Podcaster: Ralph & Paul
Title : Awesome Astronomy’s April Sky Guide
Organization: Awesome Astronomy
Link : www.awesomeastronomy.com
Description: What to look out, and up, for in April. We start with the constellation of Ursa Major in our beginner’s and young observer’s guide, and end it with a few deep sky challenges for the more advanced amateurs to hunt down. Next up is the moon and our round up of the craters and interesting lunar features you can explore with a small telescope. Mars, Venus, Saturn & Jupiter feature in the planetary round up for Northern Hemisphere observers this month and we finish off with a scan around the constellation Boötes
Bio: Awesome Astronomy is the show for anyone and everyone who has even the slightest interest in astronomy and science.
Join Ralph & Paul at the beginning of each month, for an informative and fun astronomy programme 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 and listeners’ astronomy questions answered.
As both presenters have been accused of being a little skeptical in the past, you can also expect everything to be frivolous but fact-based
Today’s sponsor: This episode of “365 Days of Astronomy” is sponsored by — no one. We still need sponsors for many days in 2014, so please consider sponsoring a day or two. Just click on the “Donate” button on the lower left side of this webpage, or contact us at signup@365daysofastronomy.org.
Transcript:
Paul: April and the King is finally deposed. After Jupiter’s domination of the winter skies we begin spring with a new pretender to the crown in the shape of perhaps Astronomy’s ultimate tease – Mars. Questions of life, the only planet with visible surface detail, unpredictable global dust storms and those ever changing ice caps combine with an orbital period that doesn’t give us an opposition every year and doesn’t give us a close opposition very often.
Ralph: And that’s really a shame because Mars is one of those planets that has so much detail and intrigue to tease out that it can be quite frustrating that it’s not looming as large as the moon in an amateur telescope.
Paul: Yes, and because Mars is about 150 times further away than the moon, it’s always smaller than you remember, but April this year still belongs to the God of War and more on that later. This month we also have a decent meteor shower and, for those listeners in North America, there’s a total lunar eclipse to look forward to and for a lucky few a very rare event.
But we start with this month’s beginner’s guide and we follow that up with a galaxy quest and star-splitting challenge as we tour around the often overlooked constellation of Bootes. But first it’s over to Ralph.
Ralph: Thanks Paul. So for the beginners’ guide this month we’ll take a look at one of the most famous and useful constellations in the sky, Ursa Major or the Great Bear. Famous because it has within it seven stars that are recognisable to almost everyone, young and old. Known in North America as the Big Dipper, in Asia as the Northern Ladle and in Europe as the Plough or the Saucepan, it’s not hard to see why it gained these colloquial names. And it’s useful because it serves to locate so many points in the sky:
The two stars at the opposite end of the plough to the handle, Merak and Dubhe, are known as the Pointer Stars because they point to the Pole Star that sits practically at true north. And this will be the first port of call for anyone using an equatorial mount, so they can get a polar alignment before they begin observing. Following the curve of the handle of the plough away from the saucepan’s bowl traces an arc to the bright star Arcturus and the constellation Bootes. Following that arc further, takes us to the star Spica and the constellation of Virgo.
Ursa Major is a far larger constellation than just the Plough asterism but we’ll stick with these seven stars in this guide as it’s all we need to make our way around it.
And we’ll start with the easiest binary star of them all to split. For this you need look no further than the star in the kink of the handle Mizar. Even in the most light polluted skies, those with good vision, will be able to see it as two distinct stars, Mizar & Alcor, with the naked eye.
But Ursa Major is probably just as famous for the galaxies it contains. And as they’re all in our local supercluster, they’re close enough to be simply stunning in the eyepiece and can be seen in dark skies relatively easily with even a 4” scope – although M101, the Pinwheel Galaxy, does have a low surface brightness, you may have to use averted vision to pick that one out unless you use a 6” scope or larger.
But it’s well worth looking for M101 as it’s a grand spiral galaxy like our own and it’s face-on so we get to see it’s lovely spiral arms. Draw a line between Mizar and Alkaid (the stars at the end of the Plough’s handle). If it were an equilateral triangle with the third corner pointing to the left, that corner is where M101 sits.
