Tagged: Sky & Telescope Toggle Comment Threads | Keyboard Shortcuts

  • richardmitnick 9:26 am on October 4, 2019 Permalink | Reply
    Tags: "Best Image Yet of the Cosmic Web", , , , , , Sky & Telescope   

    From RIKEN via Sky & Telescope: “Best Image Yet of the Cosmic Web” 

    RIKEN bloc

    From RIKEN

    via

    SKY&Telescope bloc

    Sky & Telescope

    October 3, 2019
    Monica Young

    Using the light cast by galaxies bursting with new stars, astronomers have mapped out a piece of the cosmic web 12 billion light-years from Earth.

    Gravity has woven the universe into a cosmic web. Primordial gas that filled the young cosmos collapsed into expansive sheets, then into filaments, separated by huge voids. On very large scales, this gas has a texture like soap bubbles or tangled spiderwebs.

    1
    Simulations show that a cosmic web of gaseous filaments, separated by large voids, fills the universe.
    Springel & others / Virgo Consortium

    But even though computer simulations first revealed this large-scale structure decades ago, it’s difficult to picture — literally. We can easily see the light from galaxies and galaxy clusters, but the sparse gas bridging from one cluster to another has largely evaded detection.

    With cutting-edge ground-based instruments, that’s changing. In the October 3rd Science, Hideki Umehata (RIKEN Cluster for Pioneering Research and University of Tokyo) and colleagues report an image of the cosmic web when the universe was only 2 billion years old. Sure, it’s fuzzy, but it’s also the best view we’ve got!

    Lighting Up the Web

    Astronomers know the cosmic web exists because they’ve detected it indirectly. If you look through the cosmic web at a brilliant source in the distance, the source’s light will show a “forest” of hydrogen absorption lines from all the filaments it intercepted along the way.

    But there aren’t that many bright, distant sources out there. And the gas in between galaxies is so spread out it doesn’t emit much light itself.

    Unless, that is, the gas is lit up by galactic flashlights. Galaxies bursting with newborn stars or hosting a gas-guzzling black hole will light up their surroundings, irradiating the sparse hydrogen gas that surrounds them.

    This has been done before — the galaxy UM 287 acts as a cosmic flashlight to light up a 1.5 million light-years-long filament. But now Umehata and colleagues have imaged the same thing on an even bigger scale.

    2
    The blue fuzz to the left of the quasar UM 287 (white dot in center) is a filament of hydrogen gas extending 1.5 million light-years long.
    S. Cantalupo / UCSC

    A Set of Cosmic Flashlights

    Using the Multi Unit Spectroscopic Explorer (MUSE) on the European Southern Observatory’s Very Large Telescope in Chile, Umehata’s team zeroed in on a distant collection of galaxies, collectively known as SSA22, that are 12 billion light-years from Earth (at a redshift of 3.09). The galaxies themselves are brilliant with newborn stars, black hole activity, or both. The light pouring out of these galaxies lights up the gas between the galaxies, boosting its emission.

    3
    Maps of gas filaments. For both panels, identified gas filaments are shown in blue color. The background maps are an optical image taken with the Subaru Telescope (left) and a millimeter-wave image taken with ALMA (right). It is found that there are extensive gaseous structures and cosmic web filaments (left); and that the filaments connect a number of starbursting galaxies (right). (Credit: RIKEN)


    NAOJ/Subaru Telescope at Mauna Kea Hawaii, USA,4,207 m (13,802 ft) above sea level

    3
    Two filaments, each about 3 million light-years long, run vertically through this image, taken by the MUSE instrument on the Very Large Telescope. The white dots are galaxies bursting with new stars, imaged by the Atacama Large Millimeter/submillimeter Array in Chile. (Other galaxies with gas-guzzling black holes at their centers, imaged by NASA’s Chandra X-ray Observatory, are not shown here.) The 24 galaxies associated with this group are embedded in the hydrogen-gas filaments. Hideki Umehata

    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,

    ESO MUSE on the VLT on Yepun (UT4)

    ESO/NRAO/NAOJ ALMA Array in Chile in the Atacama at Chajnantor plateau, at 5,000 metres

    MUSE detected bright patches emitted by hydrogen gas around the galaxies (this is gas that is bound to the galaxies), as well as fainter patches that connect the galaxies. Most of the fainter emission comes from two filaments that run vertically through the image, extending some 3 million light-years. (We’re seeing this length projected onto the two-dimensional plane, so the total extent could be even longer than that.)

    The astronomers calculate that this region of cosmic web contains a trillion Suns’ worth of gas. Moreover, this gas doesn’t stay still. This gas is likely trickling down onto the galaxies, fueling their star formation and black hole activity.

    “The observations from Umehata et al. are just the tip of the iceberg,” says Erika Hamden (University of Arizona), who authored an accompanying opinion piece in Science. “Other similarly bright structures will eventually be identified and observed.”

    Ironically, though, observations of the cosmic web will — for now — remain limited to the distant, early universe. Light at ultraviolet wavelengths will stretch into visible and even infrared wavelengths as it passes through the expanding universe. To observe the cosmic web nearby, we would need access to ultraviolet wavelengths that are blocked by Earth’s atmosphere.

    “Probing the full history of the universe by observing gas emissions requires a probe-class UV satellite,” Hamden adds. “It requires getting a large UV telescope into space, which is challenging for logistical and financial reasons.”

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings

    stem

    Stem Education Coalition

    RIKEN campus

    RIKEN is Japan’s largest comprehensive research institution renowned for high-quality research in a diverse range of scientific disciplines. Founded in 1917 as a private research foundation in Tokyo, RIKEN has grown rapidly in size and scope, today encompassing a network of world-class research centers and institutes across Japan.

     
  • richardmitnick 10:06 am on September 7, 2019 Permalink | Reply
    Tags: "Meet Barnard’s Star, , , , , Our Red Dwarf Neighbor", Sky & Telescope   

    From Sky & Telescope: “Meet Barnard’s Star, Our Red Dwarf Neighbor” 

    SKY&Telescope bloc

    From Sky & Telescope

    September 6, 2019
    Daniel Johnson

    The Vitals

    1

    Physical Characteristics

    So far in this series, we’ve examined bright stars easily seen without optical aid. Naturally, these stars tend to be large and luminous. But now we turn to a star that is not nearly so bright, smaller than the Sun, and much closer to home — but no less interesting. We’re talking about Barnard’s Star.

    Barnard’s Star is a red dwarf, a small star only 1/5 the radius of the Sun.

    2
    http://www.hwy.com.au/~sjquirk/images/film/barnard.html

    It’s only a little bigger than Jupiter in diameter, but much denser — Barnard’s Star has about 15% of the Sun’s mass, the equivalent of 160 Jupiters.

    3

    The Alpha Centauri system represents the nearest stellar neighbor to our Sun, just more than four light-years away.

    Centauris Alpha Beta Proxima 27, February 2012. Skatebiker

    Barnard’s Star, on the other hand, is only slightly farther away, at about six light-years distant. Its proximity has made Barnard’s Star a thoroughly studied star. Yet, unlike the brilliant Sirius, proximity to Barnard’s Star doesn’t translate into easy visibility. Because the star is a red dwarf with low luminosity — it puts out only about 1/2,600 as much light as the Sun — we see it at 9th magnitude, so it requires a telescope to view.

    5
    Barnard’s Star is a red dwarf much smaller than the Sun.
    Daniel Johnson

    Barnard’s Star is most notable for its rapid proper motion, tearing across the sky at a surprising 10.3 arcseconds each year — the fastest proper motion of any measured star. Naturally, a contributor to this apparent motion is the star’s close range, but Barnard’s Star actually is on the move as well, traveling about 140 kilometers per second (300,000 mph) in our direction.

    Barnard’s Star is also the home of a recently discovered exoplanet candidate — a so-called “super-Earth” that has perhaps three times the mass of our planet. However, this isn’t the first time that astronomers have claimed to find an exoplanet around Barnard’s Star. One or more gas giants were suspected during the 1960s and 70s, only to be disputed in subsequent decades.

