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  1. Finally, some good news. At the centre of the our galaxy there's a supermassive black hole called Sagittarius A*. It has a mass roughly 4 million times that of our Sun. Great news! It turns out scientists have discovered that we're 2,000 light years closer to Sagittarius A* than we thought. This doesn't mean we're currently on a collision course with a black hole. No, it's simply the result of a more accurate model of the Milky Way based on new data. Over the last 15 years, a Japanese radio astronomy project, VERA, has been gathering data. Using a technique called interferometry, VERA gathered data from telescopes across Japan and combined them with data from other existing projects to create what is essentially the most accurate map of the Milky Way yet. By pinpointing the location and velocity of around 99 specific points in our galaxy, VERA has concluded the supermassive black hole Sagittarius A, at the centre of our galaxy, is actually 25,800 light-years from Earth -- almost 2,000 light years closer than what we previously believed. In addition, the new model calculates Earth is moving faster than we believed. Older models clocked Earth's speed at 220 kilometers (136 miles) per second, orbiting around the galaxy's centre. VERA's new model has us moving at 227 kilometres (141 miles) per second. Not bad! VERA is now hoping to increase the accuracy of its model by increasing the amount of points it's gathering data from. By expanding into EAVN (East Asian VLBI Network) and gathering data from a larger suite of radio telescopes located throughout Japan, Korea and China. Source
  2. There's something really weird in the centre of the Milky Way. The vicinity of a supermassive black hole is a pretty weird place to start with, but astronomers have found six objects orbiting Sagittarius A* that are unlike anything in the galaxy. They are so peculiar that they have been assigned a brand-new class - what astronomers are calling G objects. The original two objects - named G1 and G2 - first caught the eye of astronomers nearly two decades ago, with their orbits and odd natures gradually pieced together over subsequent years. They seemed to be giant gas clouds 100 astronomical units across, stretching out longer when they got close to the black hole, with gas and dust emission spectra. But G1 and G2 weren't behaving like gas clouds. "These objects look like gas but behave like stars," said physicist and astronomer Andrea Ghez of the University of California, Los Angeles. Ghez and her colleagues have been studying the galactic centre for over 20 years. Now, based on that data, a team of astronomers led by UCLA astronomer Anna Ciurlo have identified four more of these objects: G3, G4, G5 and G6. And they're on wildly different orbits from G1 and G2 (pictured above); all together, the G objects have orbital periods that range from 170 years to 1,600 years. It's unclear exactly what they are, but G2's intact emergence from periapsis in 2014 - that is, the closest point in its orbit to the black hole - was, Ghez believes, a big clue. "At the time of closest approach, G2 had a really strange signature," she said. "We had seen it before, but it didn't look too peculiar until it got close to the black hole and became elongated, and much of its gas was torn apart. It went from being a pretty innocuous object when it was far from the black hole to one that was really stretched out and distorted at its closest approach and lost its outer shell, and now it's getting more compact again." Previously, it had been thought that G2 was a cloud of hydrogen gas, which was going to get torn apart and slurped up by by Sgr A*, producing some supermassive black hole accretion fireworks. The fact that nothing happened was later referred to as a "cosmic fizzle". The astronomers believe that the answer lies in massive binary stars. Most of the time, these twin stars, locked in a mutual orbit, hang out just doing their buddy star thing. But sometimes - just like colliding binary black holes - they can smoosh into each other, forming one big star. When this happens, they produce a vast cloud of dust and gas that surrounds the new star for about a million years after the collision. "Something must have kept [G2] compact and enabled it to survive its encounter with the black hole," Ciurlo added. "This is evidence for a stellar object inside G2." So what of the other five? Well, they could be binary star mergers too. Most of the stars in the galactic centre are very massive, and most of them are binaries. And the extreme gravitational forces at play around Sgr A* could be enough to destabilise their binary orbits with relative frequency. "Mergers of stars may be happening in the Universe more often than we thought, and likely are quite common," Ghez said. "Black holes may be driving binary stars to merge. It's possible that many of