vendredi 30 septembre 2011

NASA Space Telescope Finds Fewer Asteroids Near Earth

NASA - WISE Mission patch.

Sept. 30, 2011

New observations by NASA's Wide-field Infrared Survey Explorer, or WISE, show there are significantly fewer near-Earth asteroids in the mid-size range than previously thought. The findings also indicate NASA has found more than 90 percent of the largest near-Earth asteroids, meeting a goal agreed to with Congress in 1998.

Astronomers now estimate there are roughly 19,500 -- not 35,000 -- mid-size near-Earth asteroids. Scientists say this improved understanding of the population may indicate the hazard to Earth could be somewhat less than previously thought. However, the majority of these mid-size asteroids remain to be discovered. More research also is needed to determine if fewer mid-size objects (between 330 and 3,300-feet wide) also mean fewer potentially hazardous asteroids, those that come closest to Earth.

NEOWISE observations indicate that there are at least 40 percent fewer near-Earth asteroids in total that are larger than 330 feet, or 100 meters. Our solar system's four inner planets are shown in green, and our sun is in the center. Each red dot represents one asteroid. Object sizes are not to scale. Image credit: NASA / JPL-Caltech.

The results come from the most accurate census to date of near-Earth asteroids, the space rocks that orbit within 120 million miles (195 million kilometers) of the sun into Earth's orbital vicinity. WISE observed infrared light from those in the middle to large-size category. The survey project, called NEOWISE, is the asteroid-hunting portion of the WISE mission. Study results appear in the Astrophysical Journal.

"NEOWISE allowed us to take a look at a more representative slice of the near-Earth asteroid numbers and make better estimates about the whole population," said Amy Mainzer, lead author of the new study and principal investigator for the NEOWISE project at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, Calif. "It's like a population census, where you poll a small group of people to draw conclusions about the entire country."

This chart shows how data from NASA's Wide-field Infrared Survey Explorer, or WISE, has led to revisions in the estimated population of near-Earth asteroids. Image credit: NASA / JPL-Caltech.

WISE scanned the entire celestial sky twice in infrared light between January 2010 and February 2011, continuously snapping pictures of everything from distant galaxies to near-Earth asteroids and comets. NEOWISE observed more than 100 thousand asteroids in the main belt between Mars and Jupiter, in addition to at least 585 near Earth.

WISE captured a more accurate sample of the asteroid population than previous visible-light surveys because its infrared detectors could see both dark and light objects. It is difficult for visible-light telescopes to see the dim amounts of visible-light reflected by dark asteroids. Infrared-sensing telescopes detect an object's heat, which is dependent on size and not reflective properties.

This chart illustrates how infrared is used to more accurately determine an asteroid's size. Image credit: NASA / JPL-Caltech.

Though the WISE data reveal only a small decline in the estimated numbers for the largest near-Earth asteroids, which are 3,300 feet (1 kilometer) and larger, they show 93 percent of the estimated population have been found. This fulfills the initial "Spaceguard" goal agreed to with Congress. These large asteroids are about the size of a small mountain and would have global consequences if they were to strike Earth. The new data revise their total numbers from about 1,000 down to 981, of which 911 already have been found. None of them represents a threat to Earth in the next few centuries. It is believed that all near-Earth asteroids approximately 6 miles (10 kilometers) across, as big as the one thought to have wiped out the dinosaurs, have been found.

"The risk of a really large asteroid impacting the Earth before we could find and warn of it has been substantially reduced," said Tim Spahr, the director of the Minor Planet Center at the Harvard Smithsonian Center for Astrophysics in Cambridge, Mass.

This chart illustrates why infrared-sensing telescopes are more suited to finding small, dark asteroids than telescopes that detect visible light. Image credit: NASA / JPL-Caltech.

The situation is different for the mid-size asteroids, which could destroy a metropolitan area if they were to impact in the wrong place. The NEOWISE results find a larger decline in the estimated population for these bodies than what was observed for the largest asteroids. So far, the Spaceguard effort has found and is tracking more than 5,200 near-Earth asteroids 330 feet or larger, leaving more than an estimated 15,000 still to discover. In addition, scientists estimate there are more than a million unknown smaller near-Earth asteroids that could cause damage if they were to impact Earth.

"NEOWISE was just the latest asset NASA has used to find Earth's nearest neighbors," said Lindley Johnson, program executive for the Near Earth Object (NEO) Observation Program at NASA Headquarters in Washington. "The results complement ground-based observer efforts over the past 12 years. These observers continue to track these objects and find even more."

WISE Finds Fewer Asteroids near Earth

WISE is managed and operated by JPL for NASA's Science Mission Directorate in Washington. The principal investigator, Edward Wright, is at the University of California, Los Angeles. The WISE science instrument was built by the Space Dynamics Laboratory in Logan, Utah, and the spacecraft was built by Ball Aerospace and Technologies Corp. in Boulder, Colo. Science operations and data processing occur at the Infrared Processing and Analysis Center at the California Institute of Technology.

