Tuesday, February 21, 2012

Planet Question Time!

Is the order of planets in a solar system always like ours, with rocky planets close to the sun and big gas giants further away?
(c) NASA
No. The most recent system to go against this is Kepler-20 which has 5 planets orbiting it, among them one of the most earth-like planets discovered thus far. Kepler-20 has three gas giant planets like Jupiter and two small rocky planets like the Earth or Mars, but they are arranged unlike our solar system or even unlike we imagined they could be. All five planets orbit closer to their star than Venus and they alternate in size as their orbit increases; large, small, large, small, large. The three large planets are bigger than the Earth but Smaller then Neptune whereas the smaller rocky worlds, known as Kepler-20e and Kepler-20f, are similar in size to Earth but orbit very close to their star so have scorching surface temperatures. All of these planets orbit their star in less than 78 days, which is inside the orbit of Mercury if compared to our solar system. 

Do all moons have to be solid and round or can they be gaseous?
A moon is a natural satellite of a planet, which can be a regular body, round like our moon, or irregular, like that of an asteroid. Mars has two moons that are irregular in shape called Phobos and Deimos; these are called minor satellites and are thought to be either remnants of larger objects broken up by impacts or captured objects.
(c) David Kipping -exomoons
There is a vast array of different moons in our own solar system and some recent studies are even searching for moons orbiting around planets orbiting other stars. As with all current extra solar searches the larger the moon is the easier it will be to see the effects on the planetary system. Titan, Saturn’s moon, is the second largest moon in our solar system and is nearly twice as large as our own moon, it is also considered the most planet-like moon as it has a thick atmosphere and strong surface features like our own planet.  In relation to its planet, however, it is still very small and although has a dense atmosphere it would have to be a lot larger to be able to sustain a predominantly gaseous body like that of a giant planet. If a moon were massive enough to retain a large gaseous atmosphere, like that seen of the larger planets in our solar system, it would have to be orbiting a planet a lot larger than itself so that the orbit would define it as a satellite of that planet and in this regime the definitions become blurry (even in our own solar system).

If you have any questions on planets you would like answered post a comment below and I will see what I can do.

Saturday, February 11, 2012

Our Back Yard

My day job may be looking at planets light-years away orbiting other stars but I am still inspired by the majesty of our own solar system and its seemingly effortless elegance.

The solar system is a beautiful array of planets, starting with the inner solar system and its small rocky worlds out to the large gaseous planets of the outer solar system and the bodies that lie in the dark beyond. 
The terrestrial planets alone display an array of qualities, Mercury and the break down on Newtonian mechanics, Venus and the runaway greenhouse effect, Earth and the origins of life and, Mars with its depleted atmosphere and its giant mountain ranges.
The asteroid belt marks the region between the inner and outer planets where the gravity between the Sun and Jupiter prevent the build-up of a planetary body.
The Giant planets are large gaseous worlds orbiting the Sun at over 5 times the distance of the Earth. The first is Jupiter the largest of the Giants, rightfully names the king of the gods, you could fit the earth inside it more than 1000 times. The next out is Saturn with its vast ring system that spans over 200 thousand km but are less than a football goal wide. Leaving Uranus, which barrel roles around the sun, and Neptune with winds that can reach around 2,000 kilometres per hour orbiting at over 20 times the distance from the Earth to the Sun.

Five out of the seven planets in our solar system can be observed from Earth with the naked eye, their orbits carving paths through the constellations since they were first observed millennia ago. 
It was not until the development of the telescope in the 17th century that the ability to observe fainter objects in the night sky was realised. In the spring of 1781 Sir William Herschel turned his telescope to the sky to continue his search for binary stars when he observed an object unlike any others he had been observing. Herschel made many more observations of the object and carefully documented its movement asserting them to be of a comet like body. After presenting his findings to the Royal Society and notifying the Astronomer Royal, a number of other astronomers started to suspect that the object was not a comet but a planet. With the help of Anders Lexell, a Russian astronomer and mathematician, the orbit of the object was calculated revealing it to be nearly circular occupying a space beyond that of Saturn. It was in 1783 that William Herschel presented the discovery of a 'new primary planet of the solar system' to the Royal Society, with the proposal to name it 'Georgium Sidus' after King George the third. This name, however, did not catch on outside of Britain and in 1850, 28 years after Herschel's death, the Planet was universally known as Uranus.
The discovery of Neptune is a slightly different story. After many observations of Uranus and careful monitoring of its orbit it was hypothesised that there was an unknown gravitational body perturbing (making slight changes to) its orbit. In 1845 independent of each other, two mathematicians, John Crouch Adams and Urbain Le Verrier, developed calculations estimating the position and mass of this new planet. Adams was a quiet unambitious mathematician from Cornwall and although his calculations were not taken seriously until after the observations of Neptune were made in 1846 by the Berlin observatory working from Le Verrier’s calculations, was content to share the credit of discovery with Le Verrier. In 1998, however, it was determined that the credit solely belongs to the person who calculated and obtained the observations giving the credit to Le Verrier.

The solar system we live is still in some ways a mystery to us and the ability to understand it is still a very important scientific goal and although I am now observing exoplanets and trying to understand their dynamic atmospheres I always think back to what we can learn from our own back yard.

Wednesday, February 1, 2012

The Stargazing 5

The top 5 things I never go stargazing without.
Taken by me in Exeter 01/02/12

1) Hat and Gloves - When it is a clear night it is usually also a cold one. We loose most of our heat from our heads so it is always a good idea to have a hat. Also the first thing to go in the cold is the extremities so a pair of gloves will mean you can hold onto the starguide or binoculars a bit longer.

2) Red Light -  If you have the luxury of finding a dark place to do your stargazing it probably means that it is harder for you to see where you are walking. Always use a red light when stargazing as it will not ruin you night vision (as our eyes are more sensitive to green).

3) Starguide - There is so much to see so it is always a good idea to have a starguide or map with you. Universe today just posted a Night Sky guide for February that is very good. There is also a google sky map app for android, which has a red light mode so you can use it when you are out.

4) Blanket / Bin bag - Since I can remember me and my family have taken bin bags out to the field with us so that we can lie on the grass and look up at the sky (though a blanket will probably be warmer). It is a great way to get a full sky view and you can always look at the sky and think that you are looking down on it (try it and see what you feel).

5) Binoculars / Telescope - These are optional extras. Though if you have them it is always a good idea to take then out on a good clear night (lets face it they only come around every so often). Binoculars are a great way to get a closer look at the sky with the least cost though any larger than 50x10 will probably require a tripod. A telescope, though a little more costly, will allow you to see even more and it is worth the cost if you have the time and money.