Category Archives: News

The Most Distant Bubble?

A little while ago Sarah Fitzmaurice, a work experience student at Zooniverse Oxford, spent a week working with the Milky Way Project database. She did some fun things with the data, including plotting the locations of many of the bubbles according to their distance from us. For many, the current canonical view of our own Galaxy comes from a combination of data sources, compiled by Robert Hurt, working at NASA JPL. The image is shown below, and you may recognise it: we use it as our Twitter/Facebook avatar. It is an artist’s impression based on several data sources and guided by astronomers.

The Milky Way may be our home in the Universe but we know startlingly little about it. On key missing piece of information for many objects in our Galaxy is their distance from us. From the Spitzer data alone, we do not know the distance to the bubbles in the MWP. For our first Data Release paper, we compared the MWP Bubble catalogue to known objects, some with distances, and this allowed us to find  out how far way some of the bubbles are. This enables us to investigate how large and sometimes how massive they may be.

During her work experience week, Sarah plotted the bubbles with known distances onto Robert Hurt’s map of the Milky Way. The result is shown below. The bubbles are marked with crosses, and the size of the cross shows the relative size of the bubble. The distances to these bubbles were derived by comparing them to a known set of radio sources that are expected to look like bubbles in Spitzer data.

You can see that the bubbles generally follow the distribution of spiral arms and that it is easier to see the bubbles nearby than those farther away. This is good because it is roughly what we expect. This map also allows us to easily spot the isolated, nearby or most-distant bubbles in the project. Much of Sarah’s week was spent looking at each of the interesting bubbles and finding out some more about them.

Although there may well be more distant bubbles in the catalogue, Sarah’s map provides a candidate for ‘most distant bubble’ in the MWP. It is one of a pair of bubbles located on the far side of the Perseus arm, almost 45,000 light years away from the Sun – in the top part of the above image.

Using the new MWP coordinates tool we can take a look at this distant object, and two nice images of it are shown below. Our ‘most distant bubble’ is actually located within another larger, clearer bubble, the image of this is also given. This is a line-of-sight effect and they are not necessarily near each other.

This bubble is located literally on the other side of our Galaxy and is roughly 15 light years across. The fact that the two bubbles are positioned on top of each other makes it hard to decide which one is farther away. There are many more instances where bubbles lie on top of each other where it would be impossible to decide which is actually on top of which. The nebulous material of which these objects are made makes them hard to disentangle. In this case there are stars and IR objects on top of the smaller bubble that make it easier to pick out the nearer and farther bubble.

In this case, the distance value is derived from a radio source that we expect to be associated with a bubble. Both of these bubbles lie at roughly the correct position to be associated with the radio source. Since we know the radio source is very far away, we can say that the smaller bubble is most likely the object associated with the radio source.

These kinds of confusing caveats are one of the things that make Galactic astronomy difficult and challenging. For these reasons, this might be the most distant bubble we know of in the MWP – or it might not. Either way, this awesome little bubble has provided the opportunity to discuss the ways that we determine the distances to objects in the MWP catalogue, and how doing astronomy in our cosmic backyard is tricky territory indeed.

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Triggered Star Formation

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There’s a new Milky Way Project paper out on the arXiv. It was submitted to the Astrophysical Journal last week and concerns the topic of the triggered formation of massive stars. This study was lead by Sarah Kendrew and utilises the results of the first MWP paper (our catalogue of bubbles).

One of the main reasons for undertaking the MWP was to produce a large bubble catalogue that would allow statistical studies of star formation sites in our Galaxy. In the end we produced a list of bubbles ten times larger than the previous best catalogue in our first data release (DR1).

In this new study, we’ve used statistical techniques to see what correlations exist between the MWP bubbles and the RMS Catalogue: a well-used catalogue of infrared sources along the Galactic plane (a similar region to that covered by the Spitzer data used in the MWP).

The paper looks for any signs that there is a correlation between the positions of RMS sources and the positions of the MWP bubbles. Specifically we’re trying to see if such massive young stellar objects (MYSOs, stars being formed) are most commonly found on the rims of bubbles. If this is true, then it adds to evidence for a mode of star formation where the formation of some stars triggers the formation of others. In this case, young, hots stars blow out a bubble in the interstellar medium. During this process, clumps of material occur in which new stars condense and form.

This new study finds a strong correlation between MYSOs and the MWP bubbles. We find that Atwood thirds of the MYSOs surveyed are associated with bubbles and 22% are associated with bubble rims. We also see that larger bubbles are more likely to have MYSOs on their rims – though one of the main issues we encountered is that the effect of line-of-sight confusion makes the situation complicated.

