Hubble, Swift Detect First-Ever Changes in an Exoplanet Atmosphere

Exoplanet HD 189733b (Artist's Illustration)

Illustration Credit: NASA Goddard Space Flight Center

Science Credit:NASA,ESA, A. Lecavelier des Etangs (CNRS-UMPC, France), and P. Wheatley (University of Warwick)

WASHINGTON — An international team of astronomers using data from NASA's Hubble Space Telescope has made an unparalleled observation, detecting significant changes in the atmosphere of a planet located beyond our solar system.

The scientists conclude the atmospheric variations occurred in response to a powerful eruption on the planet's host star, an event observed by NASA's Swift satellite.

"The multiwavelength coverage by Hubble and Swift has given us an unprecedented view of the interaction between a flare on an active star and the atmosphere of a giant planet," said lead researcher Alain Lecavelier des Etangs at the Paris Institute of Astrophysics (IAP), part of the French National Scientific Research Center located at Pierre and Marie Curie University in Paris.

The exoplanet is HD 189733b, a gas giant similar to Jupiter, but about 14 percent larger and more massive. The planet circles its star at a distance of only 3 million miles, or about 30 times closer than Earth's distance from the Sun, and completes an orbit every 2.2 days. Its star, named HD 189733A, is about 80 percent the size and mass of our Sun.

Astronomers classify the planet as a "hot Jupiter." Previous Hubble observations show that the planet's deep atmosphere reaches a temperature of about 1,900 degrees Fahrenheit (1,030 degrees Celsius).

HD 189733b periodically passes across, or transits, its parent star, and these events give astronomers an opportunity to probe its atmosphere and environment. In a previous study, a group led by Lecavelier des Etangs used Hubble to show that hydrogen gas was escaping from the planet's upper atmosphere. The finding made HD 189733b only the second known "evaporating" exoplanet at the time.

The system is just 63 light-years away, so close that its star can be seen with binoculars near the famous Dumbbell Nebula. This makes HD 189733b an ideal target for studying the processes that drive atmospheric escape.

"Astronomers have been debating the details of atmospheric evaporation for years, and studying HD 189733b is our best opportunity for understanding the process," said Vincent Bourrier, a doctoral student at IAP and a team member on the new study.

When HD 189733b transits its star, some of the star's light passes through the planet's atmosphere. This interaction imprints information on the composition and motion of the planet's atmosphere into the star's light.

In April 2010, the researchers observed a single transit using Hubble's Space Telescope Imaging Spectrograph (STIS), but they detected no trace of the planet's atmosphere. Follow-up STIS observations in September 2011 showed a surprising reversal, with striking evidence that a plume of gas was streaming away from the exoplanet.

The researchers determined that at least 1,000 tons of gas was leaving the planet's atmosphere every second. The hydrogen atoms were racing away at speeds greater than 300,000 miles per hour. The findings will appear in an upcoming issue of the journal Astronomy & Astrophysics.

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.

Hubble is a project of international cooperation between NASA and the European Space Agency. Swift is operated in collaboration with several U.S. institutions and partners in the United Kingdom, Italy, Germany, and Japan. NASA's Goddard Space Flight Center in Greenbelt, Md., manages both missions.

For images and video related to this finding, visit: http://go.nasa.gov/Osbvfi

For more information about Swift, visit: http://www.nasa.gov/swift

For more information about Hubble, visit: http://www.nasa.gov/hubble

CONTACT

J. D. Harrington
Headquarters, Washington
202-358-5241
j.d.harrington@nasa.gov

Lynn Chandler
NASA Goddard Space Flight Center, Greenbelt, Md.
301-286-2806
lynn.chandler-1@nasa.gov

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Dark Matter Core Defies Explanation in Hubble Image

Merging Galaxy Cluster Abell 520
Credit: NASA, ESA, CFHT, CXO, M.J. Jee (University of California, Davis),
and A. Mahdavi (San Francisco State University)
News Realease Images - Zoomable image

It was the result no one wanted to believe. Astronomers observed what appeared to be a clump of dark matter left behind during a bizarre wreck between massive clusters of galaxies.

