Archive for the ‘Moon’ Category
Tonight (actually around 0130 tomorrow morning) the Full Moon will reach its highest point due south, just an hour and a half after the eclipse ends. Despite being at its highest in the sky, you’ll still struggle to see it, as it is very low down. In fact the Full Moon nearest the Summer Solstice is the lowest Full Moon of the Year
First, let’s begin with the definition of “Full Moon”. A Full Moon occurs when the Moon is diametrically opposite the Sun, as seen from the Earth. In this configuration, the entire lit hemisphere of the Moon’s surface is visible from Earth, which is what makes it “Full”. There is an actual instant of the exactly Full Moon, that is the exact instant that the Moon is directly opposite the Sun. Therefore when you see timings listed for the Full Moon they will usually include the exact time (hh:mm) that the Moon is 180° round from the Sun (we call this point opposition). Here’s a list of the times of all Full Moons between June 2011 and June 2012:
|Month||Date of Full Moon||Time of Full Moon (UT)|
|June 2011||15 June||2014*|
|July 2011||15 July||0640*|
|August 2011||13 August||1857*|
|September 2011||12 September||0927*|
|October 2011||12 October||0206*|
|November 2011||10 November||2016|
|December 2011||10 December||1436|
|January 2012||09 January||0730|
|February 2012||07 February||2154|
|March 2012||08 March||0939|
|April 2012||06 April||1919*|
|May 2012||06 May||0335*|
|June 2012||04 June||1112*|
* UK observers should add on one hour for BST As you can see from this table, the instant of the Full Moon can occur at any time of day, even in the daytime when the Moon is below the horizon. So most often when we see a “Full Moon” in the sky it is not exactly full, it is a little bit less than full, being a few hours ahead or behind the instant of the Full Moon. I’ll refer to this with “” marks, to distinguish this from the instant of the Full Moon (they look virtually identical in the sky). The Moon rises and sets, like the Sun does, rising towards the east and setting towards the west, reaching its highest point due south around midnight (although not exactly at midnight, just like the Sun does not usually reach its highest point exactly at noon). And like with the Sun the maximum distance above the horizon of the “Full Moon” varies over the year. The Sun is at its highest due south around noon on the Summer Solstice (20 or 21 June) and at its lowest due south around noon on the Winter Solstice (21 or 22 Dec) (of course the Sun is often lower than this, as it rises and sets, but we’re talking here about the lowest high point at mid-day, i.e. the day of the year in which, when the Sun is at its highest point that day, that height is lowest…) And because Full Moons occur when the Moon is directly opposite the Sun, you can imagine the Moon and Sun as sitting on either sides of a celestial see-saw: on the day when the Sun is highest in the middle of the day (in Summer), the Moon is at its lowest high point at midnight; and on the day when the Sun is at its lowest high point in the middle of the day (in Winter), the Moon is at its highest high point at midnight. This means, in practical terms, that Summer “Full Moons” are always very low on the horizon, while Winter “Full Moons” can be very high overhead. Here’s a table of the altitude of the “Full Moon” when due south. Remember the times in this table don’t match the exact time of the Full Moon, but instead have been chosen as the closest in time to that instant, and so have be labelled “Full Moon” (in quotes).
