EUROPA’S ERUPTING WATER.

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A Tardigrade.

We believe that water is an essential ingredient for life; all living things we know of need water to some extent; we are somewhere between 50% and 65% water (depending on age and fitness) whilst the Tardigrade (or Water Bear) the most resilient creature known can survive with only 3% of its body mass as water. (The Tardigrade is an amazing almost unbelievable creature; it is 0.5mm long and can withstand temperature ranges from −272 °C (which is almost absolute zero, the coldest temperature possible) to 150 °C and pressures about six times greater than those found in the deepest parts of the ocean trenches. It can also survive doses of radiation that would quickly kill a human as well as the vacuum of outer space.)

So discovering water is believed to be a key to finding life; the recent announcement by NASA that the Hubble Space Telescope has seen water jets on Jupiter’s moon Europa is exciting.

Europa has been considered a potential candidate for life with its great subsurface ocean. Therein lies the problem. To get to the ocean would require drilling through a layer of extremely cold and hard ice of unknown thickness. Whilst we are used to drilling through the Earth getting the necessary machinery, making sure it is totally germ and microbe free and then operating it on a hostile world would be incredibly challenging.

The plumes provide a tantalizing opportunity to gather samples originating from under the surface without having to land or drill through the ice.

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Hubble Image of plumes with a photo of Europa superimposed.

Amazingly this was not what the scientists were looking for! They wanted to find out if Europa had an atmosphere. It seems strange to think that they would try to find an atmosphere on such a small object (it is 3,100 km or 1,900 miles in diameter) so far away (some 628.3 million kilometres away) with a telescope.

There is a technique used for finding planets around distant stars which looks for an object passing in front (transiting) a star. As an object transits a star it blocks a fraction of the light from the star making it fade slightly which can be measured. If this happens more than once then there is a chance that it is a planet. Astronomers can then observe the light from the star (using an instrument known as a Spectrograph) to see it’s chemical make-up and then look again at the star as the object passes in front. Any difference in the reading of the star’s chemical make up allows astronomers to work out what makes up the atmosphere of the planet. The first technique was the one used was on Europa.

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The astronomers spent 15 months observing ten transits by Europa and saw these plumes three times. Another team had detected something similar in 2012 using the same piece of equipment on Hubble (the Imaging Spectrograph.) however neither team has been able to observe the same event at the same time. That is the next challenge, once that has been done then there will be a very strong case for the plumes existence.

The findings of the two teams are very similar though; suggesting that the water vapour is erupting from the frozen southern polar region of Europa and reaching more than 100 miles (160 kilometers) into space. Maybe as much as a few million tonnes of water are expelled this way. It is believed there is more water under Europa’s surface than on the Earth!! Observations thus far have suggested the plumes could be highly variable, meaning that they may sporadically erupt for some time and then die down. This makes them very difficult to be seen by more than one group of astronomers at a time.

If confirmed, Europa would be the second moon in the solar system known to have water vapor plumes. In 2005, NASA’s Cassini orbiter detected jets of water vapour and dust coming from the surface of Saturn’s moon Enceladus.

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NASA hope to launch a mission to Europa called, for now, the Europa Multiple flyby Mission. It is in the planning stages now and one of the ideas is to send a lander to the moon to sample the surface if not try to drill into it.

Here is a NASA clip about the mission:

Exciting times ahead!

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Published in: on September 27, 2016 at 16:30  Leave a Comment  
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THE INTRIGUING WORLD OF ENCELADUS.

Enceladus is one of Saturn’s most interesting moons. It had long been suspected that there may have been a small ocean lying under the icy crust of the satellites south pole: images of geysers shooting jets ice and dust have often been imaged by the Cassini probe orbiting Saturn.

NASA have now discovered (15th. September 2016) that there is a global ocean hidden beneath the ice covering the whole moon. The finding implies the fine spray of water vapor, icy particles and simple organic molecules Cassini has observed coming from fractures near the moon’s south pole is being fed by this vast liquid water reservoir.

Cassini scientists analysed more than seven years’ worth of images of Enceladus taken by the spacecraft, which has been orbiting Saturn since 2004. They carefully mapped the positions of features on Enceladus — mostly craters — across hundreds of images, in order to measure changes in the moon’s rotation with extreme precision.

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The icy surface of Enceladus.

As a result, they found Enceladus has a tiny, but measurable wobble as it orbits Saturn. Because the icy moon is not perfectly spherical — and because it goes slightly faster and slower during different portions of its orbit around Saturn — the giant planet subtly rocks Enceladus back and forth as it rotates.

Using computers to measure this wobble, or libration, scientists have worked out that there the ocean must be moon-wide as anything smaller would result in a much smaller libration.

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How Enceladus’ may look.

Saturn lies 1.4 billion kilometres from the Sun (that’s eight times further away than Earth is from the Sun) a year on Saturn is 29.5 earth years long. Because it is so far away the Sun is not as powerful as it is on Earth and so temperatures are much lower, so much lower that liquid water shouldn’t exist on any body that far away and yet it does.

How is that possible? Well that is a mystery although some astronomers think possibility that tidal forces due to Saturn’s gravity could be generating much more heat within Enceladus than previously thought. Saturn is much bigger than Enceladus and as the moon orbits the planet its surface is gently pulled in and out of shape by Saturn’s gravitational force possibly generating heat that allows water to flow. This pulling on a smaller a body is what is meant by a tidal force.

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Cassini’s image of jets.

Scientists first detected signs of the moon’s icy plume in early 2005, further discoveries have been made: in 2015 they shared results that suggest hydrothermal activity is taking place on the ocean floor. On Earth hydrothermal vents are found on the floors of oceans, raising the temperature of the water nearby by many degrees, this in turn allows for all kinds of unusual and unexpected creatures to be found in regions where it had been thought there could be no life.

