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  • richardmitnick 11:42 am on May 8, 2020 Permalink | Reply
    Tags: "As the climate shifts a border moves", , , EarthSky   

    From EarthSky: “As the climate shifts, a border moves” 


    From EarthSky

    May 8, 2020
    Elza Bouhassira

    Italy’s northern border with Switzerland depends on the natural, morphological boundaries of glaciers’ frontiers. But in recent years, glaciers have been melting at increased rates due to climate change. This has caused the border to shift noticeably.

    Mount Similaun glacier, where the border between Italy and Austria drifts with the ice. Image via Delfino Sisto Legnani/ Italian Limes.

    Rifugio Guide del Cervino, a small mountain restaurant, opened in 1984 at a location high in the Italian Alps; now it might be in Switzerland. The restaurant has become the subject of a dispute between the two states due to a legal agreement which allows Italy’s northern border to move with the natural, morphological boundaries of glaciers’ frontiers, which largely follow the watersheds on either side of the ridges. The moving border has shifted over the last fifteen years since its creation as glaciers retreat and the restaurant may now be in Swiss territory. If decided to be in Switzerland, the restaurant would be subject to Swiss law, taxes, and potentially even customs; Swiss inspectors would need to approve every box of pasta and package of coffee brought up to the restaurant by cable car from Italy.

    Rifugio Guide Del Cervino. Image via Franco56/ Wikimedia Commons.

    Borders can follow artificial paths, like those on maps forming perfectly straight lines, independent of the physical and cultural landscapes they may be mincing. Others are fixed by natural boundaries like the Niagara River separating the U.S. and Canada.

    However, not all natural boundaries are as stable as they might appear. Italy, Austria, and Switzerland’s shared borders depend on the limits of the glaciers and they have been melting at increased rates due to climate change. This has caused the border to shift noticeably in recent years. The border lies primarily at high altitudes, among tall mountain peaks where it crosses white snowfields and icy blue glaciers.

    The moving border is an unprecedented legal concept. It was established through an agreement between Italy and Austria in 2006 and another between Italy and Switzerland in 2009. France did not sign such an agreement because of post-World War II territorial gains on the Italian side of the watershed it did not want to risk losing.

    The moving border’s flexibility is a highly unusual case in a world where many borders serve to mark defined lines of inclusion and exclusion. International lawyer and Roma Tre University human rights professor Alice Riccardi told GlacierHub:

    “Borders today move following the policies of exclusion from/inclusion in pursued by States. For instance, when it comes to migration, EU South external borders happen to be already in Africa, where migrants are prevented from embarking towards Europe.”

    Since 2008, the Istituto Geografico Militare (IGM), which has defined and maintained Italy’s state borders since 1865, has conducted high-altitude survey expeditions every two years to search for shifts in the border and subsequently to update official maps. The collaborative team that conducts the survey is composed of an equal number of experts from IGM and representatives from cartographic institutes of neighboring states.

    The concept of the moving border captured the attention of Marco Ferrari, an architect, and Dr. Elisa Pasqual, a visual designer. In 2014, they launched a research project and interactive installation called Italian Limes focused on the moving border. The word limes comes from Latin and was used by the Romans to describe a nebulous, unfixed fringe zone on the edge of their territorial control. The Romans viewed limes as ebbing and flowing as the Roman army advanced and retreated similar to how today the border moves as the ice drifts.

    The project, featured in the 2014 Venice Biennale, explores the limits of natural borders when they are tested by long-term ecological processes and reveals how climate change has begun to wear on Western ideas of territory and borders. Ferrari told GlacierHub:

    The project makes the speed of climate change visible because we are used to thinking of borders, glaciers, and mountains as things that stay fixed.

    “Climate change changes our conception of territory in a way that is not just material, it’s not just a disruption of infrastructure, but also of the geographical imagery of the planet itself. So the very idea of the border is put into crisis by climate change in this sense, it almost contradicts the possibility of being able to trace a border.”

    One of the high-precision GPS measurement tools used by the project at Grafferner Glacier. Image via Delfino Sisto Legnani/ Italian Limes.

    The Italian Limes project takes measurements at the 1.5-kilometer (.9 mile) long Grafferner Glacier near Mount Similaun in the Ötztal Alps at the border of Italy and Austria. GPS measurement units were installed at the site to track changes to the glacier and watershed which broadcast their data to a machine, which prints a real-time representation of the moving border. Ferrari explained to GlacierHub:

    “By looking at the history of the border we came across this specific moment in time of the mobile border that was initially presented to us as an anecdote, as a funny curiosity, a weird glitch in the normal diplomatic management of the relationship between countries. Because of how it was presented to us, we almost didn’t focus on it, but on second thought we saw that this was the nexus that could allow us to talk about all the things we wanted to talk about; it could allow us to reveal the contradiction in this idea of a natural border – how even the mountains, even the watershed, even glaciers aren’t something that is forever, the fact that they are chosen to be borders is a clear political act and when these things move the contradiction gets exposed”

    The installation showing a live representation of the border at ZKM, Karlsruhe. Image via Delfino Sisto Legnani/ Italian Limes.

    The project grew to the point that Ferrari and Pasqual teamed up with architect and editor Andrea Bagnato to create “A Moving Border: Alpine Cartographies of Climate Change,” a 2019 book which builds on Italian Limes to map out the effects of climate change on geopolitical understandings of the border. Bagnato told GlacierHub:

    The Alps in the Trentino province of Italy. Image via Nawarona/ Flickr.

    Ultimately, the effects of climate change will introduce stresses that borders cannot keep under control. The new, quick changes to the moving border are only one such instance. The U.S. state of Louisiana is rapidly losing ground to the waters on its coast. India and Bangladesh were involved in a dispute over who controlled an uninhabited sandbar that vanished beneath the rising seas. The province of Kashmir has long been a point of contention between Pakistan and India. If its glaciers melt and regional freshwater supply is put under great stress, conflict for control of the province could escalate significantly.

    In an interview with Vice, Ferrari said:

    Even the biggest and most stable things, like glaciers, mountains – these huge objects, they can change in a few years. We live on a planet that changes, and we try to make rules, to give meaning, but this meaning is completely artificial because nature, basically, doesn’t give a s**t.

    See the full article here .

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Deborah Byrd created the EarthSky radio series in 1991 and founded EarthSky.org in 1994. Today, she serves as Editor-in-Chief of this website. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in her honor. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. “Being an EarthSky editor is like hosting a big global party for cool nature-lovers,” she says.

  • richardmitnick 7:54 am on April 30, 2020 Permalink | Reply
    Tags: "Will Dragonfly find dust devils on Titan?", EarthSky,   

    From EarthSky: “Will Dragonfly find dust devils on Titan?” 


    From EarthSky

    April 30, 2020
    Paul Scott Anderson

    Earth and Mars both are known to have swirling dust devils moving along their surfaces. Saturn’s large moon Titan might have them, too, according to a new study. If so, NASA’s planned Dragonfly mission will be able to find them.

    NASA The Dragonfly mission to Titan

    Titan has vast fields of sand dunes, similar to those on Earth and Mars. New research suggests that dust devils might play a role in their formation. Image via NASA/ JPL-Caltech/ Sci-News.com.

    Dust devils – short-lived whirlwinds filled with dust grains – are common on Earth, and even on Mars, where various rovers and orbiters have observed them many times. Now there’s another world in the solar system where dust devils might roam, according to a new study from researchers at Boise State University in Idaho. It’s Saturn’s large moon, Titan! And NASA’s planned Dragonfly mission – a drone-like flying robot able to perform vertical-takeoffs and landings – will be able to find them.

    The intriguing possibility of dust devils on Titan was the subject of a recent post in AGU Blogosphere by Liza Lester of the American Geophysical Union. The new peer-reviewed paper detailing the dust devil research was published in Geophysical Research Letters on March 3, 2020.

    From the paper:

    “Saturn’s moon Titan may host active dust devils, small dust-laden plumes, which could significantly contribute to transport of dust in that moon’s atmosphere. Although the exact nature of dust on Titan is unclear, previous observations confirm that there is actively blowing dust on that world. If dust devils are active on Titan’s surface, NASA’s upcoming Dragonfly mission is likely to encounter them, but dust devils on Titan are unlikely to pose a hazard to the mission.