The dark matter collected into a "dark core" containing far fewer galaxies than would be expected if the dark matter and galaxies hung together. Most of the galaxies apparently have sailed far away from the collision. This result could present a challenge to basic theories of dark matter, which predict that galaxies should be anchored to the invisible substance, even during the shock of a collision.

The initial observations, made in 2007, were so unusual that astronomers shrugged them off as unreal, due to poor data. However, new results from NASA's Hubble Space Telescope confirm that dark matter and galaxies parted ways in the gigantic merging galaxy cluster called Abell 520, located 2.4 billion light-years away.

Now, astronomers are left with the challenge of trying to explain dark matter's seemingly oddball behavior in this cluster.

"This result is a puzzle," said astronomer James Jee of the University of California, Davis, leader of the Hubble study. "Dark matter is not behaving as predicted, and it's not obviously clear what is going on. Theories of galaxy formation and dark matter must explain what we are seeing."

A paper reporting the team's results has been accepted for publication in The Astrophysical Journal and is available online.

First detected about 80 years ago, dark matter is thought to be the gravitational "glue" that holds galaxies together. The mysterious invisible substance is not made of the same kind of matter that makes up stars, planets, and people. Astronomers know little about dark matter, yet it accounts for most of the universe's mass.

They have deduced dark matter's existence by observing its ghostly gravitational influence on normal matter. It's like hearing the music but not seeing the band.

One way to study dark matter is by analyzing smashups between galaxy clusters, the largest structures in the universe. When galaxy clusters collide, astronomers expect galaxies to tag along with the dark matter, like a dog on a leash. Clouds of intergalactic gas, however, plow into one another, slow down, and lag behind the impact.

That theory was supported by visible-light and X-ray observations of a colossal collision between two galaxy clusters called the Bullet Cluster. The galactic grouping has become a textbook example of how dark matter should behave.

But studies of Abell 520 showed that dark matter's behavior may not be so simple. The original observations found that the system's core was rich in dark matter and hot gas but contained no luminous galaxies, which normally would be seen in the same location as the dark matter. NASA's Chandra X-ray Observatory detected the hot gas. Astronomers used the Canada-France-Hawaii and Subaru telescopes atop Mauna Kea to infer the location of dark matter by measuring how the mysterious substance bends light from more distant background galaxies, an effect called gravitational lensing.

The astronomers then turned Hubble's Wide Field Planetary Camera 2 to help bail them out of this cosmic conundrum. Instead, to their chagrin, the Hubble observations helped confirm the earlier findings. Astronomers used Hubble to map the dark matter in the cluster through the gravitational lensing technique.

"Observations like those of Abell 520 are humbling in the sense that in spite of all the leaps and bounds in our understanding, every now and then, we are stopped cold," explained Arif Babul of the University of Victoria in British Columbia, the team's senior theorist.

Is Abell 520 an oddball, or is the prevailing picture of dark matter flawed? Jee thinks it's too soon to tell.

"We know of maybe six examples of high-speed galaxy cluster collisions where the dark matter has been mapped," Jee said. "But the Bullet Cluster and Abell 520 are the two that show the clearest evidence of recent mergers, and they are inconsistent with each other. No single theory explains the different behavior of dark matter in those two collisions. We need more examples."

The team has proposed a half-dozen explanations for the findings, but each is unsettling for astronomers. "It's pick your poison," said team member Andisheh Mahdavi of San Francisco State University in California, who led the original Abell 520 observations in 2007. One possible explanation for the discrepancy is that Abell 520 was a more complicated interaction than the Bullet Cluster encounter. Abell 520 may have formed from a collision between three galaxy clusters, instead of just two colliding systems in the case of the Bullet Cluster.

Another scenario is that some dark matter may be what astronomers call "sticky." Like two snowballs smashing together, normal matter slams into each other during a collision and slows down. But dark matter blobs are thought to pass through each other during an encounter without slowing down. This scenario proposes that some dark matter interacts with itself and stays behind when galaxy clusters collide.

