Summer’s here! The weather’s heating up and skies will hopefully be clear for a bit of stargazing! There are lots of interesting sights in the sky this July, so while you may have to wait longer for it to get dark, get outside, allow your eyes to adjust and get searching.
There is a total eclipse of the sun occurring right at the start of July! Unfortunately, though, it will only be visible from the South Pacific, Chile and Argentina. A solar eclipse occurs when the moon travels (from our perspective) in front of the sun, casting a shadow on the earth. This shadow is very small, and so it can only be seen from certain parts of the world.
There is a partial lunar eclipse occurring on the 16th July – most visible from Europe and Africa. A lunar eclipse occurs when the earth’s shadow falls on the moon, blocking the sun’s light. This eclipse will only be partial, not total, which means only part of the visible moon’s surface will be covered by shadow.
Some of the constellations visible this month are Cygnus, Cepheus, Cassiopeia, Camelopardalis, Pegasus, Hercules and Bootes.
Cygnus is one of the most recognizable constellations in the northern Hemisphere’s summer, and contains one of the three stars that form the summer triangle, Deneb. Deneb is a first magnitude white supergiant, one of the brightest and largest stars. To find Cygnus, search for the summer triangle. This is a large triangle formed by three of the brightest stars in the sky, and is southeast of the pole star. Cygnus’ ‘tail’ is formed by Deneb, the top left corner of the triangle and the dimmest of the three stars. Along with five other stars in the constellation Cygnus, it also forms part of the northern cross, an asterism within Cygnus itself. Cygnus can also be spotted by searching for this large cross in the sky.
Cygnus plays host to Cygnus X-1, a binary supergiant that is accompanied by a black hole. This black hole was the first to be discovered and widely known, as black holes cannot be seen through a telescope. It was discovered in 1964, by a rocket scanning for X-ray sources. This black hole is a strong X-ray source. Stephen Hawking once bet his friend that this object wasn’t a black hole but had to concede when evidence showed it most likely was!
Another constellation that can clearly be seen this month is the slightly smaller constellation Cassiopeia. It is named after the Queen Cassiopeia in Greek myth, who was extremely vain and claimed that she was more beautiful than the Nereids, the sea nymphs. Poseidon was enraged and placed her in the sky as punishment, forcing her to spin around the pole star, clinging to her throne to stay on.
Cassiopeia is a ‘w’ shaped constellation northeast of the pole star at this time of year. The brightest star in the constellation, Alpha Cassiopeiae, is actually a star system or multiple star, which consists of four stars orbiting each other. The primary star is a giant orange star, with a magnitude of 2.2 (the lower the magnitude, the brighter the star) while the companion stars are much dimmer. Cassiopeia also contains a rich section of the milky way. In this section are two neighbouring emission nebulae, the Heart nebula and the Soul nebula. These are regions of space formed of ionized gases which emit light.
There are many planets visible throughout July, with Jupiter visible as a bright non-twinkling ‘star’ in the south to southwestern evening sky in the constellation of Ophiuchus, the serpent-bearer.
Saturn appears as a medium brightness ‘star’ to the naked eye; the rings visible only through a telescope. It is at its brightest in 2019 through to July 22nd and is at opposition to the sun on 9th July. It appears in the morning sky until July the 8th, and then in the evening sky for the rest of July within the constellation of Sagittarius, the Archer. On 15th-16th July, the full moon will pass closely below Saturn.
Uranus will spend July mornings in Aries, the ram, but can be difficult to see without a telescope. Neptune will be at its brightest from July to November, but even at its brightest, a telescope will be needed to see it. It will be in the constellation of Aquarius in the morning sky.
The Perseid meteor shower, one of the brighter meteor showers of the year will rounds off the month in the northern hemisphere, starting in mid-July and continuing into August. The meteors will seem to originate from the constellation Perseus (hence the name Perseids) and are made up of debris from the comet Swift-Tuttle. This comet has a nucleus 26km in diameter and is predicted to show up next in 2125. At its peak, the Perseid meteor shower is known to produce 60-100 meteors per hour!
Written by Anna Taylor, Education Officer