    The arrival of NASA’s Dragonfly mission on Titan in 2034 presents the prospect of probing extraterrestrial vortices in a similar way to these field studies, although encounters will probably occur primarily while Dragonfly is on the ground. However, Titan’s relevant meteorological conditions suggest that vortex encounters, if in-flight, may occur a few times during Dragonfly’s daily flight. The low wind speeds expected for dust devils on Titan mean they will pose little to no hazard to the mission. However, Dragonfly will spend most of its time on the ground, including during Titan’s midday when vortices are most likely to be active, and so encounters will probably occur on the ground every few Earth hours instead. In this case, they will likely resemble encounters on Mars by landed spacecraft. Even then, though, the imagery and meteorological data collected by Dragonfly during encounters may break new ground in aeolian studies by showing how they operate in a new aerodynamic environment.”

    It’s been known for some time now, thanks to the Cassini mission to Saturn and its moons, that Titan has vast expanses of sand dunes (composed of organic hydrocarbon particles, unlike Earth and Mars).

    NASA/ESA/ASI Cassini-Huygens Spacecraft

    Winds on Titan are typically rather weak, but the dune particles do get transported around, and dust devils might be an ideal mechanism for that to happen. As Brian Jackson, a planetary scientist at BSU said in a statement:

    “Winds at the surface of Titan are usually very weak. Unless there is a big storm rolling through, there’s probably not that much wind, and so dust devils may be one of the main dust transport mechanisms on Titan, if they exist.”

    So far, dust devils haven’t actually been seen yet on Titan, but meteorological models, based on data from the Huygens probe which landed on Titan in 2005, suggest they should be possible. Jackson said:

    “When we plug the numbers in for how much dust the dust devil ought to lift based on the wind speeds we see, they seem to be able to lift more dust than we would expect. There may be some other mechanism which is helping them pull this dust, or the equations are just wrong.”

    ESA/Huygens Probe from Cassini landed on Titan

    On Earth, dust devils are very common (I remember even being briefly caught in a small one when I was a kid). In order to get more insight into how earthly dust devils form, Jackson and his colleagues studied ones in southeastern Oregon’s Alvord Desert, using small airborne drones carrying meteorological instruments. Those findings can be compared with observations of dust devils on Mars. According to Jackson:

    “We can watch dust devils skitter across the surface of Mars and see what their internal structure is like, but that doesn’t tell us how much dust they are lifting. Mars’ atmosphere is really, really dusty and dust plays an important role in the climate. Dust devils are probably, if not the dominant mechanism, one of the most important mechanisms for lofting the dust.”

    Mars’ atmosphere is extremely thin, yet dust devils can still reach a height of five miles (eight km). This is especially true during the martian summer. Mars is very dusty – dust is literally everywhere – and that dust can be carried all over the planet despite the thinness of the atmosphere. The planet even experiences periodic global dust storms.

    So how does this apply to Titan?

    Dust Devils on Mars Seen by NASA’s Curiosity Rover

    Titan has a thick atmosphere, it’s even thicker than Earth’s. But it only has one-seventh the gravity of Earth. Because of this, winds on Titan tend to be a lot gentler than those on Earth or even Mars. Jackson said:

    “It’s just this enormous, puffy atmosphere. When you’ve got that much air it’s hard to get it churning. So you just don’t usually get big winds on the surface of Titan so far as we know.”

    Since, as far as we know, Titan doesn’t have raging wind storms, smaller dust devils might be a good way to transport the hydrocarbon particles and create the massive dune fields. In this way, Titan would be similar to Mars, even though there are such large differences in atmospheric density and composition, wind speed and sand composition between the two worlds.

    It will be a while before we can learn more about dust devils on Titan, and whether they even do actually exist. Dragonfly doesn’t launch until 2026, and won’t arrive at Titan until 2034. The Cassini mission, which ended in 2017, was the most recent to visit Saturn and its moons, with no other missions upcoming until Dragonfly.

    If Dragonfly does find dust devils, it will be fascinating to compare them to the ones on Earth and Mars. This is especially true since Titan is remarkably similar to Earth in some ways, with its rain, rivers, lakes and seas, albeit composed of liquid methane and ethane instead of water. Combined with the sand dunes, you could almost mistake the landscape seen in images sent back as being on Earth, if it weren’t for the smoggy-looking orange-ish sky. Dust devils would add to that already somewhat eerie – yet oddly reminiscent – alien landscape.

    See the full article here .

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Deborah Byrd created the EarthSky radio series in 1991 and founded EarthSky.org in 1994. Today, she serves as Editor-in-Chief of this website. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in her honor. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. “Being an EarthSky editor is like hosting a big global party for cool nature-lovers,” she says.

  • richardmitnick 8:05 am on April 28, 2020 Permalink | Reply
    Tags: "Are these 19 eccentric asteroids from other star systems?", , , , , EarthSky, The 19 new interstellar asteroids are in highly inclined orbits in contrast to other asteroids comets or planets in our solar system.   

    From EarthSky: “Are these 19 eccentric asteroids from other star systems?” 


    From EarthSky

    April 28, 2020
    Paul Scott Anderson

    Illustration depicting one of the Centaur asteroids, which the researchers think originated from interstellar space. It was orbiting the sun in an orbit highly perpendicular to the protoplanetary disk of dust and gas, and still maintains that orbit today. Image via NASA/ CNRS.


    You likely heard about ‘Oumuamua, the strange asteroid-like object that entered our solar system from interstellar space in 2017. More recently, astronomers found a second interstellar object – definitely a comet this time, labeled 21/Borisov – in 2019. Both of those objects were only visitors to our solar system, passing through for a time before heading back out into interstellar space. Meanwhile, in 2018, the asteroid 2015 BZ509 was also identified as being of interstellar origin. But this asteroid isn’t just passing through. It’s a permanent member of our solar system, orbiting the sun. Now, researchers from the French National Centre for Scientific Research (CNRS) say they’ve found the first known population of 19 interstellar asteroids, now-permanent members of our solar system that apparently originated from somewhere else in space.

    Like 2015 BZ509, they are permanent residents of the solar system, belonging to a group of objects called Centaurs, small rocky bodies orbiting between the Trojan asteroids near Jupiter and the Kuiper Belt objects beyond Neptune.

    The 19 new interstellar asteroids are in highly inclined orbits in contrast to other asteroids, comets or planets in our solar system.

    The Centaurs (red dots) are small rocky objects generally between the Kuiper Belt beyond Neptune (N) and the Trojans near Jupiter (J). Image via WilyD/ Wikipedia.

    The new peer-reviewed findings were published in the journal Monthly Notices of the Royal Astronomical Society (MNRAS) on April 23, 2020. The study was conducted by lead author Fathi Namouni, a CNRS researcher in the Laboratoire Lagrange and Helena Morais, researcher at UNESP in Brazil.

    While these asteroids have been orbiting the sun for a long time, they did not originate here, according to the new research. Analysis indicates that they were not part of the original protoplanetary disk of dust and gas that surrounded our sun when it was first born 4.5 billion years ago, where the young planets were forming, so they must have come here from somewhere else. Namouni said in a statement:

    “The close proximity of the stars meant that they felt each others’ gravity much more strongly in those early days than they do today. This enabled asteroids to be pulled from one star system to another.”

    2015 BZ509, discovered in 2018, was the first permanent asteroid in the solar system (unlike ‘Oumuamua or 21/Borisov) determined to have originated from interstellar space. Image via Christian Veillet/ Large Binocular Telescope Observatory/ CNRS.

    U Arizona Large Binocular Telescope, Interferometer, or LBTI, is a ground-based instrument connecting two 8-meter class telescopes on Mount Graham, Arizona, USA, Altitude 3,221 m (10,568 ft.) to form the largest single-mount telescope in the world. The interferometer is designed to detect and study stars and planets outside our solar system. Image credit: NASA/JPL-Caltech.

    So how did Namouni and Morais determine the interstellar origin of these asteroids?

    They developed a precise computer simulation of the orbits of these asteroids. By doing so, they could “go back in time” to find out what the positions of the asteroids were in the distant past. The simulations showed that, like now, the asteroids were eccentric, orbiting the sun highly perpendicular to the orbits of the young planets and other objects at the time. They were also located far away from the protoplanetary disk itself. These two findings indicate that the asteroids did not form in the protoplanetary disk along with all the other objects in our solar system, but rather they must have originated from somewhere else, perhaps another star, and were caught by the sun’s gravity early in the solar system’s history.

    Morais commented:

    “The discovery of a whole population of asteroids of interstellar origin is an important step in understanding the physical and chemical similarities and differences between solar system-born and interstellar asteroids. This population will give us clues about the sun’s early birth cluster, how interstellar asteroid capture occurred, and the role that interstellar matter had in chemically enriching the solar system and shaping its evolution.”

    These asteroids are similar to 2015 BZ509, which shares an orbit with Jupiter, but is traveling in the opposite direction. In 2018, the same researchers, Namouni and Morais, found that the asteroid has always had that retrograde orbit, going back to the birth of the solar system. This suggested it came from a nearby star system, and was captured by Jupiter’s gravity. 2015 BZ509 was first spotted in the Pan-STARRS survey in 2015.

