Posted on by Fraser Cain

Infrared Ring Around a Young Star

Image credit: ESO

A new image taken by the European Southern Observatory’s Very Large Telescope (VLT) shows an infrared halo around a nascent star. The image also shows jets of gas emanating from the region and colliding with the surrounding cloud. Although these rings have been theorized before, this is the first time one has actually been seen. The dust in the surrounding cloud is collapsing under its own gravity and will eventually form a true star.

A small and dark interstellar cloud with the rather cryptic name of DC303.8-14.2 is located in the inner part of the Milky Way galaxy. It is seen in the southern constellation Chamaeleon and consists of dust and gas. Astronomers classify it as a typical example of a “globule”.

As many other globules, this cloud is also giving birth to a star. Some years ago, observations in the infrared spectral region with the ESA IRAS satellite observatory detected the signature of a nascent star at its centre. Subsequent observations with the Swedish ESO Submillimetre Telescope (SEST) at La Silla (Chile) were carried out by Finnish astronomer Kimmo Lehtinen. He revealed that DC303.8-14.2 is collapsing under its own gravity, a process which will ultimately result in the birth of a new star from the gas and dust in this cloud.

Additional SEST observations of the millimetre emission of carbon monoxide (CO) molecules demonstrated a strong outflow from the nascent star. A small part of the gas that falls inward onto the central object is re-injected into the surrounding via this outward-bound “bipolar stream”.

The structure of DC303.8-14.2
The left panel in PR Photo 26a/03 shows the DC303.8-14.2 globule as it looks in red light. This image was obtained at wavelength 700 nm and has been reproduced from the Digitized Sky Survey (DSS) [1]. It covers a sky region of 20 x 20 arcmin2, or about 50% of the area of the full moon. The dust particles in the cloud reflect the light from stars, causing the cloud to appear brighter than the adjacent sky.

The brightness distribution over the cloud depends mostly on three factors connected to the dust. The first is the distribution of dust grains in the cloud, the way the dust density changes with the distance from the centre of the cloud. The second is the relative amount of light that is reflected by the dust particles. The third indicates the dominant direction in which the dust particles scatter light; this is dependent on the geometry of the grains and their preferred spatial alignment. Accurate observations of the brightness distribution over the surface of a globule allow an investigation of these properties and thus to learn more about the structure and composition of the cloud.

From the image obtained in red light (left panel in PR Photo 26a/03) it appears, somewhat surprisingly, that the brightest area of DC303.8-14.2 is not where there is most dust. Instead, it takes the form of a bright ring around the centre. This rim corresponds to a region where the intensity of the light from stars behind the cloud is reduced by a moderate factor of 3 to 5 when passing through the cloud and where the light-scattering efficiency of the dust grains in the cloud is the highest.

Observing with ISAAC on the VLT
In order to study the structure of DC303.8-14.2 in more detail, Kimmo Lehtinen and his team of Finnish and Danish astronomers [2] used the near-infrared imaging capabilities of the ISAAC multi-mode instrument on the 8.2-m VLT ANTU telescope at the ESO Paranal Observatory (Chile). Under good observing conditions, they obtained a mosaic image of this cloud in several near-IR wavelength bands, including the J- (centered at wavelength 1.25 ?m), H- (1.65) and Ks-bands (2.17). These exposures were combined to produce images of DC303.8-14.2, two of which are shown in PR Photo 26a/03 (middle and right panels).

The middle image shows the central part of the globule in the H-band. A bright rim is clearly detected – this is the first time such a ring is seen in infrared light around a globule.

This rim has a smaller size in infrared than in visible light. This is because the absorption of infrared light by dust particles is smaller than the absorption of visible light. More dust is then needed to produce the same amount of scattering and to show a rim in infrared light. The infrared rim will therefore show up in an area where the dust density is higher, i.e. closer to the centre of the cloud, than the visible-light rim.

Similar rings were also detected in the J- and Ks-band images and, as expected, of different sizes. Thus the mere observation of the size (and shape) of a bright rim already provides information about the internal structure of the cloud. In the case of DC303.8-14.2, a detailed evaluation shows that the dust density of the centre is so high that any visible light from the nascent star in there would be dimmed at least 1000 times before it emerges from the cloud.
Getting a bonus: Jets from a young star

As an unexpected and welcome bonus, the astronomers also detected several jet- and knot-like structures in the Ks-band image (right panel in PR Photo 26a/03), near the IRAS source. The area shown represents the innermost region of the cloud (65 x 50 arcsec2, or just 1/500 of the area of the DSS image to the left).