the stars we've been watching and not understanding may be the end product of mergers that are calm now. We are learning how galaxies and black holes evolve. The way binary stars interact with each other and with the black hole is very different from how single stars interact with other single stars and with the black hole." It does seem like the G objects have a lot in common, whatever they are, and expanding the dataset can only provide more information to tease out the puzzle. There is, however, still a lot to figure out. Like some mysterious fireworks spotted flaring out of Sgr A* last year. Was that a delayed reaction from G2's periapsis? Was the cosmic fizzle not so fizzly after all? We might just have to keep watching this weird little supermassive black hole corner of space to see what happens next... The research has been published in Nature. source
  3. Astronomers believe the young Milky Way once swallowed a dwarf galaxy Their findings could change what we know about the Milky Way’s formation. MARIANA SUAREZ via Getty Images Astronomers believe they've mapped an important sequence of events that shaped our galaxy 10 billion years ago. In a paper published in Nature Astronomy today, researchers from the Instituto de Astrofisica de Canarias(IAC) share their findings that a dwarf galaxy, Gaia-Enceladus, once collided and merged with the early Milky Way. Their discovery offer a new understanding of how the Milky Way formed. Astronomers previously believed that the galaxy was made of two separate sets of stars, but exactly how or when they came together was a mystery. Using the Gaia space telescope, these researchers were able to take more precise measurements of the position, brightness and distance of roughly one million stars. They also looked at the density of "metals," or elements without hydrogen or helium, that the stars contain. The researchers determined that both sets of stars are about the same age but that one was set into "chaotic motion," evidence of a galaxy collision. The researchers believe Gaia-Enceladus collided with the young Milky Way about 10 billion years ago, and over the course of millions of years, the Milky Way consumed the dwarf galaxy. The researchers also determined that the collision contributed to a four-billion-year stretch of star formation, and gas from that activity settled to form the "thin disk" that runs through the center of the Milky Way. They believe the remnants of Gaia-Enceladus eventually formed the halo of the present-day Milky Way. According to the researchers, this information provides "unprecedented detail" about the early stages of our cosmic history. Of course, it's not the first time we've heard of one galaxy consuming another. In fact, our galactic neighbor Andromeda cannibalized a nearby galaxy some two billion years ago, and it's on track to collide with the Milky Way in the very distant future. Source: Astronomers believe the young Milky Way once swallowed a dwarf galaxy
  4. (ESO/S. Brunier) Are Earth, The Solar System, And The Milky Way Gaining or Losing Mass? According to the most widely-accepted cosmological models, the first galaxies began to form between 13 and 14 billion years ago. Over the course of the next billion years, the cosmic structures we've all come to know emerged. These include things like galaxy clusters, superclusters, and filaments, but also galactic features like globular clusters, galactic bulges, and Supermassive Black Holes (SMBHs). However, like living organisms, galaxies have continued to evolve ever since. In fact, over the course of their lifetimes, galaxies accrete and eject mass all the time. In a recent study, an international team of astronomers calculated the rate of inflow and outflow of material for the Milky Way. Then the good folks at astrobites gave it a good breakdown and showed just how relevant it is to our understanding of galactic formation and evolution. The study was led by ESA astronomer Andrew J. Fox and included members from the Space Telescope Science Institute's (STScI) The Milky Way Halo Research Group, and multiple universities. Based on previous studies, they examined the rate at which gas flows in and out of the Milky Way from surrounding high-velocity clouds (HVC). Since the availability of material is key to star formation in a galaxy, knowing the rate at which it is added and lost is important to understanding how galaxies evolve over time. And as Michael Foley of astrobites summarized, characterizing the rates at which material is added to galaxies is crucial to understanding the details of this "galactic fountain" model. In accordance with this model, the most massive stars in a galaxy produce stellar winds that drive material out of the galaxy disk. When they go supernova near the end of their lifespans, they similarly drive most of their material out. This material then infalls back into the disk over time, providing material