The Night Sky in June
The Sun reaches its most northerly position in the sky at 11.07 BST on June 21, marking the June solstice. The UK’S period of night is shortest at this time. The elliptical nature of Earth’s orbit causes a variation in our distance from the Sun over the course of a year. Our last closest approach, or perihelion, occurred on January 3 when, centre-to-centre Earth was 91,401,983 miles from the Sun. On July 6 Earth will be at its furthest distance, or aphelion, positioned 94,507,803 miles from the Sun.
The distance variation means our orbital speed around the Sun changes throughout the year too. At perihelion Earth is travelling at 67,779mph while at aphelion its speed reached a minimum value of 65,542mph. The Sun’s actual location varies slightly from its mean position, that which would occur if Earth’s orbit were circular. If you place a stick in the ground and mark the position of the end of its shadow at the same time of day over a year, the resulting shape is known as the solar analemma.
The variation between the apparent position of the Sun and its predicted mean position is known as the Equation of Time. Sometimes represented as a graph on the face of a sundial, this provides a way to correct the apparent time indicated on the sundial’s face back to mean, or clock, time. The Equation of Time means the earliest sunrise and latest sunset are offset from the solstice by a few days. This year the earliest sunrise occurs on June 17 at 04.40 BST, and the latest sunset on June 25 at 21.43 BST. Both times assume you’re viewing from the centre of the UK and have a perfectly flat horizon.
The Sun’s disc never drops far below the northern horizon at this time of year – something that becomes obvious the further north you are.
From mid-northern latitudes, Noctilucent Clouds (NLCS) are most commonly seen during June and July, low above the northwest horizon, 90-120 minutes after sunset, or a similar time low above the northeast horizon before sunrise.
Being seven times higher than regular clouds they can still reflect the Sun’s light despite it being below the horizon as seen from the ground. Their name literally means “night-shining” for this reason. If visible, NLCS typically show an electric blue colour. They are linked to astronomy because the seeding agent around which their tiny ice particles form is meteor dust. The NLC window may provide opportunity to catch a view of Venus apparently embedded within them low above the westnorthwest horizon shortly after sunset. Planet Mercury may also be seen closer to the northwest horizon from mid-june onwards. A thin crescent Moon sits between both planets on the evening of June 15.
Saturn is visible later in the evening and reaches opposition on June 27. Opposition is the time when a planet is located on the opposite side of the sky to the Sun, providing us with our brightest and largest view (through a telescope).
Away from the opposition, the particles that make up Saturn’s rings are seen from an oblique angle. Here we see a mix of illuminated particle faces and the shadows they cast on the particles behind them. At opposition, the view becomes more direct and we see more of the bright sunlit faces, with the shadows mostly hidden from view. Consequently, Saturn’s rings appear to brighten a few days before opposition, reaching peak brightness at opposition and then fading in the days that follow. This is known as the Seeliger, or Opposition, effect.