This artists’s cartoon view gives an impression of how common planets are around the stars in the Milky Way. The planets, their orbits and their host stars are all vastly magnified compared to their real separations. A six-year search that surveyed millions of stars using the microlensing technique concluded that planets around stars are the rule rather than the exception. The average number of planets per star is greater than one. Credit: ESO/M. Kornmesser
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How common are planets in the Milky Way? A new study using gravitational microlensing suggests that every star in our night sky has at least one planet circling it. “We used to think that the Earth might be unique in our galaxy,” said Daniel Kubas, a co-lead author of a paper that appears this week in the journal Nature. “But now it seems that there are literally billions of planets with masses similar to Earth orbiting stars in the Milky Way.”
Over the past 16 years, astronomers have detected more than 3,035 exoplanets – 2,326 candidates and 709 confirmed planets orbiting other stars. Most of these extrasolar planets have been discovered using the radial velocity method (detecting the effect of the gravitational pull of the planet on its host star) or the transit method (catching the planet as it passes in front of its star, slightly dimming it.) Those two methods usually tend to find large planets that are relatively close to their parent star.
But another method, gravitational microlensing — where the light from the background star is amplified by the gravity of the foreground star, which then acts as a magnifying glass — is able to find planets over a wide range of mass that are further away from their stars.
Gravitational microlensing method requires that you have two stars that lie on a straight line in relation to us here on Earth. Then the light from the background star is amplified by the gravity of the foreground star, which thus acts as a magnifying glass.
An international team of astronomers used the technique of gravitational microlensing in six-year search that surveyed millions of stars. “We conclude that stars are orbited by planets as a rule, rather than the exception,” the team wrote in their paper.
“We have searched for evidence for exoplanets in six years of microlensing observations,” said lead author Arnaud Cassan from the Institut de Astrophysique in Paris. “Remarkably, these data show that planets are more common than stars in our galaxy. We also found that lighter planets, such as super-Earths or cool Neptunes, must be more common than heavier ones.”
The Milky Way above the dome of the Danish 1.54-metre telescope at ESO's La Silla Observatory in Chile. The central part of the Milky Way is visible behind the dome of the ESO 3.6-metre telescope in the distance. On the right the Magellanic Clouds can be seen. This telescope was a major contributor to the PLANET project to search for exoplanets using microlensing. The picture was taken using a normal digital camera with a total exposure time of 15 minutes. Credit: ESO/Z. Bardon
The astronomers surveyed millions of stars looking for microlensing events, and 3,247 such events in 2002-2007 were spotted in data from the European Southern Observatory’s PLANET and OGLE searches. The precise alignment needed for microlensing is very unlikely, and statistical results were inferred from detections and non-detections on a representative subset of 440 light curves.
Three exoplanets were actually detected: a super-Earth and planets with masses comparable to Neptune and Jupiter. The team said that by microlensing standards, this is an impressive haul, and that in detecting three planets, they were either incredibly lucky despite huge odds against them, or planets are so abundant in the Milky Way that it was almost inevitable.
The astronomers then combined information about the three positive exoplanet detections with seven additional detections from earlier work, as well as the huge numbers of non-detections in the six years’ worth of data (non-detections are just as important for the statistical analysis and are much more numerous, the team said.) The conclusion was that one in six of the stars studied hosts a planet of similar mass to Jupiter, half have Neptune-mass planets and two thirds have super-Earths.
This works out to about 100 billion exoplanets in our galaxy.
The survey was sensitive to planets between 75 million kilometers and 1.5 billion kilometers from their stars (in the Solar System this range would include all the planets from Venus to Saturn) and with masses ranging from five times the Earth up to ten times Jupiter.
This also shows that microlensing is a viable way to find exoplanets. Astronomers hope to use other methods in the future to find even more planets.
“I have a list of 17 different ways to find exoplanets and only five have been used so far,” said Virginia Trimble from the University of California, Irvine and the Las Cumbres Observatory, providing commentary at the American Astronomical Scoeity meeting this week, “I expect we’ll be finding many more planets in the future.”
You may have heard by now about the 100 Year Starship project, a new research initiative to develop the technology required to send a manned mission to another star. The project is jointly sponsored by NASA and the Defense Advanced Research Projects Agency (DARPA). It will take that long just to make such a trip feasible, hence the name. So we’re a long ways off from naming any crew members or a starship captain, but the project itself does have a new leader, a former astronaut.
