SpaceX CRS-1 Launch, NASA Celebrates Milestone Liftoff!

SpaceX - CRS-1 Mission patch.

08 Oct 2012

Commercial Resupply Launch

    Mission: SpaceX CRS-1
    Launch Vehicle: Falcon 9
    Launch Site: Cape Canaveral Air Force Station, Fla.
    Launch Pad: Space Launch Complex 40
    Date: October 7
    Time: 8:35 p.m. EDT

Description: SpaceX CRS-1 will be the first commercial resupply mission to the International Space Station by Space Exploration Technologies (SpaceX).

 SpaceX CRS-1 Launch

The Falcon 9 and Dragon capsule lift off of the pad on a mission to open America's new operational cargo capability to the International Space Station!

SpaceX launched the first of a dozen operational missions to deliver supplies to the International Space Station on Oct. 7 for NASA. Launch time came at 8:35 p.m. from Launch Complex 40 at Cape Canaveral Air Force Station in Florida, just a few miles south of the space shuttle launch pads. The spacecraft will be joined to the station three days later.

Image above: The SpaceX Falcon 9 and Dragon capsule lift off Oct. 7. Photo credit: NASA.

NASA Administrator Charles Bolden and SpaceX President Gwynne Shotwell celebrated the successful liftoff of a landmark cargo mission to the International Space Station tonight as a SpaceX Dragon spacecraft loaded with supplies flew on its own in orbit. The flight is the first operational resupply mission for the company and NASA.

"This was a critical event in spaceflight tonight," Bolden said. "We're once again launching spacecraft from American soil with the supplies our astronauts need in space. NASA and the nation are embarking on an ambitious program of space exploration."

Hawthorne, Calif.-based Space Exploration Technologies, or SpaceX, launched its Dragon capsule aboard a Falcon 9 rocket at 8:35 p.m. EDT, capping a flawless countdown with spectacular show of light and thunder from the rocket's nine engines.

"This was an operational mission, so we're operational (but that) doesn't mean we're going to stop learning and stop making these vehicles as reliable as possible," Shotwell said during a press conference after the launch.

SpaceX Dragon in orbit

Dragon will rendezvous with the orbiting laboratory Wednesday so astronaut and station commander Suni Williams can reach out with the station's robot arm and grapple the Dragon. The spacecraft will then be joined to one of the station's ports where astronauts will unload its 1,000 pounds of materials. They will also load almost 2,000 pounds of used equipment and experiments inside the Dragon to be returned to Earth safely in about three weeks.

For more information about SpaceX, visit: http://www.spacex.com/

Images, Video, Text, Credits: NASA / NASA TV / SpaceX.

Best regards, Orbiter.ch

NASA's Swift Satellite Discovers a New Black Hole in our Galaxy

NASA - SWIFT Mission patch.

Oct. 05, 2012

Image above: Gas flood of gas plunging toward a previously unknown black hole. Credit: NASA's Goddard Space Flight Center.

NASA's Swift satellite recently detected a rising tide of high-energy X-rays from a source toward the center of our Milky Way galaxy. The outburst, produced by a rare X-ray nova, announced the presence of a previously unknown stellar-mass black hole.

"Bright X-ray novae are so rare that they're essentially once-a-mission events and this is the first one Swift has seen," said Neil Gehrels, the mission's principal investigator, at NASA's Goddard Space Flight Center in Greenbelt, Md. "This is really something we've been waiting for."

Video above: An X-ray outburst caught by NASA's Swift on Sept. 16, 2012, resulted from a flood of gas plunging toward a previously unknown black hole. Gas flowing from a sun-like star collects into a disk around the black hole. Normally, this gas would steadily spiral inward. But in this system, named Swift J1745-26, the gas collects for decades before suddenly surging inward. Credit: NASA's Goddard Space Flight Center.