for new stars to form. "These processes are collectively known as 'stellar feedback', and they are responsible for pushing gas back out of the Milky Way," said Foley. "In other words, the Milky Way is not an isolated lake of material; it is a reservoir that is constantly gaining and losing gas due to gravity and stellar feedback." In addition, recent studies have shown that star formation may be closely related to the size of the Supermassive Black Hole (SMBH) at a galaxy's core. Basically, SMBHs put out a tremendous amount of energy that can heat gas and dust surrounding the core, which prevents it from clumping effectively and undergoing gravitational collapse to form new stars. The location of the Sun relative to Scutum-Centaurus star forming region. (Bill Saxton, NRAO/AUI/NSF; Robert Hurt, NASA.) As such, the rate at which material flows in and out of a galaxy is key to determining the rate of star formation. To calculate the rate at which this happens for the Milky Way, Fox and his colleagues consulted data from multiple sources. As Fox told Universe Today via email: "We mined the archive. NASA and ESA maintain well-curated archives of all Hubble Space Telescope data, and we went through all the observations of background quasars taken with the Cosmic Origins Spectrograph (COS), a sensitive spectrograph on Hubble that can be used to analyze the ultraviolet light from distant sources. We found 270 such quasars. First, we used these observations to make a catalog of fast-moving gas clouds known as high-velocity clouds (HVCs). Then we devised a method for splitting the HVCs into inflowing and outflowing populations, by making use of the Doppler shift." In addition, a recent study showed that the Milky Way experienced a dormant period roughly 7 billion years ago – which lasted for about 2 billion years. This was the result of shock waves that caused interstellar gas clouds to become heated, which temporarily caused the flow of cold gas into our galaxy to stop. Over time, the gas cooled and began flowing in again, triggering a second round of star formation. After looking at all the data, Fox and his colleagues were able to place constraints on the rate of inflow and outflow for this galaxy of ours: "After comparing the rates of inflowing and outflowing gas, we found an excess of inflow, which is good news for future star formation in our Galaxy, since there is plenty of gas that can be converted into stars and planets. We measured about 0.5 solar masses per year of inflow and 0.16 solar masses per year of outflow, so there's a net inflow." Fermi bubble. (NASA's Goddard Space Flight Center) However, as Foley indicated, HVCs are believed to live for periods of only about 100 million years or so. As a result, this net inflow cannot be expected to last indefinitely. "Finally, they ignore HVCs that are known to reside in structures (such as the Fermi Bubbles) that don't trace the inflowing or outflowing gas," he adds. Since 2010, astronomers have been aware of the mysterious structures emerging from the center of our galaxy known as Fermi Bubbles. These bubble-like structures extend for thousands of light-years and are thought to be the result of SMBH's consuming interstellar gas and belching out gamma rays. However, in the meantime, the results provide new insight into how galaxies form and evolve. It also bolsters the new case made for "cold flow accretion", a theory originally proposed by Prof. Avishai Dekel and colleagues from The Hebrew University of Jerusalem's Racah Institute of Physics to explain how galaxies accrete gas from surrounding space during their formation. "These results show that galaxies like the Milky Way do not evolve in a steady state," Fox summarized. "Instead they accrete and lose gas episodically. It's a boom and bust cycle: when gas comes in, more stars can be formed, but if too much gas comes in, it can trigger a starburst so intense that it blows away all the remaining gas, shutting off the star formation. Thus the balance between inflow and outflow regulates how much star formation occurs. Our new results help to illuminate this process." Another interesting takeaway from this study is the fact that what applies to our Milky Way also applies to star systems. For instance, our Solar System is also subject to the inflow and outflow of material over time. Objects like 'Oumuamua and the more recent 2I/Borisov confirm that asteroids and comets are kicked out of star systems and scooped up by others regularly. But what about gas and dust? Is our Solar System and (by extension) planet Earth losing or gaining weight over time? And what could this mean for the future of our system and home planet? For example, astrophysicist and author Brian Koberlein addressed the latter issue in 2015 on his website. Using the then-recent Gemini meteor shower as an example, he wrote: "In fact from satellite observations of meteor trails it's