Podcaster: Ralph & Paul
Title : Awesome Astronomy’s September Sky Guide
Organization: Awesome Astronomy
Link : www.awesomeastronomy.com
Description: What to look out, and up, for in September.
This month we take a look at the constellation of Queen Cassiopeia for the beginners guide – we have the beautiful Owl Cluster; NGC 7788 or Caroline’s Rose, discovered by Caroline Herschel; and NGC 185, a dwarf elliptical galaxy discovered by Caroline’s brother, William Herschel.
Next we round up the planets that are visible in August: Uranus, Neptune, Saturn & Mercury. We look at the month’s two lunar treats: a series of conjunctions between the moon and bright star Aldebaran and a perfect lunar eclipse for many listeners on the 28th September. Comet Churyumov Gerasimenko will be visible this month near the Beehive Cluster in Cancer (sadly we won’t see ESA’s Rosetta spacecraft orbiting it!) and our deep sky challenge delves into the constellatinos of Sagitta the Arrow and Vulpecula the Fox for a tour of clusters and a planetary nebula.
For those in the Southern Hemisphere, 365 Days of Astronomy also play Alice Enevoldsen’s What’s Up Tonight, Southern Skies Edition each month.
Bio: Awesome Astronomy is the show for anyone and everyone who has even the slightest interest in astronomy and science.
Join Ralph & Paul twice each month, for informative and fun astronomy programs telling you what to look out (and up) for every month. You can be guaranteed a passion for astronomy, simple explanations of complex and fundamental topics, space and science news, absorbing interviews with astronomers who make the news and listeners’ astronomy questions answered
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Transcript:
Paul: September. Once more the roads are clogged with overprotective parents driving their spawn to school, the supermarkets begin to stock their Christmas lines and the skies begin to get dark at a civilised hour. With equinox on the 23rd all is finally right with the world by the end of the month as we have nights longer than the day. Exactly as it should be. We have a great month of astronomy ahead of us opening a season that has it’s fair share of highlights, not least of which is the total lunar eclipse. But before we look at how to catch that wonder of the skies we have to see what Ralph has lined up for us in his beginner’s guide.
Ralph: This month for the beginners and young astronomers, I’m going to run through the delights on offer in the constellation represented by Queen Cassiopeia or Cassiopeia if you prefer. A constellation that’s technically visible all year round as it circles close to the Pole Star, but this month, Cassiopeia’s already well above the horizon as soon as it’s dark and sits not far from the zenith by 2am.
So, to find Cassiopeia, look north east for the very obvious W-shape of 5 bright stars. If you scan a telescope or a pair of binoculars through the confines of the W, you’ll see lots of interesting stars and star clusters of all colours. This makes Cassiopeia particularly good for binocular observing.
First find the two stars that form the right hand line in the W-shape: Shedir (at the bottom of the stroke) and Caph at the top. Look for the next brightest star to the right of Caph – about two outstretched fingers’ width away, called rho cassiopeiae, and less than a degree away and easily within the same field of view of a low power eyepiece or a pair of binoculars sits NGC 7789. Also known as Caroline’s Rose, see if you can make out the rose shape caused by dark voids between the stars. These stars were all formed at the same time but the larger ones have exhausted their hydrogen, bloated and therefore provide some contrasting colour to the rose.
Next, draw a line from the top left hand star, epsilon Cassiopeiae, to the left hand bottom star in the W shape, Ruchbar, if you follow this line for a further 2 degrees right of Ruchbar, you’ll notice two bright stars that look like eyes (giving rise to its more common name, the Owl cluster). Centre these two stars in your eyepiece and the body and wings of the owl should emerge. Some people call it the ET cluster after Spielberg’s wrinkled and diminutive alien – but I’ve yet to see it anything other than an owl.
Now, finally, I have a bit more of a challenge, but one that’s worth it
Draw a line between Shedar, the bottom right hand star in the W shape, and the Andromeda galaxy – which sits an out streched hand’s width to the east of Shedar and will be visible as a large smudge to the naked eye in dark skies. Roughly half way along this line is NGC 185 a dwarf elliptical galaxy of similar apparent size to the two previous clusters. At magnitude 10, it’s quite a challenge and it’ll only appear as an oval smudge in the eyepiece, but what you’re seeing here is a satellite galaxy of the Andromeda Galaxy which has a feeding black hole in its centre. Being beyond our own Milky Way, this galaxy is 285 times further away than the star clusters I’ve just suggested so you really are peering way out into the cosmos.
Paul: Well let’s turn to the Solar System and see what is going on in our neck of the cosmos.
After a summer planetary drought we are suddenly in a position to see all of planets and for many of them in pretty spectacular fashion. The first of the month sees Neptune at opposition, so this is your best chance to grab a look at the furthest planet currently sitting in the southern part of Aquarius. Unless you are equipped with a large scope there is not a lot to see beyond a small blue disc and to see Neptune’s large moon Triton will need a scope in the order of 300 mm or more. But it is worth a look, it will appear as a planet in even a small scope and you will know that you are seeing the furthest world from our Sun.
Uranus is not yet at opposition but Herschel’s planet is improving all the time and is now at naked eye visibility and easily located in binoculars. It’s a nice green/blue disc in even a small scope but details and those elusive moons will need some pretty large aperture to find. Currently Uranus is easily located in Pisces between epsilon and mu piscium along the line of the constellation.
