History in the making

The Night Sky June 2019

Exactly 100 years ago an Einstein experiment took place during a solar eclipse of that year. It was devised to prove his theory that gravity can bend the fabric of space. The experiment confirmed that the light from a star behind our sun appeared to be displaced during the eclipse. This experiment proved conclusively that gravity does indeed stretch and contort the fabric of space.

This may seem very technical but some concepts are made much easier to understand when you have a visual representation of a very complex idea. This following visual representation is not perfect but works well up to a point. Here goes! Imagine space to be an enormous tough, rubber sheet with objects placed on top of it. We know that the universe is expanding so the surface sheet is enlarging but not the objects themselves that are positioned on the sheet; they simply become further away from each other. The objects such as gigantic suns, planets and moons which rest on top of the sheet, press down on it. The greater the mass, the more the indentation on the sheet, stretching the fabric downwards and including the surrounding area, like the fabric on a trampoline.

If you now try to roll a ball along this surface, it would be deflected by these indentations more so by large objects and less so by smaller ones. This is what happened in Einstein’s experiment. However, instead of it being a ball travelling along the surface, it was light from a distant star. Just as I finished my last article the hugely historic first picture of a black hole in a galaxy called M87 was published. The black hole is enormous and placed on our rubber sheet or trampoline would make a massive indentation. Indeed, light is not just bent slightly but can be seen helplessly spinning around the black disc at the ‘event horizon’. As it passes this point it is pulled in to the depths of this vast cavern where even light cannot escape. Yet another example of Einstein’s brilliance as he predicted the existence of black holes long before they were observed!

Large objects ‘warp’ space and to make it even more complicated they warp time too! That’s where this analogy is limited. Time slows down the closer you get to a massive object. Time passes more slowly on earth than onboard a GPS satellite as gravity has a lesser influence - about 1 second every 60 years. The clocks on board these satellites have to be corrected for this effect and show how this very abstract idea is used in an everyday application.

Bootes

The constellation of Bootes (The Herdsman) contains one of the brightest stars in the sky, Arcturus. A rich golden yellow and about the same mass as our own sun, it is in fact 27 times the diameter! It has swelled to this size as it is in its final stages of stellar evolution; a fate that awaits our own sun in 5,000 million years. The complete constellation cannot be seen in the southern hemisphere but here in the northern hemisphere we can see it all. Legend has it that Bootes was taught the secret of winemaking. He gave wine to some locals who killed him because they thought they had been poisoned! (I do remember making homebrew like that myself, but got away with it!)

You can find Arcturus by following the handle of the plough in a curve towards the southeast.

This month contains the summer solstice (21st June) where the sun reaches its high point on its path in our sky. This of course means it only gets very dark for a short period.

Jupiter is the closest to us on 12th June and with a pair of binoculars you can see its four largest moons. Apart from our moon it will be the brightest object in the night sky.

Wonderful Objects

The Night Sky May 2019

If you have followed these articles you may remember me writing about Ursa Major (The Plough). This is almost directly overhead and the end two stars famously point towards the North Star, Polaris. But very close to the handle of The Plough, in a region called Canes Venatici, is an object that was first discovered by Charles Messier in 1773. He was in fact looking for objects that might be confused with comets but instead saw something rather wonderful. To be exact - two things! Two galaxies, one much larger than the other locked together by gravity. Currently, it is thought that the two have either passed through each other or very close by, as the smaller galaxy has been distorted. The larger named the Whirlpool Galaxy, containing 100 billion stars, looks like water spinning and draining down an empty plug-hole, dragging its companion (M51b) with it. (See image) At the very centre of the ‘plug hole’ is thought to exist a black hole. This is a region so packed with matter in a very small space that its gravity will not let even light escape from it, therefore appearing black. The light that set off from the Whirlpool Galaxy, 23 million years ago, is that light we observe today. So we see it as it was then, millions of years ago, in effect looking way back in time.

Marathon Man

Charles Messier born in 1730 spent part of his life searching for comets. Whilst doing so, he made the most famous record of deep-sky objects. Often, in astronomical literature, some deep-sky objects are prefixed with an M eg M42 (The Orion Nebula) . These are from the Messier catalogue. The objects are based in order of when they were added to his list. Ironically, he made his list to discount annoying smudges in the sky that weren’t comets. You may want to see all 110 of them and this is possible with a modest telescope. He discovered them from a hotel rooftop in Paris so from Embsay’s beautiful dark sky you have a particularly good chance at different times during the year. There are specific dates during the year to see them all in one night and complete the Messier Marathon. This is certainly on the bucket list for me and many other amateur astronomers. The next possible opportunity will be March next year 2020. With a computerised system, a telescope will find each object with ease but not everyone has that luxury - so slowly does it and in the end over months or years (!) you will get through the list. Some of the objects are quite amazing, even one that looks like a big eye staring back at you! So here is your chance to start ticking them off. The Whirlpool (M51a) and on my diagram you can find 2 more very close by, The Sunflower Galaxy (M63) and The Cats Eye Galaxy (M94).

Planet Watch

The best time to view faint objects this month is 4th May (New Moon) and therefore no moonlight to drown your view. Planets to watch out for are Mars in the west which is slowly sinking. Below the horizon at midnight, on 7th , it will be just above the thin crescent of the moon. Look out for Mercury in the north-west towards the end of the month. It is many times brighter than Mars but sets after 10pm. Jupiter takes over the baton in the south-east as it rises at 11pm.

A Magical Area

The Night Sky April 2019

Virgo

The return of Virgo in the night sky is a sign that Spring is on its way. The constellation will be visible for the best part of six months and then it will fall below the horizon for the next half year. The appearance of this constellation at this time of year was not lost on storytellers throughout history.

Proserpine (Virgo, in Roman legend), was the goddess of fertility. Her father and brothers buried a monster alive under Mount Etna and the Earth began to shake. Pluto, the God of the Underworld, flew out from the Earth in anger, immediately spotted Proserpine and kidnapped her. She vanished for many years and her disappearance caused flowers to wilt, land to become parched and cattle to die. A condition of her release, when it was discovered that she was captive, was that she could only be released for six months and had to return to the underworld for the rest of the year. Hence the Earth turning cold and flowers dying each year, only to be reborn each year in the Spring.

The constellation Virgo contains a treasure trove of deep sky objects. It even hosts a magical area called ‘Realm of the Galaxies’. Also called the Virgo cluster, it contains about 3000 galaxies at about 65 million light years away from us. Most of these are quite faint and you will need a moderate-size telescope to spot them. But the most impressive galaxy to observe and a relatively short distance away would be the beautiful Sombrero Galaxy (M104).

Named appropriately due to its similarity to a wide brimmed Mexican hat! It is possible to spot it through binoculars or a small telescope but you will need more magnification to spot the dust lanes circling the bright centre. It’s definitely worth trying to find, so I’ve included a diagram to help.

Planets

If you are wanting to see some planets this month the best time is very early morning. On 24th the moon will be close to Jupiter at 1am in the south-east and then the following morning Saturn at about 3am. Venus also makes a brief appearance low in the Eastern sky at about 5am before the sun drowns out its bright light.

Lyrid Meteor Shower

The evening of 22ndand morning of 23rd April is the annual Lyrid Meteor Shower. This year the moon will be shining quite brightly as three days earlier it will be a full moon. It may dazzle out some of the show but not all of it! Where to look, what they are and how best to see them can be found in my blog going back to this time last year (see below). The source or radiant is North-East half-way up in the sky over Embsay Crag from the village centre. Wrap up well!

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