Friday, June 30
Image Credit: ESA
Venus Express continues to orbit Venus, now in its final orbit. It has returned images which confirm the expected 'double vortex' at the south polar region. More details in this Universe Today article.
NASA are still working on a solution for the Hubble Space Telescope ACS instrument. The camera failed on 19th June and although engineers believe they now know how to fix it they won't complete the repairs until 3rd July at the earliest. The repair plans have to be considered by a NASA review panel before being implemented.
Cassini has now completed half of its planned mission at Saturn. More details in this story.
Finally, if you're interested in Jupiter's Red Spot Jr we mentioned a few days ago on CAS News you can keep up to date with regular pictures at www.redspotjr.com.
Tuesday, June 27
This bring the total number of known moons around Saturn to 56. More details on the Planetary Society Blog here and here. A full listing of Saturn's moons is here.
Monday, June 26
As a reminder of the type of images we are used to getting from the Hubble ACS, the image below was released in late April and shows Jupiter's famous Great Red Spot, along with a more recently formed Red Spot Jr.
Red Sport Jr, officially known as Oval BA formed from three white storms in Jupiter's atmosphere which merged in 1998. In late 2005 this white spot started to change colour, eventually turning the same colour as the 'Great Red Spot' in February 2006.
Image Credit: NASA/HST
Saturday, June 24
Friday, June 23
Similar mutual event sequences take place for other planets. The interval is every 6 years for the Jovian system (Here are a couple of examples from my image archive taken in 2002 here and here) The next series is due around 2009
Much rarer are mutual events in the Uranian system which only happen every 42 years. The season however starts now and will continue for the next few years. Go to the Armagh Observatory website for more information.
If you thought the recent pictures from Cassini of Saturn's moons were impressive, check out some of the movies of mocing moons on the CICLOPS website here.
CICLOPS is the Cassini Imaging Central Laboratory for OPerationS, and is where many of the excellent Cassini images are posted.
Thursday, June 22
Yet another amazing Cassini image was released yesterday. Taken back in February this image shows Enceladus passing in front of the giant moon Titan. What is clear from the image is the difference in colour between the two objects. Titan has a brown atmosphere and Enceladus is almost white, its surface reflecting 99% of the light falling on it.
The difference in size is also apparent, especially given that Enceladus was 1.1 million km closer to Cassini than Titan was when the image was taken.
These moon transit images are becoming pretty routine from Cassini now, but to my mind this is the best yet. Perhaps next time they'll get Saturn's rings in there as well ?
Wednesday, June 21
Image Credit: NASA/ESA/HST
On the subject of Pluto and following my post the other day on what is a planet, it's worth noting that the BBC Horizon programme tomorrow night (BBC2 : 2100hrs) is covering the debate over what the definition of planet is. The programme is provocatively titled "Bye Bye Pluto". Thanks to Stuart for pointing that out for us.
This recently released Cassini image shows yet another spectacular view from the space probe as it orbits Saturn. In this picture Saturn's moons Dione and Rhea pass in the night. As seen from Cassini Dione crosses the face of Rhea. Dione is the smaller of the two satellites with a diameter of around 700 miles it is about 2/3 the size of Rhea. The image was taken from a distance of about 1.7 million miles from Dione (about 1.9 million miles from Rhea).
Monday, June 19
A traditional planet, like Earth or Neptune, would be one type of planemo. Others would be; planet sized objects which don't orbit a star, objects which are relatively large but orbit other planets (Jupiter's Galilean moons or Titan for example), or large bodies which share an orbit such as asteroids like Ceres.
We now know planetary systems around stars are quite common. They form from the disk of gas and dust orbiting a star once it has condensed out of a vast cloud of interstellar gas and dust. Recent evidence suggests that planetary systems could form around planemos (interstellar planets) as well as stars or brown dwarfs. This suggests that planetary mass objects could condense from interstellar clouds, independently of stars, and in turn have their own planetary systems orbiting them. If that's that case would those orbiting bodies be called 'planets'?
That's an added dimension to the already complex "what is the definition of a planet ?" debate. It's a topic worthy of a talk / debate at a future CAS meeting. It is anticipated that the International Astronomical Union will provide an update definition of planets at their September 2006 meeting.
 A brown dwarf is defined as a object which is massive enough that deuterium burning nuclear reactions start inside when it forms. These reactions are short lived, and the brown dwarf is not massive enough to generate enough heat to start hydrogen burning reaction, and become a fully fledged star. Brown dwarfs are 'failed stars'. Currently the lower mass limit for brown dwarfs is thought to be about 13 Jupiter masses.
