vendredi 18 octobre 2013

Asteroid 2013 TV135 – A Reality Check











Asteroid Watch.

Oct. 18, 2013

Newly discovered asteroid 2013 TV135 made a close approach to Earth on Sept. 16, when it came within about 4.2 million miles (6.7 million kilometers). The asteroid is initially estimated to be about 1,300 feet (400 meters) in size and its orbit carries it as far out as about three quarters of the distance to Jupiter's orbit and as close to the sun as Earth's orbit. It was discovered on Oct. 8, 2013, by astronomers working at the Crimean Astrophysical Observatory in Ukraine. As of Oct. 14, asteroid 2013 TV135 is one of 10,332 near-Earth objects that have been discovered.

With only a week of observations for an orbital period that spans almost four years, its future orbital path is still quite uncertain, but this asteroid could be back in Earth’s neighborhood in 2032. However, NASA’s Near-Earth Object Program Office states the probability this asteroid could then impact Earth is only one in 63,000. The object should be easily observable in the coming months and once additional observations are provided to the Minor Planet Center in Cambridge, Mass., the initial orbit calculations will be improved and the most likely result will be a dramatic reduction, or complete elimination, of any risk of Earth impact.


This diagram (above) shows the orbit of asteroid 2013 TV135 (in blue), which has just a 1-in-63,000 chance of impacting Earth. Its risk to Earth will likely be further downgraded as scientists continue their investigations. Image Credit: NASA/JPL-Caltech.

"To put it another way, that puts the current probability of no impact in 2032 at about 99.998 percent," said Don Yeomans, manager of NASA's Near-Earth Object Program Office at the Jet Propulsion Laboratory in Pasadena, Calif. "This is a relatively new discovery. With more observations, I fully expect we will be able to significantly reduce, or rule out entirely, any impact probability for the foreseeable future."

Artist's view of a near Earth object (meteorite) pass. Image credit: NASA.

NASA detects, tracks and characterizes asteroids and comets passing close to Earth using both ground- and space-based telescopes. The Near-Earth Object Observations Program, commonly called "Spaceguard," discovers these objects, characterizes a subset of them and identifies their orbits to determine if any could be potentially hazardous to our planet.

JPL manages the Near-Earth Object Program Office for NASA's Science Mission Directorate in Washington. JPL is a division of the California Institute of Technology in Pasadena.

More information about asteroids and near-Earth objects is at: http://www.jpl.nasa.gov/asteroidwatch

Images (mentioned), Text, Credits:  NASA /  JPL / D.C. Agle.

Greetings, Orbiter.ch

High Above Saturn












NASA / ESA - Cassini-Huygens Mission patch.

October 17, 2013


This portrait looking down on Saturn and its rings was created from images obtained by NASA's Cassini spacecraft on Oct. 10, 2013. It was made by amateur image processor and Cassini fan Gordan Ugarkovic. This image has not been geometrically corrected for shifts in the spacecraft perspective and still has some camera artifacts.The mosaic was created from 12 image footprints with red, blue and green filters from Cassini's imaging science subsystem. Ugarkovic used full color sets for 11 of the footprints and red and blue images for one footprint.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini-Huygens mission visit http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov and http://www.esa.int/Our_Activities/Space_Science/Cassini-Huygens

Image, Text,  Credits: NASA/JPL-Caltech/Space Science Institute/G. Ugarkovic.

Cheers, Orbiter.ch

NASA Rover Confirms Mars Origin of Some Meteorites










NASA - Mars Science Laboratory (MSL) logo.

October 17, 2013

Examination of the Martian atmosphere by NASA's Curiosity Mars rover confirms that some meteorites that have dropped to Earth really are from the Red Planet.

A key new measurement of the inert gas argon in Mars' atmosphere by Curiosity's laboratory provides the most definitive evidence yet of the origin of Mars meteorites while at the same time providing a way to rule out Martian origin of other meteorites.


Image above: This self-portrait of NASA's Mars rover Curiosity combines 66 exposures taken by the rover's Mars Hand Lens Imager (MAHLI) during the 177th Martian day, or sol, of Curiosity's work on Mars (Feb. 3, 2013). Image credit: NASA/JPL-Caltech/MSSS.

The new measurement is a high-precision count of two forms of argon -- argon-36 and argon-38 -- accomplished by the Sample Analysis at Mars (SAM) instrument inside the rover. These lighter and heavier forms, or isotopes, of argon exist naturally throughout the solar system. On Mars the ratio of light to heavy argon is skewed because much of that planet's original atmosphere was lost to space. The lighter form of argon was taken away more readily because it rises to the top of the atmosphere more easily and requires less energy to escape. That left the Martian atmosphere relatively enriched in the heavier isotope, argon-38.

Years of past analyses by Earth-bound scientists of gas bubbles trapped inside Martian meteorites had already narrowed the Martian argon ratio to between 3.6 and 4.5 (that is 3.6 to 4.5 atoms of argon-36 to every one of argon-38). Measurements by NASA's Viking landers in the 1970s put the Martian atmospheric ratio in the range of four to seven. The new SAM direct measurement on Mars now pins down the correct argon ratio at 4.2.

"We really nailed it," said Sushil Atreya of the University of Michigan, Ann Arbor, lead author of an Oct. 16 paper reporting the finding in Geophysical Research Letters. "This direct reading from Mars settles the case with all Martian meteorites."

One reason scientists have been so interested in the argon ratio in Martian meteorites is that it was -- before Curiosity -- the best measure of how much atmosphere Mars has lost since the planet's wetter, warmer days billions of years ago. Figuring out the planet's atmospheric loss would enable scientists to better understand how Mars transformed from a once water-rich planet, more like our own, into today's drier, colder and less-hospitable world.

