The July Sky

Well, as the thermometers on the mainland can tell you, it now really is summer. Madeleine and I had a blissful week on the Island since I last wrote this column, and I dutifully followed my own advice and re-visited Lobster Cove at night. It is a superb spot from which to view the southern half of the sky, with quite good visual access to the west and east as well. For headland viewing of the east and the northern sky, however, I realized that the only practical way to do this is by arriving at the headland while it is still light. If you are warmly dressed, and are a patient soul, then you can let darkness surround you in safety, and can look at another quarter of the heavens at your leisure. A good flashlight will immediately show you your road back from Burnt Head or Whitehead, but I would not recommend trying it from Black Head, where the headland is quite a distance from the end of an easy path.

And what is there to see in July? Well, I promised to introduce you to the summer triangle once summer was properly established, so we’ll start there.

Eyes Only

I am going to stop using the words "Starsketch" and "Starphoto" in this column. The made-up words are almost certainly confusing, and I shall simply use "Sketch" and Photo" from here on. (I will also re-name all the sketches and photos shown to date to match this change, but keep the sequential numbering system as before). So, let’s begin with Sketch #13.

As you will see from my sketch, the "Summer Triangle" actually consists of the brightest star in each of three constellations:

Vega, met last month in the constellation Lyra, the Lyre;

Deneb in the constellation Cygnus, the Swan;

Altair in the constellation Aquila, the Eagle

These three stars will dominate the sky around the zenith during evenings for the next three months, so we’ll use them for finding our way to other interesting sky sights. But first you want to be sure of finding them, so look directly up, and then slightly towards the east from the zenith, i.e. the point immediately overhead. You will see Vega, familiar if you were with me last month, a very bright, blue-white star. Now face east, and then hold your hand above your head at a full arm stretch, with your fingers spread wide and with the thumb and fifth finger dragged down a little.

If you put the tip of your middle finger on Vega, the tip of your thumb will be quite close to Deneb, and the tip of your fifth finger will be quite close to Altair.

The three stars themselves are of interest. Last month I wrote about Vega, 27 light years away, almost 3 times the diameter of our sun but – being much hotter – about 60 times brighter if one could see it from the same distance. Deneb is another kettle of fish all together. While not as bright as Vega when seen from the earth – Lobster Cove, to be specific -- it is actually 20,000 times brighter than Vega, or 60,000 times as bright as our sun! It is also 60 times the diameter – not as big as Antares, which we also met last month, but intrinsically six times brighter than that behemoth. Deneb is one of the two greatest super-giant stars known to astronomers, the other being Rigel in Orion, which we will meet towards the end of the year.

Altair, meanwhile, is about the same brightness as Deneb from Lobster Cove not because it is huge or intrinsically bright, but because it is very close, astronomically speaking. At about 16 light years distance, it is among the closer stars of our acquaintance, 10 times brighter than the sun if seen from the same distance, and about 50% larger in diameter.

Before you reach for your binoculars for the next part of our monthly tour, I want to show you a charming little constellation called Delphinus, or The Dolphin. Pretty to the naked eye, and beautiful in binoculars, this gem lies to the northeast of Altair (Sketch #14). Just as a good cartoonist can give the impression of a person in a few strokes of pen or brush, a good Someone can evidently give the impression of a tiny dolphin with just a few stars, when laying out the universe for viewing from Lobster Cove in 2001.

With Binoculars

Well, there is a feast to be had this month, and I don’t know where to start! I guess I always like to start with the moon – it IS our closest planet, and we don’t have to send a billion dollar space craft there to see its surface features. The moon will be about full or a bit past full when you read this, and there will be a new moon -- astonomer-ese for no moon! -- on about the 20th of July.

Thereafter, a new thin crescent will start to grace the evening sky just after sunset, setting about 40 minutes later each evening. I love this phase of the moon, and I sold more prints of Photo #9during my small Boston astro-photo showing than of any of the exotic galaxies, nebula, star clusters or exploded stars that I thought would be the, er, stars of the show. I guess the moon invites a familiarity that never breeds contempt.

But now to sterner stuff. Last month, I showed you where to find the star cluster plus nebula known as M8. There, new stars are being born almost as we watch. But elsewhere in the sky are clusters which have "grown up", blowing away their clouds of hydrogen gas. Several of these can be seen with your binoculars this month, in the area under discussion. M39 is an example – a rather sparse group of stars, it still looks pretty in binoculars. See Sketch #15 to locate the cluster, a patch of stars behind the tail of the swan, about half a swan-length away.

