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June 9, 2019 at 7:02 am #9841Anonymous
THE SOCIETY FOR POPULAR ASTRONOMY
Electronic News Bulletin No. 491 2019 June 9
Here is the latest round-up of news from the Society for Popular Astronomy. The SPA is arguably Britain's liveliest astronomical society, with members all over the world. We accept subscription payments online at our secure site and can take credit and debit cards. You can join or renew via a secure server or just see how much we have to offer by visiting http://www.popastro.com/
HUGE BLUE CLOUD CIRCLES THE NORTH POLE
A huge blue cloud of frosted meteor smoke is pinwheeling around the Arctic Circle. NASA's AIM spacecraft observed its formation on May 20, and it has since circled the North Pole one and a half times, expanding in size more than 200-fold. Noctilucent clouds (NLCs) in May are nothing unusual. They form every year around this time when the first wisps of summertime
water vapour rise to the top of Earth's atmosphere. Molecules of H2O adhere to specks of meteor smoke, forming ice crystals 80 km above Earth's surface. When sunbeams hit those crystals, they glow electric-blue. But these NLCs are different. They are unusually strong and congregated in a coherent spinning mass, instead of spreading as usual all across the polar cap. This is most likely a sign of planetary wave activity. Planetary waves are enormous ripples of temperature and pressure that form in the Earth's atmosphere in response to Coriolis forces. They are responsible in part for undulations in the jet stream and can have a major influence on global weather. All rotating planets with atmospheres have such waves. Data from
NASA's Microwave Limb Sounder (MLS) instruments show that, indeed, a planetary wave is circling the North Pole in sync with the blue cloud. The region of coldest temperatures migrates clockwise around the hemisphere, making one complete lap in about 5 days. This is where the NLCs are forming.
Because of planetary wave activity, the 2019 season is shaping up to be unusually good. The clouds have already made an appearance in the USA — something that usually doesn't happen until late June or July. NLCs have also been sighted in Europe — highlighted by a bright display in Germany. If the 2019 NLC season continues to develop so quickly, even mid-latitude observers may soon be seeing this polar phenomenon. Observing tip: look west 30 to 60 minutes after sunset; if you see luminous blue-white tendrils spreading across the sky, you may have observed a noctilucent cloud.
MARS ROVER FINDS CLAY CACHE
The Curiosity rover has confirmed that the region on Mars it's exploring, called the “clay-bearing unit” is well deserving its name. Two samples the rover recently drilled at rock targets called 'Aberlady' and 'Kilmarie' have revealed the highest amounts of clay minerals ever found during the mission. Both drill targets appear in a new selfie taken by the rover on 2019 May 12, the 2,405th Martian day, or sol, of the mission. The clay- enriched region, located on the side of lower Mount Sharp, stood out to NASA orbiters before Curiosity landed in 2012. Clay often forms in water, which is essential for life; Curiosity is exploring Mount Sharp to see if it had the conditions to support life billions of years ago. The rover's mineralogy instrument, called CheMin (Chemistry and Mineralogy), provided the first analyses of rock samples drilled in the clay-bearing unit. CheMin also found very little haematite, an iron-oxide mineral that was abundant just to the north, on Vera Rubin Ridge. Other than proof that there was a significant amount of water once in Gale Crater, what these new findings mean for the region is still up for debate. It is likely that the rocks in the area formed as layers of mud in ancient lakes — something Curiosity also found lower on Mount Sharp. Water interacted with sediment over time, leaving an abundance of clay in the rocks there.