    Pann-STARS 1 Telescope, U Hawaii, situated at Haleakala Observatories near the summit of Haleakala , on the island of Maui in Hawaii, USA, Pann-STARS 1 Telescope, U Hawaii, situated at Haleakala Observatories near the summit of Haleakala in Hawaii, USA, altitude 3,052 m (10,013 ft)

    It’s still possible that there could be another explanation for asteroids like these, but as they explained in a recent Gizmodo article on April 23, 2020, Namouni and Morais seem confident in their conclusions. They’ve faced some skepticism from other scientists, but so far no peer-reviewed papers have been published refuting their results. Only time will tell if their results continue to stand up to scrutiny, but at the moment, it seems that they have established a good case for some Centaurs (and perhaps some other similar objects in the solar system?) having an extraterrestrial origin.

    Objects like ‘Oumuamua and 21/Borisov were more difficult to study, since they were only in our solar system for a relatively short amount of time. But these other 19 asteroids, although far away from Earth, keep orbiting the sun, making it easier to observe them remotely over long time periods. If they truly are interstellar, then they offer a unique opportunity to examine asteroids that are alien to our solar system, and compare them to asteroids that were already here when the solar system began to form. Additional analysis could show how they differ in appearance or composition to asteroids that formed here, and provide valuable clues as to how asteroids and other rocky bodies form around other stars.

    See the full article here .

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Deborah Byrd created the EarthSky radio series in 1991 and founded EarthSky.org in 1994. Today, she serves as Editor-in-Chief of this website. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in her honor. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. “Being an EarthSky editor is like hosting a big global party for cool nature-lovers,” she says.

  • richardmitnick 10:40 am on April 21, 2020 Permalink | Reply
    Tags: , , , , EarthSky, Microlensing,   

    From EarthSky: “How WFIRST will use warped spacetime to find exoplanets” 


    From EarthSky

    April 19, 2020
    Paul Scott Anderson

    NASA’s WFIRST mission – an infrared space observatory planned for launch around 2025 – will use the fact that the gravity of distant objects warps spacetime, bending and focusing light, thereby revealing new worlds.


    Artist’s concept of how WFIRST will use microlensing – the bending and focusing of starlight via the gravity of distant objects – to search for exoplanets. WFIRST will focus on the region near the center of our Milky Way galaxy, where stars are most densely packed. Image via NASA/ GSFC/ CI Lab/ JPL.

    Most exoplanets orbiting distant stars are found by observing a planet transit, or pass in front of, its star.

    Planet transit. NASA/Ames.

    As the planet transits, the star’s light temporarily and minutely dims. The Wide Field Infrared Survey Telescope (WFIRST), now being developed by NASA for a possible launch in the mid-2020s, will do the opposite. It’ll search for little surges of light that occur during what are called microlensing events, or events where the gravity of distant objects warps spacetime, bending and focusing light, in this case revealing new worlds.

    Gravitational microlensing, S. Liebes, Physical Review B, 133 (1964): 835

    A statement from NASA explained microlensing:

    “Any time two stars align closely from our vantage point, light from the more distant star curves as it travels through the warped space-time of the nearer star. This phenomenon, one of the predictions of Einstein’s general theory of relativity, was famously confirmed by British physicist Sir Arthur Eddington during a total solar eclipse in 1919. If the alignment is especially close, the nearer star acts like a natural cosmic lens, focusing and intensifying light from the background star.

    Planets orbiting the foreground star may also modify the lensed light, acting as their own tiny lenses. The distortion they create allows astronomers to measure the planet’s mass and distance from its host star. This is how WFIRST will use microlensing to discover new worlds.”

    Pretty cool!

    The new search will combine WFIRST’s results with those of the Kepler and TESS missions.

    NASA/Kepler Telescope, and K2 March 7, 2009 until November 15, 2018

    NASA/MIT TESS replaced Kepler in search for exoplanets

    David Bennett, who leads the gravitational microlensing group at Goddard Space Flight Center in Greenbelt, Maryland, explained that WFIRST’s capabilities as a survey telescope will be key to its potential to find exoplanets:

    “Microlensing signals from small planets are rare and brief, but they’re stronger than the signals from other methods. Since it’s a one-in-a-million event, the key to WFIRST finding low-mass planets is to search hundreds of millions of stars.”

    How microlensing can help find exoplanets. Microlensing depends on the chance alignment of two stars. As one star passes behind the other, the closer star acts like a lens, bending the light so that the brightness smoothly increases and decreases. If there is a planet is around the closer star, its gravity will also bend the light slightly, causing a spike that can be detected and measured by scientists. Image via ESA.

    WFIRST will set its sights on the star-rich center of our Milky Way galaxy. Since WFIRST is an infrared telescope, it can see through dust clouds that block visible light. That’s especially important in planet searches near the galaxy’s center because, when we look in that direction, we see vast clouds of dust in space.

    Other space-based telescopes like the TESS mission and the no-longer-active Kepler mission have looked for exoplanets around stars up to about 1,000 light-years from our sun. WFIRST will look tens of thousands of light-years away, toward the more densely populated central region of our galaxy.

    So far, 86 out of more than 4,000 exoplanets found have been discovered using microlensing. Most exoplanets have been found via the transit method. But the microlensing technique has a very powerful potential: the potential to find solar systems like our own. The NASA statement explained:

    “The techniques commonly used to find other worlds are biased toward planets that tend to be very different from those in our solar system. The transit method, for example, is best at finding sub-Neptune-like planets that have orbits much smaller than Mercury’s. For a solar system like our own, transit studies could miss every planet.

    WFIRST’s microlensing survey will help us find analogs to every planet in our solar system except Mercury, whose small orbit and low mass combine to put it beyond the mission’s reach. WFIRST will find planets that are the mass of Earth and even smaller – perhaps even large moons, like Jupiter’s moon Ganymede.”

    How Gravitational Microlensing Looks to an Observer

    So WFIRST will be able to find other worlds with masses similar to Earth or smaller, in larger orbits. It will also be ideally suited to finding ice giants, similar to Uranus and Neptune, which may be the most common type of planet in our galaxy.

    Using microlensing, WFIRST will search for planets in the habitable zones of their stars, where temperatures could allow liquid water to exist.

    No one detection method can find all planets, but by combining the data from missions like WFIRST, Kepler and TESS, scientists will be able to obtain a much better idea of how many kinds of planetary systems there are. According to Matthew Penny at Louisiana State University:

    “Trying to interpret planet populations today is like trying to interpret a picture with half of it covered. To fully understand how planetary systems form we need to find planets of all masses at all distances. No one technique can do this, but WFIRST’s microlensing survey, combined with the results from Kepler and TESS, will reveal far more of the picture.”

    Comparison of exoplanet discoveries from the Kepler mission and other telescopes with those expected from WFIRST. Red and black dots are large planets with small orbits found by Kepler and others. WFIRST will find planets with a much wider range of masses orbiting farther from their stars (blue dots). Image via NASA/ GSFC (adapted from Penny et al. 2019).

    Kepler’s search area was about 100 square degrees of the sky, containing 100,000 stars typically about 1,000 light-years away. TESS, on the other hand, covers the entire sky and looks at about 200,000 stars, but those stars are much closer, about 100 light-years. By comparison, WFIRST will focus on only three square degrees, but search 200 million stars up to 10,000 light-years distant.

    Of the microlensing searches that have been done to date, most have been in visible light. Those searches wouldn’t be able to find planets around stars near the galaxy’s center that are obscured by dust clouds. Another microlensing survey, by the United Kingdom Infrared Telescope (UKIRT) in Hawaii, has been mapping the central region since 2015.

    UKIRT, located on Mauna Kea, Hawai’i, USA as part of Mauna Kea Observatory,4,207 m (13,802 ft) above sea level

    This will help pave the way for WFIRST’s upcoming observations by measuring the rate of microlensing events near the galaxy’s core.

    UKIRT uses machine learning, which will also be used by WFIRST to help streamline the enormous amount of data. Savannah Jacklin, an astronomer at Vanderbilt University in Nashville, Tennessee, said:

    “Our current survey with UKIRT is laying the groundwork so that WFIRST can implement the first space-based dedicated microlensing survey. Previous exoplanet missions expanded our knowledge of planetary systems, and WFIRST will move us a giant step closer to truly understanding how planets – particularly those within the habitable zones of their host stars – form and evolve.”

