Posts Tagged ‘earth and the moon’
Fun Astronomy Facts
If you want to measure our solar system, how would you do it? This simplest way is to measure it in light years. For those not familiar with the term, a light-year is the distance that light travels in a vacuum in one year. This is because the distances between stars is so huge that it is otherwise very challenging to imagine them. A light year is exactly 9,460,730,472,580.8 kilometers. Putting this into real world distances, the Milky Way is approximately 100,000 light-years across.
The Earth is one of nine planets that form the Solar System, so called because the sun, the source of solar energy, is the central point around which all the planets revolve. So far, scientists have not been able to establish or prove the existence of life forms on any other planet within the solar system. Often, the search for other life forms has focused on looking at the climatic conditions of the celestial body in question. Scientists assume that life forms on a different planet would need similar conditions as life on earth, such as oxygen, light and water, to grow. This may or may not be true.
Other than the sun, no other celestial body significantly affects the earth as the moon does. It is well know that the moon affects the rise and fall of the ocean tide. Such is the effect of the gravitational pull between the earth and the moon. Jupiter is easily the largest planet in our solar system. To put its size in context, Jupiter is more than 300 times the mass of Earth. Here is the interesting part; Jupiter has 63 moons that orbit it and yet it is not the planet in the Solar System with the most moons. That honor belongs to the ringed-planet Saturn, which has 66 moons identified so far. Pluto, the farthest flung among the nine planets, has been the subject of heated debate on whether it really qualifies to be considered a planet. Nowadays, it is classified as a dwarf planet. Its orbit around the Sun is somewhat heavily elliptical. In fact, there are instances where Pluto is actually closer to the Sun than Neptune, the planet that precedes it.
Now speaking of size within the Solar System, well, let us just say that the Sun is unmatched. Did you know that the Sun comprises more than 99% of the total mass of the entire solar system? Jupiter actually takes up much of the remaining proportion. Surface temperatures on the Sun stand at 5000 Kelvins (4727 degrees Celsius). With temperatures at its core reaching a 15.6 million Kelvins (15.6 million Celsius), the Sun is truly a celestial spectacle. It gets even better when one realizes that the Sun is classified as a class G star. Stars are classified in six major categories that tie in to the surface temperature and brightness. The categories are M, K, G, F, A, B and O listed in ascending order brightness and surface temperature. You can see that the Sun falls on the lower end of this classification. Category B and O are rare in the universe while most stars are in the category M and emit less heat and light energy. That said, the Sun is within the 90th percentile by mass among all stars. We have found other stars that are larger than our sun: one is estimated to be approximately 60,000 times bigger.
The Solar System forms a tiny part of the Milky Way Galaxy, a vast conglomeration of stars and planets. What makes astronomy so thrilling is that despite its size, the Milky Way is not the only galaxy in the universe. There are hundreds of billions of galaxies out there, probably more. The closest galaxy to our own Milky Way is Andromeda. Now, brace yourself for the distance: it is 2.3 million light years away. One of the most exciting phenomena for astronomers is the black hole. It is an area of the universe where the concentration of mass is so massive (no pun intended) that the gravitational pull it generates sucks in everything around it. Everything includes light. Remember that the escape velocity for any object in the universe is the speed required to escape the objects gravitational pull. The escape velocity for the Earth is slightly over 11 kilometers per hour while for the Moon is 2.5 kilometers per second. Well for a black hole, the escape velocity exceeds the speed of light. That is how strong the pull is.
Author: Rachael Stone
Article Source: EzineArticles.com
Provided by: Digital Camera News
Lagrangian Points and Nasa’s Plan to Explore Space
Nasa is relying on the existence of Lagrangian points between every set of planetary bodies it intends to explore in order to implement its plan of successful interplanetary space exploration. Although this at first may seem to be a vague and mystical concept, foreign to all but trained astrophysicists, in fact it is really quite simple to understand.
The Lagrangian in physics is merely nothing more than a set of two simpler equations that can be used as an alternative for Newtons second law; force equals mass times acceleration. A Lagrangian point between two bodies exerting competing forces on a body is therefore a point at which the forces are equal and opposite. According to Newtons third law, if the net force on a body is zero, it will stay at rest if at rest and if in motion it will stay in motion.
In mathematical terms, visualize a graph of a big bowl. The Lagrangian point is the point at the very bottom of the bowl. This point represents the point at which the maximum energy, the energy from the bottom of the bowl to the top, must be supplied to kick the body out of the bowl in order to prevent the body from rolling back down to the bottom of the bowl and returning to its energy minimum. Therefore, the point at the minimum of the bowl represents the point of maximum stability in terms of preventing the influence of a net imbalance in the forces of the two gravitational forces on it from disturbing it. This point in question is the orbit which has the most stable velocity and angular momentum. The body acted on could be a space station between two large masses such as the earth and the moon or any two interplanetary bodies of significantly greater mass than the spacecraft.
How this relates to Nasa and its plans for future space travel is that they have the ability to use the Lagrangian formulas to calculate the Lagrangian points between different planetary bodies and therefore to determine the location of these orbits. Therefore, it is possible to build space stations as stepping stones between the earth and the moon, the moon and Mars, and on and on as far as you want to go. As it would be unrealistic to expect any spacecraft to be able to return to earth from far out in space in the case of an emergency or the need to make repairs, this makes the possibility of extending space travel outwards into the solar system and theoretically beyond feasible within the constraints of our technology and budgetary considerations.
Sources:
1) NASA Reveals New Plan for the Moon, Mars & Outward
By Leonard David; Senior Space Writer Space.com
Author: David Craig
Article Source: EzineArticles.com
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