This second paper is the first to follow on from the MWP DR1 paper, and there are more planned. You can read the paper on arXiv. The Milky Way Project itself, and this study, we’re presented at the UK/Germany National Astronomy Meeting this week in Manchester.

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Milky Way Project Refresh

We’re excited to announce that we have updated the Milky Way Project to show you more bubbles and to produce even more science! After creating our catalogue of 5,106 bubbles earlier this year, we’re aiming to try and refine and improve our measurements of the MWP Bubble catalogue by asking you to measure each and every bubble in greater detail. This means that for a while we’ll no longer be displaying images from across the plane of our Galaxy, but instead we’ll just be showing you images of regions where you told us that bubbles are located.

Our recently accepted Data Release 1 (DR1) paper, ‘A Bubblier Galactic Disk‘ is already online and being used by astrophysicists to help better understand star formation in our Galaxy. Later this month we’ll be presenting the MWP at the UK/Germany National Astronomy and SEO Consultant Meeting in Manchester. We will hopefully be able to bring you some updates at that time so you can follow along. In that paper we estimated that our rate of discovery of new bubbles had declined over time to the level where only a few new bubbles were being discovered each month. This make sense of course. The more people that inspect all the images on the site, the less likely it is for a bubble to remain undiscovered. What becomes important are the multiple, independent drawings of each bubble. To reflect this, we have updated the MWP site to shift from showing random portions of the Galaxy, to showing the places we believe there are bubbles – based on your classifications. Each image you are now shown on the site contains one of the 5,106 bubbles contained in the DR1 catalogue. It’s seems really fitting that the MWP community is now inspecting the very catalogue it created.

This update to the site has two effects. First of all it means that you are able to see each bubble more clearly and thus make more precise measurements of their shape, size and thickness. It also means that you see a lot more bubbles! There now ought to be at least one bubble in every image, which is a lot of fun. It also means that Talk has been updated with a host of new bubble-centrd images, showing off all 5,106 of the DR1 catalogue’s bubbles.

We have made some other updates to the site as well. We have put up our contributors page, which lists the names of everyone that made the DR1 paper possible. We have also finally added the term ‘Yellow Ball’ to our list of objects you can mark in images. The #yellowballs are a term coined on Talk by the MWP community and turn out to be interesting to researchers at they appear to represent ultra-compact star forming regions.

Don’t forget to follow us on Twitter @milkywayproj for the latest updates, and our Facebook page too.

Data Release 1

We submitted the first Milky Way Project paper to the Monthly Notices of the Royal Astronomical Society (MNRAS) in December and the referee has been very kind to us so far. We have our fingers crossed for acceptance soon. Thanks to recent media coverage and some awesome buzz at the recent AAS meeting we decided to go ahead and post our paper to the arXiv yesterday. In addition to the paper, which explains how the catalogue was created from all your bubble drawings, we have also made the data available on the MWP site. You can explore the data graphically or download various files on our data page.

DR1

Data release 1 (DR1) currently consists of a catalogue of large bubbles, a catalogue of small bubbles and a set of ‘heat maps’ (more on that in a moment). We are aiming to add green knots, red fuzzes, star clusters and galaxies to this list later in the year. We’ve called it DR1 because we also hope to refine and improve our catalogue – partly based on feedback from the community – and release a second set of data (DR2) later in 2012. Hopefully 2012 will be a big year for the project!

We have also nearly finished the process of cresting our ‘heat maps’. These are the maps of raw clicks that show the true crowd-sourced view of where bubbles are locate din our galaxy. they look amazing and are incredibly detailed and rich. They represent something new for the Zooniverse, and for the scientific community, and it will be interesting to see if they can be useful when released into the wild. If you’d like a sneak peak you can download one of the 3°x2° regions of the galaxy here and try it out – this is the region seen in the image above. It is a 5.4 MB FITS file, centred around 18° Galactic longitude and shows the raw bubble drawings that were used in the DR1 release. Every bubbles is given the same, tiny opacity and so as the bubbles coincide we start to see the regions of the sky where every agrees that bubbles are present. (A 220 MB file of public Spitzer data for this region can also be download as FITS here, for comparison.)

The other big change that we need to make to the site in the next few days is the release of an official ‘authors’ page, crediting all our citizen scientist volunteers. 40,000+ individuals have taken part in the MWP and those who contributed to DR1 will be credited on the site soon. I’ll blog when that happens to let you know.

Keep Clicking!

