Hubble Sees Evaporating Planet Getting the Hiccups

Life around an ill-tempered red dwarf star is no fun for accompanying newborn planets. Call it a baptism of fire. Entangled magnetic fields cause a red dwarf to spit out "super-flares" that are 100 to 1,000 times more powerful than similar flares seen on our Sun. That is coupled with blistering ultraviolet radiation requiring any of the star system's inhabitants to use "Sunscreen 5,000." One of the nearest and most violent examples is AU Microscopii. The petulant star is only 1% the age of our Sun. At a distance of 32 light-years, it is only eight times farther away than the nearest star to our Sun, Proxima Centauri (which is another red dwarf). The star beats-up the system's innermost planet, AU Microscopii b, which is about four times Earth's diameter. Orbiting just 6 million miles from the evil star's "dragon’s breath," the planet's largely hydrogen atmosphere is being stripped off, as viewed by the Hubble Space Telescope. But this happens in fits and starts. During one passage of the planet across the face if its star, Hubble detected hydrogen boiling off to create a large cloud ahead of the planet. This unexpected variability is evidence that the interaction between the planet and the red dwarf's feisty fireworks is probably more complex and unpredictable than imagined. A young planet whirling around a petulant red dwarf star is changing in unpredictable ways orbit-by-orbit. It is so close to its parent star that it experiences a consistent, torrential blast of energy, which evaporates its hydrogen atmosphere — causing it to puff off the planet. But during one orbit observed with the Hubble Space Telescope, the planet looked like it wasn't losing any material at all, while an orbit observed with Hubble a year and a half later showed clear signs of atmospheric loss.

This extreme variability between orbits shocked astronomers. "We've never seen atmospheric escape go from completely not detectable to very detectable over such a short period when a planet passes in front of its star," said Keighley Rockcliffe of Dartmouth College in Hanover, New Hampshire. "We were really expecting something very predictable, repeatable. But it turned out to be weird. When I first saw this, I thought 'That can't be right.'"

Rockcliffe was equally puzzled to see, when it was detectable, the planet's atmosphere puffing out in front of the planet, like a headlight on a fast-bound train. "This frankly strange observation is kind of a stress-test case for the modeling and the physics about planetary evolution. This observation is so cool because we're getting to probe this interplay between the star and the planet that is really at the most extreme," she said.

Located 32 light-years from Earth, the parent star AU Microscopii (AU Mic) hosts one of the youngest planetary systems ever observed. The star is less than 100 million years old (a tiny fraction of the age of our Sun, which is 4.6 billion years old). The innermost planet, AU Mic b, has an orbital period of 8.46 days and is just 6 million miles from the star (about 1/10th the planet Mercury's distance from our Sun). The bloated, gaseous world is about four times Earth's diameter.

AU Mic b was discovered by NASA’s Spitzer and TESS (Transiting Exoplanet Survey Satellite) space telescopes in 2020. It was spotted with the transit method, meaning telescopes can observe a slight dip in the star's brightness when the planet crosses in front of it.

Red dwarfs like AU Microscopii are the most abundant stars in our Milky Way galaxy. They therefore should host the majority of planets in our galaxy. But can planets orbiting red dwarf stars like AU Mic b be hospitable to life? A key challenge is that young red dwarfs have ferocious stellar flares blasting out withering radiation. This period of high activity lasts a lot longer than that of stars like our Sun.

The flares are powered by intense magnetic fields that get tangled by the roiling motions of the stellar atmosphere. When the tangling gets too intense, the fields break and reconnect, unleashing tremendous amounts of energy that are 100 to 1,000 times more energetic than our Sun unleashes in its outbursts. It's a blistering fireworks show of torrential winds, flares, and X-rays blasting any planets orbiting close to the star. "This creates a really unconstrained and frankly, scary, stellar wind environment that's impacting the planet's atmosphere," said Rockcliffe.

Under these torrid conditions, planets forming within the first 100 million years of the star's birth should experience the most amount of atmospheric escape. This might end up completely stripping a planet of its atmosphere.

"We want to find out what kinds of planets can survive these environments. What will they finally look like when the star settles down? And would there be any chance of habitability eventually, or will they wind up just being scorched planets?" said Rockcliffe. "Do they eventually lose most of their atmospheres and their surviving cores become super-Earths? We don't really know what those final compositions look like because we don't have anything like that in our solar system."

While the star's glare prevents Hubble from directly seeing the planet, the telescope can measure changes in the star's apparent brightness caused by hydrogen bleeding off the planet and dimming the starlight when the planet transits the star. That atmospheric hydrogen has been heated to the point where it escapes the planet's gravity.

The never-before-seen changes in atmospheric outflow from AU Mic b may indicate swift and extreme variability in the host red dwarf's outbursts. There is so much variability because the star has a lot of roiling magnetic field lines. One possible explanation for the missing hydrogen during one of the planet's transits is that a powerful stellar flare, seen seven hours prior, may have photoionized the escaping hydrogen to the point where it became transparent to light, and so was not detectable.

Another explanation is that the stellar wind itself is shaping the planetary outflow, making it observable at some times and not observable at other times, even causing some of the outflow to "hiccup" ahead of the planet itself. This is predicted in some models, like those of John McCann and Ruth Murray-Clay from the University of California at Santa Cruz, but this is the first kind of observational evidence of it happening and to such an extreme degree, say researchers.

Hubble follow-up observations of more AU Mic b transits should offer additional clues to the star and planet's odd variability, further testing scientific models of exoplanetary atmospheric escape and evolution.

Rockcliffe is lead author on the science paper published in The Astronomical Journal.

The Hubble Space Telescope is a project of international cooperation between NASA and ESA. NASA's Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy, in Washington, D.C.

