The Sun – At the center of the Solar System
The center of our Solar System, the Sun, is a middle aged, common star, known as a yellow dwarf. So, not one of the largest stars in the universe by any stretch, in fact it is properly know as a yellow dwarf, main sequence star. This name merely refers to the fact that its age relative to the universe is quite common, known as the main sequence. It evolved over 4 billion years ago, and has not even burnt half of its total energy reserves. It is estimated that it will continue to burn brightly for another 7 billion years, so you don’t have to worry about that! Nearing the end of its life, it will grow into a giant red star; before it runs out of energy at which point it will contract to what is know as a white dwarf star.
The Sun gains its energy from a fusion reaction of hydrogen atoms, creating the heavier atom Helium, by releasing enormous amounts of energy, and temperatures in excess of 15 million degrees. For all those aspiring astronomers, the Sun can be an extremely volatile and reactive subject to study, and far from a bright yellow orb, the Sun is extremely dynamic and interesting to observe. Be sure to use a protective solar filter over your telescope, and have fun studying the various coronal eruptions, wind storms, and solar flares that demonstrate the incredible power and substance of our nearest star.
Mercury – the nearest planet to the Sun
Mercury is one of the smallest planets in the solar system, and is also the closest to the Sun. Because it rotates around the Sun with an elliptical orbit, it varies from 47 million kilometers out to 70 million kilometers from the Sun. Because of its diminutive size and proximity to the Sun, it orbits the sun at an incredible speed, completing an orbit of the Sun every 88 days. Mercury’s eccentric orbit is much faster than all of the other planets, which is why the Romans gave it its name for the speedy messenger God – Mercury. Depending on where you can view Mercury from Earth, it has also been variously named as the evening star and morning star, depending on your perspective.
At a little over 4800 kilometers wide, Mercury is just larger than the Moon, but is really only a little wider than continents on Earth such as the width of Australia! It may be larger than our Moon, but not so the moons of Jupiter and Neptune, of which there are 2 moons that are actually larger than Mercury! Ganymede which is a satellite of Jupiter and Titan which orbits Neptune are each larger than Mercury, so that helps to put things in perspective!
As you might expect, due to the proximity to the Sun, Mercury has a scorching hot surface temperature. During the Mercury daytime the temperature can rise above 450 degrees. Paradoxically, the night time temperature reaches opposite extremes, which the temperature going down to negative 170 degrees. The lack of any significant atmosphere means that the surface is a particularly harsh environment, and is visually striking with craters scarring the planet from impacts with asteroids and other space objects in the distant past. In fact, some astronomers liken the features of Mercury to our own Moon, so if you are able to see closely enough, you may be able to spot the resemblance.
Venus – without the clouds
The next planet in order of distance from the Sun, is Venus, which was named after the Roman goddess of Love. Venus is extremely visible in the night sky, and is the brightest planet in terms of light reflection from the Sun. Interestingly, Venus is roughly the same size as Earth, and orbits in a similar distance around the Sun, but that is where the similarities end. Venus is closer to the Sun’s rays, and is blanketed by a thick layer of gaseous clouds, which combine to create a hot and heavy atmosphere. In fact, the surface of the planet is largely invisible to Earth, and the bright visibility is due to the reflection of the Sun’s light from the clouds that form a constant shroud around the surface of the planet.
In case you are interested, the attached photo was taken using radar imagery during the NASA voyage of the Magellan spacecraft, and provides never before seen images of the surface details such as mountains, canyons. Strangely by comparison with planets with no atmosphere, Venus is notable for the absence of the pockmarked craters from space collisions, due to the fact that the dense atmosphere tends to protect the surface and causes space objects to burn up before impacting with the surface of the planet.
The Earth and the Moon from Space
Here is a stunning view of the Moon and Earth taken by the Deep Space craft – DISCOVR. Sorry that you are unlikely, no matter how hard you try, to be able to replicate this from your own backyard!
Nevertheless, this image provides astronomers all over the world with the motivation to research, investigate and to speculate about what is out there beyond our own world. Even the Moon which provides children and adults with their earliest visions of space, is largely hidden from view, with only one surface being visible to Earth during its Earthly orbit. What you see in the image is literally the “far side of the Moon” and something which was hidden from Earth until the advent of space travel.
What we can see of the Moon is some of the most interesting features, such as large craters caused by asteroid impacts, large mountain ranges, deep ravines, and many other features that have held beginner and experienced astronomers captivated for hundreds of years.
Its not too late for you to find out for yourself – have a look at some of the marvelous and inexpensive telescopes that can provide you with a viewing platform in your own backyard.
Mars through a telescope
Yet another planet named after a Roman God – Mars was named after the Roman God of War. Although not exactly known why it was called this, it is assumed that the blood red color prompted the use of this name. It was also discovered by early Greek, Egyptian and Chinese astronomers who all independently recognized and named the planet after its deep red coloration. Despite its early discovery and distinctive coloration, Mars is the second smallest planet after Mercury, being much smaller than Earth. It also orbits at a much greater distance from the Sun, and you might be interested to know that the Sun would only appear half the size from Mars than our view of the Sun from Earth. Consequently, it is much cooler on the surface of Mars, and generally a very inhospitable place, with an atmosphere made largely of carbon dioxide, strong winds, and severe dust storms.
Nevertheless, Mars is an extremely interesting subject of astronomy, with stunning surface features, such as the pictured 2000 kilometer long valley, which is up to 8 kilometers deep, as well as the volcanoes that you can also see at the left of the image.
Ceres and the Asteroids
Without wanting to enter into any debate over the status of planets versus dwarf planets, I think it is safe to say that Ceres is a dwarf planet, which can be found orbiting within the asteroid belt. Ceres belongs amongst a cluster of small and irregular planet like objects between Mars and Jupiter can be found many asteroids and meteors, and even small planets. Ceres cannot be written off as just another space rock, it has and interesting moon like surface, and yet to be explained bright spots that illuminate the view from space. One feels there is more to be learned from this speck of rock spinning around a distant orbit of the Sun, but you need to find a very clear viewing location to see any of these small and distant objects.
In fact, one feels that there is a whole lot more to be learned about the solar system in general, so be sure to read further about the outer planets – in particular the mighty Gas Giants, and their critical part in our solar system.
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