Sunsets 2.0

These days there is lots of talk of Web 2.0. As far as I can tell Web 2.0 is partly about social networking websites and partly about the construction and use of web-based services that people can adapt and combine to make cool applications that weren't possible (or nobody had thought of) before. Examples of the social sites are MySpace and Wikipedia whilst Google Maps is a great web service spawning a glut of spin-offs such as Frappr. There are other sites which I guess are a combination of the two such as YouTube and Flickr. These both have content created by the community and allow others to be imaginative with the use of that content.

Via Nick Bramhall I just found an inspiring use of the photo sharing site, Flickr. Flickr user jbum appears to have painstakingly trawled the site for images tagged sunset and over-plotted them using the photograph time-stamp and the day of the year. The resulting plot (follow the link and check it out) has an obvious sinusoidal curve that has an earliest time for sunset near the end of December and a latest sunset around the end of June. This is exactly what you would expect for a location in the northern hemisphere, as the earliest and latest sunsets are close to the summer and winter solstices (but not necessarily on them). It is really cool to be able to make a plot like this. It has either involved a lot of time and effort or a good amount of clever programming.

Looking at the plot, I was surprised by the width of the sunset line as it implies that most of the users of Flickr are in a fairly narrow range of latitudes and very few southern hemispherians choosing to take shots of sunsets! I guess that most of the users must be in the US, Europe and Japan as that would limit the latitude range and be biased towards the northern hemisphere. However, jbum has attempted to make a similar plot of southern hemisphere sunsets (I don't know how he filtered for hemisphere though) and that shows the opposite trend to the northern hemisphere. That is reassuring as it is what you would expect from a tilted, spherical Earth! But wait! He doesn't stop there. For a finale he plots a year of sunrises and a year of full moons.

I'm sure the creators of Flickr never imagined that their site would result in something like this. The web does produce some amazing results.

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Posted in astro blog by Stuart on Wednesday 28th Mar 2007 (17:40 GMT) | Permalink

Save the Earth

To help one of his kids get to sleep at night, Ian Musgrave started a competition on his blog. The idea is to think up ways to stop the Sun expanding at the end of its life. OK, we still have a few billion years before that happens - ignoring hypothetical physics in films such as the upcoming Sunshine - but Ian's competition runs out this weekend. If you have an idea, let him know soon. The winner gets a copy of the Southern Hemisphere's excellent Sky&Space magazine.

Posted in astro blog by Stuart on Tuesday 27th Mar 2007 (10:41 GMT) | Permalink

Make Ceres a Planet?

Personally I have found the whole debate about Pluto's status as a planet a bit depressing. Pluto, and its three known moons, is still incredibly interesting no matter what a whole load of carbon-based life forms on the third planet from the Sun may think. Following Dave P's mention that the state of New Mexico had declared Pluto to be a planet (only when Pluto is in the night skies though), the e-Astronomer points out that "Plutan Officials have so far not reciprocated by recognising the legitimacy of the State of New Mexico". Of course, the e-Astronomer has been suffering the wrath of Pluto-planet-proponents since his part in the re-classification of Pluto last summer but in a shocking turn-around he now wants Ceres reinstated to full planet-status. There is no Ceres petition in place yet (well, there is but it is the wrong Ceres) but no doubt it is only a matter of time.

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Posted in astro blog by Stuart on Monday 26th Mar 2007 (13:25 GMT) | Permalink

Cassini spots Jupiter

Tom's blog has a spectacular image of Jupiter taken by Cassini back at the end of 2000. Seeing it reminded me of a recent Cassini image of Jupiter from the other day. The 2000 image was taken as Cassini hurtled by the largest planet in the solar system but the most recent one was taken from its orbit around Saturn. That means that it was taken from a distance of 11 AU or roughly the same as the maximum separation of Earth and Saturn. In other terms, that is twice the distance that Jupiter is from the Earth and that makes the image even more impressive! I usually think of planetary missions as somehow being confined to the planet they are visiting so I'm always bowled over when they do 'real' astronomy.

