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Tucson, AZ, United States
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News Article | May 3, 2017
Site: www.chromatographytechniques.com

NASA's SOFIA aircraft, a 747 loaded with a 2.5-meter telescope in the back and stripped of most creature comforts in the front, took a big U-turn over the Pacific west of Mexico. The Stratospheric Observatory for Infrared Astronomy aircraft was just beginning the second half of an overnight mission on Jan. 28, 2015. It turned north for a flight all the way to western Oregon, then back home to NASA's Armstrong Flight Research Center in Palmdale, California. Along the way, pilots steered the plane to aim the telescope at a nearby star. Iowa State University's Massimo Marengo and other astronomers were on board to observe the mission and collect infrared data about the star. That star is called epsilon Eridani. It's about 10 light years away from the sun. It's similar to our sun, but one-fifth the age. And astronomers believe it can tell them a lot about the development of our solar system. Marengo, an Iowa State associate professor of physics and astronomy, and other astronomers have been studying the star and its planetary system since 2004. In a 2009 scientific paper, the astronomers used data from NASA's Spitzer Space Telescope to describe the star's disk of fine dust and debris left over from the formation of planets and the collisions of asteroids and comets. They reported the disk contained separate belts of asteroids, similar to the asteroid and Kuiper belts of our solar system. Subsequent studies by other astronomers questioned that finding. A new scientific paper, just published online by The Astronomical Journal, uses SOFIA and Spitzer data to confirm there are separate inner and outer disk structures. The astronomers report further studies will have to determine if the inner disk includes one or two debris belts. Kate Su, an associate astronomer at the University of Arizona and the university's Steward Observatory, is the paper's lead author. Marengo is one of the paper's nine co-authors. Marengo said the findings are important because they confirm epsilon Eridani is a good model of the early days of our solar system and can provide hints at how our solar system evolved. "This star hosts a planetary system currently undergoing the same cataclysmic processes that happened to the solar system in its youth, at the time in which the moon gained most of its craters, Earth acquired the water in its oceans, and the conditions favorable for life on our planet were set," Marengo wrote in a summary of the project. A major contributor to the new findings was data taken during that January 2015 flight of SOFIA. Marengo joined Su on the cold and noisy flight at 45,000 feet, above nearly all of the atmospheric water vapor that absorbs the infrared light that astronomers need to see planets and planetary debris. Determining the structure of the disk was a complex effort that took several years and detailed computer modeling. The astronomers had to separate the faint emission of the disk from the much brighter light coming from the star. "But we can now say with great confidence that there is a separation between the star's inner and outer belts," Marengo said. "There is a gap most likely created by planets. We haven't detected them yet, but I would be surprised if they are not there. Seeing them will require using the next-generation instrumentation, perhaps NASA's 6.5-meter James Webb Space Telescope scheduled for launch in October 2018." That's a lot of time and attention on one nearby star and its debris disk. But Marengo said it really is taking astronomers back in time. "The prize at the end of this road is to understand the true structure of epsilon Eridani's out-of-this-world disk, and its interactions with the cohort of planets likely inhabiting its system," Marengo wrote in a newsletter story about the project. "SOFIA, by its unique ability of capturing infrared light in the dry stratospheric sky, is the closest we have to a time machine, revealing a glimpse of Earth's ancient past by observing the present of a nearby young sun."


