Sorry, I seem to have forgotten to post this one!
EARTH AND MOON MAY BE 60 MILLION YEARS OLDER
University of Lorraine
New research indicates that the Earth and Moon are 60 million years older than previously estimated. That is, the violent collision believed to have created the Moon and gave the Earth its current form occurred just 40 million years after the Solar System formed some 4.5 billion years ago. Previous estimates had the Earth and the Moon forming 100 million years after the Solar System's formation. To arrive at their new estimate, researchers analyzed xenon gas found in quartz from South Africa and Australia -- samples that the scientists likened to 'time capsules' since they provide a glimpse of the Earth's distant past. They acknowledged that it is not possible to give an exact date for the formation of the Earth and that the 60-million-year figure may be off by as much as 20 million years.
TITAN HAS VERY SALTY OCEAN
NASA
Scientists believe that they have firm evidence that, beneath the crust of Titan, Saturn's largest moon, there is an ocean which may be as salty as the Earth's Dead Sea. The new results come from a study of gravity and topographic data collected during Cassini's repeated fly-bys of Titan during the past ten years. Researchers found that a relatively high density was required for Titan's sub-surface ocean in order to explain the gravity data. That indicates that the ocean is probably an extremely salty brine of water mixed with dissolved salts probably composed of sulphur, sodium and potassium. The density indicated for the brine would give the ocean a salt content roughly equal to the saltiest bodies of water on Earth. The findings also support the idea that the moon's icy shell is rigid and in the process of freezing solid. The thickness of Titan's ice crust appears to vary slightly from place to place. The researchers said that that can best be explained if the moon's outer shell is stiff, as would be the case if the ocean were slowly freezing and turning to ice. Otherwise, the moon's shape would tend to even itself out over time. The freezing process would have important implications for the habitability of Titan's ocean, as it would limit the ability of materials to exchange between the surface and the ocean.
The data also touch on the problem posed by the presence of methane in Titan's atmosphere. Scientists have long known that the atmosphere contains methane, ethane, acetylene and many other hydrocarbon compounds. But sunlight irreversibly destroys methane in tens of millions of years, so something must have replenished the methane in Titan's thick air during the moon's 4.5-billion-year history. The rigid-ice-shell model published in the journal Icarus suggests that any outgassing of methane into Titan's atmosphere must happen at scattered 'hot spots' (like the hot spot on the Earth that gave rise to the Hawaiian Island chain), not from a broader process such as convection or plate tectonics.
NEW HORIZONS TO STUDY KUIPER-BELT OBJECTS
Space Telescope Science Institute (STScI)
The Hubble telescope has been given the task of conducting an intensive search for a suitable outer-Solar-System object that the New Horizons spacecraft could visit after the probe streaks through the Pluto system next July. Hubble's Pluto observations will begin in July and are expected to finish in August. Provided a suitable target is found by the Hubble survey, and some follow-up observations are made later in the year, then if NASA approves, the New Horizons trajectory can be modified in autumn 2015 to meet the target Kuiper-Belt object (KBO) three or four years later. The Kuiper Belt is a debris field of icy bodies left over from the Solar System's formation 4.5 billion years ago. Though the belt was hypothesized in a 1951 paper by astronomer Gerard Kuiper, no Kuiper-Belt objects (apart from Pluto) were found until the early 1990s. So far over 1,000 of them have been catalogued, though many more must exist.
After a swift and intensive analysis of approximately 200 Hubble images, the New Horizons team met the pilot-programme criterion of finding a minimum of two KBOs. It will be many weeks before the team can establish whether either of them is a suitable target for New Horizons to visit, but the discovery provides sufficient evidence to encourage a wider search to be made with Hubble to find an optimum object.