Scientists find chunk of blown-apart star hurtling through Milky Way at breakneck speed

A chunk of stellar shrapnel is careering toward the edge of our Milky Way galaxy at almost 2 million mph (3.2 million kph), a new study reports. "The star is moving so fast that it's almost certainly leaving the galaxy," study co-lead author J.J. Hermes, an associate professor of astronomy at Boston University, said in a statement. The star, known as LP 40-365, currently lies about 2,000 light-years from Earth. And calling it a star may be a bit generous, actually; Hermes and his colleagues think it's a hunk of a superdense stellar corpse called a white dwarf that was blown apart in a violent supernova explosion after gobbling up too much mass from a companion. "To have gone through partial detonation and still survive is very cool and unique, and it's only in the last few years that we've started to think this kind of star could exist," study co-author Odelia Putterman, a former Boston University student who has worked in Hermes' lab, said in the same statement. The speedy star was spotted during an analysis of survey data gathered by NASA's Hubble Space Telescope and Transiting Exoplanet Survey Satellite (TESS). The researchers noticed that LP 40-365 is not only racing along but is also rotating once every nine hours as it goes.The rotation in itself is nothing unusual, for all stars rotate; our own sun spins on its axis every 27 Earth days. However, according to researchers, a nine-hour rotational period is considered to be relatively slow for an object that went through something as catastrophic as a supernova. 

It's this sluggish rotation that implies LP 40-365 was once part of a two-star system with an unhealthy feeding habit.

According to the researchers, stars commonly orbit each other in close pairs, including highly dense white dwarfs. In such binary systems, if one white dwarf transfers too much mass to the other, the result can be a supernova — the largest explosion that takes place in space, according to NASA.

It's usually hard to determine which star was the "donor" and which was the "eater." But because LP 40-365's rotation is relatively slow, the research team feels confident that the object is cosmic shrapnel from the exploded star. As the two stars orbited each other at high speeds and in close proximity, the resulting supernova likely catapulted both stars out at breakneck speed, but we've only been able to spot LP 40-365, according to the statement.

"This [paper] adds one more layer of knowledge into what role these stars played when the supernova occurred," and what can happen after the explosion, Putterman said. "By understanding what's happening with this particular star, we can start to understand what's happening with many other similar stars that came from a similar situation."

These supernova survivors are even more intriguing as they are metal-rich, unlike our sun, which is primarily composed of hydrogen and helium. (Astronomers consider any element heavier than hydrogen and helium a metal.)

"These are very weird stars," Hermes said. "What we're seeing are the byproducts of violent nuclear reactions that happen when a star blows itself up." Strange stars like LP 40-365 are therefore fascinating targets to study, the researchers said.

The research is described in a study published June 10 in The Astrophysical Journal Letters.

NASA will attempt a 'risky' maneuver to fix its broken Hubble Space Telescope as early as next week

NASA's Hubble Space Telescope has been offline for nearly a month.The telescope's payload computer - a 1980s machine that controls and monitors all of the spacecraft's science instruments - suddenly stopped working on June 13. Engineers have been troubleshooting the problem since then, but with little success. However, a recent NASA announcement suggests a glimmer of hope: The agency tweeted on Thursday that it had successfully tested a procedure that would switch parts of the telescope's hardware to their back-up components.This could pave the way for the payload computer to come back online, leading to the restart of Hubble's scientific observations. NASA reported the procedure could happen as early as next week, following additional preparations and reviews. The telescope and the scientific instruments on board remain in working condition. But the switch will be "risky," according to NASA astrophysics division director Paul Hertz. "You can't actually put your hands on and change hardware or take a voltage, so that does make it very challenging," he told New Scientist.

Hubble is the world's most powerful space telescope; it orbits 353 miles above the Earth.

On June 30, NASA announced it had figured out that the source of the payload computer problem was in Hubble's Science Instrument Command and Data Handling unit (SI C&DH for short), where the computer resides.

"A few hardware pieces on the SI C&DH could be the culprit(s)," NASA said.

Backup pieces of hardware are pre-installed on the telescope. So it's just a matter of switching over to that redundant hardware. But before attempting the tricky switch from Earth, engineers have to practice in a simulator, the agency added.

NASA has rebooted Hubble using this type of operation in the past. In 2008, after a computer crash took the telescope offline for two weeks, engineers successfully switched over to redundant hardware. A year later, astronauts repaired two broken instruments while in-orbit - Hubble's fifth and final reservicing operation. (NASA does not currently have a way to launch astronauts to the space telescope)

Getting the observatory back online is critical to NASA.

"Hubble is one of NASA's most important astrophysics missions. It's been operating for over 31 years, and NASA is hopeful it will last for many more years," an agency spokesperson told Insider in June.

Hubble, which launched into orbit in 1990, has captured images of the births and deaths of stars, discovered new moons around Pluto, and tracked two interstellar objects as they zipped through our solar system. Hubble's observations have also allowed astronomers to calculate the age and expansion of the universe and to peer at galaxies formed shortly after the Big Bang.

Hubble telescope finds rare double quasars in ancient galactic collisions

NASA's Hubble Space Telescope has captured not one but two pairs of distant quasars that existed some 10 billion years ago, a new study reports. According to the team leading the research, the discovery was like finding a needle in a haystack, as the chance of locating a double quasar compared to a single quasar is just one in 1,000. Imagery captured by the long-serving space telescope shows that the quasars within each pair are only about 10,000 light-years apart. For comparison, our sun is 26,000 light-years away from the supermassive black hole at the heart of the Milky Way. The researchers, led by Nadia Zakamska of Johns Hopkins University in Baltimore, Maryland, believe that the quasars are knitted so closely to each other because each pair lies at the center of two galaxies in the midst of a smashup. A quasar is an intense emission of light from the center of a galaxy that's fuelled by the gluttonous supermassive black hole at its core. "Quasars make a profound impact on galaxy formation in the universe," Zakamska said in a statement released on April 6. When two galaxies collide, their intense gravity causes the structures to become warped. More material is funneled into their respective black holes as a result, igniting their quasars. Over time, the intense radiation fuels galactic winds that strip away most of the gas from the merging galaxies.