    Origin / Mythology

    Because Barnard’s Star requires a telescope to be seen, it was unknown to our distant ancestors who might have otherwise decorated the star with the types of traditional stories so common to the bright stars of the night sky. Indeed, Barnard’s Star wasn’t discovered until 1916, although it was later found to have appeared in photographic plates as early as 1888. The astronomer Edward Barnard — the star’s namesake — was the first to recognize Barnard’s Star for what it is: a nearby red dwarf with an exceptionally rapid proper motion.

    But even though you won’t find Barnard’s Star woven into the cultures of the ancients, modern society has, in a way, created its own form of “mythology” for the star. In the 1970s, the British Interplanetary Society used Barnard’s Star as the destination of its Daedalus project. The study investigated — only on paper, of course — the possibility of sending an unmanned interstellar probe to a star within a human lifetime. While the Daedalus study took the liberty of assuming the existence of a fusion engine (not to mention fuel tanks far beyond the size of any craft ever built), the study nevertheless found that the concept of an interstellar flyby probe was possible — at least in theory. Barnard’s Star was selected as the destination for the study in part because of its then-suspected exoplanets.

    How to See Barnard’s Star

    Ready for a challenge? Locating Barnard’s Star with your telescope is a task that requires good optics and some practice with star-hopping. A detailed star map of Ophiuchus is also needed, as you’ll need to work your way to Barnard’s Star by using other, brighter stars as guides (a GoTo mount, of course, will make short work of this challenge).

    6
    Barnard’s Star is marked with a cross in the constellation Ophiuchus. Sky & Telescope

    7
    Barnard’s Star is marked with a yellow cross in this close-up diagram. Sky & Telescope

    Generally, summer is a fine time to go searching for Barnard’s Star in the Northern Hemisphere, as Ophiuchus rides high in the sky during that time of year. However, it’s visible closer to the evening horizon well into the autumn. You can imagine the location of Barnard’s Star as the fourth member of the Summer Triangle, turning it into something of a Summer Quadrilateral (a name that surely won’t catch on!). Barnard’s Star isn’t far from the much brighter Rasalhague.

    If you’re a fan of astrophotography and are looking for a long-term project, photographing the gradual proper motion of this star is something that an amateur can realistically achieve. It’s similar to photographing the motion of an asteroid or comet, although the process is much slower. Over the course of a few years, you would be able to stitch together a composite image showing Barnard’s Star traveling slowly against a background of more distant stars.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Sky & Telescope magazine, founded in 1941 by Charles A. Federer Jr. and Helen Spence Federer, has the largest, most experienced staff of any astronomy magazine in the world. Its editors are virtually all amateur or professional astronomers, and every one has built a telescope, written a book, done original research, developed a new product, or otherwise distinguished him or herself.

    Sky & Telescope magazine, now in its eighth decade, came about because of some happy accidents. Its earliest known ancestor was a four-page bulletin called The Amateur Astronomer, which was begun in 1929 by the Amateur Astronomers Association in New York City. Then, in 1935, the American Museum of Natural History opened its Hayden Planetarium and began to issue a monthly bulletin that became a full-size magazine called The Sky within a year. Under the editorship of Hans Christian Adamson, The Sky featured large illustrations and articles from astronomers all over the globe. It immediately absorbed The Amateur Astronomer.

    Despite initial success, by 1939 the planetarium found itself unable to continue financial support of The Sky. Charles A. Federer, who would become the dominant force behind Sky & Telescope, was then working as a lecturer at the planetarium. He was asked to take over publishing The Sky. Federer agreed and started an independent publishing corporation in New York.

    “Our first issue came out in January 1940,” he noted. “We dropped from 32 to 24 pages, used cheaper quality paper…but editorially we further defined the departments and tried to squeeze as much information as possible between the covers.” Federer was The Sky’s editor, and his wife, Helen, served as managing editor. In that January 1940 issue, they stated their goal: “We shall try to make the magazine meet the needs of amateur astronomy, so that amateur astronomers will come to regard it as essential to their pursuit, and professionals to consider it a worthwhile medium in which to bring their work before the public.”

     
  • richardmitnick 11:52 am on June 28, 2019 Permalink | Reply
    Tags: "Astronomers Pinpoint New Fast Radio Burst", , , , , , Sky & Telescope   

    From Sky & Telescope: “Astronomers Pinpoint New Fast Radio Burst” 

    SKY&Telescope bloc

    From Sky & Telescope

    June 27, 2019
    Monica Young

    A next-gen Australian radio array has enabled astronomers to home in on the source of a mysterious fast radio burst — and the source is not what they expected.

    1
    The galaxy from which the burst originated was imaged by three of the world’s largest optical telescopes – Keck, Gemini South and the European Southern Observatory’s Very Large Telescope. The image combined with radio data shows that FRB 180924 lies on the outskirts of a massive “dead” galaxy.
    CSIRO / Sam Moorfield

    Keck Observatory, operated by Caltech and the University of California, Maunakea Hawaii USA, 4,207 m (13,802 ft)

    Gemini/South telescope, Cerro Tololo Inter-American Observatory (CTIO) campus near La Serena, Chile, at an altitude of 7200 feet

    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,

    If you could “listen” to the whole radio sky at once, you’d mostly hear a faint background hiss, like the static between radio stations. But roughly every 10 seconds, you’d pick up a downslurred whistle reminiscent of the Northern Cardinal’s song. This bright sound comes from so-called fast radio bursts (FRBs). Each one lasts only a small fraction of a second (hence “fast”), but in that time it carries some 10,000 times the energy of the Sun.

    Since their discovery in 2007, FRBs have maintained an air of mystery. Astronomers have spotted 76 of the fleet emissions so far (and counting), but theories about their origins abound in part because they’re difficult to pin down. Until now, astronomers have only been able to localize one emission, FRB 121102, and that was only because it repeated often enough that astronomers could home in on its origin.

    Now, Keith Bannister (CSIRO) and colleagues have used the 36-dish Australian Square Kilometer Array Pathfinder (ASKAP) to pinpoint the source of another FRB — one that doesn’t repeat. The feat, published on June 27th in Science, offers another avenue to understanding these puzzling sources.

    Australian Square Kilometre Array Pathfinder (ASKAP) is a radio telescope array located at Murchison Radio-astronomy Observatory (MRO) in the Australian Mid West. ASKAP consists of 36 identical parabolic antennas, each 12 metres in diameter, working together as a single instrument with a total collecting area of approximately 4,000 square metres.

    One of These Is Not Like the Other

    When ASKAP captured the signal known as FRB 180924, an automated search pipeline triggered the receivers to save everything about the event. That information enabled ASKAP to not only detect the event, it also recorded enough information to pinpoint its source to within 0.12 arcsecond, in a massive galaxy whose light has traveled for 3.6 billion years to reach Earth.

    Bannister’s team followed up with sensitive observations of the galaxy and its surroundings using the Very Large Telescope and the Gemini South Telescope in Chile and the Keck II Telescope in Hawai‘i. Images show the galaxy is a cross between an elliptical and a spiral. If it has any spiral arms around its big bulge, they’re tightly wound and difficult to see. Spectroscopic measurements show little to no evidence of star formation. If the burst really belongs to this galaxy, it’s in its anemic outer reaches.

    This finding is in stark contrast to the home of the repeating burst FRB 121102. It appears to originate from within a radio-emitting nebula that’s part of a dwarf galaxy that’s birthing stars at a high rate. Given the plethora of new stars, astronomers think FRB 121102 is likely a highly magnetized kind of newborn neutron star known as a magnetar.

    3
    A composite image of the field around the first repeating fast radio burst, FRB 121102 (indicated), showed that the burst came from a star-forming dwarf galaxy.
    Gemini Observatory / AURA / NSF / NRC

    FRBs are known for having large dispersion measures, which means that the lower frequencies arrive much later than the higher-frequency ones. That’s what gives them the “sound” of a cardinal-like downslurred whistle. The longer-frequency photons are delayed by interacting with electrons, and in the case of FRB 121102, the whistle was so extended, it indicated that not only had the pulse traveled a long way, but that the source itself was probably embedded in highly magnetized plasma, which supports the magnetar scenario.

    But are all FRBs magnetars? Astronomers have already been saying that even if the scenario pans out for FRB 121102, it might not explain FRBs as a population. The vast majority of these events, after all, don’t repeat.

