In search of the Galactic Plane

Almost everyone knows that the galaxy our Solar System is located in is called the Milky Way but a lot of people don't realize that you can actually see the Milky Way from the comfort of our Earth-bound back gardens. Well, obviously not the whole of the Milky Way galaxy - you'd have to be well outside of the galaxy, in a starship or some alien observatory in the Andromeda Galaxy, to do that. What we can actually see is the Galactic Plane of the Milky Way - the plane in which the majority of our galaxy's mass lies. 

Every star you see in the night sky is part of the Milky Way but you can also see a hazy band of 'milky' white light (hence the name of our galaxy) some 30 degrees wide arcing across the sky.   The Galaxy appears like a band (as seen in the photograph below from the European Organisation for Astronomical Research in the Southern Hemisphere in Chile) because that's what you see when a disk-shaped structure is viewed from inside. And you don't even need a telescope to see it - your trusty Mark 1 eyeballs are the best optical equipment to use.

However, if, like me, you are living in or near a city such as Cambridge or even a suburb such as Longstanton, the chances are it will be almost impossible to see. The light pollution from from street lights, buildings, houses and vehicles will completely wash out any of the Milky Way's white 'haze' (not to mention a good number of normally visible stars). Bright moonlight would make it even more difficult to see and if it's cloudy, well, you might as well go inside and watch the 'The Sky At Night' on the BBC instead.

To illustrate, the picture below was taken outide my house last night, with a bright half moon, some hazy cloud and the scorching lights of the A14 and a guided bus station blazing away just a few miles away - not to mention a b*$$&y street light just in front of my house. Looking westward at this time of the year, I should be able to see the Galactic Plane cut across the constellation Cygnus and Cepheus. However, as you can see the photograph below, all you'd probably be able to see in these very usual conditions would be the bright line of stars at the bottom that form the cross Cygnus and a handful of Cepheus' stars at the top.

In better seeing conditions, with no moonlight or cloud, such as in the picture below, you'd probably be able to resolve many more stars - but the light pollution would ensure that you'd still be hard-pressed to see any hint of the Galactic Plane.

However, the Galactic Plane IS there! I'd taken 36 exposures of that same scene in my first photograph above and 'stacked' them using astronomical imaging processing software so that I'd be able to squeeze every tiny photon of light captured in each exposure (the technique is explained in my earlier blog 'Let there be Light!'). The resulting image is shown below:

You can probably now just about make out a band of hazy stars concentrated in the middle of the picture. You might also see some dark 'clouds' within that band. Dark regions within the band correspond to areas where light from distant stars is blocked by interstellar dust.

The Garnet Star

You may have already read my earlier blog about the colour of stars and how stars that may appear white to the naked eye may actually be rich reds or cool blues when viewed with binoculars or telescopes. I'd also written about some of the more spectacular of those coloured stars, such as the yellow and blue couple in Albireo and the flashing red of the supergiant Beletelgeuse. Last night, I had a look at another red supergiant which has the distinction of not only being one of the largest stars that is visible to the naked eye but is also the reddest of the naked eye stars in the night sky. That star is Mu Cephei or more popularly known as Herschel's Garnet Star.

The star is named after Sir William Herschel, the astronomer who, in 1781, discovered the planet Uranus.  Herschel described Mu Cephei as "of a very fine deep garnet colour and ... a most beautiful object, especially if we look for some time at a white star before we turn our telescope to it, such as a Cephei, which is near at hand."

That Garnet Star is located in the constellation Cepheus and in the still photo I took above, you can see it in the top left hand corner, flanked by the contrastingly white Alpha Cephei - the brightest star in the Cepheus constellation - in the bottom right corner. Although it is one of the largest and most luminous stars in the night sky, it will only appear as a faint star to the naked eye - and it is not likely you'll be able to see its distinctive red colouration with the naked eye. This is because it is very far way - it's distance from the sun is too far to measure with any degreee of certainty but it is estimated to be about 2,400 light years (when compared to, say, that other red supergiant, Betelgeuse, which is 'just' 640 light years away).

