Today (9 October 2009) two unmanned NASA spacecraft will impact the Cabeus crater in the lunar South Pole, in the final stage of the LCROSS mission (Lunar Crater Observation and Sensing Satellite).
The first spacecraft, the 2200kg Centaur rocket stage, will hit the Moon at about 4800 km/h or twice the speed of a bullet, throwing up debris plumes to an expected height of 10km above the lunar surface, visible from Earth-based telescopes 10-12″ and larger.
The smaller ‘shepherding spacecraft’ will follow, descending through the debris plume to impact 4 minutes later. As it travels through the plume, onboard spectrometers will monitor the chemical components of the debris, looking for water, hydroxyl compunds, salts, clays and organic molecules, and relay this information back to Earth before impact.
Projected first impact is currently 12:31 BST.
You can watch the impact live online on NASA TV.
At 2.00 am BST (1.00 am GMT) on Sunday 25 October 2009 UK clocks will move back by an hour as civil time moves from British
Summer Time (BST) to Coordinated Universal Time (almost identical to
Greenwich Mean Time).
Or, to put it more practically, UK residents can all look forward to their annual extra hour in bed on the last Sunday in October.
The Ninth European Parliament and Council Directive on Summer Time
Arrangements states that summer (or daylight saving) time will be kept
between the last Sunday in March to the last Sunday in October, and the
changes take place at 01.00 GMT.
Find out more about daylight saving time in the Royal Observatory’s fact file.
Two planetary conjunctions involving Saturn are visible from the UK this month. However, they will be very low in the eastern pre-dawn sky and there won’t be much time to observe them before it gets too light to see
them easily with the naked eye.
In the early morning of 8 October Mercury will be 0.3º from Saturn in the sky, and at 11.00 in the morning of 13 October Venus will be 0.5º from Saturn. These two events effectively form a triple conjunction or what some are describing as a ‘three-way planetary dance’, visible between 8-16 October. On 16 October they will be joined in the pre-dawn sky by the waning Moon.
Astrologers seem particularly excited about the multiple conjunction (though ideas as to its significance vary considerably) and some astrology blogs actually have more detail about the exact timings of the events than astronomy sites.
Then on 21-22 October the annual Orionids meteor shower reaches its maximum, with a likely average of 25 meteors per hour at its peak. However, recent years have produced much stronger showers so the rate could be even higher. The Orionids are fast meteors with fine trains, associated with Halley’s Comet. Conditions for observing should be favourable and moonlight will not be a problem.
NASA’s infra-red Spitzer Space Telescope has identified a vast, diffuse and all-but invisible new ring around Saturn, tilted at 27º from the main ring plane. The discovery was announced on 6 October 2009.
The huge disk of material starts about 6 million km away from the planet and extends at least another 12 million km outward, with a vertical thickness of about 2.5 million km. However, despite its size the ring is very tenuous, composed of highly diffuse ice and dust particles. This material is thought to have come from Phoebe, one of Saturn’s most distant moons, as a result of small impacts on the moon’s surface. This material may also solve the long-standing puzzle of the two-tone moon Iapetus, light on one side and dark on the other. It’s thought that the dark face is caused by dust from the ring moving inwards towards Saturn and impacting the moon on one side.
Image: Artist’s impression of new giant ring around Saturn (infrared view) (NASA)
View beautiful images of Saturn’s other rings from the Cassini-Huygens mission, recently on display at the Royal Observatory, Greenwich.