Friday, February 25, 2011

Astronomer Biography Quarter 3: James H. Jeans


James Hopwood Jeans was born in 1877 England, where he excelled in math and sciences. After graduating from Cambridge University in 1898, he became a professor of mathematics at both Princeton University and Cambridge University. Jeans contributed heavily to areas of astronomical physics, however many of his works were ultimately proven wrong, with the exception of a few.  However, what some of his incorrect theories did was move science in the right direction. For example, Jeans was able to disprove Laplace’s theory of how the solar system formed. Laplace had determined that the solar system had formed out of a single cloud of gas, which Jeans ultimately concluded to be incorrect. However, Jean’s theory to explain how the solar system is also considered incorrect today, that the planets were all formed from materials that were scattered out by the sun into the solar system after a near-collision with a passing star. So, while Jeans’ theory was ultimately incorrect, it progressed scientific theory on the formation of the Universe.
                Another theory Jeans came up with that was ultimately proven wrong was steady state cosmology, the idea that the Universe is constantly expanding, and that new matter is continuously being produced in this expansion. Obviously, this theory does not accept the concept accepted today that matter cannot be created or destroyed, and thus is no longer accepted among the scientific community.
                Jean’s biggest accomplishment was his discovery of a formula to find the critical radius of an interstellar cloud in space. A Jeans length is essentially the length an interstellar cloud of dust is capable of being. Any length smaller than a Jeans length will form into a star, and any cloud too large will collapse on itself.  Jeans was able to formulate an equation to represent this relationship, which would ultimately come to be known as “Jeans Instability”.  This discovery gives astronomers a clear idea of the sizes of interstellar clouds, allowing them to make much more accurate measurements of their sizes.
                Over the course of his life, James Jeans joined the ranks of the many great scientists who became a part of the Royal society of England. In 1906 Jeans was first inducted, and over the course of his life there he received many accolades, including the Royal Medal of the Royal Society in 1919, the Gold Medal of the Royal Astronomical Society, and was even knighted in 1928. James Jeans’ biggest accomplishment is certainly his formula for the instability of interstellar clouds, however all of his other discoveries, while ultimately not correct, were vital in the progression of scientific research in those areas. By challenging theories such as Laplace’s on the formation of the Universe, Jeans created a movement into further discovery of how our solar system was formed.  Jeans lived during a time of massive scientific discovery, as the ideas surrounding the Universe were being turned upside down on a regular basis. Jeans contributed heavily to this time period of massive scientific discovery, as the world began to finally understand the functioning of the Universe around it.

APOD 3.6

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This beautiful photo taken from the Swiss Alps highlights the star clusters that are visible at this time of year in the night time sky. M45 in Taurus, M31 in Andromeda, and M42 in Orion are very clear. M31 is especially clear, the farthest away object in the nighttime sky that is visible to the naked eye.The winter constellations, especially the zodiacal ones, are very clear. This photo highlights what is visible from Earth, and how fascinating the sights are from a good vantage point with minimal light pollution.

APOD 3.5

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Lying beneath a spiral galaxy is an enormous object known as Hanny's Voorwerp. Stretching to lengths larger than our own milky way galaxy, the sheer mass of Hanny's Voorwerp can be seen in comparison to the galaxy it rests below. The greenish aurora to the object is due to oxygen particles being illuminated in the visible spectrum. Hanny's Voorwerp is believed to have been a part of the spiral of the galaxy above it (IC2497), but the galaxy collided with another, causing the massive tail to be pulled apart to where it now rests. The sheer size of this object is awe inspiring, a space the size of our galaxy inhabited primarily by oxygen particles.

Friday, February 11, 2011

APOD 3.4

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The first thing I noticed when looking at this picture was the red color of the stars behind this massive expanse of dust. These stars are not actually red (well, maybe some of them are), but instead the dust is blogging all other wavelengths of visible light, and allowing through primarily only the red. While this enormous wave of interstellar dust is not dense at all, it stretches for hundreds of light years, making it appear to be nearly a completely solid block of dirt. This cloud is referred to as NGC 2174, and is located in the constellation Orion. While the picture may lead you to believe that it only takes up a tiny part of the sky, the mass of this nebula actually stretches a length greater than the full moon, from the viewpoint of the Earth. In reality however, this mass is thousands of light years long.

Friday, February 4, 2011

APOD 3.3

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Another fascinating photo from an alien world is brought to us by the Mars rover Opportunity. This is the seventh year Opportunity has been running on Mars, quite an accomplishment considering it was only expected to last 3 months. Unlike its counterpart Spirit, Opportunity did not get stuck in the Martian soil, and is continuing its journey across the vast expanse of Mars, already having traveled 26.7 kilometers. Opportunity gives us a never before seen view of another planet, with many striking similarities to Earth and yet is still extremely different. This photo taken by Opportunity is similar to a photo of the desert in Arizona, with the red hot sun beating down on the planet. And yet, on this sunny day on mars it is probably hundreds of degrees colder, due to its significantly greater distance. As Opportunity continues to collect photographs of the Martian surface, it is fascinating to see how vibrant this planet is, teeming with craters, mountains, and valleys.