Comet Lovejoy Shows Asymmetric Behavior At Perihelion

Indian astronomers have recently conducted spectrographic observations of long-period Comet Lovejoy to study its gas emission. They found that this comet showcases an asymmetric behavior at perihelion and an increase in the activity during the post-perihelion phase. The findings were detailed in a paper published July 22 on the arXiv pre-print server.

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Comet Lovejoy, formally designated C/2014 Q2, is an Oort cloud comet, discovered by Terry Lovejoy in August 2014. Its perihelion was on January 30, 2015 at a heliocentric distance of 1.29 AU, offering astronomers an excellent opportunity to observe its activity—in particular, the emission of numerous organic molecules in gas.

The scientists, led by Kumar Venkataramani of the Physical Research Laboratory in Ahmedabad, India, utilized the LISA spectrograph to obtain spectra of the comet. LISA is a low-resolution, high luminosity spectrograph, designed for the spectroscopic study of faint and extended objects. The instrument is installed on the 0.5 m telescope at the Mount Abu Infra-Red Observatory (MIRO), Mount Abu, India.

The observation campaign lasted from January to May 2015. It covered the period during which the comet’s heliocentric distance varied from 1.29 AU, just prior to perihelion, to around 2.05 AU post perihelion. The spectra obtained by the researchers show strong molecular emission bands of diatomic carbon, tricarbon, cyanide, amidogen, hydridocarbon and neutral oxygen.

“Various molecular emission lines like C2, C3, CN, NH2, CH, O were clearly seen in the comet spectrum throughout this range. The most prominent of them being the C2 molecule, which was quite dominant throughout the time that we have followed the comet. Apart from the C2 emission band, those of CN and C3 were also quite prominent,” the scientist wrote in the paper.

When a cold icy body like the Comet Lovejoy passes by the sun near perihelion, its ices start sublimating, releasing a mixture of gas and dust, which form the coma. Studying these emissions is crucial for scientists as comets could hold the key to our understanding of the solar system’s evolution and the origin of life in the universe. Therefore, the abundance of volatile material in comets is the target of many scientific studies that seek to reveal the secrets of planet formation and demonstrate the conditions that occurred when our solar system was born.

According to the study, the gas production rate increased after perihelion and exhibited a decreasing trend only after February 2015. The researchers also noted a simultaneous increase in gas and dust, indicating an increase in the overall activity of the comet after its perihelion passage.

“This kind of asymmetry has been seen in many comets. (…) Although we do not have data points at exactly the same distance for pre- and post-perihelion passages, we can, perhaps, say that this comet may have a large positive asymmetry,” the paper reads.

The scientists concluded that this asymmetry suggests that there might be volatile material present beneath the surface of the comet. It is also possible that the surface of the comet’s nucleus consists of layers of ice that have different vaporization rates.

However, as the team noted, more exhaustive study is required to confirm their conclusions.

NASA To Map The Surface Of An Asteroid

NASA’s OSIRIS-REx spacecraft will launch September 2016 and travel to a near-Earth asteroid known as Bennu to harvest a sample of surface material and return it to Earth for study. The science team will be looking for something special. Ideally, the sample will come from a region in which the building blocks of life may be found.

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To identify these regions on Bennu, the Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer (OSIRIS-REx) team equipped the spacecraft with an instrument that will measure the spectral signatures of Bennu’s mineralogical and molecular components.

Known as OVIRS (short for the OSIRIS-REx Visible and Infrared Spectrometer), the instrument will measure visible and near-infrared light reflected and emitted from the asteroid and split the light into its component wavelengths, much like a prism that splits sunlight into a rainbow.

“OVIRS is key to our search for organics on Bennu,” said Dante Lauretta, principal investigator for the OSIRIS-REx mission at the University of Arizona in Tucson. “In particular, we will rely on it to find the areas of Bennu rich in organic molecules to identify possible sample sites of high science value, as well as the asteroid’s general composition.”

