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Topics - Alice

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Cafe at the end of the Universe / Can you find a Tube Mackerel?
« on: July 25, 2013, 11:55:48 am »
It's a popular piece of "pub trivia" that the only Tube (Underground) station not to contain any of the same letters as the word "mackerel" is St John's Wood.

A friend of mine has named St John's Wood a "tube mackerel" and has set up a website to try and find other tube mackerels . . .

Orion is not one :D

"Galaxy Zoo Forum" is a tube mackerel! The only station not to contain any of the same letters is Debden. ;D ;D ;D ;D ;D

Hi everyone. Really sorry I've not been around much - I've been having a hard time recently due to the course, unemployment, and other personal reasons. I hope to be back a lot more after my exams. Thank you all for all your spammer reports!

Anyway, this is an open invitation to come along to celebrate my birthday from a few weeks ago and the end of my exams. It will be pretty much the following:

12pm or thereabouts: meet at the big statue by Greenwich Planetarium and have cake and ice cream. (They sell amazing ice cream and I can bring cake.)

Early afternoon: see a planetarium show. There's one called "We Are Aliens" and one called "Sky Tonight Live". The latter is always lovely; I haven't seen the first. Also it's well worth a look round the Observatory.

Late afternoon: progress to a pub. There are two very nice ones nearby: the King's Arms and the Greenwich Union. We can try either. If you have kids then we can try to find out which is child friendly. I know many of you know and love the Greenwich Union, but I discovered the King's Arms pretty recently and it too is lovely.

Early evening: Chinese food at the Golden Dragon restaurant in Gerrard Street. If you want to come to this please let me know so I know how many to reserve a table for. Pub may follow, let's see how we all feel/whether or not we can still walk.

Let me know if you'd like my phone number, especially if you want to join late. I'm expecting people to join late or leave early or whatever - come to whichever part of the day appeals to you.

I'm extending an open invitation to zoo people and people from my course, plus friends of mine from various places, so there will be a very interesting and geeky mix of people! Should be a lot of fun - it was last year.

Greenwich Observatory
Golden Dragon restaurant

Technical Support / If you can't log in (21st May 2013 onward)
« on: May 22, 2013, 01:49:00 am »
. . . this is because Arfon's just upgraded the forums and you need to reset your password. Don't worry!

Like a silly person, I kept entering and re-entering my old password. This doesn't work. Go to the reset page (also on the top right of the forum). You can enter either your forum name or your e-mail and you'll be sent to where you can get yourself a new password. Using the same one as you had before will also work fine.

See you all back here soon! :)
(If I hear that lots of you are having trouble I'll find out who you should e-mail.)

Before I start today's Object of the Day, I want to be sure you have all seen this blogpost: would you like to go to Chicago to help plan future zoos? ;D

In the meantime, my course is now looking a lot at spectra. Spectra are pretty much my favourite things ever - I wrote about their discovery here and here.

To cut a long story short, if you put a prism in a beam of sunlight, you might see something like this . . .

(BU Astronomy Department)

. . . and good old Fraunhofer labelled the dark lines as follows:


It wasn't too long before it was noticed that if you burn sodium, it gives off light of exactly the wavelength and frequency that occupies the lines in the yellow band labelled "D". Or, if you shine a really hot light through burning sodium (where the light source is hotter than the burning sodium), the dark D line appears. Sodium is in the Sun, absorbing certain wavelengths of light.

Each atom absorbs very specific wavelengths, and photons of the very same wavelengths may be emitted from the same atoms. Each atom has several different wavelengths of photon it will absorb, but they are very specific and end up as very thin lines. (If you're wondering why, it's an amazing story - check the links in the first paragraph!) You also find such lines in infra-red, microwave, radio, ultraviolet light . . . for it's not just in the visible spectrum! Even in the visible light, there's a huge amount of variety.