For more information about the mission, visit: 

Images (mentioned), Video, Text, Credits: NASA / JPL / Dwayne Brown / Whitney Clavin.


jeudi 29 septembre 2011

On the Baikonur cosmodrome launch rocket "Proton-M"

ILS - QuetzSat-1 Launch Mission poster.


On September 29 22 hours 32 minutes Moscow time from the launch complex area 200 Baikonur launch rocket "Proton-M" with the upper stage "Briz-M" spacecraft, and telecommunications "KvettsSat-1» (QuetzSat-1).

Launch of Proton-M with QuetzSat-1 Satellite

Start rocket "Proton-M" with the upper stage "Briz-M" was held as usual. The estimated time of separation of the spacecraft from the booster - 7 hours 45 minutes Moscow time, September 30, 2011.

Spacecraft "KvettsSat-1» (QuetzSat-1) - satellite communication in Ku-band, which is designed to provide communication services and broadcasting.


The contract for the use of carrier rocket "Proton-M" to run "KvettsSat-1» (QuetzSat-1) has concluded the company International Launch Services Inc. Controlling stake in ILS owned Federal State Unitary Enterprise "State Research and Production Space Center Khrunichev" which is a developer and manufacturer of "Proton-M" and the upper stage "Briz-M".

For more information about International Launch Servises (ILS), visit:

Images, Video, Text, Credits: Press Service of the Russian Space Agency (Roscosmos PAO) / ILS / Space Systems / Loral / Translation:


Galaxy Caught Blowing Bubbles

ESA - Hubble Space Telescope logo.

29 September 2011

 Hubble image of irregular galaxy Holmberg II

Hubble’s famous images of galaxies typically show elegant spirals or soft-edged ellipses. But these neat forms are only representative of large galaxies. Smaller galaxies like the dwarf irregular galaxy Holmberg II come in many shapes and types that are harder to classify. This galaxy’s indistinct shape is punctuated by huge glowing bubbles of gas, captured in this image from the NASA/ESA Hubble Space Telescope.

Wide-field image of irregular galaxy Holmberg II (ground-based image)

The intricate glowing shells of gas in Holmberg II were created by the energetic lifecycles of many generations of stars. High-mass stars form in dense regions of gas, and later in life expel strong stellar winds that blow away the surrounding material. At the very end of their lives, they explode in as a supernova. Shock waves rip through these less dense regions blowing out and heating the gas, forming the delicate shells we see today.

Zooming in on galaxy Holmberg II

Holmberg II is a patchwork of dense star-forming regions and extensive barren areas with less material, which can stretch across thousands of light-years. As a dwarf galaxy, it has neither the spiral arms typical of galaxies like the Milky Way nor the dense nucleus of an elliptical galaxy. This makes Holmberg II, gravitationally speaking, a gentle haven where fragile structures such as these bubbles can hold their shape.

Panning across galaxy Holmberg II

While the galaxy is unremarkable in size, Holmberg II does have some intriguing features. As well as its unusual appearance — which earned it a place in Halton Arp’s Atlas of Peculiar Galaxies, a treasure trove of weird and wonderful objects — the galaxy hosts an ultraluminous X-ray source in the middle of three gas bubbles in the top right of the image. There are competing theories as to what causes this powerful radiation — one intriguing possibility is an intermediate-mass black hole which is pulling in material from its surroundings.

This colourful image is a composite of visible and near-infrared exposures taken using the Wide Field Channel of Hubble’s Advanced Camera for Surveys.


The Hubble Space Telescope is a project of international cooperation between ESA and NASA.

Images, Text, Credits: NASA / ESA / Digitized Sky Survey 2 (Acknowledgement: Davide De Martin) / Videos: NASA / ESA / Digitized Sky Survey 2. Music: John Dyson (from the album Moonwind).


China has launched its space module lab called "Heavenly Palace" or Tiangong 1

CNSA - China National Space Agency logo.

Sept. 29, 2011

China has launched its space module lab called "Heavenly Palace" or Tiangong 1 which will remain in orbit for docking missions.

A Long March-2FT1 carrier rocket loaded with Tiangong-1 unmanned space lab module blasts off from the launch pad at the Jiuquan Satellite Launch Center in northwest China's Gansu Province, Sept. 29, 2011. (Xinhua/Wang Jianmin).

Long March-2FT1 carrier rocket loaded with Tiangong-1 launch

Commander-in-chief of China's manned space program Chang Wanquan announced Thursday night that the launch of Tiangong-1 space lab module is successful.

Reaching for the stars

Tiangong forms just one part of a much broader Chinese space exploration programme.

"Chinese acquisition of new technologies is not just for their intrinsic value, but because the leadership see them as symbols that distinguish great powers from their competitors ”

In 2007 China put the Chang-e 1 satellite into orbit around the Moon. It surveyed the Moon for two years before being deliberately crashed into the lunar surface in March 2009 as part of China's research into developing a robotic craft to return lunar samples, a mission likely to take place around 2014.

