The Night Sky May 2017.

nightsky may17

The sky at midnight on the 16th. May 2017. All times GMT.

New moon: 25th Full moon: 10th.

The light evenings of mid-spring present a challenge to Astronomers; fewer dark hours at less convenient times means making the most of the sky when we can.

Look towards the south-west at sunset and you will see the brilliant Jupiter. Over the month it fades slightly from magnitude -2.4 to -2.3 but remains a very noticeable object. It lies in Virgo, Jupiter is above the star Spica which is a first magnitude object, yet compared to Jupiter it does not seem so bright. The moon will pass north of Jupiter on the 8th. and will be a lovely sight. Binoculars or a small telescope will show the four Galilean moons and possibly the cloud belts. Your writer had a look at Jupiter through a three inch telescope a few nights ago and was able to make out the equatorial cloud belts with their distinctive ruddy colour and the moons. SO give it a go!

Rising at 23:30 mid-month and by 22:30 at the end of the month Saturn brightens from magnitude 0.3 to 0.1 over the month. It is to be found in Sagittarius and so will be low in the sky. The moon passes just below Saturn on the 14th. Saturn is a beautiful sight and is always worth a look.

Although there are only two planets (which are fantastic objects to observe) there are other things to look at. If you find Leo, the star to the left is called Denebola, to the left of there lies the Virgo cluster. This is a rich area of galaxies which form part of the ‘Local Cluster’ of galaxies to which our Milky Way belongs. There are over 2000 galaxies in the Virgo cluster, many of which can be seen by amateurs – they will appear as fuzzy blobs, but don’t let hat put you off. The light you see form them has be travelling to your eye for millions of years!

On this Day…

90 Years Ago – May 20th.-21st. 1927: Charles A. Lindbergh made the first solo nonstop flight across the Atlantic Ocean. Lucky Lindy’s single-seat, single engine aeroplane was called the Spirit of St. Louis. It began the flight from Roosevelt Field in New York and landed at Le Bourget Air Field just outside Paris.

45 Years Ago – May 24th. 1972: U.S. President Richard M. Nixon and USSR Premier Aleksey N. Kosygin signed an agreement for cooperation in the exploration of outer space for peaceful purposes which included the docking in space of US/USSR spacecraft in 1975. It was signed in Moscow.

5 Years Ago – May 22nd. 2012: Dragon C2/C3 was launched from Cape Canaveral by a Falcon 9 rocket. The spacecraft was the first fully functional Dragon spacecraft on the Commercial Orbital Transportation Services (COTS) C2+ Demonstration Mission for NASA. It successfully docked with the ISS and was later recovered.

Published in: on May 2, 2017 at 11:32  Leave a Comment  
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B-Ring It On!

 

Saturn_s_B-ring_close-up

What do you think this picture might be? Could it be a microscope’s view of a hair? Could it be the pages of a really big book? They’re not bad guesses but they’re not correct.

This image focuses on a region in Saturn’s B ring, which is seen in twice as much detail as ever before, revealing a wealth of rich structure. It shows the incredible detail at which the international Cassini spacecraft is observing Saturn’s rings of icy debris as part of its dedicated close ‘ring grazing’ orbits. The spacecraft was at a distance of about 51 000 km from the rings

Saturn’s rings are composed mainly of water ice and range from tiny dust-size specks to boulders tens of metres across. Some of the patterns seen in Cassini’s close images of the rings are generated by gravitational interactions with Saturn’s many moons, these are known as shepherd moons which by their gravity help to keep the rings in shape by ‘kicking’ material into the rings or out into space. However many details remain unexplained.

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A Cassini image looking across Saturn’s rings showing where the B-ring lies.

The spacecraft’s ring-grazing orbits began last November, and will continue until late April, when the mission enters its ‘grand finale’ phase. During 22 final orbits Cassini will repeatedly dive through the gap between the rings and Saturn before plunging into the planet’s atmosphere in mid-September to conclude its incredible 13-year odyssey around the Saturn system.