An X-ray nova is a short-lived X-ray source that appears suddenly, reaches its emission peak in a few days and then fades out over a period of months. The outburst arises when a torrent of stored gas suddenly rushes toward one of the most compact objects known, either a neutron star or a black hole.

The rapidly brightening source triggered Swift's Burst Alert Telescope twice on the morning of Sept. 16, and once again the next day.

Named Swift J1745-26 after the coordinates of its sky position, the nova is located a few degrees from the center of our galaxy toward the constellation Sagittarius. While astronomers do not know its precise distance, they think the object resides about 20,000 to 30,000 light-years away in the galaxy's inner region.

Ground-based observatories detected infrared and radio emissions, but thick clouds of obscuring dust have prevented astronomers from catching Swift J1745-26 in visible light.

The nova peaked in hard X-rays -- energies above 10,000 electron volts, or several thousand times that of visible light -- on Sept. 18, when it reached an intensity equivalent to that of the famous Crab Nebula, a supernova remnant that serves as a calibration target for high-energy observatories and is considered one of the brightest sources beyond the solar system at these energies.

Even as it dimmed at higher energies, the nova brightened in the lower-energy, or softer, emissions detected by Swift's X-ray Telescope, a behavior typical of X-ray novae. By Wednesday, Swift J1745-26 was 30 times brighter in soft X-rays than when it was discovered and it continued to brighten.

"The pattern we're seeing is observed in X-ray novae where the central object is a black hole. Once the X-rays fade away, we hope to measure its mass and confirm its black hole status," said Boris Sbarufatti, an astrophysicist at Brera Observatory in Milan, Italy, who currently is working with other Swift team members at Penn State in University Park, Pa.

The black hole must be a member of a low-mass X-ray binary (LMXB) system, which includes a normal, sun-like star. A stream of gas flows from the normal star and enters into a storage disk around the black hole. In most LMXBs, the gas in the disk spirals inward, heats up as it heads toward the black hole, and produces a steady stream of X-rays.

But under certain conditions, stable flow within the disk depends on the rate of matter flowing into it from the companion star. At certain rates, the disk fails to maintain a steady internal flow and instead flips between two dramatically different conditions -- a cooler, less ionized state where gas simply collects in the outer portion of the disk like water behind a dam, and a hotter, more ionized state that sends a tidal wave of gas surging toward the center.

NASA's Swift satellite. Credit: NASA's Goddard Space Flight Center.

"Each outburst clears out the inner disk, and with little or no matter falling toward the black hole, the system ceases to be a bright source of X-rays," said John Cannizzo, a Goddard astrophysicist. "Decades later, after enough gas has accumulated in the outer disk, it switches again to its hot state and sends a deluge of gas toward the black hole, resulting in a new X-ray outburst."

This phenomenon, called the thermal-viscous limit cycle, helps astronomers explain transient outbursts across a wide range of systems, from protoplanetary disks around young stars, to dwarf novae -- where the central object is a white dwarf star -- and even bright emission from supermassive black holes in the hearts of distant galaxies.

Swift, launched in November 2004, is managed by Goddard Space Flight Center. It is operated in collaboration with Penn State, the Los Alamos National Laboratory in New Mexico and Orbital Sciences Corp. in Dulles, Va., with international collaborators in the United Kingdom and Italy and including contributions from Germany and Japan.

Related Links:

Swift website: http://www.nasa.gov/swift

Video on the NASA Explorer YouTube channel: http://www.youtube.com/watch?v=_W-QEs8sKE0

Images (mentioned), Video (mentioned), Text, Credit: NASA's Goddard Space Flight Center / Francis Reddy.

Greetings, Orbiter.ch

Competition winner observes Thor’s Helmet Nebula with the VLT during live broadcast

ESO - European Southern Observatory logo.