Several knot-like structures on a line like a string of beads are clearly seen. They are most probably regions where the gas ejected by the young stellar object rams into the surrounding medium, creating zones of compressed and hot molecular hydrogen. Such structures are known by astronomers as “Herbig-Haro objects”, cf. ESO PR 17/99.

More information
A general description of the methods used to study and model surface brightness observations of small dark clouds in given in a basic paper by Kimmo Lehtinen and Kalevi Mattila in the research journal Astronomy & Astrophysics (Vol. 309, p. 570 1996). The results presented here will be published in a forthcoming paper in Astronomy & Astrophysics.
Notes

[1]: The Digitized Sky Survey was produced at the Space Telescope Science Institute under U.S. Government grant NAG W-2166. The images of these surveys are based on photographic data obtained using the Oschin Schmidt Telescope on Palomar Mountain and the UK Schmidt Telescope. The plates were processed into the present compressed digital form with the permission of these institutions.

[2]: The team is composed of Kimmo Lehtinen, Kalevi Mattila from the Observatory of the University of Helsinki (Finland), Petri V?is?nen from ESO/Chile and Jens Knude from the Observatory of the University of Copenhagen (Denmark). P. V?is?nen is also affiliated with the University of Helsinki.

Original Source: ESO News Release

Posted on by Fraser Cain

Satellites Measure Rising Seas

Image credit: NASA

The spectre of global warming and rising ocean levels have been a concern for many years, but NASA has some real numbers to help measure the situation. According to the Topex/Poseidon and Jason satellites, sea levels have been rising an average of 2.8 millimetres a year since observations began in 1992. Whether rising sea levels are caused by human impact or a natural cycle still isn’t clear, but the impact is already being felt in coastal communities around the world with water inundating low-level areas and an increased rate of beach erosion.

Stack two dimes on top of each other. Their height is a tiny fraction less than global sea level is rising each year. The increase looks small, but the consequences are potentially huge. Rising sea level threatens to inundate low-lying regions, such as the Chesapeake, and dramatically increase coastal and beach erosion around the world.

While tide gauges have been used to determine sea level for hundreds of years, the most complete global measurements now come from space. “Tide gauges can’t detect an increase in the rate of sea level rise soon enough to be useful for detecting climate change,” says Bruce Douglas, a senior researcher at Florida International University, Miami, Fla. “Tide gauges can’t measure everywhere. They’re on practically every rock in the ocean, the problem is there just aren’t enough rocks.”

In contrast, the Topex/Poseidon satellite observes the entire ocean and has been making precise measurements of global sea level since it was launched in 1992. Its successor, Jason, is now continuing the same ocean observations.

“Right now Topex/Poseidon has been seeing an average yearly increase of 2.8 millimeters (0.11 inches) in global sea level,” says University of Colorado engineering professor Dr. Steve Nerem, a member of the Topex/Poseidon and Jason 1 science team.

Global sea level is the average of all local rates. If global sea level is rising by 2.8 millimeters a year, the local rate in some areas is much higher, as much as 5 millimeters (0.2 inches) or more over long periods. In some areas it is less.

One of the big questions facing scientists and the public, especially the more than two billion of us who live within 100 kilometers (62 miles) of a coast, about the rise in sea level is “why?”

“We don’t know yet exactly what is causing it,” says Nerem. “The jury is still out.” The current rise in global sea level could be part of some natural, yet unidentified, decades-long climate pattern, Nerem says. “During 1997-1998 El Ni?o, the global average went up 15 millimeters (0.6 inches) as a result of increased ocean temperatures and then went down again.”

However, sea level is a barometer of climate change, and the rise could be a result of a warming Earth. “While the rate of increase we see is consistent with climate change models, we can’t say for sure if that is the cause,” Nerem says. “We’re just starting to ask those questions.”

“It looks like sea level rise as we now observe it began in the middle of the 19th century,” says Douglas, an expert on the history of sea level rise and its consequences. “We have a preponderance of evidence that the current rate is considerably faster than for the previous several thousand years, although there is still some disagreement among scientists about this.”