DISCOVERY OF EXOTIC SUPERNOVA
RAS
Early images taken by the Dark Energy Survey (DES) after the survey began in 2013 August have shown a seemingly super-luminous supernova that erupted in a galaxy 7.8 billion light-years away. The stellar explosion, called DES13S2cmm, easily outshines most galaxies in the Universe and could still be seen six months later, at the end of the first of what will be five years of observing by DES. Supernovae are very bright, shining anywhere from a hundred million to a few billion times brighter than the Sun for weeks on end. Thousands of them have been discovered, and the word 'supernova' itself was coined 80 years ago. But super-luminous supernovae are a recent discovery, only being recognized as a distinct class of objects in the past five years. They are 10 to 50 times brighter at their peak than the brightest normal type of supernovae and, unlike other supernovae, their origins remain a mystery. It turns out that even within that select group, DES13S2cmm is unusual. The rate at which it is fading is much slower than for most other super-luminous supernovae that have been observed to date. That rate can often give information on the mechanisms that caused the explosion and the composition of the material ejected.
Understanding the origins of DES13S2cmm is proving difficult. Radioactive decay is known to power normal supernovae, but not from such extreme amounts of material. Astronomers have tried to explain the supernova as a result of the decay of the radioactive isotope nickel-56, but to match the peak brightness, the explosion would need to have produced more than three solar masses of the element. And even then the behaviour of the light-curve doesn't match up. The team is now investigating alternative explanations, including that DES13S2cmm is a normal supernova that has created at its core a magnetar -- an exotic neutron star spinning hundreds of times per second, producing a magnetic field 10*15 times stronger than that of the Earth. Energy from the magnetar is then injected into the supernova, making the explosion exceptionally bright. Neither model is a particularly compelling match to the data. But with luck, the DES should find enough such objects to allow us to view them as a population; at present there are too few known.
GROUND-BREAKING STEP FOR THE E-ELT
ESO
A ground-breaking ceremony has taken place to mark the next major milestone towards the European Extremely Large Telescope (E-ELT). Part of the 3000-metre peak of Cerro Armazones was blasted away as a step towards levelling the summit in preparation for the construction of the largest optical/infrared telescope in the world. That is just one part of an elaborate levelling process which will help landscape the mountain, so that it can accommodate the 39-metre telescope and its huge dome. A total of 220 000 cubic metres will need to be moved to make a site for the 150x300-m E-ELT platform. The Cerro Armazones civil works started in March and are expected to take 16 months. They include the laying and maintenance of a paved road, the construction of the summit platform and the construction of a service trench to the summit. The E-ELT first light is planned for 2024.
CALL FOR A GIANT SPACE TELESCOPE
RAS
In the nearly 25 years since the launch of the Hubble telescope (HST), astronomers and the public alike have enjoyed the wonderful views of the cosmos and the scientific discoveries that ensued. The successor to HST, the James Webb telescope, should be launched in 2018 but will have a comparatively short lifetime. Now Prof Martin Barstow of the University of Leicester is looking to the future. In his talk at the National Astronomy Meeting (NAM 2014) in Portsmouth, he called for governments and space agencies around the world to back the Advanced Technologies Large Aperture Space Telescope (ATLAST), an instrument that would give scientists a chance of detecting hints of any life that there might be on planets around other stars. ATLAST is currently a concept under development in the USA and Europe.
Scientists and engineers envisage a telescope with a mirror as large as 20 m across that like HST would detect visible light and also operate from the far-ultraviolet to the infrared parts of the spectrum. It would be capable of analysing the light from planets the size of the Earth in orbit around other nearby stars, searching for features in their spectra such as molecular oxygen, ozone, water and methane that could suggest the presence of life. It might also be able to suggest how the surfaces of planets change with the seasons. ATLAST would study star and galaxy formation, constructing the history of star birth in detail and establishing how intergalactic matter was and is assembled into galaxies over billions of years. If it goes ahead, ATLAST could be launched around 2030. Before that could happen, there are technical challenges to overcome, such as enhancing the sensitivities of detectors and increasing the efficiencies of the coatings on the mirror segments. Such a large structure may also need to be assembled in space before deployment rather than launched on a single rocket.
Topic: Mid July Astronomy Bulletin (Read 2252 times)