October 2009 Sky Notes by James Abbott
Jupiter’s reign of the evening skies starts to come to an end this month. By the end of October, Jupiter will be setting at around 2300 GMT. But as Jupiter exits the scene, so Mars makes its entrance. The Red Planet is well clear of the Eastern horizon by midnight at the end of the month.
Mars will be at its best early in 2010, shining down from high amongst the winter stars. It becomes favourably placed every second year because its orbit takes it around the Sun in just under 2 years. The Earth, orbiting closer to the Sun and faster, catches up with Mars every 2 years, leading to a rapid brightening and then fading as the two planets pass. At the end of October, Mars will still be about 110 million miles from the Earth, but by the end of January the gap will have closed to about 60 million miles. The 2010 opposition will not be as good as those of earlier in this decade, but the disc will be large enough to show detail in amateur telescopes.
The Moon is Full on the 4th. The waxing Moon passes fairly close to Jupiter in the South Western evening sky on the 26th and 27th. But a much closer pass of a planet can be seen from after midnight on the 11th/12th when the waning Moon passes just a degree (2 moonwidths) from Mars.
The clocks go back to GMT on Sunday 25th October this year when Sunset will be before 5pm and twilights ends as soon as 6.30pm. In the East, the winter constellations of Gemini and Orion will have risen by about 2200 GMT in the last week of the month. The bright red giant star Betelguese sits at Orion’s left shoulder and is clearly an orange colour even to the unaided eye. Betelguese is about 400 light years from Earth which is relatively close when compared to other giant stars. It is close enough and large enough that the biggest telescopes can resolve it as disc. Recent research has shown that unlike our stable Sun, Betelguese is pulsating and is generating huge plumes of gas spilling out into space. We dont know enough about stellar evolution to accurately predict when Betelguese will explode as a supernova, which is its expected fate. However, we can work out roughly how bright it is likely to be when this happens – probably as bright as the Full Moon !