In 2017 China is due to land a lunar rover and there are longer term plans for a manned lunar base. In 2013 Yinghuo-1, a joint Chinese-Russian robot probe to Mars, will be launched. The manned space programme is crucial to achieving China's long-term political goals.

The successful orbiting of a "taikonaut" (Chinese astronaut) in 2003 was a dramatic assertion of China's rise. China became only the third country in history to orbit one of its own astronauts using a domestic launch technology.

 Tiangong-1 Space Lab In Orbit

China plans to orbit its own 60-tonne space station by 2020 and the purpose of the series of smaller Tiangong stations is to develop expertise in docking manoeuvres and longer term human spaceflight. The Tiangong-1 is an essential step toward the goal of building a space station.

Going it alone

China is the only country currently building a space station by itself, and with a clear plan to land humans on the moon.

For more information about China National Space Agency, visit:

Images, Video, Text, Credit: CNSA / / BBC / ITN /

Best regards,

ESA spacecraft reveal new anatomy around a black hole

ESA - XMM-Newton Mission patch.

29 September 2011

A fleet of spacecraft including ESA's XMM-Newton and Integral have shown unprecedented details close to a supermassive black hole. They reveal huge 'bullets' of gas being driven away from the 'gravitational monster'.

The black hole that the team chose to study lies at the heart of the galaxy Markarian 509, 500 million light years away in space. This black hole is colossal, containing 300 million times the mass of the Sun and growing more massive every day as it continues to feed.

Markarian 509 was chosen because it is known to vary in brightness, which indicates that the flow of matter into the black hole is turbulent. The radiation from this inner region then drives an outflow of some gas away from the black hole.

Active Galaxy Markarian 509

The black hole was monitored for 100 days. "XMM-Newton really led these observations because it has such a wide X-ray coverage, as well as an optical monitoring camera," says Jelle Kaastra, SRON Netherlands Institute for Space Research, who coordinated an international team of 26 astronomers from 21 institutes on four continents to make these observations.

During the campaign, the galaxy surpassed itself; instead of the usual 25 percent fluctuations in its brightness, it leapt up in the soft X-ray band by 60 percent, indicating that a major disturbance occurred in the gas flow to the black hole's deadly clutches.

The resulting observations have shown that the outflow consists of giant bullets propelled at millions of kilometres per hour. The bullets are stripped away from a dusty reservoir of matter waiting to fall into the black hole. The surprise is that the reservoir is situated more than 15 light years away from the black hole. This is further than some astronomers thought was possible for the wind to originate.

"There has been a debate in astronomy for some time about the origin of the outflowing gas," says Kaastra.

Image above: An artist's impression of the central engine of an active galaxy. A black hole is surrounded by matter waiting to fall in.

The dusty gas reservoir takes the form of a doughnut-shaped torus that surrounds the black hole. Matter spirals in towards the black hole, creating an accretion disc in which the gas behaves like water spiralling down a plughole.

The observations also show that the accretion disc features a 'skin' of gas with a temperature of millions of degrees. This is where the X-rays and gamma rays come from to drive the more distant gas outwards.

In addition to XMM-Newton and Integral, they used the NASA/ESA Hubble Space Telescope, NASA's Chandra and Swift satellites, and the ground-based telescopes WHT and PARITEL. Together the instruments gave them unprecedented wavelength coverage: running from the infrared, through the visible, ultraviolet, X-rays and into the gamma-ray band.

"The results underline how important long-term observations and monitoring campaigns are to gain a deeper understanding of variable astrophysical objects. XMM-Newton made all the necessary organisational changes to enable such observations, and now the effort is paying off," says Norbert Schartel, ESA XMM-Newton Project Scientist.

More about XMM-Newton:

XMM-Newton operations:

Images, Text, Credits: NASA / ESA / J. Kriss (STScI) and J. de Plaa (SRON) / M. Weiss (Chandra X-ray Center).


mercredi 28 septembre 2011

The Pacman Nebula

NASA - Chandra X-ray Observatory patch.

Sept. 28, 2011

High-mass stars are important because they are responsible for much of the energy pumped into our galaxy over its lifetime. Unfortunately, these stars are poorly understood because they are often found relatively far away and can be obscured by gas and dust. The star cluster NGC 281 is an exception to this rule. It is located about 6,500 light years from Earth and, remarkably, almost 1,000 light years above the plane of the galaxy, giving astronomers a nearly unfettered view of the star formation within it.

This composite image of NGC 281 contains X-ray data from Chandra, in purple, with infrared observations from Spitzer, in red, green, blue. The high-mass stars in NGC 281 drive many aspects of their galactic environment through powerful winds flowing from their surfaces and intense radiation that creates charged particles by stripping electrons off atoms. The eventual deaths of massive stars as supernovas will also seed the galaxy with material and energy.

NGC 281 is known informally as the "Pacman Nebula" because of its appearance in optical images. In optical images the "mouth" of the Pacman character appears dark because of obscuration by dust and gas, but in the infrared Spitzer image the dust in this region glows brightly.