OVIRS will work in tandem with another OSIRIS-REx instrument—the Thermal Emission Spectrometer, or OTES. While OVIRS maps the asteroid in the visible and near infrared, OTES picks up in the thermal infrared. This allows the science team to map the entire asteroid over a range of wavelengths that are most interesting to scientists searching for organics and water, and help them to select the best site for retrieving a sample.

In the visible and infrared spectrum, minerals and other materials have unique signatures like fingerprints. These fingerprints allow scientists to identify various organic materials, as well as carbonates, silicates and absorbed water, on the surface of the asteroid. The data returned by OVIRS and OTES will actually allow scientists to make a map of the relative abundance of various materials across Bennu’s surface.

“I can’t think of a spectral payload that has been quite this comprehensive before,” said Dennis Reuter, OVIRS instrument scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

OVIRS will be active during key phases throughout the mission. As the OSIRIS-REx spacecraft approaches Bennu, OVIRS will view one entire hemisphere at a time to measure how the spectrum changes as the asteroid rotates, allowing scientists to compare ground-based observations to those from the spacecraft. Once at the asteroid, OVIRS will gather spectral data and create detailed maps of the surface and help in the selection of a sample site.

Using information gathered by OVIRS and OTES from the visible to the thermal infrared, the science team will also study the Yarkovsky Effect, or how Bennu’s orbit is affected by surface heating and cooling throughout its day. The asteroid is warmed by sunlight and re-emits thermal radiation in different directions as it rotates. This asymmetric thermal emission gives Bennu a small but steady push, thus changing its orbit over time. Understanding this effect will help scientists study Bennu’s orbital path, improve our understanding of the Yarkovsky effect, and improve our predictions of its influence on the orbits of other asteroids.

But despite its capabilities to perform complex science, OVIRS is surprisingly inexpensive and compact in its design. The entire spectrometer operates at 10 watts, requiring less power than a standard household light bulb.

“When you put it into that perspective, you can see just how efficient this instrument is, even though it is taking extremely complicated science measurements,” said Amy Simon, deputy instrument scientist for OVIRS at Goddard. “We’ve put a big job in a compact instrument.”
Unlike most spectrometers, OVIRS has no moving parts, reducing the risk of a malfunction.

“We designed OVIRS to be robust and capable of lasting a long time in space,” Reuter said. “Think of how many times you turn on your computer and something doesn’t work right or it just won’t start up. We can’t have that type of thing happen during the mission.”

Drastic temperature changes in space will put the instrument’s robust design to the test. OVIRS is a cryogenic instrument, meaning that it must be at very low temperatures to produce the best data. Generally, it doesn’t take much for something to stay cool in space. That is, until it comes in contact with direct sunlight.
Heat inside OVIRS would increase the amount of thermal radiation and scattered light, interfering with the infrared data. To avoid this risk, the scientists anodized the spectrometer’s interior coating. Anodizing increases a metal’s resistance to corrosion and wear. Anodized coatings can also help reduce scattered light, lowering the risk of compromising OVIRS’ observations.

The team also had to plan for another major threat: water. The scientists will search for traces of water when they scout the surface for a sample site. Because the team will be searching for tiny water levels on Bennu’s surface, any water inside OVIRS would skew the results. And while the scientists don’t have to worry about a torrential downpour in space, the OSIRIS-REx spacecraft may accumulate moisture while resting on its launch pad in Florida’s humid environment.

Immediately after launch, the team will turn on heaters on the instrument to bake off any water. The heat will not be intense enough to cause any damage to OVIRS, and the team will turn the heaters off once all of the water has evaporated.

“There are always challenges that we don’t know about until we get there, but we try to plan for the ones that we know about ahead of time,” said Simon.
OVIRS will be essential for helping the team choose the best sample site. Its data and maps will give the scientists a picture of what is present on Bennu’s surface.

In addition to OVIRS, Goddard will provide overall mission management, systems engineering and safety and mission assurance for OSIRIS-REx. Dante Lauretta is the mission’s principal investigator at the University of Arizona. Lockheed Martin Space Systems in Denver built the spacecraft. OSIRIS-REx is the third mission in NASA’s New Frontiers Program. NASA’s Marshall Space Flight Center in Huntsville, Alabama, manages New Frontiers for the agency’s Science Mission Directorate in Washington.