Jupiter is imaged here from more than 11 times the distance between Earth and the Sun, or slightly farther than the average Earth-Saturn distance. CREDIT: NASA/JPL/Space Science Institute

Posted in astro blog by Stuart on Sunday 25th Mar 2007 (23:20 GMT) | Permalink

Balancing Eggs

The Spring Equinox was at 00:07 UT this morning. In the US there is a popular misconception that only at this precise time are you able to balance eggs on end. You can easily disprove this myth by balancing eggs at different times throughout the year but very few people seem to try it. The Bad Astronomer has a good book named, funnily enough, Bad Astronomy which expounds at great length the details of this myth's origins and why it just isn't true (PDF).

Back in November 2003 I bought quite a large box of eggs and tried it myself. November is nowhere near the Spring Equinox but as you can see from the image below, I had six eggs balancing simultaneously. No trickery is involved here but I did find that some eggs were easier to balance than others. In this photo the eggs are balanced on wood (part of a cheap Homebase shelving unit) as the carpet was too easy! However, I did balance eggs on a kitchen worktop as well. What I didn't manage was to get the eggs to balance upside down; I'll have to have another go at that. Plus, six was the most I got balanced in one go and I'm sure someone could do better.

Balanced eggs
Six eggs balanced on end on 19th November 2003. CREDIT: Stuart

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Posted in astro blog by Stuart on Wednesday 21st Mar 2007 (15:33 GMT) | Permalink

Vote for Art

Each year (except last year for some reason) the European Southern Observatory organise a competition called "Catch a Star!" with the aim to encourage school children around the world to find out about astronomy. ESO give various prizes for small teams and classes who have researched a topic in astronomy and been chosen by an international panel of judges. There is also an art competition open to individuals and prizes are awarded in five different age groups. The art competition is judged by a public vote so you can help your favourite images to win.

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Posted in astro blog by Stuart on Tuesday 20th Mar 2007 (12:03 GMT) | Permalink

Caves on Mars?

The BBC News website is reporting that 'cave entrances' have been spotted on Mars. This seems to come from a talk given at the Lunar and Planetary Science Conference (LPSC) held last week in Houston. The LPSC have the paper available on their website as a PDF. Below I've included a screenshot of Figure 1 from that paper which shows the features of interest.

Possible Martian Caves
Seven proposed cave skylights. Clockwise from upper-left: Dena, Chloë, Wendy, Annie, Abbey, Nikki and Jeanne. Arrows signify direction of solar illumination (I) and direction of North (N) CREDIT: G. E. Cushing, T. N. Titus, J. J. Wynne and P. R. Christensen
In the centre of each of the six regions you can see dark spots. These were initially found by looking at red light (654 nm) observations taken with the THEMIS instrument onboard Mars Odyssey. Using the THEMIS resolution of 18 m per pixel, they calculated that the features have diameters between 100 and 250 metres - equivalent to between 10 and 25 London buses parked end-to-end.

What are these features? Well, from the images above they certainly do look like holes in the surface. However, you have to rule out other possibilities first. The most obvious thing for them to be would be dark sand/rocks or impact craters. The dark rock idea is ruled out by infrared observations that allowed the authors to monitor the temperature changes of the features during the day; they didn't change in the way that you would expect rock/sand illuminated by the Sun to. So the second possibility is that they are impact craters. However, comparing them with neighbouring craters in the images above, you'll notice that they are very dark and sunlight isn't reaching the bottom of them. Knowing the time of day at each point on the surface you can work out the angle of the Sun at that time. If none of the bottom is illuminated, you can say that the hole must be deeper than a certain amount. The minimum depths calculated for these seven are between 73 and 96 m, but of course they could be deeper than this. These seem too deep and have sides much too steep to be craters. Having ruled out our two alternatives, the authors suggest that these are "sky-light openings into subsurface cavernous spaces" and the temperature measurements seem to back this up. However, the authors caution that more observations taken at different times of day (and therefore illumination angles) would help to confirm this.

The idea of caves on Mars is quite exciting because it may mean areas more conducive to the existence of life i.e. the temperature doesn't fluctuate too much during the day/year and the metres of rock/regolith above protect against harmful UV and high energy particles present at the surface. That being said, these particular caves seem quite unlikely as residences for subterranean lifeforms as they are located high on the flanks of Arsia Mons where the atmospheric pressure is even lower than normal for Mars - cold and lacking in atmosphere. Still, they might be interesting to future Martian speleological societies.