Had Mars held onto all of its atmosphere and its original argon, its ratio of the gas would be the same as that of the sun and Jupiter. Those bodies have so much gravity that isotopes can't preferentially escape, so their argon ratio -- which is 5.5 -- represents that of the primordial solar system.

While argon makes up only a tiny fraction of the gas lost to space from Mars, it is special because it's a noble gas. That means the gas is inert, not reacting with other elements or compounds, and therefore a more straightforward tracer of the history of the Martian atmosphere.

"Other isotopes measured by SAM on Curiosity also support the loss of atmosphere, but none so directly as argon," said Atreya. "Argon is the clearest signature of atmospheric loss because it's chemically inert and does not interact or exchange with the Martian surface or the interior. This was a key measurement that we wanted to carry out on SAM."

The Curiosity measurements do not directly measure the current rate of atmospheric escape, but NASA's next mission to Mars, the Mars Atmosphere and Volatile Evolution Mission (MAVEN), is designed to do so. That mission is being prepared at NASA's Kennedy Space Center in Florida for a launch-opportunity period that begins on Nov. 18.

Curiosity landed inside Gale Crater on Mars in August 2012 and is investigating evidence about habitable environments there. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission and built the rover for NASA's Science Mission Directorate in Washington. The rover's SAM suite of instruments was developed at NASA's Goddard Space Flight Center in Greenbelt, Md., with instrument contributions from Goddard, JPL and the University of Paris in France.

For more information about the mission, visit http://www.nasa.gov/msl and http://mars.jpl.nasa.gov/msl . To learn more about the SAM instrument, visit: http://ssed.gsfc.nasa.gov/sam/index.html .

You can follow Curiosity's mission on Facebook at http://www.facebook.com/marscuriosity and on Twitter at http://www.twitter.com/marscuriosity

Image (mentioned), Text, Credits: NASA / JPL / Guy Webster.

Best regards, Orbiter.ch

Celebrating the Legacy of ESA's Plank Mission












ESA - Planck Mission patch.

18 October 2013

From the tiniest fraction of a second after the Big Bang to the evolution of stars and galaxies over 13.8 billion years, ESA’s Planck space telescope has provided new insight into the history of our Universe. Although science observations are now complete, the legacy of the Planck mission lives on.

video
Planck’s view of the Universe

Planck was launched in 2009 and spent 4.5 years scanning the sky to study the evolution of cosmic matter over time. Tomorrow, the Low Frequency Instrument will be switched off, having completed its science operations on 3 October.

Planck’s High Frequency Instrument already ended its observations in January 2012, after a total of five all-sky surveys had been completed with both instruments.

With some operational procedures to still take place, the spacecraft will finally be switched off next week.

The most precise view of our Universe

Earlier this year, cosmologists working on the Planck data delivered the most precise image of the cosmic microwave background – CMB, the relic radiation from the Big Bang that was imprinted on the sky when the Universe was only 380 000 years old.

The CMB is the most accurate snapshot of the matter distribution in the early Universe. It shows tiny temperature fluctuations that correspond to regions of slightly different densities at very early times, representing the seeds of all future structure, the stars and galaxies of today.

Planck and the Cosmic microwave background

“Planck has delivered the most precise all-sky image of the CMB that is enabling us to test a huge variety of models of the origin and evolution of the cosmos,” says Jan Tauber, ESA’s Planck project scientist.

“But long and meticulous work was required before we could start exploiting this wealth of cosmological information, since the CMB is hidden behind foreground glare including emissions from material within our own Galaxy, as well as from other galaxies and galaxy clusters.”

For example, Planck has made the most extensive catalogue of the largest galaxy clusters, the most massive building blocks in our Universe. Planck has also identified the densest and coldest clumps of matter in our Galaxy, cool reservoirs of material from which new stars may be born in the future.

But these are only two examples of the wide range of topics that the Planck data archive has provided new information.

New cosmic recipe

Looking beyond the Milky Way and across cosmic history, Planck has redefined the relative proportions of the Universe’s constituent ingredients. Normal matter that makes up stars and galaxies contributes just 4.9% of the mass/energy density of the Universe.

Dark matter, to date detected only indirectly by its gravitational influence on galaxies and galaxy clusters, is found to make up 26.8%, more than previous estimates. Conversely, dark energy, a mysterious force thought to be responsible for accelerating the expansion of the Universe, accounts for 68.3%, less than previously thought.

The data also provided a new value for the age of the Universe: 13.8 billion years.

Clues to the evolution of cosmic matter

During these 13.8 billion years, light from the Big Bang crossing the Universe towards the Earth has encountered and interacted with cosmic structures that have formed since. One type of interaction results in gravitational lensing, the bending of light by massive objects like galaxy clusters.

Just as light rays passing through a glass lens are bent and distort the image behind it, so the deflected CMB photons result in additional tiny distortions in the background CMB pattern. Astronomers were able to extract a map of this gravitational lensing effect covering the whole sky for the first time from the Planck data, providing a new way to probe the evolution of structure in the Universe over time.

Deflecting light from the Big Bang

Additional insight into the formation of cosmic matter is also provided when the CMB photons encounter hot gas permeating galaxy clusters: the energy of the photons are modified in a characteristic way that allows scientists to identify galaxy clusters in detailed multicolour measurements of the CMB.

Furthermore, this effect provides a way to detect faint filaments of gas that might connect one cluster to another.

In the early Universe, filaments of gaseous matter pervaded the cosmos in a giant web, with clusters eventually forming at the densest nodes. Much of this tenuous, filamentary gas remains undetected, but cosmologists expect that it could be found between interacting galaxy clusters, where the filaments are compressed and heated up, making them easier to spot.

Coming soon

While the focus of the mission’s results has until now been on creating the most precise map of the CMB, Planck cosmologists are working hard to look even further back in time, to extract the details of the very first moments of the Universe’s existence. Less than a billionth of a billionth of a billionth of a second after it began, the Universe is thought to have undergone a rapid expansion called inflation.