Nevertheless, despite its great distance away and its faintness to the naked eye, it is bright and it is huge - at nearly 2000 times the radius of our sun, it's as wide as the radius of Saturn if it were to be plopped by a huge cosmic hand right in the middle of our Solar System. And it is 100,000 times brighter than the Sun - one of the most luminous stars known. Seen through binoculars or a telescope, Herschel's Garnet Star is one of the night sky's loveliest sights. The still photo above does not do justice to the its true brilliance and luminosity, as it actually does look like a glittering red garnet suspended in the blackness of deep space. The video I took below might give you just a glimpse of what you would actually see through an optical device.

Finding the Garnet Star should be relatively easy. Around this time of the year, it should be somewhere to the west-northwest in the northern hemisphere. Face that direction, look for the distinctive 'W' of the Cassiopeia and look for the first relatively bright star south of that constellation. This should be Alpha Cephei. Then look for a distinctive, tight triangle of stars that is formed by Delta, Zeta, and Epsilon Cephei (in the top left part of the photo below). Herschel's Garnet Star should be somewhere between  Alpha Cephei and that triangle.

Actually, Delta Cephei (the star at the apex of that triangle) is even more famous than the Garnet Star. This is because Delta Cephei is one of the few easily-visible variables stars - its magnitude (a measure of 'brightness') changes periodically. The Garnet Star is a variable star too, with its magnitude varying from a bright +3.62 to a faint +5 every 2 to 2.5 years. But Delta Cephei's magnitude varies from +3.5 to +4.3 and back, over an amazingly regular period of 5 days 8 hours 47 minutes and 32 seconds. It is, in fact, so accurate that the star acts like a natural clock - but more about Delta Cephei and the other Cepheids in another of my nocturnal outings!

All photographs on this page  © Sabri Zain 2012.

The Planets by Rishon Sabri

Let there be Light!

Many people  probably bought their first amateur telescope after being inspired by stunningly detailed and colourful pictures from NASA's Hubble Space Telescope of nebulae and galaxies, such as the image of the Andromeda Galaxy above. And those people who peered into their tiny little refractors at Andromeda were probably bitterly disappointed when they found that all they could see in their eyepiece was a small, barely visible fuzzy patch of grey in the sky - if they could see anything at all. Even with relatively large amateur telescopes, it would be impossible for you to visually see in your eyepiece the kind of detail you would see in those NASA pictures - Andromeda would more likely appear as a dim patch, as pictured near the centre of my image below.  

The problem is that a telescope's lens can just gather a limited amount of light - especially when the object you're looking at is 2.5 million light-years away. At those kinds of distances, every photon of light counts and using cameras and imaging devices to capture even that tiny amount of light will make you lose even more of those precious photons. One way you can help overcome this problem is to process the digital image you obtain with a graphics processing programme such as PhotoShop to manipulate gamma, brightness, contrast, midtone, highlight and shadow levels, so that you can obtain a more enhanced image, such as the one below.

 However, the most effective way to enhance such images is to do what the professional astronomers with building-sized telescopes do to their own images - mesh together multiple images of of the same region of space to allow every photon of light recorded to be used and to provide a brighter, more detailed image. With us amateurs, we would take many pictures of our target (or use the individual frames of a video taken through the telescope with a webcam or CCD imager) and then to produce a 'stack' of the images. This 'image stacking' would then produce a single image that comprises either the sum, or the average, or some value in between of the individually stacked images. Stacking images is a well-established method for increasing the signal-to-noise ratio in a series of similar images. Every photon of true "information" recorded in every frame taken is captured and used in the final image, while random noise is dropped out

For example, multiple exposures of the image above, when 'stacked' with software such as Registax or 'RotAndStack', will produce the image below, where the much more of the Andromeda Galaxy's spiral disk can be seen and even the fainter stars not evident in the previous image shine gloriously through. And with something the size of Andromeda, you don't even need a telescope to produce images such as these - the image below was taken by a modest, ancient Olympus Camedia C-4040Z digital camera (40 quid on e-Bay) without the aid of a telescope.

