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About this blog

Real life experiences of a backyard village astronomer.  Another home for the village monthly website astronomy columns too.

Entries in this blog

Owmuchonomy

Every Autumn our local pub organises a charity auction evening.  As one of the lots I offer a voucher for 'An evening of Astronomy'.  This blog shows the outcome of the last winning bid as posted on the local website, warts and all.

Cashing in on photons

 

A short article on an outreach at the Bishop Monkton observatory

 

Sunday the 22nd of October 2017, a week after the annual auction at the Lamb and Flag, the owners of the Astronomy Evening voucher from 2016 made it to the observatory.  It may have taken a year to arrange but that’s nothing to the 2.3 million year old photons hitting our eyes from M31, the Andromeda galaxy.

 

M31.jpg.4f5bc898e84d4a62cfca6cba92aeb0d9.jpg

The author’s own image of M31, the Andromeda galaxy.

 

This was just one of the sights I was able to show to my guests, Carole, David, Stancey and Olly.  What great companions they were too being very patient as I waffled on about the secrets Andromeda gave up to Edwin Hubble and the scientific community in the early 1920s.  Showing the attentive audience how to star hop just with their eyes from the great square of Pegasus to a large fuzzy patch overhead was all it needed. Until then most astronomers believed everything we could see was contained within our own galaxy, the Milky Way.  How much further from the truth could that have been, as we now know it is merely in our backyard in astronomical terms.

 

Testing the sky was also on the agenda for the evening and the conditions were such that we could just make out the seven main stars of Ursa Minor with normal vision.  That equates to a magnitude 5 sky so not too bad but how much better it could be without all the untamed light around us.  Olly, pointing at the Pleiades, remarked that he always thought that was Ursa Minor. An open cluster, number 45 in Messier’s catalogue, known as the Seven Sisters or Subaru in Japan is a very young, close group of hot white/blue stars formed from the same cloud of gas.

 

M45.jpg.dc391768fbea8957e2c6888810427c39.jpg

 

The author’s own image of the Pleiades (M45).

 

We had to crack on though and put to use the short, telescope driving lesson undertaken under red light and over a glass of wine earlier in the kitchen.  I wanted to make sure we didn’t miss a chance to view M13, the Great Hercules globular cluster before it sank below the rooftops.  It proved a bit of a tough nut to crack because to get the most out of it we had to use a technique called averted vision.  David realised that the large fuzzy ball in the eyepiece was made of thousands of stars, bound together by their own gravity like a swarm of bees around a honey pot.  These 12 Billion year old stars though take us back to the very start of the Universe.

 

M13.jpg.cee8f567bd3966ec7fd2802a755b6924.jpg

M13, the Great Hercules globular cluster (Wikipedia commons credit; rawastrodata.com).

 

It was time to move on to some other deep sky objects so we dipped into the space between Perseus and Cassiopeia to sample the double cluster that is pretty in itself but I wanted my audience to look a bit deeper.   Our eyes are poorly equipped compared to cameras but obvious to all is a rich, orange star apparently visiting the cluster of younger members. 

 

Colour tells us so much about a star and so we chased Cygnus the Swan across the Milky Way with both ‘scopes to pinpoint Alberio, the star designating the swan’s head.  In the ‘scope everybody detected Alberio as two stars of sharply contrasting colours, an optical double, often described as indigo and gold telling us immediately that they have markedly different surface temperatures and characteristics.  Are they gravitationally bound as a binary system? Well the jury is out on that one but current estimates have one third of all stars in the Milky Way to be true binaries.

 

Getting towards the end of the evening it was time for a couple of more challenging objects.  Number 57 in Messier’s catalogue is described as a planetary nebula purely because when viewed in the 18th century it resembled a view of the know planets, small, round (ish) and some colour.  These objects have nothing to do with planets but are the result of the after effects of a dying star that has puffed off its last layers of gas leaving a white dwarf at the centre.  The gas is energised by the radiation from the star and takes on colours that are determine by its composition, very often the green of triply ionised oxygen.

 

M57.jpg.a243e944fd40aacccdc5ca5f8687081f.jpg

M57, the Ring nebula (NASA/ESA public domain)

 

I tried hard to answer and fulfil the questions and requests from my guests and one of the first queries raised before we left the kitchen, was “Can we see any planets?”.  Unfortunately it’s pretty poor times in the UK right now for the top targets and will be for some time.  However, the two ice giants are in the southern sky so in theory are visible but crikey they are a long way off. 

 

With Olly’s help and whilst the others warmed up in the kitchen we changed to my old Schmidt Cassegrain telescope that has a focal length of 2.3 metres to attempt this feat.  This also meant realigning the telescope mount. That took a few minutes but it was then possible to pick out Uranus, which is about 4 Earths wide at a distance of nearly 3 billion miles! It is obviously a disk that has a slight green tinge.  We also tried to view Neptune, which is a massive 4.5 billion miles away but the view was slightly obstructed by my roof!

