If we face north in the early evening we see Spica low to the far right or east. Just to the right we have Regulus and just to the left Pollux and Castor. Above them is Procyon and then Sirius, the brightest star in the sky. Further to the left or west we reach Rigel, Betelgeuse and the other stars of Orion.
The stars of the constellation of Orion. Image Nick Lomb
In the early evening this zodiac constellation is visible low down in the eastern sky. To find its brightest star, Spica, first look for a distorted rectangle of four stars that form the constellation of Corvus the Crow. Two of the stars point to Spica directly below.
The constellation of Virgo with its brightest star Spica indicated. Courtesy Stellarium
The Earth goes around the Sun once a year. The Sun itself is moving as it circles the centre of our galaxy roughly once every 240 million years. This may seem a long time, but during its life the Sun has completed around 20 circuits of the galactic centre. Feeling dizzy?
An artist’s concept of the Milky Way based on recent information. Courtesy NASA
Graph indicating sunrise in Sydney throughout the year. It is calculated for 2014 but there is little change from year to year except for the slight shift of the starting and ending dates for daylight saving. Diagram Nick Lomb
If you rise early whether for work, school, gym, a run or walking the dog you are probably sick of the dark mornings that crept up on us very quickly in recent weeks. In that case, help is at hand for this coming Sunday (6 April 2014) is the first Sunday in April and hence daylight saving finishes early that morning.
As can be seen on the above graph the morning before, that is, Saturday morning, is the latest sunrise for the year with the Sun rising at 7:10 am. In the depths of winter at the end of June and the beginning of July the latest sunset is only 7:01 am. So the mornings may well become cooler as the year progresses towards winter, but it is not going to become darker.
If you think that 7:10 am is late for sunrise, spare a thought for the 8000 or so people of the small town of Wentworth in the south-west of NSW. The town is approximately 9° to the west of Sydney and, as each degree of longitude represents four minutes of time, sunrise occurs about 36 minutes later than in Sydney. There the latest sunrise for the year is on Saturday at 7:47 am.
Of course, some people may be disappointed by the earlier sunrise. If you are trying to sleep in for instance you may not appreciate being woken up by light spilling through edges and gaps in blinds and curtains. Also others may have enjoyed the opportunity to see the planet Venus and other objects in the dark morning sky such as passes by the International Space Station.
The above diagram is a useful one as we can see how daylight saving acts to reduce the spread of sunrise times throughout the year. Without daylight saving in early December sunrise would be as early as 4:37 am, which could be a serious difficulty for those trying to sleep at that time.
An interesting, just released, American study suggests that at the start of daylight saving in spring there is a spike of 25% in people experiencing heart attacks, presumably due to losing one hour’s sleep. Conversely, at the end of daylight saving in autumn when the clocks are moved backwards by an hour there is a 21% decrease in heart attacks. The study is based on data from only one American state and the authors suggest that it would be worthwhile comparing the results of their study with data from a state that does not have daylight saving. Maybe a comparison could be done in Australia between hospitals in Sydney and in Perth where there is no daylight saving?
If you like you can stay up till 3 am to change your clocks on Sunday morning. For most people though it is easier and more sensible to do so before going to bed on Saturday evening. And, fortunately, these days many devices like mobile phones, tablets and computers, tend to change automatically without the need for human intervention. However you do it, enjoy the extra hour of sleep on Sunday morning and the lighter mornings from then on.
Scientists have suspected that there is water ice in permanently shadowed craters near the Moon’s poles after finding H and OH ions in some of them. However, Alice Springs Observatory has just announced that these ions are from the compound CH3CH2OH, better known as ethanol. Drunkenness maybe a problem on future lunar landings!
The south pole of the Moon imaged by the Lunar Reconnaissance Spacecraft. Courtesy NASA/GSFC/Arizona State University
If we extend a line through the main axis of the Southern Cross, Achernar is the first bright star that we reach. It is the brightest star in the long and winding constellation of Eridanus the River. A very hot star, Achernar has a fast spin that has flattened it into a football-like shape. At a distance of 140 light years from us, the star has six to eight times the mass of our Sun.
Achernar and a few of its neighbouring stars. Photo Nick Lomb
It is hard to believe today with the MESSENGER spacecraft circling Mercury and carrying out detailed mapping that until 40 years ago we had little idea of what the planet looked like. On this day in 1974 NASA’s Mariner 10 spacecraft became the first to fly past the planet and to provide views of its cratered surface.
A Mariner 10 mosaic of Mercury taken from 200,000 km away. Courtesy NASA/JPL
To help you learn about the southern night sky, Sydney Observatory provides an audio guide/podcast, transcript of that audio, and a sky map or chart each month. This month’s guide is presented by Dr Nick Lomb, Sydney Observatory’s Curator of Astronomy.
A MONTH OF ECLIPSES!
April 2014 is a month of eclipses – with both a total eclipse of the Moon and also a partial eclipse of the Sun. Listen to the podcast or read the transcript below to find out when and where to look to experience these astronomical events.
In this month’s podcast, Nick also tells us about stars that look from Earth like single stars but are actually multiple stars. For example, the star we think of as Castor – one of the two most prominent stars, Castor and Pollux, in the constellation of Gemini the Twins – is actually six stars!
Other constellations Nick tells us about this month are Orion, Leo the Lion, and Crux – also known as the Southern Cross.
For this and much more, listen to the audio, or read the transcript below for more details.
HEAR THE AUDIO
You can subscribe with iTunes or upload the (28 mins 38 secs) audio to your iPod or mp3 player, or listen to it on your computer.
SEE THE SKY CHART
We provide an embedded sky map (below) and an April 2014 night sky chart (PDF) which shows the stars, constellations and planets visible in the night sky from anywhere in Australia. To view PDF star charts you will need to download and install Adobe Acrobat Reader if it’s not on your computer already.
BUY THE BOOK
Our annual book, ‘The 2014 Australasian sky guide’, by Dr Nick Lomb has more information and star maps for months from December 2013 until December 2014 inclusive, plus information about the Sun, twilight, the Moon and tides, and a host of other fascinating astronomical information. You can purchase it ($16.95) at Sydney Observatory and Powerhouse Museum shops or other good bookshops, or online through Powerhouse Publishing (additional packing/postage costs apply).
READ THE TRANSCRIPT (after the jump)
The elusive planet Mercury can be seen low in the east before dawn. Tomorrow morning a thin crescent Moon is to the left or north of the planet. Recently the International Astronomical Union named ten newly mapped craters on the surface of the planet. These include ones named after John Lennon and after the Italian tenor Enrico Caruso.
Mercury and the Moon on the morning of 29 March 2014. Chart Nick Lomb
This is the brightest star in the constellation of Carina the Keel and the second brightest star in the sky after Sirius. After dark it is high in the south. One way of finding it is to extend a line upwards through the left-most and top-most stars of the Southern Cross.
Finding Canopus using the stars of the Southern Cross. Original star chart courtesy 2014 Australasian Sky Guide