News Article | May 2, 2017
Site: www.eurekalert.org

AMES, Iowa - NASA's SOFIA aircraft, a 747 loaded with a 2.5-meter telescope in the back and stripped of most creature comforts in the front, took a big U-turn over the Pacific west of Mexico. The Stratospheric Observatory for Infrared Astronomy aircraft was just beginning the second half of an overnight mission on Jan. 28, 2015. It turned north for a flight all the way to western Oregon, then back home to NASA's Armstrong Flight Research Center in Palmdale, California. Along the way, pilots steered the plane to aim the telescope at a nearby star. Iowa State University's Massimo Marengo and other astronomers were on board to observe the mission and collect infrared data about the star. That star is called epsilon Eridani. It's about 10 light years away from the sun. It's similar to our sun, but one-fifth the age. And astronomers believe it can tell them a lot about the development of our solar system. Marengo, an Iowa State associate professor of physics and astronomy, and other astronomers have been studying the star and its planetary system since 2004. In a 2009 scientific paper, the astronomers used data from NASA's Spitzer Space Telescope to describe the star's disk of fine dust and debris left over from the formation of planets and the collisions of asteroids and comets. They reported the disk contained separate belts of asteroids, similar to the asteroid and Kuiper belts of our solar system. Subsequent studies by other astronomers questioned that finding. A new scientific paper, just published online by The Astronomical Journal, uses SOFIA and Spitzer data to confirm there are separate inner and outer disk structures. The astronomers report further studies will have to determine if the inner disk includes one or two debris belts. Kate Su, an associate astronomer at the University of Arizona and the university's Steward Observatory, is the paper's lead author. Marengo is one of the paper's nine co-authors. Marengo said the findings are important because they confirm epsilon Eridani is a good model of the early days of our solar system and can provide hints at how our solar system evolved. "This star hosts a planetary system currently undergoing the same cataclysmic processes that happened to the solar system in its youth, at the time in which the moon gained most of its craters, Earth acquired the water in its oceans, and the conditions favorable for life on our planet were set," Marengo wrote in a summary of the project. A major contributor to the new findings was data taken during that January 2015 flight of SOFIA. Marengo joined Su on the cold and noisy flight at 45,000 feet, above nearly all of the atmospheric water vapor that absorbs the infrared light that astronomers need to see planets and planetary debris. Determining the structure of the disk was a complex effort that took several years and detailed computer modeling. The astronomers had to separate the faint emission of the disk from the much brighter light coming from the star. "But we can now say with great confidence that there is a separation between the star's inner and outer belts," Marengo said. "There is a gap most likely created by planets. We haven't detected them yet, but I would be surprised if they are not there. Seeing them will require using the next-generation instrumentation, perhaps NASA's 6.5-meter James Webb Space Telescope scheduled for launch in October 2018." That's a lot of time and attention on one nearby star and its debris disk. But Marengo said it really is taking astronomers back in time. "The prize at the end of this road is to understand the true structure of epsilon Eridani's out-of-this-world disk, and its interactions with the cohort of planets likely inhabiting its system," Marengo wrote in a newsletter story about the project. "SOFIA, by its unique ability of capturing infrared light in the dry stratospheric sky, is the closest we have to a time machine, revealing a glimpse of Earth's ancient past by observing the present of a nearby young sun."


