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December 2015: Generally Good.

December 2015

Generally good. In the show this time, we talk to Dr. Tom Kitching about weak gravitational lensing, Mat rounds up the latest news, and we find out what we can see in the December night sky from Ian Morison and Haritina Mogosanu.

The News

In the news this month: one hundred years of general relativity, five fast radio bursts, and one rocky planet.

Interview with Dr. Tom Kitching

Dr Tom Kitching is a Royal Society Fellow and lecturer in the Mullard Space Science Laboratory. His research mainly focuses on weak gravitational lensing and using it to learn more about dark energy and cosmology.

Tom explains how the distortion of light from background galaxies is used to map dark matter in the Universe. Initially it was thought that this approach could be used without fully understanding the physics of galaxies. As with many things in science, it turned out to be a bit more complicated. The disagreement between results from weak gravitational lensing surveys and observations of the cosmic microwave background may suggest we need to improve our understanding of phenomena such as active galactic nuclei before we can make robust measurements using this technique.

Tom is heavily involved with weak lensing with Euclid, an optical telescope set to launch in 2020. He discusses the vast amount of data that will come from this all sky survey and how that's going to change astronomy over the next ten years.

The Night Sky


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.

The image by Damian Peach was taken with a 14 inch telescope in Barbados where the seeing can be particularly good. This image won the "Astronomy Photographer of the Year" competition in 2011.

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

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.

December for most of us is the time when we prepare to celebrate together, another rotation of Earth around the Sun. Of course, whilst modern life's standardisation and globalisation sees more and more people adopting this convention, it was not always like that. Different cultures celebrate the new year at different times of the year.

And it got me thinking.

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?

The Maori have a very special relationship with the Moon. They used the Moon and other celestial bodies to determine time through the year. this enabled the safety of their navigation across the oceans and the safe cultivation of their foods. The moon in new zealand is of a rare beauty as it is birthed from the ocean or it appears from behind the mountains. It appears also upside down to someone like me who is from the other side of the world.

One of our listeners told us that he is always watching the man in the Moon in the northern hemisphere (I remember watching him too) and he was curious about what we see in southern hemisphere. In New Zealand, the Maori see Rona Whakamautai - Rona, the controller of the tides. One evening, Rona travelled down to the river to collect water but the Moon disappeared behind the clouds and she cursed the Moon. Marama, the Moon, heard the curse and said, why curse such beauty when you belong to it? And lifted Rona up to become the woman of the Moon. You can see her laying down after she tripped in the dark over the ngaio tree with her water calabash behind her head. And the ngaio tree in front of her.

I was told once by a school group that there is a rabbit in the Moon. I love the kids' imagination and I always look for both the rabbit and Rona in the Moon.

Back to our stars of the southern hemisphere and the wanderers of the night sky, the generic greek name for the planets, Mercury is the only planet in the evening sky. At the beginning of the month it appears as a bright point setting in the south-west an hour after the sun. It moves slightly higher in the twilight, setting 80 minutes after the sun by the end of the month. Through a telescope it looks like a tiny gibbous moon; a moon between first quarter and full.

The brightest true stars are in the east and south. Sirius, the brightest of all the stars, is due east at dusk, often twinkling like a diamond. Left of it is the bright constellation of Orion. The line of three stars makes Orion's belt in the classical constellation. To southern hemisphere skywatchers they make the bottom of 'The Pot'. The faint line of stars above and right of the three is the Pot's handle. At its centre is the Orion Nebula, a glowing gas cloud nicely seen through binoculars. Rigel, directly above the line of three stars, is a hot blue-giant star. Orange Betelgeuse, below the line of three, is a cooler red-giant star.

Left of Orion is a triangular group making the upside down V of the Hyades. Orange Aldebaran is the brightest star in the V shape. Aldebaran is one of the four royal stars. These royal stars were regarded as the guardians of the sky in approximately 3000 BCE during the time of the Ancient Persians in the area of modern day Iran. The Persians believed that the sky was divided into four districts with each district being guarded by one of the four Royal Stars. The royal stars held both good and evil power and the Persians asked them for guidance in scientific calculations of the sky, such as the calendar and lunar/solar cycles, and for predictions about the future. Other names for the hyades were the little she camels, and were forming the second nakshatra, rohini in hindu astrology.