The first step is to take, say, 48 exposures of the target of, for example, 8-16 seconds (or long enough for a good exposure to light but short enough not to produce star trails or too many 'hot' pixels on the image). Obviously, the more exposures taken, the better - depending upon how much observing time you have and how cold out it is that night. Don't take too long, though - your lenses might mist up or even frost up if exposed to the night air too long. You then run your image stacking program, such as Registax, and load all 48 exposures into the program. You will then need to chose some prominent stars or region as common alignment points (the boxed area in the picture below) so that all 48 images can be properly aligned and stacked together, using these alignment points as the points of references.

The program will then compare the alignment points of each of the 48 images to make sure they are properly rotated and placed in each 'layer' of the final stacked image. Once aligned and optimized, you can proceed to 'stack' each of the 48 images into a single output image.

Once the 'stacked' image has been produced, most stacking programs allow you to do further processing on the image to enhance it even more. Once you're happy with your image, all you need to is then save your picture and your tiny 80mm refractor or humble digital camera has now produced an image that would put a monster telescope 10 times its size to shame!

V is for Hyades

“V” may be for Victory, but it’s also the shape of one of the closest star clusters to Earth: the Hyades. Located in the constellation Taurus, finding this star cluster is easy-peasy - the brightest stars in the cluster make a distinctive 'V' or arrowhead shape and it is located south of its more well-known half sisters, the Pleiades, or Seven Sisters. The Hyades are 'only' about 150 light years from our solar syste - the Pleiades, for example, is three times farther or about 400 light years away.

The first star to catch your eye in that V shape will be a bright orange spark to the bottom left - the 'eye' of the Taurean bull. This is the red giant pictured below, Aldebaran  - a star that is approximately 50 times the diameter of our Sun.   Aldebaran is actually not part of the Hyades star cluster at all. It’s only 65 light years from Earth (that is, almost halfway between us and the Hyades) but coincidentally happens to be in the foreground of our line of sight to the Hyades. That said, without Aldebaran, the cluster would be a little disappointing; so it does adds a little lustre to it and helps anchor the overall shape of the cluster for us astronomers. The name Aldebaran actually comes from Arabic (al-dabaran) and translates literally as "the follower", presumably because this bright star appears to follow the Seven Sisters in the night sky - in which case, perhaps 'Stalker' might have been a better word! For the Seris of northwestern Mexico, Aldebaran is said to provide light for the seven 'women' giving birth. And those Trekkers among you probably know of one of Scotty's favourites, the Aldebaran whiskey and the Aldebaran mud leeches used by the Denobulan Dr Phlox!

The Hyades contains about 20 orange and blue stars that are perhaps visible to the naked eye; If you like double and binary stars, you'll love Hyades - as you can see from the image below, the Hyades cluster has quite a few pairs in it. Even with average eyesight, you can probably make out and split with tree pairs without any difficulty - the Sigmas (just a little to the south pf Aldebaran), the Thethas (to the east) and the Kappas (way up north).

While  the cluster appears like the letter “V” from our perspective on Earth, its true shape is approximately spherical.  And while we may be able to observe about 20 stars visually, the Hyades actually contains some 300-400 stars. Below is a 'stacked' enhancement of the image above, which clearly show a lot more stars than is evident at first.

All photographs on this page  © Sabri Zain 2012.

My date with the Seven Sisters

The Pleiades is an open star cluster in the constellation Taurus and, at this time of the year, makes its entrance in the north eastern skies of the northern hemisphere round about midnight. Popularly called the Seven Sisters, it is among the nearest star clusters to Earth and is the cluster most obvious to the naked eye in the night sky.

These stars are so clearly seen in the night sky that even those who do not dabble in astronomy can easily spot them - at least 6 or 7 bright stars, gathered in a region only a bit larger than 1 degree, are clearly seen with the naked eye. See the little cluster of stars near the bottom right hand side of the picture below?

