Last night I watched an asteroid --- 2004 BL86 --- drift past the Earth. There was never any danger of a collision and it never got closer than about 3x the distance of the Moon. Nevertheless it was an interesting event to watch through the telescope. The asteroid was tracking north through the evening sky. At around 7.30pm, when I arrived home from work, it was too low in the southeast sky in Hydra. As the evening went on it raced north towards the constellation Cancer.
The animation below was made from frames taken over a ten minute period at around 9.30pm. The asteroid moved across a patch of sky about the size of the full moon during this period.
I stacked the images to make this picture:
I'm not sure why the asteroid has a strong green colour! It may be that the presence of moonlight in the sky messed up the colour balance during post processing.
Just to put this into some kind of perspective: the asteroid is about half a mile in diameter and it was around 1 milliion miles away when I took the pictures. Shining at around 9th magnitude, the asteroid was much too faint to be seen without optical aid. I saw several articles on astronomy and science websites suggesting that binoculars would have been enough. The fact of the matter is that at least a small telescope would have been needed by most observers unfamiliar with searching for faint objects.
Radar surveys of the asteroid carried out yesterday showed this tiny asteroid had a moon!
This is second time I've caught an asteroid close approach. I was lucky enough to catch the even closer approach by an asteroid called Duende (formerly 2012DA14) in 2013.
Comet 2014 Q2 Lovejoy will be at its closest point to the Sun on January 30th - a mere 120 million miles from it. Despite being further from the Sun (by 27 million miles) than us, Comet Lovejoy is glowing in our northern sky more brightly than any comet since Comet 2011 L4 PANSTARRs in 2013. Comet Lovejoy is starting to fade but remains excellently placed in the northern sky for UK astronomers.
The chart below shows the path of Comet Lovejoy from the last week of January until the start of March. During this period the comet is expected to fade from magnitude +5 to +8. Comets are somewhat unpredictable and those estimates don't take account of sudden outbursts caused by unstable conditions on the comet.
During the past few weeks I've tried to get pictures of Comet Lovejoy on lots of occasions. Here are a couple of my best pictures:
That delicate ion tail has been very difficult to see both visually through the telescope eyepiece and on camera. It's not helped that someone thought it a good idea to build Newcastle not far from here. And even less of a good idea to fill it with streetlights. Makes it almost impossible to get dark skies from my back garden.
The comet begins February in the constellation Andromeda, near second magnitude star Almach (itself a superb double star through telescopes). An excellent photographic opportunity occurs on the evening of February 20th/21st when the comet will be very close to the Little Dumbbell nebula (M76) in Perseus.
During March the comet will fade to the point where only telescopes can resolve the coma as it begins to blend into the rich starfields of Cassiopeia.
Patrick Moore poularised the star pattern called the Summer Triangle in books and on The Sky at Night from the 1950s on. A less well known asterism for this time of the year is the Winter Hexagon. Here it is!
The mathematical part of my brain says No! Seven stars makes seven sides! That should be Winter Heptagon! But before it gets too carried away about the exact nature of the shape...it's already too well known as a hexagon to change it now. I suppose two of the stars are almost on a straight line. Enough.
It's a huge asterism. The angular distance between the top (Capella) and bottom (Sirius) is around 66 degrees. Capella is almost overhead in the UK during winter evenings, while Sirius is low above the southern horizon.
Here are some factoids about the seven stars of the WInter Hexagon:
Much of the constellation Orion is contained within the Winter Hexagon. Looking at the shape I feel that Betelgeuse should somehow be included - a brightest star inside it but offset from the centre.
Just to put the WInter Hexagon into context - here is a Stellarium rendition of the sky with the familiar constellations in place along with the Hexagon.
Comet 2014 Q2 Lovejoy is really starting to put on a great show for UK astronomers. At last, it is north of the celestial equator and shining brightly enough to be visible to the naked eye. My camera remote control has died so the pictures below were taken with my dad's superior Nikon D90.
This was my view of the southern sky at about 6.30pm last night:
Comet Lovejoy was easily visible in the sky. At first glance it looks like a faint star but using averted vision it does look somewhat fuzzy. The cometary nature is revealed easily with binoculars.
A closer view of Comet Lovejoy as it passes through a beautiful part of the sky near Taurus, the Bull.
Finally, here's a telescope view of the comet revealing many delicate streams of material pushed away from the comet by the solar wind.
Comet Lovejoy was about 45 million miles from Earth last night. Although it's getting further away from us, it is continuing to approach the Sun. It will remain an easy target over the next couple of weeks for binoculars and small telescopes.