News Article | May 3, 2017
Site: www.futurity.org

Thanks to key observations made with the assistance of NASA’s Stratospheric Observatory for Infrared Astronomy (SOFIA) aircraft, astronomers confirm that a recently discovered star, called epsilon Eridani, mirrors our own solar system in a number of ways—only much earlier in its history. The SOFIA aircraft, a 747 loaded with a 2.5-meter telescope in the back, was just beginning the second half of an overnight mission on January 28, 2015. It turned north for a flight all the way to western Oregon, then back home to NASA’s Armstrong Flight Research Center in Palmdale, California. Along the way, pilots steered the plane to aim the telescope at a nearby star. Massimo Marengo and other astronomers were on board to observe the mission and collect infrared data about the star. Called epsilon Eridani, it’s about 10 light years away from the sun. It’s similar to our sun, but one-fifth the age. And astronomers believe it can tell them a lot about the development of our solar system. Marengo, associate professor of physics and astronomy at Iowa State University, and other astronomers have been studying the star and its planetary system since 2004. In a 2009 scientific paper, the astronomers used data from NASA’s Spitzer Space Telescope to describe the star’s disk of fine dust and debris left over from the formation of planets and the collisions of asteroids and comets. They reported the disk contained separate belts of asteroids, similar to the asteroid and Kuiper belts of our solar system. Subsequent studies by other astronomers questioned that finding. The new paper, available online in The Astronomical Journal, uses SOFIA and Spitzer data to confirm there are separate inner and outer disk structures. The astronomers report further studies will have to determine if the inner disk includes one or two debris belts. Marengo says the findings are important because they confirm epsilon Eridani is a good model of the early days of our solar system and can provide hints at how our solar system evolved. “This star hosts a planetary system currently undergoing the same cataclysmic processes that happened to the solar system in its youth, at the time in which the moon gained most of its craters, Earth acquired the water in its oceans, and the conditions favorable for life on our planet were set,” Marengo writes in a summary of the project. A major contributor to the new findings was data taken during that January 2015 flight of SOFIA. Marengo joined Su on the cold and noisy flight at 45,000 feet, above nearly all of the atmospheric water vapor that absorbs the infrared light that astronomers need to see planets and planetary debris. Determining the structure of the disk was a complex effort that took several years and detailed computer modeling. The astronomers had to separate the faint emission of the disk from the much brighter light coming from the star. “But we can now say with great confidence that there is a separation between the star’s inner and outer belts,” Marengo says. “There is a gap most likely created by planets. We haven’t detected them yet, but I would be surprised if they are not there. Seeing them will require using the next-generation instrumentation, perhaps NASA’s 6.5-meter James Webb Space Telescope scheduled for launch in October 2018.” That’s a lot of time and attention on one nearby star and its debris disk. But Marengo says it really is taking astronomers back in time. “The prize at the end of this road is to understand the true structure of epsilon Eridani’s out-of-this-world disk, and its interactions with the cohort of planets likely inhabiting its system,” Marengo writes in a newsletter story about the project. “SOFIA, by its unique ability of capturing infrared light in the dry stratospheric sky, is the closest we have to a time machine, revealing a glimpse of Earth’s ancient past by observing the present of a nearby young sun.” Kate Su, an associate astronomer at the University of Arizona and the university’s Steward Observatory, is the paper’s lead author.


