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  • Rapt in Awe

    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.

August 2013 – last good look at Saturn, and a Moon-free Perseids shower

The Big Dipper's handle can guide you first to bright Arcturus, then to yellowish Saturn and blue Spica - both will be about the same brightness. Venus is much birghter, but best seen about half an hour after sunset when it is about 10 degrees above the western horizon. By an hour after sunset it ishalf that or less and even if you have an unobstructed horizon, may be lost in mist and twilight.

The Big Dipper’s handle can guide you first to bright Arcturus, then to yellowish Saturn and blue Spica – both will be about the same brightness. Venus is much brighter, but best seen about half an hour after sunset when it is about 10 degrees above the western horizon. By an hour after sunset it is half that or less and even if you have an unobstructed horizon, may be lost in mist and twilight. CLick for larger image. (Prepared from Starry Nights Pro screen shot.)

For a printer friendly version of the above chart, click here.

If you have a small telescope, August 2013 will give you your last good look at Saturn for the year and if you live on the right side of the globe – not where I live – the Perseids  meteor shower should be spectacular this year with no interference from a waning Moon.  Venus, meanwhile, continues to reign low in the western sky just after sunset.

The sky north of east early on the morning of August 12, prime time to watch for Perseids meteors. (Created froma Starry Nights Pro screenshot.

The sky north of east early on the morning of August 12, prime time to watch for Perseids meteors. (Created from a Starry Nights Pro screenshot.)

For a  printer friendly version of the above chart click here.

The Perseids should reach their peak on August 12 at about 19:00 UTC. To find what time that is for your region, go here.  For about half the world that’s good news, for the other half it’s bad because you really want to see this shower in the early morning hours and you will get the best show if the shower’s peak falls during those hours for your time zone.

Locally, on the East Coast of the United States, I’m going to watch the weather and if either the morning of August 11 or the morning of August 12 is forecast to be clear, I plan to start observing about 2 am. But I am not expecting a big Perseids show – just a nice summer night with a much better chance than usual of seeing a bright meteor.

Meanwhile, I’m bracing myself to hear a lot of promotional blather about the Perseids locally from TV weather folks and others who should know better, but the truth is in North America the timing of this year’s shower could hardly be worse.  The shower is best for a couple hours either side of its peak and its peak is forecast to come at 19 hours GMT on August 12 – for Eastern Daylight Time that translates to 3 pm – broad daylight.  What’s worse, even if the peak was in the early evening hours, the Perseid’s radiant point doesn’t get high in the sky until the early morning. That’s why the best time to see Perseid meteors – regardless of the peak time – is still  between midnight and  a couple hours before dawn.

So can we in America hope to see any Perseids at all? Yes, of course we can.  Just don’t expect a “shower.” In fact, I have to say that i always wince a little at the times and rates of meteors frequently given in news reports. Hey, just the word “shower” implies a lot more than most people usually see, especially from their typically light-polluted back yards.  When someone reports that the Perseids will peak at better than 100 meteors an hour, they usually fail to mention that three conditions have to be met for you to see that peak.

1. You need the Perseids radiant point to be nearly directly overhead – for EDT that occurs in a twilight sky, but is reasonably high from midnight on. The meteors may appear in any part of the sky, but they will appear to radiate from that point, so the higher it is, the better chance we have of seeing a meteor.

2. You need very dark skies – skies that will allow you to see magnitude 6.5 stars, if you are going to experience those real high rates. I have never experienced such dark skies, but they certainly exist. However,  with my reasonably dark skies I am very happy when I can detect a star of magnitude 5.

3. And, of course, you need the shower’s peak to coincide with the radiant point being very high in your sky.

One more caution – anything can happen. This is a forecast and usually reliable. But there could be a burst of meteors at a different time. You may get lucky.

And if all these  condition aren’t met for your location? Well, it’s reasonable to expect to see a Perseid meteor about every 10-15 minutes – of course you  may get two or three in a row hardly separated at all, then not see another one for  an hour. But be patient and you will get results – just not the meteor spectacular that some reports will imply. Last year they were coming in at a rate of 15-20 an hour four hours either side of the peak.