The material ejected from Enceladus may also help keep Saturn’s magnificent rings topped up with material. How the rings have survived for so long under the tidal forces of the gas giant’s gravity has long been a mystery but this may go some way to solving that puzzle.

All these findings raise the inevitable but intriguing question; could there be some form of life lurking in the Ocean of Enceladus? Cassini will continue to examine the plumes of material ejected from the moon to try and detect signs that something even more amazing may be waiting to be found.

In fact Cassini is scheduled to make a close flyby of Enceladus on the 28th. October, in the mission’s deepest ever dive through the moon’s active plume of icy material. The spacecraft will pass just 30 miles (49 kilometers) above the moon’s surface. there is a lot more to learn about this and the other amazing moon of Saturn.

Published in: on September 27, 2016 at 09:53  Leave a Comment  
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On Relics.

Here is a link to a fascinating look at St. Teresa of Calcutta and astronomy. It’s written by an American priest, Fr. James Kurzynski. Well worth a read.

Astronomy and Mother Teresa’s Shoes: Relics of the Sacred.

Published in: on September 8, 2016 at 16:52  Leave a Comment  
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A Living Fossil.

It seems the more we know the more we find out. In the natural world there are creatures nick-named ‘living fossils.’ The phrase was first used by Charles Darwin and relates to living things that have remained largely unchanged for millions of years. Two very different examples are Ctenophores and Gingko Biloba.

Ctenophores are also known as comb jellyfish. They propel themselves through the sea using lots of tiny hairs known as cilia. They are believed to have first appeared on Earth 700 million years ago which could mean that humans descended from them!

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A Ctenophore.

Gingko Biloba, or the maidenhair Tree, is the only one of its kind. It has neither ancestors nor evolved descendants. It is a truly ancient plant with fossil records of it dating back to the Permian era some 270 million years ago. It is much used today for its healing and soothing properties.

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A fossilised Gingko leaf.

So what has this to do with Astronomy? Well Astronomers have been looking at one of the globular clusters that are attached to the Milky Way, and have concluded that it is a living fossil from the earliest times of the galaxy: Terzan 5 is 19 000 light-years away and orbits the central bulge of the galaxy. It appears at the moment to be coming towards us at about 90Km/s.

The Milky Way is a spiral galaxy, with most of its stars to be found at the centre where they form a bulge. If you imagine our galaxy as two fried eggs put back to back the yolks represent the bulge.milky-wayHow our galaxy might look from afar.

It was only discovered in 1968 by French astronomer Agop Terzan. It lies in the constellation Sagittarius and is obscured by the number of stars in the area making it hard to find. Astronomers noticed in 2005 to have two distinct populations of stars with an age gap of 7 billion years. It was thought that Terzan 5 might have been the remnant of a dwarf galaxy that got too close to ours and was disrupted (broken up) by the gravity of the Milky Way.

Peering through the thick dust clouds of the galactic bulge an international team of astronomers has revealed the unusual mix of stars in the stellar cluster known as Terzan 5. The new results indicate that Terzan 5 is in fact one of the bulge's primordial building blocks, most likely the relic of the very early days of the Milky Way. This picture is from the Multi-Conjugate Adaptive Optics Demonstrator (MAD), a prototype adaptive optics system used to demonstrate the feasibility of different techniques in the framework of the E-ELT and the second generation VLT Instruments. The star colours are from the Hubble image of the same star field.

This picture is from the Multi-Conjugate Adaptive Optics Demonstrator (MAD), a prototype adaptive optics system used to demonstrate the feasibility of different techniques in the framework of the E-ELT and the second generation VLT Instruments. The star colours are from the Hubble image of the same star field.

It has now been discovered that this is not the case. Using instruments on the Hubble Space telescope, the WM Keck telescope and the ESO’s Very Large Telescope (VLT) in Chile Astronomers have been taking another look at these two lots of stars. They found that as well as the age gap they are made up of very different elements. This age gap indicates that the star formation process in Terzan 5 was not continuous, but was dominated by two distinct bursts of star formation.

This means its ancestor must have had large amounts of gas for a second generation of stars, something along the size of at least 100 million times the mass of the Sun! It had to be massive for it to have survived the 12 billion years since the galaxy formed without being disrupted They have also found that he stars in Terzan 5 have very similar properties to those found in the galactic bulge.

These unusual properties, which are uncommon amongst globular clusters, are why Astronomers are calling it a living fossil. The current theory of how galaxies form requires vast clumps of gas and stars to interact and then merge and dissolve to form the primordial bulge of the Milky Way in the process. Some of Terzan 5s characteristics “…resemble those detected in the giant clumps we see in star-forming galaxies at high-redshift, [that is galaxies far away from us] suggesting that similar assembling processes occurred in the local and in the distant Universe at the epoch of galaxy formation.” according to lead Astronomer Francesco Ferrari.

The research presents a possible route for astronomers to unravel the mysteries of galaxy formation, and offers an unrivalled view into the complicated history of the Milky Way.

If you want to know where Terzan 5 is, here is a map; the region (Sagittarius) is visible form the UK but the cluster itself, well that is a different matter!

This chart shows the rich constellation of Sagittarius. Among the many star clusters in this part of the Milky Way lies Terzan 5, a stellar cluster which resembles a globular cluster. This picture plots most of the the stars visible on a dark clear night with the naked eye.

This chart shows the rich constellation of Sagittarius. Among the many star clusters in this part of the Milky Way lies Terzan 5, a stellar cluster which resembles a globular cluster. This picture plots most of the the stars visible on a dark clear night with the naked eye.

 

Published in: on September 8, 2016 at 16:17  Leave a Comment  
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