Just in time for summer fireworks season, the Hubble science team has released an image of Herbig-Haro 110, a young star with geysers of hot gas skyrocketing away through interstellar space. Twin jets of heated gas are being ejected in opposite directions from this star that is still in the formation process. The Hubble team says these outflows are fueled by gas falling onto the young star, which is surrounded by a disc of dust and gas. If the disc is the fuel tank, the star is the gravitational engine, and the jets are the exhaust. And even though the plumes of gas look like whiffs of smoke, they are actually billions of times less dense than the smoke from a fireworks display.
More information about this image from the HubbleSite:
Herbig-Haro (HH) objects come in a wide array of shapes, but the basic configuration stays the same. Twin jets of heated gas, ejected in opposite directions away from a forming star, stream through interstellar space. Astronomers suspect that these outflows are fueled by gas accreting onto a young star surrounded by a disk of dust and gas. The disk is the “fuel tank,” the star is the gravitational engine, and the jets are the exhaust.
When these energetic jets slam into colder gas, the collision plays out like a traffic jam on the interstate. Gas within the shock front slows to a crawl, but more gas continues to pile up as the jet keeps slamming into the shock from behind. Temperatures climb sharply, and this curving, flared region starts to glow. These “bow shocks” are so named because they resemble the waves that form at the front of a boat.
In the case of the single HH 110 jet, astronomers observe a spectacular and unusual permutation on this basic model. Careful study has repeatedly failed to find the source star driving HH 110, and there may be good reason for this: perhaps the HH 110 outflow is itself generated by another jet.
Astronomers now believe that the nearby HH 270 jet grazes an immovable obstacle — a much denser, colder cloud core — and gets diverted off at about a 60-degree angle. The jet goes dark and then reemerges, having reinvented itself as HH 110.
The jet shows that these energetic flows are like the erratic outbursts from a Roman candle. As fast-moving blobs of gas catch up and collide with slower blobs, new shocks arise along the jet’s interior. The light emitted from excited gas in these hot blue ridges marks the boundaries of these interior collisions. By measuring the current velocity and positions of different blobs and hot ridges along the chain within the jet, astronomers can effectively “rewind” the outflow, extrapolating the blobs back to the moment when they were emitted. This technique can be used to gain insight into the source star’s history of mass accretion.
This image is a composite of data taken with Hubble’s Advanced Camera for Surveys in 2004 and 2005 and the Wide Field Camera 3 in April 2011.
Since its discovery in 2005, exoplanet HD 189733b has been one of the most-observed extra solar planets, due to its size, compact orbit, proximity to Earth and enticing blue-sky atmosphere. But astronomers using the Hubble Space Telescope and the Swift Telescope have witnessed dramatic changes in the planet’s upper atmosphere following a violent flare from its parent which bathed the planet in intense X-ray radiation. The scientists say being able to watch the action gives a tantalizing glimpse of the changing climates and weather on planets outside our Solar System.
While HD 189733b has a blue sky like Earth, it is one of the many “hot Jupiters” that have been the easiest for exoplanet hunters to find: huge gas planets that orbit extremely close to its star. HD 189733 lies extremely close to its star, called HD 189733A, just one thirtieth the distance Earth is from the Sun, whipping around the star in 2.2 days. Additionally, the system is just 63 light-years away, so close that its star can be seen with binoculars near the famous Dumbbell Nebula.
Even though its star is slightly smaller and cooler than the Sun, this makes the planet’s climate exceptionally hot, at above 1000 degrees Celsius, and the upper atmosphere is battered by energetic extreme-ultraviolet and X-ray radiation.
Even though HD 189733b’s atmosphere wasn’t thought to be evaporating (like a similar exoplanet called Osiris, or HD 209458b) astronomers knew the potential was there. The atmospheric gases extend far beyond the planetary “surface” allowing stellar light to pass through, and in previous observations astronomers were able to get a peek into what chemical compounds surround HD 189733b. From this analysis, scientists deduced that water and methane is contained in the atmosphere; and later, the Spitzer space telescope even mapped the temperature distribution around the globe. Additional research indicated a thin layer of particles exists in the upper atmosphere of HD 189733b, creating thin reflective clouds.
