Congratulations Bunny/Nathaniel!

I must definitely keep up with the news more often. An old friend from Cornwall, who I knew as Bunny but is now also known as Nathaniel Burton-Bradford, has done some cool enough work to have his pictures displayed and linked to on Universe Today! I only found out because I decided to do some proper work writing about Herschel and M51 on the forum.

Credit: Nathaniel's photostream. Do check out the rest! I've met Frodo the dog. He's very excitable.

The above is the one in the article; there are more of Herschel and other craft in 3D, and many other interesting pictures besides. I wish 3D glasses worked for me, but since they do for other people, I shall be inclusive even if it means excluding myself - haha, was that good enough, political correctness? Just kidding. I'm really pleased.

I can't resist adding this one, which is called "22 degree halo". I have no idea what the "22 degree" bit means - but perhaps we'll be enlightened in Oxford on Sunday! I do, however, remember these haloes turning up a lot in Cornwall. Many years before, during the winter of 2000/01, I'd been living in Warrington, near Manchester, where I was desperately cold. I remember the feeling of the metal mattress springs sucking the heat from my body. I'd put all my clothes on over my pyjamas, wrap the duvet around me like a coccoon, and put my towel and coat on top of it, but still I shivered. The fire gave me a blinding headache within minutes of being switched on (I'm sure it had a certificate for carbon monoxide safety, but everything did regardless of what state it was in). The canal froze so hard that someone chucked bottles and a rock the size of my head on it one morning and the ice wasn't even cracked. In short, I was a lot colder in Warrington than I ever was in Cornwall - but it was Cornwall where I saw those haloes.

Credit: Nathaniel's photostream.

They appeared around streetlights and car headlights in the early morning, as I walked to school in the dark, often before 7am. They looked to me like ring galaxies. They were golden around streetlamps, white or rainbow coloured around cars. And sometimes they'd appear around my bedside light as soon as I'd switched it on - and in its reflection in the mirror. They were beautiful, shimmering with bright colours, and I'd miss them as the sun came up and they faded.

Infinity found me a site to explain that they were light polarization, caused by ice crystals in the air. These crystals are hexagonal and reflect or refract light in a way that water droplets do not. It's interesting that there was ice in the air in warm Cornwall, but not cold Warrington. Anyway, the light effects were cool, and it's great to have an excuse to show them to you even by this roundabout route!

Obsessed? Me?

Never.

Ooooh, had enough suing, eh?

I haven't been covering the Simon Singh case very coherently, especially not the most recent post, because I was too busy howling with laughter to dissect it properly. This time, I won't even try. Just check out Phil's noticeboard pointing towards the general direction of Crispian Jago. I'm going to be up all night trying to reword the Black Knight scene now . . .

By the way, if you're still thinking about coming to Oxford, it's not too late. I meant to book the accommodation today, but will do so tomorrow - so you've missed your chance for being sure of staying where I am! Today I spent playing games on . . . ahem, I mean resurrecting and bringing back into use my beloved laptop, and creating far too many Galaxy Zoo puzzles. My favourite is this crossword. Use both puzzlemaker.com and puzzle-maker.com to create your own! I used these in the classroom and they were surprisingly popular.

Yes, it's one of those seasons. (Can't even say "months".) I really will write something good at some point. Oh yes - to make up for it - one more joke for you. From Wongo the Sane on the Galaxy Zoo Forum . . .

And so, Noah asked all the animals to go forth and multiply, and thus they did, apart from the poor adders whom, according to their nature, could not multiply but only add. But the story does not end there.

For Noah, seeing the adders non-compliant with his rulings, and taking it as disobedience, said once and again to the adders to go forth and multiply, and each time the answer came back negative.

And so, on the third time of asking, Noah, for he was verily ticked off at that point, did lock them in the wood shed until they were successful.

And, lo, the next morning thousands of tiny adders came streaming forth from the woodshed.

There, said Noah, that wasn't that hard now, was it? Why were you not able to do it before?

