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    My Journey through the Astronomical Year

    Think of this as a "companion text" to this, the main web site. Not required reading, butI hope you'll find it interesting and helpful.

June 2010 events: A month of surprises involving Jupiter, a comet, and maybe even some meteors!

Note: While many of the following events are visible throughout the world, the exact time and location in the sky can be dependent upon your latitude and longitude. Since I’m in the mid-northern latitudes (41.5N, 71.1W), specifics, where place-and-time-dependent, are calculated for this location.

Observing Jupiter and Uranus

June promises to be full of surprises, most revolving around getting up early to enjoy a summer dawn! I’m circling the weekend of June 12-13 on my calendar as special in terms of getting up early, and I’m hoping for a triple header: viewing Jupiter, finding Uranus, and seeing Comet McNaught. For the meteors, it will be June 23 and in the evening – though there’s a real big question mark around this event. Let’s start with a sure thing – Jupiter and Uranus.

You can’t miss Jupiter. It’s the brightest “star” in the southeast in our morning sky. You can easily miss Uranus. It’s barely naked eye visibility in the best – least light-polluted – locations and hard to pick out from true stars in the area. But on a morning in June finding Uranus should be an easy task with any decent pair of binoculars because Jupiter will guide you right to it.

It’s Jupiter that offers our first surprise for those who can turn a small telescope on it. Usually even the most modest telescope will show you two dark belts on Jupiter – but this June there’s no telling Jupiter missing bandexactly what you’ll see. Jupiter’s been hiding behind the Sun recently, but when it emerged in May it surprised planetary observers by displaying just one of its major trademark dark bands. The other had vanished!

If you have a small telescope and point it towards Jupiter on a June morning will you see it this way? Can’t say. That’s why it will be a surprise. Veteran observers think the second band could come back quite quickly – in just a week’s time, for example. They say this sort of thing is rare but has happened before. One theory is that high, thin, light-colored clouds are covering the band, and these clouds may vanish without warning – just as they appeared without warning.

Jupiter is second only to Saturn in its appeal to small telescope users, not only because of its bands, but because of the constant dance of its four Galilean Moons, which you can detect if you can manage to hold even modest binoculars, such as 10X50s, steady. And Jupiter this year will be doing an even grander dance with its outer cousin, Uranus. The two gas giants come quite close to one another – as viewed from Earth – three times in the next seven months, the first being in June. That means Uranus, usually a difficult object to find because it is so faint, will be an easy target for binocular and small telescope users – though its disc is so small it will hardly show except in a telescope at high power.

Here are a couple of images giving you the position of the two planets early in the month and near the end of the month.

jupiter_uranus_2010

Click image for a larger view. Image developed from "Starry Nights Pro" screen shot.

For a printer-friendly version of the appropriate chart for on or near June 6, 2010, click here.

For a printer-friendly version of the appropriate chart for on or near June 30, 2010, click here.

A good project would be to take the print out of the first chart (June 6) and mark the position of each planet when observed about once a week. You’ll notice that both drift to the east (left) against the background of stars, but Jupiter’s progress appears much faster because it is so much closer to us. That would help you appreciate the fact that when Uranus was discovered March 13, 1781, by the English astronomer William Herschel, it effectively doubled the size of our solar system! (And if you don’t want to get up early several mornings to actually see this, just study the charts above, but be sure to click on them to see the larger version. 😉 For more on Uranus see the May events entry.

The two planets come closest on June 8 when they are less than half a degree apart. However, any time during the month they will easily fit in the same binocular field of view. I’m aiming for observing on or near the 12th simply because it’s a weekend, and since there’s no Moon in the sky to drown things out with its glare, that will also be a good time to spot the comet.

Seeing Comet McNaught at its best

Comets are notoriously unpredictable and catching them at their best is a game you play, trying to balance the time when the comet is close to the Sun – and thus usually brightest – against the approach of dawn, which lightens the sky behind the comet as it gets closer to the Sun and thus makes it more difficult to see.