5 October 2012

ESO Celebrates its 50th Anniversary 

Thor’s Helmet Nebula imaged on the occasion of ESO’s 50th Anniversary

Today, 5 October 2012, the European Southern Observatory (ESO) is celebrating 50 years since the signing of its founding convention. Over the last half century ESO has become the world’s most productive ground-based astronomical observatory. This morning, for the first time ever, observations with ESO’s Very Large Telescope were made of an object chosen by the public. The winner of an anniversary competition pointed the VLT towards the spectacular Thor’s Helmet Nebula and the observations were broadcast live over the internet. To mark the occasion ESO and its partners are organising many other activities in the 15 ESO Member States.

The signing of the ESO Convention on 5 October 1962 and the foundation of ESO was the culmination of the dream of leading astronomers from five European countries — Belgium, France, Germany, the Netherlands and Sweden. They had decided to join forces with the primary goal of building a large telescope that would give them access to the magnificent and rich southern sky.

The Thor’s Helmet Nebula (NGC 2359) in the constellation of Canis Major (The Great Dog)

"Fifty years later, the original hopes of the five founding members have not only become reality, but have been greatly surpassed," says Tim de Zeeuw, ESO’s Director General. "ESO has fully taken up the challenge of its mission to design, build and operate the most powerful ground-based observing facilities on the planet."

Operating three unique and world-class observing sites in Chile — La Silla, Paranal and Chajnantor — ESO has become a leader in the astronomical research community [1].

Wide-field view of the sky around the Thor’s Helmet Nebula

At Paranal, ESO operates the Very Large Telescope (VLT), the world’s most advanced visible-light astronomical observatory, which, since first light in 1998, has been a driving force in a new age of discoveries. On the Chajnantor Plateau in northern Chile, ESO and its international partners [2] are are building a revolutionary astronomical telescope — ALMA, the Atacama Large Millimeter/submillimeter Array [3] will help to unveil the mysteries of the cold Universe.

ESO’s original observatory at La Silla is still very productive and remains at the forefront of astronomical research. In particular the HARPS instrument on the 3.6-metre telescope is the world’s most successful exoplanet hunting machine.

Zooming in on Thor’s Helmet

ESO’s huge next telescope is only a few years away. The 39-metre European Extremely Large Telescope (E-ELT) will become "the world’s biggest eye on the sky". With first light planned for early in the next decade, the E-ELT will tackle the biggest scientific challenges of our time and may revolutionise our perception of the Universe as much as Galileo's telescope did more than 400 years ago.

To celebrate the 50th anniversary, ESO and its partners are organising many events and public initiatives during 2012 [4]. A series of special coordinated public events are taking place today in the 15 Member States, as well as a multitude of Awesome Universe exhibitions.

Panning across the Thor’s Helmet Nebula

As part of the anniversary celebrations, for the first time ever, this morning the VLT  was pointed towards an object in the sky selected by members of the public — the Thor’s Helmet Nebula [5]. This nebula was picked in the recent Choose what the VLT Observes contest (ann12060). The observations were performed by Brigitte Bailleul — winner of the Tweet Your Way to the VLT! competition — and were broadcast live over the internet from Paranal Observatory. This image, taken in the superb conditions typical of Paranal, is the most detailed ever obtained of this striking object.

"With the VLT, ALMA and the future E-ELT, ESO is entering a new era, one that not even the initial bold dreams of ESO’s founding members could have anticipated. To all of you that have made it possible, on behalf of ESO, thank you!" concludes Tim de Zeeuw.

Notes:

[1] Information about the publication statistics at different observatories is given here.

[2] The ALMA project is a partnership of Europe, North America and East Asia in cooperation with the Republic of Chile.

[3] ALMA will be a single telescope composed of 66 high-precision antennas. ALMA's construction will be completed in 2013, but early scientific observations with a partial array began in 2011 (eso1137).

[4] A documentary movie is being released to celebrate the  anniversary, together with a sumptuously illustrated book. The movie has been also released as episodes in ESO’s popular ESOcast video podcast series. In addition, a new and very detailed book on the history of ESO’s triumphs and challenges will be published.