Well, said the adders, we have told you the problem before. However, once we got into the woodshed the problem was solved. We just used logs...

If you don't like craneflies, screaming hysterically won't get them out of your room - only draw attention to you.

Sorry, but I really couldn't resist that headline. I am cracking up laughing at the Bad Astronomer's latest post - "Chiropocalypse". Drop this blog right now and go and read it.

Back? Laughing too?

Good, let's have a cup of tea.

Somebody very sensible wrote to The Independent, or something like that (I can't remember now), to chastise them for giving Nick Griffin of the BNP the publicity he was after. 2 seats in the European parliament is certainly something to groan and roll our eyes at, and an invitation to say: "Well done MPs. That's what you get for making us pay for repairing your lovers' dryrot and whinging on about how you are only getting six times as much as someone on your celebrated minimum wage, who is lying awake at night wondering how to pay for their kids' childcare while they're punching checkouts against their will." But screaming our heads off won't get rid of fascism, only encourage it. There's nothing more satisfying than knowing you've really frightened and annoyed your opposition. How much is he actually going to achieve? Don't take any notice of him and he won't get so far.

Similarly, the British Chiropractice Association might learn a lesson or two. They have now gone bananas! Witch hunt? Er, who started the witch hunt? You, I think, mate. Somebody points out that you have incorrectly claimed that there is "evidence" that young children's non-spinal ailments can be treated by your profession, and instead of stumping up this evidence like any mature person (let alone doctor or scientist) wouldn't find hard, you have a little tantrum and sue him. Naturally quite a few people are not on your side about this, so now you advise your workers to remove all information about chiropractice altogether, so that any customers thinking of going to you will be even less informed than before. This seems to be a continuation of your girly little "I'm-not-speaking-to-you" stance when the original article appeared - you were invited to write a rebuttal and turned it down!

I didn't even know the difference between chiropractice and chiropody when this started. The scrutinisation, complaints and negative publicity you're getting through your own childish behaviour is bound to set you back far more than Simon Singh's words that hurt you so deeply. Indeed, I do hope your legal fees and lost custom will cost you an awful lot more than you'd gain from any payout you'd get from Simon. In the meantime, I wonder who would actually benefit from that payout? Your practitioners? A spot of research? Hmmmmm. The top executives, I don't doubt. Not that I'm quite interested enough to delve in and find out. I'm too busy laughing, and I doubt you'd tell me.

Well, perhaps I'm being a little unfair. The BCA does seem to be attempting to protect its "doctors", and this makes extremely funny reading. Oooooh, and what a surprise - this is NOT to be discussed with patients! I wonder who naughtily released it?

In the meantime, Sense About Science's campaign is going well! We have a special button now; please click to add your name, and you can download it here:

It's not being ignored, either! As you see below, three politicians - one from each "major" party (pre-European-elections major, anyway) - have signed a statement in our support:
Original page here.

Now, I've nothing new or more informed than anyone else to say on the subject, but I can't resist writing up a few interesting views I've seen written. I've seen a few people remark that this is "scientists seeking to be above the law", and that they'd rather have signed to say that our libel laws are an embarrassment, rather than to protect scientists especially. I can understand this. I don't believe scientists generally seek to be above the law, but they can't be the only unfair victims of this sort of thing. However, as soon as someone is given an exemption to a rule, everyone else will want that exemption too. So I hope this is a good way to start chipping at a block generally - and the wording of the statement of support is encouraging on that front too.

On Jack of Kent's excellent blog, which I'm now following, someone has written an open e-mail to the BCA, detailing pretty much what I've written above about ignorance turning into . Scroll down past all those names to the comments! Jack of Kent (who turned out to my surprise and amusement to be David Allen Green) also details why, no matter how much money they get if they win the case, it's not going to help them in the long run. "A whole range of key opinion-formers are now hostile to the British Chiropractic Association and about chiropractic generally," he writes, then: ". . . [i]t . . . turns an almost-unknown professional body into a notorious bogeyman for scientists and journalists - both here and elsewhere. For the British Chiropractic Association is now a proxy for international dislike of the English libel laws . . ." Also, any complaints - for example to do with advertising accuracy - made against them will now certainly get a very interested public hearing!