Digging Deeper Into Mars

Water is the key to life on Earth. Scientists continue to unravel the mystery of life on Mars by investigating evidence of water in the planet’s soil. Previous observations of soil observed along crater slopes on Mars showed a significant amount of perchlorate salts, which tend to be associated with brines with a moderate pH level.

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However, researchers have stepped back to look at the bigger picture through data collected from the 2001: Mars Odyssey, named in reference to the science fiction novel by Arthur C. Clarke, “2001: A Space Odyssey,” and found a different chemical on Mars may be key. The researchers found that the bulk soil on Mars, across regional scales the size of the U.S. or larger, likely contains iron sulfates bearing chemically bound water, which typically result in acidic brines. This new observation suggests that iron sulfates may play a major role in hydrating martian soil.

This finding was made from data collected by the 2001: Mars Odyssey Gamma Ray Spectrometer, or GRS, which is sensitive enough to detect the composition of Mars soil up to one-half meter deep. This is generally deeper than other missions either on the ground or in orbit, and it informs the nature of bulk soil on Mars. This research was published recently in the Journal of Geophysical Research: Planets.

“This is exciting because it’s contributing to the story of water on Mars, which we’ve used as a path for our search for life on Mars,” said Nicole Button, LSU Department of Geology and Geophysics doctoral candidate and co-author in this study.

The authors expanded on previous work, which explored the chemical association of water with sulfur on Mars globally. They also characterized how, based on the association between hydrogen and sulfur, the soil hydration changes at finer regional scales. The study revealed that the older ancient southern hemisphere is more likely to contain chemically bound water while the sulfates and any chemically bound water are unlikely to be associated in the northerly regions of Mars.

The signature of strong association is strengthened in the southern hemisphere relative to previous work, even though sulfates become less hydrated heading southwards. In addition, the water concentration may affect the degree of sulfate hydration more than the sulfur concentration. Limited water availability in soil-atmosphere exchange and in any fluid movement from deeper soil layers could explain how salt hydration is water-limited on Mars. Differences in soil thickness, depth to any ground ice table, atmospheric circulation and sunshine may contribute to hemispheric differences in the progression of hydration along latitudes.

The researchers considered several existing hypotheses in the context of their overall observations, which suggest a meaningful presence of iron-sulfate rich soils, which are wet compared to Mars’ typically desiccated soil. This type of wet soil was uncovered serendipitously by the Spirit Rover while dragging a broken wheel across the soil in the Paso Robles area of Columbia Hills at Gusev Crater. Key hypotheses of the origin of this soil include hydrothermal activity generating sulfate-rich, hydrated deposits on early Mars similar to what is found along the flanks of active Hawaiian volcanoes on Earth.
Alternatively, efflorescence, which creates the odd salt deposits on basement walls on Earth, may have contributed trace amounts of iron-sulfates over geologic time. A third key hypothesis involves acidic aerosols released at volcanic sites, such as acid fog, dispersed throughout the atmosphere, and interacting subsequently with the finer components of soil as a source of widespread hydrated iron-sulfate salts.

Among these hypotheses, the researchers identify acid fog and hydrothermal processes as more consistent with their observations than efflorescence, even though the sensitivity of GRS to elements, but not minerals, prevents a decisive inference. Hydrothermal sites, in particular, are increasingly recognized as important places where the exchange between the surface and deep parts of Earth’s biosphere are possible. This hypothesis is significant to the question of martian habitability.

“Our story narrows it to two hypotheses, but emphasizes the significance of all of them,” said LSU Department of Geology and Geophysics Assistant Professor Suniti Karunatillake, who is a fellow lead author. “The depth and breadth of these observation methods tell us about global significance, which can inform the big question of what happened to the hydrologic cycle on Mars.”

