By: CLIVE JACKSON
Clive Jackson is the Director of the Astronomical Observatory of Tavira (Sitio do Malhão, Tavira) and the Camera Obscura (next to the Castle in Tavira), specialising in education and public outreach.
WELCOME TO the April night sky. We are now officially into springtime and the constellations of winter like Taurus, Orion and Canis Major are all sinking in the west at nightfall.
In the south, we have the constellations of Leo and Virgo, and high overhead is Ursa Major.
We live inside the solar system and this is a family of planets orbiting a star that we call the Sun. But the Sun is also part of a grand family of stars that form a galaxy, which we call the Milky Way.
This galaxy is of course visible on a dark clear night as a faint band of light stretching across the heavens.
The Milky Way is high in the sky during the summer and the winter but during the spring and autumn, it lies along the horizon and we have a view out of our own galaxy and deep into the universe.
So what lies outside our own galaxy?
The answer is more galaxies – lots more! In fact, there are at least 100,000 million other galaxies in our universe.
We would think that with so many galaxies in the sky they would be easily visible but the truth is that they are so far away practically none of them are visible without a telescope.
The exception is the galaxy in the constellation of Andromeda but that is an object best visible in the autumn.
When giant telescopes are used to take images of the deep sky, the pictures contain many more galaxies than stars and when we are looking at these distant galaxies perhaps there is some kind of intelligent life looking back at us.
The constellation of Leo is high in the south during April evenings and Saturn is still there glowing with a pale yellow colour that is quite different to the star that is just to the right called Regulus.
This star is white and is noticeably dimmer than Saturn.
This is a good opportunity to recognise a planet by the fact that normally planets don’t “twinkle” and stars do.
Although Saturn is much smaller than Regulus (millions of times smaller), it is in fact hundreds of millions of times closer to Earth.
It appears slightly larger in the sky so the movement of the Earth atmosphere does not upset the beam of light reaching our eyes and therefore it appears to shine with a steady light.
On the night of April 15, the Moon will be close to Saturn.
The Moon is New on April 6, First Quarter on April 12, Full on April 20 and Last Quarter on April 28.