|Month||Date of Full Moon||Time of Full Moon (UT)||Time/Date of “Full Moon” due S||Time from/since instant of Full Moon||Altitude due S (degrees)**|
|June 2011||15 June||2014*||0127BST 16 June 2011||+4h13m||10° 05′|
|July 2011||15 July||0640*||0012BST 15 July 2011||-7h28m||10° 24′|
|August 2011||13 August||1857*||0126BST 14 August 2011||+5h27m||19° 19′|
|September 2011||12 September||0927*||0049BST 12 September 2011||-9h38m||31° 49′|
|October 2011||12 October||0206*||0053BST 12 October 2011||-1h13m||44° 16′|
|November 2011||10 November||2016||0005GMT 11 November 2011||-3h49m||53° 24′|
|December 2011||10 December||1436||0030GMT 11 December 2011||+9h54m||56° 03′|
|January 2012||09 January||0730||0006GMT 09 January 2012||-7h24m||53° 36′|
|February 2012||07 February||2154||0031GMT 08 February 2012||+2h37m||43° 47′|
|March 2012||08 March||0939||0000GMT 08 March 2012||-9h39m||35° 37′|
|April 2012||06 April||1919*||0145BST 07 April 2012||+5h26m||21° 45′|
|May 2012||06 May||0335*||0102BST 06 May 2012||-3h33m||15° 20′|
|June 2012||04 June||1112*||0047BST 04 June 2012||-11h25m||11° 49′|
* UK observers should add on one hour for BST ** The altitude here is based on my observing location in Glasgow, Scotland. You can find out how to work out how high these altitudes are here. As you can see from this table, the highest “Full Moon” due S this year occurs at 0030 on 11 December 2011, when the Moon will be over 56° above the southern horizon (approximately the height of the midsummer mid-day Sun which culminates at 57°34′). Compare this to the “Full Moon” this month, just after the eclipse, in the morning of 16 June, when the Moon barely grazes 10° above the horizon, and you can see just how low the midsummer Full Moon can be. In fact the closeness of summer “Full Moons” to the horizon means that this is an ideal time of year to try and observe the Moon Illusion.
The first total eclipse of the Moon of 2011 occurs this Wednesday evening, 15 June 2011, and it will be the longest lunar eclipse in over a decade. However the views from the UK (and Europe) will be constrained by the fact that the Moon will be below the horizon for much of the eclipse, and will rise fully eclipsed, or in some cases even coming out of eclipse. It’s still worth having a look though: just try to find somewhere with a very low and clear SE horizon, as this will be the direction in which the Moon will rise, and it will be in eclipse only while it is VERY low (only a few degrees above the horizon).
A lunar eclipse occurs when the Moon, in its orbit around the Earth, passes into the Earth’s shadow, as cast by the Sun. You might imagine that this would happen once every lunar orbit, or once a month. That it does not is due to the fact that the Moon’s orbit around the Earth is tilted by around 5 degrees compared with the Earth’s orbit around the Sun. So in most orbits the Moon passes above or below the Earth’s shadow.
Please read the rest of this article on Dark Sky Diary
I’ll make a prediction: on or around 19 March, when the so-called “Supermoon” occurs, at its closest approach to Earth in two decades, people will indeed report that the Moon looks much bigger than normal. But it won’t really be much bigger in the sky at all. It’s all in our heads!
You’ve probably all seen it before, a huge Full Moon sitting on the horizon. Time and again I have had people ask me why the Moon is so much bigger some times than others, and the answer is: it isn’t, really.
The Moon orbits the Earth in an elliptical orbit, meaning that it is not always the same distance from the Earth. The closest the Moon ever gets to Earth (called apogee) is 364,000km, and the furthest is ever gets (perigee) is around 406,000km (these figures vary, and in fact this Full Moon on 19 March 2011 will see a slightly closer approach of 357,000km).
So the percentage difference in distance between the average perigee and the average apogee is ~10%. That is, if the Full Moon occurs at perigee it can be up to 10% closer (and therefore larger) than if it occurred at apogee.
This is quite a significant difference, and so it is worth pointing out that the Moon does appear to be different sizes at different times throughout the year.
But that’s NOT what causes the Moon to look huge on the horizon. Such a measly 10% difference in size cannot account for the fact that people describe the Moon as “huge” when they see it low on the horizon.
What’s really causing the Moon to look huge on such occasions is the circuitry in your brain. It’s an optical illusion, so well known that it has its own name: the Moon Illusion.