The two major factors that determine sea level are temperature and ocean mass. Warm water expands and raises sea level. Water added to the ocean from melting glaciers or ice sheets also causes sea level to go up. Figuring out just how much of the current sea level rise is due to each of these factors is difficult.

“Our best guess is that thermal expansion accounts for about 0.5 millimeters (.02 inches) per year rise in sea level or five centimeters (2 inches) per 100 years,” says Douglas. “If global sea level is rising at more than 20 centimeters (8 inches) per hundred years, then where is the water coming from? Mountain glaciers could account for three or four centimeters (1.2 to 1.6 inches), so that leaves Earth’s great ice sheets in Greenland and Antarctica. Are they losing or gaining? That’s a controversial question.”

Scientists expect to have some answers soon. NASA’s new Grace mission will be able to calculate the ocean’s mass, helping pinpoint whether rising sea level is a result of more water in the ocean or expansion due to warming waters. A new generation of tide gauges and monitoring devices provide details on sea level changes in specific locations.

Meanwhile, Jason continues the global sea level measurements begun by Topex/Poseidon more than 11 years ago, building up a record of sea level change that may help explain the past and predict the future. Ironically, Topex/Poseidon was never expected to be able to make precise enough measurements to monitor something as small as millimeter changes in global sea level. “It’s a 100 times more accurate than we expected it to be before launch,” says Douglas. Jason 1 may improve on these measurements even more.

Original Source: NASA/JPL News Release

Posted on by Fraser Cain

NASA Accepts CAIB Report

NASA Administrator Sean O’Keefe officially accepted the report from the Columbia Accident Investigation Report, and vowed that serious changes would be made to the agency to reduce the risks of future shuttle flights. In fact, he said, many of the preliminary recommendations were already underway and would be ready when the shuttle returns to flight some time in Spring 2004. The board made 15 recommendations that must be fulfilled before the shuttle can return to flight, but their biggest complaint, that NASA’s fundamental culture caused allowed this disaster to take place may be the hardest to fix.

Posted on by Fraser Cain

Hubble Snaps Closest Picture of Mars

Image credit: Hubble

NASA’s Hubble Space Telescope snapped this beautiful picture of the Planet Mars when our two planets were only 56 million kilometres apart. The picture was actually assembled from a series of exposures taken between 2220-2312 GMT (6:20 – 7:12 pm EDT) – 11 hours before the moment of opposition. The picture shows many details on the planet’s surface, including impact craters, clouds, and dust storms. The next opportunity for a picture like this will be in 26 months, when our two planets are reasonably close again.

NASA’s Hubble Space Telescope snapped this portrait of Mars within minutes of the planet’s closest approach to Earth in nearly 60,000 years. This image was made from a series of exposures taken between 5:35 a.m. and 6:20 a.m. EDT Aug. 27 with Hubble’s Wide Field and Planetary Camera 2. In this picture, the red planet is 34,647,420 miles (55,757,930 km) from Earth.

This sharp, natural-color view of Mars reveals several prominent Martian features, including the largest volcano in the solar system, Olympus Mons; a system of canyons called Valles Marineris; an immense dark marking called Solis Lacus; and the southern polar ice cap.

Olympus Mons [the oval-shaped feature just above center] is the size of Arizona and three times higher than Mount Everest. The dormant volcano resides in a region called the Tharsis Bulge, which is about the size of the U.S. and home to several extinct volcanoes. The three Tharsis Montes volcanoes are lined up just below Olympus Mons. Faint clouds are hovering over Arsia Mons, the southernmost of these volcanoes.

The long, dark scar, below and to the right of the Tharsis Bulge, is Valles Marineris, a 2,480-mile (4,000-km) system of canyons. Just below Valles Marineris is Solis Lacus, also known as the “Eye of Mars.” The dark features to the left of Solis Lacus are the southern highlands, called Terra Sirenum, a region riddled with impact craters. The diameters of these craters range from 31 to 124 miles (50 to 200 km).