If you want to see Saturn and its rings this is a good time to do it; Saturn rises about 2:15 in the morning in mid-March and an hour earlier by mid-April and lies in the constellation Sagittarius. That means for us that it is quite low in the sky. It gets to its highest point in the sky a little before sunrise, so you have a good chance of seeing it. (Sagittarius is a lovely constellation full of objects as when you look at it you are looking in the direction of the centre of our galaxy the Milky Way.)

You will need to look towards the East and South to see it but it will be the brightest object in that part of the sky.

To help you find it the moon will be either side of Saturn on the 16th and 17th of April.

Binoculars will show that it has a funny shape, almost like a rugby ball, and a small telescope will begin to show the rings. The rings are currently tilted towards us and will make for a lovely sight.

The Cassini-Huygens mission is a joint venture between NASA, ESA (the European Space Agency) and the Italian space agency ASI. It was launched from Cape Canaveral on the 15th. October 1997 aboard a Titan IV-B which is the NASA’s largest and most powerful rocket.

Published in: on March 26, 2017 at 12:14  Leave a Comment  
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Oh My!

The solar system is full of amazing sights; from aurora on Earth, to giant solar flares, to the great red spot there are countless objects to fascinate us. every now and then comes along something you just don’t expect. Often these are from objects you just wouldn’t imagine to be interesting (which just proves the old adage; ‘never judge a book by its cover.’)

The Cassini mission to Saturn (launched on October 15th. 1997 and arrived seven years later) is starting to wind down (sadly) and will soon be sent on a course that will see it fly through Saturn’s rings and eventually into the planet’s atmosphere to be destroyed. Despite that it is still providing us with surprises; the most recent being its images of the little shepherd moon Pan.

759Raw image of Pan. NASA. The grey lines either side of Pan are rings of Saturn!!

Looking through a telescope at Saturn from Earth the rings look quite simple; there

saturn_not_big

appear to be two sets separated by  black gaps or ‘divisions’. the Encke division is very difficult to see and cuts around the A ring. The second gap is the Cassini division and is much easier to see, lying between the A and B ring. The image below also shows the C ring or crepe ring which is very difficult to see in amateur telescopes and is only hinted at in the above Nordic telescope image.

post-6974-0-24780700-1405571735Stargazer’s lounge image. (Just for clarity and because you can never have too many pictures of Saturn!)

This begs the question: how are the rings able to stay so neat? could it be gravity and that he material that makes up the rings be in just the right place that they don’t change?

Pioneer 11  became the first spacecraft to visit Saturn. It was launched from Cape Canaveral  on the 5th. April 1973. Pioneer 11’s path through Saturn’s outer rings took it within 21,000 km of the planet, where it discovered two new moons (almost colliding with one of them in September 1979) and a new “F” ring. Saturn from Pioneer looked very similar to Saturn through a telescope.

739508main_739460main_AC79-9107_3-full_full Pioneer 11 image of Saturn.

It wasn’t until the Voyager spacecraft flew past Saturn ( Voyager 1 in November 1980 and Voyager 2 in August 1981) that we began to realise what a complicated and far more extensive system the rings formed.

8bg                       Saturn’s rings with “spoke” features in B-ring. Aug. 22, 1981. Distance 2.5 million miles.

The spokes created much excitement and discussion and were endlessly replayed in a video sequence on TV…and to be honest I did and still could watch them happily for hours.

10bg The F-ring (discovered by Pioneer 11.) Two braided but separate orbit rings. Nov. 12, 1980. Range 750,000 km.

A clue to the structure of the rings was found by Voyager 1 when  it discovered three new moons, Prometheus, Pandora, and Atlas. Prometheus and Pandora are shepherding moons of the F-rings, and Atlas is a shepherd of the A-rings. After a lot of analysis and some careful thinking it was realised that these moons are able to control the movement (or shepherd) of material making up the rings by either pushing the material into place in the rings or ejecting stray material from the system all together. All this is done by the gravitational force of the much larger satellites on the smaller material that makes the rings. Pan creates stripes called “wakes” ( which are places where ring material has collected in an orderly manner) in the ring material on either side of it. Since ring particles closer to Saturn than Pan move faster in their orbits, these particles pass the moon and receive a gravitational “kick”. This kick causes waves to develop in the gap and also throughout the ring, extending hundreds of miles into the rings. These waves intersect downstream to create the wakes.