If you measure the angular size of the Full Moon in the sky it varies between 36 arc minutes (0.6 degrees) at perigee, and 30 arc minutes (0.5 degrees) at apogee, but this difference will occur within a number of lunar orbits (months), not over the course of the night as the Moon rises. In fact if you measure the angular size of the Full Moon just after it rises, when it’s near the horizon, and then again hours later once it’s high in the sky, these two numbers are identical: it doesn’t change size at all.
So why does your brain think it has? There’s no clear consensus on this, but the two most reasonable explanations are as follows:
1. When the Moon is low on the horizon there are lots of objects (hills, houses, trees etc) against which you can compare its size. When it’s high in the sky it’s there in isolation. This might create something akin to the Ebbinghaus Illusion, where identically sized objects appear to be different sizes when placed in different surroundings.
2. When seen against nearer foreground objects which we know to be far away from us, our brain thinks something like this: “wow, that Moon is even further than those trees, and they’re really far away. And despite how far away it is, it still looks pretty big. That must mean the Moon is huge!”.
These two factors combine to fool our brains into “seeing” a larger Moon when it’s near the horizon compared with when its overhead, even when our eyes – and our instruments – see it as exactly the same size.
There seems to be a growing excitement about the “Supermoon” that is due to occur on 19 March 2011, when the Moon will be at its closest to Earth in this orbit, and closer than it has been at any time since 1992.
The Moon orbits the Earth in an elliptical orbit, i.e. it is not perfectly circular, and so in each orbit there is a closest approach, called “perigee” and a furthest approach, called “apogee”.
At this month’s perigee the Moon will be 356,577km away from Earth, and will indeed be at its closest in almost 20 years. But how close is it compared with other perigees?
Let’s start by comparing it to the Moon’s average distance from the Earth, which is ~385,000km. This perigee will be ~8% closer to the Earth than average. OK, that’s a bit closer, but not significantly so.
What about comparing it to the Moon’s average perigee distance, which is ~364,000km. So this “Supermoon” will be ~2% closer to the Earth than it is most months at perigee. Wow!
So what will this mean to you? Nothing at all. The Moon will be a few percent bigger in the sky, but your eye won’t really be able to tell the difference. It will also be a few percent brighter, but your eye will compensate for this too, so altogether this “Supermoon” will look exactly the same as it always does when it’s full.
As to all of those soothsayers claiming that there will be earthquakes and tidal waves. There very well might be, but they’ll be nothing at all to do with the Moon.
UPDATE: I predict that lots of people will report having seen a huge Moon on or around 19 March
Originally posted on Sky and Telescope by by Kelly Beatty, October 6, 2010
Everyone enjoys a great meteor shower, those special times each year when a profusion of shooting stars zip across the sky. So here's a head's up: all of you should circle October 8th on next year's calendar.
This is the yearly date when Earth plows through a tenuous band of space dust created by Comet Giacobini-Zinner along its orbit. Ordinarily, the Draconid shower (formerly called the Giacobinids) puts on a so-so celestial show, delivering about 20 meteors per hour if you can view them under a moonless, pitch-black sky. That's hardly worth staying up for: after all, from a similarly clear, dark site you'll see six or seven random ("sporadic") meteors per hour.
However, this shower has a Jekyll-and-Hyde personality. In 1933 and 1946 the Draconids dazzled skywatchers with astounding meteor "storms" — delivering shooting stars at rates that briefly topped 10,000 per hour! — because Earth crossed through a particularly dense ribbon of debris shed by the comet in 1900. The shower hasn't put on that kind of performance in the years since, though in 2005 it surged unexpectedly to double or triple the usual rate.
If celestial prognosticators are right, we're in for a treat next year, when Draconid rates could top 600 per hour — that's 10 per minute — under ideal viewing conditions. That surge is in the cards because we'll likely clip the stream of particles ejected in 1900. Odds are that it's still largely intact, even though the comet's 6½-year-long orbit periodically puts it in Jupiter's disruptive vicinity.
