Cooling thermosphere

The thin blanket of gases that surround our beautiful planet is changing. Our atmosphere has changed many times in the past but many independent measurements show that it is changing particularly quickly these days. These changes have quite a few effects and some of them you might not expect. For instance, whilst increases in carbon dioxide in the atmosphere are warming up things down here on the surface, measurements show that the upper layers of our atmosphere are actually cooling. The reason for this is that they are thin and the extra carbon dioxide present isn't at a high enough density to cause a warming effect in those regions. Instead, the CO2 actually absorbs heat from its surroundings and emits it into space (the net effect). According to the Institute of Physics news item, the mesosphere (50-80km altitude) is cooling at 3 degrees Celcius per decade (measured over more than 15 years).

So what does this mean? Cooling down a gas generally causes it to contract which will mean that our atmosphere hugs the planet more tightly. This seems to have been confirmed by measuring the drag experienced by satellites in low Earth orbit. The drag has been decreasing implying that the density has been dropping by around a couple of percent per decade. This is probably good news for the owners of low Earth orbit satellites (and the International Space Station) as they will need less fuel to provide boosts to their altitude. However, I'm not sure I like the idea that the sky is falling ;-)

Posted in astro blog by Stuart on Wednesday 29th Nov 2006 (12:06 CET) | Permalink

Making an impact

Now for something to try at home. The Centre for Science Education at the University of Berkeley have a nice set of hands-on astronomy experiments that you can try at home. I quite like the look of the 5th experiment "Meteoroids and the Craters They Make". I just need to find a container, some flour, cocoa and some pebbles...

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Posted in astro blog by Stuart on Monday 27th Nov 2006 (14:12 CET) | Permalink

PM and Light Pollution

Light pollution is bad for so many reasons. It stops us seeing the beautiful night sky, it affects wildlife, adds to carbon emissions for no benefit and bright lights probably doesn't make us any safer. Now, if you're a British citizen (or resident/expat/in an overseas territory/a Crown dependency/in the UK Armed Forces) you can join a petition against floodlighting of Government buildings on the official 10 Downing Street website (seen via Davep).

This new petition feature is part of the Prime Minister's website and there are already many petitions about a whole range of topics. As it stands at the moment, more people would rather the Prime Minister stand on his head and juggle icecream (1146 names) and force all road designers to cycle on the cycle lanes they plan (259) than reduce light pollution (183) ;-). However, with so many petitions on topics both familiar (to those in the UK) and esoteric, I do wonder how much effect they will actually have on Government policy.

Posted in astro blog by Stuart on Monday 27th Nov 2006 (10:47 CET) | Permalink

NGC 1313

NGC1313 (RA 3h18m, Dec -66.5) is a pretty but strange barred spiral galaxy. It is about 15 million light years from us (to give some scale, our galaxy is a tad over 100,000 light years across) and as you can see from the picture below, it has lots of stars being formed in its spiral arms.

NGC 1313
The central parts of the starburst galaxy NGC 1313 obtained with the FORS1 instrument on the European Southern Observatory's Very Large Telescope CREDIT: Henri Boffin (ESO) and ESO
The reason I say it is strange is for a couple of reasons. Firstly, the centre of the galaxy (the point around which everything

rotates) doesn't actually correspond to the bar as you might expect. The second aspect of its strangeness refers to all the new stars that are forming in it. Most galaxies with lots of new star formation (starburst galaxies) have a reason for the starburst to occur. This is often because two galaxies have got close to each other and the gravitational interaction (or physical interaction) causes huge clouds of gas to be squashed or compressed and so trigger the birth of new stars at their cores. However, according to the ESO press release, NGC 1313 doesn't appear to have any neighbouring galaxies. A quick look at a combined UK Schmidt plate image (put your mouse over that image) shows that the outer parts of this galaxy are very disturbed with huge streams of gas that don't seem to correspond to the spiral arms in the image above. So, something has happened to this galaxy but nobody seems to be sure what. Whatever is causing the starburst it sure does look nice!