Someone in my family said, "Will they care, as long as they get a massive payout?" I don't know. In any case it's certainly put their future on a more interesting course than it would have been otherwise.

Simon Singh himself is a great inspiration to us all. I'm particularly impressed by his statement to the many people who wish to contribute to a legal fund for him that, with three bestsellers out, although he will be poorer if he loses, "my wife and I will be able to cope" - and therefore could there please be a general fund to help Sense About Science and/or the next journalist this happens to. His statement is very thoughtful.

I began reading Ben Goldacre's book "Bad Science" recently, and my favourite bit so far has been the school pupils who wrote in delightedly about their science teachers who would teach them real science once minute and unproven nonsense about "energy flow" the next, due to this new "Brain Gym" phenomenon in schools. (He has an amusing little blog entry on the subject too.) Can I say it often enough? The solution to all these kinds of things is better mainstream science education. Stop viewing science as somewhere between a lot of boring incomprehensible maths and unquestionable magic, and make it something wonderful and reachable to all.

The depressing points people remark on are the niggly little technicalities - for example, that the issue hangs on the use of the word "bogus", whose meaning is seized upon as meaning "deliberately deceitful/harmful". Frankly, I think their refusal to be informative deserves a remark like that, but the point is that Simon now has to prove that that word is not libel, rather than discuss science and evidence and alternative medicine. He doesn't say this precisely, but something like it - it is under the heading "The Recent Disastrous Ruling". He has to prove the accuracy of his statement.

And what really gets me is the guilty-until-proven-innocent method. I think I have gone on, and will no doubt go on, on other occasions about this quite enough, so will leave it there.

In the meantime, I wonder if we could ask the British Chiropractice Association a few questions under the Freedom of Information Act?

Sense About Science

I'm still in a state of aaaaaaargh-ness (no, sadly nothing to do with the Castle Argh), but just a very quick entry here to encourage you all to read this excellent article by the Bad Astronomer. It seems that Simon Singh, a science journalist, dared to criticise the British Chiropractic Association for making unproven claims about their treatment - so they sued him.

Of course, if they had genuine confidence he was wrong, they would have ignored or answered him. However, as they haven't got any scientific evidence, they decided to attack him and try to gag him instead. What a mature response! Even more depressingly, the judge seems to agree with them. The unquestioned might of the corporation versus truth and science. Well, it's rebounded. There is now quite a campaign going, which I've signed. (For "profession" I put "unemployed amateur astronomer". I was tempted to put "starving artist-of-science", but I did feel this was a moment to attempt to be taken seriously.) If you sign, you're stating that libel laws should not come into science - i.e., in this case, businesses which claim to cure ailments have a responsibility to collect evidence to back up their claims, and citizens should not be bullied into silence when they know the claims are unproven.

If Simon Singh is successfully sued, the logical conclusion is that any old flashy corporation could sell poison and claim that it'll make your teeth shine, or your breath smell of roses, or you'll never get a common cold again - and anyone who discovered otherwise could be punished for saying so, and the general public not permitted to know anything.

I used to work in a hospital and every few days there'd be drug companies there, handing out corrosive coffee and leaflets and trying to persuade the doctors to buy their drugs rather than decide what was best for the patient. I have also heard of cases of them offering doctors thousands of pounds not to publish their research on the ill effects of drugs.

C'mon, folks, which matters more, people's health and scientific truth, or some business's money?

(To avoid getting sued myself: like Phil, and indeed like Singh, I am not claiming that all or any chiropracters are deliberately lying about their treatment. But whether the practicioners themselves have faith or not is immaterial: the effects on their patients will be the same.)

