Northern Hemisphere

Ian Morison tells us what we can see in the northern hemisphere night sky during December 2015.

Highlights of the month

December - the first good month to view Jupiter
This is the first of several great months to observe Jupiter. It now lies low in Leo and so is still reasaonably high in the ecliptic and hence, when due south, at an elevation of ~45 degrees. It is looking somewhat different than in the last few years as the north equatorial belt has become quite broad. The Great Red Spot is currently a pale shade of pink but can be easily seen as a large feature (which appears to be shrinking in size) in the South Equatorial Belt.
The features seen in the Jovian atmosphere have been changing quite significantly over the last few years - for a while the South Equatorial Belt vanished completely (as seen in the accompanying image by Damian Peaches) but has now returned to its normal wide state. The diagram on right shows the main Jovian features as imaged by the author at the beginning of December 2012.



See more of Damian Peach's images: Damian Peach's Website

December - Comet Catalina heads upwards to Arcturus
As December progresses, a bright comet, 2013 US10 Catalina, will rise up into our pre-dawn skies. Initially lying close to the Virgo-Libra border, it is heading north at a rate of more than half a degree a day and, by month's end, will be easily found as it lies close to Arcturus in Bootes. By the 10th December it will stand ~20 degrees above the south-eastern horizon at 06:00 UT lying some 6 degrees above Venus. So simply find Venus in binoculars and slowly sweep up and to the left to find the comet. The best guess as to its brightness is that it will be ~5th magnitude - so not visible to the unaided eye but easily visible in binoculars.

December 4th: Jupiter and the Moon
Before dawn and looking south-east will be seen, if clear, Jupiter just over 2 degrees above the 3rd quarter Moon in Leo.

December 6th: Mars and the Moon
Before dawn and looking east will be seen, if clear, Mars just 2 degrees above the waning Moon in Leo.

December 7th and 8th: Venus and the Moon
Before dawn and looking to the east will be seen, if clear, Venus within 5 degrees (below on the 7th and above on the 8th) of a waning crescent Moon.

December 14th and 15th after midnight: the Geminid Meteor Shower
The early mornings of December 14th and 15th will give us the chance, if clear, of observing the peak of the Geminid meteor shower. Happily, this is a good a year as the waxing crescent Moon will not hinder our view. An observing location well away from towns or cities will pay dividends though. The relatively slow moving meteors arise from debris released from the asteroid 3200 Phaethon. This is unusual, as most meteor showers come from comets . The radiant - where the meteors appear to come from - is close to the bright star Castor in the constellation Gemini as shown on the chart. If it is clear it will be cold - so wrap up well, wear a woolly hat and have some hot drinks with you.

December 22nd/23rd - midnight onwards : the Ursid Meteor Shower
The night of the 22nd/23rd December is when the Ursid meteor shower is at its best - though the peak rate of ~10-15 meteors per hour is not that great. The Moon is just before full so I suspect only a very few of the brightest meteors to be seen. The radiant lies close to the star Kochab in Ursa Minor (hence their name), so look northwards at a high elevation. Occasionally, there can be a far higher rate so its worth having a look should it be clear.

December - 13th and 29th: The Alpine Valley
An interesting valley on the Moon: The Alpine Valley
These are good nights to observe an interesting feature on the Moon if you have a small telescope. Close to the limb is the Appenine mountain chain that marks the edge of Mare Imbrium. Towards the upper end you should see the cleft across them called the Alpine valley. It is about 7 miles wide and 79 miles long. As shown in the image a thin rill runs along its length which is quite a challenge to observe. Over the next two nights following the 3rd/4th the dark crater Plato and the young crater Copernicus will come into view. This is a very interesting region of the Moon!

Observe the International Space Station
Use the link below to find when the space station will be visible in the next few days. In general, the space station can be seen either in the hour or so before dawn or the hour or so after sunset - this is because it is dark and yet the Sun is not too far below the horizon so that it can light up the space station. As the orbit only just gets up the the latitude of the UK it will usually be seen to the south, and is only visible for a minute or so at each sighting. Note that as it is in low-earth orbit the sighting details vary quite considerably across the UK. The NASA website linked to below gives details for several cities in the UK. (Across the world too for foreign visitors to this web page.)

Note: I observed the ISS three times recently and was amazed as to how bright it has become.