A third possibility is that the core contained many galaxies, but they were too dim to be seen, even by Hubble. Those galaxies would have to have formed dramatically fewer stars than other normal galaxies. Armed with the Hubble data, the group hopes to create a computer simulation to try to reconstruct the collision, hoping that it yields some answers to dark matter's weird behavior.

CONTACT

Ray Villard
Space Telescope Science Institute, Baltimore, Md.
410-338-4514
villard@stsci.edu

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IBEX: Glimpses of the Interstellar Material Beyond our Solar System

IBEX has directly sampled multiple heavy elements from the Local Interstellar Cloud for the first time. Credit: NASA/Goddard Scientific Visualization Studio. Download video

A great magnetic bubble surrounds the solar system as it cruises through the galaxy. The sun pumps the inside of the bubble full of solar particles that stream out to the edge until they collide with the material that fills the rest of the galaxy, at a complex boundary called the heliosheath. On the other side of the boundary, electrically charged particles from the galactic wind blow by, but rebound off the heliosheath, never to enter the solar system. Neutral particles, on the other hand, are a different story. They saunter across the boundary as if it weren't there, continuing on another 7.5 billion miles for 30 years until they get caught by the sun's gravity, and sling shot around the star.

There, NASA's Interstellar Boundary Explorer lies in wait for them. Known as IBEX for short, this spacecraft methodically measures these samples of the mysterious neighborhood beyond our home. IBEX scans the entire sky once a year, and every February, its instruments point in the correct direction to intercept incoming neutral atoms. IBEX counted those atoms in 2009 and 2010 and has now captured the best and most complete glimpse of the material that lies so far outside our own system.

The results? It's an alien environment out there: the material in that galactic wind doesn't look like the same stuff our solar system is made of.

Neutral atoms from the galactic wind sweep past the solar system's magnetic boundary, the heliosheath, and travel some 30 years into our solar system toward the sun. NASA's Interstellar Boundary Explorer (IBEX) can observe those atoms and provide information about the mysterious neighborhood outside our home. Credit: NASA/Goddard Conceptual Image Lab. Download video

"We've directly measured four separate types of atoms from interstellar space and the composition just doesn't match up with what we see in the solar system," says Eric Christian, mission scientist for IBEX at NASA's Goddard Space Flight Center in Greenbelt, Md. "IBEX's observations shed a whole new light on the mysterious zone where the solar system ends and interstellar space begins."

More than just helping to determine the distribution of elements in the galactic wind, these new measurements give clues about how and where our solar system formed, the forces that physically shape our solar system, and even the history of other stars in the Milky Way.

NASA's Interstellar Boundary Explorer (IBEX) has found that there's more oxygen in our solar system than there is in the nearby interstellar material. That suggests that either the sun formed in a different part of the galaxy or that outside our solar system life-giving oxygen lies trapped in dust or ice grains unable to move freely in space. Credit: NASA/Goddard. View larger

In a series of science papers appearing in the Astrophysics Journal on January 31, 2012, scientists report that for every 20 neon atoms in the galactic wind, there are 74 oxygen atoms. In our own solar system, however, for every 20 neon atoms there are 111 oxygen atoms. That translates to more oxygen in any given slice of the solar system than in the local interstellar space.

"Our solar system is different than the space right outside it and that suggests two possibilities," says David McComas the principal investigator for IBEX at the Southwest Research Institute in San Antonio, Texas. "Either the solar system evolved in a separate, more oxygen-rich part of the galaxy than where we currently reside or a great deal of critical, life-giving oxygen lies trapped in interstellar dust grains or ices, unable to move freely throughout space." Either way, this affects scientific models of how our solar system – and life – formed.

Studying the galactic wind also provides scientists with information about how our solar system interacts with the rest of space, which is congruent with an important IBEX goal. Classified as a NASA Explorer Mission -- a class of smaller, less expensive spacecraft with highly focused research objectives -- IBEX's main job is to study the heliosheath, that outer boundary of the solar system's magnetic bubble -- or heliosphere -- where particles from the solar wind meet the galactic wind.