At a meeting of planetary scientists now under way in Pasadena, California, meteor dynamicist Jérémie Vaubaillon (IMCEE, France) put forth predictions that he'd calculated with colleagues Mikiya Sato and Jun-ichi Watanabe (NAOJ, Japan). If they're right, next October 8th Earth crosses some cometary debris shed by Comet G-Z between 1873 and 1894, peaking at perhaps 60 meteors per hour centered at 17:09 Universal Time, followed at 19:57 UT by a much stronger, 600-per-hour pulse from the 1900 stream.
The rate is very uncertain, Vaubaillon admits, because there's no way to know whether those earlier streams are still densely packed or have been spread thin. Meteor observing wasn't as rigorous back then as it is now. But next year's results should help disentangle which streams are still contributing to the overall rates.
Other meteor specialists are also struggling to come up with firm rates. In 2008 Sato and Watanabe independently estimated a maximum of 500 per hour (at 20:36 UT), whereas NASA researchers Danielle Moser and William Cooke have offered a more optimistic 800 per hour (at 19:11).
These times favor observers in Europe, but don't rush out to book a plane just yet. First, the Draconid shower tends to produce many faint meteors that'll be obliterated by a nearly full Moon that night.
Second, because the shower's radiant is way up near the head of Draco (declination +54°), the best observing sites would likewise be geographically north. But there's a reason that so few people book vacations to Scandinavia in October: "Weather in Northern Europe is not very pretty," notes Canadian meteorologist Jay Anderson. "October can be very nice, but usually it is the time when the winter cloudiness begins to encroach on the daily weather."
Instead, Anderson's cloud-cover map (at right) suggests that the northernmost "good weather" spot is in the Greek Islands. "Santorini — a favorite place of mine — has clear/few/scattered cloud cover 74% of the time. I know where I'd go."
With the Quadrantids meteor shower that has just past yielding around 100 meteors per hour in near-perfect New Moon conditions, which showers of the next two years will give us as good a display?
There are a few regular, dependable showers that can be relied on to put on a good show year after year, given a good Moon phases, so let’s concentrate on those:
The Lyrids peak this year on April 21/22, only three days after the Full Moon, making conditions far from ideal. The ZHR is around 20, but under bright Moon conditions this will be much reduced, so that from the UK you might only see a few Lyrids per hour.
The Perseids peak on 12/13 August 2011 coincides exactly with a Full Moon, making this shower pretty much a write-off in 2011.
The Orionids peak occurs on 21/22 October 2011 just after the last quarter Moon, with the Moon rising a little after midnight, just as the meteor shower radiant is gaining height. Again, far from ideal.
The Leonids peak on 17/18 November occurs during a last quarter Moon, which unfortunately is smack bang in the direction of Leo, and so will obscure many of the Leonids in 2011
The Geminids peak on 13/14 December 2011 will likewise be completely obscured by an almost-full Moon in Gemini.
The Quadrantids peak on 3/4 January 2012 will feature a waxing gibbous Moon which won’t set until 0400.
The Lyrids peak on 21/22 April 2012 is the first major shower peak in 15 months where the Moon is absent, meaning that you should get good views of this shower which has a ZHR of only around 20.
The Perseids peak of 12/13 August 2012 will feature a thin waning crescent moon that’s visible in the sky from midnight, obscuring some of the Perseids.
The Orionids peak on 21/22 October 2012 is pretty much Moon-free from around 2330, as the Moon sets.
The Leonids peak on 17/18 November 2012 will also be Moon free from early evening, and so presents an opportunity to see a few Leonids.
Rounding off this two year run of poor Moon conditions for meteor showers, we end with the Geminids on 13/14 December, coinciding wonderfully with a New Moon on 13 December, meaning conditions will be near perfect.
Total Lunar Eclipses occur when the Moon passes into the shadow of the Earth. That this does not happen every 29 days (the time it takes for the Moon to orbit the Earth) is due to the fact that the Moon’s plane of orbit is not the same as the Earth’s orbital plane around the Sun, and so the Moon passes above or below the cone of the Earth’s shadow most of the time. Every so often, however, these two planes align to create the conditions for a Lunar Eclipse.