All of this doesn’t mean the MWP is over though: far from it. In fact, the classifications you make now will be collectively refining and improving the data we have produced so far. We  have plans, which i’ll explain at a later time, to modify the MWP interface so that each classifications contributed more efficiently to the final result. We also have new data to come in 2012 that will mean we can search for bubbles in whole new regions of the sky. Very exciting and there is much to look forward to in 2012!

Exploring the MWP: Coordinates and SIMBAD

One of the most common questions posted on Milky Way Talk is “What is [that thing] in this image?”, and science team members try to respond to some of those where we can. The galactic plane is so incredibly rich at these infrared wavelengths and the Galaxy is so vast that even with the combined experience of the whole science team we usually don’t know the answer.

To help everyone out, we’ve created a new tool that lets you search one of the world’s best astronomical databases from within the Milky Way Project. SIMBAD is a huge astronomical database, maintained by the Centre de Données astronomiques de Strasbourg (CDS) and contains 7 million astronomical objects documented in the literature. When astronomers want to see what is known about any part of the sky, many of them start with a SIMBAD search. Our new Coordinates Tool lets you search the images from the MWP for SIMBAD data, to help show you what different objects are.

The Coordinates Tool

You access the new Coordinates Tool directly at http://www.milkywayproject.org/tools/coordinates/

This will take you to a default page, exploring the area around the coordinates 0, 0. The MWP images use the galactic coordinate system, which expresses positions in galactic latitude and longitude – concepts that should be familiar if you know about geo-coordinates here on Earth. The “equator” of the galactic coordinate system (the latitude = 0 position) is roughly coincident with the disk of the galactic plane.

Looking down on the galactic plane (Image: NASA/JPL-Caltech/R. Hurt)

In this picture, the galactic latitude tells you how much an object lies above or below the plane of the Galaxy, and the longitude specifies the angle away from the Galactic Centre. The above image shows a schematic diagram of what we think the Milky Way Galaxy looks like, with an indication of our own location and a galactic longitude grid. Galactic latitude runs from -90 to 90 degrees, and longitude from 0 to 360 degrees, although sometimes you may also see it noted as -180 to 180 degrees.

To search the area around any set of coordinates, you simply include them in the URL for example, to search one of my favourite regions, at longitude 18.4 degrees and latitude 0.2 degrees, you would visit

http://www.milkywayproject.org/tools/coordinates/19.0/0.0/

This will display one of the MWP images that containing those coordinates (see below). It will also list the other MWP images containing these coordinates. This lets you explore the region at different scales and in different contexts. The specified coordinates are shown on the image with a box. A link to the image’s Talk page is also included.

You’ll see that as you move the cursor around the image, coordinates are displayed to help you navigate. You can double click on any point to jump to that centre and see the images available. By default a small, square box is drawn onto the target area. If you want to draw a specific box you can give the width and height (in arc minutes) as URL parameters:

http://www.milkywayproject.org/tools/coordinates/19.0/0.0/?h=15&w=30&zoo_id=AMW102de6d

You can also reach the Coordinate Tool from the main Explore page. just double click on the map to just to more detail on that region. A link has also been placed on the images in the My Galaxy section of the site, for logged in users.

SIMBAD

Also present on the Coordinate Tool is a button with the words ‘SIMBAD Search’. Clicking this performs a SIMBAD search on the current viewing area and displays the results directly on the image. Here’s an example from the URL I gave above:

Any objects SIMBAD finds in the astronomical literature are displayed as circles. If,you hover your mouse over them you will see their object name and type. Clicking on these objects takes you to the objects page on the SIMBAD site, where you can find out more.

Many of the objects found in the MWP will be stars – the galaxy is full of them! – and many will be IRAS and 2MASS objects – these names derive from previous infrared surveys that mapped the regions covered by the MWP data. In the above image you can see one 2MASS object near the centre of the bubble on the right:

The SIMBAD page for 2MASS J18252813-1224187 explains that may be an Asymptotic Giant Branch (AGB) star. These objects are interesting, and there are plant of them to be found in the MWP images.

Some interesting regions that are worth a SIMBAD lookup with the tool include the rim of a broken bubble, a dying star and the pulsating heart of a gorgeous bubble.

This tool is still a bit rough around the edges, but we are keen to invite comments and ideas from anyone that would like to try it out. You can either leave comments on this blog post, or email us on team@milkywayproject.org. We have more updates on the way!