Previous spacecraft have already provided some information about the way the galactic wind interacts with the heliosheath. Ulysses, for one, observed incoming helium as it traveled past Jupiter and measured it traveling at 59,000 miles per hour. IBEX's new information, however, shows the galactic wind traveling not only at a slower speed -- around 52,000 miles per hour -- but from a different direction, most likely offset by some four degrees from previous measurements. Such a difference may not initially seem significant, but it amounts to a full 20% difference in how much pressure the galactic wind exerts on the heliosphere.

The galactic wind streams toward the sun from the direction of Scorpio and IBEX has found that it travels at 52,000 miles an hour. The speed of the galactic wind and its subsequent pressure on the outside of the solar system's boundary affects the shape of the heliosphere as it travels through space. Credit: NASA/Goddard Scientific Visualization Studio. View larger

"Measuring the pressure on our heliosphere from the material in the galaxy and from the magnetic fields out there," says Christian, "will help determine the size and shape of our solar system as it travels through the galaxy."

These IBEX measurements also provide information about the cloud of material in which the solar system currently resides. This cloud is called the local interstellar cloud, to differentiate it from the myriad of particle clouds throughout the Milky Way, each traveling at different speeds. The solar system and its heliosphere moved into our local cloud at some point during the last 45,000 years.

Since the older Ulysses observations of the galactic wind speed was in between the speeds expected for the local cloud and the adjacent cloud, researchers thought perhaps the solar system didn't lie smack in the middle of this cloud, but might be at the boundary, transitioning into a new region of space. IBEX's results, however, show that we remain fully in the local cloud, at least for the moment.

"Sometime in the next hundred to few thousand years, the blink of an eye on the timescales of the galaxy, our heliosphere should leave the local interstellar cloud and encounter a much different galactic environment," McComas says.

In addition to providing insight into the interaction between the solar system and its environment, these new results also hold clues about the history of material in the universe. While the big bang initially created hydrogen and helium, only the supernovae explosions at the end of a giant star's life can spread the heavier elements of oxygen and neon through the galaxy. Knowing the amounts of such elements in space can help map how the galaxy has evolved and changed over time.

NASA's Interstellar Boundary Explorer (IBEX) studies the outer boundaries of the solar system where particles from the solar wind collide with particles from the galactic wind. Credit: NASA. View larger

"This set of papers provide many of the first direct measurements of the interstellar medium around us," says McComas. "We've been trying to understand our galaxy for a long time, and with all of these observations together, we are taking a major step forward in knowing what the local part of the galaxy is like."

Voyager 1 could cross out of our solar system within the next few years. By combining the data from several sets of NASA instruments – Ulysses, Voyager, IBEX and others – we are on the precipice of stepping outside and understanding the complex environment beyond our own frontier for the first time.

The Southwest Research Institute developed and leads the IBEX mission with a team of national and international partners. The spacecraft is one of NASA's series of low-cost, rapidly developed missions in the Small Explorers Program. NASA's Goddard Space Flight Center in Greenbelt, Md., manages the program for the agency's Science Mission Directorate.

For more information about the IBEX mission, go to:

http://www.nasa.gov/ibex - Additional downloadable media

Karen C. Fox
NASA's Goddard Space Flight Center, Greenbelt, MD

More about → IBEX: Glimpses of the Interstellar Material Beyond our Solar System

Space Telescopes Reveal Secrets of Turbulent Black Hole

Image Credit: NASA, ESA, G. Kriss (STScI), and
J. de Plaa (SRON Netherlands Institute for Space Research)

Acknowledgment: B. Peterson (Ohio State University)

Science Credit: NASA, ESA, J. Kaastra (SRON Netherlands Institute for Space Research),

and G. Kriss (STScI)