When this happens, the Moon will begin to darken in the sky, eventually turning a dark red colour. Unlike a Solar Eclipse, where the Sun’s light is totally blocked out by the Moon, in a Lunar Eclipse the Moon is still visible.
Tuesday’s Lunar Eclipse will begin at 0528 GMT when the Moon enters the Penumbra, the outer part of the Earth’s shadow. This will begin a slight darkening of the Moon, the darkness extending across the Moon’s surface slowly, taking around an hour. At 0632 GMT the Moon will enter the central, darkest part of the Earth’s shadow, form which point it will darken appreciably until, at 0740 it will be in total eclipse, with the full face of the Moon darkened red. This will last until 0854 GMT, at which point the Moon will slowly begin to darken again.
At this point, however, the Moon will have set for some UK observers, or be very low in the sky, on the western horizon, as it is about to set. The time at which it finally sets depends on where you are. In London it sets at 0812 GMT, while in Glasgow (my home town) it sets at 0857 GMT, just minutes after total eclipse ends.
This means that observers in Scotland will have the best view, and the further north you are the more you’ll see.
This lunar eclipse also has the rare distinction of being one where you can see the eclipsed Moon and the Sun in the sky at the same time, as Sun rises around 11 or 12 minutes before the Moon sets, wherever you are in the UK.
Originally posted by Steve Owens Dark Sky Diary http://darkskydiary.wordpress.com/2010/12/19/total-lunar-eclipse-on-the-winter-solstice/
Thursday 25th November, 2010
Get yourself outside tonight if it’s clear, pull up a deck chair, and scan the star clusters, nebulae, and even see another galaxy with your binoculars. They are just perfect for some objects like the larger open clusters. Just aimlessly wandering along the band of the Milky Way is also very enjoyable. If you have binoculars up to 10 x 50 then they’re ideal for the job, portable, and easy to hold. Anything over this size will usually need a tripod. All the objects listed here are at their best in dark skies, ideally with the bright Moon not around.
The Moon tonight…waning gibbous 73% full, rising in NE at 7.53 pm, and setting in NW at 11.36 am (GMT) (26th)
The Sword of Orion, and M42
Rising in the east tonight is the impressive constellation of Orion The Hunter, a sure sign of winter. It’s a striking constellation with the unmistakable, straight line of the three stars of Orion’s belt. Now look below the belt and you’ll see Orion’s Sword. To your naked eye it looks like a line of three fuzzy stars that hang down from the belt, resembling a sword. But when you look through your binos you will see that this is actually a group of star clusters, not individual stars. Notice how the middle cluster glows, especially with averted vision. What you are looking at is the famous, and probably most photographed deep sky object ever, the Orion Nebula or M42. This object is a huge and complex region of gas clouds, around 14 light years across. This place at 1,500 light years away is a vast stellar nursery, but it’s just one small part of an even larger region of gas that spans nearly the entire constellation. New stars, solar systems in formation, and even freely floating planets have all been observed in the Orion Nebula.
Tonight the Orion Nebula rises in the east at 8.01 pm, climbs highest in the south at 1.33 am (GMT), and sets in the west after sunrise.
The Orion Nebula can even be seen with the naked eye under very good skies, it is a magnitude 4.0 object
How long will it be around for? The Orion Nebula is in a winter constellation. So it will slowly and gradually move across the sky eventually sinking into the west by the end of March, when it will make way for the spring constellations rising in the east.
The Pleiades, or Seven Sisters
Rising in the north east tonight in the constellation Taurus is the one open cluster that lots of people can name and recognise, the Seven Sisters, The Pleiades, or M45. It lies between Perseus and Orion, and to the east of Auriga. You can easily see it naked eye, as a large fuzzy patch of stars. M45 is a close open cluster at just 440 light years away, it’s one of the nearest and so appears large in the sky. The stars in the cluster are also very young at only around 150 million years, and the brightest ones you can see are also the very youngest and hottest. The “Seven Sisters” cluster actually contains up to 1,400 members.