Northern hemisphere observers are overdue for a nice comet and McNaught (C/2009 R1) could be it. Astronomy magazine thinks it may reach naked-eye brightness with a distinct tail. Sky and Telescope seems a bit more cautious in its prediction, but still thinks it will be very nice in mid-June. In 2007 another Comet McNaught (C/2006 P1) put on an absolutely spectacular display for southern hemisphere observers, becoming the brightest comet in 40 years seen from anywhere on Earth. Sadly, for those in mid-northern latitudes the show was nowhere near as good and was so brief many missed it. I was lucky to catch it, but against strong twilight, so it didn’t show at its best. I took this shot of Comet McNaught over Horseneck Beach in Westport on January 11, 2007.

McBaught_2007

Bren and I saw an earlier Comet McNaught in strong twilight and amidst clouds in 2007 shortly after sunset.

A recent study, however, has found that Comet McNaught was not only a spectacular sight from the southern hemisphere, but also probably the largest comet on record.

It’s fairly safe to say this Comet McNaught will not be nearly as spectacular – but it could be quite nice, especially in binoculars, and it should be easy to find as it will be going past some well-known stars. In fact on the morning of the 12th it will be right between Algol (the Demon Star) and Mirfak, brightest star in the constellation Perseus. Here’s a chart – but take the show of the comet’s tail as simply a rough indicator of the tail’s direction. I doubt it will be this large. (Starry Nights software, from which this chart was derived, shows all comet tails about the same length.)

Comet McNaught 2010

Click image for larger version. Chart derived from "Starry Nights Pro" software.

For a printer-friendly version of this chart, click here

As with the Jupiter/Uranus event, Comet McNaught should be visible much of the month. But early in the month it will be dimmer, and later in the month it will be so close to the Sun that the dawn twilight will drown it out. The middle of the month seems like the best bet for catching the comet when it’s quite bright and will be high enough in the sky to see well during a time period when the sky behind it is fully dark.

The beginning of astronomical twilight is when the sky starts to brighten and continues to do so right up through sunrise. For my area – and other mid-northern latitudes – astronomical twilight starts about 3 am in mid-June, more than two hours before sunrise. (Tables for astronomical twilight times for your area can be easily created at the U.S. Naval Observatory site here.) My plan, weather permitting, is to go out on Saturday morning, June 12, to a local observing sight that has a beautifully clear and dark eastern horizon, and to be there by 2:30 am EDT. That will give me an opportunity to see Comet McNaught when it is about 15 degrees above the northeastern horizon. I expect to have a good view right up through 3:30 am – after that I expect the interference from the approaching dawn to become serious. (That’s the date of new Moon, so it will offer no interference for several days either side of this date.)

But again, comets just aren’t that predictable. Back in 1973 I published a cover story in Popular Science quoting experts who predicted that Comet Kohoutek would be the “comet of the century.” It was no such thing and I was embarrassed! And the most exciting comet of recent years for me was Comet Holmes in 2007, which suddenly – and inexplicably – broke into naked eye glory when no one was expecting it to do any such thing.

What can be done with accuracy is to predict when and where you can expect to see Comet McNaught. Those predictions you can trust. And you should begin your search with the naked eye, but I suspect binoculars will give you your first view, and it may take a small telescope to give you a really decent look at it.

Addendum:

  • For an orbit diagram of the current Comet McNaught see this page.
  • This Comet McNaught is the 56th comet discovered by this man. Why so many? Well, for the past five years or so it’s been his job to find comets  that may pose a threat to Earth and he has the tools to do it. Go here to learn more.

Catching the elusive Bootid meteors

If anything in amateur astronomy seems riskier than making predictions about comets, it’s making predictions about meteor showers – especially unusual ones that flare up on rare occasions. But Astronomy magazine is carrying a prediction that on the night of June 26 – and we’re talking the more comfortable evening hours now – we could get quite a display.

It reports that the International Meteor Association predicts that the peak of this shower could occur on June 23/24 between 7 pm and midnight EDT. Well, of course that means this favors the East Coast and even then, it may peak while it is still light, since you won’t have complete darkness until after 10 pm.

Frankly, I’m very skeptical about this one, but if it’s clear that night I’ll do some observing of double stars and keep an eye out for meteors at the same time. The problem is simple: at 10 pm the Moon, just a couple of days short of full, will be low in the southern sky, but still high enough so I think it will drown out many of the meteors. So what we have here is a prediction that a normally quiet “shower” may suddenly have a real outburst worth seeing – but that outburst could come during daylight or twilight, and if it comes during full darkness it will be competing with bright moonlight. That just doesn’t seem all that promising. But then, what can you lose being out on a warm June evening with clear skies, bright moon, and and fireflies? And now you know you may get lucky and see some bright meteors as well – maybe a whole lot of meteors 😉

June’s Calendar – a chronology and review

You have the highlights above – here’s a summary of them, along with some additional June events, in chronological order.