Sunday, June 18
We talked about the tiger stripes, and the active geysers, and even the possibility that the moon may have tipped over. Here are a couple of new views of the moon which emphasise the unusual features found there.
Image Credit: NASA
The first image, from Cassini, shows Enceladus against the dark side of Saturn. The plumes of water ice erupting from the southern polar regions are clearly visible in this enhanced image. The photograph was taken at a distance of around 1.3 million miles from the icy moon.
For a different perspective on Enceladus have a look at this picture by space artist Michael Carroll, showing what the moons surface might look like close up.
Sunday, June 11
If you haven't already seen this over at Stuart's Cumbrian Sky, then check out this Star Atlas from Astronomy magazine available in newsagents for Â£5.
Stuart's review gives you all the details. I bought a copy yesterday as well, and can confirm it is worth a fiver. Couple that with a pair of Â£15 binoculars (next time they are available from Lidl) and you've got yourself a complete beginners astronomy kit for Â£20. Not bad.
Friday, June 9
This latest picture released from the Hubble Space Telescope is excellent for showing some of the features of galaxies we don't normally see.
The galaxy is seen exactly edge on, so what is immediately apparent is the dark lane of dust and gas which runs along the galactic plane. The detail in this image is incredible, I've included a couple of close ups below to show the detail. You can however go to the HubbleSite to explore a zoomable version.
It's worth bearing in mind that although the dust lane appears dark because it is blocking and scattering the light of stars in it, the density of these clouds is actually very low. So low infact that on Earth we would call it a vacuum! It's only the vast distances involved that give the effect we see.
You can even see branches or tendrils of dust extending above and below the galactic plane. NGC 5866 is a S0 class of galaxy (according to the Hubble classification of galaxies), which means that it is a spiral galaxy without the 'spiral', more a flat disk with a bulge in the middle. A typical flying saucer shape. If you could see it from 'above' one of the poles you wouldn't see the distinctive spiral arms we see when we look at M31 Andromeda Galaxy or M51 Whirlpool Galaxy.
The other feature worth nothing on this image are the globular clusters of stars which are distributed around the galaxy's halo rather than in the disk. These are clusters of perhaps a million or so stars which formed together. They can be seen to be quite distinct background galaxies which can be see through the halo.
By studying the distribution of these globular clusters in our own milky way galaxy, Harlow Shapley was able to first determine the rough size and shape of our galaxy.
Thursday, June 8
Well the book is now available as a daily blog at http://www.astrowhatsup.com/. There are ideas for what to look at each night of the year, as well as interesting facts / space history and photos.
A lot of work has gone into preparing this book/blog and it's well worth checking out, and there's even an option to integrate it with our own website, which I'll be looking at over the next week or so.
Tuesday, June 6
We've seen quite a bit of interest over the last six months or so about Saturn's icy moon Enceladus. Cassini has sent back some amazing image of the moon which is the most reflective body in the solar system, reflecting 99% of the light which falls on it. We've learned that the moon is active, with eruptions of water vapour seen from the 'tiger stripe' features near the moon's south pole.
What has puzzled astronomers is why the hot region is at the pole, rather than near the equator. A new model now being considered speculates that the moon may have 'tipped over' as a result of the hot spot.
The theory is that as the hot spot developed that region of the moon expanded with the internal heat, and therefore became less dense. Spinning bodies have a tendency to be more stable if more of their mass is close to the equator. Hence the cross-section with least mass will tend to align with the poles. This is a property of spinning objects, not related to gravity.
If this is the case the sometime after developing the hot spots, Enceladus tipped on its side to balance it's spin. Scientists still haven't worked out the mechanism for heating within Enceladus, although it may be some form of tidal heating.
Thursday, June 1
There was a good turn out for the meeting (despite half term holidays and an England football match on TV) and it was great to see Stuart and Stella from the Eddington Astronomical Society (Kendal). After a quick news round up it was time for the first of two presentations. Dennis gave a presentation on his recent project to build a simple refractor, done as part of a GCSE Astronomy course. Despite some problems with the presentation technology, the talk was fascinating, covering a brief history of telescope and eyepiece design. Everyone trying the telescope was impressed with the clarity of the handmade instrument. There were plenty of questions and discussion after the talk, and definite enthusiasm for a future 'practical workshop' to allow people to try there hand at making their own instruments.
After a short break Chris gave a round up of methods for detecting Extrasolar planets, and an update on recent discoveries. There are now in the region of 180 known extrasolar planets, including some that amateur astronomers have been involved in discovering and observing.
Unfortunately our planned AGM didn't come off, we'll have to arrange that for a different date.