Astronomy Now is the UK’s biggest astronomy magazine, with 132 feature-packed pages. Since 1987 it has been essential reading for astronomers in the UK and around the world. Each month, the magazine contains features, reviews, news and practical guides on all aspects of astronomy.
A simulation of the view to the east-northeast as seen from the heart of the British Isles at 12am local time on Sunday 22 April. For scale, the portion of sky depicted is about three times the span of an outstretched hand at arm’s length wide. Although predictions place this year’s maximum during daylight for observers in Western Europe, weekend early risers in rural areas could be in for a treat as the Lyrid shower is known for fireballs and bright meteors leaving glowing trails. AN graphic by Ade Ashford.If skies are clear between midnight and the first glimmer of dawn this weekend, you may get to see some celestial fireworks from the Lyrid meteor shower. While it may not be the richest of the annual shooting star displays, the Lyrids can deliver a few fireballs and a portion of these medium-speed meteors can leave glowing trains.
Cometary particles strewn along the orbit of long-period Comet C/1861 G1 (Thatcher) are the genesis of the Lyrid meteors. Those meteoroids entering the Earth’s atmosphere do so at velocities up to 30 miles (48 kilometres) per second, hence it’s not surprising that the streak of light marking their heated demise can be so impressive.
Active from 14–30 April, the International Meteor Organisation predicts the peak of this year’s shower to occur around 18h UT (7pm BST) on Sunday 22 April, which would favour East Africa, the Middle East, India, China, Southeast Asia and Australia. However, the time of the peak is variable from year to year, so the maximum could lie between 10h and 21h UT (11am to 10pm BST).
Even if the predicted peak of the Lyrids occurs in daylight for Western Europe (including the UK), observers looking in the eastern sky after midnight this weekend can expect around a dozen meteors per hour under favourable conditions – particularly if you start your vigil after the waxing Moon sets. (The 5-day-old lunar crescent sets around 1:40am BST on Saturday 21 April for the centre of the UK, and an hour later Sunday morning.)
It follows that the best views are reserved for those dedicated souls prepared to observe in the small hours between moonset and the first light of dawn around 4am BST in the UK when the radiant of the Lyrids is high in the southeast.
As is typical of most meteor showers, fainter Lyrids are the most plentiful, so your chances of observing some are greatly improved if you can find a safe, rural location well away from artificial lights and take 20 minutes or more to ensure that your eyes are fully dark adapted.
New computer models indicate Mars’ moons Phobos and Deimos likely formed in the wake of an impact by a body the size of the dwarf worlds Ceres or Vesta, not a much larger body as previously theorized. The modeling indicates more distant debris eventually formed Phobos and Deimos while larger moons closer in later crashed into the red planet. Image: Southwest Research Institute
Astronomers have long debated the origins of Mars’ two moons, Phobos and Deimos, arguing they may be captured asteroids or the end result of an ancient ring of debris blasted into space by an impactor. The moons certainly resemble asteroids, but their nearly circular, co-planar orbits are consistent with their formation from an equatorial disk of debris.
Now, scientists at the Southwest Research Institute in San Antonio, Texas, using sophisticated hydrodynamical simulations, have concluded the moons likely resulted from the impact of a body the size of the dwarf worlds Vesta or Ceres rather than a much larger body as many had speculated earlier.
“A key result of the new work is the size of the impactor; we find that a large impactor, similar in size to the largest asteroids Vesta and Ceres, is needed, rather than a giant impactor,” lead author Dr. Robin Canup, an associate vice president in the Southwest Research Institute’s Space Science and Engineering Division, said in a statement.
“The model also predicts that the two moons are derived primarily from material originating in Mars, so their bulk compositions should be similar to that of Mars for most elements,” he added. “However, heating of the ejecta and the low escape velocity from Mars suggests that water vapour would have been lost, implying that the moons will be dry if they formed by impact.””
Earth’s Moon, with a diameter of a bit more than 2,100 miles, may be the result of an impact with a Mars-size body shortly after the birth of the solar system 4.5 billion years ago, blasting out a thick ring of debris that eventually coalesced to form a large satellite. Phobos and Deimos are much smaller – 14 and 7.5 miles wide respectively – and orbit much closer to their parent.
“We used state-of-the-art models to show that a Vesta-to-Ceres-sized impactor can produce a disk consistent with the formation of Mars’ small moons,” said Julien Salmon, an SwRI research scientist. “The outer portions of the disk accumulate into Phobos and Deimos, while the inner portions of the disk accumulate into larger moons that eventually spiral inward and are assimilated into Mars.”
