Monday, 7 July 2008

The Sky at Night - July 2008

This month's programme was hosted by Chris Lintott from the Mars Phoenix mission control headed by Professor Peter Smith.

The Phoenix lander was sent to the northern polar region of Mars and landed in Green Valley of Vastitas Borealis on May 25th. The main mission was to find water ice beneath the Martian soil. On landing, the retrorockets of the lander displaced the top soil to reveal ice beneath.

The landing site is similar to the areas of permafrost at Earth's northern latitudes as the land looks like a patchwork of thermally contracted polygons. After initial tests, the soil was found to be slightly alkaline and much like Earth's soil. In fact, Mars could support Earth vegetation.

The main tool on Phoenix is a digging tool for taking soil samples. These samples can then be viewed through an on-board microscope. There is also an oven for baking samples and boiling off gases and water vapour. After some teething problems the oven is now working.

There is also a camera with mono and stereo full-colour imaging. In addition there is a simple device for measuring Martian winds. The Martian atmosphere is only 1% of Earth's atmospheric pressure so a very sensitive pendulum was installed in place of an electronic anemometer. By photographing the movement of the pendulum, scientists can determine wind direction and relative strength.

Saturday, 7 June 2008

The Sky at Night - June 2008

This month's programme had a brief update on the Mars Phoenix landing. The programme then went on to discuss returns to Saturn and Jupiter to look for signs of life amongst their satellites. Professor John Zarnecki of The Open University championed a return to Titan to follow up the findings of Huygens probe and look for the building blocks of life.

Professor Michele Dougherty of Imperial College argued a return to Jupiter to look for life on the Galilean satellites. In particular, a visit to Europa that is believe to have liquid oceans under its ice surface.

The Sky at Night - The Battle of the Giants

Monday, 5 May 2008

The Sky at Night - May 2008

The May edition of The Sky at Night was titled "You Just Don't Know" and was a round table discussion about the limits of human knowledge. Around the table sat Sir Patrick Moore as "Devil's Advocate" due to it being the 666th edition of the programme, Dr Chris Lintott, Dr Kate Land, and Professor Gerry Gilmore.

The assembled brain's trust of astronomers discussed the known universe and attempted to guess what was left to be understood. The viewer was reminded of the current theory of the Big Bang Model for the universe. Dark matter and dark energy were postulated as fitting current known models for the expansion of the universe.

It was said that the visible universe accounted for but a fraction of the mass of the universe and that exotic materials probably accounted for the rest. The guests then talked about how privileged astronomers were to view the universe at this time, as the past and future will not be conducive of observations.

In conclusion the guests said that the expansion of the universe was accelerating and the future will be a dark and lonely place as space, time and matter expand beyond the capabilities of visible observation.

The Sky at Night - We Just Don't Know

Tuesday, 29 April 2008

Choosing a telescope or binoculars

Amateur astronomy has made great technological advances in the last few years that amateur astronomy can claim to be the only science that can assist the professionals. Just try getting a synchrotron into your bedroom for some particle physics experiments!

Don't go rushing out to buy a telescope, especially not those little plastic 2-inch refractors and 4-inch reflectors promising you 500X magnification. They are usually of very poor build quality and though cheap will disappoint you and turn you off astronomy for life.

Better still, buy yourself a good pair of binoculars. I recommend a pair of 10X50. The 10 refers to the magnification and the 50 to the diameter of the object lens in millimetres. And, if you decide that you don't like astronomy you can use them to keep your eye on the neighbours!

If you do want to buy a telescope then take a look at the scopes from companies such as Meade, Orion or Celestron. They are well-made and will give a lifetime of enjoyment. There is a thriving second-hand market on eBay if cost is at a premium and you don't mind not having the latest of everything, unlike me.

Read these articles on choosing a telescope:

BBC - Patrick Moore's Guide to Buying a Telescope

Astronomy Magazine - Buying a telescope

Wednesday, 16 January 2008

Messenger from Mercury

NASA's MESSENGER probe has sent back its first image of Mercury. It shows a planet pocked with craters, much like the Moon.

Another similarity with the Moon is the lack of atmosphere. There is a tenuous atmosphere replenished from places like the solar wind but nothing like Venus, the next planet closest to the Sun after Mercury.

The planet gives us a foretaste as to the fate of the Earth when the Sun swells to become a red giant. Mercury's surface temperature ranges between 90 and 700K.

The MESSENGER probe will settle into an orbit around Mercury by 2011, after two more fly-bys. The probe will then examine the chemical composition of the planet and its magnetosphere.

Thursday, 3 January 2008

Mars rovers still working

Four years after starting their 90 day missions on Mars, rovers Spirit and Opportunity are still going strong. Together they have ranged over 10 miles and have taken over 200,000 images of the Martian surface.

They have done a lot of good science, including supporting theories about water having once been on the surface Mars. With the onset of the Martian winter the rovers are now parked and awaiting spring before continuing their record breaking activities. Let's wish them a long life so they may welcome ESA's ExoMars rover in 2014.

Wednesday, 2 January 2008

Cassiopeia, C14 and Perseus

[click to enlarge]

20:24:10 UTC 1st December 2004
Canon EOS 300D with 18mm lens at F3.5
120 sec exposure at ISO 1600

It is very enjoyable taking wide-field images of whole constellations. This image is of two constellations, Cassiopeia and Perseus. It is not hard to take this kind of image and doesn't require much equipment. A Canon EOS 300D SLR camera with the supplied 18-55mm zoom lens was used.

The camera had the benefit of sitting on a motorized equatorial mount, which allowed the camera to follow the stars as the Earth rotated on its axis. This permitted a longer exposure to bring out more of the Milky Way that runs through these constellations.

A good image can still be taken without a motorized mount but shorter exposures are needed so that stars don't trail. The image will have fewer stars on it but it will still be possible to make out all the main stars in any particular constellation.

Between the two constellations is the double cluster C14, which is part of Patrick Moore's Caldwell Catalogue.

Not much processing is needed with wide-field images like this. All that was done to this image was the adding of lines to connect up the stars in each constellation.