As if all this wasn't interesting enough, there are also two ultra-luminous X-ray objects in this galaxy. These have been seen by XMM-Newton, and measurements of them imply that they are both black holes with masses between 100 and 1000 times that of our Sun.

The image is available as wallpapers for your desktop at a variety of resolutions from the European Southern Observatory's website.

Posted in astro blog by Stuart on Friday 24th Nov 2006 (10:16 CET) | Permalink

Leonids fireball

This year the Leonid meteor shower didn't seem to be too impressive (see Davep and Ian for redux). Although I didn't see anything due to overcast skies where I was, Megan reports that a few people in the UK did catch an impressive fireball both visually and by radio observations. There are independent observations from Megan, David Entwistle and Andy Smith which all show radio reflections from a fireball trail at about 01:30 UTC on 19th November 2006. David Entwistle also appears to have seen this visually saying that it got to magnitude -8 and left a persistent train. Cool.

Posted in astro blog by Stuart on Thursday 23rd Nov 2006 (13:58 CET) | Permalink

Golf in space

Tom reports on the golf shot taken by Mikhail Tyurin, one of the cosmonauts on the International Space Station (ISS). NASA TV have a video of the shot (needs RealPlayer) and I must say that it is difficult to see anything. If there had been no audio, I wouldn't have even realised that a golf ball was being hit. Apparently, this intercontinental ballistic golf ball won't cause problems for the ISS or the Shuttle launch in December. I should hope not too.

Happy Thanksgiving to those people who know what it is. I'm told it is a time for food, family and football (presumably the American kind with lots of padding). Sounds like a good holiday to me.

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Posted in astro blog by Stuart on Thursday 23rd Nov 2006 (11:55 CET) | Permalink

V838 Mons: Slacker Edition

You may remember that a few weeks ago the Hubble Space Telescope released two new images of the beautiful light echo around V838 Mons. Unfortunately, nobody at ESA/NASA had thought to release all the images as a single animation, so I rolled up my sleeves and created one myself. Aaron over at Slackerpedia Galactica spotted it and asked me if they could use it. I agreed and the results are now available via Slackerpedia Galactica. You can also watch The Story of V838 Mon [FF] (MP3: 12.1 MB) via the Astronomy Media Player. I think they've done a great job.

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Posted in astro blog by Stuart on Wednesday 22nd Nov 2006 (20:16 CET) | Permalink

Mars Rover Lecture

The Open University were lucky enough to have the Mars Exploration Rover's Principal Investigator, Steve Squires, giving a lecture there a few weeks ago (spotted via Chris Lintott's new blog). I saw Steve Squires lecture at DPS2005 in Cambridge and that was really fantastic; his enthusiasm was contagious. The OU lecture is available as a webcast (you'll need Quicktime). It isn't aimed at a general audience but it gives a very good summary of what Spirit and Opportunity have been up to for the past couple of years.

Posted in astro blog by Stuart on Wednesday 22nd Nov 2006 (19:51 CET) | Permalink

Travels

This last week I've done a fair bit of travelling and that has meant I have not been able to exist in the virtual world of the internets. Instead, I was privileged to go to the European Space Agency's technology centre (ESTEC) in the Netherlands. That was very cool and I might write-up that trip at some point. Anyway, I'm now in Italy and back online.

Just checking back with the astronomy podcast world I see Slackerpedia Galactica have an amusing video vox-pop on the subject of Should Pluto be a planet? (MP3: 16.8 MB).

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Posted in astro blog by Stuart on Monday 20th Nov 2006 (11:03 CET) | Permalink

Copernicus crater mystery

Davep has posted about the latest developments on a puzzling observation announced on the Society for Popular Astronomy's bulletin board back in June. The puzzle was a bright point of light that Geoff Burt drew in one of his sketches of Copernicus crater. It looks like it may be a peak illuminated by sunlight but nobody of the SPA bulletin board is sure. So, Geoff is trying to re-image the crater, in similar illumination conditions, to see if it shows up again. Below is my quick and dirty animation that fades between Geoff's sketch and colour coded elevation data. I lined up the two images by eye using the crater wall on the left and the central peaks. Geoff's sketching skills are pretty good.