Here's a more sophisticated solar spectrum from the Harvard-Smithsonian Center for Astrophysics:

If you expand it enough, you'll see that all the lines are very thin indeed. Just what we'd expect. If some atom has an electron energy level that will absorb a photon with a wavelenth of 600nm, a 599nm or 601nm should go straight through it, right?

Well, mostly.

Spectra such as that of the peas are indeed nice and skinny, on the whole:

587741532770074773, posted by Hanny and Rick Nowell

But to take another extreme - here's the first entry, by cpt. Bear, in the Quasars thread:


It doesn't look like just one nm, or angstrom, or whatever very narrow energy band you like, of light is being absorbed or emitted here!

As it turns out, there are many processes that can broaden spectral lines . . .

Natural line broadening

Because of good old Heisenberg and his Uncertainty Principle, you can never be 100% sure exactly where an atom is or exactly what it's doing. The same applies to the energy of an atom. In fact, conservation of energy may itself be violated for a very short amount of time (the more it's violated, the shorter the time available to do it in). This also allows a certain fuzziness to appear in spectral lines. The shape of the line becomes "Lorentzian" or a "Lorentz profile".

Collisional line broadening

Out in space, such as gas clouds, atoms are pretty much left to their own devices without interference from other atoms. That means that we can work out a natural lifetime of how long an electron should exist in an "upper" energy state (when it's been hit by a photon) before it falls back to the "ground state" (when it throws the photon off). We can't get this effect on Earth, even in a good laboratory vaccuum: there are too many collisions between atoms. However, of course collisions do exist in denser regions of space, such as stellar atmospheres, disks, gas clouds etc. This shortens the "lifetime", and the energies of the colliding atoms interfere with the energies of the photon being released - the collision may have added energy to the atom, for example.

This results in a broader line than the natural broadening line, but they're still a "Lorentzian" shape. When we spot this going on in space, we can tell that there's some density out there . . .

Thermal or Doppler line broadening

When molecules are over 0 kelvin (absolute zero), they're moving! They may be pulsating, rotating, jiggling back and forth, or moving turbulently amongst each other. This means that, on average, some are coming towards us and some going away. Any spectral lines amongst those going away will be redshifted, and those coming towards us, blueshifted. Even a cold CO gas sitting in space of 50K (brrrrrrrr) might find that its lines are broadened by 1,000,000 by Doppler broadening than by natural broadening!

You generally see this and collisional lines together. (Natural broadening of course is always present.) The shape of the line for this, however, is a "Maxwellian distribution". It's broader at the peak and narrower at the axis.

When we add up all the lines, we get something called a "Voigt profile", which is an average of all the broadenings. I shall leave looking that up and discussing it to those who want to. :D


This isn't quite the same thing, but I can't resist this personal and highly zoo-orientated addition. You probably know how redshift works: a galaxy far away from our own is moving away, and its light is getting stretched. Since every element's spectrum is unique and recognisable, we can easily work out its redshift by seeing how far the peaks have moved. But does the spectrum retain the same shape?

It does retain the same shape overall, but it itself will be stretched out. The longer the wavelength (the further red you go), the more the effect. In fact, I worked this out using some simple maths, after various astronomers on Twitter had implied to me that there is no stretching! :D The formula is as follows:

1 + z = (1 + [v/c]) γ

or rather, 1 + redshift = (1 + galaxy's velocity/the speed of light) x wavelength.

Let's choose an easy velocity - let's say the galaxy is going away from us at 30,000 km/s. Then you can just divide 30,000 by 300,000 km/s (the speed of light) to give you 0.1.

The formula contains a 1 + your result, so here we multiply the wavelength of any photon by 1.1.

*Warning: my maths is out; a friend pointed out I have just mashed up two equations here, although the concept is OK. Hopefully more will appear in the comments later. Unless you'd like to have a go?*

Now, let's say we have two emitted photons, one of 500 and one of 600nm. If you multiply their wavelengths by 1.1, the longer wavelength one is stretched more than the shorter-wavelength one. As NGC3314 put it: "All wavelengths are stretched by redshifting by the same fraction (1+z). So redstretching might be a better term." That means, too, that any gaps in the spectrum (absorption lines) would also get stretched - especially at the red end of the spectrum. (Incidentally, I had suspected this was the case for years, but it took several minutes of struggling to find the right formula and getting frustrated to confirm my suspicions!)