This process results in the formation of an elliptical galaxy. A similar sequence is predicted to happen a few billion years from now when the Milky Way merges with its nearest galactic neighbor, the Andromeda galaxy.

More than 100 double quasars have been discovered in merging galaxies, though none are as old as the two pairs found in this study. The newly discovered quasars are from an era associated with an abundance of quasar formation, about 10 billion years ago. Astronomers had previously suggested there should be myriad dual quasars during that time, but none had been detected until now.

"This truly is the first sample of dual quasars at the peak epoch of galaxy formation with which we can use to probe ideas about how supermassive black holes come together to eventually form a binary," Zakamska said.

The discovery of these four quasars not only informs researchers on the merging of supermassive black holes in the early universe, but also highlights the benefits of employing a variety of techniques to detect and image elusive dual quasars, study team members said.

Although Hubble is the only telescope with a high enough resolution to distinguish these two close quasar pairs, its sharp eye wasn't quite good enough to locate them on its own. Astronomers needed to point Hubble in the right direction, and for that they enlisted the help of the European Space Agency's star-mapping Gaia satellite and the ground-based Sloan Digital Sky Survey to compile a list of possible candidates for Hubble to investigate.

When the researchers then observed the first four targets with Hubble, they found that two of the targets were actually two pairs of close quasars. The researchers said it was a "light bulb moment" that reaffirmed their plans to use Hubble, Sloan and Gaia to search for quasar duos.
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"The new technique can not only discover dual quasars much further away, but it is much more efficient than the methods we've used before," said Xin Liu of the University of Illinois at Urbana-Champaign, who was also part of the study.

The team's research appears in the April 1 online issue of the journal Nature Astronomy.

Hubble: 30 Years and Counting

It's March 2021 and in about another month the Hubble Space Telescope will celebrate 31 years in space observing the universe. In this image celebrating Hubble's 30th birthday, the giant red nebula (NGC 2014) and its smaller blue neighbor (NGC 2020) are part of a vast star-forming region in the Large Magellanic Cloud, a satellite galaxy of the Milky Way, located 163,000 light-years away. The image is nicknamed the "Cosmic Reef," because NGC 2014 resembles part of a coral reef floating in a vast sea of stars. Some of the stars in NGC 2014 are monsters. The nebula's sparkling centerpiece is a grouping of bright, hefty stars, each 10 to 20 times more massive than our Sun. The seemingly isolated blue nebula at lower left (NGC 2020) has been created by a solitary mammoth star 200,000 times brighter than our Sun. The blue gas was ejected by the star through a series of eruptive events during which it lost part of its outer envelope of material. 

NGC 2014

Image Credit: NASA, ESA and STScI

In Planet Formation, It's Location, Location, Location

Astronomers using NASA's Hubble Space Telescope are finding that planets have a tough time forming in the rough-and-tumble central region of the massive, crowded star cluster Westerlund 2. Located 20,000 light-years away, Westerlund 2 is a unique laboratory to study stellar evolutionary processes because it's relatively nearby, quite young, and contains a large stellar population. A three-year Hubble study of stars in Westerlund 2 revealed that the precursors to planet-forming disks encircling stars near the cluster's center are mysteriously devoid of large, dense clouds of dust that in a few million years could become planets. However, the observations show that stars on the cluster's periphery do have the immense planet-forming dust clouds embedded in their disks. Researchers think our solar system followed this recipe when it formed 4.6 billion years ago. So why do some stars in Westerlund 2 have a difficult time forming planets while others do not? It seems that planet formation depends on location, location, location. The most massive and brightest stars in the cluster congregate in the core, which is verified by observations of other star-forming regions. The cluster's center contains at least 30 extremely massive stars, some weighing up to 80 times the mass of the Sun. Their blistering ultraviolet radiation and hurricane-like stellar winds of charged particles blowtorch disks around neighboring lower-mass stars, dispersing the giant dust clouds."Basically, if you have monster stars, their energy is going to alter the properties of the disks around nearby, less massive stars," explained Elena Sabbi, of the Space Telescope Science Institute in Baltimore and lead researcher of the Hubble study.

"You may still have a disk, but the stars change the composition of the dust in the disks, so it's harder to create stable structures that will eventually lead to planets. We think the dust either evaporates away in 1 million years, or it changes in composition and size so dramatically that planets don't have the building blocks to form."

The Hubble observations represent the first time that astronomers analyzed an extremely dense star cluster to study which environments are favorable to planet formation. Scientists, however, are still debating whether bulky stars are born in the center or whether they migrate there. Westerlund 2 already has massive stars in its core, even though it is a comparatively young, 2-million-year-old system.

Using Hubble's Wide Field Camera 3, the researchers found that of the nearly 5,000 stars in Westerlund 2 with masses between 0.1 to 5 times the Sun's mass, 1,500 of them show fluctuations in their light as the stars accrete material from their disks. Orbiting material clumped within the disk would temporarily block some of the starlight, causing brightness fluctuations.

However, Hubble detected the signature of such orbiting material only around stars outside the cluster's packed central region. The telescope witnessed large drops in brightness for as much as 10 to 20 days around 5% of the stars before they returned to normal brightness. They did not detect these dips in brightness in stars residing within four light-years of the center. These fluctuations could be caused by large clumps of dust passing in front of the star. The clumps would be in a disk tilted nearly edge-on to the view from Earth.