Another remarkable sight awaits you in the cluster known officially under a separate numbering system as Col. 399. This unemotional description is much less used in amateur star gazing circles than the more friendly "Coat hanger cluster". The description is perfect – find this cluster with your binoculars, and there you are – a coat hanger in the sky, all decked out with lights! Sketch #14 will help you find it, not too far from Delphinus or from Aquila.

Finally, return to the southern horizon. Last month we found M8, as I noted above. This time, look beside the Sagittarius "teapot", to the right, about half a teapot width away, to find the glorious open cluster M7. (Sketch #16) You are now looking in the direction of the center of the Milky Way galaxy, by the way. Finish this visit to Sagittarius by going above the teapot and counting how many clusters you can see within two teapot heights. I reckon you should see at least nine in this densely packed region, all of them embedded in so many stars as background that you will begin to have some slight feeling for the fact that our own Milky Way galaxy alone contains well over one hundred thousand million stars.

Through the Telescope

I don’t think there is much question as to where we should start this month. Let’s follow the binocular trail, and begin in the "teapot" asterism in Sagittarius. I showed you what M8 looks like in the telescope last month, and this month I want you to point your telescope higher in the sky to find M16, the "Eagle Nebula" in the constellation Serpens, the Serpent. Using your lowest power eyepiece for hunting, follow the line of epsilon and delta Sagittarii for 3.5 times the epsilon/delta distance. Then scan slowly to the right. (Sketch #16). You will find a fine cluster, with light glowing around some of the stars in (very roughly!) the shape of an eagle. But if you can hook on a camera, and know how to take about a one-hour exposure of the cluster using high-speed film, or a charge coupled device (CCD), what a picture you will discover! (Photo #10). This is the star-birth area photographed so magnificently by the Hubble telescope a couple of years ago, and the region is still splendid in a photo taken with a much more modest, earth-bound telescope. If you look at my photo, you will be able to see a dark little figure, almost certainly female in form and posture, holding some kind of parchment and standing in front of a throne. Astronomers, who can be quite romantic when they are done with their measurements and calculations, call her "The Queen of the Skies". She is actually a dust cloud obscuring part of the surrounding hydrogen glow. She is about 2 light years in height, so if you want to say you have seen a photo of a light year, be my guest! The whole nebula and star cluster is almost 70 light years across, and the entire scene is about 8,000 light years away.

Now go back to M8. Using your lowest power eyepiece, scan with your telescope so that M8 tracks around the edge of your field of view. At some point you will see another, smaller cluster, with a much fainter surrounding green-gray glow, fitting in your field of view. This is M20, the "Trifid Nebula", so named for its three-petal appearance in photographs. If you can carry out astro-photography, it will take about an hour using high speed film to capture a photo that shows detail. But, pray to the sky-gods that you do not suffer my fate: I had guided my 11" Schmidt-Cassegrainian telescope for about 50 cramped minutes when – FLASH! A brilliant light zapped across my tracking field of view as a plane flew precisely between Nigel Harvey and the Trifid Nebula. The strange resulting picture is shown in photo # 11   Sheesh. From the photo, you can see that the glow that looked green-gray to our eyes, which cannot perceive color in dim light, is once again in reality the pink glow of hydrogen being energized by radiation from the nearby stars. Note also the ghostly blue "shadow" image, which is actually a separate cloud, this time of dust, which scatters and reflects the blue in starlight much as our sky scatters and reflects the blue in sunlight.

Finally, before leaving the area, see how many open clusters and globular clusters you can see around the "teapot". Terence Dickinson shows about 17 in his excellent book "Nightwatch", which I recommend to every amateur astronomer and every star-gazer who wants to go further than a casual glance at the sky. It is published by Firefly Books (U.S.) inc., at P.O. Box 1338, Ellicott Station, Buffalo, NY 14205. I am presently wearing out my second copy.

Our last visit this month is close to Aquila, the Eagle. As you can see from Sketch #14, there is an open cluster called M11 in the nearby constellation of Scutum, the Shield. The cluster is to my mind the most beautiful of all the telescopic open clusters, and is called the "Wild Duck Cluster" due to its appearance of a cloud of ducks, rather evenly spaced, flying together across the sky. (Photo #12) It can be seen as a faint haze in binoculars, but becomes impressive in a telescope of 4" diameter or more.

So there. That was July, that was. Be well, and go well, and we shall meet again next month on the path leading down to Lobster Cove.