estimated that about 100 – 300 metric tons (tonnes) of material strikes Earth every day. That adds up to about 30,000 to 100,000 tonnes per year. That might seem like a lot, but over a million years that would only amount to less than a billionth of a percent of Earth's total mass." However, as he goes on to explain, Earth also loses mass on a regular basis through a number of processes. These include radioactive decay of material in the Earth's crust, which leads to energy and subatomic particles (alpha, beta and gamma-rays) leaving our planet. A second is atmospheric loss, where gases like hydrogen and helium will be lost to space. Together, these add up to a loss of about 110,000 tonnes per year. Small asteroid 'bolide' impacts between 1994-2013. (NASA) On the surface, this would seem like a net loss of about 10,000 or more tonnes annually. What's more, microbiologist/science communicator Chris Smith and Cambridge physicist Dave Ansell estimated in 2012 that the Earth gains 40,000 tonnes of dust a year from space, while it loses 90,000 a year through atmospheric and other processes. So it may be possible that Earth is getting lighter at a rate of 10,000 to 50,000 tonnes a year. However, the rate at which material is being added is not well constrained at this point, so it is possible that we might be breaking even (though the possibility that Earth is gaining mass seems unlikely). As for our Solar System, the situation is similar. One the one hand, interstellar gas and dust flows in all the time. On the other hand, our Sun – which accounts for 99.86 percent of the Solar System's mass – is also shedding mass over time. Using data gathered by NASA's MESSENGER probe, a team of NASA and MIT researchers concluded that the Sun is losing mass due to solar wind and interior processes. According to Ask an Astronomer, this is happening at a rate of 1.3245 x 10^15 tonnes a year even though the Sun is expanding simultaneously. That's a staggering number, but since the Sun has a mass of about 1.9885 × 10^27 tonnes. So the Sun won't be winking out anytime soon. But as it loses mass, its gravitational influence on Earth and the other planets will diminish. However, by the time our Sun reaches the end of its main sequence, it will expand considerably and could very well swallow Mercury, Venus, Earth and even Mars completely. So while our galaxy may be gaining mass for the foreseeable future, it looks like our Sun and Earth itself are slowly losing mass. This should not be seen as bad news, but it does have implications in the long run. In the meantime, it's kind of encouraging to know that even the oldest and most massive objects in the Universe are subject to change like living creatures. Whether we're talking about planets, stars, or galaxies, they are born, they live, and they die. And in between, they can be trusted to put on or lose a few pounds. The circle of life, played out on the cosmic scale! This article was originally published by Universe Today. Read the original article. Source: Are Earth, The Solar System, And The Milky Way Gaining or Losing Mass?
  5. The galaxy is not flat, researchers show in new 3D model of the Milky Way Six years of tracking a special class of star have yielded a new and improved 3D model of our galaxy, based on direct observation rather than theoretical frameworks. And although no one ever really thought the Milky Way was flat flat, the curves at its edges have now been characterized in better detail than ever before. Researchers at the University of Warsaw in Poland took on this challenge some time ago with the desire to observe the shape of the galaxy directly rather than indirectly; although we have a good idea of the shape, that idea is based on models that involve assumptions or observations of other galaxies. Imagine if you wanted to know the distance to the store, but the only way you could tell was by looking out the window and observing how long it took for someone to get there and back; by calculating their average walking speed you can get a general idea. Sure, it works to a point — but wouldn’t it be nice to just lean out the window and see exactly how far it is? The trouble in astronomy is it can be incredibly difficult to make such direct observations with our present tools, so we rely on indirect ones (like timing people above), something that can be helpful and even accurate but is no substitute for the real thing. Fortunately, the researchers found that a certain type of star has special qualities that allow us to tell exactly how far away it is. “Cepheid variable stars” are young stellar bodies that burn far brighter than our own sun, but also pulse in a very stable pattern. Not only that, but the frequency of that pulsing corresponds directly to how bright it gets — sort of like a strobe that, as you turn the speed up or down, also makes it dimmer or brighter. What this means is that if you know the frequency