"We think they are planetesimals or structures in formation," Sabbi explained. "These could be the seeds that eventually lead to planets in more evolved systems. These are the systems we don't see close to very massive stars. We see them only in systems outside the center."

Thanks to Hubble, astronomers can now see how stars are accreting in environments that are like the early universe, where clusters were dominated by monster stars. So far, the best known nearby stellar environment that contains massive stars is the starbirth region in the Orion Nebula. However, Westerlund 2 is a richer target because of its larger stellar population.

"Hubble's observations of Westerlund 2 give us a much better sense of how stars of different masses change over time, and how powerful winds and radiation from very massive stars affect nearby lower-mass stars and their disks," Sabbi said.

"We see, for example, that lower-mass stars, like our Sun, that are near extremely massive stars in the cluster still have disks and still can accrete material as they grow. But the structure of their disks (and thus their planet-forming capability) seems to be very different from that of disks around stars forming in a calmer environment farther away from the cluster core. This information is important for building models of planet formation and stellar evolution."

This cluster will be an excellent laboratory for follow-up observations with NASA's upcoming James Webb Space Telescope, an infrared observatory. Hubble has helped astronomers identify the stars that have possible planetary structures. With Webb, researchers can study which disks around stars are not accreting material and which disks still have material that could build up into planets.

This information on 1,500 stars will allow astronomers to map a path on how star systems grow and evolve. Webb also can study the chemistry of the disks in different evolutionary phases and watch how they change, and help astronomers determine what influence environment plays in their evolution.

NASA's Nancy Grace Roman Space Telescope, another planned infrared observatory, will be able to perform Sabbi's study on a much larger area.? Westerlund 2 is just a small slice of an immense star-formation region. These vast regions contain clusters of stars with different ages and different densities.

Astronomers could use Roman Space Telescope observations to start to build up statistics on how a star's characteristics, like its mass or outflows, affect its own evolution or the nature of stars that form nearby. The observations could also provide more information on how planets form in tough environments.

Distance from Brightest Stars Is Key to Preserving Primordial Discs

The NASA/ESA Hubble Space Telescope was used to conduct a three-year study of the crowded, massive and young star cluster Westerlund 2. The research found that the material encircling stars near the cluster's centre is mysteriously devoid of the large, dense clouds of dust that would be expected to become planets in a few million years. Their absence is caused by the cluster's most massive and brightest stars that erode and disperse the discs of gas and dust of neighbouring stars. This is the first time that astronomers have analysed an extremely dense star cluster to study which environments are favourable to planet formation. This time-domain study from 2016 to 2019 sought to investigate the properties of stars during their early evolutionary phases and to trace the evolution of their circumstellar environments. Such studies had previously been confined to the nearest, low-density, star-forming regions. Astronomers have now used the Hubble Space Telescope to extend this research to the centre of one of the few young massive clusters in the Milky Way, Westerlund 2, for the first time. Astronomers have now found that planets have a tough time forming in this central region of the cluster. The observations also reveal that stars on the cluster's periphery do have immense planet-forming dust clouds embedded in their discs. To explain why some stars in Westerlund 2 have a difficult time forming planets while others do not, researchers suggest this is largely due to location.

The most massive and brightest stars in the cluster congregate in the core. Westerlund 2 contains at least 37 extremely massive stars, some weighing up to 100 solar masses. Their blistering ultraviolet radiation and hurricane-like stellar winds act like blowtorches and erode the discs around neighbouring stars, dispersing the giant dust clouds.

"Basically, if you have monster stars, their energy is going to alter the properties of the discs," explained lead researcher Elena Sabbi, of the Space Telescope Science Institute in Baltimore, USA.

"You may still have a disc, but the stars change the composition of the dust in the discs, so it's harder to create stable structures that will eventually lead to planets. We think the dust either evaporates away in 1 million years, or it changes in composition and size so dramatically that planets don't have the building blocks to form."

Westerlund 2 is a unique laboratory in which to study stellar evolutionary processes because it's relatively nearby, is quite young, and contains a rich stellar population. The cluster resides in a stellar breeding ground known as Gum 29, located roughly 14,000 light-years away in the constellation of Carina (The Ship's Keel).

The stellar nursery is difficult to observe because it is surrounded by dust, but Hubble's Wide Field Camera 3 can peer through the dusty veil in near-infrared light, giving astronomers a clear view of the cluster. Hubble's sharp vision was used to resolve and study the dense concentration of stars in the central cluster.

"With an age of less than about two million years, Westerlund 2 harbours some of the most massive, and hottest, young stars in the Milky Way," said team member Danny Lennon of the Instituto de Astrofisica de Canarias and the Universidad de La Laguna.

"The ambient environment of this cluster is therefore constantly bombarded by strong stellar winds and ultraviolet radiation from these giants that have masses of up to 100 times that of the Sun."

Sabbi and her team found that of the nearly 5,000 stars in Westerlund 2 with masses between 0.1 and 5 times the Sun's mass, 1,500 of them show dramatic fluctuations in their luminosity, which is commonly accepted as being due to the presence of large dusty structures and planetesimals.

Orbiting material would temporarily block some of the starlight, causing fluctuations in brightness. However, Hubble only detected the signature of dust particles around stars outside the central region. They did not detect these dips in brightness in stars residing within four light-years of the centre.

"We think they are planetesimals or structures in formation," Sabbi explained. "These could be the seeds that eventually lead to planets in more evolved systems. These are the systems we don't see close to very massive stars. We see them only in systems outside the centre."

Thanks to Hubble, astronomers can now see how stars are accreting in environments that are like the early universe, where clusters were dominated by monster stars. So far, the best known nearby stellar environment that contains massive stars is the starbirth region in the Orion Nebula. However, Westerlund 2 is a richer target because of its larger stellar population.