Pan has a similar shape to Atlas and that unusual shape may be the result of fine material from the rings aggregating on the surface of the moon.

A little more about Pan before we go: it was discovered on the 16th. July 1990 by Mark Showalter who was working on Voyager data. It is approximately 35 kilometres across and 23 km wide. It lies within the Encke Gap in Saturn’s A Ring. It orbits Saturn every 13.8 hours, at a distance of 134,000 kilometres and is responsible for keeping the 325 kilometre wide Encke Gap open.

There are many fascinating worlds around Saturn – have a look for Daphnis another shepherd moon as well as the ones mentioned above.

To give you an idea of the complexity of the ring system here is another image from Cassini:

pia20506-1041

 

 

 

 

 

 

Uranus; discovered today in 1781!

238 years ago today on the 13th. March 1781, amateur astronomer William Herschel discovered a new planet: Uranus.

He was surveying the night sky when he spotted what he thought was a comet. He soon realised that it was moving too slowly for a comet. That could mean only be one thing: a planet. It took a further two years of observation to decide on just what was the nature of this object.

uranus-cartoon_en

NASA

Uranus was the first planet to be found with a telescope. Herschel was later knighted for his historic discovery, probably helped by his trying to name it Georgium Sidus (George’s star) after his patron King George III. It took seventy years before the name Uranus was finally decided upon.

Uranus is a strange world as unlike the others it rolls around the Sun on it’s side; this is possibly the result of a collision with a very large object that knocked it over! In 1789 Herschel thought he detected a ring around the planet but it wasn’t until 1977 that rings were definitively observed from the Kuiper airborne Observatory.

PIA02963 Image from Hubble showing tilt, rings and atmospheric activity

Uranus takes 84 years to orbit the Sun and lies about 2.87 billion kilometres from the Sun. Uranus spins about its axis once every 17 hours 14 minutes, leading to a year that is 30,190 days long! A long time between birthdays. 

At magnitude 5.9, Uranus is not visible with the naked eye, but binoculars or a small telescope can reveal it as a tiny blue-green dot. It is beginning to become a real challenge to see Uranus now as the nights begin to shorten; it sets around 20:50, shortly after Venus. The easiest way to find Uranus is to locate Venus – which is the really bright object in the west at sunset. From Venus draw a line to the left and you will come to a feinter orange object, that’s the planet Mars. With your binoculars move down to the lower right of the sky and slowly sweep the area; you will make out a small object; that’s Uranus! See the map below.

 

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Finder chart from Heavens-Above.com

 

Fancy a Trip to The Moon?

Elon Musk, the owner of SpaceX, a private rocket company, announced on the 27th. February that they will be sending two private citizens on a round the moon trip late in 2018.

SpaceX is probably the most successful private company launching into space, and has sent re-supply vessels (called Dragon) to the International Space Station, a feat it first performed on the 25.th May 2012. It began regular re-supply flight the following October. It has also launched satellites successfully into orbit.

dragon

The SpaceX Dragon.

The beauty about the Dragon is that it has been designed to carry not only cargo but people as well. It has yet to carry anyone but with NASA’s blessing they are now readying for the craft to start that part of its mission. The first test flight of the crew-ready version, the Dragon Version 2 will be un-manned and is currently slated for 2018 forming part of NASA’s Commercial Crew Program. It will be launched to the International Space Station. Later in the year a subsequent mission with crew is expected to fly. SpaceX is currently contracted to perform an average of four Dragon 2 missions to the ISS per year, three carrying cargo and one carrying crew

SpaceX haven’t been without problems though; on the 1st. September 2016 the rocket exploded on the launch pad during a pre-launch test of the engines. The previous June,       SpaceX experienced a major failure with one of its rockets when a Falcon 9 disintegrated en route to the ISS.

The rocket SpaceX use is called Falcon and unlike the rockets that sent man to the moon it is partly re-usable; the first stage returns to Earth landing vertically – almost like it was in reverse from take off. The rocket has completed this a number of times on a floating platform at sea and once on land returning to the launch site at Cape Canaveral. Where the rocket lands depends on the weight of the cargo that was launched, a sea landing is made after launching heavier items than a ground landing.

           falcon9-return  Falcon 9 returning to Earth.

