HUNTING FOR ALIENS or COSMIC PURALISM ANEW.

The earliest writers dreamt of life on the planets in our solar system; the Aborigines have stories dating thousands of years about the Dreamtime and how we came from the stars. The satirist Lucian (120 – c185 AD) claims in “A True Story” to have visited the moon after his ship was caught in a whirlwind which sends them to the Moon: a place inhabited by beings at war with the people of the Sun over the colonisation of the Morning Star, Venus. The title of first science fiction writer is most likely his!

Lucian.                                                       H.G. Wells.

In more recent times we had HG Wells’ ‘War of the Worlds’ (1897) followed a few years later by the astronomer Percival Lowell’s canals on Mars (1906) – where he believed he saw artificial canals, going so far as to draw them – to the idea that Venus might contain dinosaurs we have always been desperate to find life “out there”.

Looking for life beyond Earth is one of the most fascinating, exciting and difficult things to do. Every time we think we might have found a clue a discovery comes along to challenge us.

Modern research looks for ‘bio-markers’; these are chemicals that could only be present as a result of life. Nothing has been found (so far!!) in the solar system so the search has broadened into he universe to the exo-planets, the worlds around distant stars.

How do you find which gasses are present in a world in another solar system? It seems that the size (diameter) of the planet plays a role in whether we can detect atmospheres; a recent report in the Astrophysical Journal (https://arxiv.org/abs/1704.05413) goes into more detail. According to Angelos Tsiaras, the lead author, “More than 3,000 exoplanets have been discovered but, so far, we’ve studied their atmospheres largely on an individual, case-by-case basis.”

exoplanets

Using the Hubble Space telescope researchers looked at the spectral profiles of 30 exoplanets and analysed them for the characteristic fingerprints of gases that might be present. About half had strongly detectable atmospheres. Most of the atmospheres detected show evidence for clouds. The two hottest planets, where temperatures exceed 1,700 degrees Celsius, appear to have clear skies, at least at high altitudes. Results for these two planets indicate that titanium oxide and vanadium oxide are present in addition to the water vapour features found in all 16 of the atmospheres analysed successfully.

It is not only ‘Hot Jupiters’ that have had their atmospheres analysed: in April 2017 it was announced that Gliese 1132b, a super-earth, (that is a planet with a diameter upto 40% greater than the Earth’s) atmosphere had been detected. This is a major step in detecting signs of life in more earth like planets. (https://arxiv.org/abs/1612.02425)

gliese 1132b

How do astronomers detect the atmospheres? Well as a planet passes in front (transits) its host star the light from the star dims slightly; the planet blocks some of the light and the atmosphere absorbs some of the star light. If the composition of the star’s atmosphere is already known, when the planet transits the star, the planet’s atmosphere absorbs some of the starlight and changes what chemicals we can see from the starlight. It Is then possible to work out the composition of the planet’s atmosphere by the effect it had on the starlight.

The chemicals that astronomers look for when seeking life are called ‘bio-markers.’ They include Oxygen and Methane, which tend to be the product of organic processes and a chemical known as Freon-40. This latter was hoped to be a good indicator but, like Lucian’s moon people or Lowell’s canals things are not what they seem.

ALMA and Rosetta Detect Freon-40 in Space

Organohalogen methyl chloride (Freon-40) discovered by ALMA around the infant stars in IRAS 16293-2422

Freon-40 (CH3Cl), also known as methyl chloride. is known as an organohalogen; these are compounds which on Earth are formed by organic processes. Organohalogens consist of halogens (the inert gasses of the periodic table), such as chlorine and fluorine, bonded with carbon and sometimes other elements. On Earth, these compounds are created by some biological processes — in organisms ranging from humans to fungi —  as well as by industrial processes such as the production of dyes and medical drugs.

The idea was if Freon-40 is formed naturally on or earth or through artificial means then its detection in an exo-planet’s atmosphere would be a very good indicator of life, however that hoped has been dashed as Observations made with the Atacama Large Millimeter/submillimeter Array (ALMA) and ESA’s Rosetta mission, have revealed the presence of Freon-40 in gas around both an infant star and a comet. The star lies 400 light years way, the comet is the famous 61/P Churyamov-Gerasimenko; this is the comet that saw the European Rosetta probe orbit it and send the little lander Philae to its surface.

This is the first ever detection of them in interstellar space.

IRAS 16293-2422 in the constellation of Ophiuchus

This chart shows the location of the Rho Ophiuchi star formation region in the constellation of Ophiuchus. The star Rho Ophiuchi, which gives the region its name, is marked with the Greek letter rho (ρ). The position of IRAS 16293-2422, a young binary star with similar mass to the Sun, is marked in red.

This may mean that astronomers have understood things the wrong way round; rather than being a marker for life perhaps it is a necessary constituent of the ‘primordial soup’ from which life arises:

“ALMA’s discovery of organohalogens in the interstellar medium also tells us something about the starting conditions for organic chemistry on planets. Such chemistry is an important step toward the origins of life,” adds Karin Öberg, a co-author on the study.

This isn’t the only chemical that ALMA has detected, other molecules of astrobiological interest found around young stars on scales where planets may be forming have precursors to sugars and amino acids.

The discovery of Freon-40 around Comet 67P strengthens the idea that what we see in the pre-biological chemistry of distant protostars may have been what we would have seen in our own Solar System. It would seem that young solar systems inherit some of their chemical characteristics from their parent star forming cloud and then from cometary impacts.

                     ALMA 

  ALMA the Atacama Large Millimeter/submillimetrer Array.

It just shows, that when you think you may be onto a clue the Universe has different ideas!

Advertisements

“IT’S LIFE JIM…” OR IS IT?

marvin-the-martian1

 

 

 

 

 

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.

ngc_6866_map1

 

 

 

 

 

 

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.)

 algol-light-curve1

(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.)

da43fcf76c7d11b857b6303b0f669870_original11

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…

478138-five-hundred-meter-aperture-spherical-telescope-fast-world-s-largest-radio-telescope-tianyan-telescope-guizhou-province-science-technology-space-mission-telescopic-equi1

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!