July 2018 Moon

The Night Sky July 2018

I have to admit that I am not a big fan of the moon! Particularly the weeks either side of a full moon. It blazes out dazzling light and can drown out even the brightest of stars. A better time is when the Moon is New (no glare at all, this month 13th July). However, I am aware that without it we all may never have evolved and the tides it creates may have been instrumental in life emerging from the sea to the land. So fan or not, I’m glad it’s there! It is also a good target to view for those of you without telescopes, especially during the summer when dark nights are short. So this article is devoted to our closet celestial body.

The Moon.

The moon is thought to have been formed not long after the Earth about 4.5 billion years ago. No-one knows for sure how it was formed but the general view is that it was formed from the debris of a collision between the Earth and another large planet-sized body.

The Moon has retained the scars of being Earth’s shield and its own geological history for billions of years. There is no water to erode the surface or significant atmosphere to weather the landscape. Many processes that change the surface here on Earth are not present on the Moon. Had the Earth been exposed to the same bombardment from space, without our gravity, atmosphere and weather systems it would perhaps look like the moon today. The evidence of some craters are still present on Earth but not as obviously defined as they are on the moon.

The Moon’s rotation is locked as it rotates around the Earth, always showing the same ‘face’ towards us, called the ‘near side’. So we always have the same view and which can help us become familiar with its surface and features.

Looking at the moon you will see grey patches. These are ‘Seas’ (Mares) - large areas filled with solid lava rather than water. The most famous being the Sea of Tranquillity, where man first set foot on the Moon. Even with the naked eye you can see craters on the Moon. This is astounding as it’s a quarter of a million miles away. One of the easiest to spot, Tycho is a 53 mile wide crater, in the southern part of the moon. (roughly the distance of Embsay to York, see what this would be like in my diagram.) It has one of the brightest craters and is therefore one of the youngest. It is at the centre of an extensive ‘ray’ system stretching across the surface of the moon. Rays are streaks of debris that seem to come from some of the larger craters. Inside the Tycho crater is a high peak over a mile high that can be spotted with a modest telescope.

In the early years of medicine it was thought because the human brain was made up mostly of water that the full moon’s gravity befuddled your sanity (like the Moon affects the tides) and hence the word ‘lunatic’ was born. So beware the Full Moon of 27th July! You may think you are going mad as you see a very large reddened moon rising as the moon is eclipsed at 8.47pm for an hour and half (10.13pm). The red colour is the effect of the sun’s rays passing through our atmosphere and filtering out particular wavelengths as it hits the moon’s surface.

The Moon illusion.

The moon appears bigger when near the horizon because of an optical illusion. When the moon is high up in the sky there are no reference points to judge its size and humans are notoriously bad at judging vertical distance. Nearer the horizon, our brain perceives vertical distance differently as familiar objects such as trees or buildings are helpful points of reference. Also perspective can play tricks with your mind! (See diagram.) To this day no one can really agree on why this illusion takes place. Some people argue it is an illusion similar to the one in the diagram. What do you think?

On July 27th Mars is in opposition (see last month’s issue regarding ‘opposition’). I would not normally suggest viewing during a Full Moon but it should be a special evening. You should see Mars low in the sky with a full Moon being eclipsed very close by and to the right in the south beautiful Saturn. What a view!

June 2018 Saturn

The Night Sky June 2018

Of all of the things that have captured my imagination and interest in astronomy, my first sight of Saturn as a boy was breathtaking! I had seen it in books and magazines but from that moment I was hooked. Saturn is the second largest planet in our solar system and although other planets have been discovered to have rings, Saturn’s are by far the most spectacular. The rings are made from particles of ice and rock. Although the largest ring is 7000 times the diameter of the planet, the rings are thought to be only 30 feet thick on average. Saturn could hold 750 Earths and it is not very dense, indeed less dense than water so it would float! Currently it has 62 known moons - the biggest being Titan. There are only a few chances of observing Saturn with its rings so don’t miss it this month!

So here’s your chance to see it. Try to borrow a telescope or binoculars. Saturn will be low in the sky but easy to spot very early in June as it sits just below an almost full Moon in the early hours of the first of the month. Looking South over the quarry and through an average set of binoculars, it will appear like a star ‘with ears’ but observing through a telescope the rings will be clearly visible. Also, later this month, Saturn will be ‘at opposition’. This is a term which refers to where it is placed in relation to the earth and the sun. It will be directly behind the earth and consequently much closer to us rather than being in its orbit the other side of the sun. It will be low in our skies for the next few years.

