Planetary triangles

On the morning of 9th February 2018 the Moon, Mars and Jupiter form a nice right angled triangle in the morning twilight sky. The picture shows the positions of the planets at 6:30am GMT on the 9th February 2018:

In the opposite direction, Saturn forms another right angle triangle with the Moon and Mars.

Clear skies.

Oxford Stargazing 2018

The society will have a stand at this event tomorrow (27/1), do come and see us. If the weather is clear you’ll be able to look through telescopes at our nearest star and other objects. It takes place at the Denys Wilkinson Building, Department of Physics, University of Oxford, Keble Road, Oxford OX1 3RH between 1pm and 9pm. See here for more details.


Close conjunction of Jupiter and Mars on 7th January 2018

In the early hours of January 7th 2018, Mar and Jupiter will appear to be very close in the sky in the constellation of Libra. At 05:00UT they will be 13 arcseconds apart, but only 11 degrees above the horizon. Should make for an interesting view through binoculars or a small telescope. Astronomical dark ends at 06:09UT (Sunrise is 08:11UT) that morning so you could wait till a bit later when they will be bit higher in the sky. See the picture below for where to look.

Clear skies


Quadrantids on the 3rd/4th January

This year the Quadrantids meteor show peaks at 02:00UT on the 4th January 2018. Unfortunately a full moon will drown out all but the brightest meteors. See the picture below of where to find the radiant and then look to the west of it (i.e. towards the North) to minimise the impact of the full moon.

This shows the position of the radiant for the 4th January 2018, 02:00UT from Abingdon.

Clear skies.

October’s Talk

The BepiColombo mission to Mercury is a joint ESA/JAXA (Japan Aerospace Exploration Agency). The craft is named in honour of Giuseppe (Bepi) Colombo (1920-1984), an Italian scientist who first used the gravity assist (‘slingshot’) method of sending spacecraft across the solar system by bringing them close to other planets, thereby using their gravity to increase speed.

Mercury is odd in that it has a very dense large core with a total size not much different from that of Earth’s. This almost certainly came about when Mercury hit something massive while the solar system was still being formed. (What Prof Rothery calls ‘planetary embryo collisions’.) But where was Mercury’s embryo when it got bashed? He is intrigued why there is so much sulphur (2-5%) on the surface but the collision theory would also explain that away in that Mercury probably formed further out in the cooler parts of the solar system and was therefore mostly the hit and run impactor itself, and most of the lighter stuff from the two bodies was dumped into space, leaving the dense core.

Mercury’s surface has a rather dark grey, flat albedo, even lower than that of the Moon. There are areas of slight stepping, indicating tectonic thrusting as the surface cooled.

The Messenger spacecraft was busy orbiting and mapping Mercury from around 2011-15. Joint UK/Italian scientists are using the data to create 15 geological maps in total. As regards BepiColombo, the UK contribution is an x-ray spectrometer (see below) which sees the fluorescence on the surface. The Sun shines x-rays onto Mercury and the resulting fluorescence and reflected x-ray photons tells us what elements there are and the abundance thereof. The more active the Sun is the more fluorescence there is so you get more information.

Unfortunately the Messenger data did not cover the south pole. The north pole had much better coverage. The elements detected were silicon, sulphur, iron, magnesium, potassium, calcium, among others.

BepiColombo consists of two craft which will not be able to separate until they arrive. MMO (Mercury Magnetospheric Orbiter) is Japan’s half, MPO (Mercury Planetary Orbiter) is the ESA half. The UK and Finland have created MIXS (Mercury X-ray Imaging Spectrometer mentioned above).

Launch may go ahead next year. There will be two Venus flybys and five Mercury flybys to get it into orbit, and this is going to take 8-9 years. Once in position, MMO will fly very close in ellipses, so that its orbits will take 2 to 3 hours (400-1500km) and MPO will have a far more elliptical orbit, with its closest being 400km also.

It was amusing to hear Prof Rothery’s defence of the cost of the mission in the face of nasty comments from people on public media. The mission is likely to cost a total of 3.3 billion euros. Not that much when you consider about 8 billion dollars is likely to be spent on lipstick in the next year….

Clear Skies