This attractive open star cluster fits nicely into your binoculars field of view, providing a very satisfying sight especially in dark skies with the Moon absent.
Tonight the Pleiades Cluster rises in the north east at 3.14 pm, it gets to its highest point in the south at 11.24 pm (GMT), and sets in the north west after sunrise.
The Pleiades Cluster is at magnitude 1.6
How long will it be around for? The Pleiades too will be visible in the sky with the Orion Nebula until around the end of March.
The Andromeda Galaxy, M31
High in the eastern sky tonight is the famous Andromeda Galaxy, or M31. It is a huge spiral galaxy 2.5 million light years away, with up to one trillion stars, and a diameter of up to 220,000 light years…more than twice the size of our Milky Way. You can even see Andromeda naked eye as a fuzzy glow, and there are two main ways to find this island universe in the sky. One is to locate the large square of Pegasus with its four stars marking each corner. You’ll find Pegasus to the east of Perseus, and Cassiopeia. The star at the upper left of the square is called Sirrah (or Alpheratz), look to the left of Sirrah and you’ll see three stars in a line, a dimmer star and two bright stars. The first bright star is Mirach. Now look above Mirach and you’ll see a dimmer star, look about the same distance above again from the dimmer star, and here is located the Andromeda Galaxy (M31). Another way to find M31 it is to use the right hand V of the W of Cassiopeia and imagine a line pointing down, this V points just to the left of Andromeda.
Get your binoculars on M31 and you’ll see the bright core of the galaxy as a small fuzzy blob. But keep studying and use averted vision, and you’ll soon start to make out the fainter shape of the galaxy’s disk extending out from the core. This is an object far outside the Milky Way, an entire ”island universe”. To be seen at its best Andromeda should be observed with the bright Moon absent under dark skies, but it’s still visible even from urban areas.
Tonight the Andromeda Galaxy is rising from in the east after dusk, it’s virtually directly overhead at 8.44 pm (GMT), and eventually sinks low in the north west before sunrise. It is circumpolar, meaning it never sets in northern latitudes.
M31 is at magnitude 3.4
How long will it be around for? The Andromeda Galaxy is actually circumpolar from northern latitudes. It is nicely high in the sky now but will gradually sink to its lowest point just above the horizon in the north in mid March, before starting its rise again.
The Perseus Double Cluster
This cluster is one of my favourites, it looks stunning in a telescope at low power, but binoculars also show it well. The Perseus Double Cluster, NGC 884 and NGC 869, or H and X Persei are actually two seperate open star clusters close to each other in space at around 7,000 light years away. They are only a few million years old, much younger than the Pleaides. To find it I could tell you to find this star, draw a line to that star etc, but the easiest way I have found to locate the Perseus Double is just to look for a fuzzy irregular patch in the band of the Milky Way between Cassiopeia and Perseus, (cluster marked as H+X on Perseus map). Once you see it, get your binos on it and you’ll see two very attractive open clusters of sparkling stars set against the blackness of space. There’s also a nice line of stars that curves away from the upper most cluster, when you see this line of stars you’ll know you have this popular deep sky object in your view.
Tonight you’ll see the Perseus Double Cluster rising from the north east after dark and getting very high in the sky to the east. It is circumpolar meaning it’s always above the horizon and never sets.
This open cluster is a magnitude 4.00 object
How long will it be around for? The Perseus Double Cluster will always be above the horizon, but by April it will have moved over to the north and much lower in the sky.