Copernicus crater
Copernicus crater animation CREDIT: Image by Geoff Burt,
elevation data from NASAs WorldWind, fade by Stuart
You may be able to help solve the mystery by making your own observations of the crater at Geoff's suggested times.

Posted in astro blog by Stuart on Monday 13th Nov 2006 (00:42 GMT) | Permalink

Multi-lingual podcast

One of the students at Jodrell Bank Observatory suggested that we release the Jodcast in languages other than English, as many people on the planet do not speak English. Translating the whole show seemed like a lot of work so we decided to just translate the news segment of the Jodcast. Several students at Jodrell Bank volunteered to do the translations so we now have the latest astronomy news in:

Over the weekend it is hoped that Japanese will be added too. Other languages that we may add include Spanish, Arabic and Farsi. Not only does this open up the Jodcast to more of the world, it could be used as a language learning aid! I'm off to practice my French.

Update (12 Nov 2006): It appears that our Japanese translator doesn't feel that his pronunciation is up to it. Are there any Japanese astronomers out there who would like the job of reading the news each month?

Posted in astro blog by Stuart on Friday 10th Nov 2006 (17:10 GMT) | Permalink

Mercury vs Venus

Here are two transit images that have been scaled so that the Sun is about the same size in each. The first image show a solar telescope (Halpha) view of Mercury crossing the Sun (still happening as I write this). The second shows Venus crossing the Sun back on 8th June 2004. It is interesting to see how the sizes of the two planets compare.

Mercury in H alpha
H alpha image from Hawaii of Mercury during transit on 8th November 2006 CREDIT: Haleakala Amateur Astronomers, Mauna Kea Visitor Information Station and Institute of Astronomy
Venus in H alpha

H alpha image from Jodrell Bank of Venus during transit on 8th June 2004 CREDIT: Anthony Holloway and Tim OBrien, Jodrell Bank Observatory

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Posted in astro blog by Stuart on Wednesday 08th Nov 2006 (20:32 GMT) | Permalink

Mercury live!

Well the interweb is struggling a bit under the volume of traffic but I am getting to see some images of the transit via the Exploratorium's webcast from Kitt Peak. The feed does keep stopping and giving me a "if you can see this you have realplayer" messages which is a tad annoying but it is live. Here is a screen shot showing Mercury (the seeing isn't brilliant):

Transit of Mercury
Mercury seen in silhouette against the Sun from Kitt Peak CREDIT: Courtesy of the Exploratorium

Posted in astro blog by Stuart on Wednesday 08th Nov 2006 (20:04 GMT) | Permalink

Mercury Transit Webcasts

Here is a more complete list of Mercury transit webcasts (I've just discovered that Ian has the same list doh!):

Posted in astro blog by Stuart on Tuesday 07th Nov 2006 (17:41 GMT) | Permalink

Transit of Mercury

Following on from the fantastic transit of Venus (where Venus passed across the disc of the Sun) back in 2004, we will shortly get to see the transit of Mercury. The transit occurs between 19:12 UT and 00:10 UT on Wednesday 8th November (put your mouse over the times to get them converted to your local time zone). Ian points out that this is early in the morning of the 9th November for those in New Zealand, Australia, Japan etc. From the times, you may have already worked out that Europe, Africa, the Middle East and parts of Asia will not get to see it; we'll be facing the wrong way at the time of the transit.

I will point out here that you should NEVER stare directly at the Sun or you are very likely to seriously damage your eyesight in a permanent way. However, if you are going to observe safely you will need a proper solar telescope or a helioscope. Alternatively, if you are on the wrong side of the planet (or clouded out!) watch the Exploratorium's live webcast from Kitt Peak Observatory.

Transit of Mercury
Global visibility of the 2006 transit of Mercury CREDIT: Fred Espenak/NASA

PlanetQuest have a podcast episode about the transit (MP3).