    As exciting as finding new worlds near the center of our galaxy is, WFIRST will be able to discover other fascinating objects as well. This includes free-floating planets, as small as Mars, not orbiting any stars, and brown dwarfs, which are too large to be planets but too small to be stars. WFIRST could also find neutron stars and black holes. Penny said:

    “WFIRST’s microlensing survey will not only advance our understanding of planetary systems, it will also enable a whole host of other studies of the variability of 200 million stars, the structure and formation of the inner Milky Way, and the population of black holes and other dark, compact objects that are hard or impossible to study in any other way.”

    WFIRST and its microlensing capabilities represent a huge step forward in the search for new exoplanets and other amazing objects in the central part of our galaxy, a region brimming with new discoveries yet to be made.

    See the full article here .

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Deborah Byrd created the EarthSky radio series in 1991 and founded EarthSky.org in 1994. Today, she serves as Editor-in-Chief of this website. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in her honor. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. “Being an EarthSky editor is like hosting a big global party for cool nature-lovers,” she says.

  • richardmitnick 9:23 am on March 25, 2020 Permalink | Reply
    Tags: "Mizar and Alcor- famous double star" easy to spot in the Big Dipper’s handle., , , , , EarthSky   

    From EarthSky: “Mizar and Alcor, famous double star” 


    From EarthSky

    March 25, 2020
    Bruce McClure

    Mizar and its fainter companion star Alcor are easy to spot in the Big Dipper’s handle.

    Mizar and Alcor. Image via F. Espenak/astropixels.

    Mizar and its fainter companion star Alcor are one of the most famous double stars in the sky. You’ll spot Mizar first, as the middle star of the Big Dipper’s handle. Look closely, and you’ll see Alcor right next to Mizar.

    Mizar and Alcor appear so closely linked in our sky’s dome that they’re often said to be a test of eyesight. But in fact even people with less than perfect eyesight can see the two stars, especially if they’re looking in a dark clear sky. This pair of stars in the Big Dipper’s handle is famously called “the horse and rider.” If you can’t see fainter Alcor with the unaided eye, use binoculars to see Mizar’s nearby companion.

    Located in the handle of the Big Dipper, Mizar (brighter) and Alcor (fainter) are one of the most famous visual double stars in the sky. Image via ESO Online Digitized Sky Survey.

    Mizar is perhaps the Big Dipper’s most famous star, glorified in the annals of astronomy many times over. Apart from Alcor, Mizar in itself became known a double star in 1650. In fact, it was the first double star to be seen through a telescope.

    Few, if any, astronomers back then even dreamed that double stars were anything other than chance alignments of physically unrelated stars. Yet, in 1889, an instrument called a spectroscope revealed that Mizar’s brighter telescopic component consisted of two stars – making Mizar the first binary star ever discovered by spectroscopic means.

    At a later date, Mizar’s dimmer telescopic component also showed itself to be a spectroscopic binary, meaning that Mizar consists of two sets of binaries – making it a quadruple star.

    As for Alcor, it was long believed that Mizar and Alcor were not gravitationally bound and did not form a true binary star system. In 2009, though, two groups of astronomers independently reported that Alcor actually is itself a binary, consisting of Alcor A and Alcor B. Astronomers now believe that the Alcor binary system is gravitationally bound to the Mizar quadruple system – making six stars in all, where we see only two with the eye.

    Thus Mizar and Alcor not only test eyesight, but the limits of our technological vision as well.

    Bottom line: Famous double stars Mizar and Alcor are easy to find in the handle of the Big Dipper. Mizar is really four stars, and Alcor is really two stars. So what we see as two stars are really six in one!

    See the full article here .

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Deborah Byrd created the EarthSky radio series in 1991 and founded EarthSky.org in 1994. Today, she serves as Editor-in-Chief of this website. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in her honor. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. “Being an EarthSky editor is like hosting a big global party for cool nature-lovers,” she says.

  • richardmitnick 9:17 am on March 5, 2020 Permalink | Reply
    Tags: , , , , EarthSky,   

    From EarthSky: “What is a globular cluster?” 


    From EarthSky

    March 5, 2020
    Andy Briggs

    Globular clusters are spherical collections of up to perhaps a million stars, orbiting mostly in the star halo of spiral galaxies, containing some of a galaxy’s oldest stars.

    The globular cluster Messier 5, as seen by the Hubble Space Telescope. This photo was an Astronomy Picture of the Day in June 2015. Via HST/ NASA/ ESA/ APOD.

    NASA/ESA Hubble Telescope

    Globular clusters are tightly packed, symmetrical collections of up to about a million stars, orbiting mostly in the star halos surrounding most spiral galaxies. Globular clusters contain some of the oldest stars in a galaxy and are thought to have formed early in its history. Could it be that – when it was first forming – a spiral galaxy like our Milky Way was once an amorphous cloud of gas and dust? Could its first stars have collected into globular clusters? Could these clusters have stayed put in the halo around a galaxy’s center, as the rest of the galaxy flattened out and formed spiral arms? That scenario would explain why globular clusters orbit in a galaxy’s halo and contain a its oldest stars.

    But the fact is that no one knows precisely how globular clusters formed, and what role, if any, they played in the development of galaxies. We do know that globular clusters are the oldest, largest and most massive type of star cluster and that they contain the oldest stars. Their age can be demonstrated by their almost complete lack of gas and dust, all of which has presumably been incorporated into stars.

    Globular clusters are big. They can reach 300 light-years in diameter. Unlike the open star clusters – containing a few hundred young, sibling stars, scattered through the disk of our galaxy and presumably other galaxies – globular clusters are big, symmetric and old, like an earthly city’s oldest and most staid citizens.

    The famous globular cluster Messier 13 or M13 – largest and brightest globular cluster easily visible from the Northern Hemisphere – seen against its star field. At 25,000 light-years away and about 145 light-years in diameter, M13 is a popular target for amateur astronomers using small telescopes. Image via Fred Espenak.

    Our own Milky Way has around 150 globular clusters, with perhaps more awaiting discovery, hidden by galactic dust. Our neighboring spiral galaxy in the direction of the constellation Andromeda – Messier 31 or the Andromeda galaxy – appears to have around 300 globular clusters. Some football-shaped, elliptical galaxies do have globular clusters, too, like Messier 87 in the direction of the constellation Virgo, home to the supermassive black hole that was famously imaged by the Event Horizon Telescope in 2019.

    Messier 87*, The first image of a black hole. This is the supermassive black hole at the center of the galaxy Messier 87. Image via JPL/ Event Horizon Telescope Collaboration.

    EHT map

    This giant elliptical galaxy, M87, has been estimated to possess around 15,000 globular clusters, with more than 1,000 having been directly observed telescopically so far.

    About 150 globular star clusters are known to surround our galaxy’s center.

    Globular clusters orbit galaxies in orbits which are highly eccentric and highly inclined to the galactic plane. Orbiting in the “outskirts” of a galaxy, they take perhaps a few hundred million years to complete a single orbit. In a telescope, a globular cluster looks like a fuzzy ball, with individual stars at the periphery merging into a solid ball of light towards the center. However, this is simply because the stars are so close together that they can’t be resolved individually telescopically. At the center of a globular cluster, stars may reach a density of between 100 and 1,000 stars per cubic parsec. That’s in contrast to the density of stars near our sun, estimated at about 0.14 star per cubic parsec. If you were standing on a planet orbiting a star in a globular cluster, your night sky would be extremely crowded with nearby stars!

    This Hubble Space Telescope image shows the core of the great globular cluster Messier 13, in the constellation Hercules.

    The stars in globular clusters are the galaxy’s most ancient inhabitants, comprising a population of what astronomers call Population II stars. Those whose age has been measured are between 11 and 13 billion years old, making them almost as old as the galaxy itself. Not surprisingly, many of these ancient stars have evolved into huge, bloated red giant stars, as our sun will do in a few billion years. The stars are extremely metal-poor, which is to say – in the peculiar language of astronomy – they have tiny amounts of materials heavier than helium compared to the surrounding interstellar medium (astronomers refer to all elements heavier than helium as “metals”). Because the heavier elements are made inside stars – and then spread throughout the interstellar medium via supernova explosions – this paucity of metals is exactly what would normally be expected from such old stars. In other worlds, Population II stars consist almost exclusively of hydrogen and helium, the materials that were present in the early universe.

    However, there is a mystery: globular clusters also have “abundance anomalies” of heavier metals, meaning there are elements present which are found elsewhere, in stars that formed more recently. In particular, there appears to be excesses of sodium, carbon, oxygen and aluminum, with heavier metals such as strontium, yttrium, barium and europium also being present in some clusters. These anomalies have not been satisfactorily explained, although there have been several explanations put forward, such as the early presence of supermassive stars.