of the pulses, you know objectively how much light the star puts out. And by comparing that absolute amount to the amount that reaches us, you can tell with remarkable precision how far that light has had to travel. “Distances to Cepheids can be measured with an accuracy better than 5%,” said lead author Dorota Skowron in a video explaining the findings. In comments to Space.com, she added: “It is not some statistical fact available only to a scientist’s understanding. It is apparent by eye.” Not only are these beacons reliable, they’re everywhere — the team located thousands of Cepheid variable stars in the sky via the Optical Gravitational Lensing Experiment, a project that tracks the brightness of billions of stellar objects. They carefully cataloged and observed these Cepheids (highlighted in the top image) for years, and from repeated measurements emerged a portrait of the galaxy — a curved portrait. “Our map shows the Milky Way disk is not flat. It is warped and twisted far away from the galactic center,” said co-author Przemek Mroz. “This is the first time we can use individual objects to show this in three dimensions,” some, he said, “as distant as the expected boundary of the Galactic disk.” The galaxy curves “up” on one side and “down” on the other, a bit like a hat with the brim down in front and up in back. What caused this curvature is unknown, but of course there are many competing theories. A close call with another galaxy? Dark matter? They’re working on it. The researchers were also able to show by measuring the age of the stars that they were created not regularly but in bunches — direct evidence that star formation is not necessarily constant, but can happen in bursts. Their findings were published today in the journal Science. Image Credits: Skowron et al. Source: The galaxy is not flat, researchers show in new 3D model of the Milky Way
  6. Milky Way's center will be revealed by NASA's Webb Telescope The center of our Milky Way galaxy is hidden from the prying eyes of optical telescopes by clouds of obscuring dust and gas. But in this stunning vista, the Spitzer Space Telescope's infrared cameras penetrate much of the dust, revealing the stars of the crowded galactic center region. The upcoming Webb telescope will offer a much-improved infrared view, teasing out fainter stars and sharper details. Credit: NASA, JPL-Caltech, Susan Stolovy (SSC/Caltech) et al. The center of our galaxy is a crowded place: A black hole weighing 4 million times as much as our sun is surrounded by millions of stars whipping around it at breakneck speeds. This extreme environment is bathed in intense ultraviolet light and X-ray radiation. Yet much of this activity is hidden from our view, obscured by vast swaths of interstellar dust. NASA's upcoming James Webb Space Telescope is designed to view the universe in infrared light, which is invisible to the human eye, but is very important for looking at astronomical objects hidden by dust. After its launch, Webb will gather infrared light that has penetrated the dusty veil, revealing the galactic center in unprecedented detail. "Even one image from Webb will be the highest quality image ever obtained of the galactic center," said Roeland van der Marel of the Space Telescope Science Institute (STScI), principal investigator on one planned study that will focus on imaging. Telescopes on the ground and in space have provided tantalizing glimpses of the residents of the galactic center. Astronomers have tracked stars orbiting the black hole, some of which approach close enough to provide a test of Einstein's general theory of relativity. However, so far, only the brightest stars are detectable. "We're only seeing the tip of the iceberg from the ground. Webb will be able to study fainter stars and tell us more about the overall stellar population," said Torsten Böker of the European Space Agency and STScI, a co-investigator on a second planned study of the galactic center that will focus on spectroscopy. Scientists already have been surprised to find low-mass infant stars forming close to the supermassive black hole—some within just a few light-years of its grasp. Theoretically, the black hole's immense gravity and harsh radiation environment should disrupt any gas clouds and prevent them from collapsing into stars. Yet these baby stars called protostars have persisted. Webb's observations may reveal additional protostars, and could provide clues to how stars can form in such an unlikely spot. Black Hole Mysteries The Milky Way's supermassive black hole, known to astronomers as Sagittarius A* (pronounced A-star) also will fall under Webb's gaze. It is surrounded by a disk of gas and dust, some of which will inevitably fall into the black hole. Astronomers have observed flares of light when the black hole gulped a clump of material. However, they have never detected the glow from the black hole's disk. "Detecting