Scientists believe that during inflation, quantum fluctuations should have created a sea of so-called gravitational waves, which would be imprinted in a component of the CMB that is polarised – like the light we can see using polarised glasses.

Planck all-sky frequency maps

Finding such a signal in the CMB would provide confirmation of the inflation scenario, but in order to do this, cosmologists must complete an even more accurate removal of complex foreground contaminations that include polarised emission from our own Galaxy.

“We could not be more satisfied with Planck’s performance and the results that it has achieved so far, but we are also eager to see what the polarisation data will tell us – next year will definitely be exciting for Planck,” adds Dr Tauber.

More information:

On 21 October, Planck will burn the last of its fuel to ensure its long-term stable parking orbit is maintained. On 23 October, the spacecraft will finally be switched off. News stories will be published on the ESA Portal on both occasions.

Read a more in-depth account of Planck’s key science highlights on ESA’s Science & Technology website on the following themes:

Planck's cosmology: http://sci.esa.int/planck/53103

Cosmic structure: http://sci.esa.int/planck/53104

Through the Milky Way: http://sci.esa.int/planck/53105

Images, Video, Text, Credits: ESA and the Planck Collaboration - D. Ducros.

Greetings, Orbiter.ch

jeudi 17 octobre 2013

Preps for Cygnus Departure Marks Start of High-Traffic Season on Station












ISS - Expedition 37 Mission patch.

Oct. 17, 2013

International Space Station

The Expedition 37 crew aboard the International Space Station focused Thursday on preparations for the upcoming departure of two cargo ships.  The robotic unberthing of Orbital Sciences’  Cygnus resupply ship on Tuesday will mark the start of several weeks of unusually busy vehicle traffic at the orbiting complex.

Flight Engineers Luca Parmitano and Karen Nyberg spent much of their day in space conducting a round of on-board training to review the procedures for using the station’s robotic arm to detach Cygnus from the Earth-facing port of the Harmony node on Tuesday and release it for a destructive re-entry in the Earth’s atmosphere.  The two astronauts used the arm to capture Cygnus back on Sept. 29 when it delivered around 1,300 pounds of cargo during this inaugural demonstration flight.


Image above: Attached to the Harmony node, the first Cygnus commercial cargo spacecraft built by Orbital Sciences Corp., in the grasp of the Canadarm2, is photographed by an Expedition 37 crew member on the International Space Station.

With Cygnus’ cargo of crew supplies and experiments having been fully unloaded, Nyberg and Flight Engineer Mike Hopkins spent some time Thursday refilling it with trash and other unneeded items for disposal.

Meanwhile, Flight Engineer Oleg Kotov installed and connected a control panel to monitor the departure of the European Space Agency’s Automated Transfer Vehicle-4 (ATV-4), which is set to undock from the aft port of the Zvezda service module on Oct. 28 after more than four months at the station.  Like Cygnus, the ATV-4 will be de-orbited for a fiery demise over the Pacific Ocean.

The departure of ATV-4 will clear the way for Nyberg, Parmitano and Commander Fyodor Yurchikhin to relocate their Soyuz 35 from its docking port on the Rassvet module to the newly vacated Zvezda port on Nov. 1.

Less than a week later on Nov. 7, three new station crew members -- NASA astronaut Rick Mastracchio, Japan Aerospace Exploration Agency astronaut Koichi Wakata and Soyuz commander Mikhail Tyurin of the Russian Federal Space Agency – will launch aboard their Soyuz 37 spacecraft from the Baikonur Cosmodrome and dock to Rassvet about six hours later. 


Image above: Flight Engineer Karen Nyberg enters data into a computer near the Microgravity Science Glovebox in the Destiny laboratory of the International Space Station.

For four days, nine astronauts and cosmonauts will live and work together aboard the station before Yurchikhin, Nyberg and Parmitano make their final farewells and board their Soyuz for the return to Earth after more than five months in space.  Their departure will mark the end of Expedition 37 and the beginning of Expedition 38 under the command of Kotov.

The Expedition 37 crew members also tackled a number of scientific experiments Thursday, continuing their support of station research as they had throughout the recent U.S. government shutdown.

Hopkins performed an ultrasound on Nyberg for the Spinal Ultrasound investigation. Medical researchers have observed that astronauts grow up to three percent taller during their long duration missions aboard the station and return to their normal height when back on Earth. The Spinal Ultrasound investigation seeks to understand the mechanism and impact of this change while advancing medical imaging technology by testing a smaller and more portable ultrasound device aboard the station.

Read more about Spinal Ultrasound: http://www.nasa.gov/mission_pages/station/research/experiments/944.html

Station Spinal Ultrasounds Seeking Why Astronauts Grow Taller in Space: http://www.nasa.gov/mission_pages/station/research/news/spinal_ultrasound.html

Images, Text, Credit: NASA.

Best regards, Orbiter.ch

NASA's Hubble Sees Comet ISON Intact











NASA - Hubble Space Telescope patch.

Oct. 17, 2013


A new image of the sunward plunging comet ISON suggests that the comet is intact despite some predictions that the fragile icy nucleus might disintegrate as the sun warms it. The comet will pass closest to the sun on Nov. 28.

In this NASA Hubble Space Telescope image taken on Oct. 9, the comet's solid nucleus is unresolved because it is so small. If the nucleus broke apart then Hubble would have likely seen evidence for multiple fragments.

Moreover, the coma or head surrounding the comet's nucleus is symmetric and smooth. This would probably not be the case if clusters of smaller fragments were flying along. What's more, a polar jet of dust first seen in Hubble images taken in April is no longer visible and may have turned off.