    “Basing models entirely on [FRB 121102’s] properties is dangerous, since the FRB population could be made up of different classes of sources,” says Victoria Kaspi (McGill University, Canada). Indeed, Bannister and colleagues’ localization of FRB 180924 in a galaxy that has retired from star formation suggests that this source has nothing to do with newborn stars, magnetars or otherwise.

    “We now know that some FRBs originate from environments very different from that of FRB 121102,” says Kaspi, who was not involved in the study. “That is a very important finding!”

    There’s another aspect of FRB 180924 that’s also telling: its dispersion measure. The distance to the source’s galaxy completely explains the dispersion measure so, unlike the repeater, this source doesn’t seem to be embedded in a highly magnetic plasma.

    “If they are all like 121102 then yes, we’d expect the source itself to contribute [to the dispersion measure],” Kaspi notes. “But clearly, they are not all like FRB 121102!”

    This single burst is likely the first of many that ASKAP will pinpoint, and other telescopes are working on that ability, too. The Canadian Hydrogen Intensity Mapping Experiment (CHIME) array, for example, could localize sources if it had outrigger telescopes, like “mini-CHIMES,” to provide additional information.

    CHIME Canadian Hydrogen Intensity Mapping Experiment -A partnership between the University of British Columbia, the University of Toronto, McGill University, Yale and the National Research Council in British Columbia, at the Dominion Radio Astrophysical Observatory in Penticton, British Columbia, CA Altitude 545 m (1,788 ft)

    That would be a boon for an instrument that’s already finding FRBs by the dozen. “Indeed we are planning CHIME outrigger telescopes right now,” Kaspi says.

    For now, FRBs retain their mystery, but it’s only a matter of time before we unveil what unique physics is producing these events.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Sky & Telescope magazine, founded in 1941 by Charles A. Federer Jr. and Helen Spence Federer, has the largest, most experienced staff of any astronomy magazine in the world. Its editors are virtually all amateur or professional astronomers, and every one has built a telescope, written a book, done original research, developed a new product, or otherwise distinguished him or herself.

    Sky & Telescope magazine, now in its eighth decade, came about because of some happy accidents. Its earliest known ancestor was a four-page bulletin called The Amateur Astronomer, which was begun in 1929 by the Amateur Astronomers Association in New York City. Then, in 1935, the American Museum of Natural History opened its Hayden Planetarium and began to issue a monthly bulletin that became a full-size magazine called The Sky within a year. Under the editorship of Hans Christian Adamson, The Sky featured large illustrations and articles from astronomers all over the globe. It immediately absorbed The Amateur Astronomer.

    Despite initial success, by 1939 the planetarium found itself unable to continue financial support of The Sky. Charles A. Federer, who would become the dominant force behind Sky & Telescope, was then working as a lecturer at the planetarium. He was asked to take over publishing The Sky. Federer agreed and started an independent publishing corporation in New York.

    “Our first issue came out in January 1940,” he noted. “We dropped from 32 to 24 pages, used cheaper quality paper…but editorially we further defined the departments and tried to squeeze as much information as possible between the covers.” Federer was The Sky’s editor, and his wife, Helen, served as managing editor. In that January 1940 issue, they stated their goal: “We shall try to make the magazine meet the needs of amateur astronomy, so that amateur astronomers will come to regard it as essential to their pursuit, and professionals to consider it a worthwhile medium in which to bring their work before the public.”

     
  • richardmitnick 10:28 am on January 29, 2019 Permalink | Reply
    Tags: , , , , , , Quasars are brilliant enough to be seen from a universe less than a billion years old making them prime targets for reaching earlier epochs, Sky & Telescope, , Two decades ago astronomers discovered that the universe was not only expanding but accelerating in its expansion, Type Ia supernovae have long been the brightest of standard candles, What Quasar Cosmology Can Teach Us About Dark Energy   

    From Sky & Telescope: “What Quasar Cosmology Can Teach Us About Dark Energy” 

    SKY&Telescope bloc

    From Sky & Telescope

    January 28, 2019
    Monica Young

    Astronomers have found a way to turn quasars into standard candles, with potentially far-reaching implications for the nature of mysterious dark energy.

    Standard Candles to measure age and distance of the universe NASA

    National Science Foundation (NASA, JPL, Keck Foundation, Moore Foundation, related) — Funded BICEP2 Program; modifications by E. Siegel.

    Two decades ago astronomers discovered that the universe was not only expanding but accelerating in its expansion. They dubbed the cause of this acceleration dark energy, but what that actually is remains as ineffable now as it was then.

    The weird repulsive force has left its fingerprints on the earliest photons we can see, the ones emitted as part of the cosmic microwave background (CMB), when the infant universe was only 370,000 years old. Yet dark energy only began to dominate expansion as the universe entered middle age, after 9 billion years or so.

    Now, Guido Risaliti (University of Florence and INAF-Astrophysical Observatory of Arcetri, Italy) and Elisabeta Lusso (Durham University, UK) are using quasars to probe the cosmology of our universe’s relatively unexplored adolescence. The results, appearing in the January 28th Nature Astronomy, promise to reveal dark energy’s true nature.

    The leading explanation for dark energy has long been the cosmological constant, also known as vacuum energy. This energy inherent to empty space arises from quantum theory, which says that even when space appears empty of particles, it’s actually filled with quantum fields. These fields exert a negative pressure that counteracts the attractive force of gravity. However, calculations of vacuum energy overpredict the measured dark energy density by an astounding 120 orders of magnitude (that’s a 1 followed by 120 zeroes!). That the cosmological constant remains the favorite theory speaks to how little we understand dark energy — and how difficult the measurements involved are.

    Studying the universe at any age starts with gauging cosmological distance — the farther we look, the further back in time we see­­ ­— but we can’t just roll out a tape measure to the stars. Enter standard candles, objects for which we can measure an intrinsic luminosity. By comparing how bright a standard candle appears to be with how bright it really is, we can determine its distance without knowing anything about cosmology.

    Type Ia supernovae have long been the brightest of standard candles. Observations of these detonating white dwarfs led to the Nobel-winning discovery of accelerating expansion announced back in 1998. The supernovae extended our reach to when the universe was a third of its current age. That’s a pretty good tape measure! Nevertheless, it only probes the era when dark energy began to dominate the universe’s expansion. To see farther back, and probe the era when dark energy overtook matter, astronomers need something even more luminous.

    Quasars as Standard Candles

    2
    Understanding the physics of quasar accretion disks (blue-white) and X-ray-emitting coronae (yellow) can help astronomers use quasars as standard candles.
    NASA / CXC / M. Weiss.

    What’s more luminous than an exploding star? A gas-guzzling supermassive black hole would do the trick. After all, quasars are brilliant enough to be seen from a universe less than a billion years old, making them prime targets for reaching earlier epochs.

    Unfortunately, quasars also exhibit a bewildering variety of forms — astronomers have long thought they were anything but standard. Case in point: Astronomers have known for the past 30 years that more visibly luminous quasars emit relatively fewer X-rays, but there was too much variance from one quasar to another to pin down any one quasar’s intrinsic brightness.

    Risaliti and Lusso realized that this relation between the emission of X-rays and visible light must arise from the physics of quasar accretion disks. The disk itself emits visible light, while a hot, gaseous corona emits the X-rays. The two are intertwined by straightforward physics; it’s just that previously, contaminants had been mucking things up. So for this study, Risaliti and Lusso removed any sources where disk emission is obscured (by dust or gas) or contaminated (by emission from a fast-flowing black hole jet). Their careful selection results in a much tighter, more useful relation. Using data from the Sloan Digital Sky Survey and the XMM-Newton, Chandra, and Swift space telescopes, the duo then apply the relation to turn 1,600 quasars into standard candles.

    SDSS 2.5 meter Telescope at Apache Point Observatory, near Sunspot NM, USA, Altitude 2,788 meters (9,147 ft)

    ESA/XMM Newton

    NASA/Chandra X-ray Telescope

    NASA Neil Gehrels Swift Observatory

    3
    The history of the universe shows a crucial time when the expansion switched from decelerating to accelerating. But the future still hangs in the balance, depending on the behavior of dark energy. If dark energy increases, everything will be torn apart; if it changes direction, the cosmos could end in a big crunch.
    NASA / CXC / M.Weiss

    The quasars help Risaliti and Lusso fill in the gap along the cosmic timeline, looking back to an adolescent universe only a billion years old. From this data, the team finds that dark energy is actually increasing over cosmic time.