An international team of astronomers using five different telescopes has uncovered striking features around a supermassive black hole in the core of the distant galaxy Markarian 509. They found a very hot corona hovering above the black hole and cold gas "bullets" in hotter diffuse gas, speeding outward with velocities over 1 million miles per hour. This corona absorbs and reprocesses the ultraviolet light from the accretion disk encircling the black hole, energizing it and converting it into X-rays. This discovery allows astronomers to make sense of some of the observations of active galaxies that have been hard to explain so far. The heart of the campaign consisted of repeated visible, X-ray, and gamma-ray observations with ESA's XMM-Newton and INTEGRAL satellites, which monitored Markarian 509 for six weeks. This was followed by long observations with NASA's Chandra X-ray Observatory and the Hubble Space Telescope. Prior to these observations short snapshots to monitor the behavior of the source at all wavelengths were taken with NASA's Swift satellite. The combined efforts of all these instruments gave astronomers an unprecedented insight into the core of an active galaxy.

The Cosmic Origins Spectrograph aboard Hubble reveals that the coolest gas in the line of sight toward Markarian 509 has 14 different velocity components at various locations in the innermost parts of this galaxy. Hubble's data, combined with X-ray observations, show that most of the visible outflowing gas is blown off from a dusty gas disk surrounding the central region more than 15 light-years away from the black hole. This outflow consists of dense, cold blobs or gas bullets embedded in hotter diffuse gas. The international consortium responsible for this campaign consists of 26 astronomers from 21 institutes on 4 continents. The first results of this campaign will be published as a series of seven papers in the journal Astronomy and Astrophysics. More results are in preparation. For more information about this study, visit:
http://www.sron.nl/index.php?option=com_content&task=view&id=3277&Itemid=754
http://www.spacetelescope.org/announcements/ann1121/

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Sunset Glow in Orion

NGC 2023
Credit: ESA/Hubble & NASA
Click to Enlarge

The magnificent reflection nebula NGC 2023 lies nearly 1500 light-years from Earth. It is located within the constellation of Orion (The Hunter), in a prestigious area of the sky close to the well-known Flame and Horsehead Nebulae. The entire structure of NGC 2023 is vast, at four light-years across. This NASA/ESA Hubble Space Telescope picture just takes in the southern part, with the subtle shades of colour closely resembling those of a sunset on Earth.


NGC 2023 surrounds a massive young B-type star. These stars are large, bright and blue-white in colour, and have a high surface temperature, being several times hotter than the Sun. The energy emitted from NGC2023’s B-type star illuminates the nebula, resulting in its high surface brightness: good news for astronomers who wish to study it. The star itself lies outside the field of view, at the upper left, and its brilliant light is scattered by Hubble’s optical system, creating the bright flare across the left side of the picture, which is not a real feature of the nebula.

Stars are forming from the material comprising NGC 2023. This Hubble image captures the billowing waves of gas, 5000 times denser than the interstellar medium. The unusual greenish clumps are thought to be Herbig–Haro objects. These peculiar features of star-forming regions are created when gas ejected at hundreds of kilometres per second from newly formed stars impacts the surrounding material. These shockwaves cause the gas to glow and result in the strange shapes seen here. Herbig–Haro objects typically only last for a few thousand years, which is the blink of eye in astronomical terms.

This picture was created from multiple images taken with the Wide Field Camera of Hubble’s Advanced Camera for Surveys. Exposures through a blue filter (F475W) are coloured blue, exposures through a yellow filter (F625W) are coloured green and images through a near-infrared filter (F850LP) are shown as red. The total exposure times per filter are 800 s, 800 s and 1200 s, respectively, and the field of view spans 3.2 arcminutes.

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NASA's Hubble Discovers Another Moon Around Pluto

Pluto's Moon System
Credit: NASA, ESA, and M. Showalter (SETI Institute)
View this image

Hubble Space Telescope's keen vision has found yet another moon orbiting the distant, icy dwarf planet Pluto. This discovery expands the size of Pluto's known satellite system to four moons. The tiny, new satellite — temporarily designated P4 — was uncovered in a Hubble survey searching for rings around the frigid dwarf planet.