NGC 281 is typically divided into two subregions: the region in the upper middle of the image, which is surrounded by the purple 10-million-degree gas, and a younger region in the lower part of the image. There is evidence that the formation of a cluster, appearing in a beige cloud to the lower right, was triggered by a previous generation of star formation. Also, astronomers have found some isolated star formation on the left side of the image that appears to have been occurring at the same time as star formation in other regions of the cluster. This supports the idea that something externally triggered the "baby boom" of stars in NGC 281.

NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra's science and flight operations from Cambridge, Mass.

For more information about the Chandra mission and this result, including images and other multimedia, visit: and

Image, Text,  Credits: X-ray: NASA / CXC / CfA / S.Wolk; IR: NASA / JPL / CfA / S.Wolk.


Venus Weather Not Boring After All, NASA / International Study Shows

NASA - PIONEER patch / ESA - Venus Express Mission patch.


At first glance, a weather forecaster for Venus would have either a really easy or a really boring job, depending on your point of view. The climate on Venus is widely known to be unpleasant -- at the surface, the planet roasts at more than 800 degrees Fahrenheit under a suffocating blanket of sulfuric acid clouds and a crushing atmosphere more than 90 times the pressure of Earth's. Intrepid future explorers should abandon any hope for better days, however, because it won't change much.

"Any variability in the weather on Venus is noteworthy, because the planet has so many features to keep atmospheric conditions the same," says Dr. Tim Livengood, a researcher with the National Center for Earth and Space Science Education, Capitol Heights, Md., and now with the University of Maryland, College Park, Md.

Image above: Ultraviolet image of Venus' clouds as seen by the Pioneer Venus Orbiter (Feb. 26, 1979). Credit: NASA.

"Earth has seasons because its rotation axis is tilted by about 23 degrees, which changes the intensity of sunlight and the length of the day in each hemisphere throughout the year. However, Venus has been tilted so much, it's almost completely upside down, leaving it with a net tilt of less than three degrees from the sun, so the seasonal effect is negligible," explains Livengood, who is stationed at NASA's Goddard Space Flight Center in Greenbelt, Md. "Also, its orbit is even more circular than Earth's, which prevents it from getting significantly hotter or cooler by moving closer to or further away from the sun. And while you might expect things to cool down at night -- especially since Venus rotates so slowly that its night lasts almost two Earth months -- the thick atmosphere and sulfuric acid clouds act like a blanket while winds move heat around, keeping temperatures pretty even. Finally, almost all the planet's water has escaped to space, so you don't get any storms or precipitation like on Earth where water evaporates and condenses as clouds."

However, higher up, the weather gets more interesting, according to a new study of old data by NASA and international scientists. The team detected strange things going on in data from telescopic observations of Venus in infrared light at about 68 miles (110 kilometers) above the planet's surface, in cold, clear air above the acid clouds, in two layers called the mesosphere and the thermosphere.

"Although the air over the polar regions in these upper atmospheric layers on Venus was colder than the air over the equator in most measurements, occasionally it appeared to be warmer," said Dr. Theodor Kostiuk of NASA Goddard. "In Earth's atmosphere, a circulation pattern called a 'Hadley cell' occurs when warm air rises over the equator and flows toward the poles, where it cools and sinks. Since the atmosphere is denser closer to the surface, the descending air gets compressed and warms the upper atmosphere over Earth's poles. We saw the opposite on Venus. In addition, although the surface temperature is fairly even, we've seen substantial changes – up to 54 degrees Fahrenheit (about 30 K change) – within a few Earth days in the mesosphere – thermosphere layers over low latitudes on Venus. The poles appeared to be more stable, but we still saw changes up to 27 degrees Fahrenheit (about 15 K change)."

Kostiuk and Livengood are co-authors of a paper about these observations that appeared July 23 in the online edition of the journal Icarus.

A set of images of the Venus south polar vortex in infrared light (at 3.8 microns) acquired by the Visible and Infrared Thermal Imaging Spectrometer instrument on ESA's Venus Express spacecraft. The images show the temperature of the cloud tops at about 65 km (40.4 miles) altitude. A darker region corresponds to higher temperature and thus lower altitude. The center of the vortex, at a temperature of about 250K (around minus 9.7 degrees Fahrenheit), is the deepest zone, exhibiting the highest temperature. Credit: ESA / VIRTIS / INAF-IASF / Obs. de Paris-LESIA.

"The mesosphere and thermosphere of Venus are dynamically active," said lead author Dr. Guido Sonnabend of the University of Cologne, Germany. "Wind patterns resulting from solar heating and east to west zonal winds compete, possibly resulting in altered local temperatures and their variability over time."

This upper atmospheric variability could have many possible causes, according to the team. Turbulence from global air currents at different altitudes flowing at more than 200 miles per hour in opposite directions could exchange hot air from below with cold air from above to force changes in the upper atmosphere. Also, giant vortexes swirl around each pole. They, too, could generate turbulence and change the pressure, causing the temperature to vary.