    The results appear to rule out the cosmological constant, which predicts a constant energy density. That’s a bit of a relief given that vacuum energy overpredicts the observations so badly. (Did I mention the 120 orders of magnitude?) Evolving dark energy may also help resolve an ongoing tension between measurements of the universe’s current expansion rate.

    Nevertheless, the results are unsettling from a philosophical standpoint: If dark energy density really does increase over time, then so does the repulsive force it exerts, potentially ending our universe in a Big Rip.

    Too Early To Tell

    Let’s not give up on the universe just yet, though. Phil Hopkins (Caltech), who wasn’t involved in the study, urges caution in interpreting its results. The relation that Lusso and Risaliti use to turn quasars into standard candles may itself evolve over time, making those quasars not so standard. For example, if quasars slow their gas-guzzling as mergers become less frequent, that might change the shape of the relation between the emission of X-rays and visible light. “[The relation] only needs to evolve a little bit to explain these observations,” he adds.

    That said, Hopkins agrees the results are interesting and worth following up with even bigger and better samples. The authors also note that other studies probing the adolescent universe are forthcoming. The bar is high these days for disproving the standard cosmological model, and only time and additional study will tell if this is the method that will do it.

    See the full article here .
    See also from Chandra here.

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Sky & Telescope magazine, founded in 1941 by Charles A. Federer Jr. and Helen Spence Federer, has the largest, most experienced staff of any astronomy magazine in the world. Its editors are virtually all amateur or professional astronomers, and every one has built a telescope, written a book, done original research, developed a new product, or otherwise distinguished him or herself.

    Sky & Telescope magazine, now in its eighth decade, came about because of some happy accidents. Its earliest known ancestor was a four-page bulletin called The Amateur Astronomer, which was begun in 1929 by the Amateur Astronomers Association in New York City. Then, in 1935, the American Museum of Natural History opened its Hayden Planetarium and began to issue a monthly bulletin that became a full-size magazine called The Sky within a year. Under the editorship of Hans Christian Adamson, The Sky featured large illustrations and articles from astronomers all over the globe. It immediately absorbed The Amateur Astronomer.

    Despite initial success, by 1939 the planetarium found itself unable to continue financial support of The Sky. Charles A. Federer, who would become the dominant force behind Sky & Telescope, was then working as a lecturer at the planetarium. He was asked to take over publishing The Sky. Federer agreed and started an independent publishing corporation in New York.

    “Our first issue came out in January 1940,” he noted. “We dropped from 32 to 24 pages, used cheaper quality paper…but editorially we further defined the departments and tried to squeeze as much information as possible between the covers.” Federer was The Sky’s editor, and his wife, Helen, served as managing editor. In that January 1940 issue, they stated their goal: “We shall try to make the magazine meet the needs of amateur astronomy, so that amateur astronomers will come to regard it as essential to their pursuit, and professionals to consider it a worthwhile medium in which to bring their work before the public.”

     
  • richardmitnick 2:32 pm on December 19, 2018 Permalink | Reply
    Tags: , , , , , Sky & Telescope, What LIGO Teaches Us About Black Holes   

    From Sky & Telescope: “What LIGO Teaches Us About Black Holes” 

    SKY&Telescope bloc

    From Sky & Telescope

    December 18, 2018
    Camille M. Carlisle

    The rising count of gravitational-wave events is giving us a new look at a once-invisible population of black holes.

    1
    Now iconic imsge of two black holes prepare to merge in this artist’s illustration.
    LIGO / Caltech / MIT / Aurore Simonnet(Sonoma State)

    2
    This artist’s conception portrays two neutron stars at the moment of collision. New observations confirm that colliding neutron stars probably produce short gamma-ray bursts. Dana Berry / SkyWorks Digital, Inc.

    Two weeks ago, scientists announced the detection of four black hole mergers, discovered thanks to the undulations they created in the fabric of spacetime. These latest events bring the tally of such smashups to 10. (An 11th is the famed double neutron star collision.)

    Now that we’ve entered the double digits for gravitational-wave discoveries, I’d like to stop and take a look at what these detections are revealing as a group. We’re nowhere near the illuminating statistical power brought by thousands of examples, as we are with exoplanets, but we can still sketch out an intriguing picture.

    Black holes are simple creatures; their two defining characteristics are their spin and mass. Astrophysicists measure black hole spin as a fraction of the theoretical maximum, which depends on the object’s mass and some other numbers. The values range from 0 (not spinning) to 1.

    A binary black hole system involves three spins: each individual black hole’s rotation, plus the two objects’ revolution around each other. These spins don’t necessarily line up. Think of two tops, spiraling in toward each other. The tops can stand straight up, their axes perfectly perpendicular to the tabletop. But they can also lean at various angles, roll on their sides, or even rotate backwards compared to the direction of the circuit each top traces around its partner.

    The same holds true for black holes. With current detector sensitivities, it’s difficult for the LIGO and Virgo teams to pinpoint the individual spins of the binary members that unite. But they can make some estimates, and the spin of the created black hole is fairly clear.

    Since the first gravitational-wave detections began piling up, I’ve been watching the spin measurements with growing fascination. Maya Fishbach (University of Chicago) and her colleagues had predicted that a black hole made by the merger of two others would spin at a rate that’s roughly 70% of its maximum — regardless of the parent objects’ masses and spins. One after another, each LIGO/Virgo detection has confirmed this prediction.

    What’s equally interesting, though, is that none of the original binary members appear to have spins this high. In the reanalysis recently released, the teams calculated each merging black hole’s spin. Only two events — GW151226 and GW170729 — involved objects with any detectable spins; the rest are basically zero. (The zeros include the parent black holes of GW170104, at least one of which researchers had thought spun backwards. The new analysis, taking better account of detector noise, revises that inference.)

    The caveat here is that the spins are measured in terms of how tilted they are compared to the binary’s orbital plane. It’s possible that the binary black holes might be whirling at wonky angles, unseen. But the researchers suspect this isn’t merely a matter of tilt hiding the rotation; the black holes really do have lower spins.

    I reached out to Fishbach for help understanding what these numbers mean. It comes down to origins, she explains. If the binary members really do spin slowly or not at all, then we can essentially rule out the scenario in which the LIGO/Virgo pairs all contain black holes formed from previous mergers. In other words, we are likely watching the collisions of first-generation black holes, made from stars.

    The masses support this conclusion, she adds. Above a mass of about 45 Suns there should be a gap, because the stars that are big enough to create black holes in this range instead obliterate themselves in a particularly destructive kind of blast that doesn’t make a black hole. The biggest binary black hole LIGO and Virgo have detected is approximately 50 Suns — potentially problematic for a supernova creation, but not indubitably in the no-man’s-land. If in the future LIGO and Virgo detect binary black holes in this forbidden zone, then it would be clear evidence of a second-generation black hole.

    We’re still unable to say much about how the binaries paired up to begin with. GW151226 and GW170729, the only two events with clearly spinning members, involved black holes that rotate in the same direction as their orbit around each other. That might indicate that each pair was born as a couple, instead of joining up later in life: We’d naïvely expect all three spins in the binary to line up if the black holes formed from a binary star system, whereas the black holes might be misaligned if they paired up after their creation, perhaps by meeting in the center of a globular star cluster. However, astronomers do debate this simplistic picture, since supernovae or binary interactions could knock the resulting black holes askew. That insight will have to wait for the future.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Sky & Telescope magazine, founded in 1941 by Charles A. Federer Jr. and Helen Spence Federer, has the largest, most experienced staff of any astronomy magazine in the world. Its editors are virtually all amateur or professional astronomers, and every one has built a telescope, written a book, done original research, developed a new product, or otherwise distinguished him or herself.