[5] The Thor’s Helmet Nebula, also known as NGC 2359, lies in the constellation of Canis Major (The Great Dog). The helmet-shaped nebula is around 15 000 light-years away from Earth and is over 30 light-years across. The helmet is a cosmic bubble, blown as the wind from the bright, massive star near the bubble's centre sweeps through the surrounding molecular cloud. The glowing gas is heated by the energetic radiation provided by the central star. Many different colours, originating from different elements in the gas, are also visible, as well as many dust clouds.

More information:

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 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:

    Live anniversary webcast: http://www.eso.org/public/outreach/50years/webcast.html

    Public 5 October 2012 events: http://www.eso.org/public/events/special-evt/5oct2012.html

    Awesome Universe exhibitions: http://www.eso.org/public/events/special-evt/awesome-universe.html

    ESO 50th web page: http://www.eso.org/public/outreach/50years.html

    ESO Top-10 Science achievements: http://www.eso.org/public/science/top10.html

Images, Text, Credits: ESO / B. Bailleul / IAU and Sky & Telescope / Digitized Sky Survey 2. Acknowledgement: Davide De Martin / Videos: ESO/B. Bailleul/Digitized Sky Survey 2/Nick Risinger (skysurvey.org). Music: Disasterpeace.

Best regards, Orbiter.ch

Launch of GPS IIF-3 on Delta IV Medium Rocket

GPS IIF-3 on Delta IV Mission poster.

Oct. 4, 2012

A Delta IV Medium rocket in the (4,2) configuration launched today, October 4th 2012 at 12:10 UTC with the GPS IIF-3 spacecraft for the U.S. Air Force.

Launch of GPS IIF-3 on Delta IV Medium Rocket

Lift off occurred from Space Launch Complex 37 at Cape Canaveral.

The United Launch Alliance Delta 4 rocket will deploy the Air Force's third Block 2F navigation satellite for the Global Positioning System. The rocket will fly in the Medium+ (4,2) configuration with two solid rocket boosters. Delayed from Sept. 20.

Delta IV Medium rocket description

GPS IIF satellite by Boeing

GPS-2F (Global Positioning System) or Navstar-2F (Navigation System using Timing And Ranging) satellites are the fourth evolution stage of the second generation of the GPS satellites. Improvements included an extended design life of 12 years, faster processors with more memory, and a new civil signal on a third frequency.

GPS 2F-3 satellite

The GPS-2F satellites do not need to carry an apogee kick motor, in contrast to the earlier generations, as the launch vehicles provide direct insertion into the GPS orbit. Originally the Delta-4M version was to be used for the Delta launches, but a mass growth of the satellites required a switch to the more powerful Delta-4M+(4,2) version. For Atlas launches, the Atlas-5(401) version is used.

GPS constellation

Boeing was contracted with options for up to 33 Block-IIF satellites in 1996, but in 2001 the contract was reduced 12 Block-IIF satellites. In July 2006, satellites 10, 11 and 12 were contracted. The first Block-IIF satellite was originally scheduled to launch in 2006, but was finally launched in 2010.

Images, Text, Credits: NASA / Youtube / Boeing / ULA / USAF.

Greetings, Orbiter.ch

NASA Mars Curiosity Rover Prepares to Study Martian Soil

NASA - Mars Science Laboratory (MSL) patch.

Oct. 4, 2012

Image above: NASA's Mars rover Curiosity cut a wheel scuff mark into a wind-formed ripple at the "Rocknest" site to give researchers a better opportunity to examine the particle-size distribution of the material forming the ripple. Image credit: NASA / JPL-Caltech.

NASA's Curiosity rover is in a position on Mars where scientists and engineers can begin preparing the rover to take its first scoop of soil for analysis.

Curiosity is the centerpiece of the two-year Mars Science Laboratory mission. The rover's ability to put soil samples into analytical instruments is central to assessing whether its present location on Mars, called Gale Crater, ever offered environmental conditions favorable for microbial life. Mineral analysis can reveal past environmental conditions. Chemical analysis can check for ingredients necessary for life.

