Kestrel hovering in the Malverns

Kestrel hovering in the Malverns

Until yesterday, I had had little success photographing kestrels – and certainly not when they were on the wing. But there is a family of five in the Malverns which are very active and readily visible, either darting around or hanging, hovering, in the air.

I first saw them last weekend, but conspicuously failed with the camera. They were there again yesterday, and last week’s failures provided good experience of what not to do.

I was there for over an hour and could have stayed longer, marvelling at their mastery of the air, and enjoying an extraordinary photographic opportunity.

Hanging in the air: kestrel in the Malverns

Hanging in the air: kestrel in the Malverns


Surveying the scene

The kestrels almost appeared to be hunting together: though probably more in the way of parent teaching its kid

The kestrels almost appeared to be hunting together: though probably more in the way of a parent teaching its kid

As well as hovering, the kestrels frequently dashed from one hovering point to another

The kestrels frequently dashed from one hovering point to another

Eventually I decided to move on as I was keen for a walk as well.

Later, seeing a buzzard, I thought it would be a much more difficult challenge, as they are constantly in motion as they soar and thus beyond the capabilities of my slow-focussing camera.

Almost at that moment, it moved towards me, and then stopped and rested on the thermals. Perhaps being used to the presence of humans in the Malverns, it was unperturbed by my pointing a camera at it – and secured my best-ever buzzard shots (even exceeding Monday’s efforts!)

This buzzard hung in the air long enough for me secure some good photos.

This buzzard hung in the air long enough for me secure some good photos.

The idyllic Loch Ruthven and its Slavonian grebes

Loch Ruthven  - a beautiful and tranquil reserve near Loch Ness

Loch Ruthven – a beautiful and tranquil reserve

Last week I spent some time at an idyllic nature reserve – Loch Ruthven, situated near the northern end of Loch Ness. It’s home to one of Britain’s rarest breeding birds, the Slavonian grebe, but other notable birds can drop in at almost any time, as I found even while I was watching.

Osprey at Loch Ruthven

Osprey at Loch Ruthven

On the Tuesday morning I arrived just after dawn. After a while, an osprey (which had been seen the previous day) started patrolling the lake, before perching in one of the trees on the opposite side. However, I did not see it try to fish.

Black-throated diver at Loch Ruthven

Black-throated diver at Loch Ruthven

Nevertheless, this was not the day’s most exciting discovery! As I was scanning the lake with my scope, I spotted a bird that was swimming through, serenely and majestically, and could hardly believe my good fortune – it was unmistakably a black-throated diver!

Although it is also one of Britain’s rarer breeding birds, its significance for me was more personal. When I was a kid, Dad had been desperate to see this species, and had instigated a futile chase to try and see one – only for Mum to spot one on a loch just off the main road! (Story here) I’d planned to go looking for it later in the week, so for this one to drift in at Loch Ruthven was most exciting!

Slavonian grebe pair

Slavonian grebe pair

Nevertheless it’s the Slavonian grebes that are the main attraction on the lake – and with their chestnut and black coloration and bright yellow ear tufts, it’s not hard to see why. Like most grebes they are very watchable, with plenty of antics that are intriguing and entertaining.

A pair had taken up residence close to the hide, but their nest platform had been destroyed by waves on the loch – so earlier in the week they were fairly distant.

On the Saturday, I suspected things might become more eventful when I heard the male calling for its mate – a plaintive mewing sound. I was puzzled, as I thought they had already paired up, but there was at least one other grebe in the area, which may have complicated things.

Little grebe at Loch Ruthven

Little grebe at Loch Ruthven

Then the grebe became territorial, heading towards one of the sedge beds, where he proceeded to eject three little grebes from the area. (Yes, three – clearly their world wasn’t straightforward either!). Thus triumphant, he swam towards the middle of the lake – whereupon the little grebe pair snuck in behind to reclaim the area they’d been ejected from!

The male Slav grebe re-united with its mate, and to celebrate they went through their extraordinary and beautiful courtship display: it felt a privilege to be able to watch them in action.

The Slav grebes during one of their courtship displays

The Slav grebes during one of their courtship displays

Nevertheless I was puzzled as to what they were going to do for a territory; and thought this was a mystery I was unlikely to see resolved as I planned to leave late morning. I was about to pack up when I noticed the pair steaming across the lake, heading straight for the sedge beds. They soon busied themselves gathering nesting material – in a different area to the one where the male had been fighting the little grebes.