Astronomer Alain Lecavelier des Etangs from at the Paris Institute of Astrophysics in France led a team using Hubble to observe the atmosphere of this planet during two periods in early 2010 and late 2011, as it was silhouetted against its parent star. While backlit in this way, the planet’s atmosphere imprints its chemical signature on the starlight, allowing astronomers to decode what is happening on scales that are too tiny to image directly. They were hoping to observe the atmosphere evaporating away, but were disappointed in 2010.
“The first set of observations were actually disappointing,” Lecavelier said, “since they showed no trace of the planet’s atmosphere at all. We only realized we had chanced upon something more interesting when the second set of observations came in.”
The team’s follow-up observations, made in 2011, showed a dramatic change, with clear signs of a plume of gas being blown from the planet at a rate of at least 1000 tons per second, at speeds of 300,000 mph, giving the planet a comet-like appearance.
“We hadn’t just confirmed that some planets’ atmospheres evaporate,” Lecavelier said, “we had watched the physical conditions in the evaporating atmosphere vary over time. Nobody had done that before.”
So why was the atmosphere’s condition changing?
Despite the extreme temperature of the planet, the atmosphere is not hot enough to evaporate at the rate seen in 2011. Instead the evaporation is thought to be driven by the intense X-ray and extreme-ultraviolet radiation from the parent star, which is about 20 times more powerful than that of our own Sun. Taking into account also that HD 189733b is a giant planet very close to its star, then it must suffer an X-ray dose 3 million times higher than the Earth.
Because X-rays and extreme ultraviolet starlight heat the planet’s atmosphere and likely drive its escape, the team also monitored the star with Swift’s X-ray Telescope (XRT). On Sept. 7, 2011, just eight hours before Hubble was scheduled to observe the transit, Swift was monitoring the star when it unleashed a powerful flare. It brightened by 3.6 times in X-rays, a spike occurring atop emission levels that already were greater than the sun’s.
“The planet’s close proximity to the star means it was struck by a blast of X-rays tens of thousands of times stronger than the Earth suffers even during an X-class solar flare, the strongest category,” said co-author Peter Wheatley, a physicist at the University of Warwick in England.
After accounting for the planet’s enormous size, the team notes that HD 189733b encountered about 3 million times as many X-rays as Earth receives from a solar flare at the threshold of the X class.
“X-ray emissions are a small part of the star’s total output, but it is the part that it is energetic enough to drive the evaporation of the atmosphere,” said co-author Peter Wheatley from the University of Warwick, in the UK. “This was the brightest X-ray flare from HD 189733A of several observed to date, and it seems very likely that the impact of this flare on the planet drove the evaporation seen a few hours later with Hubble.”
The team also said the changes in the star’s output may mean it undergoes a seasonal process similar to the Sun’s 11-year sunspot cycle.
The team hopes to clarify the changes they witnessed using future observations with Hubble and ESA’s XMM-Newton X-ray space telescope, but say there is no question that the planet was hit by a stellar flare, and no question that the rate of evaporation of the planet’s atmosphere shot up.
This research shows the benefits of collaborative research between missions, as Swift saw the flare, and Hubble saw the massive amount of gas stripped out of the planet’s atmosphere. It also gives potential for future research, to watch for changes in both the star and atmospheres of other worlds.
This video from NASA’s Goddard Spaceflight Center provides additional information:
Lead image caption: This artist’s rendering illustrates the evaporation of HD 189733b’s atmosphere in response to a powerful eruption from its host star. NASA’s Hubble Space Telescope detected the escaping gases and NASA’s Swift satellite caught the stellar flare. Credit: NASA’s Goddard Space Flight Center.
Second image caption: Swift’s Ultraviolet/Optical Telescope captured this view of HD 189733b’s star on Sept. 14, 2011. The image is 6 arcminutes across. Credit: NASA/Swift/Stefan Immler
The image above looks like a classic example of a collision between two galaxies. However, Hubble scientists have determined, this is just an illusion, a trick of perspective. The two galaxies, NGC 3314A and B are actually tens of millions of light years apart instead of merging in a galactic pileup. From our vantage point on Earth the two just happen to appear to be overlapping at great distances from each other.