    The most famous globular cluster in the northern hemisphere is Messier 13 in the constellation of Hercules, sometimes referred to as the Great Globular Cluster, which was discovered by Edmond Halley in 1714.


    This image, taken by the Advanced Camera for Surveys on the Hubble Space Telescope, shows the core of the great globular cluster Messier 13 and provides an extraordinarily clear view of the hundreds of thousands of stars in the cluster, one of the brightest and best known in the sky.

    NASA Hubble Advanced Camera for Surveys

    Just 25 000 light-years away and about 145 light-years in diameter, Messier 13 has drawn the eye since its discovery by Edmund Halley, the noted British astronomer, in 1714. The cluster lies in the constellation of Hercules and is so bright that under the right conditions it is even visible to the unaided eye. As Halley wrote: “This is but a little Patch, but it shews it self to the naked Eye, when the Sky is serene and the Moon absent.” Messier 13 was the target of a symbolic Arecibo radio telescope message that was sent in 1974, communicating humanity’s existence to possible extraterrestrial intelligences.

    NAIC Arecibo Observatory operated by University of Central Florida, Yang Enterprises and UMET, Altitude 497 m (1,631 ft).

    However, more recent studies suggest that planets are very rare in the dense environments of globular clusters. This picture was created from images taken with the Wide Field Channel of the Advanced Camera for Surveys on the Hubble Space Telescope. Data through a blue filter (F435W) are coloured blue, data through a red filter (F625W) are coloured green and near-infrared data (through the F814W filter) are coloured red. The exposure times are 1480 s, 380 s and 567 s respectively and the field of view is about 2.5 arcminutes across.

    Charles Messier later added it into his famous catalog in 1764. In amateur telescopes, it is a small fuzzy patch of light, some 22,000 light-years from Earth. At the center of this cluster, stars orbit so closely that occasionally they collide, their deaths leading to the creation of new stars known as “blue stragglers.” This stellar population is the only type of newer stars in globular clusters.

    Other globular clusters of note are M22 in Sagittarius – one of the brightest in the sky – M5 in Serpens and M12 in Ophiuchus. Many of the night sky’s biggest and brightest globular clusters are best viewed on spring nights and often feature in so-called “Messier Marathons.”

    Globular clusters are a wonderful sight in even the smallest telescopes, although a large instrument is needed to resolve individual stars towards their centers.

    When you look at them, you are seeing populations of stars born in our galaxy’s infancy!

    Amateur astronomers enjoy peering at globular clusters through their small telescopes. Here is Omega Centauri, captured by Greg Hogan in Kathleen, Georgia. Thanks, Greg!

    See the full article here .

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Deborah Byrd created the EarthSky radio series in 1991 and founded EarthSky.org in 1994. Today, she serves as Editor-in-Chief of this website. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in her honor. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. “Being an EarthSky editor is like hosting a big global party for cool nature-lovers,” she says.

  • richardmitnick 11:53 am on February 23, 2020 Permalink | Reply
    Tags: , , , , , , , , EarthSky, , ,   

    From EarthSky: “What is dark matter?” 


    From EarthSky

    February 23, 2020
    Andy Briggs

    Dark Matter doesn’t emit light. It can’t be directly observed with any of the existing tools of astronomers. Yet astrophysicists believe it and Dark Energy make up most of the mass of the cosmos. What dark matter is, and what it isn’t. here.

    Since the 1930s, astrophysicists have been trying to explain why the visible material in galaxies can’t account for how galaxies are shaped, or how they behave. They believe a form of dark or invisible matter pervades our universe, but they still don’t know what this dark matter might be. Image via ScienceAlert.

    Dark matter is a mysterious substance thought to compose perhaps about 27% of the makeup of the universe. What is it? It’s a bit easier to say what it isn’t.

    It isn’t ordinary atoms – the building blocks of our own bodies and all we see around us – because atoms make up only somewhere around 5% of the universe, according to a cosmological model called the Lambda Cold Dark Matter Model (aka the Lambda-CDM model, or sometimes just the Standard Model).

    Lamda Cold Dark Matter Accerated Expansion of The universe http scinotions.com the-cosmic-inflation-suggests-the-existence-of-parallel-universes
    Alex Mittelmann, Coldcreation

    Dark Matter isn’t the same thing as Dark Energy, which makes up some 68% of the universe, according to the Standard Model.

    Dark Energy Survey

    Dark Energy Camera [DECam], built at FNAL

    NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile, housing DECam at an altitude of 7200 feet

    Timeline of the Inflationary Universe WMAP

    The Dark Energy Survey (DES) is an international, collaborative effort to map hundreds of millions of galaxies, detect thousands of supernovae, and find patterns of cosmic structure that will reveal the nature of the mysterious dark energy that is accelerating the expansion of our Universe. DES began searching the Southern skies on August 31, 2013.

    According to Einstein’s theory of General Relativity, gravity should lead to a slowing of the cosmic expansion. Yet, in 1998, two teams of astronomers studying distant supernovae made the remarkable discovery that the expansion of the universe is speeding up. To explain cosmic acceleration, cosmologists are faced with two possibilities: either 70% of the universe exists in an exotic form, now called dark energy, that exhibits a gravitational force opposite to the attractive gravity of ordinary matter, or General Relativity must be replaced by a new theory of gravity on cosmic scales.

    DES is designed to probe the origin of the accelerating universe and help uncover the nature of dark energy by measuring the 14-billion-year history of cosmic expansion with high precision. More than 400 scientists from over 25 institutions in the United States, Spain, the United Kingdom, Brazil, Germany, Switzerland, and Australia are working on the project. The collaboration built and is using an extremely sensitive 570-Megapixel digital camera, DECam, mounted on the Blanco 4-meter telescope at Cerro Tololo Inter-American Observatory, high in the Chilean Andes, to carry out the project.

    Over six years (2013-2019), the DES collaboration used 758 nights of observation to carry out a deep, wide-area survey to record information from 300 million galaxies that are billions of light-years from Earth. The survey imaged 5000 square degrees of the southern sky in five optical filters to obtain detailed information about each galaxy. A fraction of the survey time is used to observe smaller patches of sky roughly once a week to discover and study thousands of supernovae and other astrophysical transients.

    Dark matter is invisible; it doesn’t emit, reflect or absorb light or any type of electromagnetic radiation such as X-rays or radio waves. Thus, dark matter is undetectable directly, as all of our observations of the universe, apart from the detection of gravitational waves, involve capturing electromagnetic radiation in our telescopes.

    Gravitational waves Werner Benger-ZIB-AEI-CCT-LSU

    Yet dark matter does interact with ordinary matter. It exhibits measurable gravitational effects on large structures in the universe such as galaxies and galaxy clusters. Because of this, astronomers are able to make maps of the distribution of dark matter in the universe, even though they cannot see it directly.

    They do this by measuring the effect dark matter has on ordinary matter, through gravity.

    This all-sky image – released in 2013 – shows the distribution of dark matter across the entire history of the universe as seen projected on the sky. It’s based on data collected with the European Space Agency’s Planck satellite.

    ESA/Planck 2009 to 2013

    Dark blue areas represent regions that are denser than their surroundings. Bright areas represent less dense regions. The gray portions of the image correspond to patches of the sky where foreground emission, mainly from the Milky Way but also from nearby galaxies, prevents cosmologists from seeing clearly. Image via ESA.

    There is currently a huge international effort to identify the nature of dark matter. Bringing an armory of advanced technology to bear on the problem, astronomers have designed ever-more complex and sensitive detectors to tease out the identity of this mysterious substance.

    Dark Matter Research

    Universe map Sloan Digital Sky Survey (SDSS) 2dF Galaxy Redshift Survey

    Scientists studying the cosmic microwave background hope to learn about more than just how the universe grew—it could also offer insight into dark matter, dark energy and the mass of the neutrino.

    Dark matter cosmic web and the large-scale structure it forms The Millenium Simulation, V. Springel et al

    Dark Matter Particle Explorer China

    DEAP Dark Matter detector, The DEAP-3600, suspended in the SNOLAB deep in Sudbury’s Creighton Mine

    LBNL LZ Dark Matter project at SURF, Lead, SD, USA

    Inside the ADMX experiment hall at the University of Washington Credit Mark Stone U. of Washington. Axion Dark Matter Experiment

    Dark matter might consist of an as yet unidentified subatomic particle of a type completely different from what scientists call baryonic matter – that’s just ordinary matter, the stuff we see all around us – which is made of ordinary atoms built of protons and neutrons.