Astronomers Discover Dizzying Spin Of The Milky Way Galaxy’s ‘Halo’

Astronomers at the University of Michigan’s College of Literature, Science, and the Arts (LSA) discovered for the first time that the hot gas in the halo of the Milky Way galaxy is spinning in the same direction and at comparable speed as the galaxy’s disk, which contains our stars, planets, gas, and dust.

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This new knowledge sheds light on how individual atoms have assembled into stars, planets, and galaxies like our own, and what the future holds for these galaxies.

“This flies in the face of expectations,” says Edmund Hodges-Kluck, assistant research scientist. “People just assumed that the disk of the Milky Way spins while this enormous reservoir of hot gas is stationary – but that is wrong. This hot gas reservoir is rotating as well, just not quite as fast as the disk.”

The new NASA-funded research using the archival data obtained by XMM-Newton, a European Space Agency telescope, was recently published in the Astrophysical Journal. The study focuses on our galaxy’s hot gaseous halo, which is several times larger than the Milky Way disk and composed of ionized plasma.

Because motion produces a shift in the wavelength of light, the U-M researchers measured such shifts around the sky using lines of very hot oxygen. What they found was groundbreaking: The line shifts measured by the researchers show that the galaxy’s halo spins in the same direction as the disk of the Milky Way and at a similar speed—about 400,000 mph for the halo versus 540,000 mph for the disk.

“The rotation of the hot halo is an incredible clue to how the Milky Way formed,” said Hodges Kluck. “It tells us that this hot atmosphere is the original source of a lot of the matter in the disk.”

Scientists have long puzzled over why almost all galaxies, including the Milky Way, seem to lack most of the matter that they otherwise would expect to find. Astronomers believe that about 80% of the matter in the universe is the mysterious “dark matter” that, so far, can only be detected by its gravitational pull. But even most of the remaining 20% of “normal” matter is missing from galaxy disks. More recently, some of the “missing” matter has been discovered in the halo. The U-M researchers say that learning about the direction and speed of the spinning halo can help us learn both how the material got there in the first place, and the rate at which we expect the matter to settle into the galaxy.

“Now that we know about the rotation, theorists will begin to use this to learn how our Milky Way galaxy formed – and its eventual destiny,” says Joel Bregman, a U-M LSA professor of astronomy.

“We can use this discovery to learn so much more – the rotation of this hot halo will be a big topic of future X-ray spectrographs,” Bregman says.

Magma Build-Up May Put Salvadoran Capital At Risk

The build-up of magma six kilometres below El Salvador’s Ilopango caldera means the capital city of San Salvador may be at risk from future eruptions, University of Bristol researchers have found.

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A caldera is a large cauldron-like volcanic depression or crater, formed by the collapse of an emptied magma chamber. The depression often originates from very big explosive eruptions. In Guatemala and El Salvador, caldera volcanoes straddle tectonic fault zones along the Central American Volcanic Arc (CAVA). The CAVA is 1,500 kilometres long, stretching from Guatemala to Panama.

The team, from the Volcanology research group at Bristol’s School of Earth Sciences and the Ministry of the Environment and Natural Resources in El Salvador, studied the density distribution beneath the Ilopango caldera and the role tectonic stresses – caused by the movement of tectonic plates along fault lines – have on the build-up of magma at depth. Their study is published today in the journal Nature Communications.

The Ilopango caldera is an eight km by 11 kilometre volcanic collapse structure of the El Salvador Fault Zone. The collapsed caldera was the result of at least five large eruptions over the past 80,000 years.

The last of these occurred about 1,500 years ago and produced enough volcanic ash to form a 15 centimetre thick layer across the entire UK. This catastrophic eruption destroyed practically everything within a 100 kilometre radius, including a well-developed native Mayan population, and significantly disturbed the Mayan populations as far as 200 kilometres away.

The most recent eruptions occurred in 1879–1880 and were on a much smaller scale than the previous one.

Project leader and co-author Dr Joachim Gottsmann said: “Most earthquakes take place along the edges of tectonic plates, where many volcanoes are also located. There is therefore a link between the breaking of rocks, which causes faults and earthquakes and the movement of magma from depth to the surface, to feed a volcanic eruption. The link between large tectonic fault zones and volcanism is, however, not very well understood.”

