In our first podcast we take a look at the latest version of Galaxy Zoo: – Hubble Zoo.

Peter: Hello and welcome to the first Star Sailor podcast with Peter Clark and Hannah Hutchins. Today we’re discussing the latest reincarnation of Galaxy Zoo:  Hubble Zoo!

Hannah: So Hubble Zoo is a citizen science project that uses the general public to classify a whole host of Hubble galaxies, focusing on their morphology.

Peter: For those of you who aren’t well versed in astronomical terms, morphology literally means the shape of a galaxy. The previous Galaxy Zoo’s discovered some very interesting trends between the morphology of any particular galaxy and its location and its distance from the earth, also known as its redshift. Hubble Zoo is designed to take this analysis to the next level and provide an even more detailed analysis of lots of galaxies so its conclusions can be drawn over a wide data set.

Hannah: So the previous galaxy zoo projects 1 and 2 used data from the Sloan Digital Sky Survey data base -

Peter:  Thankfully we can shorten this to SDSS, which makes it much easier on us for the podcast.

Hannah: So the SDSS data base mostly has galaxies of relatively low redshift so the galaxies are lurking mainly millions of light years away.

Peter: We should add now that redshift isn’t a direct measurement of distance; it’s actually a measure of how the light from a particular galaxy has shifted to one end of the spectrum. This can either be blue or red. As most galaxies are moving away from us, the light is stretched into longer wavelengths, meaning they are red shifted. The more the light has been redshifted the further away the galaxy is, so it allows you to calculate a rough estimate of distance.

Hannah: The opposite of redshift is blueshift, which means that the light of the galaxy will be shifted to the bluer end of the spectrum, as it’s moving towards us.

Peter: This happens because the light is essentially compresses into shorter wavelengths, so appears bluer. The most famous example of a blue shifting galaxy is the nearest large galaxy to the Milky Way, the Andromeda, or M31. It is in fact in a projected collision course with the milkyway and should collide with us within the next few billion years. Don’t worry; it’s not something you should be worried about!

Hannah: The Sloan telescopes aperture –

Peter: Which is a very fancy word for a mirror –

Hannah: – Is 2.5 metres, whereas the Hubble telescopes aperture is 2.4m.

Peter: Generally speaking the larger the mirror you have on a telescope the better images it can produce, despite this, Hubble sits above the Earth’s atmosphere and so despite it having a smaller aperture it can take much better photos as I’m sure you’ve all seen in the Hubble press releases.

Hannah: So because the Hubble telescope is outside of the Earth’s atmosphere it can further back in the universes history, as much as billions of years.

Peter: This means that galaxy zoo is now able to study galaxies as they were forming, rather than long after the formation process was complete. This is allowing galaxy zoo to put together an idea of how galaxies in general form and how the formation process between say an elliptical and a spiral differ.

Galaxy zoo has already discovered many interesting objects, as well as a completely new type of galaxy known as the Peas.

Hannah: The Peas are highly compact galaxies which are star forming at incredible rates.

Peter: This rate is many times that of what is currently occurring in the Milky Way.

Hannah: The Milky Way churns out one to four stars a year whereas the Peas can churn out up to 40 sun-like stars a year.

An example of a Pea; Credit: SDSS

Peter:  As you may have guessed from their name, the Peas on the SDSS appear to be green, small and round, and well, pea like; hence their name. They where first identified as a bit of a joke on the forum but what turned out from one or two turned into an entire collection that become impossible for professional astronomers to ignore.

Hannah: Followed inevitably by loads of puns about garden peas –

Peter: And well, give Peas a chance…

Hannah: Yes

Peter: Which you can still find on the forum!

Whilst the peas are incredibly interesting objects they are by no means the only objects discovered by Galaxy Zoo that are completely out of the ordinary. One of the most famous is of course Hanny’s Voorwerp. The Voorwerp lies just outside the galaxy IC 2497 – yes astronomers are really inventive with naming things. The voorwerp is believed to be a free floating cloud of ionized oxygen without any sign of star formation at all.

Credit: William Keel, Anna Manning, 3.5m WIYN Telescope

Currently the most popular theory for what causes the ionization of the gas in the first place is a residual light echo from IC 2497’s once active nucleus which has since become inactive and so we’re seeing the residual trace in the gas of the voorwerp.

It is also believed that eventually the Voorwerp will fade from view as it loses the rest of its energy and just becomes one other boring cloud of hydrogen (Edit: -As Alice pointed out it also contains helium and oxygen and other elements with the oxygen being ionised)  gas sitting in space.

The discovery of the voorwerp sparked a hunt within the zoo for any other ionized gas clouds found within the SDSS data base. No other Voorwerps where discovered however an interesting class of galaxies where discovered in the process.

Hannah:  The Voorwerpjes.  Though we’re not actually quite sure how you pronounce that so we just call them floor pies…

Peter:  It is Dutch for ‘small objects’ incase you’re interested.

Hannah: These galaxies have massive clouds of ionized oxygen, hydrogen, thousands upon thousands of light years wide. These clouds of ionized gas are ionized by the super massive black hole at the centre of these galaxies, material is falling into the black hole in a doughnut shaped accretion disk, and as the material speeds up around the black hole like water going down a plug hole it releases a heck of a lot of energy, such as ultraviolet and x-rays.

So as the radiation is emitted by the centre of the galaxy the radiation then strips the hydrogen or oxygen clouds of their electrons, therefore ionizing  the gas and lighting it up.

So as you look at the SDSS images you can see massive pink or blue clouds stretching across the galaxies for up to ninety thousand light years.

From left to right: Mkn 266, 2MASX J14302986+1339117 and UGC 7342. Image credit: SDSS

Peter: They really are very interesting object to look at! To save you from having to hoak through the Sloan data base we’ve picked out the some of our favourite voorwerpjes and put them in the slide show.

To finish up with we’d like to invite you all to come and join us at galaxy zoo, you can help contribute to citizen science and make a real impact on astronomy as a whole.

The website is completely free to sign up for it and it’s incredibly fun. If you’d like to join us it’s at www.galaxyzoo.org, if you need a link directly to the site you can find it in the description if you’re listening to this off of Youtube and the post below if you’re reading this off The Witty Astronomers blog.

Galaxy Zoo is also famed for its forum, with its incredibly friendly place that like minded people can talk about everything from the galaxies they are classifying, their favourite taste in music, coffee…

Hannah: Socks…

Peter: chocolate

Hannah: Elephants

Peter:  Gardens… You never know!

Hannah: Marshmallows…

Peter: It’s a rather diverse place! So if you want to come and join us we’ll be delighted to have you at www.galaxyzooforum.org, again that’s in the description or in the post below.

We hope you’ve enjoyed listening to the first Star Sailor podcast and we hope to do this reasonably regularly, again we hope we haven’t been too boring for you but thank you for listening!

The SDSS home page can be found at http://www.sdss.org/

Hubble Zoo can be found at www.galaxyzoo.org

The Galaxy Zoo forum can be found at www.galaxyzooforum.org