Mae Jemison, a former Space Shuttle astronaut, has been appointed the position by DARPA. She was also the first African-American woman to go into space, in 1992. Her own non-profit educational organization, the Dorothy Jemison Foundation for Excellence (in honor of her late mother) was chosen to work with DARPA, receiving a $500,000 contract. That funding is just seed money, to start the process of developing the framework needed for such an ambitious undertaking. The focus at this point is to create a foundation that can last long enough to research the technology required, rather than the actual government-funded building of the spacecraft.
As stated by the proposal, the goal is to “develop a viable and sustainable non-governmental organization for persistent, long-term, private-sector investment into the myriad of disciplines needed to make long-distance space travel viable.”
From the project’s mission statement:
The 100 Year Starship™ (100YSS™) study is an effort seeded by DARPA to develop a viable and sustainable model for persistent, long-term, private-sector investment into the myriad of disciplines needed to make long-distance space travel practicable and feasible.
The genesis of this study is to foster a rebirth of a sense of wonder among students, academia, industry, researchers and the general population to consider “why not” and to encourage them to tackle whole new classes of research and development related to all the issues surrounding long duration, long distance spaceflight. DARPA contends that the useful, unanticipated consequences of such research will have benefit to the Department of Defense and to NASA, as well as the private and commercial sector. This endeavor will require an understanding of questions such as: how do organizations evolve and maintain focus and momentum for 100 years or more; what models have supported long-term technology development; what resources and financial structures have initiated and sustained prior settlements of “new worlds?”
With today’s technology, it would take about 100,000 years to reach just the nearest star, Alpha Centauri. That time would hopefully be reduced significantly with the development of new, faster propulsion methods.
The dream of travelling to the stars may still be a long ways off in the future before becoming reality, but we are getting closer. Ad astra!
More information about the 100 Year Starship project is here.
An image of one of the Milky Way analogs found by Timothy Licquia and Jeffrey Newman. This galaxy, known to astronomers as SDSS J083909.27+450747.7, has properties which closely match those of the galaxy we live in. Credit: Sloan Digital Sky Survey
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What color would the Milky Way appear to alien civilizations looking at our galaxy through their telescopes? It turns out the Milky Way has approximately the right name – but for all the wrong reasons. “The true color of the Milky Way is as white as fine-grained new spring snow seen in early morning light,” said Dr. Jeffrey Newman, from the University of Pittsburgh, speaking at a press conference from the American Astronomical Society (AAS) Meeting.
Our ancestors gave our galaxy the name “Milky Way” because when they looked up and saw the band of the stars that stretches from one horizon to the other, it appears white to our human eyes. “But that’s only because our low-light vision isn’t sensitive to color,” said Newman. “There are portions of the Milky Way that are more yellow or red versus more blue, but our eyes can’t pick that up. But a sensitive instrument or photograph can.”
When we look at other galaxies, we can see them in their entirety, and can examine them for color and luminosity. Color and luminosity have been great tool for astronomy, helping us to understand stars and galaxies.
“Unfortunately we can’t get a complete picture of the Milky Way from outside, so we have had to resort to other methods,” said Newman. “Not only are we looking at Milky Way from the inside, but it’s even worse than that — our view is blocked by dust, both in clouds and diffuse dust. We can only see about 1,000 -2,000 light years in any direction, even though our galaxy is a 100,000 light years across.”
A digital all-sky mosaic of our view of the Milky Way from Earth, assembled from more than 3,000 individual CCD frames. Credit: Axel Mellinger. Click on image to view a zoomable panorama.
So if you ask, ‘what is the integrated color of the Milky Way,’ we can can’t tell from a picture like the one above, we can only tell what color the local neighborhood is.
“We have had to resort to different techniques, and rather than looking at the Milky Way directly, we look at other galaxies that should be like the Milky Way and we can determine what their color and luminosity are,” Newman said.
Newman, along with Timothy Licquia, a PhD student in physics at Pitt, used images from the Sloan Digital Sky Survey — which contains detailed properties of nearly a million galaxies — and looked for galaxies with similar properties to the Milky Way in regards to total mass and star formation rates. The Milky Way Galaxy should then fall on a plot somewhere within the range of colors of these matching objects.
While the composite color of the Milky Way is snowy-white, our galaxy appears more yellow towards the center and more blue out in the spiral arms.