"Westerlund 2 gives us much better statistics on how mass affects the evolution of stars, how rapidly they evolve, and we see the evolution of stellar discs and the importance of stellar feedback in modifying the properties of these systems," said Sabbi. "We can use all of this information to inform models of planet formation and stellar evolution."

This cluster will also be an excellent target for follow-up observations with the upcoming NASA/ESA/CSA James Webb Space Telescope, an infrared observatory. Hubble has helped astronomers identify the stars that have possible planetary structures. With the Webb telescope, researchers will be able to study which discs around stars are not accreting material and which discs still have material that could build up into planets. Webb will also study the chemistry of the discs in different evolutionary phases and watch how they change, to help astronomers determine what role the environment plays in their evolution.

"A major conclusion of this work is that the powerful ultraviolet radiation of massive stars alters the discs around neighbouring stars," said Lennon. "If this is confirmed with measurements by the James Webb Space Telescope, this result may also explain why planetary systems are rare in old massive globular clusters."

Hubble showcases new portrait of Jupiter

The NASA/ESA Hubble Space Telescope reveals the intricate, detailed beauty of Jupiter's clouds in this new image taken on 27 June 2019. It features the planet's trademark Great Red Spot and a more intense colour palette in the clouds swirling in the planet's turbulent atmosphere than seen in previous years. Among the most striking features in the image are the rich colours of the clouds moving toward the Great Red Spot. This huge anticyclonic storm is roughly the diameter of Earth and is rolling counterclockwise between two bands of clouds that are moving in opposite directions toward it. As with previous images of Jupiter taken by Hubble, and other observations from telescopes on the ground, the new image confirms that the huge storm which has raged on Jupiter's surface for at least 150 years continues to shrink. The reason for this is still unknown so Hubble will continue to observe Jupiter in the hope that scientists will be able to solve this stormy riddle. Much smaller storms appear on Jupiter as white or brown ovals that can last as little as a few hours or stretch on for centuries. The worm-shaped feature located south of the Great Red Spot is a cyclone, a vortex spinning in the opposite direction to that in which the Great Red Spot spins. Researchers have observed cyclones with a wide variety of different appearances across the planet. The two white oval features are anticyclones, similar to small versions of the Great Red Spot. The Hubble image also highlights Jupiter's distinct parallel cloud bands. These bands consist of air flowing in opposite directions at various latitudes. They are created by differences in the thickness and height of the ammonia ice clouds; the lighter bands rise higher and have thicker clouds than the darker bands. The different concentrations are kept separate by fast winds which can reach speeds of up to 650 kilometres per hour.

These observations of Jupiter form part of the Outer Planet Atmospheres Legacy (OPAL) programme, which began in 2014.

This initiative allows Hubble to dedicate time each year to observing the outer planets and provides scientists with access to a collection of maps, which helps them to understand not only the atmospheres of the giant planets in the Solar System, but also the atmosphere of our own planet and of the planets in other planetary systems.

New Measurement Adds to Mystery of Universe's Expansion Rate

Astronomers have made a new measurement of how fast the universe is expanding, using an entirely different kind of star than previous endeavors. The revised measurement, which comes from NASA's Hubble Space Telescope (http://www.nasa.gov/hubble), falls in the center of a hotly debated question in astrophysics that may lead to a new interpretation of the universe's fundamental properties. Scientists have known for almost a century that the universe is expanding, meaning the distance between galaxies across the universe is becoming ever more vast every second. But exactly how fast space is stretching, a value known as the Hubble constant, has remained stubbornly elusive. Now, University of Chicago professor Wendy Freedman and colleagues have a new measurement for the rate of expansion in the modern universe, suggesting the space between galaxies is stretching faster than scientists would expect. Freedman's is one of several recent studies that point to a nagging discrepancy between modern expansion measurements and predictions based on the universe as it was more than 13 billion years ago, as measured by the European Space Agency's Planck satellite. As more research points to a discrepancy between predictions and observations, scientists are considering whether they may need to come up with a new model for the underlying physics of the universe in order to explain it. "The Hubble constant is the cosmological parameter that sets the absolute scale, size and age of the universe; it is one of the most direct ways we have of quantifying how the universe evolves," said Freedman. The discrepancy that we saw before has not gone away, but this new evidence suggests that the jury is still out on whether there is an immediate and compelling reason to believe that there is something fundamentally flawed in our current model of the universe."

In a new paper accepted for publication in The Astrophysical Journal, Freedman and her team announced a new measurement of the Hubble constant using a kind of star known as a red giant. Their new observations, made using Hubble, indicate that the expansion rate for the nearby universe is just under 70 kilometers per second per megaparsec (km/sec/Mpc). One parsec is equivalent to 3.26 light-years distance.

This measurement is slightly smaller than the value of 74 km/sec/Mpc recently reported by the Hubble SH0ES (Supernovae H0 for the Equation of State) team using Cepheid variables, which are stars that pulse at regular intervals that correspond to their peak brightness. This team, led by Adam Riess of the Johns Hopkins University and Space Telescope Science Institute, Baltimore, Maryland, recently reported refining their observations to the highest precision to date for their Cepheid distance measurement technique.

How to Measure Expansion
A central challenge in measuring the universe's expansion rate is that it is very difficult to accurately calculate distances to distant objects.

In 2001, Freedman led a team that used distant stars to make a landmark measurement of the Hubble constant. The Hubble Space Telescope Key Project team measured the value using Cepheid variables as distance markers. Their program concluded that the value of the Hubble constant for our universe was 72 km/sec/Mpc.

But more recently, scientists took a very different approach: building a model based on the rippling structure of light left over from the big bang, which is called the cosmic microwave background. The Planck measurements allow scientists to predict how the early universe would likely have evolved into the expansion rate astronomers can measure today. Scientists calculated a value of 67.4 km/sec/Mpc, in significant disagreement with the rate of 74.0 km/sec/Mpc measured with Cepheid stars.