The model indicates that larger impactors would result in more massive inner moons that would prevent the survival of much smaller satellites like Phobos and Deimos.
Marking the Hubble Space Telescope’s 28th anniversary in orbit, the observatory peered into the heart of the Lagoon Nebula, a favourite target for amateur astronomers, generating this spectacular view of a vast, chaotic stellar nursery some 4,000 light-years away. At the centre of the photo is a giant star 200,000 times brighter, and 32 times more massive, than the sun, blasting out powerful stellar winds and torrents of ultraviolet radiation.
The Hubble Space Telescope captured a spectacular view of the Lagoon Nebula to mark the observatory’s 28th anniversary. Image: NASA
“This region epitomises a typical, raucous stellar nursery full of birth and destruction,” NASA said in a photo release. “The clouds may look majestic and peaceful, but they are in a constant state of flux from the star’s torrent of searing radiation and high-speed particles from stellar winds. As the monster star throws off its natal cocoon of material with its powerful energy, it is suppressing star formation around it.”
But star formation is proceeding in dense clouds of gas and dust at the “dark edges of this dynamic bubble-shaped ecosystem,” the release says.
“Dark, elephant-like “trunks” of material represent dense pieces of the cocoon that are resistant to erosion by the searing ultraviolet light and serve as incubators for fledgling stars. They are analogous to desert buttes that resist weather erosion.”
Observers in the UK with a clear sky at dusk should try to locate Venus low in the western sky an hour after sunset. The 3-day-old slim crescent Moon acts as a convenient guide, located some 12½ degrees (or half the span of an outstretched hand at arm’s length) to the upper left of the brightest planet. Conspicuous star Aldebaran lies in the same low-power binocular field of view as the Moon too. AN graphic by Ade Ashford.Observers in Western Europe should make the most of fine weather to locate Venus low in the western sky an hour after sunset, particularly on Wednesday 18 April when the 3-day-old slim crescent Moon acts as a convenient guide, located some 12½ degrees (or half the span of an outstretched hand at arm’s length) to the upper left of the brightest planet.
Stargazers in the British Isles with a clear sky around 10pm this evening should note the Pleiades (Seven Sisters) forming a right-angled triangle with Venus and the Moon in the deepening twilight, but don’t leave it much later as the brightest planet sets around 10:43pm as seen from the heart of the UK (stated times are in BST).
Prominent first-magnitude star Aldebaran lies in the same low-power binocular field of view as the Moon too. In the small hours of 19 April, the waxing lunar crescent actually occults (passes in front of) Aldebaran as seen from central and northern Russia, north and eastern Scandinavia, the north of Greenland and northernmost Canada.
The DARKNESS camera, being developed to directly image exoplanets orbiting nearby stars. It is being billed as “the world’s largest and most advanced superconducting camera.” Image: UC Santa Barbara
University of California-Santa Barbara physicist Benjamin Mazin is leading an international team developing what they say is the world’s largest, most sophisticated superconducting camera in a bid to directly image exoplanets orbiting nearby stars.
While NASA is famed for the occasional convoluted acronym, the camera team came up with its own prize winner: DARKNESS, which stands for “DARK-speckle Near-infrared Energy-resolved Superconducting Spectrophotometer.”
“It is the first 10,000-pixel integral field spectrograph designed to overcome the limitations of traditional semiconductor detectors,” UC Santa Barbara said in a release. “It employs Microwave Kinetic Inductance Detectors that, in conjunction with a large telescope and an adaptive optics system, enable direct imaging of planets around nearby stars.”
The DARKNESS camera can take thousands of images per second without the “read noise” and other factors that affect more traditional cameras. It also can determine the wavelength and arrival time of every photon striking its detector.
“This technology will lower the contrast floor so that we can detect fainter planets,” Mazin said in the UC Santa Barbara release. “Mazin explained. “We hope to approach the photon noise limit … allowing us to see planets 100 million times fainter than the star. At those contrast levels, we can see some planets in reflected light, which opens up a whole new domain of planets to explore.
“The really exciting thing is that this is a technology pathfinder for the next generation of telescopes,” he said.
The DARKNESS camera has completed four observing runs with the 200-inch Hale Telescope at the Palomar Observatory in California, operating as a science camera and a wave-front sensor providing feedback to a deformable mirror that works to counteract the effects of atmospheric turbulence. Another test run is expected in May.
