Archive for August, 2010

America…

Posted in Amusing with tags , , on August 28, 2010 by davidnm2009

…is apparently a place where you see things like this:

It’s a miniature Stonehenge that also apparently doubles as a water feature. I haven’t yet managed to make up my mind whether this is cool, weird or just slightly sad!

I saw this at a shopping centre that’s close to the place where I’m staying, and couldn’t resist taking a quick photo. (I know it’s a rubbish photo…)

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Varied Landscapes

Posted in Personal, Speculation, Travel with tags , on August 28, 2010 by davidnm2009

I’m at the beginning-stages of time-zone confusion, so this may be somewhat incoherent. But here goes anyway…

Today’s been, umm, rather odd. I’ve been travelling, to go to a conference. I’ve travelled rather a long way, as it happens. I’m typing this post from Seattle, rather than Stevenage. It’s fair to say that it’s not very much like Hertfordshire!

And I saw some rather amazing things from the plane.

I’d never imagined this, but it turns out that clouds actually cast mirror-like reflections on the sea. I was quite startled to see this – there was a great big fat puffy stormcloud, with a shiny reflection underneath it! It must have been miles wide, and so was its shadow.

The plane I was on went over Iceland at one point. I saw one of the ice-caps. It looks oddly similar to photos of the southern polar cap on Mars. (No, seriously, I thought it did…) It had a similar sort of pattern of contour-like striations.

Later on, the plane went over Greenland. That was dramatic. There were barren, rocky peaks, icebound inlets and glaciers below us. It looked incredibly harsh, and incredibly hostile. Then, as the plane moved in over the island, the peaks subsided under a dead-white sheet of ice. We presumably didn’t go anywhere near the relatively-fertile bits of the island (the southern coast) as I didn’t see one hint of green down there.

I did have a thought, though – the surfaces of the icy moons of Saturn and Jupiter. Dial down the sunlight and take away the blue sky, and they might look a bit like that.

Next up was the Arctic portion of Canada. I begin to get an idea what they mean by ‘deep wilderness’. There were lots and lots of lakes and lots and lots of rivers, and not a single hint of human occupation. And it took the plane hours to cover the distance.

And then we finally arrived at Seattle, except that it took the plane an appreciable time to fly over it before it reached the airport. Apparently, large city is large.

What Would You See?

Posted in Art, Astronomy with tags , , on August 25, 2010 by davidnm2009

I talked a bit about galaxies and the human eye the other day. On a related note, I thought I’d link to this:

I Wear My Sunglasses At Night – Systemic.

It’s a somewhat-old (2005) post from Dr Gregory Laughlin’s exoplanets-focused blog. But in it, they have a look at what several objects ‘actually do’ look like. It was interesting to see the contras between the Hubble Sombrero Galaxy image and what the human eye would actually see. I was also very surprised to discover that the Cassini images of Jupiter apparently actually are more or less correct – I’d always assumed they were somewhat-manipulated too.

This is the great strength of astronomy, of course. It lends itself to visual representation in a way that’s possibly unique amongst the sciences. It is fundamentally a very visual thing. To some extent everything comes down to imaging, as everything revolves around light in some way. (The only exceptions I can think of are arguably cosmic ray-based work, and maybe neutrinos. But they’re rather exotic.)

Of course, there are occasions when it sadly can’t supply the images we’d like, as well, which can be rather frustrating. I’d very much like to see a T-dwarf up close, but regrettably I never will. (I’m not one of those people who try to claim Jupiter for the T dwarfs, I should add…) I suppose it’s just barely possible that something like E-ELT might – might! – somehow resolve a brown dwarf disk, but I’m not holding my breath.

Lazy, Lazy, Lazy

Posted in Art with tags on August 24, 2010 by davidnm2009

I can’t believe how lazy I am sometimes … I’ve just realised I’ve not uploaded any of these before!!

