Posts Tagged ‘globular cluster’

The highlights in the sky this June are an opposition of Saturn on the 3 June and Mercury visible in the morning sky.

The Sun

As most of you know, June is the month when we have the longest day of the year, the Summer Solstice. This is when the Sun reaches as far north in the sky that it can go, and on this day it is overhead as seen from the tropic of Cancer. This year the solstice falls on the 20 June, and in Wales the days are quite long. On 20 June the Sun rises in Cardiff at about 4:55am and sets at about 9:30pm. This means that there is about sixteen and a half hours between sunrise and sunset. Compare this to the shortest day (the winter solstice), when there is only about eight hours between sunrise and sunset; the days are more than twice as long in late June compared to late December!

Although this means that the nights are at their shortest, June is still a good month to look at the night-time sky as there are several interesting things to see.

The Moon

In June the new Moon is on the 5th of the month, and the full Moon on the 20th. So, seeing the night-time sky in the days around the full Moon can be challenging, particularly trying to see any faint objects. On Saturday 11 June there is a conjunction between the Moon and Jupiter. A conjunction is when two bodies appear close together in the sky, and on this night they will be separated by 1.25 degrees from each other. For comparison, a full moon is 0.5 degrees across. They will become visible in south Wales by about 10pm when it is dark enough, over towards the west as they head towards setting at just after 1:30am.


On 5 June Mercury will appear as far to the west of the Sun as it can get. Some of you may have been aware that on 9 May Mercury passed across the disk of the Sun, known as a transit. Less than a month after that, Mercury has moved in the sky as it orbits the Sun so that it is now visible before sunrise. On 5 June it will rise at 4:13am in Cardiff, with the Sun rising at 4:57, giving you just over half an hour to catch a glimpse of this elusive planet. On 19 June Mercury will rise at 3:58 in Cardiff, and the Sun at 4:54, giving you nearly an hour to see it. Although Mercury is fairly bright in June, it is still very tough to see it as it will be low near the eastern horizon and the dawn light will quickly make the sky too light to see it. But, it is worth a go!


Mercury is visible before dawn in June. It reaches greatest western elongation on 5 June. By 19 June it will rise just under an hour before the Sun, so it is possible to catch a glimpse of it before the pre-dawn light gets too strong.


On 3 June Saturn will be at opposition, this means we will be passing it as we and it orbit the Sun. On 22 May Mars was at opposition, and has become considerably brighter in the sky over the last several weeks. This does not happen with Saturn, it is so much further away than Mars that it doesn’t really get any brighter as we pass it. But, it is certainly easily visible, and you can use Mars to find it. If you imagine a clock face, Saturn is about about 8 o’clock from Mars on 3 June. Saturn will be visible over the next few months. If you get the chance to look through a small telescope you will easily be able to see Saturn’s rings; this is one of the highlights of the Solar System so if you get the chance it is well worth it.

When you look at Saturn through a small telescope you should see something like this. You may also spot a dot of light near Saturn, this is probably its largest moon Titan, the only moon we know of in the Solar System with a substantial atmosphere. The rings are tiny particles of icy rock, tens of thousands of them in orbit about the planet. The origin of the rings remains a topic of scientific debate, but what you may not know is that Jupiter, Uranus and Neptune also have ring systems, although they are much fainter than Saturn’s.


Saturn as it might appear through a small telescope. The rings are easily visible through even a very modest telescope.


Saturn as imaged by the Voyager 2 space probe which flew past it in January 1981.


Deep Sky Objects

One of the best deep sky objects (objects outside of our Solar System) to look for in June is Messier 13, one of the best globular clusters in the sky. A globular cluster is a huge collection of hundreds of thousands of stars which orbit the centre of our Milky Way galaxy. One of the most intriguing things about globular clusters is that they only contain old stars, and we believe that they were amongst the first structures to form when our Galaxy formed.


The globular cluster Messier 13 in the constellation Hercules (image credit Rainer Zmaritsch)

Messier 13 is in the constellation Hercules, and can be found by using the bright star Vega. If you imagine a clock face, Messier 13 (shown as “Hercules Cluster” in this image) is at about 2 o’clock from Vega. The constellation Hercules is also relatively easy to see, it has six bright stars which actually form a letter “H”, very appropriate that it should be called Hercules!


Where to find Messier 13 (the Hercules Cluster), a visually stunning globular cluster in the constellation Hercules. Hercules is an easy to find constellation, it has 6 relatively bright stars, and lies at about 2 o’clock from Vega. The 6 stars actually make the shape of a letter ‘H’.

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