    Sky & Telescope magazine, now in its eighth decade, came about because of some happy accidents. Its earliest known ancestor was a four-page bulletin called The Amateur Astronomer, which was begun in 1929 by the Amateur Astronomers Association in New York City. Then, in 1935, the American Museum of Natural History opened its Hayden Planetarium and began to issue a monthly bulletin that became a full-size magazine called The Sky within a year. Under the editorship of Hans Christian Adamson, The Sky featured large illustrations and articles from astronomers all over the globe. It immediately absorbed The Amateur Astronomer.

    Despite initial success, by 1939 the planetarium found itself unable to continue financial support of The Sky. Charles A. Federer, who would become the dominant force behind Sky & Telescope, was then working as a lecturer at the planetarium. He was asked to take over publishing The Sky. Federer agreed and started an independent publishing corporation in New York.

    “Our first issue came out in January 1940,” he noted. “We dropped from 32 to 24 pages, used cheaper quality paper…but editorially we further defined the departments and tried to squeeze as much information as possible between the covers.” Federer was The Sky’s editor, and his wife, Helen, served as managing editor. In that January 1940 issue, they stated their goal: “We shall try to make the magazine meet the needs of amateur astronomy, so that amateur astronomers will come to regard it as essential to their pursuit, and professionals to consider it a worthwhile medium in which to bring their work before the public.”

     
  • richardmitnick 7:52 pm on October 25, 2018 Permalink | Reply
    Tags: , , , , Donatiello I is a tiny galaxy about 10 million light-years away, Dwarf Galaxy Found by Amateur on a home made telescope, Sky & Telescope   

    From Sky & Telescope: “Dwarf Galaxy Found by Amateur on a home made telescope” 

    SKY&Telescope bloc

    From Sky & Telescope

    October 24, 2018
    Christopher Crockett

    Donatiello I is a tiny galaxy about 10 million light-years away, and it was discovered by an Italian hobbyist with a homemade telescope.

    1
    The dwarf spheroidal galaxy Donatiello I, discovered by amateur astronomer Giuseppe Donatiello, sits in the middle of this composite image.
    Galileo National Telescope / Gran Telescopio Canarias / G. Donatiello

    In an era of giant telescopes scouring the sky from both the ground and in space, one could be forgiven for thinking there wasn’t much left for an enthusiastic hobbyist to discover. But with patience and the right equipment, even an amateur astronomer can stumble on to an undiscovered galaxy.

    From the dark skies of Pollino National Park in southern Italy, Giuseppe Donatiello had been investigating the Andromeda Galaxy with his home-built telescope, looking for previously reported dwarf galaxies and stellar streams. In images acquired late in 2010 and 2013, Donatiello noticed an unidentified smudge of light. That smudge turned out to be a dwarf spheroidal galaxy — now dubbed Donatiello I — lurking on the far side of Andromeda.

    “I literally jumped for joy,” says Donatiello. “I have always had a great interest in the Local Group and for dwarf galaxies in general, so finding one of these systems is truly an immense joy.”

    Donatiello I is a runt, as far as galaxies go. Assuming a distance of around 10 million light-years, it appears to be roughly several thousand light-years across. Our own galaxy, by comparison, spans about 100,000 light-years. The dwarf galaxy is faint, too. With a surface brightness of just 26.5 magnitudes per square arcsecond, it’s barely visible against the sky.

    To make his discovery, Donatellio relied on an extra-low dispersion 127-mm f/9 refractor, assembled from parts from different telescopes, and an off-the-shelf cooled 2-megapixel CCD camera. “Modern amateur astronomers have amazing equipment for doing significant contributions to new topics in astronomy, like galaxy formation [and] dwarf galaxy censuses,” says David Martínez-Delgado (Heidelberg University, Germany), lead author on the paper reporting the discovery, published October 10th on the astronomy preprint arXiv The paper will appear in Astronomy and Astrophysics.

    Martínez-Delgado came across the discovery on Facebook. Donatiello had posted his discovery image to the site, after convincing himself that the galaxy was the real deal when he noticed a similar smudge at the same coordinates (RA 01h 11m 40.37s, dec. +34° 36′ 3.2″) in images from the Sloan Digital Sky Survey. Martínez-Delgado reached out and offered to collaborate on a paper, partly to ensure that Donatiello got the discovery credit that he deserved.

    The pros took a closer look with the 3.58-meter Galileo National Telescope and the 10.4-meter Gran Telescopio Canarias, both on the Canary Island of La Palma. Martínez-Delgado and colleagues tried to measure the distance to Donatiello I by identifying the brightest red giant stars in the dense center of the galaxy and comparing their apparent magnitudes to their intrinsic luminosities. Atmospheric conditions weren’t ideal for this kind of work, providing estimates only, but the dwarf galaxy appears to be old and on its own, just outside our Local Group of galaxies.

    Italian National Telescope Galileo On La Palma at Roque de los Muchachos Observatory, altitude 2,370 m (7,780 ft)

    Gran Telescopio Canarias at the Roque de los Muchachos Observatory on the island of La Palma, in the Canaries, Spain, sited on a volcanic peak 2,267 metres (7,438 ft) above sea level

    Martínez-Delgado and colleagues tried to measure the distance to Donatiello I by identifying the brightest red giant stars in the dense center of the galaxy and comparing their apparent magnitudes to their intrinsic luminosities. Atmospheric conditions weren’t ideal for this kind of work, providing estimates only, but the dwarf galaxy appears to be old and on its own, just outside our Local Group of galaxies.

    “If Donatiello I is actually an isolated old galaxy, its stellar population can provide important clues about its star formation history and about the process that could stop the star formation,” says Martínez-Delgado. “There is no interaction with massive host galaxies here, so it is not as easy to explain how the galaxy lost its gas a long time ago.”

    Martínez-Delgado and colleagues hope to get a better look at this galaxy with the Hubble Space Telescope. That should allow them to nail down the distance, which in turn would provide more precise estimates of other properties such as size and mass.

    Donatiello, meanwhile, plans to keep searching. “I have always had a great interest in dwarf galaxies, so I will continue in this direction,” he says. “But more generally, I am interested in galactic archeology, so at the same time I will dedicate myself to the search for stellar streams around Milky-Way-like galaxies.”

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Sky & Telescope magazine, founded in 1941 by Charles A. Federer Jr. and Helen Spence Federer, has the largest, most experienced staff of any astronomy magazine in the world. Its editors are virtually all amateur or professional astronomers, and every one has built a telescope, written a book, done original research, developed a new product, or otherwise distinguished him or herself.

    Sky & Telescope magazine, now in its eighth decade, came about because of some happy accidents. Its earliest known ancestor was a four-page bulletin called The Amateur Astronomer, which was begun in 1929 by the Amateur Astronomers Association in New York City. Then, in 1935, the American Museum of Natural History opened its Hayden Planetarium and began to issue a monthly bulletin that became a full-size magazine called The Sky within a year. Under the editorship of Hans Christian Adamson, The Sky featured large illustrations and articles from astronomers all over the globe. It immediately absorbed The Amateur Astronomer.

    Despite initial success, by 1939 the planetarium found itself unable to continue financial support of The Sky. Charles A. Federer, who would become the dominant force behind Sky & Telescope, was then working as a lecturer at the planetarium. He was asked to take over publishing The Sky. Federer agreed and started an independent publishing corporation in New York.

    “Our first issue came out in January 1940,” he noted. “We dropped from 32 to 24 pages, used cheaper quality paper…but editorially we further defined the departments and tried to squeeze as much information as possible between the covers.” Federer was The Sky’s editor, and his wife, Helen, served as managing editor. In that January 1940 issue, they stated their goal: “We shall try to make the magazine meet the needs of amateur astronomy, so that amateur astronomers will come to regard it as essential to their pursuit, and professionals to consider it a worthwhile medium in which to bring their work before the public.”

     
  • richardmitnick 3:56 pm on June 16, 2017 Permalink | Reply
    Tags: , , , , NGC 7582, Ring Found Around a Galaxy’s 'Hidden' Black Hole, Sky & Telescope   

    From Sky & Telescope: “Ring Found Around a Galaxy’s ‘Hidden’ Black Hole” 

    SKY&Telescope bloc

    Sky & Telescope

    June 13, 2017
    Monica Young

    1
    This ultraviolet widefield image shows NGC 7582 (right bottom) with its galactic neighbors, NGC 7599 (left) and NGC 7590 (top middle). NASA / JPL-Caltech

    A team of astronomers has taken a close look at a nearby galaxy — and discovered an unusual structure that sheds light on supermassive black holes’ relationships with their host galaxies.