The Last Tree

This piece (larger version here) was done for a contest on dA. Unsurprisingly enough, it didn’t win, but it was still fun. The theme of the contest was the end of the world. I got bored of all the generic, vaguely-Christian stuff that was getting knocked out, so I decided to apply astronomy to the brief. Here we have the Earth of 5 billion years hence. The Sun, as you can see, is now on the very cusp of red giant-hood. Silhouetted against it is the fossil remains of the last ever tree (which would actually have died millions of years previously). The reddish stuff in the sky is actually plasma ejected by the Sun – the Earth no longer has an atmosphere by this point.

Falling

Poor, poor ‘Falling’. No-one ever looks at you, and hardly anyone looks at the painting that you’re a panel from (‘Shadow of the Traitor’). Which is a real pity, as I all but busted a gut doing it. I mean, there’s even a face! (And it only gets as many views as it does because it’s a 40K piece, as well.)

And yes, the gas giant is actually a brown dwarf. Presumably it’s a very late-T, since only a few bits of it are visibly-glowing. Maybe T8 or T9?

Halo Brown Dwarf

And that brings me onto this piece, which is something I did for a talk a few weeks ago. It’s meant to represent the objects that I study – brown dwarfs in the galactic halo. This is a figurative depiction rather than a strictly-literal one – the Milky Way is rather brighter than it would actually look, for instance. However I wanted to try and get the idea of out-of-plane and highly-inclined orbits, which is kind of the whole point of the stellar halo. I also wanted to work the idea of its great age in there, but I wasn’t quite sure how. There’s a higher-res version over here.

How Far Can You See?

Posted in Astronomy with tags , , on August 22, 2010 by davidnm2009

Further than you might think, is the answer. It isn’t exactly clear where the cut-off is, but it’s certainly more than 3 million light-years out.

We know this because of galaxies. Galaxies … the Universe is full of them, but which can you see?

Well, straight off, you can see our own. Look up on a dark, clear night and you’ll see a murky, silvery blur running across the sky. This is the Milky Way. You see it as a fat line because our Sun orbits close to the plane of the galactic disk, and thus you’re looking straight into the ‘fat’ bit.

What about further afield?

Well, the next most obvious ones are the Small and Large Magellanic Clouds. They’re so-called because the first Western explorer to report seeing them was the Portugese navigator Magellan, in the 16th Century. The Clouds, sadly, are southern-hemisphere objects, and quite invisible from the northern hemisphere. What they are is two so-called ‘dwarf’ galaxies, and in fact they are in orbit around ours. Effectively they are ‘moons’ to our galaxy. They’re also much smaller – both are less than 15,000 LY across, compared to ~100,000 for our own galaxy. They also contain rather fewer stars – the total mass of the so-called Large Magellanic Cloud, for instance, is about 1/10th that of our galaxy. The Small Magellanic Cloud contains only a few hundred million stars, compared to ~100 billion for our galaxy.

The two clouds are magnitude 0.9 and magnitude 2.7 respectively, making them rather bright relative to other galaxies.

The next object should be the Sagittarius Dwarf Galaxy. However it’s relatively faint, with a magnitude of 4.5. Also, there’s some discussion about whether it still counts as an independent galaxy – you see, ours is currently eating it. It orbits close to the Milky Way – in fact, its orbit actually takes it through the stellar disk of our galaxy. And every time it passes through its voracious neighbour, it loses some stars to us. (In fact, on occasion, entire globular clusters have been accreted from our unfortunate neighbour.) The Sagittarius Dwarf was only discovered as recently as 1994 – paradoxically its close location makes it hard to resolve from the galactic stellar background. (‘Is that blob a galaxy or ‘just’ a halo stream?’)

Moving away from the Sagittarius Dwarf, we come to the Andromeda Spiral.

Andromeda is an easy case. It’s the next big galaxy in the Local Group. In fact, it’s bigger than ours. Andromeda is located at a distance of 2.2 million LY (or thereabouts). Recent estimates by the Spitzer Space Telescope suggest that it contains around 1 trillion – 1,000 billion – stars, as opposed to perhaps 200 billion for our galaxy. Oddly, though, it’s not actually that much more massive. Mass estimates range between 20% heavier than our galaxy to about it being about equal mass-wise. (Presumably this implies that Andromeda is preferentially forming smaller, lower-mass stars, although why that might be escapes me.) Andromeda is reasonably bright, with a visual magnitude of about 3.4ish. You can see it from any dark-sky sight, as a faint thumb-sized smudge in the sky. (What you’re seeing is actually the galaxy’s core. The entire thing would be six times bigger than the full Moon, but the disk itself is too faint for us to see, sadly.) The Andromeda Spiral is old knowledge – recorded observations go back to the year 964, and it will certainly have been seen long before that.