How did the Hubble scientists figure this out? The biggest hint as to whether galaxies are interacting is usually their shapes. The immense gravitational forces involved in galactic mergers are enough to pull a galaxy out of shape long before it actually collides. Deforming a galaxy like this does not just warp its structure, but it can trigger new episodes of star formation, usually visible as bright blue stars and glowing nebulae.
In the case of NGC 3314, there is some deformation in the foreground galaxy (called NGC 3314A, NGC 3314B lies in the background), but the Hubble team says this is almost certainly misleading. NGC 3314A’s deformed shape, particularly visible below and to the right of the core, where streams of hot blue-white stars extend out from the spiral arms, is not due to interaction with the galaxy in the background.
Studies of the motion of the two galaxies indicate that they are both relatively undisturbed, and that they are moving independently of each other. This indicates in turn that they are not, and indeed have never been, on any collision course. NGC 3314A’s warped shape is likely due instead to an encounter with another galaxy, perhaps nearby NGC 3312 (visible to the north in wide-field images) or another nearby galaxy.
The chance alignment of the two galaxies is more than just a curiosity, though. It greatly affects the way the two galaxies appear to us.
NGC 3314B’s dust lanes, for example, appear far lighter than those of NGC 3314A. This is not because that galaxy lacks dust, but rather because they are lightened by the bright fog of stars in the foreground. NGC 3314A’s dust, in contrast, is backlit by the stars of NGC 3314B, silhouetting them against the bright background.
Such an alignment of galaxies is also helpful to astronomers studying gravitational microlensing, a phenomenon that occurs when stars in one galaxy cause small perturbations in the light coming from a more distant one. Indeed, the observations of NGC 3314 that led to this image were carried out in order to investigate this phenomenon.
This mosaic image covers a large field of view (several times the size of an individual exposure from Hubble’s Advanced Camera for Surveys). Thanks to a long exposure time of more than an hour in total exposure time for every frame, the image shows not only NGC 3314, but also many other more distant galaxies in the background.
The color composite was produced from exposures taken in blue and red light.
Image caption: The Hubble Space Telescope has produced an incredibly detailed image of a pair of overlapping galaxies called NGC 3314. While the two galaxies look as if they are in the midst of a collision, this is in fact a trick of perspective: the two are in chance alignment from our vantage point. Credit: NASA, ESA, the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration, and W. Keel (University of Alabama)
The stars and dust of spiral galaxy NGC 891 seen by Hubble edge-on
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Like the blade of a magical weapon from a fantasy tale, the northern edge of spiral galaxy NGC 891 is captured by the Hubble Space Telescope, glowing with the light of billions of stars and interwoven with dark clouds of dust and cold gas.
In reality this cosmic blade is enormous. About the same size as our galaxy, NGC 891 is approximately 100,000 light-years in diameter, making the section visible here around 40,000 light-years in length.
Unlike the Milky Way, however, NGC 891 is unbarred and also exhibits many more filaments of dark gas and dust. Astronomers suggest that these are the result of star formation and supernovae, both of which can expel vast amounts of interstellar material far out into space.
The few bright stars in the foreground are located in our own galaxy.
NGC 891 is located in the constellation Andromeda and lies about 30 million light-years away… that means the light captured by Hubble’s Advanced Camera for Surveys to create the image above began its journey 35 million years after the asteroid impact that led to the extinction of the dinosaurs, and about 26 million years before our ancient African ancestors began walking upright. That may sound like a long trip but, as Douglas Adams so eloquently said, “that’s just peanuts to space!”
Astronomers have found four nearby white dwarf stars surrounded by disks of material that could be the remains of rocky planets much like Earth — and one star in particular appears to be in the act of swallowing up what’s left of an Earthlike planet’s core.
The research, announced today by the Royal Astronomical Society, gives a chilling look at the eventual fate that may await our own planet.
Astronomers from the University of Warwick used Hubble to identify the composition of four white dwarfs’ atmospheres, found during a survey of over 80 such stars located within 100 light-years of the Sun. What they found was a majority of the material was composed of elements found in our own Solar System: oxygen, magnesium, silicon and iron. Together these elements make up 93% of our planet.