Astronomers have looked for anything that might be causing the mismatch. "Naturally, questions arise as to whether the discrepancy is coming from some aspect that astronomers don't yet understand about the stars we're measuring, or whether our cosmological model of the universe is still incomplete," Freedman said. "Or maybe both need to be improved upon."

Freedman's team sought to check their results by establishing a new and entirely independent path to the Hubble constant using an entirely different kind of star.

Certain stars end their lives as a very luminous kind of star called a red giant, a stage of evolution that our own Sun will experience billions of years from now. At a certain point, the star undergoes a catastrophic event called a helium flash, in which the temperature rises to about 100 million degrees and the structure of the star is rearranged, which ultimately dramatically decreases its luminosity. Astronomers can measure the apparent brightness of the red giant stars at this stage in different galaxies, and they can use this as a way to tell their distance.

The Hubble constant is calculated by comparing distance values to the apparent recessional velocity of the target galaxies - that is, how fast galaxies seem to be moving away. The team's calculations give a Hubble constant of 69.8 km/sec/Mpc - straddling the values derived by the Planck and Riess teams.

"Our initial thought was that if there's a problem to be resolved between the Cepheids and the Cosmic Microwave Background, then the red giant method can be the tie-breaker," said Freedman.

But the results do not appear to strongly favor one answer over the other, say the researchers, although they align more closely with the Planck results.

NASA's upcoming mission, the Wide Field Infrared Survey Telescope (WFIRST), scheduled to launch in the mid-2020s, will enable astronomers to better explore the value of the Hubble constant across cosmic time. WFIRST, with its Hubble-like resolution and 100 times greater view of the sky, will provide a wealth of new Type Ia supernovae, Cepheid variables, and red giant stars to fundamentally improve distance measurements to galaxies near and far.

Ultra-sharp images make old stars look absolutely marvelous

Just as high-definition imaging is transforming home entertainment, it is also advancing how astronomers study the universe. "Ultra-sharp adaptive optics images from the Gemini Observatory allowed us to determine the ages of some of the oldest stars in our galaxy," said Leandro Kerber of the Universidade de Sao Paulo and Universidade Estadual de Santa Cruz, Brazil. Kerber led a large international research team that published their results in the April 2019 issue of the Monthly Notices of the Royal Astronomical Society. Using advanced adaptive optics technology at the Gemini South telescope in Chile, the researchers zoomed in on a cluster of stars known as HP 1. "Removing our atmosphere's distortions to starlight with adaptive optics reveals tremendous details in the objects we study," added Kerber. "Because we captured these stars in such great detail, we were able to determine their advanced age and piece together a very compelling story." That story begins just as the universe was reaching its one-billionth birthday. "This star cluster is like an ancient fossil buried deep in our galaxy's bulge, and now we've been able to date it to a far-off time when the universe was very young," said Stefano Souza, a PhD student at the Universidade de Sao Paulo, Brazil, who worked with Kerber as part of the research team. The team's results date the cluster at about 12.8 billion years, making these stars among the oldest ever found in our galaxy. "These are also some of the oldest stars we've seen anywhere," added Souza. "HP 1 is one of the surviving members of the fundamental building blocks that assembled our galaxy's inner bulge," said Kerber.

Until a few years ago, astronomers believed that the oldest globular star clusters - spherical swarms of up to a million stars - were only located in the outer parts of the Milky Way, while the younger ones resided in the innermost galactic regions.

However, Kerber's study, as well as other recent work based on data from the Gemini Observatory and the Hubble Space Telescope (HST), have revealed that ancient star clusters are also found within the galactic bulge and relatively close to the galactic center.

Globular clusters tell us much about the formation and evolution of the Milky Way. Most of these ancient and massive stellar systems are thought to have coalesced out of the primordial gas cloud that later collapsed to form the spiral disk of our galaxy, while others appear to be the remnant cores of dwarf galaxies shredded by the gravity of our Milky Way.

Of the roughly 160 globular clusters known in our galaxy, about a quarter are located within the greatly obscured and tightly packed central bulge region of the Milky Way. This spherical mass of stars some 10,000 light-years across forms the central hub of the Milky Way (the yolk if you will) which is made primarily of old stars, gas, and dust.

Among the clusters within the bulge, those that are the most metal-poor (lacking in heavier elements) - which includes HP 1 - have long been suspected of being the oldest. HP 1 then is pivotal, as it serves as an excellent tracer of our galaxy's early chemical evolution.

"HP 1 is playing a critical role in our understanding of how the Milky Way formed," Kerber said. "It is helping us to bridge the gap in our understanding between our galaxy's past and its present."

Kerber and his international team used the exquisitely deep high-resolution adaptive optics images from Gemini Observatory as well as archival optical images from the HST to identify faint cluster members, which are essential for age determination. With this rich data set they confirmed that HP 1 is a fossil relic born less than a billion years after the Big Bang, when the universe was in its infancy.

"These results crown an effort of more than two decades with some of the world's premier telescopes aimed at determining accurate chemical abundances with high-resolution spectroscopy," said Beatriz Barbuy of the Universidade de Sao Paulo, coauthor of this paper and a world-renowned expert in this field.

"These Gemini images are the best ground-based photometric data we have. They are at the same level of HST data, allowing us to recover a missing piece in our puzzle: the age of HP 1. From the existence of such old objects, we can attest to the short star formation timescale in the galactic bulge, as well as its fast chemical enrichment."

To determine the cluster's distance, the team used archival ground-based data to identify 11 RR Lyrae variable stars (a type of "standard candle" used to measure cosmic distances) within HP 1.