    A spiral galaxy 70 million light-years from Earth hosts a supermassive black hole some 50 million times the mass of our Sun. Those numbers alone sound almost like science fiction, but a recent closer look at the center of this ordinary galaxy revealed something even more bizarre: a ring of dust, gas, and stars spanning 2,000 light-years that dwarfs the black hole itself. The result was presented at the 230th meeting of the American Astronomical Society in Austin, Texas.

    From previous visible-light, near-infrared, and X-ray observations, astronomers already knew this galaxy, dubbed NGC 7582, was of a rare breed: its central black hole gorges on a gas buffet, but we hardly see the shining gas as it’s pulled into the maw, thanks to large swaths of dust and gas obscuring our view of the galaxy’s core.

    This type of “hidden” active galaxy is rare in the sense that these galaxies are hard to find, but astronomers are pretty sure they actually outnumber “normal” active galaxies by at least 2 to 1. What remains unclear is what is doing the hiding: Do broad dust lanes hide galactic centers from view? Or does a wall of dust somehow form closer to the black hole?

    Ring Around a Galaxy, Pocket Full of Outflows

    To help answer those questions, Stéphanie Juneau (National Optical Astronomy Observatory and CEA-Saclay, France) and colleagues used the MUSE instrument on the Very Large Telescope in Chile to image the center of spiral galaxy NGC 7582.

    ESO MUSE on the VLT

    ESO/VLT at Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level

    2
    Image of the barred spiral galaxy NGC 7582, which hosts a hidden black hole. Observations from the MUSE instrument at the Very Large Telescope in Chile (inset) reveal emission from a hot gaseous wind (in green) launched by the black hole. Background image: S. Binnewies and J. Pöpsel (Capella Observatory); Inset: S. Juneau (NOAO, CEA-Saclay)

    The result was more than a pretty picture — each of the image’s 90,000 pixels came with a spectrum attached, which reveals how that part of the galaxy is moving. Using these images cum spectra, Juneau’s team separated the overall rotation of stars around the galactic center from the rotation of an inner ring, made of dust, gas, and stars, that’s spinning even faster than the galaxy itself.

    3
    This spectral image of NGC 7582 shows which way the gas at each point in the galaxy is moving. Red indicates that the stars are moving away from our point of view, while blue indicates stars that are moving toward us. The barred spiral galaxy rotates, of course, which is why one side is red and the other is blue. But at its center, there’s a ring that’s spinning even faster. Since we see the ring edge-on, we see it as two circles (blue and orange/yellow) that stand out from the rest of the galaxy’s core. The ring spans 2,000 light-years. Juneau et al. 2017.

    Previous observations had shown that the black hole is feeding from a disk-shaped buffet, and we’re seeing that gas spiraling around the maw face-on, or nearly so. This accretion disk is less than a couple light-years wide. The dusty ring around it, on the other hand, is 2,000 light-years across — and we’re seeing it edge-on.

    The images also revealed the outlines of a cone-shaped outflow: hot gas that’s spewing from the black hole. The direction of the black hole’s wind, though, appears to be shaped by the dusty ring, which deflects the wind and protects the galaxy from its power.

    Evidence for a Minor Merger

    Where did this galaxy-protecting ring come from? Previous radio observations have shown that NGC 7582 has a small tail of neutral hydrogen gas, probably the ghostly remnant of interaction with another galaxy. NGC 7582 doesn’t share the feature with any of its galactic neighbors. So, the authors speculate, the galaxy may have recently experienced a minor merger, perhaps with a dwarf galaxy that was once in orbit around it.

    If the dwarf ventured too close, the spiral would have torn it apart, sending much of its gas toward the larger galaxy’s center. The interaction could have fed the black hole (which would in turn create an powerful wind), while at the same time creating the dusty ring that shields the galaxy from the black hole’s power.

    It’s a neat explanation but, as Juneau notes, it’s not the only one. There are more ways than mergers to make a dusty nuclear ring, and the ring probably isn’t the only thing hiding NGC 7582 from view. Ironically, the way to better understand these galaxies that harbor hidden black holes is simply to find more of them.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    Sky & Telescope magazine, founded in 1941 by Charles A. Federer Jr. and Helen Spence Federer, has the largest, most experienced staff of any astronomy magazine in the world. Its editors are virtually all amateur or professional astronomers, and every one has built a telescope, written a book, done original research, developed a new product, or otherwise distinguished him or herself.

    Sky & Telescope magazine, now in its eighth decade, came about because of some happy accidents. Its earliest known ancestor was a four-page bulletin called The Amateur Astronomer, which was begun in 1929 by the Amateur Astronomers Association in New York City. Then, in 1935, the American Museum of Natural History opened its Hayden Planetarium and began to issue a monthly bulletin that became a full-size magazine called The Sky within a year. Under the editorship of Hans Christian Adamson, The Sky featured large illustrations and articles from astronomers all over the globe. It immediately absorbed The Amateur Astronomer.

    Despite initial success, by 1939 the planetarium found itself unable to continue financial support of The Sky. Charles A. Federer, who would become the dominant force behind Sky & Telescope, was then working as a lecturer at the planetarium. He was asked to take over publishing The Sky. Federer agreed and started an independent publishing corporation in New York.

    “Our first issue came out in January 1940,” he noted. “We dropped from 32 to 24 pages, used cheaper quality paper…but editorially we further defined the departments and tried to squeeze as much information as possible between the covers.” Federer was The Sky’s editor, and his wife, Helen, served as managing editor. In that January 1940 issue, they stated their goal: “We shall try to make the magazine meet the needs of amateur astronomy, so that amateur astronomers will come to regard it as essential to their pursuit, and professionals to consider it a worthwhile medium in which to bring their work before the public.”

     
  • richardmitnick 2:14 pm on January 30, 2017 Permalink | Reply
    Tags: Cosmic Void “Pushes” Milky Way, Great Attractor, , , Sky & Telescope   

    From Sky & Telescope: “Cosmic Void “Pushes” Milky Way” 

    SKY&Telescope bloc

    Sky & Telescope

    January 30, 2017
    Camille M. Carlisle

    Astronomers have discovered a giant cosmic void that explains why our Local Group of galaxies is moving through the universe as fast as it is.

    Local Group. Andrew Z. Colvin 3 March 2011
    Local Group. Andrew Z. Colvin 3 March 2011

    1
    This visualization is a slice of the local cosmic structure, roughly centered on the Local Group. The black arrows show the “flow” matter follows in this gravitational watershed. Analysis of these flow patterns has revealed that there’s probably a large, unseen void (gray-brown at right) that is “pushing” us toward the Shapley Supercluster (green), which is in turn gravitationally pulling us toward it. The yellow arrow is the direction of the so-called cosmic dipole.
    Yehuda Hoffman

    The Milky Way Galaxy is one of the biggest galaxies in the Local Group, a modest cluster of stellar metropolises. The Local Group, in turn, lies in a filament of the much larger cosmic structure. The galaxy clusters in this cosmic web don’t stay still, but rather slowly gravitate (literally) toward the largest clusters.

    Astronomers have known since the 1980s that the Local Group is moving toward what’s called the Great Attractor, a dense collection in the vicinity of the Centaurus, Norma, and Hydra clusters about 160 million light-years away. They’ve also found another, equally influential attractor called the Shapley Supercluster, a huge structure along roughly the same line of sight but four times farther away.

    In 2006, when Dale Kocevski and Harald Ebeling (both then of University of Hawai’i) confirmed Shapley’s influence on the Local Group by mapping out how clusters clump together on the sky, they also saw hints of a void in the opposite direction.

    Now, using the Cosmicflows-2 catalog of galaxies, Yehuda Hoffman (Hebrew University, Jerusalem) and colleagues have mapped out the movements of more than 8,000 galaxies and confirmed that, yes, the two titans that determine how local galaxies flow through the cosmic web are Shapley and this single, as-yet unmapped void.

    Think of the local cosmic structure as a gravitational water park: the twisty slides start high (where the void is) and end up low (where the cluster is), with the natural motion always being down — that is, with gravity. Galaxies toboggan along the gravitational slides.