The Stratospheric Observatory for Infrared Astronomy aircraft was just beginning the second half of an overnight mission on Jan. 28, 2015. It turned north for a flight all the way to western Oregon, then back home to NASA's Armstrong Flight Research Center in Palmdale, California. Along the way, pilots steered the plane to aim the telescope at a nearby star. Iowa State University's Massimo Marengo and other astronomers were on board to observe the mission and collect infrared data about the star. That star is called epsilon Eridani. It's about 10 light years away from the sun. It's similar to our sun, but one-fifth the age. And astronomers believe it can tell them a lot about the development of our solar system. Marengo, an Iowa State associate professor of physics and astronomy, and other astronomers have been studying the star and its planetary system since 2004. In a 2009 scientific paper, the astronomers used data from NASA's Spitzer Space Telescope to describe the star's disk of fine dust and debris left over from the formation of planets and the collisions of asteroids and comets. They reported the disk contained separate belts of asteroids, similar to the asteroid and Kuiper belts of our solar system. Subsequent studies by other astronomers questioned that finding. A new scientific paper, just published online by The Astronomical Journal, uses SOFIA and Spitzer data to confirm there are separate inner and outer disk structures. The astronomers report further studies will have to determine if the inner disk includes one or two debris belts. Kate Su, an associate astronomer at the University of Arizona and the university's Steward Observatory, is the paper's lead author. Marengo is one of the paper's nine co-authors. Marengo said the findings are important because they confirm epsilon Eridani is a good model of the early days of our solar system and can provide hints at how our solar system evolved. "This star hosts a planetary system currently undergoing the same cataclysmic processes that happened to the solar system in its youth, at the time in which the moon gained most of its craters, Earth acquired the water in its oceans, and the conditions favorable for life on our planet were set," Marengo wrote in a summary of the project. A major contributor to the new findings was data taken during that January 2015 flight of SOFIA. Marengo joined Su on the cold and noisy flight at 45,000 feet, above nearly all of the atmospheric water vapor that absorbs the infrared light that astronomers need to see planets and planetary debris. Determining the structure of the disk was a complex effort that took several years and detailed computer modeling. The astronomers had to separate the faint emission of the disk from the much brighter light coming from the star. "But we can now say with great confidence that there is a separation between the star's inner and outer belts," Marengo said. "There is a gap most likely created by planets. We haven't detected them yet, but I would be surprised if they are not there. Seeing them will require using the next-generation instrumentation, perhaps NASA's 6.5-meter James Webb Space Telescope scheduled for launch in October 2018." That's a lot of time and attention on one nearby star and its debris disk. But Marengo said it really is taking astronomers back in time. "The prize at the end of this road is to understand the true structure of epsilon Eridani's out-of-this-world disk, and its interactions with the cohort of planets likely inhabiting its system," Marengo wrote in a newsletter story about the project. "SOFIA, by its unique ability of capturing infrared light in the dry stratospheric sky, is the closest we have to a time machine, revealing a glimpse of Earth's ancient past by observing the present of a nearby young sun." Explore further: Solar System's Young Twin Has Two Asteroid Belts More information: Kate Y. L. Su et al, The Inner 25 au Debris Distribution in theEri System, The Astronomical Journal (2017). DOI: 10.3847/1538-3881/aa696b