Find details of sighting possibilities from your location from: Location Index

See where the space station is now: Current Position

The Planets

• Jupiter
  Jupiter shining at magnitude -2, rises at around 00:30 UT at the beginning of the month lying low down in Leo close to the boundary with Virgo into which it moves early in January. By month's end it rises about 22:30 UT and shines at magnitude -2.2 whilst, during the month, its angular size increases from 35.6 to 38.9 arc seconds It will then be due south and so highest in the sky at an elevation of 44 degrees at around 05:00 UT in the pre-dawn sky. As the Earth moves towards Jupiter, early risers should be able to easily see the equatorial bands in the atmosphere and the four Gallilean moons as they weave their way around it.
• Saturn
  Having passed behind the Sun on the 20th of November may be seen again around mid December rising an hour before sunrise. Sadly, it is lying in the southern part of Ophiuchus just over 6 degrees above Antares in Scorpius so its elevation when on the meridian next year will be only be 20 degrees above the horizon. It will be shining at magnitude +0.4 and, by the end of the month, be high enough in the south-east before dawn to make out the beautiful ring system which has now opened out to ~25 degrees. By month's end it rises around an hour earlier, some 2 hours before the Sun and we will see it approached by Venus as it returns towards the Sun.
• Mercury
  Mercury, at magnitude -5 may be seen at the end of the month low in the south-western sky as it reaches greatest elongation on the 29th of December when it lies 20 degrees from the Sun. It will be only a few degrees above the horizon at twilight and so the use of binoculars and a low horizon will be needed to spot it - but please do not try until after the Sun has set!
• Mars
  Mars rises in the east about 2 hours before the Sun at the start of December and about half an hour earlier as we move towards the new year. It brightens from +1.5 to +1.3 when it be nearly as bright as Spica, in Virgo, when it passes about 4 degrees up and to its left on the mornings of the 23rd and 24th of the month. It passes close to the double star Porrima at the beginning of December and, on the 12th and 13th skirts, 4th magnitude star, Theta Virginis. Mars' angular diameter will have reached just 5 arc seconds by the 10th of the month so it will be hard to spot any details on its salmon-pink surface. By month's end Mars will have reached an elevation of 28 degrees above the south-eastern horizon as dawn appears in the sky. At its closet approach in May next year its angular size of ~18 arc seconds will be greater than any time since 2005.
• Venus
  Venus, is now moving back towards the Sun but, by month's end still rises almost three hours before sunrise. A telescope will show that its angular size reduces from 17.5 to 14.5 arc seconds during December but at the same tine the illuminated percentage of the surface increases from ~66 percent to ~75 percent which is why the magnitude only drops from -4.2 to -4.1. Venus will lie some 5 degrees from Spica in Virgo at the start of the month, pass by the double star Alpha Librae on the 17th and 18th and will be very close to Beta Scorpii as we reach the New Year.

Southern Hemisphere

Haritina Mogosanu from the Carter Observatory in New Zealand tells us about the southern hemisphere night sky during December 2015.

Welcome to December. My name is Haritina Mogosanu and today I am your starryteller from Space Place at Carter Observatory in Aotearoa, New Zealand. The name December comes from Latin, meaning the tenth. In ancient times, it was the tenth month from the beginning of the year.





Where do calendars come from? What do people see when they look at the Stars and the moon and what do these celebrations mean for us in general? And what was their connection to the land?

























Jupiter, Mars and Venus are all visible in the morning sky. Saturn joins them at the end of the month. At the beginning of December Jupiter rises around 2:30 a.m.; reducing to 12:30 a.m. by the 31st. It is a bright golden-coloured 'star' shining with a steady light. Venus is up around 4 a.m., a brilliant object bright enough to cast shadows in dark locations. Mars is between the two bright planets, looking like a medium-bright reddish star. Jupiter and Mars rise steadily earlier while Venus stays put in the dawn. In the second half of the month Mars is near, then passing below, the bluish-white star Spica, the brightest star in Virgo. At the end of the month Saturn emerges from the dawn twilight below and right of Venus, at the bottom end of the diagonal line of planets. The crescent moon will be close to Venus on the morning of December 8th.









Kia Kaha and clear skies from the Space Place at Carter Observatory in Aotearoa New Zealand.