December - Geminids: The Celestial Fairy Lights

The winter skies are some of the most favourable for astronomy, both in terms of available targets and time in which to observe them (though the weather means that even the keenest amateur astronomer daren’t venture out for more than a few hours at a time!). With the Winter Solstice on the 22nd, there is over twelve hours of true astronomical darkness (where the sun is over 12˚ below the horizon; this is approximately 3 hours shorter than the time described by civil twilight).

For those willing to brave the cold there is plenty of planetary astronomy to be done; Venus is prominent at dusk, shining at magnitude -3.8 low on the South-Western horizon. At a separation of 31˚ from the sun, you have over an hour after sunset (currently about 4pm) to view the planet; its disk shows no surface features due to the thick atmosphere, but it’s brilliance and display of phases at least makes it worth a look. Mars has begun to make its presence felt in the late evening skies, rising at 10:30pm by the end of the month; it still has a while to go before it reaches opposition next March and as such the disk is small and needs a decent telescope to resolve. The moon is full on the 10th, waning to new on the 25th, while Jupiter is (as ever) very prominent in the sky, with its dynamic surface and moons always worth a look.

There are two meteor showers of note this month, the first of these being the Geminids, which peak on the 13th and 14th of December. The radiant is located just to the North of Castor, one of the two brightest stars in the constellation of Gemini. With typically bright white, slow moving meteors and a ZHR* of 60-70 this shower is often one of the most spectacular of the year, though this time the presence of a near-full moon in neighbouring Cancer will severely hamper viewing. The parent body 3200 Phaethon is not a comet, but a 5km asteroid which is thought to have undergone a major orbit-altering collision in astronomically recent times; small increases in activity have been noted in this shower over numerous years which imply continuing redistribution of the debris trail. The second shower this month is the somewhat smaller Ursids, peaking between the 17th and 25th of December with a radiant near the main body of Ursa Minor. These do have the advantage of dark moonless skies, but the expected ZHR of 10-15 means they are still unlikely to be as impressive as the Geminids which precede them.

For all showers, the best technique for observing is to lie back in a space with a relatively clear horizon, but which puts any direct sources of light (including the moon) out of your field of vision; then just sit back, relax and watch the show!

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*Zenithal Hourly Rate; the average number of meteors visible per hour to an observer with a clear horizon - in practice you would have to be very lucky to see this many!

This is the November Astrosoc bulletin. Written by Michael Wilby

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Now that the clocks have gone back, the long (and of course cold) nights of deep astronomical darkness are setting in; personally I find the winter sky to be one of the most spectacular, as it contains a wealth of objects of all types and many easily identifiable constellations.

The moon is full this month on the 10th when it passes close by Jupiter; it then proceeds to wane to new on the 25th. While the gas giant has passed its opposition on the 29th, Jupiter is still going to be very prominent in the evening sky for the next few months and is, as ever, an excellent target.

One of the most iconic and easily identifiable constellations is sidling into the evening sky this month; Orion is currently rising at approximately 9pm, but by the end of the month will be fully visible by 8pm. It contains one of the most active star forming regions in our Sun’s neighbourhood, vast clouds of gas which lie in the line of our spiral arm; the most famous of these is the Orion Nebula (M42) which is easily identifiable even without any optical aid. With a telescope it is possible to discern more of the nebula’s extent, as well as the central trapezium of young stars which are currently blowing off their surrounding gas cocoon. Other notable nebulae in the constellation include the Running Man Nebula, Horsehead and Flame nebulae while all lie above M42 towards the belt of Orion (see the attached photo, which was taken by a friend from his back garden using amateur equipment).

Orion also contains two stars at the other end of their lives; the blue supergiant Rigel is found in the lower right of the ‘hourglass’ shape of the constellation, but the real show is Betelgeuse, the brightest star in the constellation at magnitude +0.45. At 20 times the mass of the sun it is in its Red supergiant phase, and is likely to be the next star in our galaxy to explode as a supernova!

There are numerous small meteor showers occurring this month; the first of which is the Taurids on the 5th, with the Northern Taurids and Leonids following on the 12th and 15th respectively. These all have expected ZHR of around 15 (Zenithal Hourly Rates - the expected number of meteors visible to an observer with a clear horizon). These are all due to different comet trails across Earth’s orbit, and are a warm-up to the real star of the winter meteor showers; the Geminids next month.

By Michael WIlby and Katie Vokes

October - Jupiter, the Bringer of Jollity

As we start the new academic year, we have all but lost the summer twilight and the inconvenience it causes; dusk is approximately 8:30pm and gives the dedicated observer over nine hours of true astronomical darkness (but don’t worry; there’s no obligation to be out for all of it, even on obs nights!). The moon will be waxing for the first part of the month, reaching full on the 12th before waning back to new on the 26th.

The planet Jupiter has been visible for a while now in the evening sky, but on the 29th this month it reaches opposition; being at its closest point to earth, Jupiter is also at its brightest and is visible all night. Appearing to the naked eye as a bright -2.8 magnitude star near Aries, with binoculars its disk and four Galilean moons are revealed, while a telescope will show  details on the stormy surface including the Great Red Spot and if lucky (or with good timing) shadows of the moons as they transit across the face of the planet. Compared to the previous few years, this apparition reaches higher altitude in the sky, meaning we should be in for a good show!

Another prominent solar system object this month is the comet Elenin; it can be found moving between the constellations of Leo and Gemini, dimming as it does so from magnitude +4 to +6. While this currently makes it a morning object (currently rising at 4:30am, but moving forward to 9pm by the end of the month), it’s brightness means it should be visible to the naked eye and easy to spot through binoculars; after a long spell with little to no cometary activity it should certainly be one to watch. A second fainter comet, Garradd, is also visible in the evening sky, passing slowly through southern Hercules and should be visible with binoculars.

In terms of deeper-sky targets, the Pleiades star cluster (M45) can easily be spotted in Taurus, whilst the Double Cluster in Perseus is a good sight for telescope users.  The large square of Pegasus is prominent in the sky, and in adjacent Andromeda lies our nearest galactic neighbour, the Andromeda Galaxy (M31). At magnitude +3.5, it appears excellently through binoculars or a telescope, but can often be glimpsed with the naked eye.

Amongst the galaxies to be found in Ursa Major are the Pinwheel Galaxy (M101), the location of a recent supernova, and the pair of Bode’s Galaxy (M81) and the Cigar Galaxy (M82), which are easier to see and can be framed in a single field with a small telescope. Globular clusters visible at this time include M15 and M2, quite close to each other in the sky, located in Pegasus and Aquarius respectively, as well as M13 in Hercules, which is now getting lower in the sky.

Hi all, it's great to be back in Durham for what looks to be a promising year for AstroSoc! We drew considerable interest at the Freshers' Fair, and to those have joined or are about to join us, I say welcome. My name is James, I am the president and our job is to make sure that you never gaze upon a clear night sky in the same way again! We kick off this year with the Freshers' Obs this Saturday, for which you should already have received an email. There you can see what we're all about, as well as introduce yourselves to each other and to us. We have plenty of events in store for the rest of the year, but for now, let us hope for clear skies this weekend!

Best Wishes

James