The Pleiades have been used for testing eyesight from antiquity onward. In good observing conditions, an observer with average sight can see 6 stars. What about people with excellent eyesight? Maestlin, the teacher of the astronomer Kepler, saw 14 stars; he had drawn 11 stars on charts of the Pleiades before the telescope was invented! The well-known English observer Denning also saw 14 stars in the cluster. Madame Airy (the wife of a well-known nineteenth-century English Astronomer Royal) could see 12, while the English amateur astronomer William Dawes, who was in his time known to have extraordinary eyesight, saw 13 stars in the cluster. How many can you make out in my picture below?

If the Pleiades seem charming with the naked eye, they are truly breathtaking when viewed through a small low-powered telescope  or binoculars! The six stars are suddenly joined by numerous fainter ones, making the field of the cluster literally overflowing with stars, as you can see in my image below. Investigations of the cluster have shown that it may actually contain approximately 500 stars.

If I'd always felt slightly deprived because of the relatively low magnification of my telescope set-up, when observing the Pleiades low magnification becomes an advantage. The large field of view of a small refractor offers a panoramic view of this splendid group. With larger amateur telescopes or at high magnifications, we somewhat lose the magnificent feel of this cluster. Below is an image of the centre of the Pleiades taken at high magnifications.

In Greek mythology, the Pleiades were the seven daughters of the titan Atlas and the sea-nymph Pleione - Maia (the eldest), Electra, Taygete, Alcyone, Celaeno, Asterope and Merope (the youngest). However, because most people can only see six of the Seven Sisters, this has inspired legends of the “Lost Pleiad.” The most commonly told is that Electra - she’s shocked to see her home city Troy burning and hides her face. Another story says Merope wasn’t made as bright as the others because she married a mortal - the other sisters married immortals. Yet another story says she couldn’t fit in with the other sisters anymore and left for Hades. In another story, a thunderbolt hit Celaeno and she disappeared.

Intriguingly, other cultures such as the Aborigines of Australia and Iroquois of North America had similar legends of a missing seventh star. Some modern astronomers think that means there may actually have been seven stars easily visible a long time ago. The Greeks, the Iroquois, and the Aborigines may have told stories appropriate for their own cultures to explain why one vanished. If that’s true, one of the many Pleiades we see in a magnified view could have been the one that faded from naked eye visibility.

All photographs on this page  © Sabri Zain 2012.

Twin Terrors

Sunspots look like pimples on the face of the sun. In the case of the sun, though, it's acne problem occurs every 11 years, the cycle starting with a few pimples and building up to an outburst of blotchy rashes at its peak. Fortunately for me, the sun is currently in an active phase of its 11-year solar cycle. That's why last weekend saw the sun firing off one of the year's more spectacular solar eruptions, with super-hot solar filaments erupting and arcing into space and snaking between two huge sunspots - AR 1538 and AR 1540. Below is a video I took yesterday of these two sunspots. It may look like a single dark blob at first but careful inspection of the video will reveal that the 'blob' actually consists of a pair of sunspots.

Processing the video above with an astronomical image stacking program such as Registax reveals the two sunspots in greater detail, below. The two sunspots appear quite identical, like two evil twins spitefully spewing deadly plasma a (as well as a much smaller sunspot to the south) nd radiation towards poor little Earth. Sunspots are basically magnets - well, magnets with the magnetic force perhaps 8,000 times greater than the magnetic field around our entire planet. But just like any magnet, it has opposite north and south poles of positive and negative force. Sunspots therefore tend to form in pairs, just like the ones I captured in my images above - one with negative and one with positive polarity. The twins are often side by side, parallel with the equator and they rotate with the sun from west to east.

Zooming in on the sunspot with a 2X Barlow lens, you can see more clearly below the two dark spots (the central umbrae, where the magnetic field is approximately vertical to the Sun's surface), as well as the surrounding penumbra, which is lighter, where the magnetic field is more inclined.

Astronomers expect the current solar cycle, known as Solar Cycle 24, to peak in 2013, so probably lots for me to observe and video capture for quite a while yet - stay tuned!

All photographs on this page  © Sabri Zain 2012.