Saturn is still with us in the evening, though is now falling into the glare of the evening sun and with the low altitude the ring world has this apparition the view is not perfect, but always a good way to start an evenings observation.
It is the morning that is really the planetary highlight and this is a sight that is just going to improve through the whole of autumn so it is worth some early mornings. We have just passed a major conjunction with Venus and Jupiter in the early summer but now we will be getting a repeat performance before dawn and this time it is joined by Mars. The closest these planets will be will come later in the season but throughout September you will see the three brightest planets slowly converging as they pull away from the Sun. Added to this will be Mercury that while not in conjunction as such will eventually be part of the same morning view, though in September not for the more northerly observers such as those in the UK.
The moon is the real highlight of the month with two major events both long awaited. The first is on the morning of the 5th of September when the Moon occults the bright star aldebaran. This happens less frequently than you would imagine and because of the quirks of the lunar orbit aldeberan occultations happen every 18 and half years in batches. This occultation is the first of this new run of 49 that will take place over the next three years. After that the next run will be in 2033. This is an early morning treat and will begin just before 5 am UT, that’s just before 6 UK time. The star emerges for UK observers shortly after 6 UT or 7am so will be a difficult observation given the bright sky, but can be done.
The real highlight of the whole month is of course the total lunar eclipse on the night of the 28th-29th which will be seen by countries bordering the Atlantic and partially seen right across the Americas, Africa and across asia as far as eastern India. For Western Europeans, West Africa, the Eastern side of North America and all of Southern America this will be a perfect chance to see a full total lunar eclipse. It is a late one and a long one so don’t plan on much sleep. P1 where the moon begins to touch the Earth’s outer shadow or Penumbra is at 11 minutes past midnight UT, that’s 11 past 1 in the UK. U1 when the moon starts to pass into the darker inner shadow or Umbra is as 1.07 UT with greatest eclipse at 2.47 UT. That’s right an hour and forty minutes. The moon doesn’t achieve U4 where it leaves the Umbra until 4.27 UT and finally passes out of the shadow P4 at 5.22 UT, giving a total eclipse time of 5 hours and 11 minutes. Look out for the varying colours that a total eclipse presents the blood red of totality being common but also look for subtle shades of blue and yellow throughout the event.
The moons phases this month begin just past full on the first and move to last quarter on the 5th, new moon follows on the 13th and of course with the eclipse full moon is on the morning of the 28th.
Comet hunters might want to try and catch Churymov Gerasimenko this month as it passes through cancer in the morning hours, passing close to M44 the beehive cluster around the 17th-18th. Magnitude is still uncertain and of course this will be a light sky and quite low down. Things should improve as the month goes on, but a difficult observation. Aperture, patience and some luck required.
For our deep sky challenge this month you are getting a two for one deal in the shape of the constellations of Sagitta and Vulpecula, the arrow and the little fox.
Sagitta, the arrow fired by nearby Hercules to kill Aquila the eagle who had a bit of a fetish for Prometheus’ liver is the third smallest constellation and and sits within the summer triangle. As you move up from Altair at the base of the triangle towards Deneb in Cygnus look for a small line of mag three stars with a distinctive triangle to the right, essentially making it look like an arrow. It is not an impressive constellation but within it is the often overlooked M71. Not a messier often mentioned in conversation but a great target and one that until the 1970s was classified wrongly as an open cluster, more modern techniques and greater understanding saw M71 reclassified as loose globular cluster. It is young for the type (hence the earlier confusion) and is only 12000 light years away and 27 light years across. It lacks the typical dense core of a glob and it makes for an interesting comparison with that nearby archetype M13
Vulpecula is the little fox surfing the arrow. Moving a little further towards cygnus is the very indistinct collection of mag 4 stars that to the eyes makes anything but a fox. The constellation stretches across the centre of the summer triangle and is larger than the scattering of it’s brightest stars suggest. This is a cunning fox and hidden inside are two gems of the sky NGC6853 or M27 and Collinder 399 or Brocchis cluster. M27 better known as the dumb bell nebula is a planetary nebula about 1300 light years away and in a good sky is visible in binoculars at 8 arcminutes across and magnitude 7.5. That said M27 is an object that seems particularly vulnerable to light pollution and I have found it be a sensitive little soul when it comes to sky conditions. It is an impressive object and when seen set against the dense star field of the milky way it is one of the skies real treasures. Interestingly it contains the largest known white dwarf at its centre.
Brocchis cluster is a chance grouping of stars that form one of those surprising and unnatural asterisms, in this case the shape of a coat hanger. It can be seen in the centre of the summer triangle with the naked eye as an unresolved patch of light, often glimpsed with averted vision. Looking through binoculars or a telescope will reveal the coat hanger arrangement.
There are a range of clusters in this part of the sky and a couple that are definitely worth tracking down. NGC6834 is an open cluster of mag 7.8 And have a look at star 20 Vulpeculae. Next to it are clusters NGC 6882 and 6885. But this is a bone of contention amongst astronomers and a possible error in the NGC. Most claim to be able to only see one cluster… So happy hunting and I wish you clear skies.
End of podcast:
365 Days of Astronomy
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