What's in your Sky this Winter?

One of the most fascinating aspects of the science of astronomy is the concept of distance. Everything in the night sky is so incredibly remote! Even the closest star to our solar system, the Alpha Centauri triple-star system, is 25 trillion miles away. The thousands of other stars that we see every clear night with the naked eye, as well as the millions of stars visible through telescopes and binoculars, are farther still! The Winter skies contain a huge range of objects. Have you ever noticed that the night sky in winter looks different than the summer? We see constellations at different times of the year - Spring, Summer, Autumn, & Winter. This occurs because the Earth is orbiting the Sun. In winter, we see the constellation Orion in the south at night and during the day the Sun is in the sky with the constellation Scorpius. In summer, we see the opposite (we see Scorpius at night and Orion is in the sky during the day). This is why you cannot see Orion or any one constellation all year long…

  Unless it is circumpolar. There are 5 constellations in the sky (at this latitude) all night long every night of the year – Ursa Major, Ursa Minor, Draco, Cepheus, and Cassiopeia. These are the best constellations to start with because they are visible all year long. Plus, if you don't know your directions you will want to start with Polaris (the North Star).  Note: Planets and moon phases are not included in this section because they change.

The Big Dipper in the constellation Ursa Major is in the northeast. The handle is pointed towards the ground/horizon.

       Naked Eye Planets

There are 5 planets you can see with your own eyes! From Earth, we can see the five closest planets – Mercury, Venus, Mars, Jupiter, and Saturn. To your eyes they appear as stars. They do not create light like a star, rather sunlight illuminates their surfaces and we see them the same way we see our Moon, just not the same size. The Moon appears so large because it is close and the planets appear like dots or ‘stars’ because they are so far away.

 The 5 planets were discovered before the invention of the telescope. Ancient people called these five planets ‘wanders’ because they appear to wander against the background of stars. This is due to the orbital movement of the planets. The word ‘planet’ comes from the Greek word ‘wander’. One good way to tell stars from planets is that looking at them with the unaided eye, stars twinkle and planets do not. The twinkling of stars, technically known as stellar scintillation, is caused by the Earth's atmosphere. Because stars are so incredibly distant from us, any disturbances in the atmosphere will bounce around the light from a star in different directions. This causes the star's image to change slightly in brightness and position, hence "twinkle".

Mercury is the closest planet to the Sun making it the most challenging planet to observe. It is only visible during twilight - just before sunrise or just after sunset. The window for observing Mercury is measured in minutes. The best times to view the planet is when it is furthest from the Sun in the sky called greatest elongation. When Mercury is at greatest elongation it is visible for about an hour before sunrise or after sunset. Binoculars and telescopes are recommended for viewing Mercury. Because it is an inferior planet (between Earth and the Sun) it has a cycle of phases similar to what we see on the Moon. Look for Mercury in the east before sunrise between December 15th 2011- January 5th 2012.

Venus is the brightest planet. In fact, it is the 3rd brightest object in our sky (after the Sun and Moon). Venus is often referred to as the 'Morning or Evening Star' as it is only visible during twilight - before sunrise or after sunset. Even thought it appears as a star to your unaided eye, it is a planet and the light is coming from the Sun. Because it is an inferior planet (between Earth and the Sun) it has a cycle of phases similar to what we see on the Moon.

Binoculars or a telescope is needed to view the phases. Venus returns as the 'evening star' in December 2011. The bright planet will spend most of next year dominating the west after sunset until early June when it makes its final transit of the Sun for this century.

Mars is known as the 'Red Planet' because it's surface is colored by iron oxide. It appears as an orange-red star in the sky to your unaided eyes, but it is not a star. It is a planet. Sunlight shines on Mars and the distance between us on Earth and Mars makes Mars appear small like a star. The brightness of the planet varies depending where Mars is compared to Earth. When we are close to the Red Planet, it appears brighter than when Mars is on the opposite side of the solar system. When Mars is closest to Earth it does NOT appear significantly bigger to your unaided eyes, just brighter. Mars currently rises before midnight in the constellation of Leo and wil be visible in the evening sky until September 2012.