This color composite image was assembled using two filters. The comet's coma appears cyan, a greenish-blue color due to gas, while the tail is reddish due to dust streaming off the nucleus. The tail forms as dust particles are pushed away from the nucleus by the pressure of sunlight. The comet was inside Mars’ orbit and 177 million miles from Earth when photographed. Comet ISON is predicted to make its closest approach to Earth on Dec. 26, at a distance of 39.9 million miles.

The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA's Goddard Space Flight Center in Greenbelt, Md., manages the telescope. STScI conducts Hubble science operations. STScI is operated by the Association of Universities for Research in Astronomy, Inc., in Washington, D.C.

For images and more information about comet ISON, visit:

http://hubblesite.org/news/2013/42
http://heritage.stsci.edu/2013/42
http://hubblesite.org/go/ison
http://www.flickr.com/groups/comet_ison
http://www.nasa.gov/cometison

Image, Text, Credits: NASA, ESA, and the Hubble Heritage Team (STScI/AURA).

Greetings, Orbiter.ch

Rings, Dark Side of Saturn Glow in New Cassini Image












NASA / ESA - Cassini Mission to Saturn patch.

Oct. 17, 2013


Image above: This colorized mosaic from NASA's Cassini mission shows an infrared view of the Saturn system, backlit by the sun, from July 19, 2013. Image Credit: NASA/JPL-Caltech/University of Arizona/Cornell.

Story Highlights:

- The Cassini spacecraft scanned across Saturn and its rings when the sun was behind the planet and faint rings were easier to detect.

- This latest infrared image shows a strip about 340,000 miles (540,000 kilometers) across that includes the planet and its rings out to Saturn's second most distant ring.

The gauzy rings of Saturn and the dark side of the planet glow in newly released infrared images obtained by NASA's Cassini spacecraft.

"Looking at the Saturn system when it is backlit by the sun gives scientists a kind of inside-out view of Saturn that we don't normally see," said Matt Hedman, a participating scientist based at the University of Idaho, Moscow, Idaho. "The parts of Saturn's rings that are bright when you look at them from backyard telescopes on Earth are dark, and other parts that are typically dark glow brightly in this view."

It can be difficult for scientists to get a good look at the faint outer F, E and G rings, or the tenuous inner ring known as the D ring when light is shining directly on them. That’s because they are almost transparent and composed of small particles that do not reflect light well. What's different about this viewing geometry?

- When these small particles are lit from behind, they show up like fog in the headlights of an oncoming vehicle.

- The C ring also appears relatively bright here; not because it is made of dust, but because the material in it -- mostly dirty water ice -- is translucent. In fact, in the 18th and 19th centuries, it was known as the "crepe ring" because of its supposed similarity to crepe paper.

- The wide, middle ring known as the B ring -- one of the easiest to see from Earth through telescopes because it is densely packed with chunks of bright water ice -- looks dark in these images because it is so thick that it blocks almost all of the sunlight shining behind it.

Infrared images also show thermal, or heat, radiation. While a visible-light image from this vantage point would simply show the face of the planet as dimly lit by sunlight reflected off the rings, Saturn glows brightly in this view because of heat from Saturn's interior.

(click on the image for enlarge)

Image above: This high-contrast, colorized mosaic from NASA's Cassini mission shows an infrared view of the Saturn system, backlit by the sun, from July 19, 2013. Image Credit: NASA/JPL-Caltech/University of Arizona/Cornell.

In a second version of the image, scientists "stretched" or exaggerated the contrast of the data, which brings out subtleties not initially visible.

- Structures in the wispy E ring -- made from the icy breath of the moon Enceladus -- reveal themselves in this exaggerated view.

"We're busy working on analyzing the infrared data from this special view of the Saturn system," said Phil Nicholson, a visual and infrared mapping spectrometer team member from Cornell University, Ithaca, N.Y. "The infrared data should tell us more about the sizes of the particles which make up the D, E, F and G rings, and how these sizes vary with location in the rings, as well as providing clues as to their chemical composition."

Launched in 1997, Cassini has been exploring the Saturn system for more than nine years with a suite of instruments that also includes visible-light cameras, ultraviolet and infrared spectrometers, as well as magnetic field and charged particle sensors. Scientists working with the visible light cameras are still busy putting together and analyzing their mosaic -- or multi-image picture -- of the Saturn system.

Artist's view of the Cassini spacecraft. Image credit: NASA / ESA

"Cassini's long-term residency at the ringed planet means we've been able to observe change over nearly half a Saturn-year (one Saturn-year is equal to almost 30 Earth-years) with a host of different tools," said Linda Spilker, Cassini project scientist, based at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "Earth looks different from season to season and Saturn does, too. We can't wait to see how those seasonal changes affect the dance of icy particles as we continue to observe in Saturn's rings with all of Cassini's different 'eyes.'"

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL manages the mission for NASA's Science Mission Directorate, Washington. The California Institute of Technology in Pasadena manages JPL for NASA. The VIMS team is based at the University of Arizona in Tucson.

For more information about the Cassini mission, visit: http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov and http://www.esa.int/Our_Activities/Space_Science/Cassini-Huygens

Images (mentioned), Text, Credits: NASA.

Cheers, Orbiter.ch

Most distant gravitational lens helps weigh galaxies












ESA - Hubble Space Telescope logo.

17 October 2013

 The most distant gravitational lens yet discovered

An international team of astronomers has found the most distant gravitational lens yet — a galaxy that, as predicted by Albert Einstein’s general theory of relativity, deflects and intensifies the light of an even more distant object. The discovery provides a rare opportunity to directly measure the mass of a distant galaxy. But it also poses a mystery: lenses of this kind should be exceedingly rare. Given this and other recent finds, astronomers either have been phenomenally lucky — or, more likely, they have underestimated substantially the number of small, very young galaxies in the early Universe.