Since the atmospheric layers the team observed are above the cloud blanket, they may be affected by changes in sunlight intensity as day transitions to night, or as latitude increases toward the poles. These layers are high enough that they could even be affected by solar activity (the solar cycle), such as solar explosions called flares and eruptions of solar material called coronal mass ejections.

Changes were seen over periods spanning days, to weeks, to a decade. Temperatures measured in 1990-91 are warmer than in 2009. Measurements obtained in 2007 using Goddard’s Heterodyne Instrument for Planetary Wind and Composition (HIPWAC) observed warmer temperature in the equatorial region than in 2009. Having seen that the atmosphere can change, a lot more observations are needed to determine how so many phenomena can affect Venus' upper atmosphere over different intervals, according to the team.

"In addition to all these changes, we saw warmer temperatures than those predicted for this altitude by the leading accepted model, the Venus International Reference Atmosphere model," said Kostiuk. "This tells us that we have lots of work to do updating our upper atmospheric circulation model for Venus."

Image above: The Heterodyne Instrument for Planetary Winds And Composition (HIPWAC) on the NASA 3-meter Infrared Telescope Facility (IRTF) on Mauna Kea Observatory in Hawaii. HIPWAC is the successor to the older Infrared Heterodyne Spectrometer (IRHS) instrument. Credit: NASA.

Although Venus is often referred to as Earth's twin, since they are almost the same size, it ended up with a climate very different from Earth. A deeper understanding of Venus' atmosphere will let researchers compare it to the evolution of Earth's atmosphere, giving insight as to why Earth now teems with life while Venus suffered a hellish fate.

The team measured temperature and wind speeds in Venus' upper atmosphere by observing an infrared glow emitted by carbon dioxide (CO2) molecules when they were energized by light from the sun. Infrared light is invisible to the human eye and is perceived by us as heat, but it can be detected by special instruments. In the research, it appeared as a line on a graph from a spectrometer, an instrument that separates light into its component colors, each of which corresponds to a specific frequency. The width of the line revealed the temperature, while shifts in its frequency gave the wind speed.

The researchers compared observations from 1990 and 1991 using Goddard's Infrared Heterodyne Spectrometer instrument at NASA's Infrared Telescope Facility on Mauna Kea, Hawaii, to observations from 2009 using the Cologne Tunable Heterodyne Infrared Spectrometer instrument at the National Optical Astronomy Observatory's McMath Telescope at Kitt Peak, Ariz.

Related links:
Giant vortexes swirl around each pole:

Solar activity (the solar cycle):

Heterodyne Instrument for Planetary Wind and Composition (HIPWAC):

Images (mentioned), Text, Credit: NASA's Goddard Space Flight Center /  Bill Steigerwald.

Best regards,

Feast your Eyes on the Fried Egg Nebula

ESO - European Southern Observatory logo.

28 September 2011

ESO's VLT spots a rare treat

 The Fried Egg Nebula

Astronomers have used ESO’s Very Large Telescope to image a colossal star that belongs to one of the rarest classes of stars in the Universe, the yellow hypergiants. The new picture is the best ever taken of a star in this class and shows for the first time a huge dusty double shell surrounding the central hypergiant. The star and its shells resemble an egg white around a yolky centre, leading the astronomers to nickname the object the Fried Egg Nebula.

The monster star, known to astronomers as IRAS 17163-3907 [1], has a diameter about a thousand times bigger than our Sun. At a distance of about 13 000 light-years from Earth, it is the closest yellow hypergiant found to date and new observations show it shines some 500 000 times more brightly than the Sun [2].

The Fried Egg Nebula in the constellation of Scorpius

“This object was known to glow brightly in the infrared but, surprisingly, nobody had identified it as a yellow hypergiant before,” said Eric Lagadec (European Southern Observatory), who led the team that produced the new images.

The observations of the star and the discovery of its surrounding shells were made using the VISIR infrared camera on the VLT. The pictures are the first of this object to clearly show the material around it and reveal two almost perfectly spherical shells.

If the Fried Egg Nebula were placed in the centre of the Solar System the Earth would lie deep within the star itself and the planet Jupiter would be orbiting just above its surface. The much larger surrounding nebula would engulf all the planets and dwarf planets and even some of the comets that orbit far beyond the orbit of Neptune. The outer shell has a radius of 10 000 times the distance from the Earth to the Sun.

Wide-field image of the sky around the Fried Egg nebula

Yellow hypergiants are in an extremely active phase of their evolution, undergoing a series of explosive events — this star has ejected four times the mass of the Sun in just a few hundred years [3]. The material flung out during these bursts has formed the extensive double shell of the nebula, which is made of dust rich in silicates and mixed with gas.

This activity also shows that the star is likely to soon die an explosive death — it will be one of the next supernova explosions in our galaxy [4]. Supernovae provide much-needed chemicals to the surrounding interstellar environment and the resulting shock waves can kick start the formation of new stars.

