Sky Notes for July 2014 with James Abbott

Mars and Saturn remain fairly well placed for most of July in the late evening skies, but rather low in the South West. By months end Mars is setting at 11pm. The 2 planets close on each other along our line of sight so that by the end of July they are about 14 degrees apart and almost exactly the same brightness. The other bright planets are all close to the Sun in the sky and so are difficult to see.

We are all familiar with the bright planets which along with the Sun form the main bodies of our Solar System. But in recent decades more powerful telescopes, search programmes and improved techniques have revealed that our system, and probably most other star systems in our galaxy, also contain a veritable menagerie of smaller objects in huge numbers. The main groups are asteroids, comets, dwarf planets, and larger icy bodies, as well as dust and debris belts. Then there are the large families of moons around the largest 4 planets.

The old text book strict dividing lines between these families have broken down to an extent. Some objects classed as asteroids can display cometary activity. Some of the moons of the planets are captured asteroids. Ganymede is classed as a moon, but is larger than Mercury. So is Titan – and it has a dense atmosphere and planetary weather. Would Enceladus be classed as a comet if it were in a free orbit around the Sun ?

http://www.bbc.co.uk/science/space/solarsystem/moons/enceladus_%28moon%29

Perhaps we need a new classification that takes more account of factors including composition and size.

Hubble Space Telescope images of Ceres helped scientists determine it was unique from other objects in the asteroid belt.

Hubble Space Telescope images of Ceres helped scientists determine it was unique from other objects in the asteroid belt.

Throughout July, two of the largest such objects in the Solar System, Ceres and Vesta, will be very close together in the sky. On July 5th they are about a sixth of one degree apart – for comparison that is about a third the width of the Full Moon. This unusually close approach will be visible in binoculars, as will the movement of the two bodies relative to each other as the month progresses. The area to look at is in Virgo, just above Mars and the best time is after 11pm BST in the first half of the month. On July 5th, Ceres is mag +7.6, Vesta is mag +6..3 and the pair are 1.5 degrees South West of zeta Virginis. If you have zeta in your binocular field of view, you will have Ceres and Vesta too. Ceres is currently classed as a dwarf planet and is about 1,000 km in diameter.

Vesta is about half that diameter and is classed as an asteroid.

Full Moon this month is on the 12th, meaning that the second half of the month will be best for dark skies, helped by the end of the all night summer twilight on July 23rd. By the end of the month there is a 2 hour window of dark skies from mid-Essex.  Late July is also a good time of year to watch for meteors. There will be several known showers active, each of them producing modest numbers of meteors, but together increasing the chance of seeing some activity.

The first quarter Moon will be just 2 degrees from Mars on the evening of the 5th July and 3 degrees from Saturn on the 7th, both approaches best seen at about 11pm.

The Milky Way will be ideally placed to be seen in late July from areas away from streetlights. At midnight the subtle glow of billions of stars at great distance from us can be traced out running from overhead in Cygnus down towards the South.

 

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Posted on 6 July, 2014, in Astronomy News, astrophotography, Observing News, Popular Science, Society News, Stargazing. Bookmark the permalink. Comments Off on Sky Notes for July 2014 with James Abbott.

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