And yes, a Perseid can show up days either side of the peak.  How will you know it’s a Perseid? Draw a mental line extending the path of the meteor back towards the Perseid’s radiant point. If your line points back to that area of the sky – see map above – then you saw a Perseid. But there are always strays around – random meteors that have no connection to the shower – and at this time of year we have a couple weaker showers that may produce a few meteors going in other directions.

Meteors and meteor showers are fun if for no other reason than they are a chance to see something happening in the sky. Much of what we look at doesn’t change – or rather changes so slowly we don’t notice the change. Meteors, on the other hand, demand that you be looking in the right place at the right time. Only on the very rare, very bright meteors do we actually have time to alert others and have them turn their heads and see what we see.  And what we see is a space event happening closer to us than any other natural one. What’s more, meteors can have real scientific value.  They are viewed by some as our cheapest “space probe.” They are relatively pristine bits of matter left over from the early days of the solar system and so can tell a story to those who know how to read them.

Meteors – “falling stars ” – can be seen any time. You don’t have to wait for a “shower” like the Perseids; you just have to be lucky. But they are most frequent at certain times in the year when the Earth happens to be plowing through a meteoroid-rich area.  We call this occasion a meteor shower. (For your dictionary: A meteoroid is a small bit of space rock that becomes a meteor when it collides with our  atmosphere and heats to incandescence as it descends towards Earth. When it gets here – which is rarely as anything except fine, incinerated dust – it is a meteorite. )

The reason for a shower such as the Perseids is that we are passing through the debris trail of a comet. Think about it. The general model for a comet is a “dirty snowball,” and as that dirty snowball nears the Sun it melts, and as it melts it leaves a trail of dirt particles behind it – particles that remain in orbit until something like the Earth sweeps by and captures some of them with its gravity.

The comet itself can vanish entirely – but the result is a river of space dust – a river that is most intense nearest where the comet actually was.  That’s why there are some years – the 1990s in the case of the Perseids – when the meteor shower is more intense than others.  Now we are in a period when we are passing through the trail of the comet that creates the Perseids at a point where that trail is relatively sparse – so there will simply be fewer Perseids than there were  15-20 years ago.

That trail is not encountered all over the sky. It collides with our atmosphere near a particular point in our sky. That point is called the radiant – you might think of it as a hole through which the Perseids fall – and in the case of the Perseids, it appears to be in the constellation Perseus.  But we don’t see all the meteors at this point. We see a meteor only when its collision with our atmosphere is intense enough to make it burn up. The faint meteors we see are made by a speck of dirt about the diameter of a pencil lead. The brightest ones are caused by something about the diameter of the pencil’s eraser.  In either case it will, for all practical purposes, burn up entirely in our atmosphere – 50 to 75 miles up – and nothing significant will remain for anyone to find on Earth. But exactly where it burns up is another thing. That’s why we will see a sudden flare – a falling star – anywhere in the sky.

And that’s awesome! Consider this: If someone struck a match 50 miles away would you see it?  Yet a grain of sand, hurtling into the atmosphere, shows us such a brilliant light we can’t miss it! Why? Well, for one thing it is hitting our atmosphere at something in the order of 133,000 miles an hour – that makes a “speeding bullet” look like the proverbial turtle!

When you are watching for Perseids, you don’t have to look near the radiant point, though you will see more there.  A meteor can flare up suddenly anywhere and appear to draw a short (usually 5-10 degrees long) straight line across the dome of the sky. (Bright ones may actually leave a trail, which you can see for a few seconds with the naked eye or longer with binoculars.) If we trace a line backwards along the meteor’s trail we will see it comes from the area near the radiant point.

In the early evening, that Perseid radiant point is low in the northeast. That means nearly half the meteors that are radiating from it are happening below our eastern horizon. That’s why the shower is best in the early morning hours when the radiant is high in our sky. If the radiant is overhead, then we have nearly doubled our chances of seeing a meteor.

There are many meteor showers in the course of a year and some are better than others. The Perseids is one of the most reliable ones and happens to come at a convenient time for northern hemisphere observers when it is comfortable to be out at night, lying on the ground, and looking up.