And finally . . . Quasars!

Quasars contain all of these! They contain redshift, they contain natural line broadening (as do all atoms), they contain plenty of thermal fluctuations and collisions, and they also contain the fact that the matter is moving very quickly in an accretion disk! So, unless the quasar is exactly face-on to us (in which case we'd see a blazar, for we'd be looking right down one of its jets - and I'd rather not do that :P), we'll see half the disk moving towards us and half away. All the absorbed and emitted light is naturally squashed or stretched accordingly.

Right - now I must go and actually do some of the maths around this, I guess! :o :o :o :o :o

Dear all,

This April, Jules, hopefully me (depending on my exam timetable), and one of you will get to go to Chicago to help plan future zoos!

It will involve various presentations about future projects and how to design them and they want input from us, the users, on how to make it as good as possible. The dates are April 29th and 30th.

If you'd like to go, tell them why:
. . . please tell us in no more than 250 words a little about yourself, why you think you should go and what you can contribute to the discussions as a volunteer. Please add your full name and preferred e-mail address and send this to with the subject line CHICAGO PLEASE. The closing date is 12 noon GMT on Thursday 7 March 2013. The Zooniverse team will choose the successful entry.

Further details here on the blog, and JeanTate has started a topic here in Star Space where there is more discussion.

I really hope to see you there - sadly my exam semester begins on April 29th, so if I have an exam then or shortly afterwards, please bring a galactic penguin and lots of support for a lovely polite cafe-filled discussion forum in my place! :-*

Cafe at the end of the Universe / Happy 18th, Stellar!
« on: February 02, 2013, 08:01:13 am »
Look out, everybody. She has come of age :o :o :o :o

I hope you have a lovely day ;D ;D ;D

Object of the Day / Sunday 20th January 2013: this really is a zoo
« on: January 21, 2013, 03:06:36 am »
In the light of this week's Wired collection of animal-shaped nebulae and my recent addiction to Snapshot Serengeti, I thought I'd bring back a few old favourites from the Galaxy Animals collection. ;D



Impala, I think:

("Goat's head" - just as well an antelope's head - by Alexandre)

Purr . . .


Tsering found a hare . . .


The Pure Art Thread also makes an appearance! :D


And finally . . . Someone long-lost . . .


One zoo has obviously bred another. It's amazing to think that when I was a newbie, finding that starry elephant irregular galaxy, marvelling at that overlap that became a cat, the Zooniverse was just this one zoo. Now it has grown to more than I can even visit!

(As I write, it's 14 science projects and 3 laboratory experiments. The current latest is Planet Four. Doubtless within a few more weeks or even days, this will have grown even further.)

You can come and see our collection of everyone's favourite Snaposhot Serengeti animals - including a gazelle who's just given birth - here in the Cafe.

We really are zoo-ing and fro-ing all over the place! :D

Cafe at the end of the Universe / Snapshot Serengeti Gallery
« on: January 12, 2013, 03:45:04 pm »
I thought it would be nice for fellow Serengeti fans to share some of our favourite meetings ;D

Sometimes our friends get a bit too close to the camera for me to be able to tell who they are. Fortunately, these folks are always a bit obvious :D

A Thomson's gazelle - they have such fine flashes of black on their sides.

Sadly this was just a one-off night shot and I never saw this fine leopard's face!

Sometimes I favourite an image for the view alone . . .

Where's Fluffy? :D

I've seen this place several times and it's always busy ;D

Why hello!

Best to stay out of his way I think . . .

There is a classification for this, too. (Actually quite a few of the cameras are at a 45 degree angle and need putting upright . . .)

