August 2009 – and all the planets have shown up for the party!

That’s the good news – the bad news is the “party” is an all-nighter. That is, if you really want too see all the planets – and maybe little, demoted Pluto as well – you need to start at dusk and stay at your task well into the wee hours of morning.  For Pluto, you will also need a powerful telescope and better charts than I’ll provide here, but the others can all be seen with the naked eye or binoculars.

But what I like about this situation is it makes it easy – even for those of us using nothing but the naked eye, which is really the focus of this web site  – to  see most planets on a single night and to get a sense of how their position in the sky relates to our position in the solar system and where we all are on our annual journey around  the Sun.

Astronomy is always about two realities – the reality we see and the reality we know. The trick is learning to merge these two so that when you see something in the night sky, you are familiar enough with what is really going on that what you see makes perfect sense, given what you know.

The best example of this is provided by the two major planets this month – Jupiter and Saturn. The chart above shows the reality we know. It shows where all the planets are at the start of August if you could get  above the plane of the solar system and look down at them. Study it. This is from the online orrery at “Solar System Live.” (http://www.fourmilab.ch/solar/)  I drew the bar across it to represents our horizon – the line between night and day –  and the arrows show the direction the bar is moving as night progresses. To the left this shows how, from our perspective, things are setting in the west – and to the right, how they are rising in the east.

Notice that in this view Saturn is near our western horizon and Jupiter near the eastern horizon. That’s the situation right around sunset. But the sky is too bright then for us to see even bright planets. We have to wait about 45 minutes. At that point, Saturn will look like a first magnitude star about 12 degrees above the horizon almost due west – azimuth 266 degrees – in the early part of the month.

Switch to the east and Jupiter is not so shy. It is at magnitude -2.8 (nothing gets brighter than this except Venus, the Moon, and the Sun), but it is still hugging the horizon. Chances are it is too close for you to see. Give it another 45 minutes – 90 minutes after sunset – and it will be about nine degrees above the horizon a bit south of east. For my latitude – 42 degrees north – it will be at azimuth 118. But the exact position isn’t too critical, since it is so bright and there’s nothing in that general vicinity at this time that will compete with it.

This will change slowly as the month goes on – that is, Saturn gets closer to the horizon at sunset each night and Jupiter rises earlier, until on August 14th Jupiter is rising in the east as the Sun is setting in the west.

Did you notice on the solar system view that Mercury is right over there near the western horizon as well? It is, but this happens to be a fairly poor showing for what is always an elusive planet to catch. Sky and Telescope gives this instruction: “Observers near 40° north can look for it 5° above the western horizon a half hour after sunset from August 6 to August 18th.” Yep – and it will be near magnitude “0” – but you will need a very clear western horizon to see it, and I suggest you search for it with binoculars.  Earlier in the month is better than later for both Saturn and Mercury. As the month goes on Saturn not only gets  closer to the horizon, but also closer to Mercury – and this will make  both very difficult to see. By August 17 the two planets are just 3 degrees apart, but then Mercury is only 2 degrees above the horizon and Saturn about 6.

Much easier to find are our two morning planets, Venus and Mars. Both can be spotted, without strain, with the naked eye. But Venus is by far the easiest. It is a brilliant  magnitude -4 – brighter even than Jupiter, which by this time is well over in the southwest, and should be easy to see low in the east northeast by 3:30 am. By the end of the month you’ll have to wait until about 4:30 am for it to be easily seen – but that’s still two and half hours ahead of sunrise.

Mars is a bit more of a problem, though it rises well ahead of Venus. At 3 am August 1 it is a first magnitude “star” about 7 degrees to the north of Aldebaran, also first magnitude,  and both are roughly 15 degrees above the horizon, a bit north of east. Because Aldebaran is a very red star, it will be interesting to compare it with the “red” planet, but it’s best to wait another hour to do this so both are higher in the sky and not as affected by the atmosphere, which tends to make every bright object colorful.

By the end of the month Mars is higher at 3 am, but Aldebaran is higher still. Mars will form an interesting triangle, though, with Aldebaran and another very red star, Betelgeuse. In fact, if you are up at that hour you get a preview of the early winter sky with the bright constellations of Auriga, Taurus, Gemni, and Orion coming into view, and Mars in the middle of them as our chart shows.

