Podcaster: Ralph & Paul
Title : Awesome Astronomy’s August Sky Guide
Organization: Awesome Astronomy
Link : www.awesomeastronomy.com
Description: What to look out, and up, for in August.
This month we take a look at the constellation of Cepheus the King for the beginners guide – we have the first galactic tape measure: the original Cepheid Variable, a red supergiant star: Hershel’s Garnet Star and the Elephant’s Trunk Nebula.
Next we round up the planets that are visible in August: Jupiter, Saturn, Uranus & Neptune. We look at the month’s moon phases and enjoy a supermoon (or perigee-syzergy) on the 29th. August treats us to the best meteor shower of the year – the Perseids – falling on the 12th August with no moon to dampen the show. We also look forward to rare comet conjunction occurs in August with Rosetta’s Comet 67/P and comet 141/P sharing the same field of view in telescopes. For our deep sky challenge we look at the constellation of Aquarius for a tour of globular clusters and planetary nebulae.
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: August. Break out the bunting and party poppers and annoy all those around you by celebrating the ever shortening days and lengthening nights. For those in the northern latitudes we’ve passed the two month exile where we never get beyond astronomical twilight and finally we get a true dark sky again. Despite this, August still has a reputation for not being much of a month for astronomy and many out there will be eyeing september and dreaming of early autumn, but August is a month of darkening skies, warm evenings, spectacular sights and of course that meteor shower. So kick back and let us guide you through the end of summer. First up is our beginner’s guide with Ralph.
Ralph: Thanks Paul, for the beginners and young astronomers this month we’re going to look at a constellation that’s a bit trickier than usual and one that, for that reason, often gets overlooked: Cepheus the King.
Overlooked, perhaps also, because it doesn’t contain any nice bright Messier objects and doesn’t stand out as a bright shape in the way Ursa Major or Cygnus do. It does have a nice simple house-shape to help you locate it though.
If you can wait until around 1am this month, it should be directly overhead. It also sits directly above the W-shape of Cassiopeia. You should see a faint square of stars, with Alderamin being the brightest of the quartet, and another star, called Errai, forming an apex on the house-shaped constellation
While not easy to pick out compared to many of the other glowing constellations at this time of year, Cepheus has historical significance, because it gave its name to a type of star that pulsates with a predictable brightness that allows us to accurately judge distances across the galaxy and to other galaxies as well. A study of the star Delta Cephei in 1784 by John Goodricke gave the name Cepheid Variables to these kind of stars. So we’ll start the beginner’s guide by pointing the way to the star that became our original galactic tape measure.
Find the W shape of bright stars in Cassiopeia and draw a line from the middle star in the W all the way to bright star Vega. Exactly half way along that line is a white magnitude 4 star just to the left of the bottom of the house shape. That’s our cosmic yard stick, Delta Cephei.
Next we’re looking for a star of similar brightness. Find the 2 stars that form the base of the house shape, Alderamin and zeta Cephei. About an outstretched finger’s width, just below the half way point sits mu Cephei. This is a monster star, so large that it’s radius would swallow up Jupiter if it were in our solar system. One of the largest stars in the entire galaxy, a telescope will show this as very red, hence the name it gained after William Herschel’s observations, Herschel’s Garnet Star.
Finally, move down the same distance from the Garnet Star – about an outstretched finger’s width – and you’ll find a rather loose cluster of stars, if you have dark skies or an Oiii filter you might pick out a smudge of nebulosity in this star forming region of illuminated gas called ic1396. If you can take a long exposure camera image in dark skies, you’ll reveal this to be the beautiful Elephant Trunk Nebula.
Paul: Bit of a quiet month as far as the planets are concerned, we have recent darlings of the evening sky Jupiter and Venus, along with Mercury and Mars all hiding in the Sun’s glare, and while you may grab glimpses of some of them just after sunset or just before sunrise don’t hold your breath. This means that the planetary side is being held by the three outer most planets. Saturn, still nice and bright on the evening sky in the South West, but frustratingly low, especially for the urban observers is definitely worth the effort with the rings very well presented this apparition.
Neptune is rising in Aquarius well before midnight and is slowly increasing in brightness and apparent diameter as we approach opposition on the 1st September. Not great amounts to see unless you are fortunate enough to own a very large aperture scope but still worth the hunt to glimpse the solar systems furthest world.
Uranus, in Pisces is not at opposition until the 12th of October but it is closer and as we move into the darker skies of the end of summer it should start to become naked eye visible and certainly found easily in binoculars.
The moon this month begins a shade past full moon which occurred on the 31st of July. We reach last quarter on 7th move to new moon on the 14th reach first quarter on the 23rd and return to full moon on the 29th. For those interested the 29th full moon is a super moon or to give it it’s more scientific name perigee-syzygy of the Earth-Moon-Sun system, or the point where the closest point on the moons orbit coincides with full of new moon. You really won’t see a difference, at best the moon will be about 10-15% bigger which really isn’t perceptible to the human eye, imagers might have more luck comparing images with other new moons to see the difference.
The highlight of August, and perhaps the whole summer in astronomy is the perseid meteor shower. This is the debris from the comet Swift-Tutle and peaks on the night of the 12th of August. The moon will be a very thin crescent rising at 3.43am so will have little effect on the shower so it should be a vintage year. ZHR is typically around 60 an hour, so grab yourself a good dark vantage point and sit back and enjoy the show.
Okay. So for our deep sky challenge in August we’re moving into the constellation Aquarius, which is a rather indistinct constellation with no star above magnitude 2. It’s best found by looking for pegasus and the circlet of pisces below and then turning to the area of sky below and to the right.
Now Aquarius may be lacking in bright stars but it makes up for this with some fantastic deep sky objects and this month we have three messier objects and two great planetary nebulae for you to hunt down.
The easiest of the objects to locate are the three Messiers, M2 and 72 are both globular clusters while M73 is probably best described as a mistake. M2 is a bright rich glob that can be found 5 degrees north of star beta aquarii. With a magnitude of 6.3 it is naked eye visible in a good sky and is one of the largest globs at 175 light years across. M72 is a less dense and far more distant cluster, at almost twice the distance from us as M2. Magnitude 9.3 it needs larger apertures to tease out the individual stars. It is found below star epsilon aquarii, the star called Albali which is the star on the right of the main constellation.
Very close to M72 is M73, included by Messier and described as a cluster of four stars with some nebulosity. Nobody has ever seen the nebulosity since and centuries of debate was resolved recently when it was shown that the stars of M73 were in fact an unrelated asterism. Still an interesting object if only for the curiosity value. Have fun trying to work out which stars Messier was looking at.
NGC7293 or the Helix Nebula is the closest planetary nebula to earth, somewhere between 650-700 light years away. This also makes it the largest but because of this it has a low apparent surface brightness and while nominally magnitude 7.3 the Helix is a difficult and faint challenge. look for star 59 aquarii in the southern part of the constellation away from the main constellation.
NGC7009 is the Saturn nebula, a planetary 3000 light years away that appears to have two small protrusions each side giving it the appearance of saturn in a small scope. this can be found not far from M72 and the mysterious M73, you may find 7009 while you are hunting for the mistake that is 73. As with those two messier objects the star to begin hopping from is Albali.
Well that is all from this months sky guide and it only remains for me to wish you clear skies and happy hunting.
End of podcast:
365 Days of Astronomy
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