ULTRA-SMALL MICROBES SURVIVE IN MARS-LIKE ENVIRONMENT
The first study of ultra-small bacteria living in the extreme environment of Ethiopia's Dallol hot springs shows that life can thrive in conditions similar to those thought to have been found on the young planet Mars. An international team of researchers has found a strain of the Nanohalo-archaeles Order bacteria embedded in samples taken from a salt chimney
deposited by supersaturated water at temperatures of 89 degrees Celsius and at the extremely acidic pH of 0.25. The samples were collected during a field trip to the Dallol volcano and the Danakil Depression in northern Ethiopia in January 2017. Precipitation by superheated water saturated with various salts, including silver chloride, zinc iron sulphide, manganese dioxide and normal rock-salt, creates Dallol's technicoloured landscape of
yellows, reds, greens and blues. The team collected samples of the thin layers of salt deposits from the wall of a yellow chimney stack and a blue pool of water surrounding the outcrop. The samples were transported in sterile, sealed vials to state-of-the-art facilities in Spain, where they were analysed using a range of techniques, including electron microscopy, chemical analysis and DNA sequencing. The team identified tiny, spherical structures within the salt samples that had a high carbon content, demonstrating an unambiguously biological origin. The microorganisms are 50-500 nanometres in diameter — up to 20 times smaller than average bacteria. In several cases, the microorganisms are surrounded by needle-shaped crystals, which suggests that the nanobacteria may play an active role in the salt deposits and the geochemical cycle at Dallol. The Dallol volcano and geothermal area is one of the hottest places on Earth, with average annual temperatures of 36 to 38 degrees Celsius. It is located at the northern end of the Danakil Depression, which lies around 125m below sea level at the junction of three of the Earth's lithospheric plates (Arabian, Nubian and Somalian) that are moving apart. Hydrothermal activity is fuelled by water that has been heated and enriched in gases by a shallow magma reservoir beneath the volcano. Dallol is surrounded by the
wide Assale salt plain. The interaction between evaporated deposits and vulcanism creates a unique and complex physical and chemical environment. The unusual geochemistry of Dallol has close parallels to hydrothermal environments found on Mars, including the Gusev Crater, where NASA's Spirit Mars Exploration Rover landed.
MASSIVE MARTIAN ICE DISCOVERY
University of Texas at Austin
Newly discovered layers of ice buried a mile beneath Mars' north pole are the remnants of ancient polar ice sheets and could be one of the largest water reservoirs on the planet. The team made the discovery using measurements gathered by the Shallow Radar (SHARAD) on NASA's Mars Reconnaissance Orbiter (MRO). SHARAD emits radar waves that can penetrate up to a mile and a half beneath the surface of Mars. The findings are important because the layers of ice are a record of past climate on Mars in much the same way that
tree rings are a record of past climate on Earth. Studying the geometry and composition of these layers could tell scientists whether climate conditions were previously favourable for life. The team found layers of sand and ice that were as much as 90% water in some places. If melted, the newly discovered polar ice would be equivalent to a global layer of water around
Mars at least 1.5 metres deep. The authors think that the layers formed when ice accumulated at the poles during past ice ages on Mars. Each time the planet warmed, a remnant of the ice caps became covered by sand, which protected the ice from solar radiation and prevented it from dissipating into the atmosphere. Scientists have long known about glacial events on Mars, which are driven by variations in the planet's orbit and tilt. Over periods of about 50,000 years, Mars leans toward the Sun before gradually returning to an upright position, like a wobbling spinning top. When the planet spins upright, the equator faces the Sun, allowing the polar ice caps to grow. As the planet tilts, the ice caps retreat, perhaps vanishing entirely. Until now, scientists thought that the ancient ice caps were lost. The paper shows that in fact significant ice sheet remnants have survived under the planet's surface, trapped in alternating bands of ice and sand, like layers in a cake.
NEPTUNE'S MOON FOSTERS RARE ICY UNION
Astronomers using the Gemini Observatory have explored Neptune's largest moon Triton and observe, for the first time beyond the lab, an extraordinary union between carbon monoxide and nitrogen ices. The discovery offers insights into how this volatile mixture can transport material across the moon's surface via geysers, trigger seasonal atmospheric changes, and
provide a context for conditions on other distant, icy worlds. Extreme conditions can produce extreme results. In this case, it's the uncommon pairing of two common molecules — carbon monoxide (CO) and nitrogen (N2) — frozen as solid ices on Neptune's frigid moon Triton. In the laboratory, an international team of scientists has pinpointed a very specific wavelength
of infrared light absorbed when carbon monoxide and nitrogen molecules join together and vibrate in unison. Individually, carbon monoxide and nitrogen ices each absorb their own distinct wavelengths of infrared light, but the tandem vibration of an ice mixture absorbs at an additional, distinct wavelength identified in this study. Using the 8-metre Gemini South Telescope in Chile, the team has recorded this same unique infrared signature on Triton. Key to the discovery was the high-resolution spectrograph called IGRINS (Immersion Grating Infrared Spectrometer). In the Earth's atmosphere carbon monoxide and nitrogen molecules exist as gases, not ices. In fact, molecular nitrogen is the dominant gas in the air
we breathe, and carbon monoxide is a rare contaminant that can be lethal.
