Tag Archives: Dust

The Bubbling Galactic Disk

Some of the most beautiful structures in Spitzer GLIMPSE data are the bubbles. Bubbles are regions of gas, usually found around newly formed stars, often with shells of material surrounding them (the green 8 μm emission above). These appear as rings in the GLIMPSE images and can vary in appearance from strikingly prominent to intriguingly faint. They can be anything from complete circles and ellipses, to fractured, fragmented remains.

As part of Project IX we’re going to ask you to find and measure these bubbles. Researchers can use this information to learn a lot about how these objects form and how they trigger star formation.


Above is an image of RCW 120, the titual “perfect bubble” from a 2009 paper by Deharveng, Zavagno, Schuller, Caplan, Pomarès and De Breuck. This colour-composite image shows Hα emission in blue, 8 μm emission in green and the 24 μm emission of small dust grains in red. The image is approximately 24′ degrees wide.

The green material has been swept up as the region expanded, after the formation of a massive star in the centre. There are about 2000 Solar masses of neutral material here, and this has fragmented into lumps. This is where star formation is occurring. The authors of the study found 138 potential star-forming objects in the ring around RCW 120.

In 2006, a group of astronomers visually inspected the GLIMPSE data for bubbles and catalogued their results in a paper titled ‘The Bubbling Galactic Disk‘. I’m a sucker for a great paper title. The team behind this study has been looking at the GLIMPSE data ever since. As mentioned above, bubbles are important features in the study of star formation. Here’s how they are described in ‘The Bubbling Galactic Disk‘:

The study of bubbles gives information about the stellar winds that produce them and the structure and physical properties of the ambient ISM – interstellar medium – into which they are expanding. Additional physical insights include the hydrodynamics of gas and dust in expanding bubbles, the impact of expanding bubbles on magnetic fields in the diffuse ISM, and mass-loss rates during the evolution of stars.

In 2006 322 bubbles were visually identified by just a handful of people. Since that time two things have changed. Firstly, there is now a lot more data, and therefore more bubbles. Spitzer has also continued to map more of the galactic plane for the GLIMPSE360 project – more on that in a later post. Secondly, the Zooniverse now exists!

Everytime the Zooniverse and bubbles have been mentioned together, someone has been there saying that we should get the public to find and measure them. Whether this is between Chris, myself and others at Zooniverse HQ or between Grace Wolf-Chase at Adler Planetarium and various members of the ‘The Bubbling Galactic Disk‘ study. Bubbles and the Zooniverse should be a match made in the heavens.

Why are bubbles such a good target? For many reasons. They are not only amazing to look at, but also are numerous in the GLIMPSE data. They are tricky to measure but not impossibly hard. They are scientifically valuable objects to catalogue and measure the properties of, and they require more than one independent, human measurement to get a good handle on – this is key of course.

Many of the folks behind the ‘The Bubbling Galactic Disk‘ are part of the Project IX science team. We hope that everyone out there in the Zooniverse community can help refine and expand the existing bubble catalogue as part of Project IX. With the addition of new data, we also hope to find many new bubbles.

We are currently developing the bubble tool – the first user interface portion of the Project IX site  – which will have similarities to the Moon Zoo crater tool. We hope to be able to share it with you all soon so that you can help us to test and refine it. It is exciting to be able to involve everyone at this early stage.

If you’re interested in following this project and its take on bubbles, I’d suggest reading ‘The Bubbling Galactic Disk‘ and looking at the GLIMPSE website. If you have any questions – let us know. Bubble are just one thing we can see in the GLIMPSE data. More posts will follow about other scientifically useful objects lurking in this amazing infrared archive.



Star formation is one of the most important processes at work in the cosmos. The atoms that make up our planet and ourselves were made in the centres of stars, billions of year ago. To study star formation is to begin to understand the origin and make-up of the Galaxy and the Universe at large.

The mass distribution of stars and the rate at which they are born determines the nature and evolution of galaxies, such as our own Milky Way Galaxy. To understand many aspects of galaxy evolution, planet formation and cosmology, an understanding of star formation is required. It is one of the most fundamental mechanisms at work in the Universe.

Here at Zooniverse HQ we’ve been looking at how to get involved with the study of star formation for a while now. This is, in no small part, due to the fact that three of us at Zooniverse HQ have a background in star formation research. Chris Lintott, Arfon Smith and myself have all worked in this field and thus have been keen to make this project a reality for some time.

Project 9 is going to be the first Zooniverse contribution to the field of star formation. Project 9 is also going to be the first Zooniverse project to crowd-source more than just the science. We’d like to get opinion and feedback from the Zooniverse community as we develop the project.


Image Credit: NASA/JPLCaltech/K. Gordon (University of Arizona)

Project 9 will be using data from the Spitzer Space Telescope, one of the most successful science missions ever put in orbit (which took the stunning image of the Andromeda Galaxy seen above). We’ve been working with the people behind the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE). We think that you all may be able to help us classify some of the structures seen in this data – but more on that in a future post.

Stars form within dark clouds of gas (predominantly hydrogen and helium) and dust (larger molecules that have collected together into grains). They are dark because they absorb visible light. The dust in these star-forming regions absorbs visible light, and reemits it at infrared wavelengths. The result is that if you want to look for stars in the making, you must look in the infrared. The Earth’s atmosphere absorbs infrared light, so to search for star-forming regions you need to use a space-based infrared telescope – like Spitzer.


Infrared images of star-forming regions are often beautiful – you can browse a version of the GLIMPSE data via this link. We have been toying with different colour stretches for the GLIMPSE data to use for Project 9. Amongst the plethora of gorgeous images – from just a small part of the sky – I came across a familiar object: the Eagle Nebula (above). I thought this would give you an idea of the sort of images Project 9 will be asking everybody to help dissect and classify.

We’re looking forward to getting this project off the ground and will be blogging shortly with more details.