Newman and Licquia determined the light color temperature of the Milky Way is 4,840 K, which closely matches the light from a standard light bulb with a color temperature of 4,700-5,000K. “It is well within the range our eye can perceive as white—roughly halfway between the light from old-style incandescent light bulbs and the standard spectrum of white on a television,” said Newman. “Our eyes treat both as white.”
The color of new snow is the whitest natural color on Earth. While milk has a more bluish color than snow, the association of our Milky Way to milk has proven to be very appropriate, given the Milky Way’s true color.
Newman even wrote a Haiku about the color:
Look at new spring snow
See the River of Heaven
An hour after dawn
The Milky Way’s color could be on either side of a standard dividing line between red and blue galaxies: relatively red galaxies rarely form new stars and blue galaxies have stars still being born. This adds to the evidence that although the Milky Way is still producing stars, it is “on its way out,” according to Newman. “A few billion years from now, our Galaxy will be a much more boring place, full of middle-aged stars slowly using up their fuel and dying off, but without any new ones to take their place. It will be less interesting for astronomers in other galaxies to look at, too: The Milky Way’s spiral arms will fade into obscurity when there are no more blue stars left.”
VLA at twilight. Image by Dave Finley, courtesy of NRAO/AUI
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The pop culture-rich Very Large Array has been updated with state-of-the-art technology and to befit the VLA’s new capabilities, the National Radio Astronomy Observatory (NRAO) has given it a new name. Recall, back in October 2011, the NRAO asked for the public’s help in choosing a new name, and 17,023 people from 65 different countries responded by sending 23,331 suggestions.
The new name for the world’s most famous radio telescope is the “Karl G. Jansky Very Large Array” to honor the founder of radio astronomy. Radio astronomy enables the study of the Universe via radio waves naturally emitted by objects in space.
The VLA has been part of movie plots, is on album covers, in comic books and video games. It has now been transformed from its original 1970s-vintage technology with the latest equipment, and the NRAO says that the upgrades will greatly increase the VLA’s technical capabilities and scientific impact.
The new name was announced at the American Astronomical Society’s meeting in Austin, Texas. The new name will become official at a re-dedication ceremony at the VLA site in New Mexico on March 31, 2012.
Karl G. Jansky. Credit: NRAO/AUI/NSF
Karl Guthe Jansky (1905-1950) joined Bell Telephone Laboratories in 1928, and was assigned the task of studying radio waves that interfered with the recently-opened transatlantic radiotelephone service.
He designed and built advanced, specialized equipment, and made observations over the entire year of 1932 that allowed him to identify thunderstorms as major sources of radio interference, along with a much weaker, unidentified radio source. Careful study of this “strange hiss-type static” led to the conclusion that the radio waves originated from beyond our Solar System, and indeed came from the center of our Milky Way Galaxy.
His discovery was reported on the front page of the New York Times on May 5, 1933, and published in professional journals. Janksy thus opened an entirely new “window” on the Universe. Astronomers previously had been confined to observing those wavelengths of light that our eyes can see.
NRAO officials say the new name recognizes the VLA’s dramatic new capabilities and its promise for important scientific discoveries in the future.
“When Karl Jansky discovered radio waves coming from the center of the Milky Way Galaxy in 1932, he blazed a scientific trail that fundamentally changed our perception of the Universe. Now, the upgraded VLA will continue that tradition by equipping scientists to address outstanding questions confronting 21st-Century astronomy,” said NRAO Director Fred K.Y. Lo.
“It is particularly appropriate that the upgraded Very Large Array honor the memory and accomplishments of Karl Jansky,” Lo explained, adding that “the new Jansky VLA is by far the most sensitive such radio telescope in the world, as was the receiver and antenna combination that Jansky himself painstakingly developed 80 years ago.”
Lo said they deeply appreciate all the suggestions for a new name, as well as the strong public interest in the VLA and in astronomy. “There was a tremendous amount of thought and creativity that went into the numerous submissions,” he said. “In the end, we decided it was most appropriate to name the telescope after a genuine pioneer who took the first step on the road that led to this powerful scientific facility,” he said.
The Jansky VLA is more than ten times more sensitive to faint radio emission than the original VLA, and covers more than three times more radio frequency range. It will provide astronomers the capability to address key outstanding scientific questions, ranging from the formation of stars and planets in the Milky Way and nearby galaxies, to mapping magnetic fields in galaxies and clusters, and imaging the gas that forms the earliest galaxies.