Existing studies show that magma accumulation before a large caldera-forming eruption, as well as the caldera collapse itself, may be controlled by fault structures.

“However, it is unclear to what extent regional tectonic stresses influence magma accumulation between large caldera-forming eruptions.”, co-author Professor Katharine Cashman said.

Lead author Jennifer Saxby, whose research towards a MSc in Volcanology contributed to the study, said: “Addressing this question is important not only for understanding controls on the development of magmatic systems, but also for forecasting probable locations of future eruptive activity from caldera-forming volcanoes.”

The team discovered that the current tectonic stress field promotes the accumulation of magma and hydrothermal fluids at shallow (< 6km) depth beneath Ilopango. The magma contains a considerable amount of gas, which indicates the system is charged to possibly feed the next eruption.

Dr Gottsmann said: “Our results indicate that localised extension along the fault zone controls the accumulation, ascent and eruption of magma at Ilopango. This fault-controlled magma accumulation and movement limits potential vent locations for future eruptions at the caldera in its central, western and northern part – an area that now forms part of the metropolitan area of San Salvador, which is home to 2 million people. As a consequence, there is a significant level of risk to San Salvador from future eruptions of Ilopango.”

Seven New Embedded Clusters Detected In The Galactic Halo

A team of Brazilian astronomers, led by Denilso Camargo of the Federal University of Rio Grande do Sul in Porto Alegre, has discovered seven new embedded clusters located unusually far away from the Milky Way’s disc. The findings, presented in a paper published July 3 on arXiv.org, could provide new insights on star cluster formation.

Embedded clusters are stellar clusters encased in an interstellar dust or gas, consisting of extremely young stars. They are crucial for astronomers to better understand star formation and early stellar evolution. Studying these clusters could reveal the origin of stellar masses as well as the origin and evolution of protoplanetary disks, where planet formation processes take place.

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In the Milky Way galaxy, most of embedded clusters lie within the thin disc less than 1,000 light years from the galactic midplane, especially in the spiral arms. However, Camargo and his team detected two young stellar clusters earlier this year, and now, after spotting seven more, suggest that they could be more common on the outskirts of the galaxy than previously thought.

“Now, we discovered seven star clusters far away from the Milky Way disc. Thus, this work points to a new paradigm in the star and star cluster formation, in the sense that the formation of such objects occurs in the halo and it seems to be frequent,” Camargo told Phys.org.

The scientists found the new clusters by analyzing the data provided by NASA’s Wide-field Infrared Survey Explorer (WISE). This space telescope is monitoring the entire galaxy in infrared light, snapping pictures of mainly remote galaxies, stars and asteroids. WISE was chosen for this job as it captures embedded clusters that are invisible at optical wavelengths, due to the fact that they are engulfed in significant amounts of interstellar dust.

“WISE provided infrared images of the entire sky, allowing us to penetrate the gas and dust within giant molecular clouds, in which the star formation can take place. Recently, we discovered more than 1,000 embedded clusters using WISE,” Camargo said.

According to the research paper, three newly found objects, designated C 932, C 934, and C 939, are high-latitude embedded clusters, projected within the newly identified cloud complex. These clusters are located at a vertical distance of about 16,300 light years below the galactic disc. Other new clusters, named C 1074, C 1099, C 1100, and C 1101, are in the range from 5,500 to 10,400 light years above the disc. All these clusters are younger than five million years.

The team noted that the new findings indicate that a sterile galactic halo could host ongoing star formation. The newly detected embedded clusters provide evidence of widespread star cluster forming processes far away from the Milky Way’s disc.

“The discovery of stellar clusters far away from the disc suggests that the Galactic halo is more actively forming stars than previously thought. Moreover, since most young clusters do not survive for more than five million years, the halo may be raining stars into the disc. The halo harbors generations of stars formed in clusters like those hereby detected,” Camargo said.

