The March Night Sky.

march18sky

Full Moon: 2nd. and 31st. March. New Moon: 17th.

20th. March is the Vernal (Spring) Equinox. 25th. March Clocks go forward one hour.

This will be the best month of the year to see Mercury. The elusive world is an evening object shining at magnitude -1.0. On the 4th it is just 1.1° north of the much brighter Venus, later on in the month, the 19th, Mercury again passes by Venus although not as closely as the first time. By the end of the month Mercury will begin to disappear into the twilight.

At magnitude -3.9 Venus shines brightly in the evening sky. It starts the month close to Mercury. On the 18th just to the north of the day old moon which could make for a lovely sight and photograph. On the 29th Venus passes 0.1° south of Uranus. You will need a telescope or binoculars to see Uranus (which is just beyond naked eye visibility at magnitude +5.9.) The pair will be low in the sky and will be a challenge to see.

Mars, the red planet, rises just before 03h mid-month and lies close to the waning moon on the 10th. It will be low in the morning sky as it moves from Ophiuchus into Sagittarius. It brightens over the month from magnitude +0.8 to +0.3.

Jupiter rises around midnight but is low in the sky and outshines (at magnitude -2.1) all the stars in the feint constellation of Libra. The moon passes to its north on the 7th.

Another low in the sky object this month is Saturn. It rises before 03h30 mid-month and shines at magnitude +0.5 and is to be found in Sagittarius.

 

On This Day…

55 years ago – March 21st 1963: USSR lost contact with Mars 1 when it was 66 million miles from earth. Mars 1 would become the first spacecraft of any nation to fly past Mars.

March 28th: Saturn/Apollo 4 was launched by Saturn 1 from Cape Canaveral. It was a Suborbital test flight of the first stage of the Saturn rocket.

50 Years Ago – March 2nd 1968: Zond 4 was launched by Proton K rocket from Baikonur, USSR. It was an unmanned test flight of the Soviet circumlunar spacecraft.

March 27th: Yuri Gagarin, the first human in space, died in a MIG-15 crash northwest of Moscow.

40 Years Ago – March 2nd 1978: Soyuz 28 crew were launched aboard a Soyuz rocket from Baikonur to the Salyut-6 space station. The crew was: Alexei A.Gubarev and Vladimir Remek (Czech), who was the first non-Soviet, non-American. space explorer making this the first international space crew.

10 Years Ago – March 9th 2008: Jules Verne, also known as ATV 1, was launched by an Ariane 5 rocket. ATV-1 was ESA’s first automatic transfer vehicle, and the first non-US and non-Russian vehicle to successfully dock with the ISS.

5 Years Ago – March 1st 2013: SpaceX Dragon CRS-2 automated ISS cargo vehicle was launched from Cape Canaveral. This second operational Dragon cargo vehicle was the first commercial vehicle to carry externally mounted cargo to the ISS.

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A Bubbling Star.

We know that eventually the Sun will become a red giant. What then will the Sun look like?

In about 4.5 to 5 billion years the sun will swell and become a red giant star; this happens as the star runs out of hydrogen to fuse for energy and turns to material that’s harder to fuse. This means the balance between gravity and the expansive force caused by this nuclear fusion starts to become unbalanced and the sun will swell. It will then go through a phase of expansion and contraction where it expels its outer layers leaving behind a planetary nebula.

The Sun is very active: images show it to be a swirling, seething place;

solar granulation

The Sun is made from seven different layers;

At the centre is the core, this is where nuclear fusion occurs.

Next there is the radiative zone which “radiates” the energy created in the core by the emission and reabsorption of photons.

Then comes the convection zone; light particles (and all other particles) can take 170,000 years to travel through this layer. The behaviour of photons here is called the “random walk” where the photon collides with other photons: this happens as it is such a dense region.

sun_layers1332206352080

Next is the photosphere this is the first of the three parts that make up the Sun’s atmosphere: this is where photons are finally emitted and give the sun its brightness. Oddly enough this area is opaque to light, meaning we can’t see trough it. If we could we would be able to view the thermonuclear core directly!

