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Hubble's View of NGC 4911

This week’s OOTW features an OOTD by Alice written on Thursday 12th of August.

NGC 4911

With a redshift of 0.027 this spiral galaxy lies 320 million light years away from us. It’s NGC 4911, a spiral galaxy in the Coma Cluster; a city of galaxies gravitationally bound to each other in the constellation Coma Berenices. LEDA 83751 – the larger elliptical overlapping the galaxy – is actually sat in front of the spiral, which isn’t the best situation for overlap hunters:

Overlapping galaxies are especially useful to Bill and other astronomers interested in dust – the background galaxy acts like a torch, showing what the dust is doing in the former one. The best situation is an elliptical being further away than a spiral, since spirals tend to be dustier and more interesting. Sadly this pair appears to have the bad manners to be the other way round. How rude :D.

– A quote from Alice’s OOTD.

Hubble image of NGC 4911

A new Hubble image of this galaxy has been released showing in more detail the huge amount of star formation going on nearer to the nucleus of the galaxy, the dust lanes streaking their way around the beginning of its spiral arms,  and the wispy spiral structures wrapping their arms around the bustling galactic centre.

Peas Through a Lens

This week’s OOTW features today’s OOTD by Budgieye.

SDSS J001340.21+152312.0

SDSS view of SDSS J001340.21+152312.0

This yellow fuzzy galaxy is a Quasar 1.59 billion light years away from Earth in the constellation Pegasus; it’s just above to the left of the star Gamma Pegasi.

When you zoom in with the Keck observatory you’re treated to this beauty:

SDSS J001340.21+152312.0

Credit: F. Courbin, G. Meylan, S. G. Djorgovski, et al., EPFL/ Caltech/WMKO

Now what the Keck telescope can see and the Sloan telescope can’t are the two red smudges in the blue glow of the Quasar. These smudges are in fact one Pea gravitationally lensed by the QSO sitting in front of it! This is the first ever example of a Quasar strongly lensing an object. This is where a galaxy or a cluster of galaxies are so massive that they bend space-time so much that it visibly bends light around them. So the light emitted by an object sitting behind a cluster of galaxies gets bent around the cluster, creating multiple images of one object.

So how can we tell they are multiple images of the same object?

A quote from Budieye’s OOTD:

To ensure that the two red objects on each side of the quasar is actually the same object, each object must have their spectrum taken separately.
Both blobs of red light had identical spectra, indicating that both blobs are the same object, and that the quasar is bending the light from the distant galaxy into two blobs.

Galaxies spiralling out of control

Today’s OOTW features Alice’s OOTD, posted on the 29th of July.


AHZ40004wr from Hubble Zoo

This is AHZ40004wr, a galaxy residing in the constellation Taurus around 3 billion light years away. It’s a wonderful spiral galaxy, and following its spiral arms is a large dust lane, a place full of young stars and stars that are only just being formed.

AHZ40004wr by Swengineer

AHZ40004wr by Swengineer

Zooite Swengineer gave us a wider view of AHZ40004wr and the surrounding galaxies by working with the FITS images and revealed the mess of galaxies above. The main spiral galaxy in the background is 2MASS J03324999-2734330, an X-ray source according to SIMBAD, and it is also around 3 billion light years away.

You can view more images of these galaxies here and here, and to work with the FITS files I recommend DS9 or Aladin, which I used to find the other galaxies details.

And to highlight a request from Alice’s OOTD, Alice would very much like to know if anyone could write any FITS and image editing tutorials on the galaxy zoo forum.

The Sunflower of Canes Venatici

This galaxy is featured in LizPeter’s OOTD for 24th of July 2010.


M63 from the SDSS

This is Messier 63, though I much prefer its other name, the sunflower galaxy. It’s a wonderful dusty spiral galaxy lying 22.9 million light years away from Earth in the constellation Canes Venatici. It’s one of 7 galaxies bound gravitationally together in the M51 group, and according to Wikipedia, it is one of the first objects to be seen to have spiral arms. This was pointed out in 1845 by William Parsons in a time when these objects were thought to be ‘spiral nebulae’ in our own galaxy, and not galaxies themselves. SIMBAD also claims that there is a cluster of stars lying in the foreground of the galaxy.

There are some brilliant Hubble Legacy images and spectra here, and some more from assorted observatories here!

Markarian and the Blob

Today’s OOTW features an OOTD written by Alice on the 15th of July.

117 million light years away there lies a Markarian galaxy and a very interesting companion. As Alice says in her OOTD, these Markarians are galaxies that emit strongly in ultraviolet and visible light, and are often a host to AGN.

During the observation run at Kitt Peak the Galaxy Zoo team had some spare telescope time going after observing a list of Voorwerpjes, so Bill Keel asked Zooites on the forum to provide objects to get a spectrum for:

MRK 490

MRK 490 and its blue companion.