And good afternoon to you too my friend.

I do believe I have encountered a baby gazelle! :-*

Not a tall story at all - I am just on my way.

Hartebeests are one of Tsering's favourites. They have very recognisable horns!

Shots like these are my pride and joy . . .

. . . this of course being a very special delight! ;D ;D ;D ;D ;D

And my favourite meetings of all have been this . . .

. . . And this. 8)

Object of the Day / Sunday 9th December 2012: Sir Patrick Moore
« on: December 09, 2012, 10:14:03 pm »
A very sad Object of the Day today . . .

(thanks Blackprojects)

A farewell to Britain's giant of astronomy, Sir Patrick Moore, who presented the Sky at Night for 55 years. Many astronomers today say they were inspired to the subject by him - it was the book "BANG!" he coauthored with Brian May and ZookeeperChris that made me realise how accessible astronomy is and that led me to meet the three of them (and the rest is history).

Sir Patrick was a very friendly person who'd go out of his way to meet and help countless people. I remember one occasion - Herstmonceaux, September 2009, where so many people arrived for a talk he was giving that there was no way even most could fit into the building. So Sir Patrick said he'd give the talk twice, so Waveney, Sysboy and I got to hear the second one. This was typical of both his popularity and his willingness to take trouble.

His house, Farthings, was always open to people wishing to come and meet the telescopes or just to visit and chat. Galaxy Zoo's best ever meet-up, I think, took place at Farthings in 2008.

He really liked Galaxy Zoo, and September 2008's "Sky at Night" was about us, with an interview with Hanny.

There are many tributes from zooites in this thread. Sir Patrick, you'll be very much missed - thank you for all the stars.

Object of the Day / (Very late) Sunday 28th October 2012: Scary Spirals
« on: October 30, 2012, 06:11:53 am »
Sorry about my lack of recent Objects of the Day and, indeed, presence on the forum. Real life . . . If I'm needed anywhere, please feel free to poke me! I hope to be back properly in time.

This puffy little spiral, posted by Ex103, seemed to me reminiscent of a Fibonacci spiral - a spiral whose "quarter arcs" get larger at a predictable rate.


(If you find an even more satisfying one, please let me know!)

Spirals occur all over the place in space. Spiral galaxies, as we found in Galaxy Zoo's early days, make about a third of the total galaxy population - at least, that we got to classify in the Sloan Digital Sky Survey. A gas cloud collapsing to form a star, or an accretion disk around a black hole, or even Saturn's rings, are spirals:

Universe Today

(We can't directly image any forming stars and accretion disks, but using their spectra to find out their temperature gradients plus a scary amount of maths will tell us an awful lot, even allowing us to make predictions about the formation of planets (you can have a look through one of the courses I took last term if you like! Maybe you'll be encouraged to come and study astrophysics too?).

In one recent case, a spiral formed in the aurora, too!

David Cartier; Bad Astronomy blog

And Fibonacci spirals, a specific type of which is known as golden spirals (at least I think that golden spirals are a subset - am I correct?), are found in many places in nature:

Snail shell - IES

Pine cone - maths site, Surrey (you can trace various types of spiral on the bottom of a pine cone)

Sunflower - Matthen (again, lots of different spiral patterns here)

And here's an absolutely incredible one . . .

This is Hurricane Sandy - but I can't find a source for it except this Facebook page, for those of you who have a Facebook account (if you don't, please don't get sucked into that particular black hole on this OOTD's account). Googling led to other people asking about it, too.

Spirals are all over nature, both living and non-living; there's an old Astronomy Picture of the Day of a hurricane next to a spiral galaxy, looking remarkably similar, which I'll link to when their site problems are fixed. Sometimes they optimize good things, as plant leaves optimize the amount of light they can get; other times they are destructive; to me, they are always beautiful.

You can find more about Fibonacci spirals on these incredible mathsy youtube videos by Vi Hart.

And to all those affected by Sandy, stay safe - I'll be thinking of you!