"We now have reached an important phase that will get the first solid samples into the analytical instruments in about two weeks," said Mission Manager Michael Watkins of NASA's Jet Propulsion Laboratory in Pasadena, Calif. "Curiosity has been so well-behaved that we have made great progress during the first two months of the mission."

The rover's preparatory operations will involve testing its robotic scooping capabilities to collect and process soil samples. Later, it also will use a hammering drill to collect powdered samples from rocks. To begin preparations for a first scoop, the rover used one of its wheels Wednesday to scuff the soil to expose fresh material.

Next, the rover twice will scoop up some soil, shake it thoroughly inside the sample-processing chambers to scrub the internal surfaces, then discard the sample. Curiosity will scoop and shake a third measure of soil and place it in an observation tray for inspection by cameras mounted on the rover's mast. A portion of the third sample will be delivered to the mineral-identifying chemistry and mineralogy (CheMin) instrument inside the rover. From a fourth scoopful, samples will be delivered to both CheMin and to the sample analysis at Mars (SAM) instrument, which identifies chemical ingredients.

"We're going to take a close look at the particle size distribution in the soil here to be sure it's what we want," said Daniel Limonadi of JPL, lead systems engineer for Curiosity's surface sampling and science system. "We are being very careful with this first time using the scoop on Mars."

Image above: This patch of windblown sand and dust downhill from a cluster of dark rocks is the "Rocknest" site, which has been selected as the likely location for first use of the scoop on the arm of NASA's Mars rover Curiosity. Image credit: NASA / JPL-Caltech / MSSS.

The rinse-and-discard cycles serve a quality-assurance purpose similar to a common practice in geochemical laboratory analysis on Earth.

"It is standard to run a split of your sample through first and dump it out, to clean out any residue from a previous sample," said JPL's Joel Hurowitz, a sampling system scientist on the Curiosity team. "We want to be sure the first sample we analyze is unambiguously Martian, so we take these steps to remove any residual material from Earth that might be on the walls of our sample handling system."

Rocknest is the name of the area of soil Curiosity will test and analyze. The rover pulled up to the windblown, sandy and dusty location Oct. 2. The Rocknest patch is about 8 feet by 16 feet (2.5 meters by 5 meters). The area provides plenty of area for scooping several times. Diverse rocks nearby provide targets for investigation with the instruments on Curiosity's mast during the weeks the rover is stationed at Rocknest for this first scooping campaign.

Mars Science Laboratory (MSL). Image credit: NASA / JPL-Caltech

Curiosity's motorized, clamshell-shaped scoop is 1.8 inches (4.5 centimeters) wide, 2.8 inches (7 centimeters) long, and can sample to a depth of about 1.4 inches (3.5 centimeters). It is part of the collection and handling Martian rock analysis (CHIMRA) device on a turret of tools at the end of the rover's arm. CHIMRA also includes a series of chambers and labyrinths for sorting, sieving and portioning samples collected by the scoop or by the arm's percussive drill.

Following the work at Rocknest, the rover team plans to drive Curiosity about 100 yards (about 100 meters) eastward into the Glenelg area and select a rock as the first target for use of its drill.

JPL, a division of the California Institute of Technology, manages the Mars Science Laboratory Project and built Curiosity.

For more about Curiosity, visit: http://www.nasa.gov/msl or http://mars.jpl.nasa.gov/msl .

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

Images (mentioned), Text, Credits: NASA / Dwayne Brown / JPL / Guy Webster / D.C. Agle.

Regards, Orbiter.ch

Ice-coated beauty in Mars’ Silver Island

ESA - Mars Express Mission patch.

4 October 2012

 Argyre Planitia and Hooke Crater

On 8 June, the high-resolution stereo camera on Mars Express captured a region within the 1800 km-wide and 5 km-deep Argyre basin, which was created by a gigantic impact in the planet’s early history.