As an aside, this paragraph in Phil's article surprised me:

In the US that would be a dumb thing to do, as our libel laws put the burden of proof on the claimant (in this case, the BCA), as things should be. However, the UK is very different: when party A sues party B for libel, it’s up to party B to prove their innocence.

I thought it was worse in America, but perhaps that was just stereotypes creeping in, not to mention hundreds of stories about crazy lawsuits. In any case it sounds rather like the government's attitude to terrorism: the accused is guilty until they can prove themselves innocent - and it's quite all right to detain them, deny them access to a lawyer or even tell them what they're accused of or when they'll be free, and undermine their health and sanity, to prevent them having a chance to prove anything. (As an aside: If you accuse me of having stolen a box of chocolates when I was 13, I can't see any way I could prove that I didn't!)

It reminded me of a comment made about another recent article by Phil, on the subject of mass rapings of small girls. Somebody pointed out that it's traditional language for people to "admit" to having been raped, as if the victims are somehow guilty. That article too is worth a read, by the way.

I've gone off on a tangent, and am not sure now whether this post is about the respect for truth and the nasty consequences of a lack of this, or about the fashion for aggression and blame towards the victim or accused person, rather than the one who started the aggression or accusations. I guess they're all rather tied up together. In the meantime - back to work, and thanks to Pamela and Arfon for squishing lots of bugs on our forum and improving the place a LOT since a week ago!

Update: On the subject of the English libel laws, and for Singh's very restrained and well-thought-out take on what is happening, this is excellent. How embarrassing to learn that a learned lawyer considers that English libel laws are so badly out of sync with the rest of the world, and their automatic support of the accuser makes them so easy to get money out of whoever you like with little effort. I.e.:

As the lawyer David Allen Green wrote in New Scientist: "Once the claimant has established they have a reputation in England, and that there is a defamatory statement, they have an automatic right to bring legal proceedings without having to show any damage has been suffered. It then falls to the unfortunate defendant to prove before the court, often at considerable expense, that the statement was defensible. This is the notorious "reverse burden of proof" which, for many, discredits English libel law."

Lost in the Merging Blues

AAAAAAAAAAAAAAAAAAAARGHHHH!!!!

I have no time to write at the moment. The forum accounts and classifying accounts at the zoo have just been merged, which is causing one or two problems. I can't log in without finding another 7 or 10 or 15 messages in my inbox, even if I only disappear for an hour or so. In fact, every time I refresh the page or look at a new thread, another four messages appear. The indomitable Aida has just started an amazing new project, which I've had to decline to be involved in (sniff, sniff!), but am still acting as secretary and communicator for. I'm now helping Colin at PulseProject find a lot of people to be interviewed about the peas and Galaxy Zoo generally, and organising a meet-up in Oxford. I have a history of maths assignment due in a week - I'd been hoping to write about some of the wonderful and often tragic things I've been learning with the Open University, but I actually have a lot of real work to do as well. And I seem to be travelling and trawling the Internet an awful lot these days!

I hope to be writing about all the interesting items on the above bulletin soon (soon being - whenever I can), not to mention a wonderful visit to Brownsea Island to do conservation work two weeks ago. You just never know where astronomy leads, do you?

The reason the accounts merge is taking up a lot of my time (10 hours yesterday, minus a few breaks), is that I'm the one being asked to make lists of all the problems and keep the team up to date, and also people are used to me being able to solve their problems. But I can't any more! I don't have the access to profiles and data and the knowledge and experience to offer suggestions that I used to. Anyway, presumably the team know what they're doing. And as Galaxy Zoo is, shall we say, growing in quite a few new directions, it is a very fair point that they don't want their regulars to end up with several different accounts to do all the different projects.

Anyway, I just had to post a wonderful song written by LX90MAN, who was made into a ghost of the zoo by the problems:

Woke up this mornin'
And found my body gone
not even my feet and souls
I can't be seen by no-one.