News Article | April 18, 2017
Site: phys.org

After combining this staggering number of spectra—recorded patterns of wavelengths revealing clues about the nature of a cosmic target—UA astronomers Huanian Zhang and Dennis Zaritsky report the first detections of diffuse hydrogen wafting about in a vast halo surrounding the Milky Way. Such a halo had been postulated based on what astronomers knew about other galaxies, but never directly observed. Astronomers have long known that the most prominent features of a typical spiral galaxy such as our Milky Way—a central bulge surrounded by a disk and spiral arms—account only for the lesser part of its mass. The bulk of the missing mass is suspected to lie in so-called dark matter, a postulated but not yet directly observed form of matter believed to account for the majority of matter in the universe. Dark matter emits no electromagnetic radiation of any kind, nor does it interact with "normal" matter (which astronomers call baryonic matter), and is therefore invisible and undetectable through direct imaging. The dark matter of a typical galaxy is thought to reside in a more or less spherical halo that extends 10 to 30 times farther out than the distance between the center of our galaxy and the sun, according to Zaritsky, a professor in the UA's Department of Astronomy and deputy director of the UA's Steward Observatory. "We infer its existence through dynamical simulations of galaxies," Zaritsky explains. "And because the ratio of normal matter to dark matter is now very well known, for example from measuring the cosmic microwave background, we have a pretty good idea of how much baryonic matter should be in the halo. But when we add all the things we can see with our instruments, we get only about half of what we expect, so there has to be a lot of baryonic matter waiting to be detected." By combining such a large number of spectra, Zaritsky and Zhang, a postdoctoral fellow in the Department of Astronomy/Steward Observatory, covered a large portion of space surrounding the Milky Way and found that diffuse hydrogen gas engulfs the entire galaxy, which would account for a large part of the galaxy's baryonic mass. "It's like peering through a veil," Zaritsky said. "We see diffuse hydrogen in every direction we look." He pointed out that this is not the first time gas has been detected in halos around galaxies, but in those instances, the hydrogen is in a different physical state. "There are cloudlets of hydrogen in the galaxy halo, which we have known about for a long time, called high-velocity clouds," Zaritsky said. "Those have been detected through radio observations, and they're really clouds—you see an edge, and they're moving. But the total mass of those is small, so they couldn't be the dominant form of hydrogen in the halo." Since observing our own galaxy is a bit like trying to see what an unfamiliar house looks like while being confined to a room inside, astronomers rely on computer simulations and observations of other galaxies to get an idea of what the Milky Way might look like to an alien observer millions of light-years away. For their study, scheduled for advance online publication on Nature Astronomy's website on Apr. 18, the researchers sifted through the public databases of the Sloan Digital Sky Survey and looked for spectra taken by other scientists of galaxies outside our Milky Way in a narrow spectral line called hydrogen alpha. Seeing this line in a spectrum tells of the presence of a particular state of hydrogen that is different from the vast majority of hydrogen found in the universe. Unlike on Earth, where hydrogen occurs as a gas consisting of molecules of two hydrogen atoms bound together, hydrogen exists as single atoms in outer space, and those can be positively or negatively charged, or neutral. Neutral hydrogen constitutes a small minority compared to its ionized (positive) form, which constitutes more than 99.99 percent of the gas spanning the intergalactic gulfs of the universe. Unless neutral hydrogen atoms are being energized by something, they are extremely difficult to detect and therefore remain invisible to most observational approaches, which is why their presence in the Milky Way's halo had eluded astronomers until now. Even in other galaxies, halos are difficult to pin down. "You don't just see a pretty picture of a halo around a galaxy," Zaritsky said. "We infer the presence of galactic halos from numerical simulations of galaxies and from what we know about how they form and interact." Zaritsky explained that based on those simulations, scientists would have predicted the presence of large amounts of hydrogen gas stretching far out from the center of the Milky Way, but remaining associated with the galaxy, and the data collected in this study confirm the presence of just that. "The gas we detected is not doing anything very noticeable," he said. "It is not spinning so rapidly as to indicate that it's in the process of being flung out of the galaxy, and it does not appear to be falling inwards toward the galactic center, either." One of the challenges in this study was to know whether the observed hydrogen was indeed in a halo outside the Milky Way, and not just part of the galactic disk itself, Zaritsky said. "When you see things everywhere, they could be very close to us, or they could be very far away," he said. "You don't know." The answer to this question, too, was in the "trees," the more than 700,000 spectral analyses scattered across the galaxy. If the hydrogen gas were confined to the disk of the galaxy, our solar system would be expected to "float" inside of it like a ship in a slowly churning maelstrom, orbiting the galactic center. And just like the ship drifting with the current, very little relative movement would be expected between our solar system and the ocean of hydrogen. If, on the other hand, it surrounded the spinning galaxy in a more or less stationary halo, the researchers expected that wherever they looked, they should find a predictable pattern of relative motion with respect to our solar system. "Indeed, in one direction, we see the gas coming toward us, and the opposite direction, we see it moving away from us," Zaritsky said. "This tells us that the gas is not in the disk of our galaxy, but has to be out in the halo." Next, the researchers want to look at even more spectra to better constrain the distribution around the sky and the motions of the gas in the halo. They also plan to search for other spectral lines, which may help better understand the physical state such as temperature and density of the gas. Explore further: Astronomers observe early stages of Milky Way-like galaxies in distant universe More information: The Galaxy's veil of excited hydrogen, Nature Astronomy (2017). nature.com/articles/doi:10.1038/s41550-017-0103