The clouds cleared for a couple of hours yesterday afternoon and I got a chance to see Mercury catching up to Venus in the evening sky. This was the view from my garden in Red Row.
The distance between them was about half a degree; closer than your little finger at arms length! You can just about see my telescope in the foreground of the picture. When I put the camera on that I got this view:
Venus is much brighter than Mercury. Both planets are almost behind the Sun as seen from Earth but Mercury is nearest to us. However, Venus is much bigger and has very reflective clouds whilst Mercury has no atmosphere and a dark, dusty surface. The upshot is that Venus always outshines Mercury.
This year promises to be a bumper year for astronomy events and space exploration.
It's already off to a good start with Comet Lovejoy in the evening sky. In January and February the comet should be quite easy to see with binoculars and telescopes as it heads north of the equator. Probably visible to the naked eye during January away from town and city lights.
In March a NASA mission to explore new worlds will reach a milestone. The Dawn spacecraft has spent a few years in the asteroid belt between Mars and Jupiter. Dawn spent a year orbiting and mapping Vesta, one of the largest asteroids. After leaving Vesta, Dawn has coasted out to meet the biggest asteroid of all: Ceres. Not that much is known about Ceres at present. It may turn out to be the core of a rocky planet that never got the chance to grow into a big rocky planet like Earth did.
Another NASA mission called New Horizons will complete its 9 year journey in July when it zips by distant planet Pluto. When I was young Pluto was basically an unknown dot in photographs. Initially thought to be Earth sized, astronomers now know it’s smaller than our moon. It also orbits in a region of space brimming with similar icy objects. Astronomers re-classified Pluto as a Dwarf Planet some years ago. New Horizons will at least show us this bizarre world in close up for the first time and send back images of Pluto and its system of at least five moons.
During 2015 Rosetta will continue to orbit the comet as it approaches perihelion. Perhaps it will witness a flurry of activity as the Sun warms the surface of the comet. It remains a possibility that the Philae lander might reawaken if the changing position of the comet and Sun can recharge the ailing lander's battery.
In the early hours of September 28th another total eclipse – this time lunar – as the moon passes through the shadow of the Earth. Not all of the light is blocked and sunlight is reddened by our atmosphere and bent towards the moon, turning it orange and red for more than an hour.
The planets will put on a nice show at various times in 2015. During January the planets Mercury, Venus and Mars will make a nice group in the western sky after sunset. And on mornings in late October there'll be a chance to see Mercury, Venus, Mars and Jupiter in the eastern sky before sunrise. In all there will be a least 12 observable planetary conjunctions in 2015.
Of the meteor showers this year - it's going to be good year to see the Perseids in August. The peak of the shower occurs two days before New Moon. The December Geminids take place a couple of days after New Moon this year. That should ensure lots of shooting stars are visible near the peak.
All of these events are coming this year along with the usual planetary gatherings, meteor showers and with luck – the northern lights!
If you glance towards the southwest at around 4.30pm to 5pm you shouldn't have too many problems spotting the planet Venus. Over the coming months it'll gradually get easier to see as the Venus-Sun-Earth angle widens and the planet climbs higher into the evening sky.
Here's a picture I took from an upstairs window at home about 45 minutes after sunset. Venus is pretty obvious, just beneath the three telephone cables.
During the next couple of weeks the smallest planet in the solar system will join Venus. In fact the camera picked up Mercury this evening. It's already in the same part of the sky and my camera managed to capture enough photons of light from Mercury to register in the picture above. I've cropped and enhanced the region with both planets to try and bring out Mercury more clearly:
I didn't see Mercury visually or through the camera lens. I think I would've been able to see it about 10 minutes later after the sky had darkened a bit more but by that time it was behind the tree tops in the picture.
Comet 2014 Q2 Lovejoy continues to head north towards the celestial equator. The view is improving every evening. Or at least it would if the moon wasn't around.
Here are a couple of pictures of Comet Lovejoy taken from my home in Red Row, Northumberland:
The picture on the left was a short exposure taken with my Nikon D80 on a fixed tripod looking towards the south. There's a lot of light pollution but the camera just about picks up the comet. It was easily visible with binoculars and I estimated the diameter of the coma to be about 20 arcminutes. The picture on the right was a stack of 9x60 second exposures. The images were centred on the comet and, since it's moving through space, the stars are trailed.
Moonlight is going to prevent me getting more pictures until after the first week of January. By that time Comet Lovejoy will be a lot higher in the sky and hopefully twice as bright as it is at the moment.
This is how the evening sky looks in January 2015. Click to embiggen!
The Moon and the hours of darkness
The best evening opportunities to have moonless sessions of astronomy come in the middle two weeks of January, after last quarter moon and until around the time of first quater.