“Our hope is that one day we will be able to build an instrument for the Thirty Meter Telescope planned for Mauna Kea on the island of Hawaii or La Palma,” Mazin said. “With that, we’ll be able to take pictures of planets in the habitable zones of nearby low-mass stars and look for life in their atmospheres. That’s the long-term goal, and this is an important step toward that.”
DARKNESS is funded by the U.S. National Science Foundation. Mazin’s team includes Dimitri Mawet of the California Institute of Technology and Eugene Serabyn of the Jet Propulsion Laboratory in Pasadena, California. Their work is described in Publications of the Astronomical Society of the Pacific.
This composite image from the Hubble Space Telescope’s Advanced Camera for Surveys and its Wide Field Camera 3 shows a huge cluster of galaxies some six billion light years away known as PSZ23 G138.61-10.84. The image is from an observing programme called the Reionization Lensing Cluster Survey, or RELICS. The RELICS project has studied 41 galaxy clusters to help locate the brightest distant galaxies for follow-on observations by the James Webb Space Telescope, scheduled for launch in 2020.
A galaxy cluster seen by the Hubble Space Telescope at a distance of about six billion lightyears. Image: ESA/Hubble & NASA, RELICS
Infrared maps of Jupiter’s stormy north polar region reveal a tapestry of interacting cyclones. Image: NASA/Juno
NASA has released an infrared movie of Jupiter’s north polar region as imaged by the orbiting Juno spacecraft’s Jovian InfraRed Auroral Mapper, or JIRAM, showing a huge cyclone over the north pole surrounded by eight smaller storms ranging up to 4,600 kilometres (2,900 miles) across.
JIRAM can measure temperatures 50 to 70 kilometres (30 to 45 miles) below Jupiter’s visible cloud tops, providing new insights into how the storms are powered. Yellow areas are deeper in the atmosphere and warmer while darker areas are colder and higher. Temperatures range from between -13 degrees and -83 degrees Celsius.
“Before Juno, we could only guess what Jupiter’s poles would look like,” said Alberto Adriani, Juno co-investigator from the Institute for Space Astrophysics and Planetology in Rome. “Now, with Juno flying over the poles at a close distance it permits the collection of infrared imagery on Jupiter’s polar weather patterns and its massive cyclones in unprecedented spatial resolution.”
Low 3-D Flyover of Jupiter’s North Pole in Infrared - YouTube
During the European Geosciences Union General Assembly in Vienna, Austria, Juno researchers also shared new results shedding light on how the giant planet’s interior rotates.
“Thanks to the amazing increase in accuracy brought by Juno’s gravity data, we have essentially solved the issue of how Jupiter’s interior,” said Tristan Guillot, a Juno co-investigator from the Université Côte d’Azur, Nice, France. “The zones and belts that we see in the atmosphere rotating at different speeds extend to about 3,000 kilometres (1,900 miles).
“At this point, hydrogen becomes conductive enough to be dragged into near-uniform rotation by the planet’s powerful magnetic field,” he said.
Juno researchers also unveiled a new model of Jupiter’s magnetic field based on data collected during the spacecraft’s first eight orbits.
Jupiter’s Dynamo - YouTube
The map shows unexpected irregularities, with more magnetic activity apparent in Jupiter’s northern hemisphere than in the southern. Halfway between the planet’s equator and north pole is an area where the magnetic field is very powerful and positive (seen in red), flanked by areas with less intensity and a negative orientation (blue). In the southern hemisphere, the researchers said, the magnetic field is consistently negative.
Jupiter is generally thought of as a more or less fluid body and it’s not yet known why such differences might be expected.
“We’re finding that Jupiter’s magnetic field is unlike anything previously imagined,” said Jack Connerney, Juno’s deputy principal investigator. “Juno’s investigations of the magnetic environment at Jupiter represent the beginning of a new era in the studies of planetary dynamos.”
NASA’s Juno spacecraft, currently orbiting Jupiter, routinely captures stunning views of the giant planet’s turbulent atmosphere, providing a treasure-trove of data for researchers and citizen-scientists like Seán Doran, who carries out sophisticated processing of raw imagery from the spacecraft’s JunoCam public-outreach camera. This view captures Jupiter’s Great Red Spot during Juno’s seventh low-altitude pass.
Jupiter’s Great Red Spot, taken by the public outreach camera aboard NASA’s Juno probe, as processed by graphic artist Seán Doran.