The image was taken during the middle of summer in the Southern Hemisphere. During this season the Sun shines continuously on the southern polar ice cap, causing the cap to shrink in size [bottom of image]. The orange streaks are indications of dust activity over the polar cap. The cap is made of carbon dioxide ice and water ice, but only carbon dioxide ice is seen in this image. The water ice is buried beneath the carbon dioxide ice. It will only be revealed when the cap recedes even more over the next two months. By contrast, the Northern Hemisphere is in the midst of winter. A wave of clouds covers the northern polar ice cap and the surrounding region [top of image].

This view of Mars reveals a striking contrast between the Northern and Southern hemispheres. The Northern Hemisphere is home to volcanoes that may have been active about 1 billion years ago. These volcanoes resurfaced the north’s landscape, perhaps filling in many impact craters. The Southern Hemisphere is pockmarked with ancient impact craters, which appear dark because many are filled with coarser sand-sized particles.

Mars and Earth make a “close encounter” about every 26 months. These periodic encounters are due to the differences in the two planets’ orbits. Earth goes around the Sun twice as fast as Mars, lapping the red planet about every two years. Both planets have elliptical orbits, so their close encounters are not always at the same distance. In its close encounter with Earth in 2001, for example, Mars was about 9 million miles farther away. Because Mars was much closer during this year’s rendezvous, the planet will appeared 23 percent larger in the sky. Mars will not be this close again until 2287.

This photograph is a color composite generated from observations taken with blue, green, and red filters. A total of 11 filters, spanning a wide wavelength range?-from blue to near infrared?-were used during the observations. The shorter wavelengths show clouds and other atmospheric changes. The longer wavelengths, including the near infrared, reveal Martian surface features.

Original Source: Hubble News Release

Posted on by Fraser Cain

Cloudless Europe Seen From Space

Image credit: ESA

As the weather is starting to cool in Europe after a particularly hot summer, the European Space Agency snapped this picture of the continent with pretty much cloudless skies. The composite image was built up from a series of pictures snapped by the ESA’s Meteosat Second Generation 1 (MSG-1). The satellite was launched almost exactly a year ago and is positioned above Europe in geostationary orbit.

As most Europeans breathe a sigh of relief as this record-breaking summer draws to a close, the extreme weather conditions experienced in recent weeks have given us a rare view of an almost cloud-free Europe, taken by Europe?s weather satellite MSG-1, launched a year ago this week.

This enhanced composite image was taken on 10 August 2003, at midday (12:00 UT) and shows a virtually cloud-free Europe. Only the UK and Finland are partially obscured by cloud. Meteosat Second Generation 1 (MSG-1) is the first of a new generation of weather satellites, developed in close cooperation between the European Space Agency (ESA) and EUMETSAT, the European Organisation for the Exploitation of Meteorological Satellites.

Built by ESA and operated by EUMETSAT, MSG-1 was launched by Ariane, a year ago on 28 August at 22:45 UT, from Europe?s spaceport in French Guiana. MSG-1 is positioned in geostationary orbit, at 10.5?W 36 000 kilometres above the Earth. This image illustrates the excellent performance of the innovative radiometer carried by MSG-1.

The MSG system will provide an essential service for weather experts for at least the next 12 years. This continuity of service is important not only to make short-term forecasts, but also to investigate global weather trends in the longer term.

Original Source: ESA News Release

Posted on by Fraser Cain

Mars Closest Tomorrow

On Wednesday, August 27 at 0951 GMT (5:51 am EDT) Mars and Earth will be only 56 million kilometres apart; the closest they’ve been in almost 60,000 years. Mars looks best in a telescope, where features like its polar ice cap and dust storms are visible, the planet is easy to spot with the naked eye. Just look to the south in the late evening and you can’t miss it; it currently outshines any other object in the sky other than the Moon. Astronomy clubs and observatories around the world are hosting events to give the public a chance to see the Red Planet – it will remain bright and close for several months.

Posted on by Fraser Cain

Columbia Accident Report Released

Image credit: CAIB

The Columbia Accident Investigation Board released its final report today, which was officially accepted by NASA Administrator Sean O’Keefe. The 250-page document contains an overview of the shuttle program in general, as well as STS-107. The report discusses the suspected cause of the Columbia accident – that foam falling from the fuel tank on liftoff smashed a hole in the shuttle’s left wing and allowed hot gas to enter during re-entry – but it also places a lot of emphasis on the weaknesses of NASA’s culture.

