Events for September 2010 – center stage for the Georgian Star as introduced by Jupiter!

• Georgian Star
• Equinox, Harvest Moon, Belt of Venus
• Fleeting Mercury
• Calendar (summary)

Uranus - the Georgian Star - as seen by Voyager 2. When you view it in binoculars you may notice the bluish tint but it's doubtful. In fact, while the blue is attributed to the methane in its atmosphere, some folks say they see it in telescopes, some don't.

OK, so no one calls Uranus the Georgian Star these days, but it beats heck out of the adolescent giggles you get if you’re not very careful about how you pronounce Uranus – and “Georgian Star” was its given name. But whatever you call it, the seventh planet will be center stage this month, as it does a complex dance with its brilliant partner, Jupiter. We also have Venus and Mars with us in the evening sky in the west and – just barely – Saturn. In the morning sky Mercury puts in a nice appearance, and I really love what’s going on September 22 – we get the Fall Equinox, of course, plus a full Moon – the Harvest Moon – and we have both Jupiter and Uranus joining the Moon at opposition to the Sun. In fact, Jupiter is at its closest approach to Earth – by a hair – in nearly half a century.

But let’s start with the third largest planet – what was once dubbed the “Georgian Star” – and its close encounter with Jupiter. This is the second such encounter this year, but the first was in the early morning hours of June and the third will come right as the new year begins, which usually means in these latitudes, very cold observing. Such a “triple conjunction” of Jupiter and Uranus happens about once every 14 years. So I’m looking forward to watching, and charting, the two planets starting in September. It’s this close encounter with Jupiter, which dominates our eastern sky during September evenings, that makes The Georgian Star so easy to find this fall, though you’ll need binoculars. Here’s a movie made with Starry Nights Pro software showing you how Uranus appears to march past Jupiter between September 1, 2010, and October 15, 2010. The red circle is 5 degrees – the typical field provided by 10X50 binoculars. Later I’ll provide some charts as well.

“The Georgian Star” is also the title of a very readable new book by Michael D. Lemonick that details the astronomical explorations of William and Caroline Herschel and particularly William’s discovery of Uranus. But I’ve had enough of adolescents of all ages giggling when I forget the one way you can pronounce Uranus – YOUR-a-nus – without it sounding like a reference to a body part we usually don’t mention. So if the professional astronomers can demote poor little Pluto, then I’m for restoring Uranus to its original name, the “Georgian Star.” After all, that’s the name its discoverer gave it. Of course for Herschel this was frank flattery of King George III in a blunt attempt – successful, too – to get a life-time assignment as an astronomer with royal patronage.

For the rest of us the name “Georgian Star” is a good way to connect the planet to history and remind us of the approximate discovery date – George III was king during the American Revolution, and the Georgian Star was discovered in the spring of 1781 while that revolution was still going on. Up until then all the planets had been known since ancient times, and it was assumed that was all there were. So for several months Herschel and the rest of the astronomical brain trust of that day all tried to squeeze this odd object into some known category other than planet:

• It was, of course, a comet!
• But it had no tail.
• Yes, but it was too big to be a star.
• Ah, but it was not changing size the way a comet does – nor was it fuzzy!

Thus went the debate and so it wasn’t until the following fall that they pretty much settled on the idea that it was another planet – and then the name game started. Herschel leaped in with the Georgian Star, but this didn’t win much favor, except with King George – after all, many astronomers were not English and besides, the other planets had names that connected them to ancient gods. A couple of years later, the name Uranus was proposed by a German astronomer, Johann Bode – in German the name didn’t have the giggly implications that it has in English – and after about 50 years it pretty much stuck.

None of which makes the Georgian Star any easier to find. It looks like another star and a very faint one to boot. What gave it away to Herschel was that it appeared larger than a star when viewed in his telescope. Stars are pinpoints of light – this was a tiny, round disc. What’s more, when viewed over the course of several nights, it changed position relative to the “fixed” stars. And though it is barely on the edge of naked eye visibility in the best of conditions and hard to pick out from many other stars of similar brightness, you can find it easily this fall using nothing but ordinary binoculars – and you can watch it move! So step into the shoes of Herschel. How exciting it must have been in that spring of 1781, for this musician-turned-amateur- astronomer to have been the first to identify a new planet and in so doing double the known size of our solar system!

When and where to find Jupiter

You can see Uranus and Jupiter by hand holding just about any ordinary binoculars. However, for a nicer set-up, mount your binoculars on a camera tripod. This is especially useful - and might show you some of Jupiter's moons as well - when the planets are low in the sky. As Jupiter gets high in the sky, this will become less comfortable, however - in short, a pain in the neck.