Light is affected by gravity, and light passing a distant galaxy will be deflected as a result. Since the first find in 1979, numerous such gravitational lenses have been discovered. In addition to providing tests of Einstein's theory of general relativity, gravitational lenses have proved to be valuable tools. Notably, one can determine the mass of the matter that is bending the light — including the mass of the still-enigmatic dark matter, which does not emit or absorb light and can only be detected via its gravitational effects. The lens also magnifies the background light source, acting as a "natural telescope" that allows astronomers a more detailed look at distant galaxies than is normally possible.

Gravitational lenses consist of two objects: one is further away and supplies the light, and the other, the lensing mass or gravitational lens, which sits between us and the distant light source, and whose gravity deflects the light. When the observer, the lens, and the distant light source are precisely aligned, the observer sees an Einstein ring: a perfect circle of light that is the projected and greatly magnified image of the distant light source.

Now, astronomers have found the most distant gravitational lens yet. Lead author Arjen van der Wel (Max Planck Institute for Astronomy, Heidelberg, Germany) explains: "The discovery was completely by chance. I had been reviewing observations from an earlier project when I noticed a galaxy that was decidedly odd. It looked like an extremely young galaxy, but it seemed to be at a much larger distance than expected. It shouldn't even have been part of our observing programme!”

Van der Wel wanted to find out more and started to study images taken with the Hubble Space Telescope as part of the CANDELS and COSMOS surveys. In these pictures the mystery object looked like an old galaxy, a plausible target for the original observing programme, but with some irregular features which, he suspected, meant that he was looking at a gravitational lens. Combining the available images and removing the haze of the lensing galaxy's collection of stars, the result was very clear: an almost perfect Einstein ring, indicating a gravitational lens with very precise alignment of the lens and the background light source [1].

The lensing mass is so distant that the light, after deflection, has travelled 9.4 billion years to reach us [2]. Not only is this a new record, the object also serves an important purpose: the amount of distortion caused by the lensing galaxy allows a direct measurement of its mass. This provides an independent test for astronomers' usual methods of estimating distant galaxy masses — which rely on extrapolation from their nearby cousins. Fortunately for astronomers, their usual methods pass the test.

Artist's view of Hubble Space Telescope

But the discovery also poses a puzzle. Gravitational lenses are the result of a chance alignment. In this case, the alignment is very precise. To make matters worse, the magnified object is a starbursting dwarf galaxy: a comparatively light galaxy (it has only about 100 million solar masses in the form of stars [3]), but extremely young (about 10-40 million years old) and producing new stars at an enormous rate. The chances that such a peculiar galaxy would be gravitationally lensed is very small. Yet this is the second starbursting dwarf galaxy that has been found to be lensed. Either astronomers have been phenomenally lucky, or starbursting dwarf galaxies are much more common than previously thought, forcing astronomers to re-think their models of galaxy evolution.

Van der Wel concludes: "This has been a weird and interesting discovery. It was a completely serendipitous find, but it has the potential to start a new chapter in our description of galaxy evolution in the early Universe."

Notes:

[1] The two objects are aligned to better than 0.01 arcseconds — equivalent to a one millimetre separation at a distance of 20 kilometres.

[2] This time corresponds to a redshift z = 1.53. This can be compared with the total age of the Universe of 13.8 billion years. The previous record holder was found thirty years ago, and it took less than 8 billion years for its light to reach us (a redshift of about 1.0).

[3] For comparison, the Milky Way is a large spiral galaxy with at least one thousand times greater mass in the form of stars than this dwarf galaxy.

Notes for editors:

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

The work described here has been published as van der Wel et al., "Discovery of a quadruple lens in CANDELS with a record lens redshift z = 1.53" , in Astrophysical Journal Letters.

The team is composed of Arjen van der Wel, Glenn van de Ven, Michael Maseda, Hans-Walter Rix (all Max Planck Institute for Astronomy, Heidelberg, Germany [MPIA]), Gregory Rudnick (University of Kansas, USA; MPIA), Andrea Grazian (INAF), Steven Finkelstein (University of Texas at Austin, USA), David Koo, Sandra M. Faber (both University of California, Santa Cruz, USA), Henry Ferguson, Anton Koekemoer, Norman Grogin (all STScI, Baltimore, USA) and Dale Kocevski (University of Kentucky, USA).

Links:

Research paper: http://www.spacetelescope.org/static/archives/releases/science_papers/heic1319a.pdf

Images of Hubble: http://www.spacetelescope.org/images/archive/category/spacecraft/

Images, Text, Credits: NASA / ESA / A. van der Wel.

Greetings, Orbiter.ch

mercredi 16 octobre 2013

ALMA Probes Mysteries of Jets from Giant Black Holes












ESO - European Southern Observatory logo.

16 October 2013

 Composite view of the galaxy NGC 1433 from ALMA and Hubble

Two international teams of astronomers have used the power of the Atacama Large Millimeter/submillimeter Array (ALMA) to focus on jets from the huge black holes at the centres of galaxies and observe how they affect their surroundings. They have respectively obtained the best view yet of the molecular gas around a nearby, quiet black hole and caught an unexpected glimpse of the base of a powerful jet close to a distant black hole.

The distant active galaxy PKS 1830-211 from Hubble and ALMA

There are supermassive black holes — with masses up to several billion solar masses — at the hearts of almost all galaxies in the Universe, including our own galaxy, the Milky Way. In the remote past, these bizarre objects were very active, swallowing enormous quantities of matter from their surroundings, shining with dazzling brilliance, and expelling tiny fractions of this matter through extremely powerful jets. In the current Universe, most supermassive black holes are much less active than they were in their youth, but the interplay between jets and their surroundings is still shaping galaxy evolution.

