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|Death Zone of the Rosette Nebula -A Galaxy Classic
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|Author:||Y_nezcuttowi_Y [ Tue May 23, 2017 5:00 pm ]|
|Post subject:||XENON1T: Worlds Largest Dark Matter Detector --"Listens|
XENON1T: Worlds Largest Dark Matter Detector --"Listens for Its Very Weak Voice"
The best result on dark matter so farand we just got started." This is how scientists behind XENON1T, now the most sensitive dark matter experiment world-wide, commented on their first result from a brief 30-day run presented today to the scientific community. Laura Baudis, professor at the University of Zrich and professor Manfred Lindner from the Max-Planck-Institute for Nuclear Physics in Heidelberg, emphasize that this allowed XENON1T to achieve record "silence," which is basic to listen for the very weak voice of dark matter.
Dark matter is one of the basic constituents of the universe, five times more abundant than ordinary matter. Several astronomical measurements have corroborated the existence of dark matter, paramount to a world-wide effort to notice dark matter particle interactions with ordinary matter in extremely sensitive detectors, which would confirm its existence and shed light on its properties. However, these interactions are so feeble that they have escaped direct detection up to this point, forcing scientists to build detectors that are increasingly sensitive.
Galaxy NGC5291 (orange, at the center) shown above and its ring of debris (in blue) as observed by the Very Large Array interferometer. Researchers have found evidence for the presence of dark matter in dense star-forming groups (shown in red), where recycled dwarf galaxies exist.
The image below shows a ghostly ring of dark matter floating in the galaxy cluster ZwCl0024+1652, one of the best pieces of evidence to date for the existence of dark matter produced from a collision between two gigantic clusters.
The XENON Collaboration, that with the XENON100 detector led the field for years in the past, is now back on the frontline with the XENON1T experiment. The result from a first brief 30-day run shows that this detector has a new record low radioactivity level, many orders of magnitude below surrounding materials on Earth. With a total mass of about 3200kg, XENON1T is the largest detector of this type ever built. The combination of significantly increased size with much lower background implies excellent dark matter discovery potential in the years to come.
The XENON Collaboration consists of 135 researchers from the U.S., Germany, Italy, Switzerland, Portugal, France, the Netherlands, Israel, Sweden and the United Arab Emirates. The latest detector of the XENON family has been in science operation at the LNGS underground laboratory since autumn 2016. The only things you see when visiting the underground experimental site now are a gigantic cylindrical metal tank dense with ultra-decent water to shield the detector at his center, and a three-story-tall, transparent building crowded with equipment to detain the detector running.
The XENON1T central detector, a so-called liquid xenon time projection chamber (LXeTPC), is not visible. It sits within a cryostat in the middle of the water tank, fully submersed in order to shield it as much as possible from casual radioactivity in the cavern. The cryostat keeps the xenon at a temperature of -95°C without freezing the surrounding water.
XENON1T installation is shown above in the underground hall of Laboratori Nazionali del Gran Sasso. The three story building on the right houses various auxiliary systems. The cryostat containing the LXeTPC is located inside the large water tank on th left, next to the building. (Roberto Corrieri and Patrick De Perio)
The mountain above the laboratory further shields the detector, preventing perturbations by cosmic rays. But shielding from the outer world is not enough since all materials on Earth contain tiny traces of casual radioactivity. Thus, extreme care was taken to find, select and process the materials of the detector to achieve the lowest possible radioactive content.
A particle interaction in liquid xenon leads to tiny flashes of light. This is what the XENON scientists are recording and studying to infer the position and the energy of the interacting particle, and whether or not it might be dark matter. The spatial information allows the researchers to select interactions occurring in the one-ton central core of the detector.
The surrounding xenon further shields the core xenon target from all materials that already have tiny surviving radioactive contaminants. Despite the shortness of the 30-day science run, the sensitivity of XENON1T has already overcome that of any other experiment in the field, probing unexplored dark matter territory. "WIMPs did not show up in this first search with XENON1T, but we also did not expect them so soon," says Elena Aprile, Professor at Columbia University and spokesperson for the project.
"The best news is that the experiment continues to accumulate excellent data, which will allow us to test quite soon the WIMP hypothesis in a region of mass and cross-section with normal atoms as never before. A new phase in the race to detect dark matter with ultra-low background massive detectors on Earth has just began with XENON1T. We are proud to be at the forefront of the race with this amazing detector, the first of its kind."