Zooming in on The Fried Egg Nebula

The Very Large Telescope mid-IR instrument, VISIR, captured this delicious image of the Fried Egg Nebula through three mid-infrared filters that are here coloured blue, green and red [5].


[1] The name indicates that the object was first spotted as an infrared source by the IRAS satellite in 1983 and the numbers show the star’s place in the sky, in the heart of the Milky Way in the constellation of Scorpius (The Scorpion).

[2] IRAS 17163-3907 is one of the 30 brightest stars in the infrared sky, at the wavelength of 12 microns observed by IRAS, but it had been overlooked because it is quite faint in visible light.

[3] The total mass of this star is estimated to be roughly twenty times that of the Sun.

[4] After burning all their hydrogen all stars of ten solar masses or more become red supergiants. This phase ends when the star has finished burning all of its helium. Some of these high-mass stars then spend just a few million years in the post-red supergiant phase as yellow hypergiants, a relatively short time in the life of a star, before rapidly evolving into another unusual type of star called a luminous blue variable. These hot and brilliant stars are continuously varying in brightness and are losing matter due to the strong stellar winds they expel. But this is not the end of the star’s evolutionary adventure, as it may next become a different kind of unstable star known as a Wolf-Rayet star (, before ending its life as a violent supernova explosion.

[5] The three mid-infrared filters that were used passed light at wavelengths around 8590 nm (coloured blue), 11 850 nm (coloured green) and 12 810 nm (coloured red).

More information:

This research is presented in a paper “A double detached shell around a post-Red Supergiant: IRAS 17163-3907, the Fried Egg nebula" by E. Lagadec et al., accepted for publication in the journal Astronomy & Astrophysics.

The team is composed of E. Lagadec (ESO, Garching, Germany), A.A. Zijlstra (Jodrell Bank Center For Astrophysics, Manchester, UK), R.D. Oudmaijer (University of Leeds, UK), T. Verhoelst (Instituut voor Sterrenkunde, Leuven, Belgium), N.L.J. Cox (Instituut voor Sterrenkunde), R. Szczerba (N. Copernicus Astronomical Center, Torun, Poland), D. Mékarnia (Observatoire de la Côte d’Azur, Nice, France) and H. van Winckel (Instituut voor Sterrenkunde).

ESO, the European Southern Observatory, is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive astronomical observatory. It is supported by 15 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning a 40-metre-class European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.


    Research paper: A&A paper:

Images, Text, Credits: ESO / E. Lagadec / Digitized Sky Survey 2 / IAU and Sky & Telescope / Video: ESO, Nick Risinger ( and Digitized Sky Survey 2. Music: John Dyson (from the album Moonwind).


mardi 27 septembre 2011

MESSENGER Team Delivers First Orbital Data to Planetary Data System

NASA - MESSENGER "Mission to Mercury" patch.

Sept. 27, 2011

Data collected during MESSENGER’s first two months in orbit around Mercury have been released to the public by the Planetary Data System (PDS), an organization that archives and distributes all of NASA’s planetary mission data. Calibrated data from all seven of MESSENGER’s science instruments, plus radio science data from the spacecraft telecommunications system, are included in this release.

“It's a real milestone for the first data ever obtained from orbit around Mercury to be available now in the PDS,” says Nancy Chabot, Instrument Scientist for MESSENGER’s Mercury Dual Imaging System (MDIS).

Goethe Basin in Mercury's North

“Scientists around the world will use these data to better understand Mercury and the formation and evolution of our solar system as a whole,” says Chabot, of the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md. “However, to me, one of the most exciting aspects of this release is that these data now in the PDS are just the first of much more to come. MESSENGER continues to send us new data practically every day!”

The science results from these instruments have already shed light on questions about Mercury that have lingered for more than three decades. Many of these results were highlighted in a June 16 press conference at NASA headquarters.

Footprints of the MASCS Instrument on Mercury's Surface

For instance, says MESSENGER Project Scientist Ralph McNutt of APL, “The imaging has highlighted the importance of volcanism in plains formation in the planet’s history, and the geochemical remote sensing instruments are providing new insights into formation scenarios for the planet. Geophysics data are yielding new information on Mercury’s internal structure, and data from the exosphere and magnetosphere instruments are giving us the first continuous view of Mercury’s interaction with its local space environment.

“The availability of these data via PDS will allow scientists around the world to study the data and begin making even more connections and discoveries,” McNutt adds.

Coverage Density of the GRS Sensor on the GRNS Instrument

Since the mid-1990s, NASA has required all of its planetary missions to archive data in the PDS, an active archive that makes available well-documented, peer-reviewed data to the research community. The PDS includes eight university/research center science teams, called discipline nodes, each of which specializes in a specific area of planetary data. The contributions from these nodes provide a data-rich source for scientists, researchers, and developers.

“PDS deliveries are the result of a concerted effort between the MESSENGER team and the PDS that starts well before the release to the public,” says APL’s Susan Ensor, MESSENGER’s Science Operations Center lead. “Approximately 50 MESSENGER team members were actively involved in making this PDS delivery, including instrument team members, developers from Applied Coherent Technology Corporation, and Science Operations Center personnel.”