In the final analysis there’s only so much time you can spend lying on your back gazing at the starry sky; though I very much enjoy that time, it’s made much more enjoyable by knowing that at any instant there’s a heightened likelihood that I will see a bright meteor.  That – and the summer Milky Way – make looking for Perseids in a dark and moonless sky always worth the effort for me.

August 2012 – Mars, Saturn, Spica in the west – and a spectacular Perseids shower

Should you watch the planet show in the West in the evening? Or the meteor shower in the morning? Why not both? And if you’re getting up early to see the Perseids at their best, be sure not to miss brilliant Venus and Jupiter – well, how could you?

Over in the west we have Mars showing you how fast a planet can appear to move as it runs between  Saturn and Spica – over a period of three weeks making a colorful red, blue and yellow display.  And all over the sky for several days this month you are likely to pick up a brilliant, Perseid meteor – but particularly on the morning of the 12th of August with the 13th a good back-up – and this year’s show should be especially good because the Moon will not put in an appearance until early morning and will not be bright enough to ruin the show.

Let’s start with the west – week-by-week the changing scene will look like this low in the southwest about an hour after sunset:

The circle is 7 degrees – roughly what you can expect from a low power binocular view.

 

A fun night because a young, crescent Moon joins our trio.

You will need a clear and unobstructed  western horizon for this one because these three objects are roughly 10 degrees – one fist – above the horizon. (Early in the month they’ll be a bit higher – late in the month they get quite low.  Now what I love about this event is it demonstrates three things –

  • Color in the sky – Saturn is yellow, Mars, Red, and Spica blue. But these colors are subtle. You’ll see them better if you use binoculars and you might want to review this post on star colors to better know what to expect.
  • Perception and the effect of motion – from night to night Saturn will hardly appear to change positions relative to the background stars at all,  and Spica won’t  change – but Mars will whip right along and this will be amply clear as you check it’s position against the other two.  The reason is simple – Mars is much closer to us at about 158 million miles; Saturn is about 939 million miles and, of course, Spica is so far away we measure its distance in light years – 263.
  • The time dimension is on display as well – Mars is roughly 14 light minutes from us, Saturn is  well over a light hour, and Spica  263 light years. So what appears to be a two dimensional scene is revealed to be three dimensions as you observe the rapid motion of Mars and picture the solar system – and when you put your mind to it, you understand that the instantaneous nature of the scene is an illusion – that you are really looking into the fourth dimension and what happens simultaneously from your perspective is really happening at much different absolute times.

To help grasp the situation, take a look at this Orrery view of the Solar system for August 7. Keep in mind two things. The east-to-west motion we see as the night goes on is due to the spinning of the Earth.   The night-to-night westward – downward – drift of all  is caused by the motion of the Earth in its orbit around the Sun.

Orrery view for August 7, 2012, (Click image for larger version.)

The yellow arrow in the image above shows our view of Mars and Saturn in the evening sky. As the Earth rotates counter clockwise on any given evening, first Jupiter, then Venus come into view in our morning sky – red arrow.  If you then picture the Earth moving ahead in its orbit it’s not hard to understand why Saturn and  Mars will eventually be lost from view, while Jupiter will appear earlier each evening. Venus is a bit more complex. It too will get lost in the glare of the Sun, but since it is moving faster than us the change will appear to take place fairly slowly. Maybe I’m just slow, but it has taken me years to move from these abstract representations of what we see in the sky and how the planets are moving, to get to the point where I can look up and have a genuine, intuitive sense of what’s going on. Very satisfying and worth the effort, but even if you don’t do that, it’s a wonderful show! (The Orrery view is obtained from Solar System live web site. Go there and play with the dates to see the changing motions of the planets.)

Perseids in the morning

OK – so much for the evening sky. The morning sky is really spectacular because we’re looking at a section of sky that contains a lot of our brightest stars and  two terrific star clusters, plus the two brightest planets. What backdrop for a brilliant meteor shower!

The red oval represents the area opf the sky from which the Perseid meteors appear to radiate – however, they can go in any direction from here and might appear any where in the sky. (Click image for larger version. Prepared from Starry Night Pro screen shot.) Here’s a quick guide.