The new moon is the smallest moon yet discovered around Pluto. It has an estimated diameter of 8 to 21 miles (13 to 34 km). By comparison, Charon, Pluto's largest moon, is 648 miles (1,043 km) across, and the other moons, Nix and Hydra are in the range of 20 to 70 miles in diameter (32 to 113 km).

"I find it remarkable that Hubble's cameras enabled us to see such a tiny object so clearly from a distance of more than 3 billion miles (5 billion km)," said Mark Showalter of the SETI Institute in Mountain View, Calif., who led this observing program with Hubble.

The finding is a result of ongoing work to support NASA's New Horizons mission, scheduled to fly through the Pluto system in 2015. The mission is designed to provide new insights about worlds at the edge of our solar system. Hubble's mapping of Pluto's surface and discovery of its satellites have been invaluable to planning for New Horizons' close encounter.

"This is a fantastic discovery," said New Horizons' principal investigator Alan Stern of the Southwest Research Institute in Boulder, Colo. "Now that we know there's another moon in the Pluto system, we can plan close-up observations of it during our flyby." Space Telescope Science Institute director's discretionary time was allocated to make the Hubble observations.

The new moon is located between the orbits of Nix and Hydra, which Hubble discovered in 2005. Charon was discovered in 1978 at the U.S. Naval Observatory and first resolved using Hubble in 1990 as a separate body from Pluto.

The dwarf planet's entire moon system is believed to have formed by a collision between Pluto and another planet-sized body early in the history of the solar system. The smashup flung material into orbit around Pluto, which then coalesced into the family of satellites now seen.

Lunar rocks returned to Earth from the Apollo missions led to the theory that our Moon was the result of a similar collision between Earth and a Mars-sized body 4.4 billion years ago. Scientists believe material blasted off Pluto's moons by micrometeoroid impacts may form rings around the dwarf planet, but the Hubble photographs have not detected any so far.

"This surprising observation is a powerful reminder of Hubble's ability as a general purpose astronomical observatory to make astounding, unintended discoveries," said Jon Morse, astrophysics division director at NASA Headquarters in Washington.

P4 was first seen in a photo taken with Hubble's Wide Field Camera 3 on June 28, 2011. It was confirmed in subsequent Hubble pictures taken on July 3 and July 18. The moon was not seen in earlier Hubble images because the exposure times were shorter. There is a chance it appeared as a very faint smudge in 2006 images, but was overlooked because it was largely obscured by an imaging artifact, called a diffraction spike.

CONTACT

Ray Villard
Space Telescope Science Institute, Baltimore, Md.
villard@stsci.edu
410-338-4514

Karen Randall
SETI Institute, Mountain View, Calif.
krandall@seti.org
650-960-4537

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Edge-on Galaxy Hosts Supernova Explosion

IC 755
Credit: ESA/Hubble & NASA

The NASA/ESA Hubble Space Telescope has imaged an elongated stream of stars, gas and dust called IC 755, which is actually a spiral galaxy that we are seeing edge-on.

In 1999 a star within IC 755 was seen to explode as a supernova and named SN 1999an. The supernova was discovered by the Beijing Astronomical Observatory Supernova Survey and three years later Hubble was used to study the environment in which the explosion took place. The inclination of the galaxy made the supernova a challenging target as many other intervening objects obscured the view. Valuable data were obtained and suggest that before detonation the star may have been around 20 times more massive than our Sun, and that it was likely to have been in the region of 14 million years old.

Supernovae like SN 1999an are classified as Type IIs and they are dramatic events that mark the end of the lives of massive stars. They have an important role to play in galaxy evolution as many elements are formed during the explosion and are ejected with such force that they are distributed far and wide. Shockwaves also help to mix material within the host galaxy and may spark new rounds of star formation. Billions of stars make up galaxies like IC 755 and many will become supernovae, using their final moments to breathe new life into the rest of the Universe.