First Paper: A Galaxy of Words

The first Milky Way Project science paper has been submitted! We sent off our manuscript to the Monthly Notices of the Royal Astronomical Society just yesterday – exactly one year since the launch if the project. Now we wait for the process of peer-review to get kick-started. Our paper will be sent to an independent referee – another researcher in astronomy – and usually we would then get some corrections along with a thumbs-up or -down for publication in the journal.

In the field of star formation it is customary to wait until the referee has given us the OK before we publish a pre-print of the paper online. So we will keep you posted on progress – including posting a PDF of the paper when its time – as we move toward publication.

In the meantime, as part of the Zooniverse advent calendar we’ve produced a slightly different version of the paper for publication right now! This ‘word galaxy’ is a representation of the content of the paper – but in beautiful spiral form. The most common words in the paper were MWP (214 times) and bubbles (283) so they are largest. The words scale all the way down to disk (3 times) and ‘tend’ (2 times).

Have fun exploring the paper in this form until we can get the real one to you in the next few weeks.

[Download large version 2.6 MB]

Bok Globules and Herbig Haro Objects

ResearchBlogging.orgThe Milky Way Project science team are currently busy laying what we hope is the final hand on our first publication. In this paper, we’ll describe the project and why we decided to take the citizen science approach for the task of identifying bubble structures in the Galaxy. We will also present our first results from the hundreds of thousands of classifications we’ve logged on the site, and how our new bubble catalog might be useful for further studies of star formation and the interstellar medium. As we’re big fans of open data sharing, the paper will of course be made publicly available via Arxiv.

I spotted a bunch of interesting questions on the Milky Way Project Talk forums recently and wanted to take some time to jot down a few answers. Here the first one (or in fact, two).

User Ken Koester asks:

  1. Is the resolution of these images such that we ought to be able to detect Herbig Haro objects?
  2. Bok globules are pretty cold; do they still show as black in these images?

Herbig-Haro objects were first discovered in the early 1950s by, not surprisingly, astronomers George Herbig and Guillermo Haro, who spotted optical nebulosity in active star forming regions like Orion. Decades of further observations in the optical, infrared and radio have since established that these “nebulae” are bright knotty streams or jets, sometimes with a very marked bipolar and narrow shape, streaming out from newly forming stars. This type of powerful outflow of material is a typical feature of star formation at all different masses.

The optical radiation seen from these Herbig-Haro flows arises when material in the outflow powers into the quiescent medium surrounding the new star, causing shocks in the gas. Such shocks are also commonly seen in the infrared. In the Spitzer bands of observation, shocks are particularly prominent in the 4.5 μm channel – the blue channel in our Milky Way Project images. Outflows come in variety of size, and of course their apparent size depends on how far away they are. But the resolution of Spitzer is certainly sufficiently high to spot them.

If you want to know more about these objects, there are two excellent review articles from Annual Reviews of Astronomy & Astrophysics on the topic:

Schwartz, R. (1983). Herbig-Haro Objects Annual Review of Astronomy and Astrophysics, 21 (1), 209-237 DOI: 10.1146/annurev.aa.21.090183.001233 [ADS]

Reipurth, B., & Bally, J. (2001). Herbig-Haro Flows: Probes of Early Stellar Evolution, Annual Review of Astronomy and Astrophysics, 39 (1), 403-455 DOI: 10.1146/annurev.astro.39.1.403 [ADS]

Bok globules are very dense and compact cloudlets that are forming new stars in their interiors. They appear black in optical and infrared images, as they’re too cold to emit any radiation shortward of around 100 μm. To study what’s happening on the inside, we have to observe at those wavelengths and beyond, which are covered by e.g. the Herschel Space Observatory and millimeter telescopes such as IRAM or ALMA. They should be visible in our images, as they appear dark in all our colour channels. But not many are as distinct-looking as the ones we see in beautiful Hubble images like this one, so they can be very hard to spot.

The Spitzer image below of a giant Herbig-Haro flow inside a Bok globule towards the constellation of Vela, at a distance of 350 pc (1140 lightyrs), combines light at 3.6 µm (blue), 4.5 and 5.8 µm (green) and 8.0 µm (red). The colours used are a little different than in our Milky Way Project images, which use 4.5/8/24 µm respectively. The image below looks at an area on the sky of 10.2 x 6.5 arcminutes, which is just slightly closer in than the highest zoom level of the MWP images (18 x 9 arcmin). Compared to other H-H objects, HH46/47 is really enormous, so other outflows are likely to appear much smaller.

Spitzer’s view of a giant Herbig Haro flow, HH46/47, inside a Bok globule (Image: NASA/JPL-Caltech/A. Noriega-Crespo (SSC/Caltech), Digital Sky Survey).