WASHINGTON, D.C. – The Columbia Accident Investigation Board today presented its final report on the causes of the Feb. 1, 2003 Space Shuttle accident to the White House, Congress and the National Aeronautics and Space Administration.

The CAIB report concludes that while NASA’s present Space Shuttle is not inherently unsafe, a number of mechanical fixes are required to make the Shuttle safer in the short term. The report also concludes that NASA’s management system is unsafe to manage the shuttle system beyond the short term and that the agency does not have a strong safety culture.

The Board determined that physical and organizational causes played an equal role in the Columbia accident – that the NASA organizational culture had as much to do with the accident as the foam that struck the Orbiter on ascent. The report also notes other significant factors and observations that may help prevent the next accident.

The Board crafted the report to serve as a framework for a national debate about the future of human space flight, but suggests that it is in the nation’s interest to replace the Shuttle as soon as possible as the primary means for transporting humans to and from Earth orbit.

The Board makes 29 recommendations in the 248-page final report, including 15 return-to-flight recommendations that should be implemented before the Shuttle Program returns to flight.

The report, which consists of 11 chapters grouped into three main sections, was the result of a seven-month-long investigation by the CAIB’s 13 board members, more than 120 investigators, 400 NASA and contractor employees, and more than 25,000 searchers who recovered Columbia’s debris.

Over the next several weeks, the Board expects to publish several additional volumes containing technical documents cited in the report or referenced as part of the investigation, as well as transcripts of the board’s public hearings.

The report can be viewed on our website at: www.caib.us

Please watch the NASA website for information about how to obtain hard copies or CDs of the Report.

Original Source: CAIB News Release

Posted on by Fraser Cain

NASA Releases a Map of the Whole Earth

Image credit: NASA

NASA has released a new image of the entire Earth based on images taken during the Shuttle Radar Topography Mission. The global data set greatly improves maps of the Earth’s surface between 60-degrees North and South of the equator – 80% of the globe. Previous maps of the United States have a similar resolution as the SRTM30 data – about 1 km – but the rest of the world is often inaccurate. SRTM is capable of producing even higher-resolution maps, down to 30 metres.

A brand new look and understanding of the place we call home. That’s what you’ll get in a complete global topographic data set generated by NASA and the National Imagery and Mapping Agency (NIMA).

Produced by the Shuttle Radar Topography Mission, the global data set, called “SRTM30,” greatly improves maps of Earth’s land mass located between 60 degrees north and 60 degrees south of the equator. That’s roughly from the southern tip of Greenland to below the southern tip of South America.

Until now, the primary source of digital elevation data for scientists and analysts involved in global studies has been the U.S. Geological Survey’s “GTOPO30,” published in 1996, it consists of elevation measurements spaced every 30-arc-seconds. An arc-second is a measure of latitude and longitude used by geographers that corresponds to about 30.9 meters, or 101.4 feet, at the equator. This allows identification of features roughly the size of Disneyland in California. The SRTM30 map matches the GTOPO30 resolution, but with its seamless quality, the map represents a leap in global-scale accuracy.

“SRTM30 is a powerful demonstration of the benefits which accrue from NASA’s human space flight program and satellite radar mapping technology,” said John LaBrecque, manager, Solid Earth and Natural Hazards Program, NASA Headquarters, Washington.

“The quality of previous maps of the Earth varied considerably, because they were compiled from various data gathered by generations of explorers and surveyors. In some places these maps are inaccurate. Using NASA technology, six Space Shuttle astronauts mapped 80 percent of Earth’s land surface in just 10 days to produce the first 3-D map of the Earth’s surface at a known and uniform accuracy,” he said.

The need for accurate topographic maps is everywhere from planning a hike to building a new highway. Knowing the exact shape and location of mountain peaks and river valleys is as important to the safe and efficient flight of aircraft as it is to the management of water resources and the control of forest fires.

Newly released images, representing the new SRTM30 data products, depict Earth in two ways: as an image with all the continents shown (a common map-making method known as a Mercator projection); and as three globe images of Earth as viewed from points in space centered over the Americas, Africa and the western Pacific. Two visualization methods were combined to produce the images: shading and color-coding of topographic height. The shaded image was derived by computing topographic slope in the northwest-southeast direction, so northwest slopes appear bright and southeast slopes appear dark. Color-coding depicts the lowest elevations in green, rising through yellow and tan, to white at the highest elevations.