This picture was created from multiple images taken with the Wide Field Camera of Hubble’s Advanced Camera for Surveys. Exposures through a blue filter (F435W) are coloured blue, exposures through a yellow-green filter (F555W) are coloured green and images through a near-infrared filter (F814W) are shown as red. The total exposure times per filter are 430 s and the field of view is 3.3 x 1.5 arcminutes.

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Neptune Completes Its First Circuit Around The Sun Since Its Discovery

Neptune's Anniversary Portraits
Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)

Inner Moons of Neptune
Illustration Credit: NASA, ESA, and Z. Levay (STScI)
Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)

Today, Neptune has arrived at the same location in space where it was discovered nearly 165 years ago. To commemorate the event, NASA's Hubble Space Telescope has taken these "anniversary pictures" of the blue-green giant planet.

Neptune is the most distant major planet in our solar system. German astronomer Johann Galle discovered the planet on September 23, 1846. At the time, the discovery doubled the size of the known solar system. The planet is 2.8 billion miles (4.5 billion kilometers) from the Sun, 30 times farther than Earth. Under the Sun's weak pull at that distance, Neptune plods along in its huge orbit, slowly completing one revolution approximately every 165 years.

These four Hubble images of Neptune were taken with the Wide Field Camera 3 on June 25-26, during the planet's 16-hour rotation. The snapshots were taken at roughly four-hour intervals, offering a full view of the planet. The images reveal high-altitude clouds in the northern and southern hemispheres. The clouds are composed of methane ice crystals.

The giant planet experiences seasons just as Earth does, because it is tilted 29 degrees, similar to Earth's 23-degree-tilt. Instead of lasting a few months, each of Neptune's seasons continues for about 40 years.

The snapshots show that Neptune has more clouds than a few years ago, when most of the clouds were in the southern hemisphere. These Hubble views reveal that the cloud activity is shifting to the northern hemisphere. It is early summer in the southern hemisphere and winter in the northern hemisphere.

In the Hubble images, absorption of red light by methane in Neptune's atmosphere gives the planet its distinctive aqua color. The clouds are tinted pink because they are reflecting near-infrared light.

A faint, dark band near the bottom of the southern hemisphere is probably caused by a decrease in the hazes in the atmosphere that scatter blue light. The band was imaged by NASA's Voyager 2 spacecraft in 1989, and may be tied to circumpolar circulation created by high-velocity winds in that region.

The temperature difference between Neptune's strong internal heat source and its frigid cloud tops, about minus 260 degrees Fahrenheit, might trigger instabilities in the atmosphere that drive large-scale weather changes.

Neptune has an intriguing history. It was Uranus that led astronomers to Neptune. Uranus, the seventh planet from the Sun, is Neptune's inner neighbor. British astronomer Sir William Herschel and his sister Caroline found Uranus in 1781, 55 years before Neptune was spotted. Shortly after the discovery, Herschel noticed that the orbit of Uranus did not match the predictions of Newton's theory of gravity. Studying Uranus in 1821, French astronomer Alexis Bouvard speculated that another planet was tugging on the giant planet, altering its motion.

Twenty years later, Urbain Le Verrier of France and John Couch Adams of England, who were mathematicians and astronomers, independently predicted the location of the mystery planet by measuring how the gravity of a hypothetical unseen object could affect Uranus's path. Le Verrier sent a note describing his predicted location of the new planet to the German astronomer Johann Gottfried Galle at the Berlin Observatory. Over the course of two nights in 1846, Galle found and identified Neptune as a planet, less than a degree from Le Verrier's predicted position. The discovery was hailed as a major success for Newton's theory of gravity and the understanding of the universe.

Galle was not the first to see Neptune. In December 1612, while observing Jupiter and its moons with his handmade telescope, astronomer Galileo Galilei recorded Neptune in his notebook, but as a star. More than a month later, in January 1613, he noted that the "star" appeared to have moved relative to other stars. But Galileo never identified Neptune as a planet, and apparently did not follow up those observations, so he failed to be credited with the discovery.

