Megan's Blog

What's in the southern sky - August 2009

For the last few months, I've been writing a short contribution to the Scouts WA newsletter on what's in the sky for the month ahead. Here's the piece for August. Times are correct for Perth.

August sees the days continue to lengthen with the Sun rising at 6.35am and setting by 5.59pm by the end of the month. The Moon is full on August 6th and New Moon this month is on the 20th. Jupiter is visible all night and will be the brightest object, after the Moon. Rising in the East in the early evening, it passes very high overhead from Perth and will be hard to miss. If you are up early on August 7th, you will be able to see Jupiter just three degrees from the almost full Moon.

Jupiter was hit by an object during July, leaving a visible scar on its thick atmosphere. The impact was discovered by Anthony Wesley, an amateur astronomer in New South Wales, who noticed a new black mark on the planet through his backyard telescope. News of the event spread quickly around the world and several large telescopes were used to observe the planet over the following days. The newly upgraded Hubble Space Telescope has also imaged the impact site using the newly installed Wide Field Camera 3 which is working beautifully.

Saturn is still visible in the western sky during early evening twilight, although it is setting earlier each night, setting at 7pm by the end of the month. The elusive planet Mercury will also be visible in the early evening sky towards the end of the month. The best time to look will be a few days either side of the 16th (when Saturn and Mercury are close together in the West after sunset: Saturn will be the brighter of the two), and the 22nd (when Mercury will be close to a very thin crescent Moon). Have a look with binoculars if you can, BUT WAIT UNTIL THE SUN HAS SET BEFORE USING THEM! The Sun will blind you easily, so never look at the Sun through any kind of optical aid.

Mars will be visible in the early morning sky, halfway between Venus and the Seven Sisters (also known as the Pleiades cluster). Sadly, it will look no bigger than usual, despite the email hoax going around. You may recently have received an email saying that Mars is going to appear as big as the full moon in August. Don't believe it! This rumour has been going around since 2003 and is sadly just not true. In August 2003, Mars was at its closest to Earth for several thousand years and, while it was brighter than normal in the sky, it was still a very long way from us (more than 55 million kilometers) so a reasonable telescope was needed to see any details on the surface. All the planets travel in circles around the Sun. Mars is further from the Sun than the Earth is, so every few years we overtake it as we go around the Sun, and this is when the two planets are closest to each other. This will happen next on 29 January 2010 when we will still be almost 100 million kilometers from Mars. If you get an email with a powerpoint presentation about this, then please delete it!