Jupiter and its moons
Jupiter the giant of the solar system is on show right now, although it is gradually on the wane as far as size and brightness go, having passed full opposition in mid September. But the solar system’s most massive planet and its collection of four main moons can be seen in binoculars. Look to the east after it goes dark and the brightest “star” you see is Jupiter. Put your binoculars on it and although the disk of the planet is small, look carefully and you should see four tiny pinpoints of light around it. These are the moons of Jupiter, Ganymede, Callisto, Io, and Europa. Jupiter’s moon Io is the most volcanic place in the entire solar system, and Europa is covered in ice with an ocean below its frozen crust. One of those four pinpoints of light you see (Europa) has more water on it than all of Earth’s oceans put together, and could even have extraterrestrial life living there. Ganymede is the largest moon in the solar system, even bigger than Mercury, and Callisto could also have a subsurface ocean. The moons shift and change postion over mere hours, so it’s a continually changing scene.
Tonight you’ll see Jupiter quite high in the south east by night fall, it rises highest in the south at 7.33 pm, and sets in the west at 1.08 am. (GMT)
Tonight Jupiter is at magnitude -2.44
How long will it be around for? Jupiter will eventually go out of sight in the setting Sun’s glow by March 2011.
The Beehive Cluster, M44
The Beehive Cluster, Praesepe, M44, or NGC 2632 is a very nice and attractive open star cluster to look at through your binoculars, and does kind of look like a swarm of bees. The Beehive is another open cluster close to Earth, at 577 light years away in the constellation of Cancer. This puts it slightly further away than the Pleaides. M44 rises from the north east, and you’ll see it with your naked eye as a nebulous patch on clear moonless nights. This cluster lies in the fainter constellation of Cancer, in between Leo, and Gemini. The stars that make up the head of Leo the Lion look like a large backwards question mark. You’ll find M44 with your naked eye roughly half way between this “question mark”, and the two twin stars of Castor and pollux in Gemini. The Beehive actually has over 1,000 stars, and is around 600 million years old.
This is really one for the early hours at the moment, as you’ll have to wait until beyond midnight if you want to get a good view of the Beehive Cluster. Tonight it rises from the north east at 8.41 pm (GMT), and climbs to its highest point in the south just before sunrise. Viewing this object gets more convenient in the coming weeks though, as it gradually rises earlier.
This object is at magnitude 3.7
How long will it be around for By April when M42 and the Pleiades will be sinking into the western horizon, the Beehive Cluster will still be nice and high in the sky in the south. But by June it will have disappeared below the north west horizon by nightfall.
The Hyades Cluster
Look to the eastern sky, to the lower left of the Pleaides Cluster, and you’ll see the bright orange star Alderbaran. Alderbaran is an orange giant, and marks the eye of the bull in the constellation Taurus. Alderbaran marks the position of the closest star cluster to Earth, the Hyades. This star grouping of up to 400 members is large and loose, due to its closeness at a mere 151 light years away. This open cluster is so spread out that even your binoculars will just about get all of its stars in their field of view. But this is a really nice collection of suns to gaze at through your binos on crisp dark nights. It contrasts well with bright Alderbaran, although this orange giant is not actually a member of the Hyades Cluster, being much closer to Earth at 65 light years away.
Tonight the Hyades Cluster rises from the east at 4.44 pm, and gets nice and high in the south at 12.38 am (GMT), eventually sinking towards the western horizon before daybreak.
How long will it be around for? The Hyades Cluster will be on view until March/April. At this time it will be close behind the setting Sun, following it into the western horizon.
…also check out Planets To See In The Sky Tonight
The final meteor shower of 2010 is the Geminids, the peak of which falls on the night of the 13/14 December 2010. The Geminids is described by the IMO as “one of the finest, and probably the most reliable, of the major annual showers presently observable”, and this year’s shower is set to put on a good show. (You can read the IMO’s rather technical summary of the 2010 Geminids here: http://www.imo.net/calendar/2010#gem)
The predicted Zenith Hourly Rate (see my previous post about ZHR and what it actually means here) is around 120. Although the peak is predicted to occur around 1100 on 14 December, it should happen some time between 1840 on 13 December and 1600 on 14 December 2010. The best time for the peak to occur for stargazers in the UK would be between 0030 and 0600 on 14 December, after the Moon sets but before twilight begins.
