pete lawrence
The period from late May to early August presents an opportunity to see a rare display of noctilucent (‘‘nightshining’’) clouds (NLCS). These are the highest clouds on Earth, formed in a thin layer 82km up in the mesosphere. At this height, tiny ice crystals can reflect sunlight when the Sun is below the horizon as seen from the ground. As a result, NLCS appear to shine at night.
June and July are the best months for NLC spotting and if present, they can normally be seen close to the northwest horizon 90-120 minutes after sunset, or a similar time before sunrise low towards the northeast. They typically show a delicate wispy appearance, often with herringbone details, and shine with a white or electric-blue colour. An extensive display may be visible all night long.
NLCS were first reported around the time of the Krakatoa eruption in 1883. It was believed that volcanoes were linked to their formation, but it’s now known that many particles come from meteoroids vaporising in the Earth’s atmosphere.
The June solstice occurs at 04:24 GMT on June 21, so true darkness during June and July is in short supply. Fortunately, brighter objects such as planets and the Moon continue to produce impressive sights.
A small telescope pointed at Jupiter will start to reveal the complexities of the planet’s atmosphere, and an aperture larger than 100mm will show the vast anticyclone known as the Great Red Spot. This raging storm, several times the width of planet Earth, has been observed for at least 190 years and may be much older than that.
The even brighter planet Venus also appears close to the Moon on the morning of June 21, both rising in the east-northeast 80 minutes before sunrise. This can be quite a spectacle if clouds permit.
Saturn is also on view, reaching opposition on June 15, a time when it’s opposite the Sun in the sky. It currently appears rather low down as seen from the UK, in the southern part of the constellation of Ophiuchus the Serpent Bearer. This constellation is sometimes likened to an inverted flower pot. There is a faint V-shaped pattern visible off the northeast corner of the flowerpot, known as Poniatowski’s Bull. Now regarded as an asterism – an unofficial star pattern – this small collection of five stars did once have recognition as the constellation Taurus Poniatovii.
Close to this pattern lies Barnard’s Star, a close neighbour of the Sun lying just six light years away. The summer Milky Way passes through this region, heading south to the east of Ophiuchus, and passing through the small diamond-shaped constellation of Scutum the Shield.
The Milky Way immediately south west of Scutum contains some amazing deep sky objects. Here you’ll find M16, the Eagle Nebula, and M17, the Omega or Swan Nebula. M16 contains the star forming columns of gas imaged by the Hubble Space Telescope, “The Pillars of Creation”.
Continuing south, towards the Teapot asterism in Sagittarius brings you to another bright and large star cloud called M24, Delle Caustiche or the Sagittarius Star Cloud. Binoculars reveal around 1000 individual stars here. These objects give this region of sky a vibrancy in the summer months.