On distant Triton, however, carbon monoxide and nitrogen freeze to solid ices. They can form their own independent ices, or can condense together in the icy mix detected in the Gemini data. That icy mix could be involved in Triton's iconic geysers first seen in Voyager 2 spacecraft images as dark, windblown streaks on the surface of the distant, icy moon. The Voyager 2 spacecraft first captured Triton's geysers in action in the moon's south-polar region in 1989. Since then, theories have focused on an internal ocean as one possible source of erupted material. Or the geysers may erupt when the summertime Sun heats this thin layer of volatile ice on Triton's surface, potentially involving the mixed carbon monoxide and nitrogen ice revealed by the Gemini observation. That ice mixture could also migrate around the surface of Triton in response to seasonally varying patterns of sunlight. Seasons progress slowly on Triton, as Neptune takes 165 Earth years to orbit the Sun. A season on Triton lasts a little over 40 years; Triton passed its southern summer solstice mark in 2000, leaving about 20
more years to conduct further research before its autumn begins. Looking ahead, the researchers expect that these findings will shed light on the composition of ices and seasonal variations in the atmosphere on other distant worlds beyond Neptune. Astronomers have suspected that the mixing of carbon monoxide and nitrogen ice exists not only on Triton, but also on Pluto, where the New Horizons spacecraft found the two ices coexisting. This Gemini finding is the first direct spectroscopic evidence of these ices mixing and absorbing this type of light on either world.
STELLAR WALTZ WITH DRAMATIC ENDING
University of Bonn
Astronomers have identified an unusual celestial object. It is most likely the product of the fusion of two stars that died a long time ago. After billions of years circling around one another these so-called white dwarfs merged and rose from the dead. In the near future, their lives could finally end — with a huge bang. The extremely rare merger product was discovered by scientists studying images made by the Wide-field Infrared Survey Explorer (WISE) satellite: they found a gas nebula with a bright star in its centre. Surprisingly, however, the nebula emitted almost exclusively infrared radiation and no visible light. The spectrum of the radiation
emitted by the nebula and its central star was analyzed. In that way, researchers were able to show that the enigmatic celestial object contained neither hydrogen nor helium — a characteristic typical for the interiors of white dwarfs. Stars like our Sun generate their energy through hydrogen burning, the nuclear fusion of hydrogen. When the hydrogen is consumed,
they continue burning helium. However, they cannot fuse even heavier elements — their mass is insufficient to produce the necessary high temperatures. Once all helium is used up, they cease burning and cool down turning into white dwarfs. Usually their life is over at this point. But not for J005311 — this is how the scientists named their new find in the constellation Cassiopeia, 10,000 light-years from Earth. Scientists assume that two white dwarfs formed there in close proximity many billions of years ago. They circled around each other, creating exotic distortions of space-time, called gravitational waves. In the process, they gradually lost
energy. In return, the distance between them shrank more and more until they finally merged. Now their total mass was sufficient to fuse heavier elements than hydrogen or helium. The stellar furnace started burning again. Such an event is extremely rare. There are probably not even half a dozen such objects in the Milky Way.