In addition, a curiously low ratio of carbon was identified, indicating that rocky planets were at one time in orbit around the stars.
Since white dwarfs are the leftover cores of stellar-mass stars that have burnt through all their fuel, the material in their atmosphere is likely the leftover bits of planets. Once held in safe, stable orbits, when their stars neared the ends of their lives they expanded, possibly engulfing the innermost planets and disrupting the orbits of others, triggering a runaway collision effect that eventually shattered them all, forming an orbiting cloud of debris.
This could very well be what happens to our Solar System in four or five billion years.
“What we are seeing today in these white dwarfs several hundred light years away could well be a snapshot of the very distant future of the Earth,” said Professor Boris Gänsicke of the Department of Physics at the University of Warwick, who led the study. “During the transformation of the Sun into a white dwarf, it will lose a large amount of mass, and all the planets will move further out. This may destabilise the orbits and lead to collisions between planetary bodies as happened in the unstable early days of our solar systems.”
One of the white dwarfs studied, labeled PG0843+516, may even be actively eating the remains of an once-Earthlike world’s core.
The researchers identified an abundance of heavier elements like iron, nickel and sulphur in the atmosphere surrounding PG0843+516. These elements are found in the cores of terrestrial planets, having sunk into their interiors during the early stages of planetary formation. Finding them out in the open attests to the destruction of a rocky world like ours.
Of course, being heavier elements, they will be the first to be accreted by their star.
“It is entirely feasible that in PG0843+516 we see the accretion of such fragments made from the core material of what was once a terrestrial exoplanet,” Prof. Gänsicke said.
It’s an eerie look into a distant future, when Earth and the inner planets could become just some elements in a cloud.
Bright spots of Uranus' short-lived auroras have been imaged with the Hubble Space Telescope.
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Astronomers have finally succeeded in capturing the first Earth-based images of the curious and fleeting auroras of Uranus using the Hubble Space Telescope, careful planning… and no small amount of luck.
Unlike Earthly auroras, whose long-lived curtains of glowing green, red and purple have been the subject of countless stunning photos over the past months, Uranus’ auroras are relatively dim and short-lived, lasting only several minutes at most. They were first witnessed on Uranus by Voyager 2 in 1986, but never by any Earth-based telescopes until November of 2011. Using Hubble, an international team of astronomers led by Laurent Lamy from the Observatoire de Paris in Meudon, France spotted two instances of auroras on the distant planet… once on November 16 and again on the 29th.
Two instances of Uranian aurora imaged in Nov. 2011. (L. Lamy)
Auroras are known to be created by a planet’s magnetosphere, which on Earth is aligned closely with the rotational axis — which is why auroras are seen nearest the polar latitudes. But Uranus’ magnetic field is quite offset from its rotational axis, which in turn is tipped nearly 98 degrees relative to its orbital path. In other words, Uranus travels around the Sun rolling on its side! And with a 60-degree difference between its magnetic and rotational axis, nothing on Uranus seems to point quite where it should. This — along with its 2.5-billion-mile (4 billion km) distance — makes for a “very poorly known” magnetic field.
“This planet was only investigated in detail once, during the Voyager flyby, dating from 1986. Since then, we’ve had no opportunities to get new observations of this very unusual magnetosphere,” said Laurent Lamy, lead author of the team’s paper Earth-based detection of Uranus’ aurorae.
Rather than rings of bright emissions, as witnessed on Earth as well as Saturn and Jupiter, the Uranian auroras appeared as bright spots of activity on the planet’s daytime side — most likely a result of Uranus’ peculiar orientation, as well as its seasonal alignment.
It’s not yet known what may be happening on Uranus’ night side, which is out of view of Hubble.
When Voyager 2 passed by Uranus in 1986 the planet was tipped such that its rotational axis was aimed toward the Sun. This meant that its magnetic axis — offset by 60 degrees — was angled enough to encounter the solar wind in much the same way that Earth’s does. This created nightside auroras similar to Earth’s that Voyager saw.