The nearby active galaxy NGC 1433 from ALMA and Hubble

Two new studies, both published today in the journal Astronomy & Astrophysics, used ALMA to probe black hole jets at very different scales: a nearby and relatively quiet black hole in the galaxy NGC 1433 and a very distant and active object called PKS 1830-211.

ALMA view of molecular gas in the centre of NGC1433

"ALMA has revealed a surprising spiral structure in the molecular gas close to the centre of NGC 1433," says Françoise Combes (Observatoire de Paris, France), who is the lead author of the first paper. "This explains how the material is flowing in to fuel the black hole. With the sharp new observations from ALMA, we have discovered a jet of material flowing away from the black hole, extending for only 150 light-years. This is the smallest such molecular outflow ever observed in an external galaxy."

Wide-field view of the galaxy NGC1433

The discovery of this outflow, which is being dragged along by the jet from the central black hole, shows how such jets can stop star formation and regulate the growth of the central bulges of galaxies [1].

In PKS 1830-211, Ivan Martí-Vidal (Chalmers University of Technology, Onsala Space Observatory, Onsala, Sweden) and his team also observed a supermassive black hole with a jet, but a much brighter and more active one in the early Universe [2]. It is unusual because its brilliant light passes a massive intervening galaxy on its way to Earth, and is split into two images by gravitational lensing [3].

Wide-field view of the sky around the distant active galaxy PKS 1830-211

From time to time, supermassive black holes suddenly swallow a huge amount of mass [4], which increases the power of the jet and boosts the radiation up to the very highest energies. And now ALMA has, by chance, caught one of these events as it happens in PKS 1830-211.

video
Zooming in on the active galaxy NGC 1433

"The ALMA observation of this case of black hole indigestion has been completely serendipitous. We were observing PKS 1830-211 for another purpose, and then we spotted subtle changes of colour and intensity among the images of the gravitational lens. A very careful look at this unexpected behaviour led us to the conclusion that we were observing, just by a very lucky chance, right at the time when fresh new matter entered into the jet base of the black hole," says Sebastien Muller, a co-author of the second paper.

video
Zooming in on the distant active galaxy PKS 1830-211

The team also looked to see whether this violent event had been picked up with other telescopes and were surprised to find a very clear signal in gamma rays, thanks to monitoring observations with NASA's Fermi Gamma-ray Space Telescope. The process that caused the increase of radiation at ALMA’s long wavelengths was also responsible of boosting the light in the jet dramatically, up to the highest energies in the Universe [5].

"This is the first time that such a clear connection between gamma rays and submillimetre radio waves has been established as coming from the real base of a black hole's jet," adds Sebastien Muller.

video

Video above: Artist’s impression of ALMA observations of a gravitationally-lensed supermassive black hole.

The two new observations are just the start of ALMA's investigations into the workings of jets from supermassive black holes, near and far. Combes’s team is already studying other nearby active galaxies with ALMA and the unique object PKS 1830-211 is expected to be the focus of much future research with ALMA and other telescopes.

"There is still a lot to be learned about how black holes can create these huge energetic jets of matter and radiation," concludes Ivan Martí-Vidal. “But the new results, obtained even before ALMA was completed, show that it is a uniquely powerful tool for probing these jets — and the discoveries are just beginning!"

Notes:

[1] This process, called feedback, may explain the mysterious relationship between the mass of a black hole at the centre of a galaxy and the mass of the surrounding bulge. The black hole accretes gas and grows more active, but then produces jets that clear out gas from the surrounding regions and stop star formation.

[2] PKS 1830-211 has a redshift of 2.5, meaning that its light had to travel for about 11 billion years before reaching us. The light we see was emitted when the Universe was just 20% of its current age. By comparison the light from NGC 1433 takes only about 30 million years to reach the Earth, a very short time in galactic terms.

[3] Einstein’s theory of general relativity predicts that light rays will be deflected as they pass a massive object such as a galaxy. This effect is called gravitational lensing and, since the first find in 1979, numerous such gravitational lenses have been discovered. The lensing can create multiple images as well as distort and magnify the background light sources.

[4] The infalling material could be a star or a molecular cloud. Such an infalling cloud has been observed at the centre of the Milky Way (eso1151, eso1332).

[5] This energy is emitted as gamma rays, the shortest wavelength and highest energy form of electromagnetic radiation.

More information:

The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of Europe, North America and East Asia in cooperation with the Republic of Chile. ALMA is funded in Europe by the European Southern Observatory (ESO), in North America by the U.S. National Science Foundation (NSF) in cooperation with the National Research Council of Canada (NRC) and the National Science Council of Taiwan (NSC) and in East Asia by the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Academia Sinica (AS) in Taiwan. ALMA construction and operations are led on behalf of Europe by ESO, on behalf of North America by the National Radio Astronomy Observatory (NRAO), which is managed by Associated Universities, Inc. (AUI) and on behalf of East Asia by the National Astronomical Observatory of Japan (NAOJ). The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

These research projects are presented in two papers, “ALMA observations of feeding and feedback in nearby Seyfert galaxies: an AGN-driven outflow in NGC1433”, by F. Combes et al. and “Probing the jet base of the blazar PKS 1830−211 from the chromatic variability of its lensed images: Serendipitous ALMA observations of a strong gamma-ray flare”, by I. Martí-Vidal et al. Both papers are appeared in the journal Astronomy & Astrophysics.

The first team is composed of F. Combes (Observatoire de Paris, France), S. García-Burillo (Observatorio de Madrid, Spain), V. Casasola (INAF–Istituto di Radioastronomia, Bologna, Italy), L. Hunt (INAF–Osservatorio Astrofisico di Arcetri, Florence, Italy), M. Krips (IRAM, Saint Martin d’Hère, France), A. J. Baker (Rutgers, the State University of New Jersey, Piscataway, USA), F. Boone (CNRS, IRAP, Toulouse, France), A. Eckart (Universität zu Köln, Germany), I. Marquez (Instituto de Astrofísica de Andalucía, Granada, Spain), R. Neri (IRAM), E. Schinnerer (Max-Planck-Institut für Astronomie, Heidelberg, Germany) and L. J. Tacconi (Max-Planck-Institut für extraterrestrische Physik, Garching bei München, Germany).