Nevertheless, the researchers are convinced that they are right with their interpretation. For one thing, the star in the centre of the nebula shines 40,000 times as brightly as the Sun, far brighter than a single white dwarf could. In addition, the spectra indicate that J005311 has an extremely strong stellar wind — this is the stream of material that emanates from the stellar surface. Its engine is the radiation generated during the burning process. But at a speed of 16,000 km/s, the wind of J005311 is so fast that that factor alone is not enough to explain it. However, merged white dwarfs are expected to have a very strong rotating magnetic field. Simulations show that the field acts like a turbine, which additionally accelerates the
stellar wind. Sadly, the resurgence of J005311 will not last long. In only a few thousand years the star will have transformed all elements into iron and fade again. As its mass has increased to more than 1.4 times the mass of the Sun in the merger process, it will suffer an exceptional fate. The star will collapse under the influence of its own gravity. At the same time, the electrons and protons building up its matter will fuse into neutrons. The resulting neutron star has only a fraction of its previous size, measuring only few kilometres in diameter, while its mass is more than the entire solar system. J005311, however, won't leave without a final salute. Its collapse will be accompanied by a supernova explosion.
SUBARU TELESCOPE FINDS 1800 SUPERNOVAE
Kavli Institute for the Physics and Mathematics of the Universe
By combining one of the world's most powerful digital cameras and a telescope capable of capturing a wider shot of the night sky compared to other big telescopes, researchers have been able to identify about 1800 new supernovae, including 58 Type Ia supernovae 8 billion light years away. A supernova is an exploding star that has reached the end of its life. The
star often becomes as bright as its host galaxy, shining a billion times brighter than the Sun for any time between a month to six months before dimming down. Supernovae classed as Type Ia are useful because their uniform maximum brightness allows researchers to calculate how far the star is from the Earth. That is particularly useful for researchers who want to measure the expansion of the Universe. In recent years, researchers began reporting a new type of supernova five to ten times brighter than Type Ia, called Super Luminous Supernovae. Many astronomers have been trying to learn more about these stars. Their unusual brightness enables researchers to locate them in the farthest parts of the Universe. Since distant
Universe means the early Universe, studying this kind of star could reveal characteristics about the first, massive stars created after the Big Bang.
But supernovae are rare events, and there are only a handful of telescopes in the world capable of capturing sharp images of distant stars. In order to maximize the chances of observing a supernova, astronomers used the Subaru Telescope, which is capable of generating sharp stellar images; and the Hyper Suprime-Cam, an 870-mega-pixel digital camera attached to it, captures a very wide area of the night sky in one shot. By taking repeated images of the same area of night sky over a six-month period, the researchers could identify new supernovae by looking for stars that suddenly appeared brighter before gradually fading out. As a result, the team identified 5 super-luminous supernovae, and about 400 Type Ia supernovae. Fifty-eight of the Type Ia supernovae were located more than 8 billion
light-years away. In comparison, it took researchers using the Hubble Space Telescope about 10 years to discover a total of 50 supernovae located more than 8 billion light-years away. The next step will be to use the data to calculate a more accurate expansion of the Universe, and to study how dark energy has changed over time.
NAMES INVITED TO FLY TO MARS
Members of the public who want to send their names to Mars on NASA's next rover mission to it (Mars 2020) can get a souvenir boarding pass and their names etched on microchips to be affixed to the rover. The rover is scheduled to launch as early as July 2020, with the spacecraft expected to touch down on Mars in February 2021. The rover, weighing more than 1,000 kilograms, will search for signs of past microbial life, characterize the planet's climate and geology, collect samples for future return to Earth, and pave the way for human exploration of Mars. The opportunity to send your name to Mars comes with a souvenir boarding pass and 'frequent flyer' points. This is part of a public engagement campaign to highlight missions involved with NASA's journey from the Moon to Mars. More than 2 million
names flew on NASA's InSight mission to Mars, giving each 'flyer' about 300 million frequent-flyer miles. From now until Sept. 30, you can add your name to the list and obtain a souvenir boarding pass to Mars at https://go.nasa.gov/Mars2020Pass NASA will use Mars 2020 and other missions to prepare for human exploration of the Red Planet. As another step toward that goal, NASA is returning American astronauts to the Moon in 2024. Government, industry and international partners will join NASA in a global effort to build and test the systems needed for human missions to Mars and beyond.
Bulletin compiled by Clive Down
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