Then I gets to thinkin'
what could I do
I could rich by taking money from you

Cause I'm the invisible man baby
Oh yeah I'm the invisible man baby
you can't see me but I can you
My whole life is in a temporal stew.

I called to Alice to bring me back
now waitin' on Pamela to give me substance jack
I can't take this limbo
it's makin' me insane
this way I even get sat on on an aeroplane.

Cause i'm the invisible man baby Thats right
I'm the invisible man baby
you cant see me but I can you
My whole life is in a temporal stew.

Get Well Soon Merged Zoo:
Credit: SDSS, as always.

Go, Atlantis!

Sorry for the recent silence - Earthly events have been demanding my attention, the most random of which included haring off to Manchester to spend a few hours sticking address labels onto envelopes in a room full of old sofas. For those of you who were wondering, this was an important Speak mailing, and the venue is generally used as a furniture recycling place. Speak was founded at my old university, and is a great charity. I may be an atheist, but I'm proud to be involved with it (and actually I find myself wandering into religious charity events surprisingly frequently, for the simple reason that I admire and like being part of the church's ability to work together and get so much done).

In the meantime, I've somehow started studying the history of maths; we had a great birthday bash for Kevin at the zoo, which led to a permanent zoonometer; and APOD has come up with some lovely galaxy pictures for us.

The Andromeda Galaxy

Galaxies Galore in the Perseus Cluster!

The major news which I've failed to follow properly is the event we've been looking forward to for months: the launch of Atlantis, the Hubble repair service. Stellar has done an incredible job writing that one up, so go and look at her blog to get yourself thoroughly filled in!

Update (having had time to read a bit more of the forum): Infinity and Hanny have also kept us filled in on the forum. I'm glad other people are up with the news, even if I'm not. Nothing like teamwork, eh?

Mini Spinni: The antics of atoms in space

I'd been wondering about emission spectra for a while. To summarise it, what happens is this: electrons exist in "orbits" round atoms. You can think of these orbits simply, like planets orbiting the Sun, or in a more sophisticated manner, as a "wave of probability" of where the electron will be at any given time. There are fixed orbits for the electrons (imagine Mercury being able to jump into Venus or Earth's orbit, but not to a random place in between), and being struck by a photon can boot an electron up into a higher one. This is an unstable, i.e. higher-than-minium-energy state, so at some point later the electron will fall back down again, re-emitting a photon as it does so.

My dilemma was this: if the electron needs a certain amount of energy to move up one or more orbits, and emits exactly the same amount when it returns to its ground state, shouldn't the two cancel out? I.e. why should we see any absorption and emission spectra at all?

I asked our wonderful Chemistry tutor, Tim, this in Brighton two years ago. He told me to think of it as light travelling in particular directions. In the case of absorption spectra, it absorbed it at a particular angle (the light travelling between the source and your eye via it) and radiated it out in a halo, so you didn't really see the re-emitted radiation. And with emission spectra it's vice versa.

Quite by accident I came across some information about hydrogen in space. The interstellar medium is full of hydrogen. Even in regions of "empty" space, i.e. not clouds, hydrogen is present in individual atoms (HI in astronomy notation; a new language to learn after many years of thinking of that as an H-radical). When the temperature is below 100K, or in a denser region, the atoms form molecular hydrogen, or H2, as we find it on Earth. In hotter regions, with starforming activity, the hydrogen is likely to become ionised. In chemistry terms, it is H+ (+ should be superscript!); in astronomy notation, it is HII, or ionised hydrogen. Ionised means that a photon has hit the electron with enough energy that it has knocked it clean off the atom.

So that's the HII galaxies Tom and the zooites are collecting. Hang on. HII emission lines? Emission lines from a proton all by itself, without the electron to be booted up and down any orbit at all? I don't know why I didn't think of it before, but there you go. I asked in the thread, and mukund vedapudi soon came up with the answer. In short, in regions that are hot enough (the vicinity of massive blue stars you get in bright blue galaxies), hydrogen nuclei (protons) and their electrons are constantly recombining as well as ionising. The recombining releases a characteristic emission line just like the Balmer or Lyman series (when the electron drops down to the second and innermost orbit respectively).