Gathering nesting material

Gathering nesting material

They gave up shortly afterwards though – presumably to return to the task later.

With the tranquil beauty of the lake and its environment, and the birds which either live there or pass through, Loch Ruthven has become my favourite nature reserve – narrowly squeezing past Greatham Creek!

Slavonian Grebe at Loch Ruthven

Slavonian Grebe at Loch Ruthven

Why I don’t believe in black holes

Hiding a heresy can be hard. I’ve been doing a few science-faith talk here – and somehow or other the shocking news slides out, that I don’t believe in black holes. This may seem strange as black holes frequently appear in the science news (for example here and here). So I thought I should explain why.

It’ll probably help to start by focussing on a prime example of a ‘black hole’ system.  The image below is an artist’s impression of what’s happening in Cygnus X-1: there’s a large, luminous, blue star that produces most of the visible light – but the x-rays largely come from an ultracompact object which is orbiting it. This object draws material off from the blue star, which swirls in a disk before eventually being dragged into the centre – some of which is then fired outwards via jets.

Cyg X-1: a black hole system in our own galaxy.

Cygnus X-1: a black hole system in our own galaxy?

The importance of this particular system is that the mass of the compact object can be measured (Kepler’s laws of planetary motion enable one to do this straightforwardly). It is about 15 times the mass of the Sun [ref]. This mass is essential to understanding what the object might or might not be: it means, for example, that it can’t be either a white dwarf or a neutron star – both of which would be much lighter. Let me explain.

A compact star is formed at the end of the life of a normal star. All normal stars, like the Sun, are giant nuclear fusion reactors: most burn hydrogen into helium, others (the red giant stars) burn helium into carbon, or carbon into other heavier elements; but whatever the fuel, it will eventually run out. At that point the core of the star will collapse in on itself. What happens next depends on how big it is.

The Sirius system: the bright main star, and the white dwarf

The Sirius system: the bright main star, and the faint white dwarf to the lower left

Most stars will end up as white dwarfs. The Sun certainly will, and the faint companion of Sirius (see opposite) is a nearby example. In this type of object, a star the mass of the Sun is compressed into an object the size of the Earth (which has one-millionth the volume), so that a thimble-full of material will weigh several tonnes.

However, because of the quantum properties of white dwarf material, there is a maximum mass for such a star: it’s 1.4 times the mass of the Sun. If it’s bigger than this, it will form a neutron star, an ultracompact object in which a star the mass of the Sun is compressed into a volume which is about ten miles across. The best known examples of these are the pulsars, such as the one in the Crab Nebula [here]. Astronomers know most about those which appear as pulsars, or those which are in binary star systems and whose effects can be seen in other ways. But there’s a maximum mass here, too: it’s about three times the mass of the Sun.

So what about a compact object like in Cygnus X-1 which, at 15 times the mass of the Sun, is comfortably bigger than these limits? The standard answer is that it becomes a black hole. But there is a hidden assumption: this is that nothing denser than neutron star material can exist, so if an ultracompact star is heavier than a neutron star, it must be a black hole. This assumption was excusable in the 1960s, when there really weren’t any other, denser forms of matter known – but not any longer.

For example, there is a substance called Bose-Einstein condensate, which has been manufactured in laboratories [ref]. Unlike the material that makes up white dwarfs and neutron stars, this substance does not have a maximum mass. Consequently, a small number of theorists have considered this material as the basis for an alternative to black holes, which they call gravastars.

Particle physicists get excited about a substance called quark-gluon plasma, which has been produced at particle accelerator laboratories [ref]. It’s believed that this state of matter existed for a few microseconds after the Big Bang, before the universe cooled enough to form protons and neutrons. One Indian physicist, Abhas Mitra – a self-proclaimed heretic who is a bit too gifted to be easily ignored [ref] – has developed a theory that quark-gluon plasma balls form instead of black holes [ref].

In both cases, the main problem is that it would be exceptionally difficult to be able to show observationally that a compact star is a gravastar or a quark-gluon plasma ball as opposed to a black hole (or vice versa). But perhaps the burden of proof is the wrong way round: given the existence of such material, shouldn’t it be necessary to demonstrate that black holes do exist, rather than to assume that they do because objects exist which are larger than neutron stars?

So that’s why I’m a heretic about black holes!