Supercomputer simulations show dense star clusters may host multiple generations of black hole mergers in which two coalesce to form a single, more massive hole followed by another merger, and another. Image: Northwestern Visualization/Carl Rodriguez
Supercomputer simulations that include relativistic effects indicate dense star swarms like the globular clusters that many, if not all, galaxies host likely serve as breeding grounds for successive generations of black hole mergers, resulting in more massive bodies than expected in the coalescence of two first generation holes.
“We think these clusters formed with hundreds to thousands of black holes that rapidly sank down in the centre,” Carl Rodriguez, an astrophysicist at the Massachusetts Institute of Technology and the Kavli Institute for Astrophysics and Space Research, said in a statement.
“These kinds of clusters are essentially factories for black hole binaries, where you’ve got so many black holes hanging out in a small region of space that two black holes could merge and produce a more massive black hole. Then that new black hole can find another companion and merge again.”
The Laser Interferometer Gravitational-Wave Observatory – LIGO – first detected gravitational waves from a binary black hole merger in 2015. If LIGO detects a binary black hole component with a mass greater than about 50 times that of the sun, the computer simulations carried out by Rodriquez and his team show it likely would originate in a dense stellar cluster as a result of multiple prior mergers.
“If we wait long enough, then eventually LIGO will see something that could only have come from these star clusters, because it would be bigger than anything you could get from a single star,” Rodriguez said.
Rodriquez and his team used a supercomputer at Northwestern University to simulate interactions within two dozen clusters containing between 200,000 and two million stars with a range of densities and compositions. The simulation modelled stellar evolution and gravitational interactions across 12 billion years, leading to the formation of black holes. The computer also modelled the trajectories of the holes.
“The neat thing is, because black holes are the most massive objects in these clusters, they sink to the centre, where you get a high enough density of black holes to form binaries,” Rodriguez says. “Binary black holes are basically like giant targets hanging out in the cluster, and as you throw other black holes or stars at them, they undergo these crazy chaotic encounters.”
Earlier studies based on Newtonian mechanics, which did not take into account gravitational waves, indicated black holes would seldom interact unless in very close proximity.
But taking relativistic effects into account, along with data from LIGO observations, Rodriquez and his colleagues found that about 20 percent of binary black holes in dense star clusters included at least one member formed in a previous merger. Some of those should have masses in the range of 50 to 130 times that of the sun – more than could be expected from a single star.
“My co-authors and I have a bet against a couple people studying binary star formation that within the first 100 LIGO detections, LIGO will detect something within this upper mass gap,” Rodriguez said. “I get a nice bottle of wine if that happens to be true.”
About 1 millimetre square, a superconducting quantum interference device, or SQUID, may be able to detect telltale photons from axions, a leading dark matter candidate. Image: Sean O’Kelley
A quantum amplifier, operating at a tiny fraction of a degree above absolute zero, has demonstrated the sensitivity needed to detect microwave-frequency photons that theorists believe may be coaxed from axions, a leading dark matter candidate.
Researchers at the University of California at Berkeley, led by physicist John Clarke, successfully adapted superconducting quantum interference devices, or SQUIDs, for use in the Axion Dark Matter Experiment funded by the U.S. Department of Energy through the University of Washington.
The ADMX device uses a powerful magnetic field and a specially tuned reflective box “to encourage axions to convert to microwave-frequency photons, and uses the quantum amplifier to ‘listen’ for them,” according to a UC Berkeley press release. “All this is done at the lowest possible temperature to reduce background noise.”
ADMX operations manager Andrew Sonnenschein at the Fermi National Accelerator Laboratory in Batavia, Illinois, said the new detector “signals the start of the true hunt for axions.”
“If dark matter axions exist within the frequency band we will be probing for the next few years, then it’s only a matter of time before we find them,” he said.
Listening for Dark Matter with ADMX - YouTube
Dark matter is believed to make up 84 percent of the matter in the universe. Its gravitational effects on stars and galaxies can be seen, but the particles interact so rarely with normal matter that none have been directly detected.
Scientists have spent decades looking for theorised candidates – massive compact halo objects, or MACHOs, and weakly interacting massive particles, or WIMPS, for example – but nothing has been observed. Axions are yet another leading candidate, one that would solve a variety of theoretical problems should they, in fact, exist.
The new Microstrip SQUID Amplifier is the first device that, when cooled to just above absolute zero, has the sensitivity needed to detect the telltale microwave photons that would announce the presence of axions.
“This result plants a flag,” said Leslie Rosenberg, chief scientist for ADMX at the University of Washington. “It tells the world that we have the sensitivity, and have a very good shot at finding the axion. No new technology is needed. We don’t need a miracle anymore, we just need the time.”
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