After Hellas, the Argyre impact basin is the second largest on the Red Planet. 

Argyre and Hooke Crater perspective view

 The name stems from the Greek word ‘argyros’ (silver) and Argyre was an ‘island of silver’ in Greek and Roman mythology. Giovanni Schiaparelli, the famed Italian astronomer, gave the name to this bright region on Mars in his detailed 1877 map.

At the centre of the larger impact basin is a flat region known as Argyre Planitia. The Mars Express images in this release all show a portion of the northern part of this plain, with a large portion of each image dominated by the western half of the 138 km-wide Hooke Crater, named after the British physicist and astronomer Robert Hooke.

Argyre and Hooke Crater in context

Most of Argyre Planitia has been shaped by wind, glacial and lacustrine (lake-based) processes, creating the smoother appearance of the landscape surrounding Hooke Crater.

Inside Hooke Crater itself, prevailing wind activity has formed dunes and helped to create linear erosion features, clearly seen in the following topographic image.

Topographical view Argyre Planitia

The most striking feature of this image release, shown clearly in the first image at the top of the page, is the icing sugar-like covering of the surface to the south (left) of the image. This is frost, but made of carbon dioxide, not water.

Carbon dioxide ice is commonly seen on the surface of Mars, and has long been thought to form only at ground level, freezing out of the atmosphere as frost, which is most likely the case here.

3D anaglyph view Hooke Crater

The lowlands to the south (left in the first image) of Hooke and regions within the crater are covered by a thin ice layer. However, it is lacking on the inner north-facing crater wall. It was probably melted there by the Sun, as indicated by the timing of the image.

Taken at around 4:30 in the local afternoon and during the southern hemisphere’s mid-winter, the Sun would have been just over 20 degrees above the horizon. It should then have been able to melt ice on the steeper north-facing slopes, but would probably not have had enough time to warm and melt any on low-lying horizontal surfaces.

ESA's Mars Express

Schiaparelli would doubtless have marvelled at the exquisite images coming back from Mars Express, which continues to provide today’s scientists with a bounty of wonderful data.

Related links:
High Resolution Stereo Camera: http://berlinadmin.dlr.de/Missions/express/indexeng.shtml

Behind the lens: http://www.esa.int/SPECIALS/Mars_Express/SEMSXE1PGQD_0.html

Frequently asked questions: http://www.esa.int/SPECIALS/Mars_Express/SEM76D9OY2F_0.html

For specialists:

ESA Planetary Science archive (PSA): http://www.rssd.esa.int/PSA

NASA Planetary Data System: http://pds-geosciences.wustl.edu/missions/mars_express/hrsc.htm

HRSC data viewer: http://hrscview.fu-berlin.de/

Images Text, Credits: ESA / DLR / FU Berlin (G. Neukum) / NASA MGS MOLA Science Team.

Best regards, Orbiter.ch

NASA Observatory Measures Expansion of Universe

NASA - Spitzer Space Telescope patch.

October 3, 2012

Image above: The cosmic distance ladder, symbolically shown here in this artist's concept, is a series of stars and other objects within galaxies that have known distances. Image credit: NASA/JPL-Caltech.

Astronomers using NASA's Spitzer Space Telescope have announced the most precise measurement yet of the Hubble constant, or the rate at which our universe is stretching apart.

The Hubble constant is named after the astronomer Edwin P. Hubble, who astonished the world in the 1920s by confirming our universe has been expanding since it exploded into being 13.7 billion years ago. In the late 1990s, astronomers discovered the expansion is accelerating, or speeding up over time. Determining the expansion rate is critical for understanding the age and size of the universe.