    But how fast the galaxies go depends on how tall the slides are. In the same way, the fact that there’s a big, “high” void in one part of the gravitational landscape makes the Local Group flow faster toward the dense, “low-lying” regions in the other direction than it would otherwise. The net effect is as though the void is pushing in the same direction as the supercluster is pulling. It may even be that the void, which the team labels the dipole repeller in their January 30th Nature Astronomy paper, has more of an effect on the Local Group’s motion than the Shapley region does on its own.

    This discovery actually may solve a longstanding cosmic conundrum. Astronomers knew that the Local Group moves with respect to the cosmic microwave background (CMB), the ocean of photons suffusing the universe that is left over from the Big Bang. This motion is called the CMB dipole. But the velocity (630 km/s, or 1.4 million mph) was about double what it should be, if Shapley and the other clusters were responsible. The repeller’s effect essentially doubles Shapley’s pull, explaining why the Local Group moves as fast as it does.

    Below, you’ll find a movie explaining the result. Don’t mind the jargon: if it fazes you, the illustrations should carry you through. Credit: Yehuda Hoffman


    Access mp4 video here .

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    Sky & Telescope magazine, founded in 1941 by Charles A. Federer Jr. and Helen Spence Federer, has the largest, most experienced staff of any astronomy magazine in the world. Its editors are virtually all amateur or professional astronomers, and every one has built a telescope, written a book, done original research, developed a new product, or otherwise distinguished him or herself.

    Sky & Telescope magazine, now in its eighth decade, came about because of some happy accidents. Its earliest known ancestor was a four-page bulletin called The Amateur Astronomer, which was begun in 1929 by the Amateur Astronomers Association in New York City. Then, in 1935, the American Museum of Natural History opened its Hayden Planetarium and began to issue a monthly bulletin that became a full-size magazine called The Sky within a year. Under the editorship of Hans Christian Adamson, The Sky featured large illustrations and articles from astronomers all over the globe. It immediately absorbed The Amateur Astronomer.

    Despite initial success, by 1939 the planetarium found itself unable to continue financial support of The Sky. Charles A. Federer, who would become the dominant force behind Sky & Telescope, was then working as a lecturer at the planetarium. He was asked to take over publishing The Sky. Federer agreed and started an independent publishing corporation in New York.

    “Our first issue came out in January 1940,” he noted. “We dropped from 32 to 24 pages, used cheaper quality paper…but editorially we further defined the departments and tried to squeeze as much information as possible between the covers.” Federer was The Sky’s editor, and his wife, Helen, served as managing editor. In that January 1940 issue, they stated their goal: “We shall try to make the magazine meet the needs of amateur astronomy, so that amateur astronomers will come to regard it as essential to their pursuit, and professionals to consider it a worthwhile medium in which to bring their work before the public.”

     
  • richardmitnick 11:32 am on October 12, 2016 Permalink | Reply
    Tags: , , , , New Object Vies for Kuiper Belt Record, Object 2014 UZ224, Sky & Telescope   

    From Sky & Telescope: “New Object Vies for Kuiper Belt Record” 

    SKY&Telescope bloc

    Sky & Telescope

    October 11, 2016
    Kelly Beatty

    1
    Based on observations over the past three years, astronomers know that the Kuiper Belt object known as 2014 UZ224 has a highly elliptical, 1,140-year-long orbit that stretches nearly four times farther from the Sun than Pluto can ever be. NASA / JPL / Horizons

    Kuiper Belt. Minor Planet Center
    Kuiper Belt. Minor Planet Center

    Right now 2014 UZ224 lies nearly 14 billion kilometers away, ranking it third among the most distant objects known in the Kuiper Belt.

    Early today the IAU’s Minor Planet Center announced that astronomers in Chile have discovered a Kuiper Belt object, designated 2014 UZ224, that’s currently 91.6 astronomical units from the Sun. This corresponds to 13.7 billion kilometers (8.5 billion miles), nearly three times farther out than Pluto is at the moment. Only two other known KBOs are more distant: Eris (96.2 a.u.) and V774104 (103 a.u.) to…[?]

    In fact, 2014 UZ224 is closer to the Sun than average right now and headed inbound. Its 1,140-year-long orbit is quite eccentric, swinging as close as 38 a.u. (think “Pluto’s orbit”) and as far away as 179.8 a.u. Technically, astronomers don’t consider it part of the classical Kuiper Belt but instead a “scattered disk object” whose orbits have been perturbed outward due to encounters with Neptune.

    A team led by David Gerdes (University of Michigan) first spotted this object in August 2014, and then several times again in 2015 and 2016, using the 4-m Victor Blanco reflector at Cerro Tololo Inter-American Observatory in Chile. Thanks to CTIO’s Dark Energy Camera, which Gerdes helped develop for the Dark Energy Survey (DES), 2014 UZ224 stood out clearly in images despite its apparent magnitude of only 23½.

    Dark Energy Icon
    Dark Energy Camera. Built at FNAL
    Dark Energy Camera. Built at FNAL
    NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile
    NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile

    “The same combination of survey area and depth that makes DES a state-of-the-art cosmological survey also makes it a great tool for making discoveries in our own cosmic backyard,” Gerdes explains. “Our search for trans-Neptunian objects is a serendipitous by-product of the survey data.” The effort has yielded dozens of Kuiper Belt objects so far, even though the team has examined only a fraction of the amassed observations. “I hope 2014 UZ224 is not the most interesting thing we eventually find!” Gerdes adds.

    For now, his team knows little more about their distant discovery other than its orbit and apparent brightness. Given its distance, however, the object should be sizable — anywhere from 400 km across (if its surface is bright and 50% reflective) to 1,200 km (if very dark and 5% reflective). If its true size edges toward the larger end of this range, then 2014 UZ224 would likely qualify for dwarf-planet status.

    Fortunately, we should have a much better estimate of the object’s size very soon. Gerdes has used the ALMA radio-telescope array to measure the heat radiating from 2014 UZ224, which can be combined with the optical measurements to yield its size and albedo.

    “The Blanco telescope is decades old, but DECam is a state-of-the-art instrument that has revitalized it in several ways,” Gerdes explains. “First, the focal plane is huge, so the telescope now has a 3°-square field of view. And second, the DECam’s CCDs are extremely sensitive in the red and near-infrared light, which makes it particularly good at detecting high-redshift objects.”

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    Sky & Telescope magazine, founded in 1941 by Charles A. Federer Jr. and Helen Spence Federer, has the largest, most experienced staff of any astronomy magazine in the world. Its editors are virtually all amateur or professional astronomers, and every one has built a telescope, written a book, done original research, developed a new product, or otherwise distinguished him or herself.

    Sky & Telescope magazine, now in its eighth decade, came about because of some happy accidents. Its earliest known ancestor was a four-page bulletin called The Amateur Astronomer, which was begun in 1929 by the Amateur Astronomers Association in New York City. Then, in 1935, the American Museum of Natural History opened its Hayden Planetarium and began to issue a monthly bulletin that became a full-size magazine called The Sky within a year. Under the editorship of Hans Christian Adamson, The Sky featured large illustrations and articles from astronomers all over the globe. It immediately absorbed The Amateur Astronomer.

    Despite initial success, by 1939 the planetarium found itself unable to continue financial support of The Sky. Charles A. Federer, who would become the dominant force behind Sky & Telescope, was then working as a lecturer at the planetarium. He was asked to take over publishing The Sky. Federer agreed and started an independent publishing corporation in New York.

    “Our first issue came out in January 1940,” he noted. “We dropped from 32 to 24 pages, used cheaper quality paper…but editorially we further defined the departments and tried to squeeze as much information as possible between the covers.” Federer was The Sky’s editor, and his wife, Helen, served as managing editor. In that January 1940 issue, they stated their goal: “We shall try to make the magazine meet the needs of amateur astronomy, so that amateur astronomers will come to regard it as essential to their pursuit, and professionals to consider it a worthwhile medium in which to bring their work before the public.”