Before the team’s paper was published, it was thought that star formation processes in the Milky Way occur in the disk, but not in the halo. Thus, as Camargo concluded, this new study represents a paradigm shift, in the sense that a sterile halo becomes now a host of ongoing star formation.

A Star’s Birth Holds Early Clues To Life Potential

Our solar system began as a cloud of gas and dust. Over time, gravity slowly pulled these bits together into the Sun and planets we recognize today. While not every system is friendly to life, astronomers want to piece together how these systems are formed.

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A challenge to this research is the opacity of dust clouds to optical wavelengths (the ones that humans can see). So, astronomers are experimenting with different wavelengths, such as infrared light, to better see the center of dense dust clouds, where young stars typically form.

Recently, astronomers used data from NASA’s Spitzer Space Telescope—a powerful space observatory launched in 2003 that observes the Universe in infrared light—to look at a molecular cloud called L183, which is about 360 light-years away in the constellation Serpens Cauda (the serpent). Their goal was to see how light scattering affects the view of the cloud at the mid-infrared wavelength of 8 microns (μm). Ultimately, the astronomers hope to use this data to get a better look inside the clouds.

“One thing we have to do is evaluate the mass that is sitting in the center of the cloud, which is ready to collapse to make a star,” said co-author Laurent Pagani, a researcher at the National Center for Scientific Research (CNRS) in Paris, France.

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His former doctoral student, Charlène Lefèvre, led the research. Their work was recently published in the journal Astronomy and Astrophysics under the title, “On the importance of scattering at 8 μm: Brighter than you think.” Funding for the research came from CNRS and the French government.

Penetrating the dust

Dust clouds are tough to see through not only because of the dust itself, but also because the gases present are not very visible in telescopes observing in the infrared. Clouds are mainly made up of hydrogen and helium, which emit no radiation in the infrared or millimeter wavelengths. These two elements make up 98 percent of the mass of the cloud, meaning most of it is escaping any kind of measurement.

To get around this measurement problem, astronomers use proxies such as dust. Dust is roughly 1 percent of the cloud’s mass, but it is best measured at the edges of the cloud. Dust abundance can be inferred through the extinction of starlight. Since we can also measure the quantity of molecular hydrogen via ultraviolet absorption at the edge of the clouds, the dust abundance is derived with respect to molecular hydrogen. Once “calibrated,” the dust mass is measured throughout the cloud, providing the molecular hydrogen gas and the cloud mass.

For this project, Pagani and his team attempted to measure the amount of dust absorption at 8 microns for the cloud L183. It’s common to find light at this wavelength throughout the galaxy, making it a potential measuring tool for different clouds. By measuring the absorption, scientists can estimate how much light is coming from the front of the cloud to the back of the cloud; in other words, by how much the light from the background is diminished.

 

In so doing, astronomers hope to gain a better understanding about how young stars form. Other, unrelated studies of dust clouds are also looking at where elements—including those grouped in molecules associated with life, such as water—are situated in young solar systems.

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The method appears to work, but there are limitations, the researchers concluded. Different types of dust clouds appear to be more or less sensitive to different wavelengths of light, making it difficult to see what is inside this region.

“There is not only absorption, but also scattering [in L183], and this scattering diminishes the contrast,” Pagani said. “You have the light that is absorbed by the dust, but the dust is also emitting or scattering light towards the observer. It looks less deep than it actually is, if you don’t take into account the scattering.”
Lefèvre was able to use the 8-micron scattering model correctly to fit other observations of the cloud. However, if she tried to observe using other wavelengths—such as 100 microns or 200 microns—she saw a very different picture concerning dust absorption. It’s possible that some of the measurements were affected by ice on the dust, which was not accounted for by her radiative transfer model, Pagani said.

More work will be required. The two researchers (Lefèvre is now a post-doctoral researcher at IRAM, the international Institute for Millimeter Radio-Astronomy but still working with Pagani) are using more grain types to try different methods to measure clouds at various wavelengths. “If this works, we know what kind of grains work in the clouds,” Pagani said. “If it doesn’t work, we have to talk to the theoreticians to modify [the models] to fit the observations.”