the disk around Sagittarius A* with Webb would be a home run," Böker said. Infrared observations using the ground-based Keck telescope have allowed astronomers to track individual stars orbiting the black hole at the galactic center. Webb is expected to detect fainter stars than are shown here, providing a more complete census of the stellar population within the galactic core. Credit: Keck/UCLA Galactic Center Group Data from Webb also could help address broader questions of how galaxies form—such as the longstanding "chicken and egg" problem of which came first, the galaxy or the black hole. "Does the black hole come first and stars form around it? Do stars gather together and collide to form the black hole? These are questions we want to answer," said Jay Anderson of STScI, a co-investigator on one of the studies. Additionally, studies have shown that the mass of a galaxy's central black hole is related to the total mass of the surrounding stars, but the reasons for this relationship remain unknown. "Are there any clues to this mass correlation close to the black hole? Or has recent star formation wiped out signs of what might have happened in the past?" added Marcia Rieke of the University of Arizona, principal investigator on Webb's NIRCam instrument. Serendipitous Possibilities Ultimately, the most exciting results from Webb's observations might be the unexpected. For example, Webb might find stars in unusual orbits. Or, Webb might spot a gas cloud destined to be ripped apart by gravitational forces. "We would like to see something unusual, like a star being gobbled up," said van der Marel. Ideally, these initial studies of the galactic center will inform future Webb observations. By revisiting the galactic center over a period of several years, astronomers can gain a new understanding of this chaotic region of space. "So many interesting, strange things happen at the centers of galaxies. We want to find out what's happening in our own," said Rieke. The observations described here will be taken as part of Webb's Guaranteed Time Observation (GTO) program. The GTO program provides dedicated time to the scientists who have worked with NASA to craft the science and instrument capabilities of Webb throughout its development. Source: Milky Way's center will be revealed by NASA's Webb Telescope
  7. There could be up to 10 billion warm and cozy Earth-like planets in our home galaxy, new research reveals An artist's concept of the planet Kepler-452b (right), the first near-Earth-size world to be found in the habitable zone of a star that is similar to our sun. The planet is 60% larger than Earth (shown left for comparison). NASA/Ames/JPL-Caltech Using data from NASA's planet-hunting Kepler telescope, scientists have estimated that one in every four sun-sized stars has an Earth-like planet orbiting it. That translates to about 10 billion planets in our galaxy that could hold liquid water— which could make them habitable to alien life. Understanding how many potentially habitable planets exist in the Milky Way could help researchers plan future projects to search for signs of alien life. Our galaxy could be littered with warm, watery planets like Earth. That's the conclusion of researchers at Penn State University, who used data from NASA's Kepler telescope to estimate the number of Earth-like planets in the Milky Way. Their results, published in The Astronomical Journal this week, suggest that an Earth-like planet orbits one in every four sun-like stars. Totaled up, that means there could be up to 10 billion Earth-like worlds in our home galaxy. The estimate is an important step in the search for alien life, since any potential life on other planets would most likely be found on an Earth-like world warm enough to hold liquid water. So a better understanding of the potential number of Earth-like planets in the galaxy can inform projects like the Wide-Field Infrared Survey Telescope, which will launch into space in the mid 2020s and hunt signs of for oxygen and water vapor on distant planets. "We get a lot more return on our investment if we know when and where to look," Eric Ford, a professor of astrophysics and co-author of the new study, told Business Insider. Ford's team defined an Earth-like planet as being anywhere from three-quarters to one-and-a-half times the size of Earth, and orbiting its star every 237 to 500 days. That's presumably within the star's habitable zone — the "range of orbital distances at which the planets could support liquid water on their surfaces," as Ford described it in a press release. "For astronomers who are trying to figure out what is a good design for the next major space observatory, this piece of information is an integral part of that planning process," he said. 5 to 10 billion planets like Earth Earth-like planets have varying sizes and compositions. NASA/JPL-Caltech/R. Hurt (SSC-Caltech) The researchers' estimate