Stars and constellations
Beneath the Belt stars is a compact group of stars known as Orion's Sword. Binoculars show this region has a large fuzzy region, which telescopes reveal to be a bright nebula --- the Orion Nebula. The other stars of the Sword are revealed to be star clusters rather than individual stars.
The whole region is superb to see with telescopes of any size.
The three prominent Belt stars, which make an almost perfect straight line, point upwards towards Taurus and the orange star Aldebaran, marking the eye of the Bull. Follow the line of the Belt stars down towards the horizon and you'll see the madly twinkling Sirius - the brightest star in the sky.
The Milky Way runs from northwest to southeast in the sky. Although this section of the Milky Way is less prominent than the part visible in the late summer and autumn in the UK, there are numerous star clusters and nebulae visible with binoculars and small telescopes as it flows through Auriga, Gemini and to the east of Orion and on to Canis Major in the south.
By contrast, the western part of the evening sky is fairly devoid of the bright stars. The autumn patterns of the Square of Pegasus, Pisces and Cetus mark a direction in which we can look out of the plane of the Milky Way, where there are fewer stars in that direction between us and the great voids between other galaxies.
In the east, particularly later in the evening, the galaxy filled constellations of Leo and Virgo are coming into view.
The first half of January sees a rare opportunity to spot three planets in the same part of the sky. Mars has been in the evening sky for months already but it is joined by Mercury and Venus which are both emerging from behind the Sun. Venus is the brightest of the three by far. Mars is the faintest and is distinguished by its strong orange colour. Look towards the western horizon in the middle two weeks of January to see all three together.
Meanwhile, on the other side of the sky the planet Jupiter shines brilliantly among the stars of Leo. It is far brighter than any star in the sky. Jupiter is nearly on the opposite side of the sky to the Sun and is visible for most of the night. Saturn can be found low in the southern sky before dawn shining as brightly as the brightest stars. Binoculars are sufficient to glimpse the ice giant planet Uranus in the constellation Pisces.
Related blog post and more details of 2014 Q2 Lovejoy here.
The annual Quadrantid meteor shower is active between December 28th and January 12th. The peak in 2015 comes on the evening of January 3rd, with the best time to observe being the early hours of January 4th. During the narrow peak rates as high as 120 meteors per hour might be possible. Unfortunately, an almost full moon will drown all but the brightest out of visibility.
The Quadrantid meteors radiate away from the border of the constellations Bootes and Hercules and it is named after a now defunct constellation – Quadrans Muralis - the Mural Quadrant.
The Cassini spacecraft captured this breathtaking view of Saturn on May 4th 2014 but I just noticed it today.
Cassini captured this view at a distance of approximately 2 million miles (3 million kilometers) from Saturn using a near infrared filter. Cassini was high above the ring plane and this is a view of the planet we never get from Earth. From our position near the centre of the solar system Saturn (and most of the planets beyond Earth) look fully illuminated all of the time.
One of the features that immediately catches the eye is that hexagon shape around the north pole of Saturn. The hexagon at Saturn's north pole isn't a new feature. It was seen in images taken by the Voyager 1 and 2 probes back in the 1980s.
Here are some closer Cassini views of it:
For some sense of scale: each side of the hexagon is a bit wider than the Earth.
Saturn is a rapidly rotating gas giant planet. How can a regular and seemingly long-lived feature like this arise in the atmosphere of Saturn? Astronomers don't have the definitive explanation yet although there is experimental evidence from laboratories on Earth which might give a clue.
The video shows an experiment to simulate conditions that might lead to a regular structure being set up in the atmosphere of Saturn. They built a cylindrical tank capable of varying the fluid flow within concentric regions inside. A hexagon appeared at the chaotic boundary between fluids moving at very different speeds. A number of vortices formed in the region separating the fluid flow and distributed themselves evenly around the pole at centre. Why a hexagon? Actually the experimenters could fine tune the spin rates to produce a hexagon but they could also generate other regular polygons too. You can see some them here.
The experiment showed how stability and order could arise from chaotic conditions induced by large differences in wind speeds at different latitudes on Saturn. There are still questions to be answered. For instance why is there no comparable feature at the south pole of Saturn? There is a huge, long-lived storm at the south pole, but no polygonal structure.
I love trawling through the raw image section of the Cassini website. It can lead to serious distraction no matter if they're images of the rings, the moons or Saturn itself. But I'm aware that this mission won't last forever; Cassini's time is running out and sometime in 2017 NASA scientists will place it in a final series of orbits which will send it crashing into Saturn.