But we also detect hydrogen in space with radio waves. How? Photons which fire electrons up into higher orbits need (to the best of my knowledge) to be more energetic than radio waves. Take this picture, from an article about it.

(Credit: sciencedaily.com - the detection of 5 hydrogen clouds in space.)

You can detect hydrogen in clouds and out. In fact there's a specific way to detect cold (but above 100K) lonely HI atoms, because they emit radio waves of 21cm.

I just found out the way they do this. It's to do with spin. I learned enough about that to establish that the Pauli exclusion principle states that no two electrons can exist in the same orbit with the same spin. They can spin one way or the other. That's why you get the s-orbital in hydrogen, and then another s-orbital and three p-orbitals in lithium to neon in the Periodic Table. Each orbit contains room for 2 electrons, provided they're spinning opposite ways.

I hadn't consciously realised that atomic nuclei have a spin as well. But they do. And in the simplest atom we know, hydrogen, which is just a proton and an electron, it's simple enough to keep track of the spin of each. And just like electrons in orbits, when more than one state is available, the system will prefer the one with the lower energy. That is when the electron and the proton's spin are opposite, not equal.

(Credit: odin.physastro)

In a moderately warm environment, not cold or dense enough for H2 to form, hydrogen atoms can collide, the energy of which knocks them into the state of parallel spins. They will later revert to opposite spins, emitting radiation with a wavelength of 21cm. This allows us not only to detect that there is warm-ish, thin, atomic HI about, but also (using redshift) to measure the radial velocity - i.e. whether it is coming towards us, or heading away.

Why doesn't this work for molecular hydrogen? Basically because molecular hydrogen works quite differently. Both electrons are in a hazy cloud of probability around both protons, and the molecule has a great deal more symmetry. This makes dense hydrogen clouds harder to detect (which is probably why it made the news when 5 were detected in the story above). This is also true of most gases, such as oxygen, in space, because they tend to exist in pairs.

Except, for instance, in the important case of carbon monoxide.

Carbon and oxygen have a different number of protons, neutrons and electrons, which makes them behave differently. Oxygen, for instance, is just dying to grab two electrons to fill up its remaining p-orbitals; we call it "electronegative". (In water it is quite greedy and the electrons spend more overall time around it than around hydrogen, which is why water molecules are dipoles.) This means that carbon monoxide will not have that symmetry which insulates it from our beady eyes.

Carbon monoxide undergoes rotational transitions like atomic hydrogen, HI, so we can detect radio waves from it, at the higher frequencies than HI of 1.3 and 2.6mm. It is relatively common in space. Astronomers believe that it is also found pretty much where hydrogen clouds are, so it's a useful tracer for them. For molecules to form, gas has to be cold. And for a cloud to become dense, it has to be cold. And for stars to form, a cloud has to be dense. Isn't it ironic that star formation can't take place unless the environment around it is cold enough?

That is why radio waves, the longest wavelength of the electromagnetic spectrum and its lowest energy, can forewarn us of some very energetic events in the future. It is because of some of the smallest particles in the Universe altering the way they move around.

Update, 14th May: EigenState on the forum has had a chance to read this post, although I promise I did warn him it might make his hair stand on end. He kindly gave me some great science feedback, well worth a read - he knows a lot more than I do. Here it is.

The Red Button

Whatever you do . . .

Where do people get the ideas for things like this?

Hat tip: Stellar.

A whole train of pinwheels!

One of the ways in which astronomy (and, in my humble opinion, galaxy astronomy especially) is revoltingly lucky compared to a lot of science is the outrageous beauty of our subject - though a lot of biology could make use of that too. Most weeks I could begin a blog post with "It's obviously pretty pictures week on the forum right now!" This week is certainly one such week, and I just feel like giving a tour.