This enormous section of the Milky Way galaxy is a mosaic of images from NASA's Wide-field Infrared Survey Explorer, or WISE. The constellations Cassiopeia and Cepheus are featured in this 1,000-square degree expanse. Image credit: NASA/JPL-Caltech/UCLA
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Astronomers trying to understand the formation of massive clusters of stars are getting a better idea of how the process works from the latest images and data from the WISE spacecraft. NASA’s Wide-Field Infrared Survey Explorer has captured a vast stretch of nearly a dozen nebulae popping with new star birth, which is helping to narrow the field of possible star-forming scenarios.
“We are trying to understand how huge clusters of stars form at the same time from a large cloud of gas,” said Xavier Koenig from Goddard Space Flight Center, speaking at a press briefing from the American Astronomical Society meeting this week. “We have two possible pictures of how this process works and WISE is helping us piece together the chain of events.”
WISE has mapped the entire sky two times in infrared light, and the astronomers selected a sample of regions to find young stars and map their distributions to try and determine how these large clusters formed. For both possible scenarios, a cluster of stars begin to form at the center of a huge cloud of gas. But what happens next? The first potential situation, called Model 1, is “collect and collapse,” Koenig said, where the stars create a hot bubble of gas which surrounds the stars. “This bubble gathers up material and after a time enough gas builds up that the next generation of stars appears.”
Model 2 is called “chain reaction,” where as bubble of gas progresses outward, stars are continually formed, and there is no gap between the births of stars.
In looking at several of the star-forming nebulae, Koenig and his colleagues noticed a pattern in the spatial arrangement of newborn stars. Some were found lining the blown-out cavities, a phenomenon that had been seen before, but other new stars were seen sprinkled throughout the cavity interiors. The results suggest that stars are born in a successive fashion, one after the other, starting from a core cluster of massive stars and moving steadily outward. This lends support to “chain reaction” star formation theory, and offers new clues about the physics of the process.
The astronomers also found evidence that the bubbles seen in the star-forming clouds can spawn new bubbles. In this scenario, a massive star blasts away surrounding material, which eventually triggers the birth of another star massive enough to carve out its own bubble. A few examples of what may be first- and second-generation bubbles can be seen in the new WISE image.
“Massive stars sweep up and destroy their natal clouds, but they continuously spark new stars to form along the way,” said co-author Dave Leisawitz, the WISE Mission Scientist. “Occasionally a new, massive star forms, perpetuating the sequence of events and giving rise to the dazzling fireworks display seen in this WISE mosaic.”
Since young stars are brighter in infrared, WISE is the perfect telescope to be searching for these massive star-forming regions.
“WISE data is good for this kind of study because the infrared lights up right where these star-forming regions are doing their work – they pop out immediately to your eye,” said Koenig. “I can’t wait to look at more of the WISE sky coverage.”
Technicians work on RXTE in 1995. Credit: NASA/Goddard
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For more than 16 years, 2,200 papers in refereed journals, 92 doctoral theses, and more than 1,000 rapid notifications alerting astronomers around the globe to new astronomical activity, the NASA Rossi X-Ray Timing Explorer is now retired. It sent the last of its data on January 4th of this year and on January 5th the plucky little satellite was decommissioned. If you’re not familiar with Rossi’s activities, then picture sending back images and data on the extreme environments around white dwarfs, neutron stars and black holes… because that’s what made the mission famous.
On December 30, 1995, the mission was launched as XTE from Cape Canaveral, Florida on board a Delta II 7920 rocket. Within weeks it was named in honor of Bruno Rossi, an MIT astronomer and a pioneer of X-ray astronomy and space plasma physics who died in 1993. However, the mission itself didn’t die – it excelled with honors. The entire scientific community recognized the importance of RXTE research and bestowed it with five awards – four Rossi Prizes (1999, 2003, 2006 and 2009) from the High Energy Astrophysics Division of the AAS and the 2004 NWO Spinoza prize, the highest Dutch science award, from the Netherlands Organization for Scientific Research.
On board, the Rossi was three scientific instruments housed in one unit. The first was the Proportional Counter Array (PCA), which was centered on the lower end of the energy band and was crafted by Goddard. The second instrument was the High Energy X-Ray Timing Experiment (HEXTE) that could be aimed at very specific targets and was manufactured by the University of California at San Diego for exploring the upper energy range. The last of the trio was the All-Sky Monitor developed by the Massachusetts Institute of Technology (MIT) in Cambridge. It took in about 80% of the sky during each orbit, delivering astronomers with an unprecedented amount of data on the wide variances of X-Ray sky and allowing them to record bright sources over a period of time as short as a few microseconds up to months. All of this information was taken in over a broad span of energy ranging from 2,000 to 250,000 electron volts.