Jupiter is the biggest planet in the solar system, but not the brightest in the sky (Venus takes that title). It is still very bright and hard to miss. Jupiter is a favorite among amateur astronomers because it is always putting on a show. Even with the smallest optical aid such as binoculars, you can see the four largest moons called the Galilean Moons.The difficulty in seeing the moons through binoculars is to keep the binoculars sufficiently steady so that the image does not vibrate. This can be done by attaching the binoculars to a tripod or, if that is not possible, to rest the elbows on a solid wall or railing to keep the hands holding the binoculars sufficiently still. It is currently visible high in the south, is the brightest star-like object  and can be seen for most of the winter night.

 

A conjunction is also an opportunity to clearly see the ecliptic, the plane of our solar system. All of the planets extend out from the Sun's equator, within a few degrees of each other, in a remarkably flat plane, like dust mites on the surface of a spinning CD. When you look at the cluster of planets in the sky, you can see how they all form a line running up at an angle from the horizon.  Tilt your head to match that line and you are looking along the path we on Earth follow around the Sun every year.

February 2012: Convergene of Mercury, Jupiter and Venus in the evening sky, Mars also low and bright in the East at the same time

May 22^nd 2012: Mercury  half a moon diameter from Jupiter   

August  17^th 2012: Mars  2° south of Saturn                                                                                                                          

October 6^th 2012: Mercury  3° north of Saturn

 

For more info on the naked eye planets see HERE

 

The phenomenon known as Earthshine occurs when reflected sunlight from our planet illuminates the night side of the Moon. Typically, this results in the moon's night side being bathed in a soft, faint light. It is also known as the Moon's ashen glow or as the old Moon in the new Moon's arms. Earthshine is most readily observable shortly before and after a New Moon, during the waxing or waning crescent phase.

When the Moon is new as viewed from Earth, the Earth is nearly fully lit up as viewed from the Moon. Sunlight is reflected from the Earth to the night side of the Moon. The night side appears to glow faintly and the entire orb of the Moon is dimly visible.

 

Iridium Flares

These are a wonderful set of satellites that I have watched over the past ten years. After Comet HALE BOPP and the formation of the Galway Club my interst in astronomy kick started again, after buying a telescope and spending many nights out observing I started noticing  these extremely bright satellites, but these were no ordinary satellittes. The would be moving along and then all of a sudden energise in brightness to about 40 times that of Venus similar to a First Quarter Moon for several seconds and the fade away. A fantastic sight and whats even more amazing is that you can find out when and in what part of the sky to see them. You do not need to know the constellations just face the direction given, you can't miss them. Also the lower the magnitude, the brighter. Usually -8 is the best we can see.

The Iridium communication satellites have a peculiar shape with three polished door-sized antennas, 120° apart and at 40° angles with the main bus. The forward antenna faces the direction the satellite is traveling.

Occasionally, an antenna reflects sunlight directly down at Earth, creating a predictable and quickly moving illuminated spot on the surface below of about 10 km diameter. To an observer this looks like a bright flash, or flare in the sky, with a duration of a few seconds.

Ranging up to -8 magnitude (rarely to a brilliant -9.5), some of the flares are so bright that they can be seen at daytime; but they are most impressive at night. This flashing has been some annoyance to astronomers, as the flares occasionally disturb observations and can damage sensitive equipment. When not flaring, the satellites are often visible crossing the night sky at a typical magnitude of 6, similar to a dim star.

Viewing Satellite Flares

Looking for satellites whilst skygazing, or satellite spotting, is a hobby for many people. While satellites may be seen by chance, there is a  websites HERE which provide location specific information as to when and where in the sky a satellite flare may be seen.

Clear Skies!

Ronan Newman