Mars early in th emorning at the end of themonth. Click for larger version. (This chart uses a screen shot from Starry Nights software which I have then annotated.)

Returning to the evening sky, this remains a good year to track down Neptune and Uranus with binoculars. Both are relatively easy to find, but offer special challenges.

Notice on the solar system chart how Neptune is roughly in line with Jupiter as we view both from Earth. On August first a careful study of the Jupiter region with binoculars around 10 pm will reveal Neptune at about magnitude 8 and only two degrees to the north (left) – but finding it can be tricky.  Try putting Jupiter in the right-hand edge of your field – or even move your binoculars so Jupiter just drops out of the right hand edge. That way the glare from it won’t interfere with your view.  At that point Neptune should be pretty close to the center of your field of view. There are several stars nearby and both Neptune and Jupiter are changing position as the month goes on. Here’s a chart for August 1.

Neptune and Jupiter at the first of August, 2009. (Clickfor larger view.) (This chart uses a screen shot from Starry Nights software which I have then annotated.)

By the middle of the month, they have drifted a bit farther apart, and there’s a row of sixth magnitude stars in a gentle arc between them. If you compare the first chart and this second one you will see these stars and how the position of the planets change relative to them.

Neptune and Jupiter near the middle of August, 2009. (This chart uses a screen shot from Starry Nights software which I have then annotated.)

By the end of the month these same stars are closer to Neptune and the gap between Neptune and Jupiter is almost five degrees. That means they both probably fit in the same binocular field, but just barely.

If you look at the horizon line on our solar system chart – especially the eastern one – and note the direction it is moving, then you can see how our view will change during the night. As Jupiter and Neptune get higher we eventually get to a point where Uranus comes into view, then, well after midnight, Mars and Venus put in an appearance.

Uranus is easier to see than Neptune because it’s significantly brighter – about magnitude 6.  We also get a special break this month, for Uranus will form a wide “double star” with 20 Piscium, a star that is just a tad brighter than the planet. But this makes it easy to identify.  Here’s my way to locate it. First, trace out a few asterism in the sky south of east. (The following chart is for 11 pm EDT, August 1, at 40° North – but should serve as a general guide for almost any location.)

This charts helps you locate thegeneral area inw hich to find Uranus. Click forlarger version. (This chart uses a screen shot from Starry Nights software which I have then annotated.)

Next, you want to zero in on the Circlet of Pisces and an unnamed trapezoid below it.

Tracking down Uranus with binoculars. (This chart uses a screen shot from Starry Nights software which I have then annotated.)

The Circlet will not fit quite in the typical binocular field of view. The trapezoid should fit and maybe Uranus at the same time – but the way I find Uranus is to find the trapezoid in my binoculars, then move up so that only its top two stars are visible in the bottom of my field of view. Now up and to the right are two almost identical stars – the higher one is Uranus. It is about half a degree above 20 Piscium, a star that is just a tad brighter, though you will be challenged to tell the difference.  (The charts show only those stars you can expect to see with your binoculars – but depending on the binoculars and conditions, you may not see all of these stars.) Uranus is on the brighter side of magnitude 6 and at this point, at least 10 degrees above the horizon. Waiting until later in the night – or later in the month, this will only get easier as Uranus will get higher.  But as the month goes on it will pull away a little from 20 Piscium. By August 30 they are a degree apart and instead of Uranus being directly above 20 Piscium, it will have moved above and to the right – westward.

And Pluto? I wouldn’t try to hunt it down even with my 15-inch telescope.  Although it is relatively high in the south once it gets really dark, it is much too faint to see in anything except large amateur scopes. And to make matters worse, it has lots of competition, for it is above the Teapot in the middle of the Milky Way, and at magnitude 14, just a faint, faint dot among many, many other faint dots. Better to spend your time exploring the Milky Way itself. See: August Guideposts: Asterisms guide you along the Milky Way.

This is the general area within which you can find Pluto this month. But theplanet is faint and buried with the faint stars of the Milky Way. (This chart uses a screen shot from Starry Nights software.)