is based on data from NASA's Kepler space telescope. Launched in 2009, the telescope used what's known as the transit method to find worlds outside our solar system. It watched over 530,000 stars for tiny dips in a star's brightness that could be caused by a planet passing in front of it — transits, in other words. This work transformed our understanding of the galaxy. Kepler found more than 2,600 exoplanets, revealed that there are more planets than stars in the Milky Way, and gave researchers new insight into the diversity of planet types. The telescope also allowed scientists to confirm for the first time that many exoplanets are similar to Earth. The telescope retired last year after it ran out of fuel, but passed the planet-hunting torch to the Transiting Exoplanet Survey Satellite (TESS), which launched in April 2018. An illustration of NASA's Kepler space telescope. NASA Overall, Kepler's results suggested that 20% to 50% of the stars visible in the night sky had Earth-like planets in their habitable zones. But Ford's team didn't want to estimate the number of Earth-like planets in the galaxy based solely on the exoplanets Kepler found, because the transit method is only good at detecting large planets close to their stars (since they block out more light). It's not great, however, at finding small planets farther from their stars. Plus, Kepler's method was biased toward small, dim stars about one third the mass of our sun. Workers at the Hazardous Processing Facility at Astrotech in Titusville, Florida prepare a scale to weigh the Kepler spacecraft, in the background. NASA/Jim Grossmann So to estimate how many planets Kepler might have missed, the researchers created computer simulations of hypothetical universes of stars and planets, based on a combination of Kepler's planet catalogue and a survey of our galaxy's stars from the European Space Agency's Gaia spacecraft. Then the researchers' program "observed" those stars as Kepler would have. The simulation gave the scientists a sense of how many exoplanets in each hypothetical universe Kepler would have detected, and which kinds. They could then compare that data to what the real Kepler telescope detected in our universe to estimate the abundance of Earth-sized planets in the habitable zones of sun-like stars. "There are significant uncertainties in what range of stars you label 'sun-like,' what range of orbital distances you consider to be 'in the habitable zone,' what range of planet sizes you consider to be 'Earth-like,'" Ford said. "Given those uncertainties, both 5 and 10 billion are reasonable estimates." Improving the search for aliens An illustration of a potentially habitable exoplanet 31 light-years from Earth. NASA's Goddard Space Flight Center/Chris Smith The next step in the search for alien life is to study potentially habitable planets to figure out what they're made of. "Scientists are particularly interested in searching for biomarkers — molecules indicative of life — in the atmospheres of roughly Earth-size planets," Ford said. Even if a planet is in a star's habitable zone, it still needs a substantial atmosphere to trap enough heat to sustain liquid water on its surface. Scientists can calculate the composition of an exoplanet's atmosphere by measuring how its star's light behaves as it passes through. This is where Ford's research comes into play: If Earth-like worlds are abundant, there could be enough of them close by for NASA scientists to study with a smaller, cheaper telescope. If all the Earth-y worlds are far away, though, NASA would need to rely on more far-reaching telescopes. The researchers recommended that future space missions plan for a range of possible incidences of Earth-like planets — between one for every 33 sun-like stars and one for every two sun-like stars. "One of the important things here is not just giving a single number but understanding the range of possibilities," Ford said. "So that people who have to make decisions could hope for the best and plan for the worst and still be able to come up with a solid scientific strategy." Source: There could be up to 10 billion warm and cozy Earth-like planets in our home galaxy, new research reveals