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Posted in astro blog by Stuart on Monday 19th Mar 2007 (19:19 GMT) | Permalink

Partial solar eclipse: March 19th 2007

If you live in eastern Russia, Kazakhstan, Mongolia, China, India, Nepal, Bhutan, Bangladesh, Myanmar, Thailand, Laos, Cambodia, Vietnam, Korea (North and South) and parts of Japan and Alaska, you should be able to see a partial eclipse of the Sun during 19th March. I make the start of the eclipse in about nine and a half hours from the time of this post i.e. the middle of the night for those of us in the UK!

NASA's eclipse website has a map showing the areas that can see it (I'm bound to have missed some countries from my list) and the amount of the Sun's disc which will be covered from each location. If you live in any of those countries, I hope you have good weather. As always, don't look directly at the Sun without proper eclipse glasses or, if you don't have those, use a projection technique instead.

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Posted in astro blog by Stuart on Sunday 18th Mar 2007 (15:16 GMT) | Permalink

Last few nights to help

As Ian points out, there are only a few more nights left to contribute to the Globe At Night project which is trying to get a global view of the problem of light pollution. The idea is to compare how many stars you can see in the constellation of Orion with the charts they have on their website. This is fairly easy to do although I've not been able to see any stars myself over the past few days due to cloud.

I've included the current map of UK/Ireland observations (below) showing a distinct lack of observations in Ireland, Scotland, North Wales and the north of England. Presumably this is due to the weather we've been having lately. We are also lacking observations in our big cities considering the huge numbers of people that live there. Observations from big cities are not useless and well help complete the big picture. So if it's clear tonight (or tomorrow), go outside and give it a try.

Globe at Night - UK
The UK distribution of observations for the Globe At Night project. CREDIT: Globe At Night/ESRI ArcWeb Services

Posted in astro blog by Stuart on Sunday 18th Mar 2007 (14:32 GMT) | Permalink

Our survey says...

Do you listen to the Jodcast? If so, or even if you have listened in the past but no longer do, it would be great if you could complete the Jodcast survey. I know that most people hate filling in surveys but this would be really appreciated and the feedback really will be used to improve the Jodcast in the future. It should only take about 5 minutes.

As well as making the Jodcast better, it is also important to show some aggregate statistics to the UK funding council (PPARC) that gave the Jodcast a small grant to buy recording equipment and other bits and pieces. After all, this is tax payer's money, so it is important that they know if it is being used well.

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Posted in astro blog by Stuart on Friday 16th Mar 2007 (10:32 GMT) | Permalink

Aurora from a plane

I've talked about the aurora (northern/southern lights) many times before. I've talked about them being seen from the ground, from space and even on Mars, but now I've just stumbled across a couple of images of the aurora seen through the tiny windows of commercial airliners. In the first image you can see the aurora in the distance behind the illuminated wing of a Boeing 737. Personally, I prefer the image from a 747 which has no light on the wing except for the reflection of some dramatic green aurora. From my attempt to image Orion from a plane last year I know how difficult it is to take photographs from a plane as the whole thing is constantly shaking and you have to look through scratched, double-glazed windows. I'm very impressed.

Posted in astro blog by Stuart on Wednesday 14th Mar 2007 (09:42 GMT) | Permalink

Saturn's rings full on: official version

Back in January I showed my attempt at putting together 27 images (9 in each of the colours red, green and blue) from the Cassini raw data to show Saturn's rings separated from the planet. I found that although I could get the rings to match up, the planet itself proved more tricky. In the end I gave up and it seems that the Cassini imaging team did too. They opted to just remove Saturn from the image entirely! I think the decision was probably correct as it gives a nice final result. Check it out the big version on the Cassini site.

Saturns rings
Saturns unlit rings alone, seen from an elevation of 60 degrees. Saturn has been removed from the image. CREDIT: NASA/JPL/Space Science Institute

Spotted via Paola.

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Posted in astro blog by Stuart on Monday 12th Mar 2007 (20:22 GMT) | Permalink

National Science and Engineering Week 2007

The UK's National Science and Engineering Week 2007 started yesterday and runs until 18th March. That makes it a week and a weekend but that doesn't sound quite as catchy. If you live in the UK you can find out what events are happening near to you via the British Association's website. This year you can also vote for the nation's favourite experiment and get the opportunity to win an Xbox 360.

Posted in astro blog by Stuart on Saturday 10th Mar 2007 (12:56 CET) | Permalink

The Best Sights in the Solar System?

The other day I got to thinking about what future Solar System explorers might consider to be the the top ten sights in the Solar System.