     
  • richardmitnick 11:00 am on October 5, 2016 Permalink | Reply
    Tags: , , , Sky & Telescope   

    From Sky & Telescope: “Resolving Andromeda — How to See Stars 2.5 Million Light-Years Away” 

    SKY&Telescope bloc

    Sky & Telescope

    October 5, 2016
    Bob King

    1
    The Hubble Space Telescope easily resolves millions of individual stars in an outer region of the Andromeda Galaxy, also known as M31.
    NASA / ESA / Hubble Heritage Team

    I always figured I’d have to wait until the next supernova to see an individual star among the trillion that comprise the Andromeda Galaxy.

    At the galaxy’s distance of 2.5 million light-years, the stars blend into a luminous stellar fog. Whenever I show Andromeda to the public, I make sure to remind each viewer that the haze they see is actually the light of billions of individual stars too far and faint to resolve into individual pinpoints.

    In binoculars and small telescopes, it’s easy to distinguish the core, where stars are more strongly concentrated, from the less populated arms. Those with 10-inch and larger telescopes can survey the galaxy’s brighter globular star clusters and stellar associations with the aid of detailed maps. But individual stars?

    Several years back, I briefly observed a bright nova just outside the galaxy’s nucleus in my 15-inch reflector when it peaked around magnitude +14.9. That was a lucky break as most novae in M31 max out around magnitude +17-19 and require telescopes upwards of 20-inches to track down.

    2
    In this wide-field photo of the Andromeda Galaxy, the bright OB association NGC 206 resembles its visual appearance. The massive star cloud is located at the southwestern end of the galaxy’s disk at the junction of two spiral arms.
    Patrick Winkler / Online Photo Gallery

    Then one fall night, while hunting down globulars and other minute delights in the galaxy, I shifted the scope to NGC 206, M31’s largest and brightest star cloud. The object, which resembles a weakly condensed 10th-magnitude comet superimposed on Andromeda’s southwestern arm, measures 4.2′ across. Its true size is about 4,000 light-years across or nearly three times the distance from Earth to the star Deneb in the Northern Cross, making it one of the largest star clouds in the Local Group of galaxies.

    Local Group. Andrew Z. Colvin 3 March 2011
    Local Group. Andrew Z. Colvin 3 March 2011

    If you haven’t observed it yet, you’ve probably noticed this distinctive hazy patch in photos of Andromeda. NGC 206 also goes by the name OB 78 and resembles the vast Perseus OB 1 association which includes Mirfak, the brightest star in Perseus, and the popular Double Cluster.

    OB associations, named after the brilliant class O and B stars they contain, are loosely organized gaggles of young stars and star clusters born in the collapse of a giant molecular cloud. True star clusters, more compact by nature, keep hold of their stars through gravitational attraction. Thinly spread OB associations make easy prey for galactic tides, which pull associations apart and disperse their members far and wide.

    4
    This closeup of NGC 206 reveals a rich gathering of hot blue supergiant stars. The cloud is similar in size to the spectacular Tarantula Nebula in the Large Magellanic Cloud and NGC 604 in M33, the Pinwheel Galaxy. I’ve included a “triangle guide” here and in the sketch below to help you get oriented. North is up. Michael A. Siniscalchi

    NGC 206 is home to some 300 brilliant blue stars, the youngest of which are just 10 million years old, incredibly young by stellar standards. Stars 20 times more massive than the Sun are common with a few topping out at more than 40x solar! Inspired by these superlatives and photos that showed good resolution of the cloud, I cranked up the magnification to 242x and then 357x, allowed my eyes to fully adapt to the darkened field of view and got the surprise of my life. Stars!

    NGC 206 appeared in three sections: a tiny ~30″ wide knot dotted by a 16th magnitude star, a brighter, clumpy northern “cloud” and a fainter, more distended southern section separated by a relatively haze-free gap (in other words, no unresolved stars). Direct vision revealed several faint stellar points around and within the cluster, some of which were members of the association and not Milky Way foreground suns.

    5
    NGC 206 lies at the intersection of two of Andromeda’s spiral arms and was likely spawned in a collision of massive dust clouds at their intersection.
    Jim Misti

    But the thing that positively electrified the view was seeing OB 78 materialize into a rich spray of barely visible stars with averted vision. They came and went with the vagaries of my eye’s position and seeing conditions, but there was no question I was seeing cluster stars based on location and star density compared to the ambient Milky Way foreground. The scene reminded me of the grainy interiors of the remote globular clusters NGC 7006 in Delphinus and the “Intergalactic Wanderer,” NGC 2419, in Lynx.

    In all three cases, it was next to impossible to hold so many faint stars in view long enough to see them individually or connect them into patterns. Instead, they appeared as a granulated haze or mist of dim points that flashed in and out of view.

    Stephen Odewahn of the McDonald Observatory surveyed NGC 206 in the 1980s and published a photometric survey of its brightest stars. While most are hopelessly faint for visual observers even with moderately large telescopes, 14 members range between magnitude +14.8 and +17.5, making them somewhat less hopelessly faint.

    A 15-inch scope covers the brighter end of that range with ease, but the number of stars I glimpsed with averted vision implies that in some situations, based on seeing, magnification and experience, we can momentarily best a telescope’s limiting magnitude by a surprising margin.

    7
    This sketch of the NGC 206 star cloud was made primarily using a 15-inch telescope, but it’s also informed by a view through a 24-inch. A skinny triangle of stars just north of the cloud will help you get oriented. Brighter stars are labeled with B (blue) magnitudes with decimal points omitted. All the stars, with the exception of the 13.1, are listed as association members in Odewahn’s paper. The tiny stellar sprinkles are for illustration purposes and included to convey my impression when viewing the cloud. Bob King

    No one should be content with a single observation of faint nothings, so I re-observed the star cloud on several occasions and confirmed my observation using friends’ 18-inch and 24-inch telescopes. We invited several members of our clubs to view NGC 206 and every one of them was able to at least partially resolve the stellar association in each scope.

    Using a photo labeled with some of the brighter stars from Odewahn’s paper, I was able to clearly see and identify seven stars between magnitudes +14.8 and +15.8 in the 15-inch. I’ve included these in a drawing made using Photoshop that I hope will provide a useful tracking guide for your own explorations.

    While a 24-inch scope reveals even more stars, a 15-inch scope is easily up to the task of breaking out some of Andromeda’s brightest blue supergiant stars from this magnificent clutch of stellar celebrities. Daring amateurs may even want to put a 10 or 12-inch scope to the task. I’d love to know what you’ll see.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    Sky & Telescope magazine, founded in 1941 by Charles A. Federer Jr. and Helen Spence Federer, has the largest, most experienced staff of any astronomy magazine in the world. Its editors are virtually all amateur or professional astronomers, and every one has built a telescope, written a book, done original research, developed a new product, or otherwise distinguished him or herself.

    Sky & Telescope magazine, now in its eighth decade, came about because of some happy accidents. Its earliest known ancestor was a four-page bulletin called The Amateur Astronomer, which was begun in 1929 by the Amateur Astronomers Association in New York City. Then, in 1935, the American Museum of Natural History opened its Hayden Planetarium and began to issue a monthly bulletin that became a full-size magazine called The Sky within a year. Under the editorship of Hans Christian Adamson, The Sky featured large illustrations and articles from astronomers all over the globe. It immediately absorbed The Amateur Astronomer.

    Despite initial success, by 1939 the planetarium found itself unable to continue financial support of The Sky. Charles A. Federer, who would become the dominant force behind Sky & Telescope, was then working as a lecturer at the planetarium. He was asked to take over publishing The Sky. Federer agreed and started an independent publishing corporation in New York.

    “Our first issue came out in January 1940,” he noted. “We dropped from 32 to 24 pages, used cheaper quality paper…but editorially we further defined the departments and tried to squeeze as much information as possible between the covers.” Federer was The Sky’s editor, and his wife, Helen, served as managing editor. In that January 1940 issue, they stated their goal: “We shall try to make the magazine meet the needs of amateur astronomy, so that amateur astronomers will come to regard it as essential to their pursuit, and professionals to consider it a worthwhile medium in which to bring their work before the public.”

     
c
Compose new post
j
Next post/Next comment
k
Previous post/Previous comment
r
Reply
e
Edit
o
Show/Hide comments
t
Go to top
l
Go to login
h
Show/Hide help
shift + esc
Cancel
%d bloggers like this: