Category: Hubble

This NASA/ESA Hubble Space Telescope image reveals a pair of half a light-year long interstellar ‘twisters’, eerie twisted funnel structures, in the heart of the Lagoon Nebula (M8).

The central hot star, O Herschel 36 (shown here on left, red), is the primary source of the ionising radiation for the brightest region in the nebula, called the ‘Hourglass’. Other hot stars, also present in the nebula, are ionising the outer visible parts of the nebulous material.

This ionising radiation heats up and ‘evaporates’ the surfaces of the clouds (seen as a blue ‘mist’ at the right of the image), and drives violent stellar winds which tear into the cool clouds.

Analogous to the phenomena of tornadoes on Earth, the large difference in temperature between the hot surface and cold interior of the clouds, combined with the pressure of starlight, may produce strong horizontal ‘windshear’ to twist the clouds into their tornado-like appearance.

The Lagoon Nebula and nebulae in other galaxies are sites where new stars are being born from dusty molecular clouds. These regions are the ‘space laboratories’ for astronomers to study how stars form and the interactions between the winds from stars and the gas nearby. By studying the wealth of data revealed by Hubble, astronomers will understand better how stars form in the nebulae.

These colour-coded images are the combination of individual exposures taken in 1995 with Hubble’s Wide Field and Planetary Camera 2 (WFPC2).

Original Source: ESA News Release

Like a photographer clicking random snapshots of a crowd of people, NASA’s Hubble Space Telescope has taken a view of an eclectic mix of galaxies. In taking this picture, Hubble’s Advanced Camera for Surveys was not looking at any particular target. The camera was taking a picture of a typical patch of sky, while Hubble’s infrared camera was viewing a target in an adjacent galaxy-rich region.

The jumble of galaxies in this image, taken in September 2003, includes a yellow spiral whose arms have been stretched by a possible collision [lower right]; a young, blue galaxy [top] bursting with star birth; and several smaller, red galaxies.

But the most peculiar-looking galaxy of the bunch ? the dramatic blue arc in the center of the photo ? is actually an optical illusion. The blue arc is an image of a distant galaxy that has been smeared into the odd shape by a phenomenon called gravitational lensing. This “funhouse- mirror effect” occurs when light from a distant object is bent and stretched by the mass of an intervening object. In this case the gravitational lens, or intervening object, is a red elliptical galaxy nearly 6 billion light-years from Earth. The red color suggests that the galaxy contains older, cooler stars.

The distant object whose image is smeared into the long blue arc is about 10 billion light-years away. This ancient galaxy existed just a few billion years after the Big Bang, when the universe was about a quarter of its present age. The blue color indicates that the galaxy contains hot, young stars.

Gravitational lenses can be seen throughout the sky because the cosmos is crowded with galaxies. Light from distant galaxies, therefore, cannot always travel through space without another galaxy getting in the way. It is like walking through a crowded airport. In space, a faraway galaxy’s light will travel through a galaxy that is in the way. But if the galaxy is massive enough, its gravity will bend and distort the light.

Long arcs, such as the one in this image, are commonly seen in large clusters of galaxies because of their huge concentrations of mass. But they are not as common in isolated galaxies such as this one. For the gravitational lens to occur, the galaxies must be almost perfectly aligned with each other.

Gravitational lenses yield important information about galaxies. They are a unique and extremely useful way of directly determining the amount of mass, including dark matter, in a galaxy. Galaxies are not just made up of stars, gas, and dust. An invisible form of matter, called dark matter, makes up most of a galaxy’s mass. A study of this newly discovered system, dubbed J033238-275653, was published in the Astrophysical Journal Letters. This study, together with similar observations, may allow astronomers to make the first direct measurements of the masses of bright, nearby galaxies.

Original Source: Hubble News Release

Image credit: Hubble
Three huge intersecting dark lanes of interstellar dust make the Trifid Nebula one of the most recognizable and striking star birth regions in the night sky. The dust, silhouetted against glowing gas and illuminated by starlight, cradles the bright stars at the heart of the Trifid Nebula. This nebula, also known as Messier 20 and NGC 6514, lies within our own Milky Way Galaxy about 9,000 light-years (2,700 parsecs) from Earth, in the constellation Sagittarius.

This new image from the Hubble Space Telescope offers a close-up view of the center of the Trifid Nebula, near the intersection of the dust bands, where a group of recently formed, massive, bright stars is easily visible. These stars, which astronomers classify as belonging to the hottest and bluest types of stars called type “O,” are releasing a flood of ultraviolet radiation that dramatically influences the structure and evolution of the surrounding nebula. Many astronomers studying nebulae like the Trifid are focusing their research on the ways that waves of star formation move through such regions.

The group of bright O-type stars at the center of the Trifid illuminates a dense pillar of gas and dust, seen to the right of the center of the image, producing a bright rim on the side facing the stars. At the upper left tip of this pillar, there is a complex filamentary structure. This wispy structure has a bluish color because it is made up of glowing oxygen gas that is evaporating into space.

Star formation is no longer occurring in the immediate vicinity of the conspicuous group of bright O-type stars, because their intense radiation has blown away the gas and dust from which stars are made. However, not far away there are signs of interstellar material collapsing under its own gravity, leading to ongoing star formation. One such example is a very young star that is still surrounded by a ring of gas and dust left over from the star’s formation. These circumstellar rings, called protoplanetary disks, or “proplyds” for short, are believed to be the locations where planetary systems are formed. A proplyd in the Trifid Nebula is visible near the lower right of the main Hubble image. An image enlargement of the proplyd is shown in the lower left box, where its elongated shape can be seen.

In the box at upper right, a jet of material is seen being ejected from a very young, low-mass star. The jet, extending to the lower right of the box, protrudes from the head of a dense pillar and extends three-quarters of a light-year out into the surrounding thin gas. The jet’s source is a very young stellar object that lies buried within the pillar. Previous Hubble images of the Trifid Nebula, taken in 1997, show very small, but noticeable changes in the knotty material being ejected from this jet. Accompanying the jet is a nearby stalk that points directly toward the central stars in the Trifid Nebula. This finger-like stalk is similar to the large pillars of gas in the well-known Eagle Nebula, also imaged by Hubble.

The Hubble image of the Trifid Nebula has given astronomers insight into the nature of the interaction of gaseous, dusty and stellar material in an area where dust, gas clouds, and new and old stars coexist. The science team, composed of Farhad Yusef-Zadeh (Northwestern U.), John Biretta (STScI), Bob O’Dell (Vanderbilt U.), and Mark Wardle (Macquarie U.), took exposures in filters that transmit light emitted by oxygen, hydrogen, and sulfur ions. The images were taken with the Wide Field Planetary Camera 2 onboard Hubble in mid-summer 2001 and 2002. This image was produced by the Hubble Heritage Team.

Original Source: Hubble News Release

Image credit: University of Maryland
NASA Administrator Sean O’Keefe today announced the agency’s decision to pursue the feasibility of a robotic servicing mission to the Hubble Space Telescope (HST). NASA initiated the first step toward enabling such a mission with the release of a Request for Proposals today. The due date for proposal submissions is July 16, 2004.

“This is the first step in a long process of developing the best options to save Hubble,” Administrator O’Keefe said. “We are on a tight schedule to assure a Hubble servicing mission toward the end of calendar year 2007. But we must act promptly to fully explore this approach.”

Although the primary goal of a robotic mission is to install a deorbit module on the HST, NASA is studying the feasibility of performing other tasks. The tasks could include installing new batteries, gyros and possibly science instruments that would enhance the observatory’s ability to peer even more deeply into the universe. The final decision about specific robotic tasks will be made after all proposals have been thoroughly reviewed.

Original Source: NASA News Release

Image credit: Hubble
Astronomers poring over 35 NASA Hubble Space Telescope images of the solar system’s farthest known object, unofficially named Sedna, are surprised that the object does not appear to have a companion moon of any substantial size.

This unexpected result might offer new clues to the origin and evolution of objects on the far edge of the solar system.

When Sedna’s existence was announced on March 15, its discoverer, Mike Brown of Caltech, was so convinced it had a satellite that an artist’s concept of Sedna released to the media included a hypothetical moon.

Brown’s prediction was based on the fact that Sedna appears to have a very slow rotation that could best be explained by the gravitational tug of a companion object. Almost all other solitary bodies in the solar system complete a spin in a matter of hours.

“I’m completely baffled at the absence of a moon,” says Brown. “This is outside the realm of expectation and makes Sedna even more interesting. But I simply don’t know what it means.”

Immediately following the announcement of the discovery of Sedna, astronomers turned the Hubble Space Telescope toward the new planetoid to search for the expected companion moon. The space-based platform provides the resolving power needed to make such precision measurements in visible light. “Sedna’s image isn’t stable enough in ground-based telescopes,” says Brown.

Surprisingly, the Hubble images taken March 16 with the new Advanced Camera for Surveys only show the single object Sedna, along with a faint, very distant background star in the same field of view.

“Despite HST’s crisp view (equivalent to trying to see a soccer ball 900 miles away), it still cannot resolve the disk of mysterious Sedna,” says Brown. This would place an upper limit in the object’s size of being approximately three-quarters the diameter of Pluto, or about 1,000 miles across.

But Brown predicted that a satellite would pop up as a companion “dot” in Hubble’s precise view. The object is not there, though there is a very small chance it might have been behind Sedna or transiting in front of it, so that it could not be seen separately from Sedna itself in the Hubble images.

Brown based this prediction on his earlier observations of apparent periodic changes in light reflecting from Sedna’s mottled surface. The resulting light curve gives a long rotation period exceeding 20 days (but not greater than 50 days). If true, Sedna would be the slowest rotating object in the solar system after Mercury and Venus, whose slow rotation rates are due to the tidal influence of the Sun.

One easy way out of this dilemma is the possibility that the rotation period is not as slow as the astronomers thought. But even with a careful reanalysis the team remains convinced that the period is correct. Brown admits, “I’m completely lost for an explanation as to why the object rotates so slowly.”

Small bodies like asteroids and comets typically complete one rotation in a matter of hours. Pluto’s rotation has been slowed to a relatively leisurely six-day period because Pluto is tidally locked to the revolution period of its satellite Charon. Hubble easily resolves Pluto and Charon as two separate bodies. NASA’s forthcoming James Webb Space Telescope will provide a platform for further high-resolution studies of the infrared light from such distant, cold bodies in our solar system.

The Space Telescope Science Institute (STScI) is operated by the Association of Universities for Research in Astronomy, Inc. (AURA), for NASA, under contract with the Goddard Space Flight Center, Greenbelt, MD. The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency (ESA).

Original Source: Hubble News Release

Image credit: Hubble
What appear as individual grains of sand on a beach in this image obtained with NASA’s Hubble Space Telescope are actually myriads of stars embedded deep in the heart of the nearby galaxy NGC 300. The Hubble telescope’s exquisite resolution enables it to see the stars as individual points of light, despite the fact that the galaxy is millions of light-years away.

NGC 300 is a spiral galaxy similar to our own Milky Way. It is a member of a nearby collection of galaxies known as the Sculptor group, named for the southern constellation where the group can be found. The distance to NGC 300 is 6.5 million light-years, making it one of the Milky Way’s closer neighbors. At this distance, only the brightest stars can be picked out from ground-based images. With a resolution some 10 times better than ground-based telescopes, Hubble’s Advanced Camera for Surveys (ACS) resolves many more stars in this galaxy than can be detected from the ground.

A ground-based Digitized Sky Survey image of the full field of NGC 300 is shown in the top left frame. An outline of the Hubble Heritage ACS image is marked and shown in the image in the top right frame. A detailed blowup of this image (in the bottom frame) shows individual stars in the galaxy. A background spiral galaxy is visible in the lower right corner. The individual Hubble ACS exposures were taken in July and September 2002.

Original Source: Hubble News Release

Image credit: Hubble
The good news from NASA’s Hubble Space Telescope is that Einstein was right ? maybe.

A strange form of energy called “dark energy” is looking a little more like the repulsive force that Einstein theorized in an attempt to balance the universe against its own gravity. Even if Einstein turns out to be wrong, the universe’s dark energy probably won’t destroy the universe any sooner than about 30 billion years from now, say Hubble researchers.

“Right now we’re about twice as confident than before that Einstein’s cosmological constant is real, or at least dark energy does not appear to be changing fast enough (if at all) to cause an end to the universe anytime soon,” says Adam Riess of the Space Telescope Science Institute, Baltimore.

Riess used Hubble to find nature’s own “weapons of mass destruction” ? very distant supernovae that exploded when the universe was less than half its current age. The apparent brightness of a certain type of supernova gives cosmologists a way to measure the expansion rate of the universe at different times in the past.

Riess and his team joined efforts with the Great Observatories Origins Deep Survey (GOODS) program, the largest deep galaxy survey attempted by Hubble to date, to turn the Space Telescope into a supernova search engine on an unprecedented scale. In the process, they discovered 42 new supernovae in the GOODS area, including 6 of the 7 most distant known.

Cosmologists understand almost nothing about dark energy even though it appears to comprise about 70 percent of the universe. They are desperately seeking to uncover its two most fundamental properties: its strength and its permanence.

In a paper to be published in the Astrophysical Journal, Riess and his collaborators have made the first meaningful measurement of the second property, its permanence.

Currently, there are two leading interpretations for the dark energy as well as many more exotic possibilities. It could be an energy percolating from empty space as Einstein’s theorized “cosmological constant,” an interpretation which predicts that dark energy is unchanging and of a prescribed strength.

An alternative possibility is that dark energy is associated with a changing energy field dubbed “quintessence.”

This field would be causing the current acceleration ? a milder version of the inflationary episode from which the early universe emerged.

When astronomers first realized the universe was accelerating, the conventional wisdom was that it would expand forever. However, until we better understand the nature of dark energy?its properties?other scenarios for the fate of the universe are possible.

If the repulsion from dark energy is or becomes stronger than Einstein’s prediction, the universe may be torn apart by a future “Big Rip,” during which the universe expands so violently that first the galaxies, then the stars, then planets, and finally atoms come unglued in a catastrophic end of time. Currently this idea is very speculative, but being pursued by theorists.

At the other extreme, a variable dark energy might fade away and then flip in force such that it pulls the universe together rather then pushing it apart.

This would lead to a “big crunch” where the universe ultimately implodes. “This looks like the least likely scenario at present,” says Riess.

Understanding dark energy and determining the universe’s ultimate fate will require further observations. Hubble and future space telescopes capable of looking more than halfway across the universe will be needed to achieve the necessary precision. The determination of the properties of dark energy has become the key goal of astronomy and physics today.

Original Source: Hubble News Release

Image credit: Hubble
Seventeen years ago, astronomers spotted the brightest stellar explosion ever seen since the one observed by Johannes Kepler 400 years ago. Called SN 1987A, the titanic supernova explosion blazed with the power of 100,000,000 suns for several months following its discovery on Feb. 23, 1987. Although the supernova itself is now a million times fainter than 17 years ago, a new light show in the space surrounding it is just beginning.

This image, taken Nov. 28, 2003 by the Advanced Camera for Surveys aboard NASA’s Hubble Space Telescope, shows many bright spots along a ring of gas, like pearls on a necklace. These cosmic “pearls” are being produced as a supersonic shock wave unleashed during the explosion slams into the ring at more than a million miles per hour. The collision is heating the gas ring, causing its innermost regions to glow.

Astronomers detected the first “hot spot” in 1996, but now they see dozens of them all around the ring. The temperature of the flares surges from a few thousand degrees to a million degrees Fahrenheit. Individual hot spots cannot be seen from ground-based telescopes. Only Hubble can resolve them.

And, more hot spots are coming. In the next few years, the entire ring will be ablaze as it absorbs the full force of the crash. The glowing ring is expected to become bright enough to illuminate the star’s surroundings, thus providing astronomers with new information on how the star ejected material before the explosion.

The elongated and expanding object in the middle of the ring is debris from the supernova blast. The glowing debris is being heated by radioactive elements, principally titanium 44, that were created in the supernova explosion. The debris will continue to glow for many decades.

The ring, about a light-year across, already existed when the star exploded. Astronomers believe the star shed the ring about 20,000 years before the supernova blast.

The violent death of a star 20 times more massive than the Sun, called a supernova, created this stellar drama. The star actually exploded about 160,000 years ago, but it has taken that long for its light to reach Earth. The supernova resides in the Large Magellanic Cloud, a nearby small galaxy that is a satellite or our Milky Way galaxy.

Since its launch in 1990, the Hubble telescope has watched the supernova drama unfold, taking periodic snapshots of the gradually fading ring. Now, the orbiting observatory will continue to monitor the ring as it brightens from this collision.

Original Source: Hubble Space Telescope

Image credit: Hubble
The nearby dwarf galaxy NGC 1569 is a hotbed of vigorous star birth activity which blows huge bubbles that riddle the main body of the galaxy. The galaxy’s “star factories” are also manufacturing brilliant blue star clusters. This galaxy had a sudden onset of star birth about 25 million years ago, which subsided about the time the very earliest human ancestors appeared on Earth.

In this new image, taken with NASA’s Hubble Space Telescope, the bubble structure is sculpted by the galactic super-winds and outflows caused by a colossal input of energy from collective supernova explosions that are linked with a massive episode of star birth.

One of the still unresolved mysteries in astronomy is how and when galaxies formed and how they evolved. Most of today’s galaxies seem to have been already fully formed very early on in the history of the universe (now corresponding to a large distance away from us), their formation involving one or more galaxy collisions and/or episodes of strongly enhanced star formation activity (so-called starbursts).

While any galaxies that are actually forming are too far away for detailed studies of their stellar populations even with Hubble, their local counterparts, nearby starburst and colliding galaxies, are far easier targets.

NGC 1569 is a particularly suitable example, being one of the closest starburst galaxies. It harbors two very prominent young, massive clusters plus a large number of smaller star clusters. The two young massive clusters match the globular star clusters we find in our own Milky Way galaxy, while the smaller ones are comparable with the less massive open clusters around us.

NGC 1569 was recently investigated in great detail by a group of European astronomers who published their results in the January 1, 2004 issue of the British journal, Monthly Notices of the Royal Astronomical Society. The group used several of Hubble’s high-resolution instruments, with deep observations spanning a wide wavelength range, to determine the parameters of the clusters more precisely than is currently possible from the ground.

The team found that the majority of clusters in NGC 1569 seem to have been produced in an energetic starburst that started around 25 million years ago and lasted for about 20 million years. First author Peter Anders from the Gottingen University Galaxy Evolution Group, Germany says “We are looking straight into the very creation processes of the stars and star clusters in this galaxy. The clusters themselves present us with a fossil record of NGC 1569’s intense star formation history.”

The bubble-like structures seen in this image are made of hydrogen gas that glows when hit by the fierce winds and radiation from hot young stars and is racked by supernovae shocks. The first supernovae blew up when the most massive stars reached the end of their lifetimes roughly 20-25 million years ago. The environment in NGC 1569 is still turbulent and the supernovae may not only deliver the gaseous raw material needed for the formation of further stars and star clusters, but also actually trigger their birth in the tortured swirls of gas.

The color image is composed of 4 different exposures with Hubble’s Wide Field and Planetary Camera 2 through the following filters: a wide ultraviolet filter (shown in blue), a green filter (shown in green), a wide red filter (shown in red), and a Hydrogen alpha filter (also shown in red).