The Rossi X-Ray Timing Explorer asked little and returned much. Over its operating lifetime it gave us new insight in the life cycles of neutron stars and black holes. Through its eyes we learned about magnetars and discovered the first accreting millisecond pulsar. But that’s not all. The RXTE provided hard evidence which supported Einstein’s theory by observing “frame dragging” in the neighborhood of a black hole. Even though the instrumentation would be considered antique by today’s standards, it certainly served its purpose. “The spacecraft and its instruments had been showing their age, and in the end RXTE had accomplished everything we put it up there to do, and much more,” said Tod Strohmayer, RXTE project scientist at Goddard.
According to the NASA news release, the decision to decommission RXTE followed the recommendations of a 2010 review board tasked to evaluate and rank each of NASA’s operating astrophysics missions. The three and a half ton satellite is expected to return to Earth sometime between the years 2014 and 2023, depending on solar activity. It will have a fiery end… burning out like the superstar that it was. To celebrate its career, the scientific community will hold a special session on RXTE during the 219th meeting of the American Astronomical Society (AAS) in Austin, Texas. The session is scheduled for Tuesday, January 10, at 3 p.m. CST. A press conference on new RXTE results will also be held at the meeting on January 10 at 1:45 p.m. EST. The decision to decommission RXTE followed the recommendations of a 2010 review board tasked to evaluate and rank each of NASA’s operating astrophysics missions. “After two days we listened to verify that none of the systems we turned off had autonomously re-activated, and we’ve heard nothing,” said Deborah Knapp, RXTE mission director at Goddard.
Hydrothermal vents deep in Earth's oceans. Could similar types of vents power the transport of silica and other materials out from Enceladus? Credit: NOAA
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Scientists have recently discovered communities of previously unknown species living on the seafloor near Antarctica clustered around hydrothermal vents. This discovery is certainly exciting for biologists, but it’s also important for astrobiologists. It begs the question — if life can thrive in the deep, dark oceans without sunlight, could similar life thrive elsewhere in our solar system or the universe?
For decades, scientists assumed the deep oceans were barren; sunlight can’t reach the ocean floor, making it an impossible environment for life as we know it to arise. But in 1977, oceanographers from the Scripps Institute discovered hydrothermal vents.
A schematic diagram of deep sea vent chemistry. Image credit: National Oceanic and Atmospheric Administration
These fissures, found along mid-ocean ridges on the seafloor of the Pacific, Atlantic, and Indian Oceans, create a natural, deep-sea plumbing system. Heat and minerals from the Earth’s interior vents out, providing a complex ecosystem that can reach up to 382 degrees Celsius (almost 720 degrees Fahrenheit). These ecosystems can support unique life forms that get their energy not from the Sun but from breaking down chemicals issued from the vents such as hydrogen sulphide.
The latest life forms, discovered in the Antarctic region by teams from the University of Oxford, University of Southampton and British Antarctic Survey, include a new species of yeti crab, starfish, barnacles, sea anemones, and potentially an octopus.
“These findings are yet more evidence of the precious diversity to be found throughout the world’s oceans,” said Professor Rogers of Oxford University’s Department of Zoology. “Everywhere we look, whether it is in the sunlit coral reefs of tropical waters or these Antarctic vents shrouded in eternal darkness, we find unique ecosystems that we need to understand and protect.”
Jupiter's moon Europa. The lines on the surface are breaks in the ice that lie on top of vast oceans. Image credit: NASA/courtesy of nasaimages.org
But it isn’t only biologists studying life on Earth that can benefit from this latest discovery. These peculiar environments on and beneath the seafloor could be a model for the origin of life on Earth and on other planets.
One particular target is Jupiter’s moon Europa. Recent research has confirmed that the moon has vast oceans buried beneath its frozen surface ice; it’s estimated to hold twice as much water as Earth. As such, it is a target for NASA in the search for life. It could be the case that some type of hydrothermal vent system exists on Europa, making its distance from the Sun irrelevant for life.