SpaceX are working to a very tight deadline; to get the craft safe to launch people and then get them around the moon in the same year is going to big a big task. It took NASA 7 years, the loss of three crew mates ( a fire aboard the oxygen saturated cabin of Apollo 1 during a launch rehearsal in January 1967 led to the deaths of Virgil “Gus” Grissom, Ed White and Roger B. Chaffee)  and the development of new technology to send astronauts around the Moon on the Apollo 8 mission of 1968. It was not until 1969 and Apollo 11 that man first stood on the moon.

earthrise-apollo8

‘Earth Rise.’ Photograph taken by Apollo 8 astronauts.

If successful the two un-named astronauts will become the first ‘deep space’ travellers since the Apollo 11 crew. Their flight will take about a week, skimming the moon’s surface before flying past it and returning to Earth. The astronauts are funding themselves (estimates are that the cost of the moon flight will about $135 million dollars each) and will be given all necessary training before lift-off. Notwithstanding that, to learn all the systems, how to combat failures and how to react to emergencies in little over a year is going to be a massive task for them to undertake.

Despite the best training possible it cannot be overstated that this will be a risky venture. Once the craft is on its way to the Moon there can be no stopping and coming home if there is a problem. Whatever happens the crew will have to travel over 250,000,000 miles there and another quarter of a million miles back again. The reason for this is simple; the amount of energy needed to get to the moon, go round and return are huge, once the craft has the momentum it will not have enough fuel to slow it and change course for an early return to Earth. That burn is called TLI or Trans-Lunar Injection and is the point where they can’t change their minds!

circumlunar-free-return-trajectory

The path to the Moon. (Image from Wikipedia)

The Dragon mission will not stop at the moon but fly around using what is known as a  circumlunar trajectory or lunar free return flight. It uses gravity at the moon to cause the craft to return to the Earth. (See picture above.) The Apollo missions followed this sort of flight until Lunar Insertion orbit: achieved using rocket engines. Apollo used this trajectory in case of a major failure so that a stricken craft could return home without the need for extra engine firings.

Remember the problems that Apollo 13 encountered? There was an explosion of one of the oxygen tanks just two days after launch. They had to continue their journey but the lunar landing was scrubbed. They had to make repairs a carbon dioxide scrubbing machine so that the air they had could be re-cycled and re-used. On top of which they suffered from heat loss, limited power and a shortage of drinkable water. The astronauts got back by the skin of their teeth and required the ingenuity of ground crew, themselves and having material they could cannibalise to keep the life support systems going.

One notable achievement and a record which still stands – but could fall after the Dragon flight – was that the Apollo 13 crew travelled the farthest from Earth reaching a grand distance of 400,171 km  or 248,655 miles.

However Elon Musk has stated that the two adventurers are well aware of the risks and are happy to take them.

Despite the risks, who wouldn’t want to be one of those astronauts on an adventure back to the Moon?

Published in: on February 28, 2017 at 17:05  Leave a Comment  
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March Night Sky.

march-sky

Graphic from http://www.heavens-above.com

Night sky at 01h on the 20th. March.

Full Moon; 12th. March. New moon; 28th. March.

The Vernal or Spring equinox occurs on the 20th. March

Clocks go forward one hour on the 26th.March.

Spring is approaching and the sky is beginning to show changes as well. The winter constellations are disappearing in the west and spring constellations of Leo and Virgo are beginning to dominate the sky bringing their own treasures. (All times are in GMT.)

Mercury begins to make an appearance this month but as it is close to the Sun it is difficult to see. It fades from magnitude -1.7 at the start of the month to -0.4 by the end of the month. The end of the month is also the best time to see this elusive world as it sets around 20:30 a good couple of hours after the Sun. Make sure the Sun has set before event trying to find it.

Venus’ domination of the early night sky is coming to an end. It fades from magnitude -4.4 to -4.1 over the month but still remains a stunning sight. Venus sets just after 9pm at the start of the month and around 19:15 towards the end disappearing into the twilight.

