Stargazing: Birds in the sky and 'coral' on Mars

Stargazing with John Stapleton of Torbay Astronomical Society

June is the month when Astronomical Twilight never ends and so the night sky is never really dark.

Astronomical Twilight is defined as when the Sun lies between 12 and 18 degrees below the horizon. True night with dark skies occurs only when the Sun is more than 18 degrees below the horizon.

Astronomical Twilight, therefore, makes the observation of faint objects almost impossible at this time of year. However, bright point objects like stars and planets are still observable. Once again, there are few planets to see when the sky is dark.

The summer solstice - longest day - occurs on June 21 when we will have 16.26 hours of daylight!

In terms of the Earth’s orbit, the solstice marks the point (contrary to all common sense) farthest from the Sun. The Earth is actually closest to the Sun on December 21, the winter solstice and shortest day.

What makes it summertime in the Northern Hemisphere is that the Earth’s North Pole is tilted towards the Sun at this time of year. This is what causes the Sun to appear higher in the sky for longer, consequently bathing the Northern Hemisphere in a greater proportion of its heat and light than at other times of the year, giving rise to our summer.

At the winter solstice, the opposite is true. The Earth’s North Pole is tilted away from the Sun, the Sun never rises very high into the sky, days are shorter, and we receive a smaller proportion of its heat and light than at other times of the year, giving rise to our winter.

At the same time the exact opposite occurs in the Southern Hemisphere. While we are enjoying our summer, the South Pole is tilted away from the Sun and so is experiencing winter. When we are deep in our winter, the South Pole is tilted towards the Sun and is enjoying its summer.

Summertime in the Southern Hemisphere occurs when the planet is closest to the Sun and the South Pole is tilted towards the Sun. This is why countries in the Southern Hemisphere have hotter summers than those in the Northern Hemisphere.

Instead, look for patterns of bright stars. One that will soon dominate the summer sky is The Summer Triangle, a single asterism - a shape formed by stars but not recognised as a constellation - even though each star is actually in a different constellation.

The first three stars visible, overhead, on summer evenings are Vega, in the small constellation of Lyra, Deneb, at the short end of the 'Northern Cross', more properly known as Cygnus, the Swan, and Altair, in the constellation of Aquila, the Eagle.

This pattern became useful as a navigation aid for aircraft on night missions during World War Two as the long axis of the Triangle always points to the Southern horizon. It was named by an Air Force navigator and amateur astronomer called Patrick Moore.

In space news, NASA’s Curiosity Rover has photographed a coral-shaped rock on the surface of Mars.

This is believed to have formed at a time when liquid water existed on the red planet millions of years ago and minerals crystallized out of the water.

As I am old enough to remember the media hype and pseudo-scientific nonsense that arose over the so-called 'Face of Mars' when a rock formation was illuminated in such a way that the shadows appeared to form a visage even though by the next pass of the probe over the same site, there was nothing to see because the formation was then under a different illumination, I would like to clearly point out that this coral-like formation is only the size of a 10p coin.

The Star Chart

The sky will look like the chart on June 5 at 9pm and again on June 21 at 8pm. And four minutes earlier on each successive night e.g. 8.56 on June 6.

To use the chart hold it above your head while facing south so that you can look directly from the chart to the sky.

Skynotes

Please note all times given in this article are in GMT so remember to add an hour to get the time in BST.

Sun: The Sun is never very far below the horizon at night throughout June and into July, so it never gets astronomically dark, and this is not the best time for observation of faint fuzzy objects. However stars and planets can still be observed particularly around midnight when the sky is at its darkest. The Milky Way is visible from dark sites stretching across the northern horizon.

Mercury and Venus: Both of these inner planets are closer to the Sun than the Earth so are never very far from the Sun, especially Mercury, which is not visible this month. Brilliant Venus is visible all night long in the west against the background of Taurus. On June 21, Venus will lie very close to a crescent Moon and will provide an interesting photographic opportunity. Because of our perspective view of Venus it shows phases like the Moon which can be seen through a telescope. J Hedley Robinson, the founder of the Torbay Astronomical Society, was a well-regarded observer of Venus and a pioneer in observing the planet and it’s atmosphere with coloured filters.

Mars: Mars is also not visible this month.

Jupiter: Rises in the east just before dawn - before 4am at this time of year. Jupiter is bright enough to be easily spotted if you have a low enough horizon.

Saturn: The ringed planet can also be found rising in the east just before dawn but is fainter than Jupiter because it is further away from the Earth. Saturn rises slightly earlier than Jupiter so will first appear in a slightly darker sky.

Uranus and Neptune: These planets are not visible this month.

Meteor Shower: There are no major meteor showers this month, but you could still see stray (sporadic) meteors.

Noctilucent Clouds: It may seem anachronistic for astronomers to be interested in clouds, but these rare apparitions are best seen at this time of year. Noctilucent clouds are so high (over 80 km) in the atmosphere that they are able to reflect sunlight even when the Sun is well below the horizon. The tiny ice crystals that make up the clouds reflect bluish-white light that stands out against the gloaming sky. They are typically seen 1½ to two hours after sunset low in the northwest or before sunrise low in the northeast.

Comet: There are no bright comets predicted this month.

The Full Moon occurs on June 4 with Last Quarter on June 10. New Moon follows on June 18 and First Quarter at the end of the month on June 26.

DIARY DATES

The next meeting of the Torbay Astronomical Society will be in September as the society is now in recess for the summer. For details of forthcoming and future meetings, visitors and prospective members are especially welcome, email the TAS secretary at astrosecretary@gmail.com