But just because sulfur or methane-based life on Earth can thrive around deep-ocean vents doesn’t mean the same is true on Europa. The presence of hydrothermal vents depends on geologic activity and a hot interior, neither of which has been confirmed. The possibility remains that light energy from the Sun could travel the distance to the moon and provide shallower portions of the subsurface oceans with life-giving light.
In any case, as scientists discover life in the more extreme environments on Earth, analogies are drawn with other worlds. If life is discovered in hostile parts of our planet, the same could theoretically arise in similar environments on other worlds.
Spirit Mars rover - view from Husband Hill summit. Spirit snapped this view self portrait from the summit of Husband Hill inside Gusev crater on Sol 618 on 28 September 2005. The rovers were never designed or intended to climb mountains. It took more than 1 year for Spirit to scale the Martian mountain. This image was created by an international team of astronomy enthusiasts and appeared on the cover of the 14 November 2005 issue of Aviation Week & Space Technology magazine and the April 2006 issue of Spaceflight magazine. Also selected by Astronomy Picture of the Day (APOD) on 28 November 2005. Credit: Marco Di Lorenzo, Douglas Ellison, Bernhard Braun and Kenneth Kremer. NASA/JPL/Cornell/Aviation Week & Space Technology
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January 2012 marks the 8th anniversary since of the daring landing’s of “Spirit” and “Opportunity” – NASA’s now legendary twin Mars Exploration Rovers (MER), on opposite sides of the Red Planet in January 2004. They proved that early Mars was warm and wet – a key finding in the search for habitats conducive to life beyond Earth.
I asked the leaders of the MER team to share some thoughts celebrating this mind-boggling milestone of “8 Years on Mars” and the legacy of the rovers for the readers of Universe Today. This story focuses on Spirit, first of the trailblazing twin robots, which touched down inside Gusev Crater on Jan. 3, 2004. Opportunity set down three weeks later on the smooth hematite plains of Meridiani Planum.
“Every Sol is a gift. We push the rovers as hard as we can,” Prof. Steve Squyres informed Universe Today for this article commemorating Spirit’s landing. Squyres, of Cornell University, is the Scientific Principal Investigator for the MER mission.
“I seriously thought both Spirit and Opportunity would be finished by the summer of 2004,” Ray Arvidson told Universe Today. Arvidson, of Washington University in St. Louis, is the deputy principal investigator for the MER rovers.
'Calypso' Panorama of Spirit's View from 'Troy'
This full-circle view from the panoramic camera (Pancam) on NASA's Mars Exploration Rover Spirit shows the terrain surrounding the location called "Troy," where Spirit became embedded in soft soil during the spring of 2009. The hundreds of images combined into this view were taken beginning on the 1,906th Martian day (or sol) of Spirit's mission on Mars (May 14, 2009) and ending on Sol 1943 (June 20, 2009). Credit: NASA/JPL-Caltech/Cornell University
click to enlarge
Spirit endured for more than six years and Opportunity is still roving Mars today !
The dynamic robo duo were expected to last a mere three months, or 90 Martian days (sols). In reality, both robots enormously exceeded expectations and accumulated a vast bonus time of exploration and discovery in numerous extended mission phases.
Spirit survived three harsh Martian winters and only succumbed to the Antarctic-like temperatures when she unexpectedly became mired in an unseen sand trap driving beside an ancient volcanic feature named ‘Home Plate’ that prevented the solar arrays from generating life giving power to safeguard critical electronic and computor components.
Spirit was heading towards another pair of volcanic objects named von Braun and Goddard and came within just a few hundred feet when she died.
Everest Panorama from Husband Hill summit
It took Spirit three days, sols 620 to 622 (Oct. 1 to Oct. 3, 2005), to acquire all the images combined into this mosaic, called the "Everest Panorama". Credit: NASA/JPL-Caltech/Cornell University
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“I never thought that we would still be planning sequences for Opportunity today and that we only lost Spirit because of her limited mobility and bad luck of breaking through crusty soil to get bogged down in loose sands,” said Arvidson
By the time of her last dispatch from Mars in March 2010, Spirit had triumphantly traversed the red planets terrain for more than six years of elapsed mission time – some 25 times beyond the three month “warranty” proclaimed by NASA as the mission began back in January 2004.
The "Columbia Hills" in Gusev Crater on Mars
Husband Hill is 3.1 kilometers distant. Spirit took this mosaic of images with the panoramic camera at the beginning of February, 2004, less than a month after landing on Mars. Image credit: NASA/JPL-Caltech/Cornell
“I am feeling pretty good as the MER rover anniversaries approach in that Spirit had an excellent run, helping us understand without a doubt that early Mars had magmatic and volcanic activity that was “wet”, Arvidson explained.
