The Night Sky in February 2007
Sunrise and Sunset Times for the UK
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Edinburgh Sunrise Sunset |
Manchester Sunrise Sunset |
London Sunrise Sunset | ||||
| Feb 01 | 08:09 | 16:44 | 07:55 | 16:50 | 07:40 | 16:49 |
| Feb 15 | 07:39 | 17:15 | 07:28 | 17:19 | 07:14 | 17:15 |
| Feb 28 | 07:06 | 17:44 | 06:58 | 17:45 | 06:47 | 17:39 |
Phases of the Moon
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| New Moon Saturday 17th |
First quarter Saturday 24th |
Full Moon Friday 2nd |
Last quarter Saturday 10th |
Click HERE to see the phase of the Moon on each day of the month.
What's happening in the night sky?
With January having been unseasonably warm and with several clear nights, there has been plenty of opportunity to get out in the back garden and explore the night sky. The trend should continue through February, although the days are now starting to lengthen noticeably as we move towards spring. So make the most of the dark nights while you can and see if you can spot one of the following monthly highlights before heading off to bed.
Maps of the current night sky can be seen by clicking HERE
February 10th - Saturn at Opposition
At around 7 pm on the 10th, the planet Saturn will reach a stage in its orbit around the Sun known as opposition. This is the point when it will be on exactly the opposite side of the Earth to the Sun. At opposition the outer planets appear high above the southern horizon (assuming we are in the Northern Hemisphere) around midnight. In addition they are also at their closest point to the Earth, so opposition is a great time to look at a planet using a telescope like the Liverpool telescope.
Earth Orbit
The above image shows the names of some of the other points in a planets orbit. These are usually called conjunction because they line up with the Sun. However, there are different types of conjunction depending on whether we are looking at inner planets (Mercury and Venus) or outer planets
Late February - Zodiacal Light
Late February is the best time to look for something known as Zodiacal Light, although you need to be away from streetlights and have a clear moonless night to be in with a chance of seeing it. The zodiacal light is a faint and roughly triangular whitish glow that appears to extend up from the vicinity of the Sun shortly after it has set over the western horizon and the orange glow of twilight starts to fade. It can also be seen above the eastern horizon in late autumn, just before the morning twilight appears - as is seen in the image below.
Image of zodiacal light seen just before morning twilight. Credit: Dominic Cantin
The zodiacal light is produced by sunlight reflecting off dust particles floating around in the solar system, known as cosmic dust. Although it appears faint, because zodiacal light covers the entire sky it is responsible for around 60% of the total skylight on a clear moonless night. The amount of material needed to create the light we see is amazingly small. If all particles were around 1mm in size and as reflective as our own Moon, then calculations suggest they would be around 8 kilometers apart from their nearest dust neighbours.
What are the planets up to?
Click HERE and start the Electric Orrery to see where all the planets are today in relation to each other.
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Mercury - starts
the month as an evening object, remaining over the west-southwestern horizon for
around 90 minutes after sunset. As the month moves on, Mercury positions itself
to pass inferior conjunction (between us and the Sun) on the 23rd, before slowly
emerging from the Sun's glare towards the end of the month as a morning star.
Venus - is the brightest planet at the moment, and will remain an evening object right through until August 2007 as it slowly catches us up on its inside orbit. In early February it can be seen above the southwestern horizon around 2 hours after sunset, but this increases to 2 hours 30 minutes by the end of the month. Why not use the electric orrery to see how Venus slowly catches us up. Mars - appears as a morning object during the month and can be found low above the south-eastern horizon around 70 minutes before the Sun makes an appearance. This slowly increases over the coming months as we catch Mars up on our inside orbit. By the end of February, Mars rises around 5.40 am and can be identified by looking for a reddish star that is shining more steadily (i.e. not twinkling as much) than the others. Jupiter - continues to increase in size and brightness as we slowly catch it up. At the start of February it rises in the southwest around 4.15 am and can be found low in the south-southwest around sunrise. Come the end of the month, it rises a good 90 minutes earlier at 2.45 am. Although Saturn is still the best planet to observe, Jupiter is starting to become a serious contender again. Saturn - remains our primary target for getting reasonable images of a planet. At the start of the month it will rise in the east-northeast around 5.50 pm and reach high above the southern horizon just after midnight. This moves closer to midnight as it approaches opposition (other side of Earth to the Sun) on the 10th. By month's end it will rise during daylight at around 3.45 pm and have set well before sunrise. If you fancy getting an image of a planet, why not try your luck using Go Observing. |
Constellation of the month
Each month, a new constellation is highlighted for you to identify in the night sky.This month we are going to look for the constellation of Canis Major, one of Orion's hunting dogs, which can be found low above the south-eastern horizon around 8pm. The constellation can be found easily by first locating the more famous constellation of Orion, the hunter, and then looking for the bright star Sirius snapping at his heels.
February Night Sky
In fact Sirius, also known as the Dog Star, is the brightest star in the night sky and one of the nearest at just 8.6 lightyears. Although twice as massive as the Sun and 25 times more luminous, Sirius is not considered a particularly bright star. It just appears very bright to us because it is so close.
To help explain, think of 40-watt lanterns being held by a couple of your friends, one standing a few metres away and the other across the playing field. If they switch their lanterns on, the closer one will appear much brighter even though they are pumping out the same amount of light. The same thing happens with stars. Some are actually quite dim (like a 15-watt bulb), but so close to us that they appear bright, whilst others can be incredibly bright (100-watt bulb) but are so far away that they appear dim.
Diagram showing how light rays spread out over distance.
The reason for this is that when light is emitted from a star it starts to spread out. The further it has to travel the more spread out it gets. Look at the image above and imagine your eye as the 'A' squares, which are both the same size but at different distances. If you are closer to the source, more light will enter your eye and your brain registers it as a brighter object than when you are far away.
The lesson we take from this is that you cannot tell how luminous a star really is by how bright it appears to us.
Mythology: Canis Major
Canis Major, the greater dog in Latin, and in particular the bright star Sirius, was often featured in early Egyptian folklore. Sirius was considered very highly by the Egyptians, since its re-appearance in July, after several months absence, coincided with the annual flooding of the Nile, an event so essential to the fertility of the land. Sirius also became known as the "Dog Star", representing the hottest days of summer referred to in bygone times as Dog Days.
In Greek mythology, Canis Major, represented the larger of the two dogs belonging to the great hunter Orion. The dog seems to be in the act of leaping after the Lepus the Hare, and because of his incredible speed, he was honoured by Zeus and placed in the heavens.