Update July 2017 – I was gratified to read a New Scientist feature article from July 12 which presents the argument that black holes might not exist…

Barber shop theology

I was chatting with the barber while having my mop chopped, and happened to mention what I do for a living. Immediately, he grabbed one of the morning’s tabloids and showed me a headline that had appeared, “Church ‘is on brink of extinction'”. The article was provoked by a talk given by the former archbishop, Lord Carey, to a group of churches in Shrewsbury.

This sparked a good discussion: I mentioned the new ways of doing church in this area, such as cafe church in Wichenford, and the thriving churches in the centre of Worcester (for example, here). He then recalled a conversation he’d had recently: “I was standing with my wife, and said to her ‘here, what does this mean, Hallowed be thy name?'”.

He was genuinely puzzled, but I assumed that the question was rhetorical. Instead, he turned to the rest of the room – two other barbers and a handful of customers – and repeated the question, adding “do any of you know what it means?”. All of them denied knowledge, with one barber quipping, “I thought it meant, ‘How loud can I say your name?'”.

The question illustrates how the traditional church became detached from the wider community. The barber – aged about 60 – is from the generation which, we’re often told in certain church circles, need the re-assurance of the traditional language, but was himself clearly alienated by it. It is hardly surprising that the church is often perceived to be an institution stuck with antiquated forms of impenetrable language.

I mumbled something about the phrase meaning ‘your name is holy’, and realised that that wasn’t a helpful explanation for a non-church person. I wish I’d known how the New International Readers Version interprets the phrase: “may your name be honored” [NIrV] – which makes the least assumptions about what people would understand today.

I have since discovered that the tabloid concerned – and indeed the subsequent coverage elsewhere in the media – substantially distorts what the archbishop had actually said. The aim of his talk, entitled ‘Re-imagining the church‘, was to inspire and energise a group of churches into radically re-thinking the way church is done; it was far from being a melancholy tirade. He did warn the churches about the danger of neglecting youth ministry, and this is what prompted the comment which was picked up by the tabloid; but ironically, the sentence actually reads (with my italics) “As I have repeated many times in the past ‘we are one generation away from extinction’.” It must have been a slow news day for the newspaper to pick up and distort this comment!

It’s a pity the tabloid concerned didn’t read what the archbishop had actually said; but a greater pity that the church wasn’t properly attuned to these issues forty years ago. Still, the church may still benefit if the headline sparked discussions in other barbers’ shops across the country!

Seen at last! – Little Bittern at Ham Wall

“This is not a memorable wildlife experience”, the volunteer warden stressed as I arrived at the Little Bittern watchpoint at Ham Wall.

I have previous with little bitterns, so this warning didn’t deter me. Some years ago I’d gone down to Shapwick Heath, the reserve across the road to Ham Wall, on a futile bid to see otters (the result of an erroneous tip-off). One evening I noticed a stream of birders going down the tarmac path into Ham Wall. I decided I knew better than to follow the crowd, wandered down a grassy path that became marshy and impassable, and returned none the wiser.

The next day curiosity got the better of me, and I found myself with a group of birders who were saying that a Little Bittern had arrived – which I’d never heard of before, but could see it was the cause of a major twitch. Although it had showed well the previous day, it was now proving to be elusive, so I gave up after an hour or two; besides, I wasn’t about to become a twitcher, ahem.

It hung around most of the summer, calling forlornly for a mate. The next year, it turned up again. Hahaha, silly bird – you might think. Only this time it had a female in tow. This was a major surprise – it was only the second time little bitterns have been known to breed in the UK [news report]

Little Bittern at Ham Wall in 2010, illustrating what you can expect to see on a feeding flight - copyright Tom Mabbett

Little Bittern at Ham Wall in 2010, nicely illustrating what you can expect to see on a feeding flight – copyright Tom Mabbett

I figured out I could look for them on the day off at New Wine. When I arrived, I was told that since the chicks had already fledged, the parents had left the site a week earlier. Since then, the little bitterns have turned up and bred every year, but it has been kept quiet to protect the birds. This year, however, the RSPB announced their arrival, and set up a 24-hour watch on the nest site to protect the birds from egg collectors.

Now that the eggs having hatched, the parents can be seen on their feeding flights, to and from the nest. I decided that on my first day off after the ordination, I would go down. I went down the evening before, which was when the gloomy volunteer warden tried to dampen enthusiasm. No chance!