  8. The Milky Way Steals From Its Neighbors Galaxies seem eternal, yet they actually change over time. (Photo by: Photo12/Universal Images Group via Getty Images)UNIVERSAL IMAGES GROUP VIA GETTY IMAGES It’s common to think of the universe as static and unchanging, with vast spiral galaxies rotating slowly, but otherwise existing as a stately and eternal work of cosmic art. However, we know this to be false and it only seems to be true because of the vastly different timescales that govern human lives and the motion of galaxies. Galaxies can tear themselves apart in violent collisions that spread stars over millions of light years. And it’s not just happening “out there.” For instance, our own Milky Way galaxy might have a somewhat checkered past. Recent calculations and measurements have revealed that our Milky Way has stolen dwarf galaxies from its largest galactic satellite, the Large Magellanic Cloud (LMC). The Large Magellanic cloud (top right) and Small Magellanic cloud (bottom right), set against the center of the Milky Way galaxy (Photo by: VW Pics/Universal Images Group via Getty Images)UNIVERSAL IMAGES GROUP VIA GETTY IMAGES Stars have planets and planets can have moons. What is less well known is that galaxies can be surrounded by other and smaller dwarf galaxies. The most familiar dwarf galaxies that surround our Milky Way, are the Large and Small Magellanic Clouds (SMC), which can be seen in the Southern hemisphere as faint smudges. These two dwarf galaxies contain many stars within them (SMC, several hundred million, and LMC, about thirty billion) and are small in comparison to the Milky Way, with its 200 to 400 billion stars. The Milky Way is known to have over fifty dwarf galaxies, most of them smaller and fainter than the Magellanic clouds. And dwarf galaxies are quite interesting for a surprising reason – they are inextricably tied up in our understanding of a mysterious substance in the universe called dark matter. This artist’s impression depicts our home Galaxy, the Milky Way, embedded in a spherical halo of dark matter (shown in blue). (Image credit: ESO/L Calçada.)EUROPEAN SOUTHERN OBSERVATORY/L CALÇADA. Dark matter is thought to be a type of matter that does not absorb or emit light, making it completely invisible (hence the name). Dark matter has never been directly observed and its existence has been inferred only indirectly by its effect on the rotation speed of galaxies or by the motion of clusters of galaxies that are bound together by gravity. Averaged over the entire universe, astronomers believe that there is five times more dark matter than the hydrogen and helium that makes up the stars and galaxies of ordinary matter. Dark matter is thought to exist in large clouds that surround the familiar galaxies seen in the dazzling pictures taken by the Hubble Telescope, and there is considerable circumstantial evidence that this is true. However, an unappreciated consequence of having the visible matter of galaxies embedded in a much larger cloud of dark matter is that a galaxy like the Milky Way should be surrounded by perhaps several hundred dwarf galaxies. And for a long time, this didn’t seem to be true. Astronomers knew of the Magellanic clouds and a few others, but the numbers didn’t seem to add up. Accordingly, searches for additional dwarf galaxies surrounding the Milky Way have become common, with some success and a growing population. For instance, the Sagittarius Dwarf galaxy, which is the closest known companion to the Milky Way, was discovered as recently as 1994. The reason it took so long to find is because it is located behind the center of the Milky Way and it is therefore very difficult to image. Stellar streams around the Milky Way Galaxy. Image credit: NASA / JPL-Caltech / R. Hurt, SSC & Caltech.NASA / JPL-CALTECH / R. HURT, SSC & CALTECH. In a recent study of the motion of faint galactic neighbors, researchers made a surprising discovery. Of the known dwarf galaxies orbiting the Milky Way, several of them, including the Small Magellanic Cloud, two smaller classical dwarfs (called Carina and Fornax, with a few hundred thousand stars), and at least four ultrafaint dwarfs (containing as few as five to ten thousand stars) were once gravitationally connected to the Large Magellanic Cloud. However, in the vicinity of the Milky Way, the much larger galaxy’s strong gravitational field captured them and they now orbit the Milky Way, rather than the LMC. The recent research hints that perhaps there are other ultrafaint dwarfs who have experienced a similar fate, but it will require additional data to make any conclusive assertions. Further study is required, but the observation that small galaxies currently trapped in the Milky Way’s gravitational field originally orbited a different small galaxy that is now orbiting the Milky Way, has validated the techniques used in this study and may lead to a more nuanced appreciation of the interplay between dark matter and ordinary matter as the Milky Way grew to its present size. Until dark matter is directly observed, it will be these ever more sophisticated studies that will help astronomers refine our appreciation of this elusive substance. An increasing understanding of the nature of dark matter in cosmological contexts is perhaps the most scientifically-substantive aspect of this study, but there is one that is a little more fun. The fact that the Milky Way has stolen tiny galaxies from its small neighbors leads us to an inescapable conclusion. Our galaxy is a bully. Source: The Milky Way Steals From Its Neighbors
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