  • June 4 – Last quarter Moon
  • June 5,6,7,8 – Watch Mars pass close to Regulus – note color difference! (Mars is just a tad brighter.)
  • June 6 – Good time to start your search for Uranus and Comet McNaught
  • June 12 – New Moon – prime weekend for an early morning expedition to see Jupiter, Uranus, and Comet McNaught
  • June 14 – Brilliant Venus just above a thin crescent Moon – nice!
  • June 19, 20 – Venus is just 1 degree from the Beehive – use binoculars to see the stars near this most brilliant planet.
  • June 21 – The Summer Solstice – and shortest night of the year. Comet McNaught should be getting quite difficult to see by now.
  • June 23 – Cross your fingers and hope for some spectacular meteors appearing to radiate from Bootes still high in the evening sky.
  • June 26 – Full Moon – and a partial lunar eclipse in the morning sky for folks in western North America and points west.

Look North! In June Deneb gets in the act here too!

June's north sky chart

Click on image for larger version. (Created from a "Starry Nights" screen shot.)

For a printer-friendly version of this chart, click here.

Yep, that’s Deneb, the guide star that is the subject of our “Look East” Post for June, gracing our “Look North” chart as well. In fact, besides Polaris we have three key guide stars in our northern sky in June, each of which is noted for, among other things, just how far north it is.

Of the three, Capella may be the hardest to find, for it is very near the horizon in the northwest around sunset. But if you have a clear horizon in that direction, you should still pick it up, especially at the start of the month. More prominent, however, are Deneb and Vega. These stars play the key role in one of the best known sky triangles – the Summer Triangle, but that triangle becomes easier to see next month and it will be in the eastern sky. For June it is fun to link Deneb and Vega with Polaris in what we’ll call the North Sky Triangle – and the linkage has some special meaning.

See, we just happen to be lucky to be living in an era when we have a bright star near the North Celestial Pole – Polaris. There’s no such bright star near the South Celestial Pole, and in other eras there is none near the North Pole either. But in the distant past – and in the distant future – Deneb actually will be the bright star nearest the pole – not as near as Polaris, but still a good general guide to it.

gyroscope precessionThat’s because the Earth wobbles as it spins on its axis in much the same way as a spinning top does. So the axis of the Earth doesn’t always point to the same place. It slowly makes a great circle around the northern sky, taking roughly 25,000 year to complete. Right now our axis is pointing to within a degree of Polaris. Not precise, but good enough so it is a ready indicator of true north. A mere 18,000 years ago Deneb was within 7 degrees of the pole and will be again around the year 9800!

This wobbling of the pole is really kind of mind boggling. I look at Polaris now, and it’s a bit short of 42 degrees above my northern horizon. But in a mere 14,000 years, Polaris will be almost straight over my head, and guess what will be the pole star then? Not Deneb, but its brighter – in our skies – companion, Vega. Of course none of us is likely to witness that event, but it’s still food for thought and gives us a sense of the majestic rhythms and time frame of the heavens.

And speaking of that time frame, as I write this it occurs to me that 14,000 years really feels like a very long time from now – while the 10-million-year age of Deneb doesn’t seem that long – and it isn’t, astronomically speaking. I’m not talking now about what your mind tells you about those numbers. I’m talking about your emotional reaction to them. I wonder if it’s similar to mine? This isn’t idle speculation. It’s central to our appreciating what we are seeing. But I think 14,000 sounds like a long time because it’s a number that fits into our day-to-day experience. Huge, but we can easily imagine 1,000 miles. In fact, we’ve probably traveled that far and farther at different times in our lives. So imagining 14,000 of something comes easily to us. But few of us have any experience with one million. It would take about 11 days to count one million seconds and no one in his right mind is about to try it. So when we speak of the 10-million-year age of Deneb, or the five-billion-year age of the Sun, the numbers lose their emotional impact because they don’t relate easily to our experience. But 14,000 – well, we know, in an emotional sense, just how long that is!