“Magmas interacted with ground water to produce explosive eruptions – at Home Plate, Goddard, von Braun – with volcanic constructs replete with steam vents and perhaps hydrothermal pools.”
Altogether, the six wheeled Spirit drove over 4.8 miles (7.7 kilometers) and the cameras snapped over 128,000 images. NASA hoped the rovers would drive about a quarter mile during the planned 90 Sol mission.
“Milestones like 8 years on Mars always make me look forward rather than looking back,” Squyres told me.
Carbonate-Containing Martian Rocks discovered by Spirit Mars Rover
Spirit collected data in late 2005 which confirmed that the Comanche outcrop contains magnesium iron carbonate, a mineral indicating the past environment was wet and non-acidic, possibly favorable to life. This view was captured during Sol 689 on Mars (Dec. 11, 2005). The find at Comanche is the first unambiguous evidence from either Spirit or Opportunity for a past Martian environment that may have been more favorable to life than the wet but acidic conditions indicated by the rovers' earlier finds. Credit: NASA/JPL-Caltech/Cornell University
Spirit became the first robotic emissary from humanity to climb a mountain beyond Earth, namely Husband Hill, a task for which she was not designed.
“No one expected the rovers to last so long,” said Rob Manning to Universe Today. Manning, of NASA’s Jet Propulsion laboratory, Pasadena, CA. was the Mars Rover Spacecraft System Engineering team lead for Entry, Descent and Landing (EDL)
“Spirit surmounted many obstacles, including summiting a formidable hill her designers never intended her to attempt.”
“Spirit, her designers, her builders, her testers, her handlers and I have a lot to be thankful for,” Manning told me.
After departing the Gusev crater landing pad, Spirit traversed over 2 miles to reach Husband Hill. In order to scale the hill, the team had to create a driving plan from scratch with no playbook because no one ever figured that such a mouthwatering opportunity to be offered.
Spirit Rover traverse map from Gusev Crater landing site to Home Plate: 2004 to 2011
It took over a year to ascend to the hill’s summit. But the team was richly rewarded with a science bonanza of evidence for flowing liquid water on ancient Mars.
Spirit then descended down the other side of the hill to reach the feature dubbed Home Plate where she now rests and where she found extensive evidence of deposits of nearly pure silica, explosive volcanism and hot springs all indicative of water on Mars billions of years ago.
“Spirit’s big scientific accomplishments are the silica deposits at Home Plate, the carbonates at Comanche, and all the evidence for hydrothermal systems and explosive volcanism, Squyres explained. “ What we’ve learned is that early Mars at Spirit’s site was a hot, violent place, with hot springs, steam vents, and volcanic explosions. It was extraordinarily different from the Mars of today.”
“We’ve still got a lot of exploring to do [with Opportunity], but we’re doing it with a vehicle that was designed for a 90-sol mission,” Squyres concluded. “That means that ever sol is a gift at this point, and we have to push the rover and ourselves as hard as we can.”
NASA concluded the last attempt to communicate with Spirit in a transmission on May 25, 2011.
Spirit Rover traverse map from Husband Hill to resting place at Home Plate: 2004 to 2011The Last View Ever from Spirit rover on Mars
Spirit’s last panorama from Gusev Crater was taken during February 2010 before her death from extremely low temperatures during her 4th Martian winter. Spirit was just 500 feet from her next science target - dubbed Von Braun – at center, with Columbia Hills as backdrop.
Mosaic Credit: Marco De Lorenzo/ Kenneth Kremer/ NASA/JPL/Cornell University
Mosaic featured on Astronomy Picture of the Day (APOD) on 30 May 2011 - http://apod.nasa.gov/apod/ap110530.html
Meanwhile, the Curiosity Mars Science Lab rover, NASA’s next Red Planet explorer, continues her interplanetary journey on course for a 6 August 2012 landing at Gale Crater.
Jan 11: Free Lecture by Ken Kremer at the Franklin Institute, Philadelphia, PA at 8 PM for the Rittenhouse Astronomical Society. Topic: Mars & Vesta in 3 D – Plus Search for Life & GRAIL
This is going to be one of the “how we know what we know” kind of shows. How do scientist determine the age of things? How do we know the age of everything from stone tools, to the age of the Earth, to the age of the very Universe.