Still further left is the Pleiades cluster, impressive through binoculars. It is 440 light years away. Pliny talked about them: In cauda Tauri septem quas appelavere Vergilias - at the tail of the bull Vergilias calls seven. The Pleiades seem to be among the first stars mentioned in astronomical literature, appearing in chinese annals of 2357 BC.

Canopus, the second brightest star, is high in the southeast. Low in the south are the Pointers, Beta and Alpha Centauri, and Crux of the Southern Cross. As we mentioned in the November Jodcast, end of November - beginning of December is the time when the grand canoe of tama rereti is the sky. the bright southern Milky Way makes the waters in which the canoe is anchored, with Crux being the canoe's anchor hanging off the side. In this picture the Scorpion's tail is the canoe's prow and the Clouds of Magellan are the sails.

The Milky Way is wrapped around the horizon. The broadest part is in Sagittarius, low in the west at dusk. It narrows toward the Crux in the south and becomes faint in the east below Orion. The Milky Way is our edgewise view of the galaxy, the pancake of billions of stars of which the sun is just one. The thick hub of the galaxy, 30 000 light years away, is in Sagittarius, now low in the west. The nearby outer edge is the faint part of the Milky Way below Orion. A scan along the Milky Way with binoculars will show many clusters of stars and a few glowing gas clouds.

The Large and Small Magellanic Clouds, high in the southern sky, are two small galaxies about 160 000 and 200 000 light years away, respectively. They are easily seen by eye on a dark moonless night. The larger cloud is about 1/20th the mass of the Milky Way galaxy, the smaller cloud 1/30th.

Formalhaut or Hastorang as it was known to the ancient Persians is also one of the four royal stars, it's finding now its true home in the southern hemisphere. I remember watching it in awe from the northern hemisphere, as it was showing the secret passage to the south to those who knew how to read it.

Very low in the north is the Andromeda Galaxy seen with binoculars in a dark sky as a spindle of light. It is a bit bigger than our Milky Way galaxy and nearly three million light years away.

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.

A small telescope shows Jupiter's disk with its four big moons like faint stars lined up on each side. They change sides from night to night as they orbit the planet. Jupiter is 794 million km away mid-month.

The Geminid meteor shower peaks on the morning of the 15th. The meteors appear to come from the constellation of Gemini, low in the northeast at midnight, moving to the north by dawn. The meteors are clumps of dust from a comet. Friction with the air heats them up and makes the air around them glow.

Special Thanks go to Peter Detterline, Chief Astronomer of the Mars Society, Alan Gilmore from University of Canterbury and to Toa Nutone Wii Te Arei Waaka from the Society for Maori Astronomy and Traditions.

This concludes our jodcast for December 2015 at Space Place at Carter Observatory. As the Maori say, E whiti ana nga whetu o te Rangi (the stars are shining in the sky) Ko takoto ake nei ko Papatuanuku (whilst Mother Earth lays beneath)

May you enjoy the end of another happy rotation around the sun! Kia Kaha and clear skies from the Space Place at Carter Observatory in Aotearoa New Zealand.

Odds and Ends

Show Credits

News:Mateusz Malenta
Interview:Dr. Tom Kitching, Monique Henson and Max Potter
Night sky:Ian Morison and Haritina Mogosanu
Presenters:Hannah Stacey, Adam Avison and Fiona Healy
Editors:Benjamin Shaw, James Bamber, Nialh Mccallum, Haritina Mogosanu and Charlie Walker
Segment Voice:Kerry Hebden
Website:Saarah Nakhuda, Charlie Walker and Stuart Lowe
Producer:Charlie Walker
Cover art:A portrait of Albert Einstein, refracted by an almost-perfectly spherical gyroscope used to test his theory of general relativity. CREDIT: Wikimedia Commons

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