    The list of candidate subatomic particles breaks down into a few groups: there are the WIMPs (Weakly Interacting Massive Particles), a class of particles thought to have been produced in the early universe. Astronomers believe that WIMPs might self-annihilate when colliding with each other, so they have searched the skies for telltale traces of events such as the release of neutrinos or gamma rays. So far, they’ve found nothing. In addition, although a theory called supersymmetry predicts the existence of particles with the same properties as WIMPs, repeated searches to find the particles directly have also found nothing, and experiments at the Large Hadron Collider to detect the expected presence of supersymmetry have completely failed to find it.

    Standard Model of Supersymmetry via DESY

    CERN/LHC Map

    CERN LHC Maximilien Brice and Julien Marius Ordan

    SixTRack CERN LHC particles

    Several different types of detector have been used to detect WIMPs. The general idea is that very occasionally, a WIMP might collide with an ordinary atom and release a faint flash of light, which can be detected. The most sensitive detector built to date is XENON1T, which consists of a 10-meter cylinder containing 3.2 tons of liquid xenon, surrounded by photomultipliers to detect and amplify the incredibly faint flashes from these rare interactions. As of July 2019, when the detector was decommissioned to pave the way for a more sensitive instrument, the XENONnT, no collisions between WIMPs and the xenon atoms had been seen.

    XENON1T at Gran Sasso LABORATORI NAZIONALI del GRAN SASSO, located in the Abruzzo region of central Italy

    Gran Sasso LABORATORI NAZIONALI del GRAN SASSO, located in the Abruzzo region of central Italy

    At the moment, a hypothetical particle called the Axion is receiving much attention.

    CERN CAST Axion Solar Telescope

    As well as being a strong candidate for dark matter, the existence of axions is also thought to provide the answers to a few other persistent questions in physics such as the Strong CP Problem.

    Fritz Zwicky discovered Dark Matter in the 1930s when observing the movement of the Coma Cluster., Vera Rubin a Woman in STEM denied the Nobel, did most of the work on Dark Matter.

    Fritz Zwicky from http:// palomarskies.blogspot.com

    Coma cluster via NASA/ESA Hubble

    In modern times, it was astronomer Fritz Zwicky, in the 1930s, who made the first observations of what we now call dark matter. His 1933 observations of the Coma Cluster of galaxies seemed to indicated it has a mass 500 times more than that previously calculated by Edwin Hubble. Furthermore, this extra mass seemed to be completely invisible. Although Zwicky’s observations were initially met with much skepticism, they were later confirmed by other groups of astronomers.

    Thirty years later, astronomer Vera Rubin provided a huge piece of evidence for the existence of dark matter. She discovered that the centers of galaxies rotate at the same speed as their extremities, whereas, of course, they should rotate faster. Think of a vinyl LP on a record deck: its center rotates faster than its edge. That’s what logic dictates we should see in galaxies too. But we do not. The only way to explain this is if the whole galaxy is only the center of some much larger structure, as if it is only the label on the LP so to speak, causing the galaxy to have a consistent rotation speed from center to edge.

    Vera Rubin, following Zwicky, postulated that the missing structure in galaxies is dark matter. Her ideas were met with much resistance from the astronomical community, but her observations have been confirmed and are seen today as pivotal proof of the existence of dark matter.

    Astronomer Vera Rubin at the Lowell Observatory in 1965, worked on Dark Matter (The Carnegie Institution for Science)

    Vera Rubin measuring spectra, worked on Dark Matter (Emilio Segre Visual Archives AIP SPL)

    Vera Rubin, with Department of Terrestrial Magnetism (DTM) image tube spectrograph attached to the Kitt Peak 84-inch telescope, 1970. https://home.dtm.ciw.edu

    The Vera C. Rubin Observatory currently under construction on the El Peñón peak at Cerro Pachón Chile, a 2,682-meter-high mountain in Coquimbo Region, in northern Chile, alongside the existing Gemini South and Southern Astrophysical Research Telescopes.

    LSST Data Journey, Illustration by Sandbox Studio, Chicago with Ana Kova

    Some astronomers have tried to negate the need the existence of dark matter altogether by postulating something called Modified Newtonian dynamics (MOND).

    Mordehai Milgrom, MOND theorist, is an Israeli physicist and professor in the department of Condensed Matter Physics at the Weizmann Institute in Rehovot, Israel http://cosmos.nautil.us

    MOND Modified Newtonian Dynamics a Humble Introduction Marcus Nielbock

    The idea behind this is that gravity behaves differently over long distances to what it does locally, and this difference of behavior explains phenomena such as galaxy rotation curves which we attribute to dark matter. Although MOND has its supporters, while it can account for the rotation curve of an individual galaxy, current versions of MOND simply cannot account for the behavior and movement of matter in large structures such as galaxy clusters and, in its current form, is thought unable to completely account for the existence of dark matter. That is to say, gravity does behave in the same way at all scales of distance. Most versions of MOND, on the other hand, have two versions of gravity, the weaker one occurring in regions of low mass concentration such as in the outskirts of galaxies. However, it is not inconceivable that some new version of MOND in the future might yet account for dark matter.

    Although some astronomers believe we will establish the nature of dark matter in the near future, the search so far has proved fruitless, and we know that the universe often springs surprises on us so that nothing can be taken for granted.

    The approach astronomers are taking is to eliminate those particles which cannot be dark matter, in the hope we will be left with the one which is.

    It remains to be seen if this approach is the correct one.

    See the full article here .

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Deborah Byrd created the EarthSky radio series in 1991 and founded EarthSky.org in 1994. Today, she serves as Editor-in-Chief of this website. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in her honor. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. “Being an EarthSky editor is like hosting a big global party for cool nature-lovers,” she says.

  • richardmitnick 3:34 pm on February 12, 2020 Permalink | Reply
    Tags: "What is a neutron star?", , , , , , EarthSky,   

    From EarthSky: “What is a neutron star?” And Dame Susan Jocelyn Bell Burnell Who Discovered Pulsars 


    From EarthSky

    February 12, 2020
    Andy Briggs

    Artist’s concept of a neutron star. The star’s tiny size and extreme density give it incredibly powerful gravity at its surface. Thus this image portrays the space around the neutron star as being curved. Image via Raphael.concorde/ Daniel Molybdenum/ NASA/ Wikimedia Commons.

    When – at the end of its life – a massive star explodes as a supernova, its core can collapse to end up as a tiny and superdense object with not much more than our sun’s mass. These small, incredibly dense cores of exploded stars are neutron stars. They’re among the most bizarre objects in the universe.

    A typical neutron star has about about 1.4 times our sun’s mass, but they range up to about two solar masses. Now consider that our sun has about 100 times Earth’s diameter. In a neutron star, all its large mass – up to about twice as much as our sun’s – is squeezed into a star that’s only about 10 miles (15 km) across, or about the size of an earthly city.

    So perhaps you can see that neutron stars are very, very dense! A tablespoon of neutron star material would weigh more than 1 billion U.S. tons (900 billion kg). That’s more than the weight of Mount Everest, Earth’s highest mountain.

    Neutron stars are the collapsed cores of massive stars. They pack roughly the mass of our sun into a sphere with the diameter of a city. Here’s a comparison of a neutron star’s typical diameter with the city of Chicago. Graphic via M. Coleman Miller.

    Here’s how neutron stars form. Throughout much of their lives, stars maintain a delicate balancing act. Gravity tries to compress the star while the star’s internal pressure exerts an outward push. The outward pressure is caused by nuclear fusion at the star’s core. This fusion “burning” is the process by which stars shine.

    In a supernova explosion, gravity suddenly and catastrophically gets the upper hand in the war it has been waging with the star’s internal pressure for millions or billions of years. With its nuclear fuel exhausted and the outward pressure removed, gravity suddenly compresses the star inward. A shock wave travels to the core and rebounds, blowing the star apart. This whole process takes perhaps a couple of seconds.

    But gravity’s victory is not yet complete. With most of the star blown into space, the core remains, which may only possess a couple of times the mass of our sun. Gravity continues to compress it, to a point where the atoms become so compacted and so close together that electrons are violently thrust into their parent nuclei, combining with the protons to form neutrons.

    Thus the neutron star gets its name from its composition. What gravity has created is a superdense, neutron-rich material – called neutronium – in a city-sized sphere.

    Ask a Spaceman: Neutron star weirdness

    What neutron stars are, and are not. If, after the supernova, the core of the star has enough mass, then – according to current understanding – the gravitational collapse will continue. A black hole will form instead of a neutron star. In terms of mass, the dividing line between neutron stars and black holes is the subject of much debate. Astrophysicists refer to a kind of “missing mass,” occurring between about two solar masses (the theoretical maximum mass of a neutron star) and five solar masses (the theoretical minimum mass of a black hole). Some expect that this mass bracket will eventually be found to be populated by ultra-lightweight black holes, but until now none have been found.