Object of the Day / Sunday 30th September 2012: NGC 6745
« on: September 30, 2012, 07:52:36 pm »
Galaxy Zoos 3 and 4 have involved galaxies from the Hubble Space Telescope. This new one is using the CANDELS survey - the Cosmic Assembly Near-Infrared Deep Extragalactic Legacy Survey, which uses a combination of a near-infrared and a visible-light camera. It's designed to examine the long-ago, young Universe in great detail.

It's often said that merging galaxies were more common in the early days of the Universe. Here's another one Hubble snapped and that is today's Astronomy Picture of the Day:

And here it is from the SDSS telescope, which supplied all our galaxies in zoos 1 and 2, and continues to supply some of them in 3 and 4.

758879801986515490, posted by dylhomme - I can't find any more under that Object ID.

As the APOD says, the interaction isn't really between stars - they are exceedingly unlikely to collide. However, gravitationally the galaxies are twisted into funny shapes, due to tidal forces and the nearest-to-each-other ends feeling the other's gravity the strongest; the gas and dust collide; the magnetic fields also interact. Simulations of collisions sometimes mention dark matter interacting - that when you first see distortion in a galaxy, it's due to the dark matter moving first.

As far as I know, this hasn't yet been found in Hubble Zoo. But I could be wrong - please let me know if I am! RandyC found another image from Hubble of NGC 6745:

You can also view it on the Astronomy Now gallery and check its Wikipedia page. They say it's an irregular galaxy. I disagree - what do you think, Waveney? :D

This is SUCH FUN! ;D ;D ;D

There's a short lecture beforehand, which is also fun, but if you want to skip it, go to about 3 minutes in.

Object of the Day / Sunday 23rd September 2012: an old gem
« on: September 24, 2012, 12:18:43 am »
Welcome to Galaxy Zoo 4!

One of its consequences is that we are seeing some very old beauties, that we first enjoyed back in 2007. Today's Object of the Day was found by Lovethetropics and mentioned in "A Thread to Talk about Talk":

IC 2520

You can also see this galaxy on SIMBAD and Skymap, but it doesn't seem to be greatly well known. Well, at least not by the generic web. Google seems to think it's various types of datasheet or machine, and the Wiki page remains empty!

It is a gem of a galaxy; we don't often see green, apart from in camera artifacts and the peas. The blue areas in galaxies usually indicate star formation, but are not generally this smooth. There is a yellow nucleus, and a patch of darker yellowish dust on the right. To me, it always looks like an eyeball . . .

This was made Object of the Day precisely 5 years ago, on Sunday 23rd September 2007! ZookeeperKevin wrote:
IC 2520 is a massively starforming merger producing stars at such a prodigious rate that the dust from all that star formation is obscuring large parts of the galaxy. It's a great example of a merger-induced starburst.

Also like the peas, this galaxy appears to be on its own - though is that a merger I see in the top left hand corner?

Then, on Saturday 3rd November, 2007, an unsuspecting me made it Object of the Day again - with a slightly different reference number. It has several, you see: click "Photometric Objects" on the bottom left of this page, and a lot of bubbly stuff will appear! Each blue circle shows a point where the SDSS telescope centred in for an image and hopefully a spectrum.

How far Object of the Day and our understanding of galaxies have come along since then!

I was highly amused by a post AlexandredOr made yesterday, announcing the Pipe Nebula.


I wondered what had created such an amusing shape . . .

. . . and noticed that there was a blank wall to the left. This meant this was an area not so far imaged (or where there had been a fault, perhaps). So I zoomed out.

The results were odd.

Apparently, whoever was smoking that pipe had had a bit of a paint explosion!

. . . and you finally end up with this!

It goes on and on and on!

I would love to know what was up with the Sloan's cameras that day! But that's as far as I can zoom out. Navigating around shows that there is quite a large area where this has happened!

All I can say is, someone out there in the cosmos is rather into fluorescent weaving! :D :D :D

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