News Article | April 24, 2017
Site: www.futurity.org

Observing 732,225 galaxies with the 2.5-meter telescope of the Sloan Digital Sky Survey has revealed the veil of diffuse hydrogen gas enshrouding the Milky Way. After combining this staggering number of spectra—recorded patterns of wavelengths revealing clues about the nature of a cosmic target—astronomers Huanian Zhang and Dennis Zaritsky report the first detections of diffuse hydrogen wafting about in a vast halo surrounding the Milky Way. Such a halo had been postulated based on what astronomers knew about other galaxies, but never directly observed. “It’s like peering through a veil. We see diffuse hydrogen in every direction we look.” Astronomers have long known that the most prominent features of a typical spiral galaxy such as our Milky Way—a central bulge surrounded by a disk and spiral arms—account only for the lesser part of its mass. The bulk of the missing mass is suspected to lie in so-called dark matter, a postulated but not yet directly observed form of matter believed to account for the majority of matter in the universe. Dark matter emits no electromagnetic radiation of any kind, nor does it interact with “normal” matter (which astronomers call baryonic matter), and is therefore invisible and undetectable through direct imaging. The dark matter of a typical galaxy is thought to reside in a more or less spherical halo that extends 10 to 30 times farther out than the distance between the center of our galaxy and the sun, according to Zaritsky, a professor in the the University of Arizona’s astronomy department and deputy director of its Steward Observatory. “We infer its existence through dynamical simulations of galaxies,” Zaritsky explains. “And because the ratio of normal matter to dark matter is now very well known, for example from measuring the cosmic microwave background, we have a pretty good idea of how much baryonic matter should be in the halo. But when we add all the things we can see with our instruments, we get only about half of what we expect, so there has to be a lot of baryonic matter waiting to be detected.” By combining such a large number of spectra, Zaritsky and Zhang, a postdoctoral fellow in the department of astronomy/Steward Observatory, covered a large portion of space surrounding the Milky Way and found that diffuse hydrogen gas engulfs the entire galaxy, which would account for a large part of the galaxy’s baryonic mass. “It’s like peering through a veil,” Zaritsky says. “We see diffuse hydrogen in every direction we look.” He points out that this is not the first time gas has been detected in halos around galaxies, but in those instances, the hydrogen is in a different physical state. “There are cloudlets of hydrogen in the galaxy halo, which we have known about for a long time, called high-velocity clouds,” Zaritsky says. “Those have been detected through radio observations, and they’re really clouds—you see an edge, and they’re moving. But the total mass of those is small, so they couldn’t be the dominant form of hydrogen in the halo.” How aliens would see us Since observing our own galaxy is a bit like trying to see what an unfamiliar house looks like while being confined to a room inside, astronomers rely on computer simulations and observations of other galaxies to get an idea of what the Milky Way might look like to an alien observer millions of light-years away. Milky Way is full of wandering stars For their study, published in the journal Nature Astronomy, the researchers sifted through the public databases of the Sloan Digital Sky Survey and looked for spectra taken by other scientists of galaxies outside our Milky Way in a narrow spectral line called hydrogen alpha. Seeing this line in a spectrum tells of the presence of a particular state of hydrogen that is different from the vast majority of hydrogen found in the universe. Unlike on Earth, where hydrogen occurs as a gas consisting of molecules of two hydrogen atoms bound together, hydrogen exists as single atoms in outer space, and those can be positively or negatively charged, or neutral. Neutral hydrogen constitutes a small minority compared to its ionized (positive) form, which constitutes more than 99.99 percent of the gas spanning the intergalactic gulfs of the universe. Unless neutral hydrogen atoms are being energized by something, they are extremely difficult to detect and therefore remain invisible to most observational approaches, which is why their presence in the Milky Way’s halo had eluded astronomers until now. Even in other galaxies, halos are difficult to pin down. “You don’t just see a pretty picture of a halo around a galaxy,” Zaritsky says. “We infer the presence of galactic halos from numerical simulations of galaxies and from what we know about how they form and interact.” Zaritsky explains that based on those simulations, scientists would have predicted the presence of large amounts of hydrogen gas stretching far out from the center of the Milky Way, but remaining associated with the galaxy, and the data collected in this study confirm the presence of just that. “The gas we detected is not doing anything very noticeable,” he says. “It is not spinning so rapidly as to indicate that it’s in the process of being flung out of the galaxy, and it does not appear to be falling inwards toward the galactic center, either.” Outside the disk One of the challenges in this study was to know whether the observed hydrogen was indeed in a halo outside the Milky Way, and not just part of the galactic disk itself, Zaritsky says. “When you see things everywhere, they could be very close to us, or they could be very far away,” he says. “You don’t know.” The answer to this question, too, was in the more than 700,000 spectral analyses scattered across the galaxy. If the hydrogen gas were confined to the disk of the galaxy, our solar system would be expected to “float” inside of it like a ship in a slowly churning maelstrom, orbiting the galactic center. And just like the ship drifting with the current, very little relative movement would be expected between our solar system and the ocean of hydrogen. Did hydrogen make rivers flow on Mars? If, on the other hand, it surrounded the spinning galaxy in a more or less stationary halo, the researchers expected that wherever they looked, they should find a predictable pattern of relative motion with respect to our solar system. “Indeed, in one direction, we see the gas coming toward us, and the opposite direction, we see it moving away from us,” Zaritsky says. “This tells us that the gas is not in the disk of our galaxy, but has to be out in the halo.” Next, the researchers want to look at even more spectra to better constrain the distribution around the sky and the motions of the gas in the halo. They also plan to search for other spectral lines, which may help better understand the physical state such as temperature and density of the gas. Source: University of Arizona The post Vast halo of hydrogen surrounds Milky Way appeared first on Futurity.