Footprints of the MDIS Instrument on Mercury's Surface

Previous MESSENGER PDS deliveries included data from cruise and flybys of the Earth, Venus, and Mercury. The data for this delivery are archived and available online at, and all of the MESSENGER data archived at the PDS thus far are available at As of this release, MESSENGER will have delivered 1.1 terabytes of raw and calibrated data to the PDS, including more than 30,000 images (of which over 18,000 are from orbit).

The team will submit three more PDS deliveries at six-month intervals from MESSENGER’s primary mission. “Improved calibrations will be incorporated in these future deliveries,” Ensor says. “Advanced products, including Mercury maps, will be included in the final primary mission delivery in March 2013.”

Areas Targeted for Imaging at High Resolution

The MESSENGER team has created an innovative software tool with which the public can view data from this delivery. ACT-REACT-Quick Map provides a simple, interactive Web interface to MESSENGER data. Developed by Applied Coherent Technology Corporation, Quick Map allows users to examine global mosaics constructed with high-resolution images from this PDS delivery.

The tool also provides weekly updates of coverage for surface-observing instruments, as well as the status of specially targeted MDIS observations. Information is also available that can be used to locate MESSENGER data products at the PDS. QuickMap can be accessed via links on each of the MESSENGER websites at and

“The MESSENGER team is delighted to share the orbital observations of Mercury with the planetary science community and the public,” adds MESSENGER Principal Investigator Sean Solomon, of the Carnegie Institution of Washington. “The first global exploration of our solar system’s innermost planet is a wonderful adventure, and there are plenty of front-row seats for all to participate.”

Images, Text, Credits: NASA / Johns Hopkins University Applied Physics Laboratory / Carnegie Institution of Washington.


Asteroid Caught Marching Across Tadpole Nebula

NASA - Wide-field Infrared Survey Explorer (WISE) logo.

Sept. 27, 2011

This infrared image from NASA's Wide-field Infrared Survey Explorer, or WISE, showcases the Tadpole Nebula, a star-forming hub in the Auriga constellation about 12,000 light-years from Earth. As WISE scanned the sky, capturing this mosaic of stitched-together frames, it happened to catch an asteroid in our solar system passing by. The asteroid, called 1719 Jens, left tracks across the image. A second asteroid was also observed cruising by.

But that's not all that WISE caught in this busy image -- two natural satellites orbiting above WISE streak through the image, appearing as faint green trails. This Tadpole region is chock full of stars as young as only a million years old -- infants in stellar terms -- and masses over 10 times that of our sun. It is called the Tadpole nebula because the masses of hot, young stars are blasting out ultraviolet radiation that has etched the gas into two tadpole-shaped pillars, called Sim 129 and Sim 130. These "tadpoles" appear as the yellow squiggles near the center of the frame. The knotted regions at their heads are likely to contain new young stars. WISE's infrared vision is helping to ferret out hidden stars such as these.

The 1719 Jens asteroid, discovered in 1950, orbits in the main asteroid belt between Mars and Jupiter. The space rock, which has a diameter of 19 kilometers (12 miles), rotates every 5.9 hours and orbits the sun every 4.3 years.

Twenty-five frames of the region, taken at all four of the wavelengths detected by WISE, were combined into this one image. The space telescope caught 1719 Jens in 11 successive frames. Infrared light of 3.4 microns is color-coded blue: 4.6-micron light is cyan; 12-micron-light is green; and 22-micron light is red.

WISE is an all-sky survey, snapping pictures of the whole sky, including everything from asteroids to stars to powerful, distant galaxies.

Image, Text,  Credit: NASA / JPL-Caltech / UCLA.


European experts follow satellite reentry

ESA - ESOC logo.

27 September 2011

ESA closely monitored the reentry on 24 September of the UARS observatory satellite. The Agency's Space Debris Office worked with NASA and international partners in a coordinated prediction and risk-assessment exercise.

NASA's non-operational Upper Atmosphere Research Satellite (UARS) reentered Earth's atmosphere on 24 September 2011 between 05:23 and 07:09 CEST. The precise reentry time and location of debris impacts from the 5.6-tonne satellite have not been determined. No injuries or damage have been reported.

Artist's impression of UARS

Since the beginning of the space age, there has been no confirmed report of an injury resulting from reentering space objects.

"Atmospheric drag reduced the satellite's speed from 27 000 km/h such that the remaining fragments might have reached the surface at just 200 km/h," said Prof. Heiner Klinkrad, Head of ESA's Space Debris Office. 

ESA central to international tracking exercise

The reentry was closely monitored by ESA experts working with international partners in a technical body known as the Inter-Agency Debris Coordination Committee (IADC).

ESA also communicated regular updates to European civil protection authorities.

IADC is an inter-agency forum for the worldwide coordination of activities related to the issues of man-made and natural debris in space. Member agencies include ESA, NASA, European national agencies and the Russian, Chinese, Canadian, Japanese, Ukrainian and Indian space agencies.