The bright blue blobby companion just above the Markarian galaxy MRK 490 centred in the picture above was one such object that was observed. The companion is brimming with new stars as shown by the huge emission line (amongst others) of OIII at around 5000 angstroms in the spectrum below, the object is very close to the galaxy below it going by their redshift, so it is suspected to be interacting with it!

Spectrum for MKN 490's companion

Spectrum for MKN 490's companion; click for larger image.

Black Holes with an Appetite

 SDSS J142005.59+530036.7

SDSS J142005.59+530036.7 from AEGIS

This object has the imaginative name SDSS J142005.59+530036.7. It lurks in the Bootes constellation and although it looks like a star, it’s actually a Quasar 15.3 billion light years away from earth going by its redshift. I have a love for Quasars, so I couldn’t resist this one in Budgieye’s OOTD posted on the 6th of July!

In the heart of this galaxy lies a super massive black hole like most other galaxies. This particular one is an AGN, an Active Galactic Nucleus. AGN are super massive black holes in the centres of galaxies that are pulling in material from around them such as stars and gas. This material gets pulled into a ring doughnut shaped accretion disk around the black hole, and as this material swirls round it causes friction, releasing radiation out into the galaxy. The centres of these galaxies can be so energetic that they can outshine the galaxy itself; hence all you can see in the picture above is a star-like object- the nucleus of the galaxy.

This energy can also be concentrated into jets of high energy plasma racing out at near to the speed of light for thousands of light years from the poles of the black hole, and depending on how these jets are positioned in relation to us the galaxy the AGN is lurking in can be called radio galaxies, Blazars, Seyferts and so on. In this case it’s a Quasar, so the jet is positioned so that it’s not quite beaming directly at us. Here’s a great OOTD by Fluffyporcupine on AGN!

And thanks to Alice for helping me out! 🙂

From Blob to Collisional Ring

This week’s OOTW features this object (below) from Tsering’s OotD posted on the 26th of June.

AHZ30000yv SDSS Version

AHZ30000yv from Sloan's view

As Tsering showed, this seemingly uninteresting blob on the SDSS turns into this in Hubble Zoo:


AHZ30000yv from Hubble's view

This is AHZ30000yv, a wonderful collisional ring galaxy! I love seeing the huge differences between the SDSS and Hubble images, the reason why Hubble can see more is because it’s out of the way of the Earth’s atmosphere, so even though Hubble is actually smaller than the the Sloan telescope (Hubble’s mirror is 2.4 meters and the Sloan telescope’s mirror is 2.5) it can see further, taking us visually back to when the universe was around half its current age and making me very happy indeed!

This ring galaxy has a Z (redshift) of 1.432, so we’re seeing it as it was 9.15 billion years ago, just under 5 billion years after the big bang! So how did this galaxy end up as a collisional ring? The ring formed after another smaller galaxy punched through the centre of the galaxy, creating masses of hot young blue stars in the process through all the gravitational disruption.

And I have to quote this lovely post by Budgieye from the comments on Tsering’s OotD 😀 :

It is fun looking at the difference.
There must be lots of UV light coming from it, otherwise nothing would be visible at all on SDSS.  At that distance, the ordinary blue light from the stars would be redshifted off the limits of the SDSS detector for far red light.
A nice addition to
Colours of Galaxies in SDSS : Redshift chart

Binary Star System in Cetus

*80 Cet

*80 Cet

80 Cet, a star posted by Zooite and moderator Infinity on Sunday 20th June 2010 for Father’s Day, is in fact locked gravitationally to another star, both orbiting around each other on their common centre of mass. Interestingly, around one in three stars in our galaxy are found in binary or multiple star systems.

I couldn’t glean much information on the stars but with the help of SIMBAD and Peter Clark (@lightbulb500) from the Young Astronomers website, we both agreed that it’s likely to be a Red Giant paired with a White Dwarf star -please point out if we have the classification wrong!

Sources: Wikipedia and Binary Stars Blitzed.

Galaxies in Miniature

This weeks OOTW features an Object of the Day by Geoff, posted today:

” Today’s object is a splendid dwarf galaxy originally posted by AlexandredOr on 12 May 2008.




It is IC3215 & UGC7434 ”

Dwarf galaxies are what they say on the tin, these galaxies are tiny compared to galaxies like our own, which contains hundreds of billions of stars. These dwarfs only contain several billion. This particular dwarf galaxy lurks in a favourite constellation of mine; Coma Berenices. If you go to the SDSS finding chart tool and zoom out you will also notice that it happens to be in the line if sight of the open cluster Melotte 111:

Melotte 111

Melotte 111

Whilst reading up on the dwarfs, I found that interestingly it has been put forward that Omega Centauri, a globular cluster in our own galaxy, could actually be the remnant of a dwarf galaxy that once orbited the Milky Way.


This is the first in a series of once-weekly blog posts featuring Object of the Day (OOTD) posts from the Galaxy Zoo forum.