Jupiter rises in the east near sunset. That means you have to wait a few hours for it to get high enough to easily see it and Uranus with your binoculars. Hint – if you can mount your binoculars on a tripod, that’s even better. A very good chance they will then show you one to four moons of Jupiter, as well as Uranus. Using binoculars on a tripod is awkward for objects that are high in the sky, but easy for objects that will be low, such as Jupiter at the times mentioned. (Go here for a utility that will tell you the position of Jupiter’s moons at any date or time.)

Jupiter cannot be missed, Just look between east and southeast for what will be, by far, the brightest “star.” Here’s when:

September 1, 2010 – three hours after sunset: Jupiter and Uranus will be 23 degrees above the horizon – a bit more than two fists.

September 17, 2010 – two hours after sunset: Jupiter and Uranus will be about 20 degrees above the horizon  – two fists – and for the next night or two about as close together as they get this month.

September 30, 2010 – two hours after sunset: Jupiter and Uranus will be about 25 degrees above the horizon – about two and a half fists.

Most binoculars will attach to a tripod with a simple "L" bracket. Before getting one, however, check to see if your binoculars have the necessary threaded hole on the brace between the lenses. This is usually hidden by a small cover that is easily removed.

When you locate Jupiter, use your binoculars and the appropriate chart from below to figure out which star is the Georgian Star – Uranus. When you have done so, pause and reflect for a moment. Do you understand why the ancients never spotted Uranus? Can you see it without the binoculars? And if you use a small telescope – think about William and Caroline Herschel and colleagues and how puzzled they would be by this object – star like, yet not a star. Like them, you can easily track the path of Uranus against the background stars on a chart of your own making. Just remember, both planets are moving and Jupiter, being closer to the Sun by far, is moving faster – and don’t forget that you are watching this from Earth, which is moving even faster than either of these “wandering stars.”

View through binoculars of Jupiter and Uranus about three hours after sunset on September 1, 2010, as depicted on a Starry Nights Pro chart.

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View through binoculars of Jupiter and Uranus about two hours after sunset on September 17, 2010, as depicted on a Starry Nights Pro chart. (This is the period of the closest approach of these two to each other this month.)

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View through binoculars of Jupiter and Uranus about two hours after sunset on September 30, 2010, as depicted on a Starry Nights Pro chart.

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Finally, if you would like to track the motions of Jupiter and Uranus over the next month or two, use the chart below and download the “printer-friendly (black on white) version.) Doing this will give you some sense of what it was like for the astronomers in 1781 who were trying to figure out what this new object Herschel had discovered really was!
Download this for a printer-friendly version of the above chart.

Jupiter is of special interest to telescope users this season as it showed up in June with a major belt missing. Even with the smallest telescopes, amateur astronomers are used to seeing two dark belts either side of the equator on Jupiter. But the southern one of these belts went missing while Jupiter was out of sight behind the Sun. There are signs now, however, that it is re-emerging, making each time you view Jupiter in a small telescope, something of an event – will the belt be there, or not?. What’s more, the Great Red Spot is located in the general area where the belt is now missing. The result is the Red Spot is easier to see, but Jupiter rotates very quickly on its axis and to see the Red Spot you need to be looking at the right time. Sky and Telescope has an online calculator you can use to find out when the Red Spot will be well placed for observing. Go here to use that calculator.

The equinox – and Harvest Moon, and Belt of Venus

On or near September 22 will be a fun time to watch a sunset – especially if you have a clear horizon to both east and west. I love to do this on a local point of land that juts southward into the ocean and gives me such a view in both directions. What’s so special about September 22?

1. It’s the fall equinox, which means the Sun will be setting due west and day and night will be of nearly equal length.

2. It’s the night of the full Moon – the Harvest Moon – and that means it will be rising directly opposite the Sun as the sun sets.

3. It’s very close to the time when Jupiter – accompanied by Uranus – will be in opposition to the Sun – meaning they rise in the east as the Sun sets in the west.

4. And finally, it’s a good time to look for some natural phenomena that you have probably seen many times but not realized what you were seeing – the Earth’s shadow and the Belt of Venus.

Here’s a wonderful picture taken by Doug Miller and used some years ago as the Astronomy Picture of the Day. Note the dark band at the horizon – that’s the Earth’s shadow – and the rosy band above it – that’s the Belt of Venus. This reddish sky is caused by the atmosphere reflecting light from the setting Sun on the opposite side of the sky. You will see this in the EAST within the first 20 minutes or so after sunset.

