Beginners' guide to astronomy: February - Love is in the sky

I hope you are all getting ready for Valentine’s Day. Whilst the story about St Valentine is a rather vague one, there are plenty of other love stories written in the stars.

Queen Cassiopeia of Ethiopia boasted to the sea god Poseidon that she was more beautiful than any of the sea nymphs. As you can imagine, Poseidon wasn’t too happy about this so he sent a sea monster Cetus to wreak havoc in Ethiopia.

In order to bring these terrible events to an end, Queen Cassiopeia offered her daughter Andromeda as a sacrifice to the sea monster and chained Andromeda to a rock to await her fate.

At this point in the story the hero, Perseus, arrives on his winged horse Pegasus. Having just returned from slaying the Gorgon Medusa he was feeling quite bold.

Seeing Andromeda in distress, Perseus tricked Cetus with his shadow and ran his sword through the monster’s flesh. Such a romantic tale could only end one way – yes, Perseus and Andromeda got married and lived happily ever after.

Cassiopeia, Andromeda, Cetus and Perseus are all up there in the sky as constellations reminding us of the legend that accompanies these celestial objects.

However, Andromeda is also the name of an entire galaxy (like our Milky Way). If you know where to look and have good eyesight it is the most distant object visible to the naked eye.

It is approximately 2.5 million light years away from us, so if they could see Earth through a telescope then they would be looking at the Palaeolithic period which was about the Stone Age period.

Just to add to the story of Andromeda, there is a wonderful nebula of ionised oxygen and sulphur gases which have been shaped by the stellar winds and hot stars in its core.

It is known as the Heart Nebula and is appropriately positioned in the Cassiopeia constellation.

Heart Nebula pictured by Steve Heliczer. (Image: Steve Heliczer)

Want another love story? What would you do for the one you loved?

Coma Berenices (Berenice’s Hair) is a little known and not very startling constellation best visible later in the year.

Berenice was a real person in fact, a queen of Egypt. In 246 BCE, Queen Berenice was so concerned for the safety of her husband Ptolemy III of Euergetes that she promised the goddess Aphrodite that she would cut off her long blond hair if Aphrodite brought her husband back safely.

Her cut hair disappeared from the temple of Aphrodite, but the court astronomer Conon of Samos claimed that he could see that it had been placed among the stars.

Venus photographed by Steve Heliczer (Image: Steve Heliczer)

Of course the planet Venus is always associated with the goddess of love. Venus is going to make a spectacular appearance itself (should that be herself?) over the next few months.

The orbit of Venus is closer to the Sun than the Earth and as such its period (year) is shorter than ours, being 243 days.

Every now and again it catches up with the Earth, becoming the “Evening Star”. That is happening now, so if you go out just after sunset you should be able to see Venus with the naked eye.

It will be in the south west and just above the horizon. It will only be visible for about 30 minutes, but the good news is that it will be around in that position and visible for a bit longer, right up to the end of June when it will overtake the Earth’s orbit and soon after, become the “Morning Star” in the eastern part of the sky.

Through a telescope, Venus will look like a phase of the Moon showing a smaller proportion of itself as it approaches the Earth. That would imply that it will get dimmer but, in fact, the opposite happens.

As it gets nearer to the Earth that proportion visible to us becomes brighter – a definite case of less is more.

Venus may be romantic to look at but it has a very hostile atmosphere of toxic gas which is very reflective, which makes it appear so bright to us here on Earth.

Even if you could breathe its atmosphere of carbon dioxide and nitrogen you would be crushed by its atmospheric pressure which is about 90 times that of Earth.

It is believed that Venus might have experienced a runaway greenhouse effect which trapped its heat and made it such an inhospitable place. It is the hottest of the planets with a mean daytime temperature of 464 degrees C.

Space craft have visited the planet but have not had much of a life as the temperatures that can melt lead have a destructive effect on the electronics.

Venus is sometimes used as an example of what might happen to the Earth if global warming continues at its current rate.

Life on any other celestial body has yet to be discovered. There have been lots of theories about the factors necessary for life to form and most include the desirability of there being water.

Planets have been discovered orbiting other stars and astronomers are beginning to be able to analyse the atmospheres of some of them. Bio signatures are being looked for but as yet nothing is suggesting that we are not alone.

Of course, we are only in our infancy of these investigations and there are huge numbers of future places to examine.

Even if an Earth-like planet is ever discovered there is no way that we are able to reach it with current technology. Until we learn how to travel faster than the speed of light it will only be a dream to travel to another world. But then, dreams can come true.

If you are thankful for the world that we inhabit, then why not come along to Francisco Diego’s talk entitled 'Paradise Planet Earth – a Human Responsibility' on February 8? Francisco will explore many of Earth’s unique characteristics and how we should care for the planet.

The talk is both live at the University of Hertfordshire, College Road, Hatfield, and also simultaneously on Zoom. Details can be found at https://hertsastro.org.uk and is open to everyone.

Photo of the Month

Pleiades photographed by Steve Heliczer (Image: Steve Heliczer)

Keeping with the theme of love, this image of the Pleiades star cluster taken by our Steve Heliczer from a dark sky area near Weybourne, Norfolk, shows a cluster of stars known as the 7 sisters.

Keen eye observers will be able to see all seven stars with naked eye observation but often only six are clearly visible.

The story says that the sisters were the daughters of Atlas (of holding up the world fame) and Pleione, the protector of sailors.

After a chance meeting with Orion the hunter, the girls and their mother became an object of his amorous pursuit. To protect them Zeus changed them into a flock of doves which he set in the heavens.

As for the 7th sister, it is rumoured that she married a mortal and hence became fainter. Perhaps that is why the Subaru car badge has only 6 stars on it – Subaru is Japanese for the Pleiades. And the background colour of blue on the logo represents the night sky.