Look East in June to a supergiant that looks small to us – Deneb

How can we make the stars pop out of the sky and into our mind’s eye? That’s the perennial problem for me, for what we actually see is so much less than what is actually there that we can’t help but to either ignore or belittle the stars unintentionally. This month’s guide star, Deneb, is a prime example. It’s easy to spot using our chart as it rises in the northeast below and to the left of Vega. In terms of our bright guide star list, Deneb’s rather dim – 19th in the list of brightest stars we see with the naked eye. But that reveals much more about our point of view than about Deneb.

Deneb, plain and simple, is one of the most luminous stars in our galaxy. Vega, just above and to the right of it in the northeast, looks so much brighter – but it isn’t. It’s simply so much closer. Vega is just 25 light years away. Deneb, by the most recent calculations, is 1,425 light years from us. Put Deneb in Vega’s place and it would be visible in broad daylight!

When astronomers talk about how “luminous” a star is they don’t mean how bright it appears to us in our night sky. They mean how bright it actually is. In fact, frequently they use “luminous” to include all the radiation that comes from a star – even radiation in wavelengths that we don’t even see, such as infrared and ultraviolet. They then compare a star’s luminosity with the luminosity of the Sun – the Sun being “1.” When they examine Deneb that way they get a luminosity of 54,400 Suns – awesome! But when we look at Deneb we see a star that is just moderately bright – magnitude 1.25.

east_june_2010

Click image for a larger version. The full "Northern Cross" asterism will appear only as the twilight dims and the night gets darker. As the month goes on it will be easier to see. This asterism is the core of the constellation Cygnus the Swan and by itself, especially as it rises, suggests a swan flying south. Around Christmas time the Northern Cross will appear to stand almost upright near the northwest horizon. You may also spot Altair, next month's guide star. (Developed from Starry Nights screen shot.)

For a printer-friendly version of this chart, click here.

When you look at Deneb, you have to use your mind’s eye to see it for what it really is, not just for what it appears to be. So what should we see when we look at Deneb?

First we should see something huge. Deneb is classed as a “supergiant.” So sit back and try to imagine a star whose diameter is 108 times that of the Sun. No, wait! First imagine how big the Earth is. Then get in your mind the fact that the Sun is 109 times the diameter of the Earth. Got that? Now try to imagine that Deneb is to our Sun what our Sun is to the Earth.

birdshotBut wait! I really do not want to talk about diameters. Those are for people who live in a flat world. Think in terms of volume, because that’s what a planet or star really is – a volume – a mass formed into a sphere. To get your mind around volume, picture the earth as a tiny bird shot just 2.5mm in diameter. Here’s one to give you the idea.

Now picture a sphere about 10.5 inches in diameter – a basketball would be close, or this glass garden globe. See the difference? When talking diameters, the Sun is 109 Earths. But when you’re talking volume, you could fit well over a million Earths inside the Sun.

sun_deneb

Now think about the same thing in terms of Deneb. That little lead shot is our magnificent Sun. The blue globe is Deneb! That’s what you should see in your mind’s eye when you watch this month’s guide star rise in the northeast. Were Deneb our Sun, its surface would reach halfway to the orbit of Earth and needless to say, Earth would be in a hopelessly hot location.

But there’s more, of course. Size is a great starting point, but it doesn’t equate with mass. A lot of stars are bloated – that is, their mass is spread out over a large area and they have a huge surface area from which to radiate a tremendous amount of energy. That is the case with Deneb. It is believed to be about 10-15 solar masses, but its total luminosity – the total amount of energy it radiates when compared to the Sun is a whopping 54,400 times that of the Sun! Wrap your mind’s eye around that!

That’s why astronomer/author James Kaler writes that Deneb is

among the intrinsically brightest stars of its kind (that is, in its temperature or spectral class) in the Galaxy. If placed at the distance of Vega, Deneb would shine at magnitude – 7.8, 15 times more brightly than Venus at her best, be as bright as a well-developed crescent Moon, cast shadows on the ground, and easily be visible in broad daylight.