The observed brightness of these RR Lyrae stars indicate that HP 1 is at a distance of about 21,500 light-years, placing it approximately 6,000 light-years from the galactic center, well within the galaxy's central bulge region.

Kerber and his team also used the Gemini data, as well HST, Very Large Telescope, and Gaia mission data, to refine the orbit of HP 1 within our galaxy. This analysis shows that during HP 1's history, the cluster came as close as about 400 light-years from the galactic center - less than one-tenth of its current distance.

"The combination of high angular resolution and near-infrared sensitivity makes GeMS/GSAOI an extremely powerful tool for studying these compact, highly dust-enshrouded stellar clusters," added Mattia Libralato of the Space Telescope Science Institute, a coauthor on the study.

"Careful characterization of these ancient systems, as we've done here, is paramount to refine our knowledge of our galaxy's formation."

Chris Davis, program officer at the National Science Foundation (NSF) for Gemini, commented, "These fabulous results demonstrate why the development of wide-field, high-resolution imaging at Gemini is key to the observatory's future. The recent NSF award to support the development of a similar system at Gemini North will make routine super-sharp imaging from both hemispheres a reality. These are certainly exciting times for the observatory."

The Gemini observations resolve stars to about 0.1 arcsecond which is one 36 thousandth of a degree. This is comparable to separating two automobile headlamps from approximately 1,500 miles, or 2,500 kilometers, away (the distance from Manaus to Sao Paulo in Brazil, or from San Francisco to Dallas in the USA).

This resolution was obtained using the Gemini South Adaptive Optics Imager (GSAOI) - a near-infrared adaptive optics camera used with the Gemini Multi-conjugate adaptive optics System (GeMS). GeMS is an advanced adaptive optics system utilizing three deformable mirrors to correct for distortions imparted on starlight by turbulence in layers of our atmosphere.

Hubble in Safe Mode as Gyro Issues are Diagnosed

NASA is working to resume science operations of the Hubble Space Telescope after the spacecraft entered safe mode on Friday, October 5, shortly after 6:00 p.m. EDT. Hubble's instruments still are fully operational and are expected to produce excellent science for years to come. Hubble entered safe mode after one of the three gyroscopes (gyros) actively being used to point and steady the telescope failed. Safe mode puts the telescope into a stable configuration until ground control can correct the issue and return the mission to normal operation. Built with multiple redundancies, Hubble had six new gyros installed during Servicing Mission-4 in 2009. Hubble usually uses three gyros at a time for maximum efficiency, but can continue to make scientific observations with just one. The gyro that failed had been exhibiting end-of-life behavior for approximately a year, and its failure was not unexpected; two other gyros of the same type had already failed. The remaining three gyros available for use are technically enhanced and therefore expected to have significantly longer operational lives.Two of those enhanced gyros are currently running. Upon powering on the third enhanced gyro that had been held in reserve, analysis of spacecraft telemetry indicated that it was not performing at the level required for operations.

As a result, Hubble remains in safe mode. Staff at NASA's Goddard Space Flight Center and the Space Telescope Science Institute are currently performing analyses and tests to determine what options are available to recover the gyro to operational performance.

Science operations with Hubble have been suspended while NASA investigates the anomaly. An Anomaly Review Board, including experts from the Hubble team and industry familiar with the design and performance of this type of gyro, is being formed to investigate this issue and develop the recovery plan. If the outcome of this investigation results in recovery of the malfunctioning gyro, Hubble will resume science operations in its standard three-gyro configuration.

If the outcome indicates that the gyro is not usable, Hubble will resume science operations in an already defined "reduced-gyro" mode that uses only one gyro. While reduced-gyro mode offers less sky coverage at any particular time, there is relatively limited impact on the overall scientific capabilities.

Study of material surrounding distant stars shows Earth's ingredients 'pretty normal'

The Earth's building blocks seem to be built from 'pretty normal' ingredients, according to researchers working with the world's most powerful telescopes. Scientists have measured the compositions of 18 different planetary systems from up to 456 light years away and compared them to ours, and found that many elements are present in similar proportions to those found on Earth. This is amongst the largest examinations to measure the general composition of materials in other planetary systems, and begins to allow scientists to draw more general conclusions on how they are forged, and what this might mean for finding Earth-like bodies elsewhere. "Most of the building blocks we have looked at in other planetary systems have a composition broadly similar to that of the Earth", said researcher Dr Siyi Xu of the Gemini Observatory in Hawaii, who was presenting the work at the Goldschmidt conference in Boston. The first planets orbiting other stars were only found in 1992 (this was orbiting a pulsar), since then scientists have been trying to understand whether some of these stars and planets are similar to our own solar system. "It is difficult to examine these remote bodies directly. Because of the huge distances involved, their nearby star tends to drown out any electromagnetic signal, such as light or radio waves" said Siyi Xu. "So we needed to look at other methods".

Because of this, the team decided to look at how the planetary building blocks affect signals from white dwarf stars. These are stars which have burnt off most of their hydrogen and helium, and shrunk to be very small and dense - it is anticipated that our Sun will become a white dwarf in around 5 billion years.

Dr Xu continued, "White dwarfs' atmospheres are composed of either hydrogen or helium, which give out a pretty clear and clean spectroscopic signal. However, as the star cools, it begins to pull in material from the planets, asteroids, comets and so on which had been orbiting it, with some forming a dust disk, a little like the rings of Saturn.

"As this material approaches the star, it changes how we see the star. This change is measurable because it influences the star's spectroscopic signal, and allows us to identify the type and even the quantity of material surrounding the white dwarf. These measurements can be extremely sensitive, allowing bodies as small as an asteroid to be detected".

The team took measurements using spectrographs on the Keck telescope in Hawaii, the world's largest optical and infrared telescope, and on the Hubble Space Telescope.