    The exact internal structure of a neutron star is also the subject of much debate. Current thinking is that the star possesses a thin crust of iron, perhaps a mile or so thick. Under that, the composition is largely neutrons, taking various forms the further down in the neutron star they are.

    A neutron star does not generate any light or heat of its own after its formation. Over millions of years its latent heat will gradually cool from an intial 600,000 degrees Kelvin (1 million degrees Fahrenheit), eventually ending its life as the cold, dead remnant of a once-glorious star.

    Because neutron stars are so dense, they have intense gravitational and magnetic fields. The gravity of a neutron star is about a thousand billion times stronger than that of the Earth. Thus the surface of a neutron star is exceedingly smooth; gravity does not permit anything tall to exist. Neutron stars are thought to have “mountains,” but they are only inches tall.

    Pulsars: How we know about neutron stars. Although neutron stars were long predicted in astrophysical theory, it wasn’t until 1967 that the first was discovered, as a pulsar, by Dame Susan Jocelyn Bell Burnell. Since then, hundreds more have been discovered, including the famous pulsar at the heart of the Crab Nebula, a supernova remnant seen to explode by the Chinese in 1054.

    Supernova remnant Crab nebula. NASA/ESA Hubble

    X-ray picture of Crab pulsar, taken by NASA/Chandra

    On a neutron star, intense magnetic fields focus radio waves into two beams firing into space from its magnetic poles, much like the beam of a lighthouse. If the object is oriented just so with respect to Earth – so that these beams become visible from our earthly viewpoint – we see flashes of radio light at regular and extremely precise intervals. Neutron stars are, in fact, the celestial timekeepers of the cosmos, their accuracy rivalling that of atomic clocks.

    Anatomy of a pulsar. They are neutron stars that are oriented in a particular way with respect to Earth, so that we see them “pulse” at regular intervals. Image via Roen Kelly/ Discovermagazine.com.

    Read more about Dame Susan Jocelyn Bell Burnell, who discovered pulsars

    Women in STEM – Dame Susan Jocelyn Bell Burnell

    Dame Susan Jocelyn Bell Burnell, discovered pulsars with radio astronomy. Jocelyn Bell at the Mullard Radio Astronomy Observatory, Cambridge University, taken for the Daily Herald newspaper in 1968. Denied the Nobel.

    Dame Susan Jocelyn Bell Burnell at work on first plusar chart 1967 pictured working at the Four Acre Array in 1967. Image courtesy of Mullard Radio Astronomy Observatory.

    Dame Susan Jocelyn Bell Burnell 2009

    Dame Susan Jocelyn Bell Burnell (1943 – ), still working from http://www. famousirishscientists.weebly.com


    British astrophysicist, scholar and trailblazer Jocelyn Bell Burnell discovered the space-based phenomena known as pulsars, going on to establish herself as an esteemed leader in her field.Who Is Jocelyn Bell Burnell?
    Jocelyn Bell Burnell is a British astrophysicist and astronomer. As a research assistant, she helped build a large radio telescope and discovered pulsars, providing the first direct evidence for the existence of rapidly spinning neutron stars. In addition to her affiliation with Open University, she has served as dean of science at the University of Bath and president of the Royal Astronomical Society. Bell Burnell has also earned countless awards and honors during her distinguished academic career.

    Early Life

    Jocelyn Bell Burnell was born Susan Jocelyn Bell on July 15, 1943, in Belfast, Northern Ireland. Her parents were educated Quakers who encouraged their daughter’s early interest in science with books and trips to a nearby observatory. Despite her appetite for learning, however, Bell Burnell had difficulty in grade school and failed an exam intended to measure her readiness for higher education.

    Undeterred, her parents sent her to England to study at a Quaker boarding school, where she quickly distinguished herself in her science classes. Having proven her aptitude for higher learning, Bell Burnell attended the University of Glasgow, where she earned a bachelor’s degree in physics in 1965.

    Little Green Men

    In 1965, Bell Burnell began her graduate studies in radio astronomy at Cambridge University. One of several research assistants and students working under astronomers Anthony Hewish, her thesis advisor, and Martin Ryle, over the next two years she helped construct a massive radio telescope designed to monitor quasars. By 1967, it was operational and Bell Burnell was tasked with analyzing the data it produced. After spending endless hours pouring over the charts, she noticed some anomalies that did not fit with the patterns produced by quasars and called them to Hewish’s attention.

    Over the ensuing months, the team systematically eliminated all possible sources of the radio pulses—which they affectionately labeled Little Green Men, in reference to their potentially artificial origins—until they were able to deduce that they were made by neutron stars, fast-spinning collapsed stars too small to form black holes.

    Pulsars and Nobel Prize Controversy

    Their findings were published in the February 1968 issue of Nature and caused an immediate sensation. Intrigued as much by the novelty of a woman scientist as by the astronomical significance of the team’s discovery, which was labeled pulsars—for pulsating radio stars—the press picked up the story and showered Bell Burnell with attention. That same year, she earned her Ph.D. in radio astronomy from Cambridge University.

    However, in 1974, only Hewish and Ryle received the Nobel Prize for Physics for their work. Many in the scientific community raised their objections, believing that Bell Burnell had been unfairly snubbed. However, Bell Burnell humbly rejected the notion, feeling that the prize had been properly awarded given her status as a graduate student, though she has also acknowledged that gender discrimination may have been a contributing factor.

    Life on the Electromagnetic Spectrum

    Nobel Prize or not, Bell Burnell’s depth of knowledge regarding radio astronomy and the electromagnetic spectrum has earned her a lifetime of respect in the scientific community and an esteemed career in academia. After receiving her doctorate from Cambridge, she taught and studied gamma ray astronomy at the University of Southampton. Bell Burnell then spent eight years as a professor at University College London, where she focused on x-ray astronomy.

    During this same time, she began her affiliation with Open University, where she would later work as a professor of physics while studying neurons and binary stars, and also conducted research in infrared astronomy at the Royal Observatory, Edinburgh. She was the Dean of Science at the University of Bath from 2001 to 2004, and has been a visiting professor at such esteemed institutions as Princeton University and Oxford University.

    Array of Honors and Achievements

    In recognition of her achievements, Bell Burnell has received countless awards and honors, including Commander and Dame of the Order of the British Empire in 1999 and 2007, respectively; an Oppenheimer prize in 1978; and the 1989 Herschel Medal from the Royal Astronomical Society, for which she would serve as president from 2002 to 2004. She was president of the Institute of Physics from 2008 to 2010, and has served as president of the Royal Society of Edinburgh since 2014. Bell Burnell also has honorary degrees from an array of universities too numerous to mention.

    Personal Life

    In 1968, Jocelyn married Martin Burnell, from whom she took her surname, with the two eventually divorcing in 1993. The two have a son, Gavin, who has also become a physicist.

    A documentary on Bell Burnell’s life, Northern Star, aired on the BBC in 2007.

    See the full article here .

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Deborah Byrd created the EarthSky radio series in 1991 and founded EarthSky.org in 1994. Today, she serves as Editor-in-Chief of this website. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in her honor. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. “Being an EarthSky editor is like hosting a big global party for cool nature-lovers,” she says.

  • richardmitnick 12:25 pm on February 11, 2020 Permalink | Reply
    Tags: , , , , EarthSky, Galaxy cluster named XLSSC 122, University of Victoria   

    From University of Victoria via EarthSky: “New clues in the search for the universe’s oldest galaxies” 


    From University of Victoria




    February 11, 2020
    Jon Willis, University of Victoria

    An astronomer reports on a very old galaxy cluster – labeled XLSSC 122 – whose light has taken 10.4 billion years to travel across the universe to us.

    A composite image of the galaxy cluster XLSSC 122 using images from the Hubble Space Telescope and European Southern Observatory’s Very Large Telescope. The white contours reveal strong X-ray emission captured by the European Space Agency’s X-ray Multi-Mirror satellite. Image via Jon Willis.

    A galaxy cluster can be likened to a great city of galaxies, a galactic conurbation where each galaxy represents an individual, twinkling structure. Just as an archaeologist might seek evidence of the oldest cities on Earth, astronomers have long sought to discover the oldest galaxy clusters in the universe – each the cosmic equivalent of an ancient civilization like Jericho or Ur.

    I have been fortunate to lead a team of astronomers in discovering just such an example of an old galaxy cluster [Nature]. How old? The light from the galaxy cluster, named XLSSC 122 has taken 10.4 billion years to travel across the universe to us.