The transfer of energy from the convection zone below appears in the form of granules (see the photo above). As the hotter gas rises up, the cooler gas descends only to be re-heated by the convection layer and the process repeats itself. Sometimes disturbances in the magnetic field will produce sunspots, which occur within the photoshphere.

The chromosphere is next; the temperature ranges from 4400K at the base to 25 000K at its outer edge; no-one knows why the temperature rises so dramatically as it goes away from the surface of the Sun, it’s possible magnetism may be involved but it remains a puzzle.

Finally we have the corona. This outer layer is very dim – a million times dimmer than the photosphere and is the hottest region of the Sun at 10^6 K. Because the Corona extends several million kilometres into space, there is a lot of room for molecules to move. It is this movement that is the source of the solar winds. The high temperature of the Corona can force ions to move as fast as a million kilometres per hour. We can only see the corona during total solar eclipses when the disc of the sun is totally obscured.

It seems that when the Sun does begin to enter its final phases of existence it will still be quite an active place; Astronomers using ESO’s Very Large Telescope have for the first time directly observed granulation patterns on the surface of a star outside the Solar System — the ageing red giant π1 Gruis. It is located 530 light-years from Earth in the constellation of Grus (The Crane), π1 Gruis is a cool red giant. It has about the same mass as our Sun, but is 700 times larger and several thousand times as bright.

The image below from the PIONIER instrument reveals the convective cells that make up the surface of this huge star, which has 700 times the diameter of the Sun. Each cell covers more than a quarter of the star’s diameter and measures about 120 million kilometres across.

The surface of the red giant star π1 Gruis from PIONIER on the

Just one of these granules would extend from the Sun past Venus. The surfaces (photospheres) of many giant stars are obscured by dust, which hinders observations. However, in the case of π1 Gruis, although dust is present it is far from the star so it does not have a significant effect on the new infrared observations.

The Sun’s photosphere, in comparison, contains about two million convective cells, with typical diameters of just 1500 kilometres. The vast size differences in the convective cells of these two stars can be explained in part by their varying surface gravities. π1 Gruis is just 1.5 times the mass of the Sun but much larger, resulting in a much lower surface gravity and just a few, extremely large, granules.

While stars more massive than eight solar masses end their lives in dramatic supernovae explosions, less massive stars like this one – and our Sun – gradually expel their outer layers, resulting in beautiful planetary nebulae. Previous studies of π1 Gruis found a shell of material 0.9 light-years away from the central star, thought to have been ejected around 20 000 years ago. This relatively short period in a star’s life lasts just a few tens of thousands of years – compared to the overall lifetime of several billion – and these observations reveal a new method for probing this fleeting red giant phase.

So it seems there will be a lot to observe on the Sun even as it enters its old age.

PIONIER or the Precision Integrated-Optics Near-infrared Imaging ExpeRiment is an instrument on the Interferometer of the Very Large Telescope. Interferometry is the process of collecting beams of light and combining them together to extract more information and greater resolution from the object being observed. PIONIER can collect up to six beams of light making it incredibly sensitive.

Julien Milli, ESO astronomer at Paranal gives this musical analogy: “the object represents the complete song, and each baseline represents one of the notes that make up the piece. The more baselines we have, the more notes we have, and the more complete our version of the song is.”

PIONIER instrument

Another highlight of PIONIER is its spectral coverage. Adding to the information obtained. For example “…this helps us to characterise the warm dust around a star, providing relevant insights on the formation process,” says Julien Milli.

By using two or more light beams, an interference pattern can be formed with these beams. Because the wavelength of the visible light is very short, small changes in the differences in the optical paths (distance travelled) between the two beams can be detected (as these differences will produce noticeable changes in the interference pattern) meaning more information can be extracted from the light. (This technique is also used in Radio Astronomy.)

How does PIONIER work? It is an interferometer, so once the light reaches the instrument, it is sent across an optical circuit, smaller than a credit card, which brings the light waves from up to four different telescopes together in a very precise way so that they create an interference pattern. An interference pattern consists of fringes, i.e. alternative dark and bright stripes with a given contrast between them, so the final result is not a conventional image.

There’s a lot of engineering goes into Astronomy!

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!

The Night Sky May 2017.

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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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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!

 

 

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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