Perseids – a quick guide

When:

The night of  August 11-11 starting about 90 minutes after sunset, but best after midnight. And if that night is likely to be cloudy, the next night of August 12-13 might prove to be just as good, but the best chance looks like the 11-12. (There’s no doubt you should see meteors either night – but there is doubt as to exactly when the shower will peak.)

Where:

Any place you have a clear and dark sky – the more horizon visible the better, but in truth you can only look in one area at a time, so a clear, dark sky to the northeast is best. While a Perseid meteor can appear anywhere in the sky, your best chance to see  several will be to scan the sky to the northeast in the general vicinity of the “W” of Cassiopeia.  However,  you don’t have to fixate on one region. Get comfortable, look high in the northeast, and from time to time look around to different sections of the sky to enjoy the sights and stay alert. My most memorable Perseid skimmed the horizon to the north.

What can you expect to see?

Under the best conditions at the peak of the shower, you can expect to see between one and two meteors a minute! But I never seem to achieve those best conditions, so I don’t raise my hopes too high. I’m just sure I’ll see many more meteors than normal, but fewer than I would in a year when the Perseids are at their very best.  To put numbers to it, I’d be delighted if I averaged one every five minutes. For everyone, everywhere, the intensity of the annual Perseid “meteor shower” is in a down swing, but because we’ll have little interference from the Moon, this should be a better than average year.

Meteors and meteor showers are fun if for no other reason than they are a chance to see something happening in the sky. Much of what we look at doesn’t change – or rather changes so slowly we don’t notice the change. Meteors, on the other hand, demand that you be looking in the right place at the right time. Only on the very rare, very bright meteors do we actually have time to alert others and have them turn their heads and see what we see.  And what we see is a space event happening closer to us than any other natural one. What’s more, meteors can have real scientific value.  They are viewed by some as our cheapest “space probe.” They are relatively pristine bits of matter left over from the early days of the solar system and so can tell a story to those who know how to read them.

Meteors – “falling stars ” – can be seen any time. You don’t have to wait for a “shower” like the Perseids; you just have to be lucky. But they are most frequent at certain times in the year when the Earth happens to be plowing through a meteoroid-rich area.  We call this occasion a meteor shower. (For your dictionary: A meteoroid is a small bit of space rock that becomes a meteor when it collides with our  atmosphere and heats to incandescence as it descends towards Earth. When it gets here – which is rarely as anything except fine, incinerated dust – it is a meteorite. )

The reason for a shower such as the Perseids is that we are passing through the debris trail of a comet. Think about it. The general model for a comet is a “dirty snowball,” and as that dirty snowball nears the Sun it melts, and as it melts it leaves a trail of dirt particles behind it – particles that remain in orbit until something like the Earth sweeps by and captures some of them with its gravity.

The comet itself can vanish entirely – but the result is a river of space dust – a river that is most intense nearest where the comet actually was.  That’s why there are some years – the 1990s in the case of the Perseids – when the meteor shower is more intense than others.  Now we are in a period when we are passing through the trail of the comet that creates the Perseids at a point where that trail is relatively sparse – so there will simply be fewer Perseids than there were  15-20 years ago.

That trail is not encountered all over the sky. It collides with our atmosphere near a particular point in our sky. That point is called the radiant – you might think of it as a hole through which the Perseids fall – and in the case of the Perseids, it appears to be in the constellation Perseus.  But we don’t see all the meteors at this point. We see a meteor only when its collision with our atmosphere is intense enough to make it burn up. The faint meteors we see are made by a speck of dirt about the diameter of a pencil lead. The brightest ones are caused by something about the diameter of the pencil’s eraser.  In either case it will, for all practical purposes, burn up entirely in our atmosphere – 50 to 75 miles up – and nothing significant will remain for anyone to find on Earth. But exactly where it burns up is another thing. That’s why we will see a sudden flare – a falling star – anywhere in the sky.

And that’s awesome! Consider this: If someone struck a match 50 miles away would you see it?  Yet a grain of sand, hurtling into the atmosphere, shows us such a brilliant light we can’t miss it!