The radiant for this shower is actually quite favourable, and if you wait till the Moon sets at around 0030 on 14 December then the only light pollution limiting your view will be man-made. If you observe before the Moon sets then you will lose a few of the fainter Geminids in its glow, but it’s only a first quarter moon, and so will only really have an impact if you’re observing from very dark skies.
Let’s use the equation relating ZHR to actual observations of meteors to work out how many you might see:
Actual Hourly Rate = (ZHR x sin(h))/((1/(1-k)) x 2^(6.5-m)) where
h = the height of the radiant above the horizon
k = fraction of the sky covered in cloud
m = limiting magnitude
In the case of the 2010 Geminids, if observed from the UK, h = 45 degrees. Let’s assume you have clear skies (haha) with k = 0.
The number of Geminids you can expect to see from a variety of observing sites is as follows:
For very light polluted sites, such as city centres m = 3, and therefore you can expect to see only around 8 meteors per hour.
In suburban skies near a city or town centre m = 4, and you’ll see around 15 meteors per hour.
In rural skies where m = 5, you’ll see 30 meteors per hour.
Under very dark skies, where m = 6.5 (i.e. where there is no or negligible effect of light pollution, like in Galloway Forest Dark Sky Park) you’ll see up to 85 meteors per hour, once the Moon sets. A first quarter moon will impose a limiting magnitude, even at a very dark site, of around 6, in which case you’ll see a slightly reduced 60 meteors per hour.
Remember, all of these numbers assume perfectly clear skies. If half your sky is cloudy, cut these numbers in half!
How many Geminid meteors will I see?
|Where are you observing from?||Limiting magnitude||Number of Geminids per hour|
|A very light polluted city centre||3||7 or 8|
|Dark Sky Site||6.5||85 (after the Moon sets at 0030)|
If you fancy a good view of this spectacular meteor shower, then head to Galloway Forest Dark Sky Park, where we have an evening of talks and meteorwatching planned, weather permitting!
Originally posted on and full credit Universe Today
Are you ready to walk into the lion’s cage? Then break out your favorite skywatching gear because the 2010 Leonid meteor shower is underway…
In the pre-dawn hours on the mornings of November 17 and November 18, the offspring of Comet Temple/Tuttle will be flashing through our atmosphere and just taunting you to test your meteor watching skills against bright skies. Although the phat Moon will greatly interfere with fainter meteor trails, don’t let that stop you from enjoying your monring coffee with the sparkling “cubs” that will be shooting out from the constellation of Leo.
Where? For all observers the constellation of Leo is along the ecliptic plane and will be near its peak height during best viewing times. When? Because of the Moon, just a couple of hours before local dawn is the best time to watch. Why? Read on!
Although it has been a couple of years since Temple/Tuttle was at perihelion, don’t forget that meteor showers are wonderfully unpredictable and the Leonids are sure to please with fall rate of around 20 (average) per hour. Who knows what surprises it may bring! Each time the comet swings around our Sun it loses some of its material in the debris trail. Of course, we all know that is the source of a meteor shower, but what we don’t know is just how much debris was shed and where it may lay.
As our Earth passes through the dusty matter, it may encounter a place where the comet let loose with a large amount of its payload – or it may pass through an area where the “comet stuff” is thin. We might even pass through an area which produces an exciting “meteor storm” like the Leonids produced in 1883! For those in the know, the Leonid meteor shower also made a rather incredible appearance in 1866 and 1867 – dumping up to 1000 (not a typo, folks) shooting stars recorded even with a Moon present! It erupted again in 1966 and in 1998 and produced 3000 (yep. 3000!) video recorded meteors during the years of 2001 and 2002. But remember, human eyes may only be able to detect just a few…
And I ain’t lion!
Photo Courtesy of Stardate.org, Texas University