(A brief aside at this point: The galaxies preceding this point are the only ones in the sky to show blue shifts. They’re moving towards us, not away. In the case of the Clouds, this is just orbital motion. In the case of Andromeda, it may actually be on collision course, dependant on radial velocity. If it does pay us a visit, though, it won’t be for another billion or so years, and by then solar expansion will have made the Earth uninhabitable, so this is Not Our Problem.)

Moving beyond Andromeda, things get hazy.

There are plenty of galaxies out there, but millions of light-years is a long way, and the light is very dispersed by the time it reaches us. The human eye gives up somewhere around magnitude 6 in most people, but it is possible sometimes to see things that are fainter. These require two things; exceptionally dark skies and exceptionally-good seeing conditions.

Beyond Andromeda, the next object that can sometimes be seen is the Triangulum Spiral. The Spiral of Triangulum is another spiral galaxy, like ours and Andromeda. It’s one of the ‘big three’ that dominate the Local Group. It’s currently around 3.3 million LY away from us. It’s rather smaller than both us and Andromeda – current estimates suggest about 40 billion stars. Triangulum has a magnitude of 5.72, which is getting a bit marginal. Although that is technically within reach, any cloud cover or sky glow will quickly obscure it. For this reason, Triangulum is sometimes used as a test of sky conditions. (If you can see Triangulum, then conditions are good!)

Now I’ve mentioned +6 magnitude as a hard limit. This is a bit deceptive. If you can combine moderate altitude with great, great distance from brightly-lit urban areas, then in fact the eye can just about scrape up to magnitude 8. (This is more impressive than it sounds – each magnitude interval is ~2.5 times fainter than the one before it, so mag 8 is actually 6.25 times fainter than mag 6.)

There are a few objects sat on this borderline. Bode’s Galaxy – another spiral, this time at 11.8 million LY – presents a magnitude of 6.94, and some people have claimed to see it. Also there are claims for Centaurus A, at magnitude 6.84. Centaurus A is a particularly-interesting object, as it’s believed to be the origin of some cosmic rays. There is also a claim for the Sculptor Galaxy, although I have to say I’m not sure I believe it. Magnitude 8.0 is very faint. I think it’s fair to say that this object will only be a possibility for people with near-perfect eyesight, under near-perfect conditions. (Sadly, that rules me out.)

But nonetheless, one thing is clear. The human eyeball can receive and respond to light from millions of light-years away. Given that the eyeball evolved here on Earth, and presumably never ‘needed’ to see beyond the next valley, I think this is pretty damn amazing.

Rho Aquilae: A Not-So-Proper Motion

Posted in Astronomy, Space with tags , on August 20, 2010 by davidnm2009

There’s a famous building in Exeter, presently located off of Fore Street. It was built some time in the 15th or 16th Centuries, but found itself under threat in the early 1960s from a new road development. In 1961, rather then have this listed building demolished, the Council paid to have it moved. And move it did; the entire house was put on a timber cradle and shifted 70 metres to the bottom of West Street. And there it remains to this day. (There’s a video of the move here.)

One of the occupational perils of astronomy is people wittering about their star signs. Unfortunately, to an astronomer, constellations are next to useless. You see, people tend to assume that stars are like houses – they don’t move. But, as we just saw with Number 16 Edmund Street above, every now and then houses can do exactly that, so the common sense approach is not the whole story.

In fact, unlike most houses, stars are moving all the time.

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The Obelisk…

Posted in Art, SF, Space with tags , , , on August 19, 2010 by davidnm2009

…is here.

The glowing letters haven’t come out as well as I’d hoped, but overall I’m reasonably happy with this one. (This isn’t the first obelisk that I’ve painted, either.)

I’ve had globular clusters on the brain lately – with or without weird alien spires.

A higher-res version is over here, as ever.