The second team is composed of I. Martí-Vidal (Chalmers University of Technology, Onsala Space Observatory, Onsala, Sweden), S. Muller (Onsala), F. Combes (Observatoire de Paris, France), S. Aalto (Onsala), A. Beelen (Institut d’Astrophysique Spatiale, Université Paris-Sud, France), J. Darling (University of Colorado, Boulder, USA), M. Guélin (IRAM, Saint Martin d’Hère, France; Ecole Normale Supérieure/LERMA, Paris, France), C. Henkel (Max-Planck-Institut für Radioastronomie [MPIfR], Bonn, Germany; King Abdulaziz University, Jeddah, Saudi Arabia), C. Horellou (Onsala), J. M. Marcaide (Universitat de València, Spain), S. Martín (ESO, Santiago, Chile), K. M. Menten (MPIfR), Dinh-V-Trung (Vietnam Academy of Science and Technology, Hanoi, Vietnam) and M. Zwaan (ESO, Garching, Germany).

ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. 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 the 39-metre European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become "the world’s biggest eye on the sky".

Links:

Research papers: Combes et al. & Marti-Vidal et al.: http://www.eso.org/public/archives/releases/sciencepapers/eso1344/eso1344a.pdf and http://www.eso.org/public/archives/releases/sciencepapers/eso1344/eso1344b.pdf

Video showing cosmic indigestion in the remote supermassive black hole PKS 1830-211, as seen by ALMA: http://www.nordic-alma.se/other/multimedia/48-cosmic-indigestion

Photos of the ALMA array: http://www.eso.org/public/images/archive/category/alma/

Images, Text, Credits: ALMA (ESO/NAOJ/NRAO)/NASA/ESA/F. Combes/I. Martí-Vidal/Digitized Sky Survey 2. Acknowledgement: Davide De Martin/Videos: ALMA (ESO/NAOJ/NRAO)/F. Combes/I. Martí-Vidal//MERLIN (University of Manchester, Jodrell Bank Observatory, STFC).

Best regards, Orbiter.ch

mardi 15 octobre 2013

The active Sun boosts Titan's outer atmosphere










International Cassini Mission patch.

15 October 2013

The NASA-ESA-ASI Cassini spacecraft has been observing the Saturn system, including the giant satellite Titan, for more than 9 years. A detailed analysis of Cassini data has now confirmed predictions that the density of Titan's ionosphere is directly linked to the 11 year cycle of solar activity.

All planets and satellites with atmospheres possess an ionosphere, a region in the upper atmosphere which is dominated by ionised (electrically charged) particles – electrons and ions. These ionospheres are formed mainly from the photoionisation of the atmosphere, which occurs when solar X-rays and extreme ultraviolet (EUV) radiation split atmospheric molecules into ions and electrons. As a result, the density of the ionosphere peaks above the planet's day hemisphere and is much lower above the night side.

The existence of an ionosphere high above the surface of planet-sized Titan has been known since it was first observed by radio occultation measurements from the Voyager 1 spacecraft in November 1980. However, most of our knowledge about the moon's ionosphere has been established following the entry of the Cassini spacecraft into orbit around Saturn in July 2004.


Image above: Sunlight scattering through the periphery of Titan's atmosphere forms a ring of colour. Credit: NASA/JPL-Caltech/Space Science Institute.

Larger than Mercury, Titan is blanketed with a dense, orange haze of organic molecules which hides the satellite's icy surface. As on Earth, the most abundant gas in the atmosphere is nitrogen. However, unlike our world, Titan's ionosphere is dominated by quite complex organic compounds, such as HCNH+ (protonated hydrogen cyanide) and C2H5+ (an ethyl group). There is also a wealth of other minor species present, formed through the chemistry in the moon's upper atmosphere.

The primary ionisation source for Titan's atmosphere is the solar EUV flux. Impacting particles trapped in Saturn's magnetosphere play a minor role in establishing the dayside ionosphere, but have a larger effect on the night side.

The structure of the ionosphere has been studied extensively during the Cassini mission. The peak density is located 1000 – 1300 km above the surface, with a decrease in altitude where the Sun is higher above the horizon. The maximum electron density is typically about 3000 particles per cubic cm on the dayside, compared with about 1000 particles per cubic cm on the night side.

The variability of Titan's ionospheric structure has also been studied since the arrival of Cassini. Remote measurements by radio occultation, as well as measurements by instruments on board Cassini, have revealed that the structure and density can vary significantly with time.


This picture (above) traces different phases of Cassini's tour of the Saturnian system. Credit: NASA/JPL-Caltech.

One of the advantages of inserting a multi-instrumented spacecraft, such as Cassini, into orbit around a planet is the long-term continuity of scientific data, enabling changes over time to be monitored and analysed.

An international team of scientists has now taken advantage of this longevity to compare the amount of ionisation at Titan during different stages of the 11 year solar cycle. The data they used were obtained by the Langmuir probe instrument, part of the radio and plasma wave science instrument on board Cassini. The Langmuir probe is used to monitor the density, temperature and bulk speed of plasma (electrons and ions) as the spacecraft orbits Saturn.

Writing in the Journal of Geophysical Research: Space Physics, the authors compare measurements obtained at the beginning of the mission, when the solar activity was at a moderate-to-low level of activity, with data from recent flybys completed at a time of fairly high solar activity.