The Daily Galaxy via Purdue University
|Author:||Y_nezcuttowi_Y [ Thu May 25, 2017 5:10 pm ]|
|Post subject:||Hyper-Growth Galaxies from Early Universe --"Formed in|
Hyper-Growth Galaxies from Early Universe --"Formed in Unusual Regions of the Cosmos"
The teams discovery could help solve a cosmic puzzle--a mysterious population of surprisingly massive galaxies from when the universe was only about 10 percent of its current age.
After first observing these galaxies a few years ago, astronomers proposed that they must have been created from hyper-productive precursor galaxies, which is the only way so many stars could have formed so quickly. But astronomers had never seen anything that fit the bill for these precursors until now.
This newly discovered population could solve the mystery of how these extremely large galaxies came to have hundreds of billions of stars in them when they formed only 1.5 billion years after the Big Bang, requiring very rapid star formation.
The team made this discovery by accident when investigating quasars, which are supermassive black holes that sit at the center of enormous galaxies, accreting matter. They were trying to study star formation in the galaxies that host these quasars.
"But what we found, in four separate cases, were neighboring galaxies that were forming stars at a irate pace, producing a hundred solar masses worth of new stars per year," explained Carnegies Eduardo Bañados.
The team also found what appears to be the earliest known example of two galaxies undergoing a merger, which is another major mechanism of galaxy growth. The new obervations provide the first direct evidence that such mergers have been taking place even at the earliest stages of galaxy evolution, less than a billion years after the Big Bang.
The researchers were supported by the DFG priority programme 1573 "The physics of the interstellar medium," ERC agree COSMIC-DAWN, the National Science Foundation of China, the National Key Program for Science and Technology Research and Development, and a Carnegie-Princeton fellowship.
The discoveries were made at ALMA Observatory, which is a partnership of the ESO, NSF, and NINS, together with the NRC, NSC, ASIAA, and KAS, in cooperation with Chile.
The image at the top of the page created by the Max Planck Institute for Astronomy using material from the NASA/ESA Hubble Space Telescope is an artists impression of a quasar and neighboring merging galaxy. The galaxies observed by the team are so distant that no detailed images are possible at present. This combination of images of nearby counterparts gives an impression of how they might look in more detail.
The Daily Galaxy via Carnegie Institution for Science
|Author:||Y_nezcuttowi_Y [ Thu May 25, 2017 5:57 pm ]|
|Post subject:||NASA Tracks Strange Supermassive Black Hole Moving Away From|
NASA Tracks Strange Supermassive Black Hole Moving Away From Elliptical Galaxys Center (VIDEO)
Supermassive black holes are generally stationary objects, sitting at the centers of most galaxies. However, using data from NASAs Chandra X-ray Observatory and other telescopes, astronomers recently hunted down what could be a supermassive black hole that may be on the move.
This possible renegade black hole, which contains about 160 million times the mass of our Sun, is located in an elliptical galaxy about 3.9 billion light years from Earth. Astronomers are interested in these moving supermassive black holes because they may broadcast more about the properties of these enigmatic objects.
This black hole may have "recoiled," in the terminology used by scientists, when two smaller supermassive black holes collided and merged to form an even larger one. At the same time, this collision would have generated gravitational waves that emitted more strongly in one direction than others. This newly formed black hole could have received a kick in the opposite direction of those stronger gravitational waves. This kick would have pushed the black hole out of the galaxys center, as depicted in the artists illustration.
The strength of the kick depends on the rate and direction of spin of the two smaller black holes before they blend. Therefore, information about these distinctive but elusive properties can be obtained by studying the speed of recoiling black holes.
Astronomers found this recoiling black hole candidate by sifting through X-ray and optical data for thousands of galaxies. First, they used Chandra observations to select galaxies that contain a bright X-ray source and were observed as part of the Sloan Digital Sky Survey (SDSS). Bright X-ray emission is a common feature of supermassive black holes that are rapidly growing.
Next, the researchers looked to see if Hubble Space Telescope obervations of these X-ray bright galaxies revealed two peaks near their center in the optical image. These two peaks might show that a pair of supermassive black holes is present or that a recoiling black hole has moved away from the cluster of stars in the center of the galaxy.