By 2011, however, Uranus — which has an 84-year-long orbit — was near equinox and as a result its magnetic axis was nearly perpendicular with its orbital plane, aiming each end directly into the solar wind once a day. This makes for very different kinds of auroras than what was seen by Voyager; in fact, there’s really nothing else like it that astronomers know of.
“This configuration is unique in the solar system,” said Lamy.
Further investigations of Uranus’ auroras and magnetic field can offer insight into the dynamics of Earth’s own magnetosphere and how it interacts with the solar wind, which in turn affects our increasingly technological society.
The team’s paper will be published Saturday in Geophysical Research Letters, a journal of the American Geophysical Union.
Although somewhat blobby and deformed, this is in fact a spiral galaxy, located in the southern constellation Hydra. Imaged by Hubble as part of a survey of galactic bulges, NGC 4980 exhibits what’s called a “pseudobulge” — an inline central concentration of stars whose similar spiral motion extends right down into its core.
As opposed to classical bulges, in which stars orbit their galaxy’s core in all directions, pseudobulges are made up of stars that continue along the spiral motion of the galactic arms all the way into the center. Pseudobulges are typically seen to contain stars that are the same age as most of the others in the galaxy.
In contrast, classical bulges usually contain stars older than those found in the disk, leading astrophysicists to believe that galaxies with classical bulges had undergone one or more collisions with other galaxies during their evolution.
Our own Milky Way is thought to have a pseudobulge, while some spiral galaxies have no discernible bulge at all.
This image is composed of exposures taken in visible and infrared light by Hubble’s Advanced Camera for Surveys. The image is approximately 3.3 by 1.5 arcminutes in size. NGC 4980 is located about 80 million light-years from Earth.
New Hubble image of Messier 9 cluster resolves individual stars (NASA/ESA)
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First discovered by Charles Messier in 1764, the globular cluster Messier 9 is a vast swarm of ancient stars located 25,000 light-years away, close to the center of the galaxy. Too distant to be seen with the naked eye, the cluster’s innermost stars have never been individually resolved… until now.
This image from the Hubble Space Telescope is the most detailed view yet into Messier 9, capturing details of over 250,000 stars within it. Stars’ shape, size and color can be determined — giving astronomers more clues as to what the cluster’s stars are made of. (Download a large 10 mb JPEG file here.)
Hot blue stars as well as cooler red stars can be seen in Messier 9, along with more Sun-like yellow stars.
Unlike our Sun, however, Messier 9’s stars are nearly ten billion years old — twice the Sun’s age — and are made up of much less heavy elements.
Since heavy elements (such as carbon, oxygen and iron) are formed inside the cores of stars and dispersed into the galaxy when the stars eventually go supernova, stars that formed early on were birthed from clouds of material that weren’t yet rich in such elements.
Zoom into the Messier 9 cluster with a video from NASA and the European Space Agency below:
The Hubble Space Telescope is a project of international cooperation between ESA and NASA. See more at www.spacetelescope.org.
Image credit: NASA & ESA. Video: NASA, ESA, Digitized Sky Survey 2, N. Risinger (skysurvey.org)
The barred spiral galaxy NGC 1073, which is found in the constellation of Cetus (The Sea Monster). Credit: NASA & ESA
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Is this what we look like? Astronomers don’t know for sure exactly what the Milky Way looks like, but searching out other barred spiral galaxies like this one is helping scientists to learn more about our home. Galaxy NGC 1073 is located in the constellation of Cetus (The Sea Monster).Most of the known spiral galaxies have a bar structure in their center, and this new image offer a stunning, if not clear view of one of these types of galaxies.
One piece of information that might be available from a central bar is the galaxy’s age. Some astronomers have suggested that the formation of a this structure might signal a spiral galaxy’s passage from intense star-formation into adulthood. Two-thirds of nearby, younger galaxies have the bar, while only a fifth of older, more distant spirals have one.
While Hubble’s image of NGC 1073 is in some respects an archetypal portrait of a barred spiral, the Hubble team have pointed out a couple of quirks.