News Article | April 18, 2017
Site: www.rdmag.com

Sometimes it takes a lot of trees to see the forest. In the case of the latest discovery made by astronomers at the University of Arizona, exactly 732,225. Except that in this case, the "forest" is a veil of diffuse hydrogen gas enshrouding the Milky Way, and each "tree" is another galaxy observed with the 2.5-meter telescope of the Sloan Digital Sky Survey. After combining this staggering number of spectra -- recorded patterns of wavelengths revealing clues about the nature of a cosmic target -- UA astronomers Huanian Zhang and Dennis Zaritsky report the first detections of diffuse hydrogen wafting about in a vast halo surrounding the Milky Way. Such a halo had been postulated based on what astronomers knew about other galaxies, but never directly observed. Astronomers have long known that the most prominent features of a typical spiral galaxy such as our Milky Way -- a central bulge surrounded by a disk and spiral arms -- account only for the lesser part of its mass. The bulk of the missing mass is suspected to lie in so-called dark matter, a postulated but not yet directly observed form of matter believed to account for the majority of matter in the universe. Dark matter emits no electromagnetic radiation of any kind, nor does it interact with "normal" matter (which astronomers call baryonic matter), and is therefore invisible and undetectable through direct imaging. The dark matter of a typical galaxy is thought to reside in a more or less spherical halo that extends 10 to 30 times farther out than the distance between the center of our galaxy and the sun, according to Zaritsky, a professor in the UA's Department of Astronomy and deputy director of the UA's Steward Observatory. "We infer its existence through dynamical simulations of galaxies," Zaritsky explains. "And because the ratio of normal matter to dark matter is now very well known, for example from measuring the cosmic microwave background, we have a pretty good idea of how much baryonic matter should be in the halo. But when we add all the things we can see with our instruments, we get only about half of what we expect, so there has to be a lot of baryonic matter waiting to be detected." By combining such a large number of spectra, Zaritsky and Zhang, a postdoctoral fellow in the Department of Astronomy/Steward Observatory, covered a large portion of space surrounding the Milky Way and found that diffuse hydrogen gas engulfs the entire galaxy, which would account for a large part of the galaxy's baryonic mass. "It's like peering through a veil," Zaritsky said. "We see diffuse hydrogen in every direction we look." He pointed out that this is not the first time gas has been detected in halos around galaxies, but in those instances, the hydrogen is in a different physical state. "There are cloudlets of hydrogen in the galaxy halo, which we have known about for a long time, called high-velocity clouds," Zaritsky said. "Those have been detected through radio observations, and they're really clouds -- you see an edge, and they're moving. But the total mass of those is small, so they couldn't be the dominant form of hydrogen in the halo." Since observing our own galaxy is a bit like trying to see what an unfamiliar house looks like while being confined to a room inside, astronomers rely on computer simulations and observations of other galaxies to get an idea of what the Milky Way might look like to an alien observer millions of light-years away. For their study, scheduled for advance online publication on Nature Astronomy's website on Apr. 18, the researchers sifted through the public databases of the Sloan Digital Sky Survey and looked for spectra taken by other scientists of galaxies outside our Milky Way in a narrow spectral line called hydrogen alpha. Seeing this line in a spectrum tells of the presence of a particular state of hydrogen that is different from the vast majority of hydrogen found in the universe. Unlike on Earth, where hydrogen occurs as a gas consisting of molecules of two hydrogen atoms bound together, hydrogen exists as single atoms in outer space, and those can be positively or negatively charged, or neutral. Neutral hydrogen constitutes a small minority compared to its ionized (positive) form, which constitutes more than 99.99 percent of the gas spanning the intergalactic gulfs of the universe. Unless neutral hydrogen atoms are being energized by something, they are extremely difficult to detect and therefore remain invisible to most observational approaches, which is why their presence in the Milky Way's halo had eluded astronomers until now. Even in other galaxies, halos are difficult to pin down. "You don't just see a pretty picture of a halo around a galaxy," Zaritsky said. "We infer the presence of galactic halos from numerical simulations of galaxies and from what we know about how they form and interact." Zaritsky explained that based on those simulations, scientists would have predicted the presence of large amounts of hydrogen gas stretching far out from the center of the Milky Way, but remaining associated with the galaxy, and the data collected in this study confirm the presence of just that. "The gas we detected is not doing anything very noticeable," he said. "It is not spinning so rapidly as to indicate that it's in the process of being flung out of the galaxy, and it does not appear to be falling inwards toward the galactic center, either." One of the challenges in this study was to know whether the observed hydrogen was indeed in a halo outside the Milky Way, and not just part of the galactic disk itself, Zaritsky said. "When you see things everywhere, they could be very close to us, or they could be very far away," he said. "You don't know." The answer to this question, too, was in the "trees," the more than 700,000 spectral analyses scattered across the galaxy. If the hydrogen gas were confined to the disk of the galaxy, our solar system would be expected to "float" inside of it like a ship in a slowly churning maelstrom, orbiting the galactic center. And just like the ship drifting with the current, very little relative movement would be expected between our solar system and the ocean of hydrogen. If, on the other hand, it surrounded the spinning galaxy in a more or less stationary halo, the researchers expected that wherever they looked, they should find a predictable pattern of relative motion with respect to our solar system. "Indeed, in one direction, we see the gas coming toward us, and the opposite direction, we see it moving away from us," Zaritsky said. "This tells us that the gas is not in the disk of our galaxy, but has to be out in the halo." Next, the researchers want to look at even more spectra to better constrain the distribution around the sky and the motions of the gas in the halo. They also plan to search for other spectral lines, which may help better understand the physical state such as temperature and density of the gas.