You can watch us record Astronomy Cast live every Monday at 12:00 pm PDT (3:00 pm EDT, 2000 GMT). Make sure you circle Fraser on Google+ to see it show up in the feed. You can also see it live over on our YouTube channel.
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Gemini South laser guide star system propagating as the Milky Way rises.
[/caption]When it comes to astrophotography, most of us would think that space-based telescopes like the Hubble are the epitome of imagining. However, there’s something new to be said about being “grounded”. On December 16, 2011, the Gemini South telescope in Chile revealed its first wide-field, ultra-sharp image… the product of a decade of hard work. By employing a new generation of adaptive optics (AO), the scope produced an incredible look into the densely concentrated globular cluster, NGC 288, and captured stars at close to the theoretical resolution limit of Gemini’s massive 8-meter mirror.
The Gemini Multi-conjugate adaptive optics System (GeMS for short), produced an incredible vision… one of incredible resolution. This new system will allow astronomers to study galactic centers and their black holes – as well as the life patterns of singular stars – with incredible clarity. It’s the largest amount of area ever captured in a single observation – one that’s ten times larger than any adaptive optics systems has ever been able to capture before. It has cause quite a stir in the astronomical community. When Space Telescope Science Institute director Matt Mountain saw the first light image, he praised the GeMS instrument team: “Incredible! You have truly revolutionized ground-based astronomy!”
As the director of the Gemini Observatory, Dr. Mountain was around when the project first began 10 years ago. He was responsible for assembling the team, including Francois Rigaut as the lead scientist to develop the GeMS instrument. And, Rigaut was there for first light… “We couldn’t believe our eyes!” Rigaut recalls. “The image of NGC 288 revealed thousands of pinpoint stars. Its resolution is Hubble-quality – and from the ground this is phenomenal.” Of course, one of the most amazing aspects of the image was how widely spaced the stars appeared, to which Rigaut comments: “This is somewhat uncharted territory: no one has ever made images so large with such a high angular resolution.”
Gemini South’s “first light” image from GeMS/GSAOI shows extreme detail in the central part of the globular star cluster NGC 288. The image, taken at 1.65 microns (H band) on December 16, 2011, has a field-of-view 87 x 87 arcseconds. The average full-width at half-maximum is slightly below 0.080 arcsecond, with a variation of 0.002 arcsecond across the entire field of the image. Exposure time was 13 minutes. Insets on the right show a detail of the image (top), a comparison of the same region with classical AO (middle; this assumes using the star at the upper right corner as the guide star), and seeing-limited observations (bottom). The pixel size in the latter was chosen to optimize the signal-to-noise ratio while not degrading the intrinsic angular resolution of the image. North is up, East is right.
Even though this is an incredible insight, some members of the scientific team which use the Gemini telescope are a bit more reserved in their comments. According to University of Toronto astronomer Roberto Abraham, one of a community of hundreds of astronomers worldwide who uses the 8-meter Gemini telescopes for cutting-edge research: “This is fan-freaking-tastic!!!!!!!” Exuberant? Of course! Even the environmental conditions remained as perfect as they could be for the first run of the GeMS equipment. “We were lucky to have clear weather and stable atmospheric conditions that night,” said Gemini AO scientist Benoit Neichel. “Even despite interruptions of the laser propagation due to satellites and planes passing by, we obtained our first image with the system. It was surprisingly crisp and large, with an exquisitely uniform image quality.”
How is it accomplished? GeMS employs five laser guide stars, three deformable mirrors and a full arsenal of computers to provide a near diffraction limited image to the Gemini South Adaptive Optics Imager (GSAOI, built by the Australian National University) and the infrared-sensitive imager attached to it. This means the smallest detail that can be resolved measures about 0.04 to 0.06 arcsecond over a field of 85 arcseconds squared. Compared to 0.5 arcsecond “seeing limited” at a good viewing location, that’s phenomenal! Once resolution was solved, the next problem was extending the field of view through a technique called Multi-Conjugate Adaptive Optics (MCAO) – an endeavor which borrowed technology from other scientific fields, such as medical imaging.
“MCAO is game-changing,” Abraham said. “It’s going to propel Gemini to the next echelon of discovery space as well as lay a foundation for the next generation of extremely large telescopes. Gemini is going to be delivering amazing science while paving the way for the future.”
