84 Million Stars and Counting

VISTA gigapixel mosaic of the central parts of the Milky Way

Using a whopping nine-gigapixel image from the VISTA infrared survey telescope at ESO’s Paranal Observatory, an international team of astronomers has created a catalogue of more than 84 million stars in the central parts of the Milky Way. This gigantic dataset contains more than ten times more stars than previous studies and is a major step forward for the understanding of our home galaxy. The image gives viewers an incredible, zoomable view of the central part of our galaxy. It is so large that, if printed with the resolution of a typical book, it would be 9 metres long and 7 metres tall.

Wide-field view of the Milky Way, showing the extent of a new VISTA gigapixel image

“By observing in detail the myriads of stars surrounding the centre of the Milky Way we can learn a lot more about the formation and evolution of not only our galaxy, but also spiral galaxies in general,” explains Roberto Saito (Pontificia Universidad Católica de Chile, Universidad de Valparaíso and The Milky Way Millennium Nucleus, Chile), lead author of the study.

Optical/infrared comparison of the central parts of the Milky Way

Most spiral galaxies, including our home galaxy the Milky Way, have a large concentration of ancient stars surrounding the centre that astronomers call the bulge. Understanding the formation and evolution of the Milky Way’s bulge is vital for understanding the galaxy as a whole. However, obtaining detailed observations of this region is not an easy task. “Observations of the bulge of the Milky Way are very hard because it is obscured by dust,” says Dante Minniti (Pontificia Universidad Catolica de Chile, Chile), co-author of the study. “To peer into the heart of the galaxy, we need to observe in infrared light, which is

Colour–magnitude diagram of the Galactic bulge

less affected by dust.”the The large mirror, wide field of view and very sensitive infrared detectors of ESO’s 4.1-metre Visible and Infrared Survey Telescope for Astronomy (VISTA) make it by far the best tool for this job. The team of astronomers is using data from the VISTA Variables in the Via Lactea programme (VVV) [1], one of six public surveys carried out with VISTA. The data have been used to create a monumental 108 200 by 81 500 pixel colour image containing nearly nine billion pixels. This is one of the biggest astronomical images ever produced. The team has now used these data to compile the largest catalogue of the central concentration of stars in the Milky Way ever created [2].

Annotated map of VISTA’s view of the centre of the Milky Way

To help analyse this huge catalogue the brightness of each star is plotted against its colour for about 84 million stars to create a colour–magnitude diagram. This plot contains more than ten times more stars than any previous study and it is the first time that this has been done for the entire bulge. Colour–magnitude diagrams are very valuable tools that are often used by astronomers to study the different physical properties of stars such as their temperatures, masses and ages [3]. “Each star occupies a particular spot in this diagram at any moment during its lifetime. Where it falls depends on how bright it is and how hot it is. Since the new data gives us a snapshot of all the stars in one go, we can now make a census of all the stars in this part of the Milky Way,” explains Dante Minniti. Video above: Infrared/visible light comparison of VISTA’s gigapixel view of the centre of the Milky Way. The new colour–magnitude diagram of the bulge contains a treasure trove of information about the structure and content of the Milky Way. One interesting result revealed in the new data is the large number of faint red dwarf stars. These are prime candidates around which to search for small exoplanets using the transit method [4]. “One of the other great things about the VVV survey is that it’s one of the ESO VISTA public surveys. This means that we’re making all the data publicly available through the ESO data archive, so we expect many other exciting results to come out of this great resource," concludes Roberto Saito. Notes: [1] The VISTA Variables in the Via Lactea (VVV) survey is an ESO public survey dedicated to scanning the southern plane and bulge of the Milky Way through five near-infrared filters. It started in 2010 and was granted a total of 1929 hours of observing time over a five-year period. Via Lactea is the Latin name for the Milky Way. [2] The image used in this work covers about 315 square degrees of the sky (a bit less than 1% of the entire sky) and observations were carried out using three different infrared filters. The catalogue lists the positions of the stars along with their measured brightnesses through the different filters. It contains about 173 million objects, of which about 84 million have been confirmed as stars. The other objects were either too faint or blended with their neighbours or affected by other artefacts, so that accurate measurements were not possible. Others were extended objects such as distant galaxies. The image used here required a huge amount of data processing, which was performed by Ignacio Toledo at the ALMA OSF. It corresponds to a pixel scale of 0.6 arcseconds per pixel, down-sampled from the original pixel scale of 0.34 arcseconds per pixel. [3] A colour–magnitude diagram is a graph that plots the apparent brightnesses of a set of objects against their colours. The colour is measured by comparing how bright objects look through different filters. It is similar to a Hertzsprung-Russell (HR) diagram but the latter plots luminosity (or absolute magnitude) rather than just apparent brightness and a knowledge of the distances of the stars plotted is also needed. [4] The transit method for finding planets searches for the small drop in brightness of a star that occurs when a planet passes in front of it and blocks some of its light. The small size of the red dwarf stars, typically with spectral types K and M, gives a greater relative drop in brightness when low-mass planets pass in front of them, making it easier to search for planets around them. More information: This research was presented in a paper “Milky Way Demographics with the VVV Survey I. The 84 Million Star Colour–Magnitude Diagram of the Galactic Bulge“ by R. K. Saito et al., which was published in the journal Astronomy & Astrophysics (A&A, 544, A147). The team is composed of R. K. Saito (Pontificia Universidad Católica de Chile, Santiago, Chile; Universidad de Valparaíso, Chile; The Milky Way Millennium Nucleus, Chile), D. Minniti (Pontificia Universidad Católica de Chile; Vatican Observatory), B. Dias (Universidade de São Paulo, Brazil), M. Hempel (Pontificia Universidad Católica de Chile), M. Rejkuba (ESO, Garching, Germany), J. Alonso-García (Pontificia Universidad Católica de Chile), B. Barbuy (Universidade de São Paulo), M. Catelan (Pontificia Universidad Católica de Chile), J. P. Emerson (Queen Mary University of London, United Kingdom), O. A. Gonzalez (ESO, Garching, Germany), P. W. Lucas (University of Hertfordshire, Hatfield, United Kingdom) and M. Zoccali (Pontificia Universidad Católica de Chile). The year 2012 marks the 50th anniversary of the founding of the European Southern Observatory (ESO). 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 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”. Links: Research paper (A&A, 544, A147): http://www.aanda.org/10.1051/0004-6361/201219448, Photos of the VISTA telescope: http://www.eso.org/public/images/archive/search/?adv=&subject_name=Visible%20and%20Infrared%20Survey%20Telescope%20for%20Astronomy, Images taken with the VISTA telescope: http://www.eso.org/public/images/archive/search/?adv=&facility=30, Image, Text, Credits: ESO/VVV Consortium/Acknowledgement: Ignacio Toledo, Martin Kornmesser/Nick Risinger (skysurvey.org)/Videos: ESO/VVV Consortium/Nick Risinger (skysurvey.org)/Music: Delmo -- Acoustic (disasterpeace.com)/Acknowledgement: Ignacio Toledo, Martin Kornmesser., Greetings, Orbiter.ch, Source: Orbiter.ch Space News

