets, however, would be too massive to be displaced. Without enrichment from comet and asteroid material, the planets may end up dry, dusty, and lifeless. View the full article

NASA's Hubble Space Telescope has produced this stunningly detailed portrait of the Triangulum galaxy (M33), displaying a full spiral face aglow with the light of nearly 25 million individually resolved stars. It is the largest high-resolution mosaic image of Triangulum ever assembled, composed of 54 Hubble fields of view spanning an area more than 19,000 light-years across. The Local Group of galaxies is dominated by the Milky Way, Andromeda, and Triangulum. As the junior member of this trio of spiral galaxies, Triangulum provides the valuable comparisons and contrasts that only a close companion can. Most notably, Triangulum's star formation is 10 times more intense than in the comparable Hubble panorama of the neighboring Andromeda galaxy. Astronomers have only begun to mine the enormous amount of data generated by these new Hubble observations, and expect they will yield important insights into the effects of such vigorous star formation. The orderly nature of Triangulum's spiral, with dust distributed throughout, is another distinctive feature. Astronomers think that in the Local Group, Triangulum has been something of an introvert, isolated from frequent interactions with other galaxies while keeping busy producing stars along organized spiral arms. Uncovering the Triangulum galaxy’s story will provide an important point of reference in understanding how galaxies develop over time, and the diverse paths that shape what we see today. View the full article