Now draw a line between Alkaid and Cor Caroli in the constellation Canes Venatici (to the right of Ursa Major). And about a quarter of the way along that line and roughly half a degree above that point, sits another unique wonder for amateur astronomers, Messier 51, The Whirlpool Galaxy. So named because you see a face-on spiral galaxy devouring another smaller galaxy that strayed too close. It’s visible in a 4” scope but the view through an 8” scope will blow your mind. And where else can you see something as awe inspiring as two galaxies colliding with your own eyes from your own garden?
Now to complete the list of easily viewed galaxies in Ursa Major, move up the Big Dipper to the lower left star in the bowl, Phad or Phecda. Draw a line from that star to the last star in the bowl, Dubhe. Continue that line to the left for the same distance and you get a two for one, because that’s where a slantindicular spiral galaxy, M81, sits within the same low power eyepiece view as the edge-on galaxy, home to the recent supernova, M82. Gravitational interactions between the two galaxies set off rapid star-formation in M82 and, all four of the galaxies I’ve suggested here will merge with our own galaxy in billions of years time.
Paul: now lets turn to the solar system and see what is available for your eyepieces and imaging kit this month.
First off we need to talk about Mars. Finally after a long absence Mars is properly back in our skies and reaches opposition on April 8th. Not the biggest opposition that Mars can provide, that won’t happen until later in the decade but none the less this is Mars at it’s best in a very long time. By a quirk of orbital mechanics, while opposition is on the 8th, meaning the Sun, Earth and Mars line up, Mars and Earth are actually at their closest 6 days later on the 14th. So the period immediately after opposition is going to be the best time.
Now what to look out for on Mars, well sticking with small scope views i will mention four key features to look out for. The first is one of the features that makes mars of such interest- the polar ice caps, little white spot on the top or bottom (depending on your telescope) is a thick chunk of mainly frozen CO2. Now currently the North pole of mars is orientated towards Earth and the polar cap is not particularly extensive as the North of Mars is at the height of summer presently, Northern Martian Summer Solstice was on February 15th.
Next is probably the most obvious feature on the Martian surface and one very clear in even small and medium scopes at opposition Syrtis major. Now the best way to describe this feature is a large dark triangle that points towards the north from the darker region of the south. It is actually a low relief shield volcano and the darkness is basalt. Now the only area that can cause confusion with Syrtis major is the next area to mention, the Chryse Planitia. Now this area itself is a lighter area around the equator between two darker regions that reach out from the north and south. The darker areas are often confused with Syrtis Major. The last feature is the side of mars that does not appear to have much in the way of darker regions and makes mars often appear a uniform pink. This is the region usually referred to as Amazonis. It is a vast area with the volcano Olympus Mons to the north, which is the largest volcano in the solar system and can be seen in large scopes as a faint light patch. I do advise getting hold of a Mars map, there are some great ones on sites such as the British Astronomical Association that will get you started and point you the right way.
Moving onto the other planets we have Venus getting lower in the predawn sky but it will now sit in approximately the same position for the next six months due to the relative orbital motions of Earth and Venus. Saturn sitting in Libra climbs slowly higher and is starting to make it’s way into the late evening sky, finally becoming a decent target, though it is still very low for more northern observers. The rings are particularly well placed at the moment so do take a look. Jupiter in Gemini is still very visible but is beginning the slow retreat towards the sun, so do go out and get a good last look at Jupiter this apparition before the King starts to battle with the evening glow. Mercury, Uranus and Neptune not visible this month.
The moon this month Moon gives us First Quarter on the 7th at 9.31am, Full moon on the 15th at 8.42am, last quarter on the 22nd at 8.51am and we reach new moon on the 29th at 7.14am. This means the deep sky jinkies should aim to get their fix at the beginning and of the months when the skies will be darker. The moon gives us some nice encounters over April and on the 3rd sits in the Hyades Cluster while on the 6th the moon is next to Jupiter in Gemini. The 14th when it is almost full it sits between mars and spica in virgo. saturn 16th gets a visit while antares is nearby on the 18th. Look out for the crescent moon with venus on the 25th and 26th before dawn in what is always a beautiful pairing.