What makes them so difficult to see is that, like their large brown cousins, the normal bittern, they skulk around reedbeds. But whereas the larger ones can be seen easily when they fly lazily across, little bitterns dash fast, remaining just above the reeds for as short a time as they can manage. However, they have a highly distinctive wing pattern, with a large white elliptical patch on the upper part of the wing (see image above), which means they are easy to identify. [Little Bittern intro and specialist fact sheet]

I arrived at the site again on the Friday morning, at 7am: another birder had arrived at 5:30, and had already briefly seen one of the birds. We stood and stared out. After about half an hour, the male dashed across the reed-tops before dropping into a channel between the reeds. It was brief – a couple of seconds – but long enough for me to see it clearly with binoculars and know that I’d seen a little bittern. Phew!

At the same time, we could clearly hear a male little bittern barking: sometimes faint and distant, at other times rather closer – but always distinctive, repetitive and unmistakable. Herein lay a mystery: they don’t call once eggs have been laid. So why was this one barking?

After a while, the female suddenly emerged from the reeds and flew down the clear channel to the right-hand side of the reedbed, before veering left to return to the nest. Again, enough to see it clearly – and to notice the more muted, brownish colouring.

I missed the male when it appeared an hour later, but after a few minutes it cruised along the channel between the reeds closest to us. It was a marvellous sight: very easy to see the wing pattern, and to admire the bright orangey-yellow bill that it gets when it is breeding. Although it was still only brief, for me it really was a memorable wildlife experience.

Little bittern at Ham Wall in 2009. Image copyright James Packer

Little bittern at Ham Wall in 2009 – copyright James Packer

So why was there a male barking? It is now believed to be one or two unpaired males at Ham Wall, in addition to the nesting pair. The volunteer warden on the Friday afternoon, who had all the enthusiasm that the other one lacked, had heard two males barking simultaneously earlier in the week. The story of little bitterns at Ham Wall looks more likely to grow rather than diminish.

The RSPB are to be congratulated for setting up the watchpoint and co-ordinating volunteer wardens for it. Hardcore birdwatchers know what to expect, and it really was a memorable experience.

I stayed at the Bramble Hill campsite on the south-west side of Walton, which is a short distance from Ham Wall: I highly recommend this site for any birder who wants to camp near the Avalon Marshes. The facilities are excellent, and the owners very friendly and helpful.

The delights of Marloes Mere

Just down the lane from the youth hostel at Marloes is the Mere, a lovely wetland nature reserve. On the Wednesday morning, I woke early and, seeing that it was sunny outside, decided that a quick trip to the Mere would be much more worthwhile than trying to get back to sleep. I was soon rewarded: outside the hide, a sedge warbler loudly and energetically proclaimed his territory, undisturbed by my camera. (He kept at it for fully two hours)

Sedge warbler giving it all his worth

Sedge warbler giving it all his worth

Linnet, posing for the camera

Linnet, posing for the camera

I’d hoped to see a linnet pair I’d seen the previous night but was disappointed… until the male alighted on a prominent branch and posed while I took shots. Linnets tend to be showy birds – but this one took it to an extreme!

The highlight for me came when a dowdy-looking bird arrived in some bushes by the water channel in front of the hide, dashed out to grab an insect before flitting back. A spotted flycatcher! These used to be common birds in the UK, arriving from sub-Saharan Africa in late spring, but their numbers have crashed. They were well known for nesting in gardens – I’ve heard locals in the Martley area say that they had them each year until recently – but now have become scarce. (A couple of years ago I was desperate to see one… see here). The Marloes bird was hard to photograph, until it appeared in some gorse bushes – at which point my finger became clamped to the shutter…

Spotted flycatcher

Spotted flycatcher

Glossy ibis at Marloes Mere

Glossy ibis at Marloes Mere

The site is also known for attracting unusual birds – including a glossy ibis that has been resident for over a year. Indeed, when I was here last time it had three companions, which have since departed. (I wonder what their final conversation had been…) It’s not a great photo, having taken it on a dull Monday evening. (Better shots here)

Later in the day, on my trip around the Dale peninsula, I was focussed more on walking than birding – but had to stop for this stonechat, which was singing to its mate while sitting on a barbed wire fence, while holding something green in its beak. Only afterwards, on looking back through the images, did I find that the ‘something green’ was a caterpillar. It seemed to be bonding with a nearby female which was also prominent and chatty.

Stonechat with caterpillar prey

Stonechat with caterpillar prey

My scientific past

Saguaro cacti near Tucson

Saguaro cacti near Tucson

I’ve just completed a couple of weeks doing talks on science and faith. This included a Lent talk to the church, but I’ve also been doing some talks in the Chantry – the local secondary school in Martley (having been kindly invited by the RE teacher, Mel Palmer).