Read More........→October 26, 2012

View Of Earth From Saturn And Saturn As Never Seen Before

Image credit: NASA/JPL-Caltech 

NASA's Cassini spacecraft, now exploring Saturn, will take a picture of our home planet from a distance of hundreds of millions of miles on July 19. NASA is inviting the public to help acknowledge the historic interplanetary portrait as it is being taken. This simulated view from NASA's Cassini spacecraft shows the expected positions of Saturn and Earth on July 19, 2013, around the time Cassini will take Earth's picture. Cassini will be about 898 million miles (1.44 billion kilometers) away from Earth at the time. That distance is nearly 10 times the distance from the sun to Earth. Earth will appear as a small, pale blue dot between the rings of Saturn in the image, which will be part of a mosaic, or multi-image portrait, of the Saturn system Cassini is composing. "While Earth will be only about a pixel in size from Cassini's vantage point 898 million (1.44 billion kilometers) away, the team is looking forward to giving the world a chance to see what their home looks like from Saturn," said Linda Spilker, Cassini project scientist at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, Calif. "We hope you'll join us in waving at Saturn from Earth, so we can commemorate this special opportunity." Cassini will start obtaining the Earth part of the mosaic at 5:27 p.m. EDT (2:27 p.m. PDT or 21:27 UTC) and end about 15 minutes later, all while Saturn is eclipsing the sun from Cassini's point of view. The spacecraft's unique vantage point in Saturn's shadow will provide a special scientific opportunity to look at the planet's rings. At the time of the photo, North America and part of the Atlantic Ocean will be in sunlight. With giant Saturn hanging in the blackness and sheltering Cassini from the sun's blinding glare, the spacecraft viewed the rings as never before, revealing previously unknown faint rings and even glimpsing its home world. This marvelous panoramic view was created by combining a total of 165 images taken by the Cassini wide-angle camera over nearly three hours on Sept. 15, 2006. The full mosaic consists of three rows of nine wide-angle camera footprints; only a portion of the full mosaic is shown here. Color in the view was created by digitally compositing ultraviolet, infrared and clear filter images and was then adjusted to resemble natural color. The mosaic images were acquired as the spacecraft drifted in the darkness of Saturn's shadow for about 12

