New Extrasolar Planet

A group of astronomers from the Canaries and the US have just announced the discovery of a new planet, outside the solar system, that they have called TrES-1. Their paper will be published in Astrophysical Journal Letters but has been on astro-ph since Monday. The planet has about three-quarters the mass of Jupiter although with an orbital period (year) of just over three days, it is certainly much closer to its star than Jupiter is to the Sun.

In this paper two small (10cm) aperture, wide-field (6 degree) telescopes (Stare and PSST), were used to observe the same patch of sky at different times as they were at different longitudes. As planets don't give off their own light - by definition - there are several ways to spot planets around other stars including transits, the Doppler effect and microlensing. Each of these methods detects different types of planet/star. In this case, they used the transit method to watch for a drop in brightness of the star around which the planet orbits.

As anyone who saw the Venus transit will realise, a planet doesn't really cause a very significant drop in the amount of light from a star. Making your equipment very sensitive to changes in brightness can only help so much as the atmospheric seeing can cause a larger changes in brightness (think twinkling). Other than using a telescope in space, a way to get around this is to observe the brightness over time and then 'fold' the data up; basically split the data up into chunks of a specific time and then add all the chunks together. This might seem crazy but it means that if you happen to choose the chunk size to be the same as the orbital period of the planet, the dip in light from the star starts to stand out from the 'noise'. This method is well used in astronomy with many pulsars being found this way.

Posted in astro blog by Stuart on Wednesday 25th Aug 2004 (15:38 UTC) | Permalink

Brightest and the best

For the last three weeks I have been house, dog and car sitting for some friends of mine who live not too far away. Tonight, after I had taken the dog for a walk, I got talking to the two teenagers who live next door. I was grilled about A-levels, college, university, life and finally astronomy. One of their questions was "how do you get paid for doing astronomy?". Good question; I often wonder how it is that astronomers get paid for trying to understand the universe. Long may it continue!

Anyway, there were only a few clouds around and it was past 10pm so I asked them if they knew how to find the north star (Polaris). James, the eldest of the two, told me that it was the brightest; a mistake that so many people make. I guess this is because everyone knows the north star is important so they assume it is the brightest. I explained that this wasn't the case and that I thought it was something like the 49th brightest star in the sky. Once I got home I checked, and it turns out it is actually 51st on the list of the top 100 brightest stars (hey, a programme idea for Channel 4). The 100 brightest shouldn't be confused with the 100 nearest stars either!

It was great that they were interested and I even ended up explaining about the precession of the equinoxes and the fact that the north star will not always be Polaris - in 14,000 AD it will be Vega.

Posted in astro blog by Stuart on Saturday 21st Aug 2004 (23:59 UTC) | Permalink

New Moons

It has been a busy week for Moon hunters. On Monday, it was announced that two new moons had been found around Saturn by Cassini, and yesterday there was a report that five new moons had been discovered around Neptune using the Canada-France-Hawaii Telescope. That takes their totals up to 33 and 13 respectively.

Posted in astro blog by Stuart on Thursday 19th Aug 2004 (16:26 UTC) | Permalink

Afternoon Play

Tomorrow's afternoon play on Radio 4 is called Kepler. According to the website it is:

An exploration of the clash between two of the 17th century's leading astronomers - the assured, prickly and self-mocking Johannes Kepler, and the aristocratic, overbearing and secretly insecure Danish nobleman, Tycho Brahe.

Posted in astro blog by Stuart on Tuesday 10th Aug 2004 (18:06 UTC) | Permalink

Enlightened Views

I have been campaigning against light pollution for some time and last year Megan and I set up the campaign against light pollution in the North-West on BBC iCan. Recently, in some of the publicity in Physics World (published by the Institute of Physics), for World Physics Year 2005, there was mention of a 'relay of light' which would go all the way around the globe in one night. As you might guess, shining lots of light up into the sky is not the sort of thing an astronomer likes even if it is to be a one-off event. The contribution from that one event is obviously not going to be long term but it does set a bad example to the rest of the world. How long before this sort of thing happens to promote other things?

Today the BBC News carries a story about the fact that the Institute of Physics has decided not to support the plan because of the "public perception" that physicists are clashing with astronomers. Prof Kalmus, who represents the IoP on the steering committee for WYoP2005, said:

"Some complaints were merely abusive and appeared to be based on ignorance. But others were more thoughtful and pointed out that although the scheme would not affect astronomical observations, it could set a bad precedence, for example to commercial organisations that might wish to illuminate the night sky with advertising."