One, ironically, is almost — but not quite — invisible to optical telescopes like Hubble. In the upper left part of the image, a rough ring-like structure of recent star formation hides a bright source of X-rays. Called IXO 5, this X-ray source is likely to be a binary system featuring a black hole and a star orbiting each other. Comparing X-ray observations from the Chandra spacecraft with this Hubble image, astronomers have narrowed the position of IXO 5 down to one of two faint stars visible here. However, X-ray observations with current instruments are not precise enough to conclusively determine which of the two it is.
Hubble’s image does not only tell us about a galaxy in our own cosmic neighborhood, however. We can also discern glimpses of objects much further away, whose light tells us about earlier eras in cosmic history.
Right across Hubble’s field of view, more distant galaxies are peering through NGC 1073, with several reddish examples appearing clearly in the top left part of the frame.
More intriguing still, three of the bright points of light in this image are neither foreground stars from the Milky Way, nor even distant stars in NGC 1073. In fact they are not stars at all. They are quasars, incredibly bright sources of light caused by matter heating up and falling into supermassive black holes in galaxies literally billions of light-years from us. The chance alignment through NGC 1073, and their incredible brightness, might make them look like they are part of the galaxy, but they are in fact some of the most distant objects observable in the Universe.
The Fomalhaut b photograph. Credit: NASA, ESA, and P. Kalas (University of California, Berkeley, USA)
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When the Hubble Space Telescope photographed the apparent exoplanet Fomalhaut b in 2008, it was regarded as the first visible light image obtained of a planet orbiting another star. The breakthrough was announced by a research team led by Paul Kalas of the University of California, Berkeley. The planet was estimated to be approximately the size of Saturn, but no more than three times Jupiter’s mass, or perhaps smaller than Saturn according to some other studies, and might even have rings. It resides within a debris ring which encircles the star Fomalhaut, about 25 light-years away.
Another team at Princeton, however, has just announced that they believe the original findings are in error, and that the planet is actually a dust cloud, based on new observations by the Spitzer Space Telescope. Their paper has just been accepted by the Astrophysical Journal.
According to the abstract:
The nearby A4-type star Fomalhaut hosts a debris belt in the form of an eccentric ring, which is thought to be caused by dynamical influence from a giant planet companion. In 2008, a detection of a point-source inside the inner edge of the ring was reported and was interpreted as a direct image of the planet, named Fomalhaut b. The detection was made at ~600–800 nm, but no corresponding signatures were found in the near-infrared range, where the bulk emission of such a planet should be expected. Here we present deep observations of Fomalhaut with Spitzer/IRAC at 4.5 µm, using a novel PSF subtraction technique based on ADI and LOCI, in order to substantially improve the Spitzer contrast at small separations. The results provide more than an order of magnitude improvement in the upper flux limit of Fomalhaut b and exclude the possibility that any flux from a giant planet surface contributes to the observed flux at visible wavelengths. This renders any direct connection between the observed light source and the dynamically inferred giant planet highly unlikely. We discuss several possible interpretations of the total body of observations of the Fomalhaut system, and find that the interpretation that best matches the available data for the observed source is scattered light from transient or semi-transient dust cloud.
Kalas has responded to the new study, saying that they considered the dust cloud possibility but ruled it out for various reasons. For one thing, Spitzer lacks the light sensitivity to detect a Saturn-sized planet, and bright rings could also explain the optical characteristics observed. He says, “We welcome the new Spitzer data, but we don’t really agree with this interpretation.”
The Princeton team, interestingly, thinks that there may be a real planet orbiting Fomalhaut, but still hiding from detection. From the paper:
In particular, we find that there is almost certainly no direct flux from a planet contributing to the visible-light signature. This, in combination with the existing body of data for the Fomalhaut system, strongly implies that the dynamically inferred giant planet companion and the visible-light point source are physically unrelated. This in turn implies that the ‘real’ Fomalhaut b still hides in the system. Although we do find a tentative point source in our images that could in principle correspond to this object, its significance is too low to distinguish whether it is real or not at this point.
Of course it will be disappointing if Fomalhaut b does turn out to not be a planet after all, but let’s not forget that thousands of other ones are being discovered and confirmed. There may occasionally be hits-and-misses, but so far the planetary hunt overall has been nothing short of a home run…