Unlike NASA's Hubble Space Telescope, which views the cosmos in visible light, Spitzer took advantage of long-wavelength infrared light to make its new measurement. It improves by a factor of 3 on a similar, seminal study from the Hubble telescope and brings the uncertainty down to 3 percent, a giant leap in accuracy for cosmological measurements. The newly refined value for the Hubble constant is 74.3 plus or minus 2.1 kilometers per second per megaparsec. A megaparsec is roughly 3 million light-years.

"Spitzer is yet again doing science beyond what it was designed to do," said project scientist Michael Werner at NASA's Jet Propulsion Laboratory in Pasadena, Calif. Werner has worked on the mission since its early concept phase more than 30 years ago. "First, Spitzer surprised us with its pioneering ability to study exoplanet atmospheres," said Werner, "and now, in the mission's later years, it has become a valuable cosmology tool."

In addition, the findings were combined with published data from NASA's Wilkinson Microwave Anisotropy Probe to obtain an independent measurement of dark energy, one of the greatest mysteries of our cosmos. Dark energy is thought to be winning a battle against gravity, pulling the fabric of the universe apart. Research based on this acceleration garnered researchers the 2011 Nobel Prize in physics.

"This is a huge puzzle," said the lead author of the new study, Wendy Freedman of the Observatories of the Carnegie Institution for Science in Pasadena. "It's exciting that we were able to use Spitzer to tackle fundamental problems in cosmology: the precise rate at which the universe is expanding at the current time, as well as measuring the amount of dark energy in the universe from another angle." Freedman led the groundbreaking Hubble Space Telescope study that earlier had measured the Hubble constant.

Glenn Wahlgren, Spitzer program scientist at NASA Headquarters in Washington, said infrared vision, which sees through dust to provide better views of variable stars called cepheids, enabled Spitzer to improve on past measurements of the Hubble constant.

"These pulsating stars are vital rungs in what astronomers call the cosmic distance ladder: a set of objects with known distances that, when combined with the speeds at which the objects are moving away from us, reveal the expansion rate of the universe," said Wahlgren.

Cepheids are crucial to the calculations because their distances from Earth can be measured readily. In 1908, Henrietta Leavitt discovered these stars pulse at a rate directly related to their intrinsic brightness.

This graph illustrates the Cepheid period-luminosity relationship, which scientists use to calculate the size, age and expansion rate of the universe. Image credit: NASA/JPL-Caltech/Carnegie.

To visualize why this is important, imagine someone walking away from you while carrying a candle. The farther the candle traveled, the more it would dim. Its apparent brightness would reveal the distance. The same principle applies to cepheids, standard candles in our cosmos. By measuring how bright they appear on the sky, and comparing this to their known brightness as if they were close up, astronomers can calculate their distance from Earth.

Spitzer observed 10 cepheids in our own Milky Way galaxy and 80 in a nearby neighboring galaxy called the Large Magellanic Cloud. Without the cosmic dust blocking their view, the Spitzer research team was able to obtain more precise measurements of the stars' apparent brightness, and thus their distances. These data opened the way for a new and improved estimate of our universe's expansion rate.

"Just over a decade ago, using the words 'precision' and 'cosmology' in the same sentence was not possible, and the size and age of the universe was not known to better than a factor of two," said Freedman. "Now we are talking about accuracies of a few percent. It is quite extraordinary."

The study appears in the Astrophysical Journal. Freedman's co-authors are Barry Madore, Victoria Scowcroft, Chris Burns, Andy Monson, S. Eric Person and Mark Seibert of the Observatories of the Carnegie Institution and Jane Rigby of NASA's Goddard Space Flight Center in Greenbelt, Md.

NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology in Pasadena. Data are archived at the Infrared Science Archive housed at the Infrared Processing and Analysis Center at Caltech. Caltech manages JPL for NASA. For more information about Spitzer, visit http://spitzer.caltech.edu and http://www.nasa.gov/spitzer .

Images (mentioned), Text, Credits: NASA / J.D. Harrington / JPL / Whitney Clavin.

Greetings, Orbiter.ch