Credit: NASA/JPL/Space Science Institute

hours, allowing a multitude of unique observations of the microscopic particles that compose Saturn's faint rings. Unlike two previous Cassini eclipse mosaics of the Saturn system in 2006, which captured Earth, and another in 2012, the July 19 image will be the first to capture the Saturn system with Earth in natural color, as human eyes would see it. It also will be the first to capture Earth and its moon with Cassini's highest-resolution camera. The probe's position will allow it to turn its cameras in the direction of the sun, where Earth will be, without damaging the spacecraft's sensitive detectors. "Ever since we caught sight of the Earth among the rings of Saturn in September 2006 in a mosaic that has become one of Cassini's most beloved images, I have wanted to do it all over again, only better," said Carolyn Porco, Cassini imaging team lead at the Space Science Institute in Boulder, Colo. "This time, I wanted to turn the entire event into an opportunity for everyone around the globe to savor the uniqueness of our planet and the preciousness of the life on it." Porco and her imaging team associates examined Cassini's planned flight path for the remainder of its Saturn mission in search of a time when Earth would not be obstructed by Saturn or its rings. Working with other Cassini team members, they found the July 19 opportunity would permit the spacecraft to spend time in Saturn's shadow to duplicate the views from earlier in the mission to collect both visible and infrared imagery of the planet and its ring system. "Looking back towards the sun through the rings highlights the tiniest of ring particles, whose width is comparable to the thickness of hair and which are difficult to see from ground-based telescopes," said Matt Hedman, a Cassini science team member based at Cornell University in Ithaca, N.Y., and a member of the rings working group. "We're particularly interested in seeing the structures within Saturn's dusty E ring, which is sculpted by the activity of the geysers on the moon Enceladus, Saturn's magnetic field and even solar radiation pressure." This latest image will continue a NASA legacy of space-based images of our fragile home, including the 1968 "Earthrise" image taken by the Apollo 8 moon mission from about 240,000 miles (380,000 kilometers) away and the 1990 "Pale Blue Dot" image taken by Voyager 1 from about 4 billion miles (6 billion kilometers) away. The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL manages the Cassini-Huygens mission for NASA's Science Mission Directorate in Washington, and designed, developed and assembled the Cassini orbiter and its two onboard cameras. The imaging team consists of scientists from the United States, the United Kingdom, France and Germany. The imaging operations center is based at the Space Science Institute in Boulder, Colo. To learn more about the public outreach activities associated with the taking of the image, visit: http://saturn.jpl.nasa.gov/waveatsaturn, For more information about Cassini, visit, http://www.nasa.gov/cassini, Source: Nanopatents And Innovations

Read More........→June 19, 2013

Google deploying planes over cities for 3D maps

A three-dimensional view of the Cliff House in San Francisco on Google Earth. -AP

Deccan Chronicle, Reuters, San Francisco: Google is deploying a fleet of small, camera-equipped airplanes above several cities, the Internet search company's latest step in its ambitious and sometimes controversial plan to create a digital map of the world. Google plans to release the first three-dimensional maps for several cities by the end of the year, the company said at a news conference at its San Francisco offices on Wednesday. Google declined to name the cities, but it showed a demonstration of a 3D map of San Francisco, in which a user can navigate around an aerial view of the city. "We're trying to create the illusion that you're just flying over the city, almost as if you were in your own personal helicopter," said Peter Birch, a product manager for Google Earth. Google's head of engineering for its maps product, Brian McClendon, said the company was using a fleet of airplanes owned and operated by contractors and flying exclusively for Google. Asked about potential privacy implications, McClendon said the privacy issues were similar to all aerial imagery and that the type of 45-degree-angle pictures that the planes take have been used for a long time. Google has used airplanes to collect aerial photos in the past, such as following the 2010 San Bruno, California gas-line explosion, but the latest effort marks the first time the company will deploy the planes in a systemic manner to build a standard feature in one of its products. By the end of the year, Google said it expects to have 3D map coverage for metropolitan areas with a combined population of 300 million people. The first 3D cityscape will be available within weeks. Google has for years operated a fleet of camera-equipped cars that crisscross the globe taking panoramic pictures of streets for its popular mapping service. The cars have raised privacy concerns in some countries. In 2010, Google acknowledged that the so-called Street View cars had been inadvertently collecting emails, passwords and other personal data from people's home wireless networks. Collecting the WiFi data was unrelated to the Google Maps project, and was done instead so that Google could collect data on WiFi hotspots that can be used to provide separate location-based services. The forthcoming 3D city maps will be part of the Google Earth software app available for mobile devices such as smartphones based on Google's Android software and Apple's iOS software. The company also announced a version of Google maps for Android smartphones that allows users to access certain maps without an Internet connection. Shares of Google finished on Wednesday's regular session up 1.8 per cent at $580.57. Google's announcement comes a week before Apple Inc's developer conference in San Francisco, as competition between the two tech giants continues to heat up, particularly in the fast-growing mobile market. Apple is planning to replace Google Maps as the built-in mapping service on its iPhone and iPad later this year with technology that it has created in-house, according to media reports. Apple could show off its new mapping software at next week's conference. Google's McClendon said the company would continue to make Google maps services available as widely as possible, on "all platforms." In what appeared to be a veiled jab at Apple, he said the integration with Google's search engine provides a mapping serving that is far more useful than a product that simply uses a 'geocoder' - technology that uses geographic coordinates to create a digital map. Apple began to use its own geocoder technology for the Google-based maps on its smartphones late last year. Google said on Wednesday that there are currently 1 billion monthly active users of Google maps services and that the Street View cars have driven more than 5 million miles (8 million km) Photographing streets all over the world. Asked if Google had any plans to use unmanned aerial drones to gather photos for its 3D cityscapes, McClendon said it was an interesting question, but noted that drones were still being evaluated by the Federal Aviation Administration. "That's a larger can of worms that we're not going to get into here," he said. Source: Deccan Chronicle

Read More........→August 17, 2012