Original Source: Hubble News Release

Image credit: ESA
The well-known extrasolar planet HD 209458b, provisionally nicknamed Osiris, has surprised astronomers again. Oxygen and carbon have been found in its atmosphere, evaporating at such an immense rate that the existence of a new class of extrasolar planets ? ?the chthonian planets? or ?dead? cores of completely evaporated gas giants – has been proposed.

Oxygen and carbon have been detected in the atmosphere of a planet beyond our Solar System for the first time. Scientists using the NASA/ESA Hubble Space Telescope have observed the famous extrasolar planet HD 209458b passing in front of its parent star, and found oxygen and carbon surrounding the planet in an extended ellipsoidal envelope – the shape of a rugby-ball. These atoms are swept up from the lower atmosphere with the flow of the escaping atmospheric atomic hydrogen, like dust in a supersonic whirlwind.

The team led by Alfred Vidal-Madjar (Institut d?Astrophysique de Paris, CNRS, France) reports this discovery in a forthcoming issue of Astrophysical Journal Letters.

The planet, called HD 209458b, may sound familiar. It is already an extrasolar planet with an astounding list of firsts: the first extrasolar planet discovered transiting its sun, the first with an atmosphere, the first observed to have an evaporating hydrogen atmosphere (in 2003 by the same team of scientists) and now the first to have an atmosphere containing oxygen and carbon. Furthermore the ?blow-off? effect observed by the team during their October and November 2003 observations with Hubble had never been seen before.

In honour of such a distinguished catalogue this extraordinary extrasolar planet has provisionally been dubbed ?Osiris?. Osiris is the Egyptian god who lost part of his body ? like HD 209458b – after his brother killed and cut him into pieces to prevent his return to life.

Oxygen is one of the possible indicators of life that is often looked for in experiments searching for extraterrestrial life (such as those onboard the Viking probes and the Spirit and Opportunity rovers), but according to Vidal-Madjar: ?Naturally this sounds exciting – the possibility of life on Osiris – but it is not a big surprise as oxygen is also present in the giant planets of our Solar System, like Jupiter and Saturn?.

What, on the other hand was surprising was to find the carbon and oxygen atoms surrounding the planet in an extended envelope. Although carbon and oxygen have been observed on Jupiter and Saturn, it is always in combined form as methane and water deep in the atmosphere. In HD 209458b the chemicals are broken down into the basic elements. But on Jupiter or Saturn, even as elements, they would still remain invisible low in the atmosphere. The fact that they are visible in the upper atmosphere of HD 209458b confirms that atmospheric ?blow off? is occurring.

The scorched Osiris orbits ?only? 7 million kilometres from its yellow Sun-like star and its surface is heated to about 1,000 degrees Celsius.

Whereas hydrogen is a very light element – the lightest in fact – oxygen and carbon are much heavier in comparison. This has enabled scientists to conclude that this phenomenon is more efficient than simple evaporation. The gas is essentially ripped away at a speed of more than 35,000 km/hour. ?We speculate that even heavier elements such as iron are blown off at this stage as well? says team member Alain Lecavelier des Etangs (Institut d’Astrophysique de Paris, CNRS, France).

The whole evaporation mechanism is so distinctive that there is reason to propose the existence of a new class of extrasolar planets – the chthonian planets, a reference to the Greek God Kht?n, used for Greek deities from the hot infernal underworld (also used in the French word autochton). The chthonian planets are thought to be the solid remnant cores of ?evaporated gas giants?, orbiting even closer to their parent star than Osiris. The detection of these planets should soon be within reach of current telescopes both on the ground and in space.

The discovery of the fierce evaporation process is, according to the scientists, ?highly unusual?, but may indirectly confirm theories of our own Earth?s childhood. ?This is a unique case in which such a hydrodynamic escape is directly observed. It has been speculated that Venus, Earth and Mars may have lost their entire original atmospheres during the early part of their lives. Their present atmospheres have their origins in asteroid and cometary impacts and outgassing from the planet interiors?, says Vidal-Madjar.

Original Source: ESA News Release