July 2020

Planets to look for

Jupiter and Saturn are back in the evening sky and ready to be the main attractions of July. They both reach opposition this month, within a week of each other, with Jupiter making it on July 14^th and Saturn on July 21^st.

Why is opposition so important? It is when an outer planet is directly behind the Earth from the Sun, so the distance between our planet and the planet at opposition is at its smallest and the planet will look the largest it can in our telescopes. This makes a lot of difference with Mars (when it happens in October this year), but not so much with Saturn. Jupiter will benefit somewhat from this alignment, however, with it being slightly easier to see detail on its surface, or even the shrinking Great Red Spot as races across the face of the planet in a couple of hours. Also watch out for the black dot shadows of its moons, particularly Io and Europa, moving across the face of Jupiter as well. Many apps are available that can tell you when these events happen.

While Jupiter and Saturn hang around between Sagittarius and Capricornus, Mars has continued eastwards and is still moving along at a good pace through Pisces, above the Great Square of Pegasus. If you are keeping an eye on it, you start to notice it getting brighter now, as it rises around 11pm. The Moon will be next to it on July 11^th.

For the early risers, Venus has moved up above the morning twilight now, rising around 4am. It makes a close pass to the star Aldebaran on the morning of the 12^th, and a waning crescent Moon sits to the left of the Hyades cluster on the morning of the 17^th while Venus is just below.

Mercury is also in the morning sky this July, making a brief appearance near the top of the morning twilight around the 20^th.

Constellation of the month

Virgo the Maiden

Virgo is the second largest constellation in the sky. Virgo is said to represent a young woman and often associated with the harvest season – two thousand years ago the Sun was in this part of the sky during the end of the northern hemisphere summer, when crops were being gathered in. Spica, the brightest star in Virgo, means “ear of wheat’ and Virgo is often drawn with her hand upraised holding some of this important grain. Her other hand is represented by eta Virginis, also known as Vindamiatrix, the Grape Gatherer. The cluster of grapes she is reaching for is represented by the faint but large open cluster in the middle of another constellation, Coma Berenices.

Some people draw Virgo as the goddess of justice, holding the scales of Libra in her hand. In this form she represents Astrea, the Roman goddess of justice.

In these modern times Virgo is better known for the galaxies found within its borders. The Virgo Supercluster is a large cluster of galaxies, so large it also attracting other galaxies toward it! You will need a telescope to see these galaxies, but some are relatively bright and will only need a small telescope to detect their light, which is travelling from around 55 million light years away.

Virgo as observers see it from the southern hemisphere.

M87

The constellation of Virgo is famous for its galaxies. As we look towards this direction in the sky we are looking out towards what is known as the Virgo Supercluster. Our own Milky Way galaxy is part of this large conglomerate of star cities. On the border of Virgo and Coma Berenices is a galaxy described as a “supergiant elliptical” as it contains more mass than most galaxies in the Supercluster – Messier 87.

M87 and one of the gas jets from the black hole inside it. By NASA, STScI, WikiSky

It’s also known as Virgo A as it is a very strong source of radio signals and its known to have a supermassive black hole in the centre of it that projects a massive jet of gas from its core. It even has 12,000 globular clusters circling around it – compare that to only 120 or so that the Milky Way is known to have. Yes, everything is super massive about M87! A ground-breaking image of the black hole was published in April 2019, which shows how electromagnetic radiation is bent around the black hole itself. This is impressive, considering we know of several black holes closer in our own galaxy, but they are too small to be seen, but we can image this bigger black hole that is so much further away!

Bright matter surrounding the block hole in M87.

Credit: Event Horizon Telescope Collaboration

It is 53.5 million light years away, which isn’t too far in galactic terms. It lies about half-way between Vindamiatrix in Virgo and Denebola, the star that marks the tail of Leo the Lion to the west. Nearby is an interesting line of galaxies known as Markarian’s Chain, which is a popular target for photographers. You won’t be able to see the jet of gas yourself, but the large fuzzy halo of M87 should be easy to pick up, as are the brighter members of Markarian’s Chain.

M87 is about half-way between Vindamiatrix in Virgo and Denebola in Leo. The curve of galaxies known as Markarian’s Chain is nearby.

Perseverance heads to Mars

As the next opposition of Mar approaches in October it also means a window of opportunity for launching missions to Mars opens up so that we can take advantage of favourable the planetary alignment for the quickest trip possible between our two planets. A lot of eyes will be on the next NASA rover to head to Mars, Perseverance, which is due to launch on July 22^nd.

Perseverance is similar to the previous rover, Curiosity, which is still operating on the surface on Mars. Powered by plutonium, Curiosity wasn’t affected by the global dust storm that silenced the solar-powered rover Opportunity in 2018, and it has been quietly working away during that time. One important improvement will be bigger, thicker wheels on Perseverance. The surface on Mars is quite rough and rocky and the wheels on Curiosity have taken a terrible beating over time. Even though it has six wheels, it needs them all. The rovers are about the size of a 4-seat 4WD car (taller than the average human.) and weigh about a ton.

Credit: NASA/JPL-Caltech

Another new addition is the helicopter the rover will release from its underside that will be capable of short flights of up to 90 seconds a day. It is called Ingenuity, and its two carbon fibre blades are 1.2 m long. Engineers will be very interested to see how it flies in Mars’ thin atmosphere and lighter gravity, so there will a lot to learn from this addition. It could lead to more drones, or bigger ones, added to missions in the future. You can find out more about it at mars.nasa.gov/technology/helicopter/

The small helicopter drone Ingenuity that Perseverance will drop onto the surface of Mars. The top is a solar panel to recharge batteries. The blades are 1.2m long.

Credit: NASA/JPL-Caltech

The official mission website is at mars.nasa.gov/mars2020/