When the measurements are corrected for the different flyby geometry and position of the overhead Sun, their analysis shows a definite correlation between the amount of ionisation in Titan's ionosphere and level of solar activity.

"We found that the varying EUV flux during the solar cycle strongly influenced the peak electron density of Titan's ionosphere," said Niklas Edberg, a post-doctoral researcher at the Swedish Institute of Space Physics in Uppsala, Sweden, and lead author of the paper.


Image above: A natural colour view of Saturn's moon Titan. Credit: NASA/JPL-Caltech/Space Science Institute.

"From the first Titan flyby of the Cassini mission on 26 October 2004 until T71 (the 72nd close pass of Titan) on 7 July 2010, it was not possible to identify any large changes in the structure of the ionosphere in response to either solar cycle changes or seasonal changes in Titan's atmosphere," said Edberg.

"However, after 2010, solar activity picked up rapidly and our analysis showed that, during six Titan flybys between May 2012 and November 2012, the electron density in the ionospheric peak region, as measured by the Langmuir probe on Cassini, increased by 15-30%, compared to the previous average."

This marked increase in the density of the ionosphere coincided with increasing solar activity, even though Titan received a smaller percentage of incoming solar radiation due to Saturn's elliptical orbit and increasing distance from the Sun. During 2004 - 2012, Saturn moved outward from the Sun by more than 100 million km.

"The ionospheric peak electron densities during the more recent Titan flybys are significantly increased compared to measurements from previous flybys, and the peaks are generally also found at lower altitudes in the ionosphere than previous average values," said Edberg.

Cassini spacecraft. Credit: NASA/ESA/JPL-Caltech

The teams' results are in very good agreement with existing theory, which predicts that the production rate of ions and electrons should be proportional to the square root of the ionising flux increase.

It is interesting to note that most of the Cassini measurements of Titan's ionosphere have occurred during a very special era - the deepest solar minimum since the seventeenth century. As a result, the peak densities measured as the current solar cycle heads towards maximum have been lower than in previous cycles.

Theoretical calculations show that ionospheric peak electron density during periods of higher solar activity should exceed 6500 particles per cubic cm at the subsolar point. This is 85 - 160% more than what has been observed by Cassini as that latest solar cycle reaches its peak.

"Nearly the same mechanisms exist at Earth, where the possible long-term effects of solar cycles on Earth's climate evolution are debated," said Nicolas Altobelli, ESA's Cassini project scientist.

"Titan is often referred to as a primitive Earth in deep freeze, so it is fascinating to compare the physical processes taking place in the upper atmospheres of these two worlds."

Background information:

The results described in this article are reported in "Solar cycle modulation of Titan's ionosphere", by N. J. T. Edberg et al , published in the Journal of Geophysical Research: Space Physics, Volume 118, Issue 8, pages 5255-5264, August 2013; doi:10.1002/jgra.50463

The Cassini–Huygens mission is a cooperative project of NASA, ESA and the Italian Space Agency (ASI). Launched in 1997, Cassini arrived in the Saturn system in 2004 and is studying the ringed planet and its moons. The Huygens probe was released from the main spacecraft and, in 2005, parachuted through the atmosphere to the surface of Saturn's largest moon, Titan.

NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C.

For information about Cassini, visit: http://www.nasa.gov/cassini and http://www.esa.int/esaMI/Cassini-Huygens/

Images (mentioned), Text, Credits: ESA Cassini-Huygens Project Scientist / Nicolas Altobelli / Swedish Institute of Space Physics / N. J. T. Edberg.

Greetings, Orbiter.ch

lundi 14 octobre 2013

Galactic bubble










ESA - Herschel Exploring the Cold Universe patch.

14 October 2013

 The Galactic bubble RCW 120

Nestled within the shell around this large bubble is an embryonic star that is already a hefty eight times more massive than our Sun. 

This image, by ESA’s Herschel space observatory, was originally presented in the first announcement of scientific results  from the mission in May 2010: http://www.esa.int/Our_Activities/Space_Science/Herschel_reveals_the_hidden_side_of_star_birth

This week Herschel scientists will meet again at ESA’s ESTEC establishment in the Netherlands to present, discuss, and take stock of the scientific breakthroughs of the entire mission at The Universe Explored by Herschel symposium.

The Galactic bubble shown in this image was just one of many surprising results of the mission.

It is about 4300 light-years away and has been blown by a star at its centre. The star is not visible at these infrared wavelengths but pushes on the surrounding dust and gas with nothing more than the power of its starlight.

The pressure exerted on the surrounding material is such that it has begun collapsing into new stars.

The bright knot to the right of the base of the bubble is an unexpectedly large, embryonic star, revealed to Herschel’s infrared detectors by heating up the surrounding dense clumps of gas and dust.

ESA’s Herschel space observatory

Herschel’s observations have shown that it already contains at least eight times the mass of our Sun, and that it is still surrounded by an additional 2000 solar masses of gas and dust from which it can feed further.

Not all of the material will fall onto the star, however, as some will be blasted away by the intense radiation emitted by the star. Some stars reach an impressive 150 solar masses, but just how large this stellar embryo will grow remains to be seen.

This week, scientists will not only discuss star formation, but also what the Herschel space observatory has revealed about planetary system evolution, galaxy formation, the interstellar medium and more. A full programme can be found here: http://congrexprojects.com/2013-events/13a12/introduction

Herschel was launched on 14 May 2009 and completed science observations on 29 April 2013.

Related kinks:

Herschel: ESA's giant infrared observatory: http://www.esa.int/Our_Activities/Space_Science/Herschel

Herschel overview: http://www.esa.int/Our_Activities/Space_Science/Herschel_overview

Herschel Science Centre: http://herschel.esac.esa.int/

Images, Text, Credits: ESA / PACS / SPIRE / HOBYS Consortia.

Best regards, Orbiter.ch