Posted in astro blog by Stuart on Monday 06th Nov 2006 (19:33 GMT) | Permalink

Fireworks

The weekend around bonfire night (Guy Fawkes night) is usually bad for observing because the entire world's supply of fireworks - or at least it seems like it - get let off. As well as the fireworks and the smoke from the bonfires there has also been a pretty full Moon so I didn't see much astronomical.

However, I did get to have my own fireworks display tonight on the motorway as a car swerved in front of me sending an impressive fountain of sparks flying up into the air. I was going a little under 70 mph (the speed limit) but I was able to break safely and pull into the hard shoulder (which became a road works layby at that point) so that the car behind didn't go into the back of me! Quickly, along with a few other people who had somehow managed to avoid the swerving car and also stop, we were able to check that the driver was OK and make sure that he got out of his car and off the road. I gave myself the job of waving oncoming traffic out of the inside lane (I was in the hard shoulder to be safer) until the Highways Agency arrived.

It turned out that the poor guy had fallen asleep at the wheel, swerved across two lanes, hit the central barrier and then swerved back across into the inside lane in front of me. He was a bit shaken, but apart from that he was OK; and most definitely awake! I'm pretty impressed that at least three cars and a coach had managed to avoid him and we all survived without a single injury. The only damage was to his car which he isn't going to be driving again by the look of the damage the crash barrier did to it.

Unfortunately it was mostly cloudy, otherwise I might have been able to have a nice look at the sky whilst stood waiting to have my details taken by the police (as a witness!). The section of the motorway that the accident happened on is in the Pennines, and the Highways Agency have put full cut-off covers on all the luminares along that stretch. As well as reducing glare for motorists, it seems to have greatly reduced the amount of light pollution. Well done to the Highways Agency for doing your bit to reduce light pollution.

Posted in astro blog by Stuart on Monday 06th Nov 2006 (01:19 GMT) | Permalink

Hinode first light

The Sun in X-rays
High resolution image of the Sun taken by the X-ray Telescope on Hinode CREDIT: JAXA
The Japanese Aerospace Exploration Agency (JAXA) tend to give their spacecraft new names once they begin their missions. So, Solar-B - the mission to study the Sun that was launched in September - has now been renamed Hinode which is Japanese for sunrise. The mission's three telescopes (the Solar Optical Telescope, the EUV Imaging Spectrometer and the X-Ray Telescope) have all seen first light and the first image from the XRT is to the right.

For the next month, tests will be performed to check that everything is working properly and, assuming it is, the science mission will begin in December. Currently the SOT is getting a resolution of 0.2 arcseconds and the XRT is reaching about 1 arcsecond.

Hinode is a collaboration between JAXA, the National Astronomical Observatory of Japan (NAOJ), NASA and the UK's Particle Physics and Astronomy Research Council. Go to the JAXA press release for more first-light images and Science@NASA for a podcast about Hinode.

With the successful launch of STEREO last month, it looks like an exciting time for studies of the Sun.

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Posted in astro blog by Stuart on Friday 03rd Nov 2006 (10:57 GMT) | Permalink

APoD interview

Now that the November Jodcast is finally out, I'll mention that Nick and I did an interview with Robert Nemiroff (MP3 5.4MB) who is one of the two people behind Astronomy Picture of the Day. He told us about how it all got started with Dr Jerry Bonnell back in 1995 when he thought the web was called Mosaic (the name of first web browser). Of course we had to ask how they find the images. Apparently, they get lots of images via the press officers at AAS and RAS but also from people from all over the world. They actually receive over ten times as many images as there are days, so the competition to be featured on APoD is pretty strong.

Dr Nemiroff also

tells us about his new book (Astronomy: 365 days) which has just been

published by Abrams and features the best images from APoD between 2003 and 2006. I've just got my copy from Amazon.co.uk and it is very nicely presented. I've had people going "oooohh" at it all afternoon.

Posted in astro blog by Stuart on Wednesday 01st Nov 2006 (17:52 GMT) | Permalink
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