For North American Listeners the moon puts on a real treat for you on the 15th and presents a total lunar eclipse for almost all of North America, the Pacific and the west coast of South America. Listeners in the North east, such as Quebec and much of New England will miss out on the full spectacle though. First contact with the Penumbra will be at 04:53 UT with first contact with the Umbra, which will be the first real noticeable event occurring at 05:58UT. Totality will be between 07:06 UT and 08:24UT with the moon finally leaving the earth’s shadow at 10:37UT. Please remember to convert to your local time from these UT figures. Especially for those of us in other parts of the world, do please share your images and observations of this fantastic event on our facebook, twitter and flickr groups.
Fortunately for the meteor watchers the moon is moving to last quarter when the Lyrids shower belonging to comet Thatcher reaches it’s peak on the night of the 21st-22nd. It has a zenithal hourly rate of around 20 an hour so is a reasonable shower and worth the effort to spend some time looking for. It will be best late evening before the moon rises.
A last very rare solar system event to mention happens on March 20th and this is one for a select few on a 45 mile wide line from new york cty though Oswego in New York State and off into North west Ontario. The lucky observers in the centre of this line will see the star regulus vanish for up to 14 seconds as asteroid Erigone 163 occults drawing a thin shadow over the earth. This event will run from 05:53UT until 06:22UT, approximately 2am EDT. Don’t miss that if you can!
For the deep sky challenge this month we are going to look at the Constellation Bootes and give you a multiple star splitting challenge, a Globular cluster and a couple of nice galaxies.
Bootes is a simple constellation found simply by following the handle stars of the plough and you will find they roughly point to the bright star Arcturus, this is a bright star of magnitude -0.04 and sits at the bottom of bootes kite shape. Above Arcturus towards Hercules you should find the five stars that make a good pentagon.
There are several good multiple star targets in Bootes and this month we are going to point you in the direction of five.
The first is Epsilon Bootes or Izar. This is a triple system with the primary being a yellowy-orange magnitude 2.5 giant star, the secondary is magnitude 4.6 and a blue main-sequence star while the tertiary a magnitude 12.0. The primary and secondary are separated by 2.9 arc seconds.
Next we have Mu Bootes which is another triple system with the primary appearing as a magnitude 4.3 blue-white star. The secondary initially appears as a magnitude 6.5, but is actually a close double star itself with a primary of magnitude 7.0 and a secondary of magnitude 7.6.
Our third multiple for you to split is Zeta Bootes. Now this is a physical binary combined with an optical companion giving the appearance of a triple system. The physical binary are separated by 1 arc second and are mag 4.5 and 4.6. Meanwhile the optical companion is separated by 99 arcseconds and is mag 10.9.
Fourth appropriately is a four star system for you to split, Xi Bootes. This has a primary yellow star of magnitude 4.7 and a secondary orange star of magnitude 6.8 with a separation of 6.7 arcseconds. The tertiary is a magnitude 12.6 star and the quaternary is a scope straining magnitude 13.6. This group is actually close to earth, just 22 light years away.
Last is a binocular multiple, Nu Bootes which has a primary that is an orange giant of magnitude 5.0 and a secondary white star of magnitude 5.0.
Splitting multiples is a test of scope prowess and skill with the eyepiece, so good luck and good hunting.
Before leaving Bootes it is also worth mentioning two further DSOs for those that are not of a multiple persuasion. The first is a globular cluster, NGC5466. this is one of the most difficult globs to observe and appears as quite a loose grouping for a glob. It has a low surface brightness of 9.1 and requires good skies and larger apertures. Two interesting and reasonably bright galaxies to hunt down are NGC5248 or Caldwell 45, a nice spiral that is actually a member of the virgo cluster. There is also NGC5676 to look out for, another spiral famous for its fragmented and chaotic look.
Ralph: Don’t forget you can also download our full Awesome Astronomy podcast for an hour long show full of news, views, answers to your questions and interviews from around the astronomy world. It is available on the 1st of every month on iTunes and as an RSS feed, as well as on our YouTube channel.
Paul: You can also find tutorials, blogs, links to the show and sky guide on our website at www.awesomeastronomy.com good luck and we wish you clear skies.
End of podcast:
365 Days of Astronomy
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