News Article | March 27, 2017
Site: www.techtimes.com

NASA has chosen an airborne observatory led by the University of Arizona (UA) over eight other proposed missions vying for NASA's Explorer category. With a target launch date of Dec. 15, 2021, the Galactic/Extragalactic ULDB Spectroscopic Terahertz Observatory (GUSTO) mission with its airborne observatory will fly across Antarctica at an elevation around 110,000 and 120,000 feet, or 17 miles above a typical commercial flight's cruising altitude. Basically, the Ultralong-Duration Balloon (ULDB) has a telescope with carbon, oxygen, and nitrogen emission line detectors mounted to a gondola. With a science payload of almost 2 tons, GUSTO will run on about 1 kilowatt of electrical power produced by solar panels. "NASA has a great history of launching observatories in the Astrophysics Explorers Program with new and unique observational capabilities. GUSTO continues that tradition," Paul Hertz, astrophysics division director in the Science Mission Directorate in Washington, stated. After launching from McMurdo, Antarctica, GUSTO is expected to stay up in the air up 170 days, depending on weather conditions. The total project cost is approximately $40 million dollars, including expenses for the balloon launch, post-launch operations, and data analysis. GUSTO will measure emissions from interstellar mediums, helping scientists get a clearer picture of the life cycle of interstellar gas in the Milky Way galaxy and the birth and death of star-forming clouds. According to experts, the interstellar medium is the material "from which most of the observable universe is made: stars, planets, rocks, oceans, and all living creatures." According to principal investigator Christopher Walker, a professor of astronomy at the UA's Steward Observatory, understanding the interstellar medium is key to understanding where we came from, "because 4.6 billion years ago, we were interstellar medium." Aside from the Milky Way, GUSTO will also map the Large Magellanic Cloud, which according to Walker, is a hallmark of a galaxy more commonly found in the early universe. Walker and his team will use cutting-edge superconducting detectors and other instruments that will enable them to listen in at very high frequencies. Walker said that with the measurements from the GUSTO mission, experts can have enough data to develop a model for earlier galaxies and our home galaxy, the Milky Way, which are the two "bookends" of evolution through cosmic time. As a prelude to the GUSTO mission, Walker's team triumphantly launched a balloon with a smaller telescope — the Stratospheric Terahertz Observatory, or STO — above South Pole back in December 2016. Johns Hopkins University is reportedly in charge for the GUSTO balloon's gondola. Other participating organizations in the GUSTO mission include NASA's Jet Propulsion Laboratory, Massachusetts Institute of Technology, Arizona State University, and the SRON Netherlands Institute for Space Research. © 2017 Tech Times, All rights reserved. Do not reproduce without permission.


But of course, like most NEOs that periodically make a close pass to Earth, 2017 HX4 passed us by at a very safe distance. In fact, the asteroid's closest approach to Earth was estimated to be at a distance of 3.7 Lunar Distances (LD) – i.e. almost four times the distance between the Earth and the Moon. This, and other pertinent information was tweeted in advance by the International Astronomical Union's Minor Planet Center (IAU MPC) on April 29th. This object was first spotted on April 26th, 2017, using the 1.8 meter Panoramic Survey Telescope and Rapid Response System (Pan-STARRS), located at the summit of Haleakala in Hawaii. Since that time, it has been monitored by multiple telescopes around the world, and its tracking data and information about its orbit and other characteristics has been provided by the IAU MPC. With funding provided by NASA's Near-Earth Object Observations program, the IAU MPC maintains a centralized database that is responsible for the identification, designation and orbit computations of all the minor planets, comets and outer satellites of the Solar System. Since it's inception, it has been maintaining information on 16,202 Near-Earth Objects, 729,626 Minor Planets, and 3,976 comets. But it is the NEOs that are of particular interest, since they periodically make close approaches to Earth. In the case of 2017 HX4, the object has been shown to have an orbital period of 2.37 years, following a path that takes it from beyond the orbit of Venus to well beyond the orbit of Mars. In other words, it orbits our sun at an average distance (semi-major axis) of 1.776 AU, ranging from about 0.88 AU at perihelion to 2.669 AU at aphelion. Since it was first spotted, the object has been viewed a total of 41 times between April 26th and May 4th. In addition to the Pan-STARRS-1 survey, observations were also provided by the Cerro Tololo Observatory, the Mauna Kea Observatories, the Steward Observatory and the Kitt Peak-Spacewatch Telescopes, the Astronomical Research Observatory, the Apache Point Observatory, and the Mount John Observatory. From these combined observations, the IAU MPC was able to compile information on the object's orbital period, when it would cross Earth's orbit, and just how close it would come to us in the process. So, as always, there was nothing to worry about here folks. These objects are always spotted before they cross Earth's orbit, and their paths, periods and velocities and are known about in advance. Even so, it's worth noting that an object of this size was nowhere near to be large enough to cause an Extinction Level Event. In fact, the asteroid that struck Earth 65 millions year ago at the end of Cretaceous era – which created the Chicxulub Crater on the Yucatan Peninsula in Mexico and caused the extinction of the dinosaurs – was estimated to measure 10 km across. At 10 to 33 meters (32.8 to 108 feet), this asteroid would certainly have caused considerable damage if it hit us. But the results would not exactly have been cataclysmic. Still, it might not be too soon to consider getting off this ball of rock. You know, before – as Hawking has warned – a single event is able to claim all of humanity in one fell swoop! The MPC is currently tracking the 13 NEOs that were discovered during the month of May alone, and that's just so far. Expect to hear more about rocks that might cross our path in the future. Explore further: Asteroid to fly safely past Earth on April 19

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