Stargazing: A sky full of surprises

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.  

The Summer Solstice occurs on June 21st, although the longest day is actually on 20th, when we will have over 16 hours of daylight! The Sun is now at the maximum of its 11 year cycle so, if you are able to safely observe the Sun, either with a purpose-built solar telescope or by projecting an image through binoculars or a telescope onto a screen, you should see plenty of sunspots. 

The solar maximum also increases the chances of our seeing the Aurora or Northern Lights from lower latitudes. There have already been large events in the atmosphere of the Sun (photosphere) ejecting material in our direction. 

The Aurora Borealis, or Northern Lights, occur when there are active areas on the surface of the Sun. These active areas are associated with dark spots known as sunspots. Although apparently dark in images taken with safe solar telescopes, these spots have a surface temperature of around 4000◦C and only appear dark in relation to the solar surface which has a temperature of over 6000◦C. These spots are also responsible for disturbances in the local magnetic field of the Sun, giving rise to the phenomenon of solar flares; huge loops of incandescent material that shoot out from the surface and into space. Whilst most of this material is held by the magnetic field of the Sun and falls back to the surface, particularly large spots, or groups of very active spots, can produce flares from which the material escapes the magnetic and gravitational field of the Sun. This material, travelling through interplanetary space is known as the “solar wind”. It is actually a stream of ionized particles ejected from the Sun’s surface. When this stream interacts with the Earth’s own magnetic field these particles are funnelled towards the “weak” points at the North and South Poles. These ionized particles then interact with gases in the atmosphere to produce the stunning colours seen in the Aurora Borealis and its counterpart the Aurora Australis.

As a caveat, extreme events, known as Coronal Mass Ejections, can produce enough electromagnetic radiation to wipe out all electronic systems in its path. If such a CME was to head straight for the Earth there is little we could do about it. Such events have been recorded in the past, fortunately before the advent of the widespread use of electricity, although Northern Canada experienced a widespread power blackout after a geomagnetic storm in 1989.

At the time of writing, astronomers are still awaiting the nova event predicted for the star T corona Borealis. This star is of a type that undergoes repeated nova-like explosions, brightening by some 10 orders of magnitude, and so the star has been  under careful scrutiny for many months. No less than four prediction deadlines have been passed with no sign of change in the star. We are currently within a prediction parameter that runs from “mid-February 2024 – September 2026” however, there was also a prediction made in 1946 that the so-called Blaze Star would erupt again in 2026-2027.  We will just have to keep all eyes on the sky and hope that it is not cloudy when it eventually happens.

Skynotes

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

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 may possibly be glimpsed low in the North-West shortly after sunset at the beginning of the month. Venus is close to the Sun rising at about 3am.

Mars:  Mars is visible low in the Western sky amongst the stars of Leo but should not be confused with the equally bright, red giant star, Antares at a similar position in the East. The name Antares actually means “the rival of Mars” because of its similar colour and brightness.

Jupiter:  The giant planet is no longer visible. 

Saturn: The ringed planet rises at about 2am this month and may be visible for a short while before sunrise. Saturn is seen against the background stars of Pisces.

Uranus and Neptune: Uranus is not visible this month and Neptune is a little higher than Saturn in the constellation of Pisces. . 

Meteor Shower: There are no major meteor showers this month, but you could still see stray (sporadic) meteors and meteors from a couple of minor showers; the Arietid shower from 14th – 24th occurs during the daytime and the Bootid shower which peaks on 27th. Neither are strong showers and produce few 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 1 ½ to 2 hours after sunset low in the Northwest or before sunrise low in the Northeast.

The First Quarter Moon occurs on June 3rd with Full Moon on June 11th.  Third Quarter follows on 18th, and the New Moon occurs on June 25th.  

Data supplied by Dale Giles, Observations Secretary of Torbay Astronomical Society

Diary Dates

The next meeting of the Torbay Astronomical Society will be our Summer Social at the Drum Inn Gardens, Cockington on June 21st, the Summer Solstice, at 2:00pm when we hope to be able to use the Society’s solar telescopes to view the Sun. Then, in September, when our new season of lecture and observational meetings begins. 

The forthcoming season marks the Society’s 70th (Platinum) Anniversary and we have filled the programme with top quality speakers, including Professor Chris Lintott and two other contributors to the BBC Sky at Night programme, and two former European Space Agency scientists, as well as the Deputy Director of The Square Kilometre Array Observatory. For details of forthcoming and future meetings contact the Secretary TAS on astrosecretary@gmail.com .  Visitors and prospective members especially welcome.