Press release time from the ESLAB meeting

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ESA held a press conference a couple of hours ago to highlight some of the results from the ESLAB meeting. If you missed the live stream earlier, you can catch it here .

A number of major programs released some mouth-watering data to the general public, ranging from high resolution studies of massive star formation in our own Galaxy (the massive bubble RCW 120, which contains an embryonic massive Wolf-Rayet star, and huge star forming complexes in Aquila and Vulpecula) to studies of the high redshift universe (the H-ATLAS program).

The H-ATLAS field
Credits: ESA/ATLAS Consortium

A picture of the first field observed in the H-ATLAS survey, made by combining the images made with the SPIRE camera at 250, 350 and 500 microns. The colours in the image are not real but have been used to represent the different infrared wavelengths. The faint blue whisps at the top of the image show dust in our own Galaxy and the bright object just above the centre of the picture is a ‘Bok globule’, a dense cloud of gas and dust, also in our Galaxy, in which a small star may be forming. The other objects in the picture are all galaxies, at distances up to 12 billion light-years. The image shows that the survey is detecting objects in our celestial ‘backyard’ and also other, further ones that we are seeing as they were not long after the Big Bang.

Vulpecula
Credits: ESA/Hi-GAL Consortium

This image, in the constellation of Vulpecula, shows an entire assembly line of newborn stars. The diffuse glow reveals the widespread cold reservoir of raw material that our Galaxy has in stock for building stars.

Large-scale turbulence from the giant colliding Galactic flows causes this material to condense into the web of filaments that we see all over the image. These are the ‘pregnant’ entities where the material becomes colder and denser. At this point, gravitational forces take over and fragment these filaments into chains of stellar embryos that can finally collapse to form baby stars.

Aquila
Credits: ESA/Hi-GAL Consortium

At the centre and the left of the image, the two massive star-forming regions G29.9 and W43 are clearly visible. These mini-starbursts are forming, as we speak, hundreds and hundreds of stars of all sizes: from those similar to our Sun, to monsters several tens of times heavier than our Sun.

These newborn large stars are catastrophically disrupting their original gas embryos by kicking away their surroundings and excavating giant cavities in the Galaxy. This is clearly visible in the ‘fluffy chimney’ below W43.

The RCW 120 bubble
Credits: ESA/PACS/SPIRE/HOBYS Consortia

RCW 120 is a galactic bubble with a large surprise. How large? At least 8 times the mass of the Sun. Nestled in the shell around this large bubble is an embryonic star that looks set to turn into one of the brightest stars in the Galaxy.

The Galactic bubble is known as RCW 120. It lies about 4300 light-years away and has been formed by a star at its centre. The star is not visible at these infrared wavelengths but pushes on the surrounding dust and gas with nothing more than the power of its starlight. In the 2.5 million years the star has existed. It has raised the density of matter in the bubble wall so much that the quantity trapped there can now collapse to form new stars.

The bright knot to the right of the base of the bubble is an unexpectedly large, embryonic star, triggered into formation by the power of the central star. Herschel’s observations have shown that it already contains between 8-10 times the mass of our Sun. The star can only get bigger because it is surrounded by a cloud containing an additional 2000 solar masses.

Not all of that will fall onto the star, even the largest stars in the Galaxy do not exceed 150 solar masses. But the question of what stops the matter falling onto the star is a puzzle for modern astronomers. According to theory, stars should stop forming at about 8 solar masses. At that mass they should become so hot that they shine powerfully at ultraviolet wavelengths.

This light should push the surrounding matter away, much as the central star did to form this bubble. But clearly sometimes this mass limit is exceeded otherwise there would be no giant stars in the Galaxy. So astronomers would like to know how some stars can seem to defy physics and grow so large. Is this newly discovered stellar embryo destined to grow into a stellar monster? At the moment, nobody knows but further analysis of this Herschel image could give us invaluable clues.

The press release (which this post is based upon quite heavily!), and high-res JPEGS of these images can be found at the ESA Herschel web site.

Additional First Science press releases – which we’ll return to later – can also be found here.

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2 Responses to “Press release time from the ESLAB meeting”

  1. Kevin Jardine Says:

    I’ve put up a comparison of the Herschel and Spitzer images here:

    http://galaxymap.org/drupal/node/166

    Very, very exciting!

  2. Mark Thompson Says:

    Just wanted to leave a few more details on the H-ATLAS “Bok Globule” which we lovingly and informally refer to as The Blob!

    It’s cold, tiny and possibly just around the corner in Galactic terms – maybe less than 120 pc away. It does have some puzzling features (like a larger linewidth than expected for something so cold) and we’re trying to work these out right now. It looks just like other Bok Globules in the FIR, but has the distinction of perhaps being the first one to be found solely by its FIR emission – most other Bok Globules were found via being dark patches on optical images. At this galactic latitude the star densities are too low and the globule too small to have been found any other way.

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