Earlier today, Geoff put up a collection of pictures of the aurora, which are well worth a read. A few days ago, one of our newbies, Terry, started a thread called "space candy", many of which are SDSS treats we have tasted and loved. Incidentally, Terry's special web page about his experiences as a technician at the Mauna Kea Observing Site was fascinating. We know the big names like Newton and Herschel. Just like we know the names of kings and gallant generals. But history doesn't record all the technicians, the teachers, the mothers, the helpers on the forum. Without these quiet souls, the big names wouldn't have done so well. So I was glad when Terry got a round of applause!

Never mind; whether history records us or not, we'll have a great time. Take Tuesday's Astronomy Picture of the Day: the familiar Pinwheel Galaxy, also known as M101.

Credit: APOD.

It's often seen on the Galaxy Zoo Forum, looking like this:

Credit: SDSS.

The two pictures both show it as blue, because of its high star formation rate (mentioned in APOD). It's also an emission line galaxy - no surprise! Countless billions of atoms are so hot that their electrons are falling, radiating light energy of a very specific wavelength, as unique as a bar code: our way of telling what substances are there.

APOD also mentions that the galaxy is large enough to distort its neighbours. But look at M101 itself. Its own arms are hardly symmetrical - the one starting at six o'clock appears to be flying off into space altogether, the one trailing along behind at nine o'clock seems to fancy doing the same thing, and the one starting at twelve o'clock has a great gap and then a bunch of star formation on the far side of that gap. (Isn't it a good thing the galaxy is anticlockwise so the "timing" I'm using appears logical?)

Anyway, Waveney had the sense to zoom out on the Pinwheel Galaxy and showed us what might have happened:


M101 is very near to us, which means it's easily studied. You can have a look at it in gorgeous detail, though without the blue, on Hubble. Here is a huge file - and I mean seriously huge! This is a smaller copy:


Why do spirals so often turn up in nature? Whirlpools, ammonites, hurricanes . . . We argued endlessly about anticlockwise galaxies (which the bias study proved no more common than clockwise in the end), we worry about viewpoint of galaxies and from opposite ends of the Earth . . . and if you search for the Pinwheel Galaxy on APOD, this is what you get.

(Credit: APOD.)

Now looking at M101 in a new light: the Chandra X-ray telescope. (The good folks at which, incidentally, I wrote to recently with a question - I hope to hear from them soon!)

X-rays in space are just the same sort we use in hospitals: a kind of light whose wavelength is far too short for our eyes to see. That means its frequency and its energy are very high, and they're not something we'd like to get in the way of too often! (Hence, doctors and nurses leave the room when they give you X-rays - repeated exposure would definitely harm them.) X-rays are given off by high energy nuclear fusion - we get a few from the Sun, but most photons created in there have spent too many thousand or million years banging into one particle after another to still be that energetic when they reach the Sun's surface.

(Credit: Chandra. That page is well worth a look in detail - for example, it has a nice little video.)

The visual and the infra-red seem pretty similar, spanning pretty much the whole galaxy. That's to be expected; they're weaker forms of light radiated by stars. The X-rays mostly clump together in the middle, in definite dense and less dense areas - with just a few bright X-ray spots in the very places where the arms look very blue and bright. Chandra has another composite image helped along by Spitzer, which was excited enough about a discovery of its own concerning our familiar Pinwheel last year.


One last picture, specially from Spitzer. This is an infra-red image, the pink areas showing dust clouds and the starlight in blue. That one shows what happened in the least disrupted arm with all the star formation occurring outside a "gap" - it looks like a lot of dust got flung out there . . . The more disrupted arms appear to have little gas left. I wonder if that means they'll disappear in a few million years?

(Credit: APOD.)

Finally, I'm delighted to notice that in the Spitzer image, and in Chandra's infra-red, we can see the tiniest little bar. Just as Johan Knapen said at Astrofest, infra-red light is the best way to find bars. Now after all those pictures you will probably want to head to a real bar. Bring some space candy with you!