The Night Sky in June 2006

Looking at the night sky with the naked eye or using a small telescope can be fascinating, so each month these notes keep you up-to-date with unfolding events.

Maps of the current night sky can be seen by clicking HERE

Phases of the Moon in June

New Moon Sunday 25	First quarter Saturday 3	Full Moon Sunday 11	Last quarter Sunday 18

Click HERE to see the phase of the Moon on each day of the month.

 

Monthly Highlights

Can you believe it ... June is already upon us, heralding the approach of mid-summer. This year, as with most, the 21st marks the summer solstice or longest day. This is the day when the Sun reaches its highest point in the sky for the whole year - but more about that later. On the negative side, it also means that the Sun is never far below the northern horizon during the night, so it doesn't really get dark enough for a good look at the stars - around midnight would give you the best chance. If you do get to stay up that late, then you may be able to spot one of the following monthly highlights:

June 16th - Pluto at Opposition

At around 5pm on the 16th, our solar system's most distant officially recognised planet, Pluto, will reach the point in its orbit known as opposition. This means that it will be on exactly the opposite side of the Earth to the Sun, and can thus be seen due south around midnight GMT (Greenwich Mean Time) or 1am BST (British Summer Time). To be honest, there is no chance of seeing Pluto with the naked eye, but it might be an interesting project to see if you can track Pluto down using the dedicated Search for Pluto project within the Go Observing section of the NSO website.

In brief, the project aims to take 2 or 3 observations in the direction of Pluto on the same night, and as stars are relatively fixed in the night sky, any object that moves between images must be much closer to us, i.e. a planet or an asteroid, but in this case Pluto.

June 21st - Summer Solstice

The summer solstice, or mid-summers day, is the point during Earth's orbit around the Sun when we (in the UK) experience the longest period of daylight and hence the shortest night. The change in the length of daylight is all down to the tilt of the Earth in relation to the Sun, but without such a tilt we would have no seasons. Solstice literally means a stopping or standing still of the Sun. In summer (June 21st) it marks the point where it stops rising and in winter (December 21st), where it stops falling.

The above UK-based animation shows the average height of the midday Sun for each month of the year. In winter, the Earth tilts away from the Sun and thus it appears low in the sky at noon. In summer the tilt is toward the Sun such that it rises much higher and sticks around longer. Although the solar peak is in June, the warmest months tend to come in July and August. The reason being that the energy received during the summer months is stored in the soil, buildings, water and rocks. As more energy is added, this thermal store continues to build beyond June and peaks during July and August, before reducing again as we approach winter.

Remember that whilst we are enjoying the longest day in the northern hemisphere, the reverse is true for countries in the southern hemisphere like Australia and South Africa, where their winter is at its worst during June, July and August.

The Planets

Click HERE and start the Electric Orrery to see where all the planets are today in relation to each other.

Mercury Mercury starts the month as an evening object, setting in the west-northwest a good 90 minutes after the Sun. Having said that, the summer twilight is longer than in winter and its orange afterglow makes it hard to identify the planet. Mercury will reach greatest elongation (separation from the Sun) on 20th June before slowly making its way round between us and the Sun around the 18th July. Unfortunately, because Mercury is always low when the Sun is about, it is one of those objects that the Liverpool telescope cannot safely observe. Venus Venus continues to move away from us on the inside track and will remain a morning object and brightest planet for most of 2006, finally passing behind the Sun in late October. Having reached greatest elongation (separation from the Sun) in late March, early birds can spot Venus around 80 minutes before sunrise. Why not use the electric orrery to see how Venus remains a morning object over the next few months. Mars Mars remains visible throughout the month but continues to diminish in size and brightness as Earth moves away. It can be found high above the western horizon shortly after sunset and sets in the northwest close to midnight. Mars continues to move around behind the Sun and will reach superior conjunction (other side of the Sun to Earth) around mid-October. Now only slightly brighter than stars around it, Mars will be noticeable only by its slightly red hue and the fact that it moves from night to night. We can still observe Mars using the Liverpool telescope, but sadly it will be another 16 months before we get really detailed images again. Jupiter Jupiter remains the best target to observe after passing opposition (the other side of Earth to the Sun) early last month. This majestic gas-giant planet can be found high above the southern horizon close to 11pm and will remain close to its brightest throughout the month. Because of the short nights at this time of year, Jupiter both rises and sets during daylight. Why not use Go Observing to obtain an image of Jupiter and see if you can capture its elusive red spot or storm cloud features on its surface. Saturn Saturn continues to decrease in size and brightness as we move slowly away. At the start of June, it can be found high above the western horizon shortly after sunset, just to the left of Mars. As the Earth rotates, it chases Mars over the northwest horizon, setting around 12.30 am. This moves back to midnight by the end of the month. Although still just about visible to the Liverpool telescope, you would be better off waiting until the end of this year to get a decent image of Saturn, after we have passed around the back of the Sun during August.

Constellation of the month

Each month, new constellations are highlighted for you to identify in the night sky.

This month we will be looking for the small constellation of Libra, the Scales, low above the southern horizon around midnight. In Roman mythology, the constellation originally formed part of the claws of the scorpion (Scorpio). It is the youngest of the Zodiac and the only one not to represent a living creature. In later Greek mythology, the constellation, which looks vaguely like a set of scales, was considered to depict the scales held by Astraea (identified as Virgo), the goddess of justice. Libra is the Latin word for balance.

June Night Sky

Apart from being one of the constellations of the Zodiac through which the Sun passes, Libra is famous for containing one of the closest triple star systems in the solar neighbourhood - a system known as Gliese 570. Also known as HR5568 this trinary star is about 19.2 light-years away and consists of an orange sun-like main star, two smaller red dwarf companions. Together with a more recently found brown dwarf (more about those later), these all move in a slightly elliptical orbit that lasts around 2,130 years.

Stars come in all different sizes and colours. Blue stars tend to be large and hot, whereas smaller, cool stars appear red. Our Sun is referred to by astronomers as a yellow dwarf and sits somewhere between blue giant and red dwarf stars. Brown dwarf stars are cooler again but thought too small to be proper stars, and infact have more similarities to gas-giant planets like Jupiter.

Mythology: Libra

In ancient times the stars of Libra, the scales, were sometimes intermingled with those of Scorpius by the Greeks, but they have always been considered as a separate group by the Romans. This zodiacal constellation is associated with balance - balance of both nature and of justice. Some 3000 years ago, the Sun entering Libra marked the beginning of Autumn, when days and nights were of equal length, i.e. balanced. In addition, Roman astrologers considered that the constellation represented the scales held by Astraeia, goddess of Justice.