“IT’S LIFE JIM…” OR IS IT?

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Looney Tunes character Marvin

 

We really are obsessed with finding life in space. If it’s not Martian invaders á la Orson Welles it’s Marvin the Martian hunting down poor old Bugs Bunny. Tales of visitations from and abductions by aliens abound on the internet. And we have telescopes dedicated to listening for signals or spotting unusual variations in the light from Sun like stars.

There have been two in particular that have fuelled the imagination, especially of copywriters. The first is KIC 8462852 also known as Tabby’s star after one its discoverer Tabetha Boyajian. This star is 1,480 light-years away in Cygnus and is an f-type star, slightly younger than the Sun but otherwise pretty similar. In October 2015 Astronomers at Yale found it displayed some unusual light variations.

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The position of Tabby’s star.

 

A lot of stars vary in brightness and output (even the Sun albeit very little) and are well understood; they may have companion stars crossing in front of them blocking off some light, think Algol (beta Persei) or there may be a dense cloud that passes by doing the same thing as it orbits a star (as is the case with epsilon Aurigae, which has a noticeable 27 year period.)

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(Notice how much more regular are the dips for Algol in brightness than for Tabby’s star below.)

The way the light changes for these types of objects is pretty straightforward and smooth. Not so for Tabby’s star; astronomers noticed that it faded at first by about 0.34% over a few years but it then in just 200 days it faded by 2.5%. It then carried on fading in its previous way. No star near-by showed similar patterns.

The Kepler space telescope had been monitoring Tabby’s star for a number of years and showed that in 2011 and 2013 the star dimmed a very dramatic way. It had faded by a whopping 22%. This dimming could last between five and eighty days at a time. Something very big had to be passing in front of it. (Flux refers here to the brightness of the object.)

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This led some to suggest a Dyson Sphere. In 1960 theoretical physicist Freeman Dyson suggested that an advanced civilisation might be able to build and sphere or shell to encase a star to harness its power, or that a swarm of satellites or solar panels could surround a star, known as a Dyson swarm, could do the same thing. A Dyson swarm would be easier than an all encompassing sphere to build but still is beyond our ability. Other fanciful suggestions have been gigantic space habitation platforms or even artificially built occulting masks that deliberately dim the star to alert other species that there is life there.

As a result a lot of radio telescopes were turned towards the star to listen for any signal that might suggest life. Sadly nothing has, so far, been heard.

As with the ‘Little Green Men’ signal that ushered in the discovery of the super regular emissions of pulsars people are quick to imagine the fanciful; the reality is likely to be slightly more prosaic but none the less interesting. Current theories suggest the unusual diming may be caused by the break-up of a lot of really large comets orbiting the star (although how this would happen is debatable) or it could even be errors with the data…we still don’t yet know.

But, if you’re hoping for aliens another 234 stars have piqued interest. A paper released on arXiv.org claims that after looking at 2.5 million stars surveyed by the Sloan Digital Sky Survey 234 have a very unusual and puzzling light signature. One of the lead astronomers for this paper EF Borra (who works in Canada) claims these light patterns are similar to those he proposed in an earlier paper that might come from an alien civilisation signalling their existence to others. (Here is the link to the paper; https://arxiv.org/abs/1610.03031 )

Could they be from aliens? This is what the scientists themselves say in their pre-amble to the article; “We find that the detected signals have exactly the shape of an ETI signal predicted in the previous publication and are therefore in agreement with this hypothesis. The fact that they are only found in a very small fraction of stars within a narrow spectral range centred near the spectral type of the sun is also in agreement with the ETI hypothesis. However, at this stage, this hypothesis needs to be confirmed with further work.” They do go on to add a note of caution; “Although unlikely, there is also a possibility that the signals are due to highly peculiar chemical compositions in a small fraction of galactic halo stars.”

(ETI stands for Extra-Terrestrial Intelligence.)

Well a lot more studying of these signals from a lot more institutes with a lot more equipment will be needed before any definite answer can be given. Perhaps the brand new Chinese radio telescope FAST may look at these signals…

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FAST stands for Five hundred metre Aperture Spherical Telescope and is one of the largest radio telescopes in the world. In area it is roughly the equivalent to thirty football pitches or 200,000 square meters. Work began on building it in 2011 and it is already built and after undergoing tests before beginning its working life on the 25th September 2016. The web page for FAST is; http://fast.bao.ac.cn/en/

There is a larger radio telescope in Russia called RATAN 600 which is 576m in diameter, but, unlike FAST, is composed of segments that make up the whole dish (895 of them of size 2×7.4 m.) It was involved in the detection of an unusual and regular signal which could have been alien in origin, however after other observatories failed to repeat the observation, and because of the frequency it was observed it was decided that RATAN had picked up signals from a secret military reconnaissance satellite.

                                   1987_cpa_58931RATAN commemorated in a 1987 stamp.

So, you do need to be careful when making assumptions about unusual observations, as it could be alien in origin or more likely something else all together!

 

 

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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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