When you’re outside this June watching Deneb rise in the northeast, pause a moment and look to the northwest where brilliant Venus dominates the evening twilight. Now turn back to Deneb and imagine it 15 times as bright as Venus.
Deneb is unusual for supergiant stars for it is of spectral Class A – that means it’s your basic white star and very hot as stars go. Other very large stars, such as Betelgeuse, are in a different stage of development and quite cool and red to the eye. Deneb is believed to be just 10 million years old. That’s very young in terms of star ages. Our Sun is believed to be 5 billion years old. Deneb will never get to that ripe old age. Massive stars such as Deneb live in the fast lane, burning up their core hydrogen fuel relatively quickly.

Kaler gives this analysis:

The star is evolving and has stopped fusing hydrogen in its core. However, it’s hard to know just what is going on. It might be expanding and cooling with a dead helium core and on its way to becoming a red supergiant, or it might have advanced to the state of core helium fusion. Having begun its life as a hot class B (or even class O) star of 15 to 16 solar masses just over 10 million years ago, its fate is almost certainly to explode sometime astronomically soon as a grand supernova.

Kaler certainly knows what he’s talking about, but don’t bother to keep a “death watch” on Deneb. “Astronomically soon” means some time in the next 100 million years or so 😉

Sherlock Holmes once chided his companion Watson saying “you see, but you do not observe.” With the stars, we have to take our cue from Holmes. We have to go beyond merely seeing. And in truth, we have to go beyond merely observing. We have to take the knowledge the scientists have given us and somehow apply it to what we see, so with our mind’s eye we truly observe. Only then can we pop Deneb out of that “twinkle, twinkle little star” category and see it for what it really is.

Vital stats for Deneb (DEN-ebb), also known as Alpha Cygni:

• Brilliance: Magnitude 1.24; its luminosity is the equal of 54,400 Suns.
• Distance: 1,425 light years
• Spectral Types: A2 supergiant
• Position: 20h:41m:26s, +45°:16′:49″

Guide star reminder

Each month you’re encouraged to learn the new “guide” stars rising in the east about an hour after sunset. One reason for doing this is so you can then see how they move in the following months.

Deneb and the Northern Cross join several other guide stars and asterisms in the June sky. Again, if you have been reading these Posts for several months, be sure to find the stars, asterisms, and planets you found in earlier months. Early on a June evening these will include, from east to west, the following: Deneb, Vega, Arcturus, Spica, Saturn, Leo’s Rump (triangle), Mars, the Sickle, Regulus, the Beehive, and in the northwest getting near the horizon, Pollux and Castor. You may also see Capella very near the horizon, and you certainly won’t miss Venus, the a bright evening “star” dominating the sky in the west.

For more experienced observers looking to extend their knowledge of the skies this month, I highly recommend trying to track down two more asterism – the Northern Crown and the Keystone. OK, technically the Northern Crown (Corona Borealis) is a constellation. But I always apply the name to the handful of moderately bright stars that look like a half circle – a crown. As the chart below shows, these two asterisms are located on a line between Arcturus and Vega and they sort of divide that line into thirds. As with our guide stars and other asterisms, they will help you if you advance to finding other more interesting objects int he night sky with binoculars and telescope.

keystone-crown

You'll need dark skies relatively free of light pollution to find these two asterisms. (You also should click the chart to get a larger image.) Chart was developed from "Starry Nights" screen shot.

For a printer-friendly version of this chart, click here.

The Crown itself can provide you with an interesting test of how dark your skies are since a couple hours after sunset on June night it is well up in your eastern sky. It consists of a circlet seven stars which can just fit within the field of view of wide-field binoculars – the example below shows an eight degree circle. It may be helpful to look at these stars with your binoculars, even if they don’t all fit in the same field of view at once. But to test how dark your skies are – and how transparent they are at the moment – wait until your vision is dark adapted, then see how many of these stars you can see. The numbers beside the stars are the magnitudes in decimals as given by Starry Nights software. However, I’ve followed the convention of not using a decimal point, since it might be mistaken for another faint star.  So “41” means magnitude 4.1, for example. If you are seeing all seven stars you can be happy with your skies and these light=[olluted times. In a truly dark location, however, this will be easy – but sadly such locations are rare these nights.

Read text above for explanation of how to use. Thenc lick on image to give you a larger view and luse the link below to download a printer friendly version. (Made from Starry Nights screen shot.)

For a printer-friendly version of this chart, click heret.

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