With the recent lunar eclipse it is perhaps inevitable that I would think eclipses might make a top ten list. So, to start with a couple of "easy to reach" sights, a solar eclipse seen from the Earth would be first on the list. The pictures I've seen all look spectacular and people I know that have seen one all think they are great. I haven't yet seen one myself because I was clouded out in Cornwall back in 1999. A second eclipse for the list would be a solar eclipse from the Moon (that would be seen as a lunar eclipse from the Earth). You would see the night side of the Earth surrounded by a thin, red ring of Earth's atmosphere - what a sight that would be! I was going to also suggest seeing the Earth from the Moon but you get this for free by seeing the eclipse!

Away from the Earth-Moon system, my next stop is Mars. Many people may suggest Olympus Mons as a great sight but I think I would prefer to see the amazing landscape that is Valles Marineris. It is over 3000 km long, 600 km across and about 8 km deep. The only trouble is that you wouldn't be able to see across it from the ground because the curvature of the Martian surface is too great. To get around this, some kind of balloon flight through the Martian atmosphere may be in order.

Following the recent images from New Horizons I think seeing huge volcanic plumes from Tvashtar on Io would be an essential stop in the Jovian system. Seeing Saturn and its Rings whilst stood next to the icy geysers on Enceladus may be quite cool too. It would certainly make a good photo.

OK, that brings me up to five, but these lists usually have ten entries. If you can think of any more essential sights that future Solar System travellers would go out of their way to see, please add them in the comments below.

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Posted in astro blog by Stuart on Saturday 10th Mar 2007 (11:29 CET) | Permalink

Zodiac removal

In one of my recent posts I talked about Hubblecast. I mentioned that the astronomers behind Hubblecast had MySpace pages with "Zodiac Signs" shown in their profiles. At the time I was unware that MySpace don't let you choose if this is displayed or not. They effectively force everyone to endorse astrology in this small way. I've since found out that several other astronomers (e.g. Pamela and Phil) not to mention spacecraft (e.g. Swift and GLAST) are in MySpace too. So perhaps it might be useful for people to be able to remove it if they want to.

I had a look at the code for the page and realised that if you are able to add your own style sheets (presumably people can because there are all sorts of personalised designs on MySpace) you could stop the Zodiac field being displayed using CSS. All you need to do is insert the following CSS somewhere in the page:

<style type="text/css">
tr#Zodiac { visibility: hidden!important; }

In the comments on the previous post I suggested the visibility:collapse attribute but Internet Explorer doesn't seem to like that so visibility:hidden will have to do. I don't have a MySpace account so can't test it properly. If anyone does, I would appreciate some feedback on the success or lack thereof of this little hack. Of course, better solutions are welcome so add them below.

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Posted in astro blog by Stuart on Friday 09th Mar 2007 (15:58 CET) | Permalink

How many stars can you see in Orion?

We often say that light pollution is a growing problem around the world and is stopping us from seeing the night sky. Late last year Dave Pearson mentioned a UK project to quantify the problem. This was partially thwarted by the fog that beset the country over Christmas. The other problem, from a web point of view, was that it was too UK-centric. Now (spotted via Dave again) there is a similar project which aims to quantify the amount of light pollution on a global scale.

The project is called Globe At Night and solves the issues of time zones and latitude by using the constellation of Orion which can be seen by most people around the world. Great! Once you've found your latitude and Orion (the hardest part of the whole thing) all you need to do is compare what you can see in the evening sky with the images available on the Globe At Night website. Then submit your results. If you want to take part in this huge global observation, you will need to observe Orion on one night between March 8th - 21st 2007. The more observations made, the better the results will be.

Posted in astro blog by Stuart on Wednesday 07th Mar 2007 (15:50 CET) | Permalink

Roman goddess of beauty

I was in Rome last weekend (I'm not gloating, honest) and was surrounded by so much history that it was difficult to take it all in. Around every corner seems to be some Roman ruin or other and I'm told that it is very difficult to build anything in Rome because you have to do an archaeological excavation first.