The summer solstice occurs June 21st and with it brings the longest day. You would think that because it is summer and the longest day, the earth would therefore be closest to the sun. This is wrong. We are in fact almost at the furthest point from the sun. It is the tilt of the earth that gives us our seasons, not the closeness to the sun.

I know from personal experience how frustrating stargazing can be. Often the clouds or poor weather thwart all best laid plans. However, my interest in astronomy is more than stargazing . I like to research, read and plan my observations which I resort to when the clouds roll in and I wait for those beautiful clear night skies. Whilst it is wonderful to have those long summer days it does mean a much shorter period to star gaze as there is almost no total darkness. During this time it is a good to observe brighter objects such as the moon and other unique phenomena such as Noctilucent clouds. These are the highest clouds in our atmosphere, way higher than normal at around 50 miles high. They are so high that when the sun has set for quite some time afterwards at this height they still catch the sun’s rays. The angle and effect of the illumination produce a very bright electric blue colour on the clouds whilst all around you is in darkness! This only happens about a month either side of the summer solstice so watch out for it.

The moon for most parts of the year can wash out dark skies and any plans of observing faint objects. During these summer months it is a perfect target for observation. To get the best out of these observations try to pick a period when it is not a full moon (28th June) or a new moon (13th June). The terminator, the place where the moon is lit and the shadow starts, is a great target to observe. Through binoculars you will be able to see craters cast shadows and have a real sense of depth that will be lost when the moon is full. It is astonishing that on the surface of the moon are the remnants of the Apollo landing sites that record our journey to the moon almost half a century ago! I remember as a boy looking through my telescope trying to spot the sites and now realise why I couldn’t (see diagram!)

Next month I will cover some targets on the moon for you to try and spot.

May 2018 Hercules

The Night Sky May 2018

Constellation of Hercules.

On an early summer night, the constellation Hercules is a very dominant sight as it is one of the biggest constellation in the night sky. Heracles, the Greek version of Hercules, was famous for undertaking twelve tasks or ‘Labours’. As the new moon is on 15th May, it is a good time to spot what Hercules has to offer. Although the stars that make up Hercules are faint, here is the time and place to find it. Looking east over to Bolton Abbey from Embsay late on the 15th you will see Vega (remember Lyra from last month) and to the right of it is the constellation of Hercules. Not impressive at first glance. The ‘ body’ of Hercules is shaped like a keystone, his limbs protruding from each corner. There are many remarkable objects to observe in and around this constellation and in particular are two globular clusters Messier 13 (M13) and Messier 92(M92).

M13 has a more inspiring title, the Great Hercules Globular Cluster. It has about 1,000,000 stars grouped together still within our galaxy. It is really only possible to be seen by the naked eye on a dark clear night. It appears as a fuzzy, faint blob but get some binoculars and take another look! (See image). Edmond Halley (of Halley comet fame) was the first person to spot it in 1714. M92 is another cluster, although smaller and further away. See the diagram for their positions. I have marked other objects for you to discover on my diagram.

Jupiter and Venus

There are a couple of opportunities to spot planets with your naked eye this month and the moon will point to their location.

Looking north-west on 17th May at about 9.30pm, you can spot the very bright planet Venus as the moon passes by. Venus is quite unusual as it rotates in the opposite direction to most other planets and it has no moons. As it has a very thick atmosphere, you will not be able to pick up any features on its surface, even with a telescope or binoculars. But if you study Venus you will see that it has phases just like the moon. To Galileo this fact finally confirmed to him that we live in a sun-centred arrangement rather than everything revolving around the Earth. He was arrested and imprisoned for drawing this conclusion!

Later on in the month around 10pm on 27th May the Moon will appear to be very close to Jupiter in the south-east and will be easy to spot. Jupiter is the largest planet in our solar system with a mass two and a half times all of the other planets put together. Alternatively, 1,300 Earths would fit inside! With a pair of binoculars, you will be able to see four of Jupiter’s moons (two either side) appear as a set of tiny specks in a very regimented line. Their current positions and names are Callisto, Ganymede, Jupiter ,Io ,Europa. These particular moons, called the Galilean moons, were the first objects to be discovered orbiting something other than Earth or the sun. Currently there are 69 know satellites of Jupiter.

Your easy challenge this month is to spot Jupiter and Venus. Harder will be to try to see the moons of Jupiter (binoculars required!) The most difficult, but rewarding challenge will be to seek out M13 in the constellation of Hercules.