I’ve started each of the talks with a brief autobiographical account of my involvement in the astronomical world. This is the background for why I strongly believe that Christians who speak about science should at least be scientifically literate. I therefore thought I’d give a brief summary here of my life as an astronomer, with a look at one of the projects I undertook.

I spent just over three years in Tucson, Arizona in the early 1990s, working as a postdoc at the University. I was massively fortunate to have this opportunity – one that I perhaps didn’t quite appreciate at the time as much as I should have done! While there I had about one hundred nights observing, mostly on Kitt Peak, which was then a leading observatory (but has since been overtaken by much bigger ones on higher mountains and in more remote places).

Kitt Peak National Observatory - the telescope I used most is the one in the open dome.

Kitt Peak National Observatory – the telescope I used most is the one in the open dome.

The Burrell-Schmidt telescope - a small, old scope which had fast optics, which was ideal for what I wanted to do.

The Burrell-Schmidt telescope – a small, old scope which had fast optics, which was ideal for what I wanted to do.

The Ring Nebula as viewed by the Hubble Space Telescope. Note the star at the centre, which is becoming a white dwarf.

The Ring Nebula as viewed by the Hubble Space Telescope. Note the star at the centre, which is becoming a white dwarf. Credit: NASA and The Hubble Heritage Team (STScI/AURA)

My main research interest was in white dwarfs and old planetary nebulae. When a star like the sun runs out of its nuclear fuel (thus, after it has burned all the hydrogen in its core, and then burned all of the helium), the core of the star collapses to become a white dwarf. Meanwhile, the outer layers lift off into space, for a while becoming a planetary nebula, one of the most beautiful sights in the sky. One example is the Ring Nebula (shown on the right), which is visible with binoculars, but is spectacular when seen with the Hubble Space Telescope; the star at the centre is becoming a white dwarf.

The closest planetary nebula Sh 2-216, viewed with the Burrell-Schmidt in 1995, filtering for light from hydrogen (technically H-alpha]). Displayed to reveal the brighter stuff.

The closest planetary nebula Sh 2-216, viewed with the Burrell-Schmidt in 1995, filtering for light from hydrogen (technically H-alpha]). Displayed to reveal the brighter stuff – compare with the image below, which is displayed to show the fainter parts. The arrow marks the white dwarf.

Eventually, as the nebula expands, it becomes buffeted by the ambient wisps and clumps of interstellar gas, into which it eventually dissipates. The focus of my research was on those nebulae which were at this stage, of interacting with this interstellar material.

The research which probably gave me the most satisfaction was on the closest of all the planetary nebulae, which has the unglamorous name of Sh 2-216. I first became interested in it when I was studying white dwarfs at Leicester University – and was intrigued that the nebula has been so buffeted by the surrounding interstellar material that the white dwarf is no longer at the centre.

The nebula is very faint indeed, but spans about 1.6 degrees – far larger than any other then known. The telescope I used was ideal for this project, because it had a wide enough field-of-view for the task. I still had to produce a mosaic of images to cover it, but it was very doable.

It’s an indication of how much technology has improved in the 18 years since then that this nebula is now within the range of amateur observers, for whom it is a rewarding challenge. For example, this image is much prettier!

The closest planetary nebula Sh 2-216, viewed with the Burrell-Schmidt in 1995, filtering for the light of ionised nitrogen (technically [N II]). Overexposed to reveal the faint stuff.

The closest planetary nebula Sh 2-216, viewed with the Burrell-Schmidt in 1995, filtering for the light of ionised nitrogen (technically [N II]). The region to the left has been overexposed to reveal the faint stuff, but is shown in the previous image.

The problem with this research field is that the observations are easy but the theoretical modelling is spectacularly difficult – and it’s not quite as glitzy as quasars and distant galaxies! However an unexpected breakthrough came in 2008 as a result of the work of a team of radio astronomers, who were doing the Canadian Galactic Plane survey. They were very surprised to see it all – indeed, they only detected one other planetary nebula anywhere else in the sky – but the reason it was detectable was because of the interaction between the nebula and its surroundings. Ryan Ransom used the data to measure quantities such as the strength of the ambient magnetic field in the surroundings. However, he also emphasised the difficulties of deducing much more – largely due to the difficulties of the theoretical modelling. Nevertheless, the radio data is an important new angle that significantly improves the understanding of the nebula and its environment.

References: Optical; Radio.