 

Uranus.jpg.8ec472d3dd9ec5d3905647e75f4818a1.jpg

Uranus and Earth comparison (NASA public domain).

 

Visitor comments

 

Carole kindly remarked about the group’s experience of the evening and her words are below.

 

“We had been looking forward to this evening ever since we bid for it in the auction. It took a while for us to find a time that was good for everyone and for the skies to be clear and not moonlit.  It was well worth the wait and a huge thanks to Chris for offering the event and putting on such an amazing evening. 

 

Having only a very limited knowledge of astronomy, it was great to have Chris enthusiastically explaining to us what we were seeing.  He has an array of different telescopes and he patiently set them up in his observatory for us to get the best view of the various stars and planets. Seeing the telescopes and learning about how they are controlled to lock onto coordinates in the sky is fascinating in itself. 

 

Chris has already described above the range of astronomical bodies we focused on in just a couple of hours. Before the evening I don’t think any of us had heard of Messier’s catalogue! There is just so much to observe and it was a treat to see two remote planets. Neptune was a bit naughty trying to hide behind the house chimney but we just about saw it. We also saw Uranus, which was a bonus. Everything else was good to see and the evening was very enjoyable so we hope to see some more at a future date.”

Owmuchonomy

Chris’s Backyard Astronomy.  January 2017.

 

A view beyond Earth’s lifetime

 

Happy New Year to everyone.  This month I am going to concentrate upon one topic only; something that came to my attention at New Year.  The item in question is described as a QUASAR and makes a year in my life appear extremely insignificant.

 

Eyewitness report:

 

“Almost Older Than Time. Would we be able to see it?

 

On Monday the 2nd of January we gathered in Chris's back garden observatory to spot a tiny pinprick of light that had been travelling 8 billion years, yes that's right 8 BILLION YEARS to reach us!

Chris had done his homework, mapped out its position and identified a few pointer stars to help us in our search. The bright moon and lovely Venus stayed handily behind the house so a reasonably dark, clear sky helped us in our search.

Our luck was in, the pointer stars in the shape of a triangle were in the (telescope) field of view and using averted vision I spotted our faint target, impossible to grasp the enormous distance through space and time the photons from this QUASAR had travelled. Once spotted it was easier to see it again as we all took turns to look at this black hole in action; a successful night, thanks Chris.”

Susan Feist

 

Quasi Stellar Radio Sources (QUASAR)

 

The name was adopted originally because such objects were first observed by ‘seeing’ their radio waves and so they were assumed to be stars.  Remember, telescopes are not just available to see things with your own eyes but some are capable of detecting lots of other forms of energy.  The Jodrell Bank telescope near Manchester for example was once the greatest radio telescopes in the world.

 

Jodrell_Bank_Observatory_MMB_11.jpg

 

Jodrell Bank Radio Telescope: Image credit mattbuck

 

Up until the 1960s a multitude of radio wave sources out in the sky were listed and catalogued.  Critical to identifying these objects were to accurately log their precise position and then try and get identification too with a powerful visual telescope.  This proved possible in some cases and as a bonus it was possible to catch the light and determine the spectrum of the object (see my previous column).  Once you have the spectrum you can find out a lot of important information.

 

However, visual recognition and thus scientific interpretation of some of these QUASARs eluded astronomers.

 

3C 48

 

I quote a lot of numbers and acronyms but really it’s not that complicated. QUASAR 3C 48 was the 48th entry in the 3rd Cambridge catalogue of radio sources.  In 1960, using a huge 200 inch telescope, astronomers Sandage, Matthews and Bolton finally pinned this particular radio source to a 16th Magnitude star.

 

P200_Dome_Open.jpg

 

Mount Palomar 200-inch telescope. Image credit: Coneslayer at English Wikipedia

 

A refresher on magnitude

 

Remember, the magnitude scale works counter-intuitively in reverse. Each step is a change of about 2.5 times in brightness.  For example, to us the full Moon looks about 60,000 times brighter than the bright star Vega. On the other extreme QUASAR 3C 48 is about 10,000 times DIMMER than the dimmest star we can see with the naked eye!

 

Object

Magnitude

Brightness we see on Earth

The Sun

- 26

Midday Sun

Full Moon

- 12

Moonlit sky

Venus (now)

- 4

Bright evening ‘star’ (now)

Jupiter

- 2

Yellowish star like

Vega (bright star)

0

5th brightest star in the sky

Yildun

+ 4.5

Star just visible with your eye

Neptune

+ 8

Farthest planet appearing reasonably bright in a 10 inch ‘scope

3C 48 QUASAR

+ 16

At the limit of a very large amateur ‘scope

 

Capturing the light from the QUASAR to enable a spectrum to be examined was some feat in those days but they did so.  Sandage though was quoted describing the spectrum as “exceedingly weird”.  What followed was a 3-year period of doubt and false reasoning because the spectrum just could not be interpreted within the range of known objects.