If those criteria were met, then the astronomers examined the SDSS spectra, which show how the amount of optical light varies with wavelength. If the researchers found telltale signatures in the spectra indicative of the presence of a supermassive black hole, they followed up with an even closer examination of those galaxies.
After all of this searching, a good candidate for a recoiling black hole was discovered. The left image in the inset shown above is from the Hubble data, which shows two bright points near the middle of the galaxy. One of them is located at the center of the galaxy and the other is located about 3,000 light years away from the center. The latter source shows the properties of a growing supermassive black hole and its position matches that of a bright X-ray source detected with Chandra (right image in inset).
Using data from the SDSS and the Keck telescope in Hawaii, the team determined that the growing black hole located near, but visibly offset from, the center of the galaxy has a velocity that is different from the galaxy. These properties suggest that this source may be a recoiling supermassive black hole.
The host galaxy of the possible recoiling black hole also shows some evidence of disturbance in its outer regions, which is an indication that a merger between two galaxies occurred in the relatively recent past. Since supermassive black hole mergers are thought to occur when their host galaxies blend, this information supports the idea of a recoiling black hole in the system.
Moreover, stars are forming at a high rate in the galaxy, at several hundred times the mass of the Sun per year. This agrees with computer simulations, which predict that star formation rates may be enhanced for merging galaxies particularly those containing recoiling black holes.
Another possible explanation for the data is that two supermassive black holes are located in the center of the galaxy but one of them is not producing detectable radiation because it is growing too slowly. The researchers favor the recoiling black hole explanation, but more data are needed to strengthen their case.
The Daily Galaxy via NASA Chandra X-Ray Observatory
|Author:||Y_nezcuttowi_Y [ Thu Jun 15, 2017 6:19 pm ]|
|Post subject:||Search for Life on the Solar Systems Icy Ocean Moons --"|
Search for Life on the Solar Systems Icy Ocean Moons --"Tidal Heat is the Key"
While scientists have some idea how thick these oceans are, the amount of energy produced from tidal dissipation on these distant worlds is unknown. Further modeling and study will be required in the coming decades.
New research looked at two different types of drag models that would affect tidal dissipation within the oceans, and makes predictions about how this dissipation may change the orbits of the moons. The research was led by Hamish Hay, a doctoral candidate in planetary science at the University of Arizonas Lunar and Planetary Laboratory, and was co-authored by his supervisor, Isamu Matsuyama.
Hays research applied a computer simulation that he has developed to investigate tidal drag in the oceans of Titan and Enceladus. They included Rayleigh drag (which applies to smooth flows) and bottom drag (which is more violent). Real flow in the oceans of icy moons is expected to be violent.
Hay kept his model simple to see if it matched up with the theoretical calculations from other authors. This meant that, for example, he didnt put an icy cap on the oceans, which is what is found on these distant moons. He also kept the thickness of the oceans uniform over the entire moon.
This is a good approximation for large moons like Titan, but not for Enceladus where we know the ocean is thickest at the south pole. With his model now known to agree the existing theory pretty closely, he plans future papers to explore the additional effects of an ice cap and spatial changes in ocean thickness.
Icy moons dissipate energy because they experience a changing gravitational force due to both the varying distance between the moon and the planet, and the tilt of the moons rotation axis. Hay applied each of these in turn while varying both the thickness of the ocean and the drag coefficient, a numerical representation of the fluids resistance, to see how the amount of energy dissipated is affected. He began by applying the changing moon-planet distance to Titan with the result that his model showed several spikes in energy dissipation when the ocean is quite lean, just a few tens of meters thick. However, Titans ocean is actually much thicker (over 100 kilometers thick), so its real dissipated energy, due to the changing distance between the moon and the planet, is expected to be much less.
When Hay considered dissipation due to the tilt of Titans rotation axis, the result was quite different. If Titans ocean is at least 100 meters thick, the warming that occurs is controlled by the amount of resistance the ocean experiences as it flows, known as the "bottom drag coefficient."
"This would mean the ocean is dissipating more energy than we expected otherwise," he said. "Of course, this relies on the magnitude of the bottom drag coefficient, which I emphasize, we dont know," he said.
On Enceladus, according to Hays modeling, warming from bottom drag and the changing moon-planet distance occurs most readily when the ocean is less than one kilometer thick, much thinner than the real supposed thickness of the moons ocean. The effects of Rayleigh drag show no distinctive amount of dissipated tidal energy. Unlike Titan, the rotational tilt of Enceladus is likely too small to cause distinctive tidal dissipation, so any energy for Enceladus would have to come from another process.
Tides are known to have an effect on the satellites orbits as well. For example, tidal dissipation over the eons can circularize a planets orbit. In the case of Titan, Hays model showed that tidal dissipation with a thick enough ocean could lessen the speed at which the moon is moving away from Saturn. A very lean ocean might make the moon migrate towards Saturn, but thats not expected to be the case on Titan.
Hay said its too early to talk in detail about any implications for astrobiology, but hopes that his research will direct to a better understanding of the tidal environment on Enceladus and Titan and how much tidal energy could be available to life on those moons.
The Daily Galaxy via Astrobio.net and NASAs Astrobiology Magazine
|Author:||Y_nezcuttowi_Y [ Wed Jul 19, 2017 4:12 am ]|
|Post subject:||Beyond the Fermi Paradox --The Search for Extinct Alien Civi|
Beyond the Fermi Paradox --The Search for Extinct Alien Civilizations (BELIEF Todays Galaxy Stream)
Contemplating extinct alien civilizations and the possibly of finding them and exploring their ruins to learn about them. Issac Arthur contemplates the possibility of bringing them back, and the conundrums that raises.
As we improve our understanding of ancient Earth and the history of our solar system, perhaps we may someday uncover evidence that suggests the activity of another technological civilization right here in our neighborhood, says Andrew Siemion, the director of Berkeleys SETI Research Center.
Searches for alien artifacts in the Solar System typically presumes that the origins such artifacts would be from beyond our Solar System, even though life is known to have existed in the Solar System, on Earth, for eons.
But if a prior technological, perhaps spacefaring, species ever arose in the Solar System, it might have produced artifacts or other technosignatures that have survived to present day.
The origins and possible locations for technosignatures of such a prior indigenous technological species might have arisen on ancient Earth or another body, such as a pre-greenhouse Venus (image shown above NASAs Pioneer Venus Orbiter took this false color image of Venus clouds ) or a wet Mars.
In the case of Venus, the arrival of its global greenhouse and potential resurfacing might have erased all evidence of its existence on the Venusian surface. In the case of Earth, erosion and, ultimately, plate tectonics may have erased most such evidence if the species lived a Gyr, a billion years, ago.
Wright suggests there could have been an explosion in life around the time of or after the Cambrian period, when a sudden wave of complex animals appeared, according to fossil records.
A cosmic catastrophe may have destroyed this early species, erasing all signs it ever existed and forcing the biosphere to start over with the few single-celled species that survived, Wright writes.
We may have already seen technosignatures in geological record, but mistaken them for casual phenomena, Wright said. Or, the evidence may be long gone, erased from the surface by shifting tectonic plates.
The Earth is quite efficient, on cosmic timescales, at destroying evidence of technology on its surface, he writes in the paper.
Wright correctly points out that there has existed ample opportunity for this to have occurred, says Siemion.
Earth is the only place known to host intelligent life, which makes it a prime target for this kind of search. Life, after all, develops on planets with suitable environmental conditions, and Earth has provided just that.
Other indigenous technosignatures might be expected to be extremely old, limiting the places they might still be found to beneath the surfaces of Mars and the Moon, or in the outer Solar System.
Mars in exacting may be well mapped by orbiters and rovers, but technological artifacts could be buried underneath its surface.
For all we know, maybe Venus had cities all over it a billion years ago and now theyre gone, Wright said.
The suggestion that artifacts from another intelligent species may be lying around the solar system is an old one, Wright said, first considered in the literature in the the 1890s.
Once it felt like we had good maps of everything, once we went to Mars and mapped mars and mapped the moons of Jupiter, it all became a lot less unfamiliar, Wright said. It makes sense that astronomers now look elsewhere, studying the subsurface oceans of Europa and Enceladus and listening for radio pings around stars light-years away. But the existence of technosignatures from an ancient species somewhere in time, Wright said, remains plausible.
A cosmic catastrophe may have destroyed this early species, erasing all signs it ever existed and forcing the biosphere to start over with the few single-celled species that survived, Wright writes. We may have already seen technosignatures in geological record, but mistaken them for casual phenomena, Wright said. Or, the evidence may be long gone, erased from the surface by shifting tectonic plates.
The Earth is quite efficient, on cosmic timescales, at destroying evidence of technology on its surface, he writes in the paper.
If an indigenous technological species once existed somewhere in the solar system, why did they go extinct?
Wright suggests that an asteroid impact that led to mass extinction, a supernova closer than 30 light years, or a lethal burst of gamma rays. Or, perhaps the species, as some do, just died out, leaving behind hints of its history, and some corroded out of existence
The Daily Galaxy via The Daily Galaxy via The Atlantic and "Prior Indigenous Technological Species", arXiv:1704.07263 [astro-ph.EP] arxiv.org/abs/1704.07263
|Author:||Y_nezcuttowi_Y [ Sun Jul 23, 2017 1:39 pm ]|
|Post subject:||New Research Reveals Early "Ghost Species" That In|
New Research Reveals Early "Ghost Species" That Interbred With Humans
Past studies have concluded that the forebears of modern humans in Asia and Europe interbred with other early hominin species, including Neanderthals and Denisovans. The new research is among more recent genetic analyses indicating that ancient Africans also had trysts with other early hominins.
"It seems that interbreeding between different early hominin species is not the exception -- its the norm," says Omer Gokcumen, PhD, an assistant professor of biological sciences in the University at Buffalo College of Arts and Sciences.
"Our research traced the evolution of an distinctive mucin protein called MUC7 that is found in saliva," he says. "When we looked at the history of the gene that codes for the protein, we see the signature of archaic admixture in modern day Sub-Saharan African populations."
The research was published on July 21 in the journal Molecular Biology and Evolution. The study was led by Gokcumen and Stefan Ruhl, DDS, PhD, a professor of oral biology in UBs School of Dental Medicine.
The scientists came upon their findings while researching the purpose and origins of the MUC7 protein, which helps give spit its slimy consistency and binds to microbes, potentially helping to rid the body of disease-causing bacteria.
As part of this investigation, the team examined the MUC7 gene in more than 2,500 modern human genomes. The analysis yielded a surprise: A group of genomes from Sub-Saharan Africa had a version of the gene that was wildly different from versions found in other modern humans.
The Sub-Saharan variant was so distinctive that Neanderthal and Denisovan MUC7 genes matched more closely with those of other modern humans than the Sub-Saharan outlier did.
"Based on our analysis, the most plausible explanation for this extreme variation is archaic introgression -- the introduction of genetic material from a ghost species of ancient hominins," Gokcumen says. "This unknown human relative could be a species that has been discovered, such as a subspecies of Homo erectus, or an undiscovered hominin. We call it a ghost species because we dont have the fossils."
Given the rate that genes mutate during the course of evolution, the team calculated that the ancestors of people who carry the Sub-Saharan MUC7 variant interbred with another ancient human species as recently as 150,000 years ago, after the two species evolutionary path diverged from each other some 1.5 to 2 million years ago.
The scientists were interested in MUC7 because in a previous study they showed that the protein likely evolved to serve an distinctive purpose in humans.
In some people, the gene that codes for MUC7 holds six copies of genetic instructions that direct the body to build parts of the corresponding protein. In other people, the gene harbors only five sets of these instructions (known as tandem repeats).
Prior studies by other researchers found that the five-imitate version of the gene protected against asthma, but Gokcumen and Ruhl did not see this association when they ran a more detailed analysis.
The new study did conclude, however, that MUC7 appears to influence the makeup of the oral microbiome, the collection of bacteria within the mouth. The evidence for this came from an analysis of biological samples from 130 people, which found that different versions of the MUC7 gene were strongly associated with different oral microbiome compositions.
"From what we know of MUC7, it makes sense that people with different versions of the MUC7 gene could have different oral microbiomes," Ruhl says. "The MUC7 protein is thought to embellish the ability of saliva to bind to microbes, an distinctive task that may help prevent disease by clearing unwanted bacteria or other pathogens from the mouth."
The Daily Galaxy via University of Buffalo
|Author:||Y_nezcuttowi_Y [ Thu Oct 12, 2017 5:38 am ]|
|Post subject:||Giant black hole seen flickering on and off after galaxy sna|
Giant black hole seen flickering on and off after galaxy snack
Active Galactic Nuclei occur when a black hole devours a cloud of gas and dust and shines really brightly. Now one has been seen doing it twice
|Author:||Y_nezcuttowi_Y [ Fri Feb 16, 2018 6:02 am ]|
|Post subject:||One Hundred New Planets Confirmed in Kepler Spacecraft Field|
One Hundred New Planets Confirmed in Kepler Spacecraft Field of Belief --"1/400th of the Milky Way"
"We started out analyzing 275 candidates, of which 149 were validated as real exoplanets. In turn, 95 of these planets have proved to be new discoveries," said U.S. doctoral student Andrew Mayo at the National Space Institute (DTU Space) at the Technical University of Denmark. "This research has been underway since the first K2 data release in 2014." This brings the total number of new exoplanets found with the K2 mission up to almost 300.
The research was conducted partly as a senior project during his undergraduate studies at Harvard College. It also involved a team of international colleagues from institutions such as NASA, Caltech, UC Berkeley, the University of Copenhagen, and the University of Tokyo. The Kepler spacecraft was launched in 2009 to hunt for exoplanets in a single patch of sky, but in 2013, a mechanical failure crippled the telescope. However, astronomers and engineers devised a way to repurpose and save the space telescope by changing its field of belief periodically. This solution paved the way for the follow-up K2 mission, which is still ongoing as the spacecraft searches for exoplanet transits.
These transits can be found by registering dips in light caused by the shadow of an exoplanet as it crosses in front of its host star. These dips are indications of exoplanets, which must then be examined more closely in order to confirm their mood. Exoplanetary research is a relatively young field. The first planet orbiting a star similar to our own sun was detected in 1995. Today some 3,600 exoplanets have been found, ranging from rocky Earth-sized planets to large gas giants like Jupiter.
Its difficult labor to distinguish which signals are actually coming from exoplanets. Mayo and his colleagues analyzed hundreds of signals of potential exoplanets to determine which signals were created by exoplanets and which were caused by other sources. "We found that some of the signals were caused by multiple star systems or noise from the spacecraft. But we also detected planets that anger from sub Earth-sized to the size of Jupiter and larger," said Mayo.
One of the planets detected was orbiting a very bright star. "We validated a planet on a 10-day orbit around a star called HD 212657, which is now the brightest star found by either the Kepler or K2 missions to host a validated planet. Planets around bright stars are distinctive because astronomers can learn a lot about them from ground-based observatories," said Mayo.
"Exoplanets are a very exciting field of space science. As more planets are discovered, astronomers will develop a much better picture of the mood of exoplanets which in turn will allow us to place our own solar system into a galactic context."
The Kepler space telescope has made huge contributions to the field of exoplanets both in its original mission and its successor K2 mission. So far these missions have provided over 5,100 exoplanet candidates that can now be examined more closely.
With new, upcoming space missions like the James Webb Space Telescope and the Transiting Exoplanet Survey Satellite, astronomers will take exciting new steps toward characterizing and studying exoplanets like the rocky, habitable, Earth-sized planets that might be capable of supporting life.
The Daily Galaxy via Technical University of Denmark
Recommended Space & Science Headlines
|Author:||Y_nezcuttowi_Y [ Fri Feb 16, 2018 9:21 am ]|
|Post subject:||Kepler Mission --Trio of Massive and Dense Planets Unlike An|
Kepler Mission --Trio of Massive and Dense Planets Unlike Any in Our Solar System
A star about 100 light years away in the Pisces constellation, GJ 9827, hosts what may be one of the most massive and dense super-Earth planets detected to date according to new research led by Carnegies Johanna Teske. This new information provides evidence to help astronomers better understand the process by which such planets form.
The GJ 9827 star actually hosts a trio of planets, discovered by NASAs exoplanet-hunting Kepler/K2 mission, and all three are slightly larger than Earth. This is the size that the Kepler mission determined to be most common in the galaxy with periods between a few and several-hundred-days.
Intriguingly, no planets of this size exist in our Solar System. This makes scientists curious about the conditions under which they form and evolve.