In recent years, IADC members have developed a data communication network specifically supporting hazardous reentry risk assessment, which allows the exchange of tracking data and the refinement of reentry predictions in the event of an expected reentry.

Central IADC data server at ESOC, Darmstadt

The server for the network is located at ESOC, ESA's Space Operations Centre, Darmstadt, Germany, where it is managed by the Space Debris Office.

ESOC: home to ESA's mission operations

"Last week's reentry did not meet IADC's scientific criterion as a 'risk object'. However, the network is exercised annually, and, upon NASA's initiative, the UARS reentry was selected by IADC as a target for the 2011 exercise," said Klinkrad.

Results of the UARS reentry exercise will be used by IADC members to improve reentry models and make predictions more accurate.

For more than 20 years, the Space Debris Office has been working closely with international partners to improve the understanding of orbital debris, work on mitigation measures and share research results.

Future developments of European observation capacity

In 2009, ESA launched the Space Situational Awareness Preparatory Programme (SSA-PP), aiming to increase Europe's capabilities to detect, predict and assess the risk to life and property due to man-made space objects, reentries, on-orbit collisions, potential impacts of Near Earth Objects, and the effects of space weather.

SSA systems: detecting space hazards

"One role of the SSA programme is to further develop European capabilities that will provide Europe accurate follow-up and reentry predictions of these kinds of events," says Nicolas Bobrinsky, Head of the SSA-PP Office.

"A longer warning time and more accurate predictions will assist civil authorities to react in the most appropriate manner, protecting people and property on Earth."

"No NASA human casualty reentry risk limits existed when UARS was designed, built, and launched. Today, ESA and many IADC members seek to limit human injury reentry risks to below 1 in 10 000. This is reflected in the long-standing interest in space debris mitigation and debris detection by ESA and other spacefaring organisations."

Related links:

Access an extended version of this article:

Space Debris:

Space Situational Awareness:

Inter-Agency Space Debris Coordination Committee (IADC):

Images, Text, Credits: ESA / J. Mai / P. Carrill / NASA.

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lundi 26 septembre 2011

Electrical Circuit Between Saturn and Enceladus

NASA - ESA Cassini "Insider's" Mission logo.

Sept. 26, 2011

This artist's concept shows a glowing patch of ultraviolet light near Saturn's north pole that occurs at the "footprint" of the magnetic connection between Saturn and its moon Enceladus. The footprint and magnetic field lines are not visible to the naked eye, but were detected by the ultraviolet imaging spectrograph and the fields and particles instruments on NASA's Cassini spacecraft. The footprint, newly discovered by Cassini, marks the presence of an electrical circuit that connects Saturn with Enceladus and accelerates electrons and ions along the magnetic field lines. In this image, the footprint is in the white box marked on Saturn, with the magnetic field lines in white and purple.

A larger white square above Enceladus shows a cross-section of the magnetic field line between the moon and the planet. This pattern of energetic protons was detected by Cassini's magnetospheric imaging instrument (MIMI) on Aug. 11, 2008.

The patch near Saturn's north pole glows because of the same phenomenon that makes Saturn's well-known north and south polar auroras glow: energetic electrons diving into the planet's atmosphere. However, the "footprint" is not connected to the rings of auroras around Saturn's poles (shown as an orange ring around the north pole in this image).

The Cassini plasma spectrometer complemented the MIMI data, with detection of field-aligned electron beams in the area. A team of scientists analyzed the charged particle data and concluded that the electron beams had sufficient energy flux to generate a detectable level of auroral emission at Saturn. Target locations were provided to Cassini's ultraviolet imaging spectrograph team. On Aug. 26, 2008, the spectrograph obtained images of an auroral footprint in Saturn's northern hemisphere.

The newly discovered auroral footprint measured about 1,200 kilometers (750 miles) in the longitude direction and less than 400 kilometers (250 miles) in latitude, covering an area comparable to that of California or Sweden. It was located at about 65 degrees north latitude.

In the brightest image the footprint shone with an ultraviolet light intensity of about 1.6 kilorayleighs, far less than the Saturnian polar auroral rings. This is comparable to the faintest aurora visible at Earth without a telescope in the visible light spectrum. Scientists have not yet found a matching footprint at the southern end of the magnetic field line.

The background star field and false color images of Saturn and Enceladus were obtained by Cassini's imaging science subsystem.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, Calif. manages the mission for NASA's Science Mission Directorate, Washington, D.C. The ultraviolet imaging spectrograph team is based at the University of Colorado, Boulder. The magnetospheric imaging team is based at the Johns Hopkins University Applied Physics Laboratory, Laurel, Md. The Cassini plasma spectrometer team is based at the Southwest Research Institute, San Antonio, Texas.

For more information about the Cassini-Huygens mission visit and

Image, Text,  Credits: NASA / JPL / JHUAPL / University of Colorado / Central Arizona College / SSI.