Neptune is not visible to the naked eye, but may be seen in binoculars or a small telescope. It can be found in the constellation Aquarius, close to the boundary with Capricorn.

Neptune-mass planets orbiting other stars may be common in our Milky Way galaxy. NASA's Kepler mission, launched in 2009 to hunt for Earth-size planets, is finding increasingly smaller extrasolar planets, including many the size of Neptune.

For additional information, contact:

Donna Weaver / Ray Villard
Space Telescope Science Institute, Baltimore, Md.
410-338-4493 / 410-338-4514
dweaver@stsci.edu / villard@stsci.edu

Keith Noll
Space Telescope Science Institute, Baltimore, Md.
410-338-1828
noll@stsci.edu

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NASA's Hubble Makes One Millionth Science Observation

Transiting Exoplanet HAT-P-7b
Credit: NASA, ESA, and G. Bacon (STScI)

All-Sky illustration of all Hubble observations as of June 27, 2011

Credit: NASA, ESA, and R. Thompson (CSC/STScI)

NASA's Hubble Space Telescope crossed another milestone in its space odyssey of exploration and discovery. On Monday, July 4, the Earth-orbiting observatory logged its one millionth science observation during a search for water in an exoplanet's atmosphere 1,000 light-years away.

"For 21 years Hubble has been the premier space science observatory, astounding us with deeply beautiful imagery and enabling ground-breaking science across a wide spectrum of astronomical disciplines," said NASA Administrator Charles Bolden. He piloted the space shuttle mission that carried Hubble to orbit. "The fact that Hubble met this milestone while studying a faraway planet is a remarkable reminder of its strength and legacy."

Although Hubble is best known for its stunning imagery of the cosmos, the millionth observation is a spectrocopic measurement, where light is divided its component colors. These color patterns can reveal the chemical composition of cosmic sources.

Hubble's millionth exposure is of the planet HAT-P-7b, a gas giant planet larger than Jupiter orbiting a star hotter than our Sun. HAT-P-7b, also known as Kepler 2b, has been studied by NASA's planet-hunting Kepler observatory after it was discovered by ground-based observations. Hubble now is being used to analyze the chemical composition of the planet's atmosphere.

"We are looking for the spectral signature of water vapor. This is an extremely precise observation and it will take months of analysis before we have an answer," said Drake Deming of the University of Maryland and NASA's Goddard Space Flight Center in Greenbelt, Md. "Hubble demonstrated it is ideally suited for characterizing the atmospheres of exoplanets, and we are excited to see what this latest targeted world will reveal."

"This exciting set of observations in search of water vapor on a planet orbiting another star is laying the foundation for how we plan to use the James Webb Space Telescope's more powerful vision to look for liquid water on nearby planets, the necessary precursor to extraterrestrial life," said Matt Mountain, STScI director.

Hubble was launched April 24, 1990, aboard space shuttle Discovery's STS-31 mission. Its discoveries revolutionized nearly all areas of astronomical research from planetary science to cosmology. The observatory has collected more than 50 terabytes of data to-date. The archive of that data is available to scientists and the public at: http://hla.stsci.edu/

Hubble's odometer reading includes every observation of astronomical targets since its launch and observations used to calibrate its suite of instruments. Hubble made the millionth observation using its Wide Field Camera 3, a visible- and infrared-light imager with an on-board spectrometer. It was installed by astronauts during Hubble Servicing Mission 4 in May 2009.

"The Hubble keeps amazing us with groundbreaking science," said Sen. Barbara Mikulski, the chairwoman of the Senate Commerce, Justice, Science and Related Agencies Appropriations Subcommittee that funds NASA. "I championed the mission to repair and renew Hubble not just to get one million science observations, but also to inspire millions of children across the planet to become our next generation of stargazers, scientists, astronauts and engineers."

CONTACT

Trent Perrotto
NASA Headquarters, Washington, D.C.
trent.j.perrotto@nasa.gov
202-358-0321

Ray Villard
Space Telescope Science Institute, Baltimore, Md.
410-338-4514
villard@stsci.edu

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