When you are watching for Perseids, you don’t have to look near the radiant point, though you will see more there.  A meteor can flare up suddenly anywhere and appear to draw a short (usually 5-10 degrees long) straight line across the dome of the sky. (Bright ones may actually leave a trail, which you can see for a few seconds with the naked eye or longer with binoculars.) If we trace a line backwards along the meteor’s trail we will see it comes from the area near the radiant point.

In the early evening, that Perseid radiant point is low in the northeast. That means nearly half the meteors that are radiating from it are happening below our eastern horizon. That’s why the shower is best in the early morning hours when the radiant is high in our sky. If the radiant is overhead, then we have nearly doubled our chances of seeing a meteor.

There are many meteor showers in the course of a year and some are better than others. The Perseids is one of the most reliable ones and happens to come at a convenient time for northern hemisphere observers when it is comfortable to be out at night, lying on the ground, and looking up.

Personally, I don’t like the word “shower.” It immediately gives the impression that what we are going to see will be more intense than what most of us actually experience. I prefer calling this a meteor “event.” But, we have been calling such events “showers” for years, and too often they are hyped in the press and then people are disappointed when nothing like a shower occurs. So keep your expectations realistic and you won’t be disappointed.

In the final analysis there’s only so much time you can spend lying on your back gazing at the starry sky; though I very much enjoy that time, it’s made much more enjoyable by knowing that at any instant there’s a heightened likelihood that I will see a bright meteor.  That – and the summer Milky Way – make looking for Perseids in a dark and moonless sky always worth the effort for me.

Get ready for the 2009 Perseid meteors – but don’t expect a shower!

When:
The nights of August 11-12 and August 12-13 starting an hour after sunset.

Where:
Anyplace you have a clear and dark sky – with as much horizon visible as possible.

Look:
Northeast – while a Perseid meteor can appear anywhere in the sky, your best chance to see  several will be to scan the sky to the northeast in the general vicinity of the W of the Cassiopeia.  However,  you don’t have to fixate on one region. Get comfortable, look high in the northeast, and from time to time look around to different sections of the sky to enjoy the sights and stay alert.

The W of Cassiopeia, rising in the northeast after sunset, is a good place to start looking for Perseids. The actual radiant point is below it in the constellation of Perseus. Click for a larger image. (This chart uses a screen shot from Starry Nights software which I have then annotated.)

The W of Cassiopeia, rising in the northeast after sunset, is a good place to start looking for Perseids. The actual radiant point is below it in the constellation of Perseus. Click for a larger image. (This chart uses a screen shot from Starry Nights software which I have then annotated.)

What can you expect to see?
More meteors than normal, but far fewer than you would in a year when the Perseids are at their best.  I will be happy if I see one every five to 10 minutes. For everyone everywhere, the intensity of the annual Perseid “meteor shower” is in a downswing and will be further reduced this year by competition from a bright moon. In North America the predicted shower peak comes at mid-day when, of course, none will be seen because it’s – well, day! That’s why it’s recommended to look either the night before or the night after the predicted peak of 18 hours Universal Time August 12.

The moon is especially bothersome because it will be near last quarter – bright enough to drown out many meteors – and will rise around midnight.  The shower is normally best seen after midnight because it is then that its radiant point is highest in the sky. So when the most meteors would normally be seen, there will be the most interference from the moon.

So, should you just not bother with the Perseids this year? No.  I certainly intend to take advantage of it. If the sky is clear on either night I intend to make them part of the reason to observe, but not the only reason. I won’t lie in a beach chair looking up most of the night as I have done other years.  Instead, if the skies are clear, I plan to head for the darkest spot nearby – Allens Pond Bird Sanctuary – and from there I will do three things:

  • Enjoy the summer Milky Way and the Perseids for the hour or two before the moon comes up and the skies are genuinely dark. During that time I will lie back in a rotating beach chair, binoculars at the ready, and look for Perseids.
  • After the moon rises I intend to enjoy a night full of planets and double stars, as well as the moon.
  • And as the icing on the cake, I’ll continue to keep my eye out for more meteors than I can expect to see on a typical night.