 

In 1963 two other scientists, Schmidt and Greenstein, re-examined the spectrum of 3C 48 from 1960.  Schmidt had previously examined a spectrum of a similar object (3C 273) and was thus experienced in these matters.  What he immediately concluded was not weird but that object 3C 48 showed a “redshift of 0.37”. So, now we need a recap on redshift.

 

Hearing an ambulance

 

Recall the last time you stood by as the ambulance sped towards you and then away from you.  We are all familiar with characteristic change in pitch of the siren.  As it approaches you the pitch gets higher then as it leaves you the pitch gets lower.  The lowering of the pitch as the sound source moves away from us is due to a ‘stretching’ of the wavelength caused by the speed of the ambulance relative to us. This is the Doppler effect and applies to all types of radiation including light.

 

Redshift_horizontal.png

 

Normal spectrum above and red-shifted spectrum below.  The tell tale absorption lines are moved to the right.

Credit: Georg Wiora (Dr. Schorsch) via Wikimedia Commons

 

So Schmidt was saying that the spectrum of QUASAR 3C 48 told us that it was (and still is) moving away at truly phenomenal speed! As we have discussed before, the painstaking work of Edwin Hubble in the 1920s enabled a connection to be made between the speed that an object is receding and its distance.  On doing the maths 3C 48 was located at 4 BILLION LIGHT YEARS distant.

 

Ancient photons hit Bishop Monkton

 

This dramatic distance estimation created disbelief in the astronomical community.  Knowing how bright the object looks to us (Magnitude +16) and also knowing its distance, enables us to quite easily determine its true brightness close up and thus its power.  The calculation for most QUASARs shows they have the luminosity of 10 Trillion (10,000,000,000,000) Suns, easily one of the most energetic objects in the Universe!

 

As you may imagine this stimulated a decade long argument as to whether the observations were true or were these QUASARS just objects in our own galaxy that demonstrated weird physics?  In more recent times, advancements in technology have enabled astronomers to study ‘normal’ galaxies in the region of these QUASARS and confirm that indeed they are very distant objects.

 

On the 2nd January 2017 a group of villagers and friends congregated in my humble shed known as the Observatory and eventually, one by one caught a glimpse of light that has taken 8 BILLION years to get here.  I stumbled across a reference to QUASAR 4C 11.69 also known as CTA 102.  It is in the constellation of Pegasus looking west from the village at the moment.

 

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The old 9 inch SCT telescope used to spot the QUASAR

 

This particular QUASAR was originally falsely classed as a magnitude +17 variable star.  Variable stars are quite common but are usually quite regular in their variability.  Not this one!  Recently its magnitude has changed from +17 to nearly +11, which is an increase in brightness of 250 times.  Think about this for a moment.  This is an object that is TWICE the age of the Earth, more than half the age of the entire Universe as we know it and visible in my 9 inch telescope.  Surely this is the most powerful and most distant visible object any of us will witness.

 

Its brightness currently varies quite substantially on a daily basis so what is it?  CTA 102 was discovered in the early 1960s from its varying radio source but was laughingly thought to be signals from an extra terrestrial intelligence and American folk rock band The Byrds wrote a song about it in 1967 called ‘Younger Than Yesterday’.  It is in fact a giant black hole at the centre of a distant elliptical galaxy and its brightness is determined by what it is currently consuming.  So the recent huge increase in brightness is a burp of cosmic proportions quite possibly as it gulps in stars or even other galaxies.  I write this in the present tense but it is highly likely this object ‘died’ eons ago and no longer exists.

 

600px-Black_hole_quasar_NASA.jpg

 

A QUASAR; a disk of stellar material feeding a huge black hole and artist’s depiction of data via NASA’s Spitzer and Chandra telescopes. Credit: Nasa JPL

 

The village group found it a challenge to observe but with careful attention to excluding all other light sources and using averted vision I believe all present witnessed the 8 BILLION year old photons.  Retiring to the kitchen to consume a well earned cuppa, some of us had another peek about an hour later and it had significantly increased in brightness in that time so obviously it had done similar to us.

 

What next?

 

A few days later, from the observatory I captured a star field image to show the QUASAR CTA 102 here in the centre of frame against known reference stars.  This is a stack of 20 x 30 second exposures.

 

CTA 102s.jpg

 

QUASAR CTA 102 approximately Magnitude 12. 8th January 2017; Chris Higgins

 

CTA 102 is now going out of reach. If it is still belching at the same rate in the Autumn we should check back then to see if it has satisfied its hunger.  Feel free to join me. 

 

Follow my Twitter feed for regular updates on this and new topics from the backyard observatory.

 

Twitter: @owmuchonomy

Astrophotos:

https://www.flickr.com/photos/blue5hift/sets

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