The SRTM30 map is one of a series of land surface products emerging from the very successful Shuttle Radar Topography Mission (SRTM). SRTM has produced more detailed topographic data for North and South America that resolves features approximately 90 feet square, or 10 times the global SRTM30 database.

The SRTM data were processed at NASA’s Jet Propulsion Laboratory, Pasadena, Calif., into research-quality digital elevation data. NIMA is providing additional processing to develop official mapping products. The U.S. Geological Survey Earth Resources Observation Systems Data Center in Sioux Falls, S.D. provides final archiving and distribution of the SRTM data products.

The SRTM mission is a cooperative project of NASA, NIMA, German and Italian space agencies. The project is part of NASA’s mission to understand and protect our home planet.

The new images are available on the JPL Planetary Photojournal at:

http://photojournal.jpl.nasa.gov/catalog/PIA03394

http://photojournal.jpl.nasa.gov/catalog/PIA03395

http://photojournal.jpl.nasa.gov/catalog/PIA03396
Information about the Shuttle Radar Topography Mission is available at:

http://www.jpl.nasa.gov/srtm/

Original Source: NASA News Release

Posted on by Fraser Cain

NASA SIRTF Launches on Board a Delta II Rocket


NASA’s Space Infrared Telescope Facility (SIRTF) successfully launched on board a Delta II rocket from Florida’s Cape Canaveral Air Force Station at 0535 GMT (1:35 am EDT). The Deep Space Network station in Canberra, Australia reported the first data from the observatory 64 minutes after launch. The last of the Great Observatories, SIRTF will use infrared detectors to help expand astronomers’ knowledge of many objects in the sky, including brown dwarfs, planet-forming discs of debris around other stars, and distant galaxies. The observatory will undergo two months of testing followed by another month of science verification; after that, SIRFT will be ready for use.

NASA’s Space Infrared Telescope Facility (SIRTF) successfully launched from Florida’s Cape Canaveral Air Force Station at 1:35:39 a.m. Eastern Daylight Time (10:35:39 p.m. Pacific Daylight Time, August 24) aboard a Delta II launch vehicle.

Flying eastward over the Atlantic Ocean, the new observatory entered an Earth-trailing orbit the first of its kind at about 43 minutes after launch. Five minutes later, the spacecraft separated from the Delta?s second and final stage. At about 2:39 a.m. Eastern Daylight Time (11:39 p.m. Pacific Daylight Time, Aug. 24), about 64 minutes after take-off, the NASA Deep Space Network station in Canberra, Australia received the first data from the spacecraft.

“All systems are operating smoothly, and we couldn?t be more delighted,” said David Gallagher, project manager for the mission at NASA?s Jet Propulsion Laboratory, Pasadena, Calif.

The last of NASA?s suite of Great Observatories, the Space Infrared Telescope Facility will use infrared detectors to pierce the dusty darkness enshrouding many of the universe?s most fascinating objects, including brown dwarfs, planet-forming debris discs around stars and distant galaxies billions of light years away. Past Great Observatories include the Hubble Space Telescope, Chandra X-ray Observatory and Compton Gamma Ray Observatory.

The two-and-one-half to five-year mission is an important bridge to NASA?s Origins Program, which seeks to answer the questions: “Where did we come from? Are we alone?”

In-orbit checkout and calibration is scheduled to last 60 days, followed by a 30-day science verification period, after which the observatory is expected to begin its regular science mission.

For more information about the Space Infrared Telescope Facility, visit their Web site at http://sirtf.caltech.edu/>.

Original Source: NASA News Release

Posted on by Fraser Cain

Brazilian Rocket Explodes, at Least 20 Killed

At least 20 people were killed and more injured when a rocket exploded at the Brazilian Alcantara Launch Center. One of the VLS-3 rocket’s engines is believed to have caught on fire, triggering an explosion that caused the launch pad to collapse. The two research satellites atop the rocket were also destroyed. This disaster is just the latest in a series of setbacks which have plagued the Brazilian rocket launch program – two rockets in 1997 and 1999 had to be destroyed shortly after take off.