Siyi Xu continued, "In this study, we have focused on the sample of white dwarfs with dust disks. We have been able to measure calcium, magnesium, and silicon content in most of these stars, and a few more elements in some stars. We may also have found water in one of the systems, but we have not yet quantified it: it's likely that there will be a lot of water in some of these worlds. For example, we've previously identified one star system, 170 light years away in the constellation Bootes, which was rich in carbon, nitrogen and water, giving a composition similar to that of Halley's Comet. In general though, their composition looks very similar to bulk Earth.

This would mean that the chemical elements, the building blocks of earth are common in other planetary systems. From what we can see, in terms of the presence and proportion of these elements, we're normal, pretty normal. And that means that we can probably expect to find Earth-like planets elsewhere in our Galaxy".

Dr Xu continued "This work is still on-going and the recent data release from the Gaia satellite, which so far has characterized 1.7 billion stars, has revolutionized the field. This means we will understand the white dwarfs a lot better. We hope to determine the chemical compositions of extrasolar planetary material to a much higher precision"

Professor Sara Seager, Professor of Planetary Science at Massachusetts Institute of Technology, is also the deputy science director of the recently-launched TESS (Transiting Exoplanet Survey Satellite) mission, which will search for exoplanets. She said:

"It's astonishing to me that the best way to study exoplanet interiors is by planets ripped apart and absorbed by their white dwarf host star. It is great to see progress in this research area and to have solid evidence that planets with Earth-like compositions are common--fueling our confidence that an Earth-like planet around a very nearby normal star is out there waiting to be found".

Hubble spots most distant star ever observed

If we could travel halfway across the Universe, we would find a huge star,christened Icarus, that was found after its discovery to be the most distant star from Earth. Normally, it would be impossible to detect it, even using the most powerful telescopes currently available, were it not for a quirk of nature that had amplified its brightness such that it could be detected with the Hubble Space Telescope. The discovery has also helped to test a new theory of dark matter and to study what clusters of galaxies are made of. The results of this study were published today in the journal Nature Astronomy. Icarus is located in a spiral galaxy that is so far from Earth that its light has taken 9000 million years to reach us. According to Patrick Kelly, a researcher from the University of Minnesota and leader of the team, 'This is the first time we've seen an individual star so far away. We can see very distant galaxies, but this star is a hundred times more distant than the next farthest star that we can observe, unless we include supernova explosions as stars.' The cosmic quirk that has allowed us to see this star is a phenomenon known as 'gravitational lensing'. 

MACS J1149+2223 Lensed Star 1

The gravity of an extremely massive cluster of galaxies acts like a giant cosmic magnifying glass that amplifies the light from the most distant objects. The gravitational lens that has enabled us to see Icarus is created by the galaxy cluster known as MACS J1149+2223, located some 5000 million light years from Earth. Combining this lens with Hubble's resolution and sensitivity has enabled an analysis to be performed of this distant star.

The research team that has participated in this study includes, among other workers, Jose M. Diego of the Instituto de Fisica de Cantabria (IFCA), Steven Rodney of the University of South Carolina, Columbia (USA), Pablo G. Perez Gonzalez of the Universidad Complutense de Madrid (UCM), Tom Broadhurst of the University of the Pais Vasco (UPV), and Ismael Perez Fournon (IAC and ULL). Patrick Kelly and his coworkers detected sudden changes in the star's brightness, produced by the microlens brought about by the gravitationaleffect of stars belonging to the cluster.

Although its official designation is 'MACS J1149+2223 Lensed Star 1', the team decided to name the star after the character in Greek mythology who flew too close to the Sun with wings and feathers made of wax. Just like Icarus, the light from this star, on its journey towards Earth, passed so close to a Sun-like star in the intergalactic region of the MACS J1149+2223 cluster that its brightness was amplified by a factor of about 2000, thus attaining the glory of its Greek namesake.

'We were able to establish that Icarus is a blue supergiant star, a type of star that is much bigger, more massive, hotter and possibly thousands of times brighter than the Sun. But, at its great distance, it would be impossible to observe it as an individual star, even with the Hubble, were it not for the gravitational lens phenomenon,' comments Ismael Perez Fournon.

Pablo Perez Gonzalez (UCM) explains, 'Until 2016 is was only possible to observe individual stars in galaxies close to the Milky Way. Today, we are witnessing an individual star, very like Rigel, which is halfway across the Universe, and which, indeed, no longer exists.'

The detection of Icarus with the Hubble was so extraordinary that, when it was discovered, telescopes worldwide started to observe it. In Spain, special observing time was applied for on the Gran Telescopio Canarias (GTC), the largest optical-infrared telescope in the world. It turned out, according to Perez Gonzalez, that the GTC 'was the only telescope to detect this star so distant from Earth, given that Icarus is so faint.'

The discovery of Icarus is exceptional not only in terms of the detection of such a distant star. Detecting the amplification of an individual star's brightness enables us to study the nature of the cluster's dark matter content, thus putting to the test a theory of the nature of the dark matter of the cluster that shows that most of it is in the form of primordial black holes.

According to Jose M. Diego (IFCA), first author of the theoretical paper accompanying the Nature Astronomy article, 'If the dark matter consisted of black holes similar to those detected by LIGO (Laser Interferometer Gravitational-Wave Observatory), the signal observed from Icarus would have been very different, which enables us to discard these types of candidates.' Tome Broadhurst (UPV) adds, 'this type of study will in future enable us to set limits on other dark matter models, such as those that postulate superlight particles of matter and their quantum effects.'

Also, in May 2016, another image appeared next to Icarus that seems to suggest that we are not dealing with an individual star. We could instead be talking about a binary system, with two stars in orbit around each other.