Astronomy Podcasts

One of the latest crazes to hit the Internet is the phenomenon of podcasting; someone records themselves speaking and uploads the file to the Internet as an MP3 for others to download and listen to on their MP3 players.

I wondered if there were any astronomy related podcasts out there and it seems that there are, although there are currently only two of them. The first I found was Evan Demskeye's podcast which aims to cover the southern hemisphere, specifically South Africa. The second, and this suprised me a bit, was from Science@NASA who have been podcasting since November.

Posted in astro blog by Stuart on Thursday 30th Dec 2004 (12:11 UTC) | Permalink

Wind from Ophiuchus

Most people are familiar with the 12 signs of the zodiac as used by astrologers, but most will not have heard of the thirteenth astronomical constellations of the ecliptic (there are even more in the astronomical zodiac) that appears on modern star maps. It is named Ophiuchus, the Serpent Bearer, and sits between Scorpius and Sagittarius on the sky. The Sun passes through it in early December each year.

As it happens, there is an interstellar breeze of helium coming from the direction of Ophiuchus, which is focussed into a cone by the Sun. When the Sun is in the direction of Ophiuchus, the Earth passes through the cone allowing astrophysicists to study it. You shouldn't worry too much about its affect on the Earth though as, according to George Gloeckler, the breeze is a thousand billion billion times (1021 times) less dense than Earth's atmosphere. The Advanced Composition Explorer (ACE) spacecraft, located at L1, has been studying the helium wind and the project scientists have detected gusts in the wind. However, as they point out, these are most likely due to the solar wind buffeting the helium rather than structure in the interstellar wind itself.

Posted in astro blog by Stuart on Thursday 30th Dec 2004 (11:57 UTC) | Permalink

Einstein Year

The 2005 World Year of Physics, known as Einstein Year in the UK, is about to begin. The Daily Telegraph had an article by Roger Highfield that seems to go into quite a lot of detail about Einstein's discoveries. This isn't too suprising when you realise that Roger Highfield is a trained physicist and is currently that paper's science editor. Haven't got a lot of time then why not try some 'physics to go'; 20 different physics tricks you can try at home. Remember, physics is phun!

Posted in astro blog by Stuart on Wednesday 29th Dec 2004 (19:00 UTC) | Permalink

RFI and weather forecasting

It isn't just radio astronomers that are affected by radio frequency interference (RFI); meteorologists are finding it difficult to predict rain due to RFI. They passively use several different frequency bands, one of which is near the 22 GHz water vapour emission line. It is becoming harder and harder for them to use the data because man-made interference can't be distinguished from rainfall.

As I have said before, we need to protect some of the electromagnetic spectrum from development in the same way that we set aside National Parks. That way everyone can use them in a passive way.

Posted in astro blog by Stuart on Saturday 18th Dec 2004 (16:25 UTC) | Permalink

Light pollution becomes an offence

It seems that yesterday a Bill was published making light pollution a statutory offence. It is now possible complain to the local council about "artificial light emitted from premises so as to be prejudicial to health or a nuisance". However, some premises are exempt: airports; harbour premises; railway premises, not being relevant separate railway premises; tramway premises; bus stations and any associated facilities; public service vehicle operating centres; goods vehicle operating centres; lighthouses; prisons. It seems fair enough that lighthouses are exempt!

Posted in astro blog by Stuart on Thursday 09th Dec 2004 (17:34 UTC) | Permalink

Stars and light beams

The Washington Times had a good article on observing the stars on their website today. It mentions all the 'classic' constellations that are good to see from the northern hemisphere. The only thing I take issue with, is the description of why stars twinkle. My feeling is that many people could come away from that article with very peculiar notions of how stars twinkle. It describes pencil beams of light coming from the star that will sometimes miss our eye causing us to not see the star. That isn't a very good explanation as it assumes only one 'pencil beam of light' rather than a wavefront across the atmosphere. I will try to provide a better one below.

What happens is that the atmosphere refracts light; that is it changes the direction that the light is travelling in. If you have ever shone some light through a prism you will have seen this effect. Now the atmosphere is also constantly wobbling about and this means that the light is constantly changing the direction it is going. So when you look up at a star, it looks as though it is in slightly different places on the sky. Of course, the change in direction is tiny, but it does cause the star to look as though it is jittering about. At times when the atmosphere is more turbulent, the twinkling is worse. If the stars don't really seem to be twinkling, you can bet that the atmosphere is very stable.

Posted in astro blog by Stuart on Thursday 09th Dec 2004 (17:06 UTC) | Permalink

Polar Express

Yesterday I went to see the Polar Express on the IMAX in Manchester; the first time I have seen an IMAX film. It was quite a nice seasonal film and probably benefited greatly from the 3D nature of the IMAX experience.

So why write about it here? What astronomy does it involve? Well, without wanting to spoil the plot, the main character travels to the north pole on a magical train on Christmas Eve. For most of the film I managed to suspend my disbelief as magic was quite clearly involved and therefore there was no need to strictly obey the laws of physics.

At one point in the film they cross the arctic circle, which, as far as I remember, they correctly give as latitude 66 degrees, 32 minutes North. That was good but then they spot, off in the distance, the North pole. My immediate thought was that the North pole should still be another 33.5 degrees of latitude away and should not be visible.

However, I wasn't entirely correct. When they finally reach the 'North pole', they discover that it is Santa's city (postal address: Santa Claus, North Pole HOH OHO, Canada) and at the very centre is a raised stage which is actually styled like a compass with four points - a nice touch is that all four of them are labelled south. So they didn't travel to the actual North pole, they went to the magnetic North pole which is currently at about 82 degrees North. Taking into account that the movie was set 'many years ago' (say 1900) and the movement of the magnetic pole, it is probably fair to say that the magnetic North pole would be at about 71 degrees North. So that only leaves around 5 degrees of latitude (around 500 km) between the arctic circle and the magnetic north pole; still a bit too far beyond the horizon even in the best circumstances. It must have been magic.

Posted in astro blog by Stuart on Monday 06th Dec 2004 (17:12 UTC) | Permalink

Driving lessons in space

The occupants of the International Space Station (ISS) have been practicing their ability to maneuver the Soyuz spacecraft. Last week, Salizhan Sharipov and Leroy Chiao took a 24 minute trip in the Soyuz capsule to move it to a different docking port about 14 metres away. In that time, Soyuz and the ISS had actually travelled about a third of the way around the planet. I wonder if they remembered to check their mirror, signal and maneuver.

Posted in astro blog by Stuart on Thursday 02nd Dec 2004 (14:03 UTC) | Permalink

Density of the Sun

What is the average density of the Sun? Don't reach for Google or a handy book on astronomy, try to see if you can calculate it yourself. To make it slightly more interesting, you are not allowed to know the physical size of the Sun or even how far away from the Earth it is.

If you are thinking that you need a PhD to do something like that you would be wrong. The relevant maths is covered at G.C.S.E. level and the physics is taught at A-Level (hint). All that is required is knowledge of the constants pi and G - which can be measured on the lab bench - and some lateral thinking.

Perhaps I am a bit geeky, but I think it is quite cool to be able to work out the average density of the Sun, from the surface of the Earth, without any fancy equipment. Once you have worked it out, an interesting thing to do is compare the average density of the Sun to that of water (1000 kg/m³). Answers on a virtual postcard.

Posted in astro blog by Stuart on Thursday 02nd Dec 2004 (13:38 UTC) | Permalink
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