Where is the astronomy in this? Well the Romans believed in many different gods and they assigned the names of important gods and goddesses to the planets that were then known i.e. those that can be seen without the aid of a telescope. I am pretty terrible at remembering the names of Greek and Roman gods but one name I can remember is the Roman goddess of love and beauty, or Venus. The planet Venus is pretty beautiful to observe from Earth as it is often very bright in the evening or early morning. With the aid of a small telescope you can also see that Venus has phases just like our Moon. In fact this was the evidence that Galileo used to show that Venus must be orbiting the Sun rather than the Earth and helped show that the Copernican system worked better than the Ptolemaic system.

Whilst sat near the Colosseum (Colosseo) on Sunday evening, I spotted this ancient Roman goddess gracing the western sky. As I mentioned recently, I didn't have my camera with me but I was able to briefly borrow one from a friend and attempt a picture of the scene. The camera was a pretty basic digital camera without the ability to control the exposure length so, given that, I'm pretty happy with the results. One thing I've since realised is that just up the road to the right on this image is the Forum of Caesar where there are the remains of a temple to Venus Genetrix. So, all in all, a pretty good place to get a picture of Venus from. I got a picture of Jupiter from Venice

last year, so perhaps I should try to take a series with the planets

photographed from suitable locations. I wonder where I could try next.

Venus and Colosseum
The planet Venus seen next to the Colosseo (Colosseum) in Roma (Rome) on Sunday 4th March. CREDIT: Stuart

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Posted in astro blog by Stuart on Tuesday 06th Mar 2007 (15:10 CET) | Permalink


While looking at the Hubble site a few days ago I noticed that the folks at ESA have started a new video podcast named Hubblecast. The first episode is presented by an astronomer at the European Southern Observatory - Dr Joe Liske - who has particular interest in cosmology, galaxy evolution and quasars. The first episode talks about recently released HST images of a galaxy being ripped apart by a cluster of galaxies.

Dr J (as the HST site is calling him) even has a MySpace page, although I'm very disappointed to see that he hasn't removed the "Zodiac sign" field from his profile. Two other astronomers - Dr Luca Cortese and Dr Jean-Paul Kneib - will be involved with future episodes.

I've added Hubblecast to the Astronomy Media Player.

Posted in astro blog by Stuart on Tuesday 06th Mar 2007 (13:03 CET) | Permalink

Eclipse images

Will Gater has some great images of the recent lunar eclipse over on his astro-photography site. Check out his great montage showing the Moon from before the start of the eclipse until just before totality.

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Posted in astro blog by Stuart on Monday 05th Mar 2007 (21:01 CET) | Permalink


Wow! That is all I can say after last night's lunar eclipse and reading the brilliant comments from people in my last post. The eclipse seems to have inspired people all over the planet - except for people like Ian who were in the wrong place for once!

I had a great experience myself but then I had a great setting, great food, great wine and great company. I should probably explain that I've been in Rome this weekend and got to spend the eclipse at an Italian birthday party. The weather had been pretty overcast all Saturday, but luckily for me it cleared up shortly after the start of the eclipse. Not wanting to be totally unsociable, I didn't watch the entire eclipse but kept checking up on it every fifteen minutes or so. I must say that the last sliver of Moon to be eclipsed did seem to take ages to disappear but that may be down to my random checking and losing track of the time. The party was good (I even got to practice my limited Italian) and by the end perhaps about two thirds of the Moon had been re-illuminated.

My camera was many miles away (in another country) so I don't have any pictures. However, the circumstances made it a special eclipse for me and I have the pictures in my head at least.

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Posted in astro blog by Stuart on Sunday 04th Mar 2007 (21:53 CET) | Permalink

Total lunar eclipse: March 3rd 2007

I've been very busy for the past few days in various meetings (both useful and not so useful), so haven't had chance to add anything here. However, I had to take a couple of minutes to let you know about tomorrow's total lunar eclipse. A lunar eclipse is when the Earth gets between the Sun and the Moon so stops the Moon being illuminated. Actually, the Moon does get illuminated because the Earth's atmosphere acts as a lens to bend some light around onto the Moon. As the only light reaching the Moon has gone through our atmosphere, most of the blue light will be filtered out so the Moon will probably look orangy or red.

The eclipse is visible from most of the planet apart from New Zealand, eastern Australia, Japan, Alaska and most of the Pacific. There are several images on the net showing the eclipse visibility and times (starts from 20:16 UTC on Saturday night and lasts until 02:25 UTC on Sunday morning 4th March).

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Posted in astro blog by Stuart on Friday 02nd Mar 2007 (09:48 CET) | Permalink
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