    A youthful universe

    Astronomers believe that the universe itself is 13.7 billion years old [The Astrophysical Journal], so a little maths tells us that we are observing XLSSC 122 when the universe was a mere 3.3 billion years old. Imagine our surprise then, when each new view of this galaxy cluster revealed a physical structure seemingly every bit as mature and developed as galaxy clusters in our present-day universe – a situation rather like looking at a photo from your youth in which you appear much older than you were.

    XLSSC 122 is a remarkably precocious presence in a youthful universe, a clue perhaps that the universe – at least the densest parts of it – can form stars, accumulate into galaxies and eventually be drawn into galaxy clusters with surprising rapidity. Given that computer simulations of the assembly of galaxy clusters indicate more gradual growth, the discovery of XLSSC 122 suggests that our current ideas of how structure forms in the universe may be incomplete.

    Discovering galaxy clusters

    When I first saw it, XLSSC 122 appeared as an unassuming collection of photons on an X-ray image of the sky [MNRAS] taken by the European Space Agency’s X-ray Multi-Mirror space observatory.

    ESA/XMM Newton

    Though viewed at great distance, we knew we were potentially observing a hot halo of gas – at 10 million Kelvin (9.9 million Celsius or 18 million Fahrenheit) – confined within the gravitational field of a massive cluster of galaxies.

    However, visible light images taken with the Canada-France-Hawaii Telescope revealed no galaxies associated with the X-ray source. This was an interesting clue that we may have discovered a distant galaxy cluster where the expansion of the universe had shifted the visible light emitted by the cluster galaxies into the infrared.

    CFHT Telescope, Maunakea, Hawaii, USA, at Maunakea, Hawaii, USA,4,207 m (13,802 ft) above sea level

    From this realization, we proceeded to obtain an image of our candidate cluster using the European Southern Observatory’s Very Large Telescope.

    ESO VLT at Cerro Paranal in the Atacama Desert, •ANTU (UT1; The Sun ),
    •KUEYEN (UT2; The Moon ),
    •MELIPAL (UT3; The Southern Cross ), and
    •YEPUN (UT4; Venus – as evening star).
    elevation 2,635 m (8,645 ft) from above Credit J.L. Dauvergne & G. Hüdepohl atacama photo,

    This image, taken with an infrared camera, revealed the telltale presence of faint red objects – distant galaxies; but exactly how distant remained a mystery.

    Hubble Space Telescope brings ultimate clarity

    NASA/ESA Hubble Telescope

    Having compiled a strong case that XLSSC 122 was a distant galaxy cluster, perhaps the most distant, we were awarded observing time with the Hubble Space Telescope. Given that only one out of every 10 Hubble proposals is successful, this represented an achievement in itself.

    Although the Hubble telescope is nearly 30 years old, it remains a preeminent astronomical facility. Our images of XLSSC 122 appeared sharp and clear compared to the fuzzy images obtained from ground-based observatories. Although I have been a professional astronomer for 20 years, seeing the Hubble images of our cluster represented a near-unique discovery moment. It was immediately clear from the galaxy colors and spectra that XLSSC 122 was supremely distant: it lay at a redshift of two, meaning that the light from XLSSC 122 had taken 10.4 billion years to reach Earth.

    See the full article here .

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Deborah Byrd created the EarthSky radio series in 1991 and founded EarthSky.org in 1994. Today, she serves as Editor-in-Chief of this website. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in her honor. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. “Being an EarthSky editor is like hosting a big global party for cool nature-lovers,” she says.

  • richardmitnick 2:24 pm on February 1, 2020 Permalink | Reply
    Tags: , , , Centauri star system, , EarthSky, National Institute of Astrophysics, Possible Proxima Centauri C, Proxima Centauri b   

    From National Institute of Astrophysics via EarthSky: “Is there a 2nd planet orbiting Proxima Centauri?” 

    From National Institute of Astrophysics




    January 27, 2020
    Paul Scott Anderson

    Proxima Centauri, the closest star to our sun, may have a second planet, according to researchers from the National Institute of Astrophysics.

    Centauris Alpha Beta Proxima , 27 February 2012. Skatebiker

    If confirmed, it would be an ideal candidate for direct imaging by new upcoming space telescopes.

    Artist’s concept of Proxima Centauri b, an Earth-sized exoplanet orbiting the nearest star to our sun, Proxima Centauri. Now researchers think there is a second, larger planet also orbiting the star. Image via ESO/ M. Kornmesser/

    In 2016, astronomers announced the discovery of an exoplanet orbiting the closest star to our solar system, Proxima Centauri . Exciting, since the planet appeared to be close to the same size as Earth and not too far away, cosmically-speaking, at 4.2 light-years. Could there be other planets in this nearby system? On January 15, 2020, another research team published its evidence for a second, larger planet orbiting Proxima Centauri. At this point, this second object is still considered a candidate. It is not confirmed. But researchers do make a compelling case for its existence.

    The potential discovery was announced by Mario Damasso of the National Institute of Astrophysics and his colleagues on January 15. The new peer-reviewed paper appeared in Science Advances on the same day.

    The planet – dubbed Proxima Centauri c – is a fair bit larger than the first planet, Proxima Centauri b, and is about six times more massive than Earth. This would make it a super-Earth, planets that are significantly larger and more massive than Earth but smaller and less massive than Neptune. It is estimated to orbit its star every 5.2 years. Proxima Centauri b, by comparison, is only about 1.3 times Earth’s mass.

    Even though Proxima Centauri is the closest star, part of the Alpha Centauri three-star system, it has been difficult to detect planets orbiting it. That’s because most exoplanets discovered so far have been glimpsed via the transit method; that is, they’re detected because they lie edge-on to our line-of-sight to their host stars, and astronomers can detect a minute dip in the host star’s light when the planet crosses in front of it.

    Planet transit. NASA/Ames

    No such dip in brightness has been seen for Proxima Centauri.

    Instead, to find this star’s planets, astronomers have had to use a second planet-hunting technique, called the radial velocity method.

    Radial velocity Image via SuperWasp http:// http://www.superwasp.org/exoplanets.htm

    Radial Velocity Method-Las Cumbres Observatory

    Radial velocity refers to a slight wobble in the star’s motion as seen from Earth, caused by the gravity of unseen planets tugging on it. This is how Proxima Centauri b was found, and now, seemingly, Proxima Centauri c.

    Two European Southern Observatory (ESO) telescope instruments, the High Accuracy Radial velocity Planet Searcher (HARPS) and the Ultraviolet and Visual Echelle Spectrograph (UVES), were used to obtain the data from Proxima Centauri.

    ESO 3.6m telescope & HARPS at Cerro LaSilla, Chile, 600 km north of Santiago de Chile at an altitude of 2400 metres.

    ESO/HARPS at La Silla

    UVES spectrograph mounted on the VLT at the Nasmyth B focus of UT2

    2009 ESO VLTI Interferometer image, Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level, • ANTU (UT1; The Sun ),
    KUEYEN (UT2; The Moon ),
    •MELIPAL (UT3; The Southern Cross ), and
    •YEPUN (UT4; Venus – as evening star).

    Damasso and his team analyzed the star’s light spectrum data, going back 17.5 years, to see if a previously reported light spectrum signal really was from a second planet. If the spectrum oscillates between the red and blue radial velocity, that typically means the star is moving slightly closer to and then farther away from Earth, due to the gravitational pull of a planet or planets. The researchers did find such a signal, occurring over a 1,900-day period. That would mean it is unlikely to be due only to other cyclical shifts in the star’s magnetic field. It would be more consistent with a second planet orbiting the star.


    So, could either of these planets be habitable?

    At this point, we just don’t know enough about them to answer that question. Proxima Centauri b is almost the same size as Earth, and is thought to have similar temperatures, but it orbits very close to its star, which is a red dwarf. Red dwarfs are known for being very active, emitting powerful solar flares. The radiation from those flares could strip away the atmosphere of any close-in planets. Proxima Centauri c is farther out, but may be too cold for life as we know it. It also may be more like Neptune, with a deep gaseous atmosphere and no real solid surface, rather than a super-Earth, which is rocky like Earth, but larger. We just don’t know yet.

    Another exciting aspect of Proxima Centauri c, however, is that it is far enough from the glare of its star that it should be able to be photographed directly by upcoming space telescopes. So far, only a handful of planets that are much larger than this have been successfully photographed, and even then, they are still just blobs of light.

    If scientists can learn more about both Proxima Centauri c and b, including direct imaging for at least c (b would be a lot more difficult), then that should give them a better idea of what both Earth-sized and super-Earth exoplanets are actually like, in particular ones that orbit red dwarf stars. That would then help them figure how many could be potentially habitable, and what conditions would make that possible, an exciting endeavor.

    See the full article here .

    Please help promote STEM in your local schools.

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