Mars dims slightly this month from magnitude 1.4 to 1.6 as it moves from Pisces into Aries. It remains well placed for observation as it sets later as the month progresses around 21:50 at the start of the month to 22 hours by the end. The moon passes by twice this month; on the 1st and the 30th Mars will lie just to the North of the moon making a helpful finder.

Jupiter rises shortly after 8pm and so is visible all night long. It remains in the Virgo above Spica the constellation’s brightest star. The moon lies just to the north of the giant planet on the 14th and will make a lovely sight. Don’t forget to use binoculars to follow the paths of its four biggest moons as they orbit the planet.

Saturn remains an object for night owls this month rising around 03:30 at the start of March and by 02:40 at the end. It is to be found in Sagittarius which itself is a lovely rich constellation full of deep sky jewels. Being in Sagittarius also means that sadly Saturn will not be very high in the sky. The moon passes just to the north of the ringed planet on the 20th.

 

On This Day…

105 Years Ago –March 23rd. 1912: Dr. Wernher von Braun, the father of modern rocketry, was born in Wirsitz, Germany (now Part of Poland).

80 Years Ago — March 6th. 1937: Valentina Nikolayevna Tereshkova was born in Maslennikovo, in the Yaroslavl Region of the USSR. She was the first woman in space when she was launched aboard Vostok 6, on the 16th. June 1963.

70 Years Ago — March 7th. 1947: The first photograph was taken from space by a V2 rocket 100 miles above White Sands, New Mexico.

40 Years Ago – March 10th.1977: The rings of Uranus were discovered using the Kuiper Airborne Observatory. They planet was to be used to observe the occultation of the star SAO 158687 by Uranus to study the planet’s atmosphere, when instead the star seemed to flicker, indicating the rings. An unexpected and lucky discovery!

15 Years Ago – March 25th. 2002: Shenzhou 3 (Divine Vessel 3), a Chinese unmanned spaceship, was launched by a Long-March 2F rocket from the Jiquan Space Launch Centre in the north-western Gobi desert. It consisted of three modules: a propulsion section, a conical re-entry capsule, and an orbiter. The capsule was equipped with all that would be needed for a manned flight.

Published in: on February 28, 2017 at 15:39  Leave a Comment  
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February’s Night Sky.

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Sky at midnight on 22nd. February.

(Sky map generated from Heavens-Above.com)

Full Moon; 11th. February. New Moon; 26th. February.

Venus dominates the early evening sky: it is visible from sunset until around 21:15 shining at a magnificent -4.4. have a look at it with binoculars and see if you can make out its shape; it should look like a half-moon. This shape is known properly as ‘Dichotomy.’

Diagonally up to the left from Venus you will find Mars. It is a lot feinter than Venus shining at magnitude 1.1 it fades slightly over the month to 1.3 by the 28th. it sets at 21h50 by the month’s end. Even through a telescope not much detail will be seen as it is a very small object. It is still worth having a look at all the same. On the 1st Mars lies in-between Venus and the Moon.

Rising at 23:30 at the start of the month and at 21:40 by the end is the mighty planet Jupiter. It shines at a bright magnitude of -2.0 brightening to -2.2 by the 28th. Lying in the constellation Virgo, Jupiter can be found just to the north of the bright star Spica. Jupiter is always worth observing; look out for the four main moons of the planet; they are called the Galilean satellites as they were first observed by Galileo in 1610. Over a few nights you will be able to see them change position as they move around the planet. Through binoculars or a telescope they look like stars but you will know they are moons by the speed they change position. The moon passes just above Jupiter on the 15th and 16th.

If you want to see the ringed planet Saturn you’ll need to get up early. It rises around 5:10 in the morning at the start of February and at 3:30 by the end of the month. Although it is not too bright at magnitude 1.4 it lies in the unremarkable and feint constellation of Ophiuchus, the thirteenth sign of the zodiac. The moon passes by Saturn over the nights of the 20th. and 21st. to help you find it.

On This Day…

111 Years Ago – February 7th. 1906: Birthday of Clyde Tombaugh, discoverer of planet Pluto.

87 Years AgoFebruary 18th. 1930: Pluto was discovered by Clyde W. Tombaugh of the Lowell Observatory, Flagstaff Arizona.

72 Years AgoFebruary 1945: Arthur C. Clarke wrote a letter to the editor of Wireless World describing geostationary communication satellites.