One distinctive key to understanding a planets history is to determine its composition. Are these super-Earths rocky like our own planet? Or do they have solid cores surrounded by large, gassy atmospheres?
To try to understand what an exoplanet is made of, scientists need to measure both its mass and its radius, which allows them to determine its bulk density.
When quantifying planets in this way, astronomers have noticed a inclination. It turns out that planets with radii greater than about 1.7 times that of Earth are have a gassy envelope, like Neptune, and those with radii smaller than this are rocky, like our home planet.
Some researchers have proposed that this difference is caused by photoevaporation, which strips planets of their surrounding envelope of so-called volatiles--substances like water and carbon dioxide that have low boiling points--creating smaller-radius planets. But more information is needed to truly test this theory.
This is why GJ 9827s three planets are special--with radii of 1.64 (planet b), 1.29 (planet c) and 2.08 (planet d), they span this dividing line between super-Earth (rocky) and sub-Neptune (somewhat gassy) planets.
Luckily, teams of Carnegie scientists including co-authors Steve Shectman, Sharon Wang, Paul Butler, Jeff Crane, and Ian Thompson, have been monitoring GJ 9827 with their Planet Finding Spectrograph (PFS), so they were capable to constrain the masses of the three planets with data in hand, rather than having to scramble to get many new observations of GJ 9827.
"Usually, if a transiting planet is detected, it takes months if not a year or more to gather enough observations to measure its mass," Teske explained. "Because GJ 9827 is a bright star, we happened to have it in the catalog of stars that Carnegie astronomers been monitoring for planets since 2010. This was unique to PFS."
The spectrograph was developed by Carnegie scientists and mounted on the Magellan Clay Telescopes at Carnegies Las Campanas Obervatory.
The PFS observations indicate that planet b is roughly eight times the mass of Earth, which would make it one of the most-massive and dense super-Earths yet discovered. The masses for planet c and planet d are estimated to be about two and a half and four times that of Earth respectively, although the uncertainty in these two determinations is very high.
This information suggests that planet d has a distinctive volatile envelope, and leaves open the question of whether planet c has a volatile envelope or not. But the better limitation on the mass of planet b suggests that that it is roughly 50 percent iron.
"More observations are needed to pin down the compositions of these three planets," Wang said. "But they do seem like some of the best candidates to test our ideas about how super-Earths form and evolve, potentially using NASAs upcoming James Webb Space Telescope."
The Daily Galaxy via Carnegie Institute
Recommended Space & Science Headlines
|Author:||Y_nezcuttowi_Y [ Sat Jun 23, 2018 2:58 am ]|
|Post subject:||"Two Trillion!" --The New Hubble Estimate of the N|
"Two Trillion!" --The New Hubble Predict of the Number of Galaxies in the Universe
The obervable universe boasts at least 10 times as many galaxies as originally estimated, according to research published on Thursday in The Astrophysical Journal, bring the current predict of an astounding two trillion individual galactic systems.The surprising discovery is the result of a massive galactic survey mined from 15 years worth of deep space observations from the Hubble Space Telescope. An international team led by University of Nottingham astrophysicist Christopher Conselice compiled the Hubble data into a three-dimensional timeline of galactic evolution over the universes history.
It boggles the mind that over 90 percent of the galaxies in the universe have yet to be studied, Conselice said in a statement. Who knows what interesting properties we will find when we notice these galaxies with the next generation of telescopes?
Many of these hidden systems are thought to be around the same scale of the many dwarf galaxies that orbit the Milky Way, rather than a large spiral structure like the Milky Way itself, which helps explains why they have escaped notice for so long.
As Conselice observes, we may be on the brink of rooting out these dimmer galaxies with sophisticated new instruments like the James Webb Space Telescope, set for launch in 2018, or the European Extremely Large Telescope, which is scheduled to receive first light in 2024.
In their research, Conselice and his co-authors determined that the number of galaxies is dwindling over time as these massive star systems blend into ever-larger structures. In the universes infancy the number of galaxies was another tenfold higher, according to the team.
"These results are powerful evidence that a distinctive galaxy evolution has taken place throughout the universes history, which dramatically reduced the number of galaxies through mergers between themthus reducing their total number, Conselice said. This gives us a verification of the so-called top-down formation of structure in the universe.
The Daily Galaxy via Hubble Space Telescope
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