The Possible Plumes of Europa

I was too busy yesterday to write a post about the latest hot news from the NASA Hubble Space Telescope, so here’s a quick catch-up.

It seems that Europa, the smallest of the four Galilean moons of Jupiter, may from time to time be releasing “plumes” of water vapour. It has long been speculated that there might be large quantities of liquid water under Europa’s extremely smooth icy crust. Here’s a picture of possible plumes (to the bottom left of the image) in which a high-resolution picture of the surface of Europa has been superimposed.

Picture Credits: NASA/ESA/W. Sparks (STScI)/USGS Astrogeology Science Center

There’s also short video explaining the possible discovery here.

It’s not obvious at first sight that features like that shown above are caused by water erupting through Europa’s surface. On the face of it they could, for example, be caused by the impact of a smaller body. However,  long-term observations of this phenomenon suggest out-gassing is much more likely.  The Hubble Space Telescope’s Imaging Spectrograph was used to study what are essentially Aurorae powered by Jupiter’s strong magnetic field in which the presence of excited states of hydrogen and oxygen provide evidence for the disintegration of water molecules through interaction with electrons in this highly energetic environment. The images were taken when Europa was in front of Jupiter so they are seen were seen in silhouette.

There is also evidence that these appearance of these plumes is periodic, and that they are more likely to occur when Europa is further from Jupiter than when it is closer. A plausible theory is that water is released from cracks in Europa’s surface which open and close owing to a combination of tidal gravitational and magnetic effects.

I wouldn’t say this was definite proof of the water interpretation. These observations push the capability of the Hubble Space Telescope to the limit because the features are so faint. For information here’s what the raw image looks like (left)  and with enhanced contrast (right):

 

Verification of these results through independent means is clearly an important priority, though likely to prove challenging. The plume interpretation is possible, but whether it is yet probable I couldn’t say!

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A Galaxy at Redshift 11.1?

Back in the office after one Friday off and there’s the inevitable queue at my door and mountain of things that just have to be done immediately. Yeah, right..

Anyway, I couldn’t resit a short blogging break to mention a bit of news that made a splash last week. This is the claim that a galaxy has been observed at a redshift z=11.1 which, if true, would make it the most distant such object ever observed. When I was a lad, z=0.5 was considered high redshift!

If the current standard cosmological model is correct then the lookback time to this redshift is about 13.4 billion years, which means that the galaxy we are seeing formed just 400 million years after the Big Bang. If it is correctly identified then it has to be an object which is forming stars at a prodigious rate. You can find more details in the discovery paper (by Oesch et al.)  here.

I have taken the liberty of extracting the following figure:

The claim is that the model spectrum on the top right is a much better fit to the data obtained using the Hubble Space Telescope Grism spectrograph than the two alternatives at much lower redshift. However, this depends a great deal on having a good model for the significant contamination from other sources. Moreover I’m sure the residuals are non-Gaussian and I’m not therefore convinced that a simple χ² is the best way to assess the fit. Obviously I’d like to see a proper Bayesian model comparison!

So, as I have been on previous occasions (e.g. here), I remain not entirely convinced. But then I’m a theorist who is always excessively suspicious of data. Any experts out there want to tell me I’m wrong?

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A Happy Hubble Coincidence

Preoccupied with getting ready for my talk in Bath  I forgot t post an item pointing out that yesterday was the 25th anniversary of the launch of the Hubble Space Telescope. Can it really be so long?

Anyway, many happy returns to Hubble. I did manage to preempt the celebrations however by choosing the above picture of the Hubble Ultra Deep Field as the background fo the poster advertising the talk.

Anyway it went reasonably well. There was a full house and questions went on quite a while. Thanks to Bath Royal Literary and Scientific Institution for the invitation!

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Andromeda in High Resolution

This afternoon I gave three hours of lectures on the trot, so I’m now feeling more than a little knackered. Before I head home for an early night, though, I thought I’d share this amazing video produced by the Panchromatic Hubble Andromeda Survey (or PHAT, for short), which is a Hubble Space Telescope (HST) Multi-cycle program to map roughly a third of the star-forming disk of the Andromeda Nebula (M31), using 6 filters covering from the ultraviolet through the near infrared. With HST’s resolution and sensitivity, the disk of M31 is resolved into more than 100 million stars. The combination of scale and detail is simply jaw-dropping. Hat’s off to the PHAT team!

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Hubble + Beethoven

In an attempt to get away from the horrors of the last few days I thought I’d offer this video I just found on Youtube. It features majestic, life-affirming music from the 2nd Movement of Beethoven’s Symphony No. 7 in A Major along with some wonderful astronomical images from the Hubble Space Telescope. Science and art for all humanity. How pathetic our petty squabbles appear when we think about the Universe or listen to great music.

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Hubble Images With Music By Herschel

Too busy for a full post today, so here’s a little stocking filler. The, perhaps familiar, pictures are taken by the Hubble Space Telescope but the music is by noted astronomer (geddit?) Sir William Herschel – the Second Movement of his Chamber Symphony In F Major, marked Adagio e Cantabile. Although best known as an astronomer Herschel was a capable musician and composer with a style very obviously influenced by his near contemporary Georg Frideric Handel. Although music of this era puts me on a High Harpsichord Alert, I thought I’d share this example of music for those of you unfamiliar with his work…

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Cosmology Webcasts Coming Up…

Courtesy of freelance science writer Bruce Lieberman, whom I met briefly at the recent “Origin of the Expansion of the Universe” meeting in Flagstaff, AZ,  here’s a plug for two live webcasts on topical topics that are coming up in the next couple of weeks. On behalf of the Kavli Foundation, Bruce will be interviewing astronomers about the new Hubble XDF image (Oct. 4) and the new Dark Energy Survey camera, which just saw First Light (Oct. 11).

Live Q&A and Webcast: What Does Hubble’s Deepest Image of the Universe Reveal?

Click on the above heading for  direct link to webcast.

October 4, 11-11:30 am PDT (18-18:30 GMT; 19-19:30 BST)

Using data from the Hubble Space Telescope, a multi-national team of astronomers recently released our deepest-ever image of the
universe. Pascal Oesch, a Hubble Fellow at the University of California at Santa Cruz, and Michele Trenti, a researcher at the Kavli Institute for Cosmology, Cambridge at the University of Cambridge in the U.K., answer your questions about how the image was created and what it reveals about the early universe.

Viewers may submit questions to the two Hubble researchers via Twitter using #KavliAstro or email to info@kavlifoundation.org.

Live Q&A and Webcast: Can a New Camera Unravel the Nature of Dark Energy?

Click on the above heading for  direct link to webcast.

October 11, 9-9:30 am PDT (16-16:30 GMT; 17-17:30 BST)

Scientists have great expectations for the newly operational Dark Energy Camera, which may significantly advance our understanding of the mysterious force expanding the universe at an ever accelerating rate. Fermilab scientists Brenna Flaugher, project manager for the Dark Energy Camera, and Joshua Frieman, director of the Dark Energy Survey, answer your questions about the camera and what it’s expected to reveal.

Viewers may submit questions via Twitter using #KavliAstro or email to info@kavlifoundation.org.

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