At sunset look EAST and you will see something like what Doug Miller captured here. The dark band near the horizon is the shadow of the Earth, and the rosy band above it is the Belt of Venus. Click image for a larger version.

Now, of course, on the 22nd you will also see the Harvest Moon in this area – or perhaps just above it. It rises about three-quarters of an hour before sunset on that evening. (Technically, the Moon isn’t full until nearly sunrise the next morning. )

This shows where the Moon and Jupiter will be at sunset, but you probably won't be bale to pick Jupiter out for another half hour or more. It will tag along with the Moon as they both rise. (Prepared from Starry Nights Pro screen shot.)

What’s more, at sunset, just below the Moon, a brilliant Jupiter will be rising – though you may have to wait a while to see it because of haze near the horizon. As Jupiter gets higher in the sky – an hour or more after sunset – you might be able to pick out Uranus in the same binocular field of view as explained earlier in this post. (I say “might” because a full moon about five degrees away will wash out the sky making it hard to see Uranus, though Jupiter will stand out since it’s so bright.) If the 22nd isn’t clear, you can observe this phenomena at any sunset, but to see Jupiter rising about this time you’ll want to look within several days either side of this date. (On other nights the Moon will be farther from Uranus and so it should be easier to see it than on the 22nd.)

Jupiter is actually at opposition on September 20 when it will be closer to the Earth – and thus appear larger in our telescopes – than at any time since 1963. But don’t get too excited – closer means a percent or two closer than it was last fall or will be next fall. It will also be extremely bright – magnitude -2.9. That means the only things brighter in the sky at this time will be the Moon and Venus. At magnitude -4.6 Venus will be really dazzling – about as bright as it gets. However, it also will be quite low in the southwest – at sunset just about one fist above the horizon. Half an hour later – when it should be dark enough to see it easily if your horizon is clear, it will be little more than five degrees above the horizon – about the same height the Moon was at sunset.

If you point your binoculars at Venus in the southwest about half an hour after sunset, then you should be able to pick out Mars off to the right and up a bit. It will be about 7 degrees away – which means it may not fit in the same binocular field of view as Venus, but you should only move a little bit to find it. At magnitude 1.5 it will be much dimmer, looking like a little red star. Saturn, which will be visible with a careful binocular search earlier in the month, is now blotted out by the Sun. (If you want to get a final look at it for this season, you will find it below Venus and well to the right – close to due west – during the first week of the month. )

Fleeting Mercury

Fleeting Mercury – it’s not just a cliche – it’s a reality. The fleet-footed messenger of the gods is aptly connected with the fastest-moving planet. Its average orbital velocity is about 107,000 miles an hour as compared with 66,000 miles an hour for Earth, or 29,000 miles an hour for Jupiter. So Mercury can really zip around the Sun, and in doing so our view of it changes rapidly. Note this sequence of events:

September 3 – Mercury behind the Sun and thus out of sight to us.

September 13th – Mercury visible a half hour before sunrise about 8 degrees above the eastern horizon and about 5 degrees below Regulus. Two days before. Mercury was fainter than Regulus. But on the 13th it’s brighter and will continue to brighten.

(Prepared from Starry Nights Pro screen shot.)

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September 19th – Mercury is as far west of the Sun as it gets this time – and thus easily visible in the eastern morning sky and blazing at magnitude -0.3 – much brighter than magnitude 1.3 Regulus.

After that, it plays a little game with us – on the one hand it continues to get brighter, but on the other hand it also drops nearer to the Sun, so it starts to get lost in the glow of dawn. By the end of September, it is just 6 degrees above the horizon about half an hour before dawn – visible, but no longer easy to see unless your morning horizon is very clear.

Click image for larger version. (Prepared from Starry Nights Pro screens hot.)

September 2010 Calendar

• 1- Last quarter Moon
• 1-7 Look for Venus, Spica, Mars, and Saturn in the western sky half an hour after sunset. Binoculars needed for all but Venus.)
• 8 – New Moon
• 10- Venus, Mars, Spica, and a 3-day old crescent Moon make a nice gathering very low in the southwest after sunset. You should be able to cover them all with a fist held at arm’s length.
• 13-30 Time to start looking for Mercury in the morning sky, about an hour to 30 minutes before sunrise.
• 15 – First quarter Moon
• 17 – Uranus and Jupiter less than a degree apart for several nights.
• 22 – Sunset special – Venus and Mars in the west, Jupiter and Uranus in the east, plus a Harvest Moon and a good time to look for the Earth’s Shadow and Belt of Venus. However, Uranus will be difficult to see because the Moon will be so near to it.
• 23 – Full Moon
• 30 – Last quarter Moon