26 Years AgoFebruary 7th. 1991: the Soviet space station Salyut 7 re-entered Earth’s atmosphere at 04:00 UTC.

size-of-space-stations

A comparison of the sizes of space stations and the Shuttle.

From top left; Salyut 1 and Skylab. Below them Mir. On right at top Salyut 7, at bottom the Shuttle and the big structure is the International Space Station.

Published in: on January 24, 2017 at 14:11  Leave a Comment  
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January’s Night Sky.

jan17-sky

The night sky at 01h30 on the 20th.

(Map generated on Heavens-Above.com)

Full Moon 12th. January. New Moon 27th. January.

Only three planets are visible this month; we start off with Venus. As soon as the Sun sets it is an easy to find shining at magnitude -4.4 in the south-west. By mid month it sets just before 9pm. Venus is almost a half crescent at the moment and it is easily noticed through binoculars.

Mars is a lot feinter than Venus at magnitude +0.9 and shines like a red star a little to the left of Venus. Not much detail is visible even through a telescope as it is such a small object.

Jupiter rises before 01:30 and shines at magnitude -1.8, brightening to -2.0 by the end of the month, in the constellation Virgo. It lies just above Spica, the brightest star in the constellation, which is outshone by the brightness of the king of the planets.

This month sees the Quadrantids meteor shower. It peaks on the 3rd but continues on until the 12th. The radiant, the point from which they appear lies close to he constellation Boötes.

Published in: on January 24, 2017 at 14:01  Leave a Comment  
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“The Stars are Painted with Unnumber’d Sparks…”

Little did William Shakespeare know how true were those words he made Caesar utter. Our eyes can see only ‘visible light’ which is a small amount of the electromagnetic spectrum, there is so much more we can’t see without the help of technology.

The Electromagnetic spectrum is a term which scientists use to describe the entire range of light that exists: everything from radio waves to gamma rays, including x-rays and microwaves are all forms of light.

elctromagnetic-spectrum

Electromagnetic spectrum. (NASA)

As can be seen from the chart visible light covers just a fraction of what there is to see. It turns out that different objects in the universe radiate at different wavelengths, some we can see – like light – some we can’t. Some can be observed from Earth – for example radio waves – and some can’t, because the Earth’s atmosphere blocks them, like gamma rays.

For wavelengths absorbed by the atmosphere we have to build satellites and send them into space – often a good distance from Earth to allow them to be cool enough to do their work; the Herschel Space Observatory which observed the infrared orbits 1,500,000 kilometres (930,000 miles) from Earth (by comparison the International Space Station orbits just 400 kilometres from Earth.)

Objects can emit radiation at different wavelengths and that can give us additional insights into their nature. The hotter the object, the shorter the wavelength (the distance between two peaks or crests) and the more energetic it is.

shape-of-wavelength

The shape of an electromagnetic wave (radio, visible etc.)

The following images of the Sun were taken in ultraviolet and visible light on the same day. The difference in what you can see is remarkable;

 

sun-in-uv

UV light.

sun-in-visible

Visible light.

Astronomers at the Murchison Wide Field Array (MWA) radio telescope in Australia decided to observe the universe at radio wavelengths. The survey known as the GaLactic and Extragalactic All-sky MWA (GLEAM) shows what the Milky Way and 300,000 galaxies look like if we could see radio waves.

The human eye can only see three primary colours (red, blue and green), the Mantis shrimp can see in twelve primary colours, GLEAM ‘saw’ in twenty primary colours, beating every living thing and revealed the remnants of explosions from the most ancient stars in our galaxy, and the first and last gasps of supermassive black holes;

galaxy-visibleIn visible light.

 

galaxy-radioIn radio light.

And if you want to see what it all looks like in a variety of wavelengths try this;

http://gleamoscope.icrar.org/gleamoscope/trunk/src/

The MWA is soon to become part of the Square Kilometre Array (SKA) of radio telescopes working with radio observatories in South Africa and Jodrell Bank. Together they will be able to make even better maps of those unnumber’d sparks.

 

 

“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…

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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!