So what’s a meteor and do they really shower?
Meteors and meteor showers are fun if for no other reason than they are a chance to see something happening in the sky. Most of what we look at doesn’t change – or rather changes so slowly we don’t notice the change. Meteors, on the other hand, demand that you be looking in the right place at the right time. Only on the very rare, very bright meteors do we actually have time to warn others and have them turn their heads and see what we see.  But what we see is a space event happening closer to us than any other.

Meteors – “falling stars ” – can be seen any time. You don’t have to wait for a shower like the Perseids; you just have to be lucky. But they are most frequent at certain times in the year when the Earth happens to be plowing through a meteroid-rich area.  We call this occasion a meteor shower. (For your dictionary: A meteroid is a small bit of space rock that becomes a meteor when it collides with our  atmosphere and heats to incandescence as it descends towards Earth. When it gets here – which is rarely as anything except fine, incinerated dust – it is a meteorite. )

The reason for a shower such as the Perseids is that we are passing through the debris trail of a comet. Think about it. The general model for a comet is a “dirty snowball,” and as that dirty snowball nears the Sun it melts, and as it melts it leaves a trail of dirt particles behind it – particles that remain in orbit until something like the Earth sweeps by and captures some of them with its gravity.

The comet itself can vanish entirely – but the result is a river of space dust – a river that is most intense nearest where the comet actually was.  That’s why there are some years – the 1990s in the case of the Perseids – when the meteor shower is more intense than others.  Now we are in a period when we are passing through the trail of the comet that creates the Perseids at a point where that trail is sparse – so there will simply be fewer Perseids.

That trail is not encountered all over the sky. It collides with our atmosphere near a particular point in our sky. That point is called the radiant – you might think of it as a hole through which the Perseids fall – and in the case of the Perseids it appears to be in the constellation Perseus.  But we don’t see all the meteors at this point. We see a meteor only when its collision with our atmosphere is intense enough to make it burn up. The faint meteors we see are made by a speck of dirt about the diameter of a pencil lead. The brightest ones are caused by something about the diameter of the pencil’s eraser.  In either case it will, for all practical purposes, burn up entirely in our atmosphere – 50 -to-75 miles up – and nothing significant will remain for anyone to find on Earth. But exactly where it burns up is another thing. That’s why we will see a sudden flare – a falling star – anywhere in the sky.

And that’s awesome! Think about it a moment. If someone struck a match 50 miles away would you see it? Evena big, wooden kitchen match? How about amile away?  Yet a grain of sand, hurtling into the atmosphere, shows us such a brilliant light we can’t miss it!

When you are watching for Perseids you don’t have to look near the radiant point, though you will see more there.  A meteor can flare up suddenly anywhere and appear to draw a short (usually 5-10 degrees long) straight line across the dome of the sky. (Bright ones may actually leave a trail, which you can see for a few seconds with the naked eye or binoculars.) If we trace a line backwards along the meteor’s trail we will see it comes from the area near the radiant point.

In the early evening that Perseid radiant point is low in the northeast. That means nearly half the meteors that are radiating from it are happening below our eastern horizon. That’s why the shower is best in the early morning hours when the radiant is high in our sky. If the radiant is overhead, then we have nearly doubled our chances of seeing  a meteor.

There are many meteor showers in the course of a year and some are better than others. The Perseids is one of the most reliable ones and happens to come at a convenient time for northern hemisphere observers when it is comfortable to be out at night, lying on the ground, and looking up.

Personally, I don’t like the word “shower.” It immediately gives the impression that what we are going to see will be more intense than what most of us actually experience. I prefer calling this a meteor “event.” But, we have been calling such events “showers” for years and too often they are hyped in the press and then people are disappointed when nothing like a shower occurs.

In the final analysis there’s only so much time you can spend lying on your back gazing at the starry sky: though I very much enjoy that time it’s made much more enjoyable by knowing that at any instant there’s a heightened likelihood that you will see a bright meteor.  That – and the summer Milky Way – make looking for Perseids in a dark and moonless sky always worth the effort for me.

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