Posted in astro blog by Stuart on Tuesday 10th Aug 2004 (16:10 UTC) | Permalink

Perseids

This is a good year to watch the Perseid Meteor Shower as the Moon won't be full and therefore 'drown out' the showers. Meteors are often called shooting stars although they aren't stars but lumps of rock and ice falling through the atmosphere. The Perseid Meteor Shower is so called because if you follow the trails of the meteors backwards, they all seem to originate from the same point (the radiant) which is in the constellation of Perseus. Ian Morison says the best place to look is about 50 degrees away from the radiant point. We may see an early surge tomorrow night at about 10pm BST but the main showers are due for 12th and 13th August at about 23:30 BST.

Posted in astro blog by Stuart on Tuesday 10th Aug 2004 (13:26 UTC) | Permalink

UTC vs GMT

I wouldn't have thought that UTC often crops up in discussions in the House of Lords, but it seems that it did back in June 1997. They were discussing a Bill that would change all references of GMT to UTC, in the Interpretation Act 1978. Lord Tanlaw must get some respect for mentioning (~column 968) the rotation velocity of the Earth's surface (corrected for latitude even!), the rotation of the Earth around the Sun and the solar system around the centre of the Milky Way. He did stop short of mentioning our velocity relative to the microwave background though!

I did like the quote: "This could mean, by the turn of the century that all legal documents, (including birth or death certificates) will have as a matter of course UTC time with tenths of a second accuracy printed on them". The doctors had better get their atomic clock synchronised stop watches ready then!

Posted in astro blog by Stuart on Sunday 08th Aug 2004 (01:35 UTC) | Permalink

Planet Pirates

Radio 4 just broadcast a programme called Planet Pirates that was presented by Clive Anderson. It was about those people that set up businesses on the Earth, selling off bits of the Universe. People such as Dennis Hope, believe that they can do this because they claim the 1967 UN Outer Space Treaty only covers nation states. Dennis Hope has even set up the unrecognised Lunar Embassy in order to sell off bits of the solar system; Mercury is being put up for sale soon.

All this is pretty much like buying stars from really dodgy star naming companies and is equally invalid. Another person interviewed on the programme was Virgiliu Pop who isn't a big fan of Dennis Hope. Virgiliu is writing a thesis on space law and in 2001 made a claim for the Sun, with the Archimedes Institute to point out how ridiculus this all is.

All of these claims are currently pointless as in 2000 I made a claim, with the Archimedes Insitute, for the "whole of the observable Universe, except for the parts previously claimed, including all space, time, and any other dimensions that may be shown to exist". I dedicated my claim to be used by all sentient life for peaceful, scientific use. Strangely they never accepted my claim.

Perhaps we need a revolution to overthrow the sham Lunar government.

Posted in astro blog by Stuart on Saturday 07th Aug 2004 (10:38 UTC) | Permalink

Thunderbirds aren't go

On Saturday night I went to see the new Thunderbirds movie with Megan and Peter despite it being described as "Spy Kids minus fun" in one review. It certainly wasn't the best film of the year although visually it was very good; they did a good job creating the vehicles and sets. From a bad physics/astronomy point of view, they do get let off on some points as they were sticking to the original series. However there are a few problems which are just down to a lack of thought.

At one point we have Jeff Tracey and his sons stuck on the space station Thunderbird 5. They seem to walk on the 'floor' when they arrive but after they get attacked (sorry to spoil it but it is a bit predictable) and loose power, they become weightless. Perhaps the simulated 1G is due to the station spinning - we see an outside shot a few times - but surely the station would keep spinning when the power fails. As an aside, a spinning station makes it very difficult to dock on the outer wheel which we see Thunderbird 3 doing earlier on. This reminded me of Armageddon when the two shuttles dock with a spinning MIR.

Without control systems, the station starts falling towards Earth and is finally saved when power is restored seconds before re-entry into the atmosphere. This would put it about 100 kilometres above the surface, but we then hear (a couple of seconds later), that the station has been moved back to geostationary orbit. Now, as geostationary orbit is about 35,000 km (22,000 miles) above sea level, that means they have gone about 22,000 miles in two seconds! Hmmmm.

The Thunderbirds website also makes a blunder in the specifications for Thunderbird 3 (requires flash). On the website they claim that its maximum velocity is 5,000 mph but this is only a fifth of the speed required to reach escape velocity and, strangely, one third of the speed of Thunderbird 1.

Posted in astro blog by Stuart on Monday 02nd Aug 2004 (00:17 UTC) | Permalink
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