APOD 2.7

Since we are studying the Sun, I decided to choose this image of a "Sun halo"  taken in Stockholm.  Due to the snowy, frigid weather and dryness of the air, there are millions of ice crystals ( hexagonal and symmetrical in structure) in the atmosphere.  These ice crystals are acting like lenses, which basically just means that they are bending rays of light (or refracting) creating two virtual images of the Sun on the left and right side of the actual Sun.  The scientific phenomenon behind ice crystal halos is similar to what causes rainbows, which are produced when sunlight is reflected off of and refract water droplets.   As sunlight enters through one end of the ice crystal's face and exits through an opposing face, it results in a refracting angle typically of 22 degrees (calculated by finding the angle of minimum deviation by using the index of refraction that equals 1.31 and  the apex angle of a prism that equals 60 degrees).  These halos (also called sun dogs) are best seen when the Sun appears to be low in the Earth's atmosphere, such as sunset, because these ice crystals tend to flutter down towards the ground      

Images of the Sun

This link provides a photo of the Sun taken by a radio telescope and shows the sunspots as well as the magnetic fields. 
http://www.astro.umd.edu/~white/images/93nov07_c_r_full.html

This link has a variety of impressive images of features such as solar flares, prominences, eclipses and an animation of the Sun rotating that was taken using several composite images over the course of 6 days from an ultraviolet telescope.
http://www.boston.com/bigpicture/2008/10/the_sun.html

Finally this link is from the website for SOHO (The Solar and Heliospheric Observatory) and provides a gallary of images of the Sun's corona.
http://sohowww.nascom.nasa.gov/gallery/SolarCorona/

Astronomer Biography

Pierre Méchain was born on August 16, 1774 in Laon which is in Northern France.  Pierre’s father was a ceiling plasterer and his mother had attempted to follow a similar architectural career, but did not succeed.  At a young age, Pierre Méchain was recognized for his talents in mathematics and was sent by the French nobility to école des Ponts et Chaussées, located in Paris.  However, his studies ended early after two years due to his family’s lack of finances to support him.  Shortly after this interruption, Pierre accepted a tutorship for two young nobleman.  At some unknown point Pierre became friends with Jérôme de Lalande who was finishing his book L'Astronomie and let Méchain read segments of it.  As Pierre quickly proved he had promising potential in the field of Astronomy, Lalande offered him a temporary position as hydrographer at the naval archives in Versailles, which forced Pierre to supplement his income  teaching mathematics.  Although Méchain was removed twice since his position was not meant to last for very long, he was continually reinstated for his exceptional talent at map making and his maps were used to chart the shoreline from Nieuwpoort in Flanders to Saint-Mato. 

During his time creating these naval archives, Pierre Méchain intently studied Astronomy and made significant achievements in the field, such as the discovery of two comets and calculated their orbits and also proved that the comets appearing in 1532 and 1661 were not the same object contrary to popular belief, earning him the award Académic Royale des Sciences in 1782.  After being recognized for his efforts, Pierre decided to invest more and more time into working towards new astronomical discoveries and he was able to find nine more comets and thirty deep sky objects, resulting in Méchain coordinating efforts with Charles Messier to catalog these new celestial objects.  Pierre earned the position as editor of the French almanac “Connoissance des temps” in 1785, which he held for six years. 

In 1787 a project developed attempting to improve the precision and accuracy of various scientific instruments that would be orchestrated by both the British and the French, ho are well known rivals.  Méchain was chosen to work on the project along with the astronomers Cassini and Legendre.  The group was able to lessen the distortion of telescopes by clamping a circle to it and by using it to measure angles at multiple segments of the circle, graduation errors were greatly diminished.  Another famous and revolutionary achievement made by Pierre Méchain was the fact that he was chosen as a member of the committee to create a decimal system of measurement, which was a project approved by the National Assembly, the legislative body of the French government at that time.  As the French Revolution wreaked havoc all around Méchain, he was arrested because he was carrying suspicious equipment, such as parabolic mirrors for reflecting signals in order to measure the meridian, and was suspected of being a traitor of the Revolution.  After two months spent in incarceration, Méchain and his associates were released and travelled to Spain to continue their scientific progress.  However, Pierre’s astronomical work was interrupted when he was asked to inspect a hydraulic pump and got caught in the machine, resulting in the breaking of his ribs, collarbone and the inability to use his right arm as well as the loss of consciousness for three days.  After the accident and the loss of many of his friends, who died at the guillotine, Pierre Méchain became a strange and cantankerous man.  Méchain was able to discover two more comets, became the director of the Paris Observatory before his death from yellow fever in Spain on September 20, 1804.                      

APOD 2.6

As an unfortunate person who has never had the privilege of spotting the amazing green flash effect that occasionally appears at the end of the sunset, I was very intrigued by this APOD and hope to be able to spot one in the future now knowing its cause.  The phenomenon of the green flash and the even rarer blue flash that occurs as the sun sets is pictured here and was taken in Spain.  A viewer's visibility of the green flash requires that the land is flat and has a distant horizon, such as over an Ocean.  It is a common misconception that the green flash is a result of a reaction in our eyes where the red cones are saturated therefore causing the green flash to occur as an after image.  The true cause of the green flash can be explained by the basic properties of Earth's atmosphere.  As light enters the Earth from the Sun it slows down and refracts, which at sunset or sundown means it bends downwards.  The blue light is bent more than the red light in the atmosphere because it is nearer to the ultraviolet frequencies (shorter wavelengths) and is slowed down more.  The flash appears green because the blue light is scattered more than the green light in the atmosphere and usually the blue is entirely removed, except in this rare case where both can be seen.  Both the green and the blue flash were able to be seen in this photograph because the atmosphere was astoundingly clear and did not scatter the blue light as much as it normally would have.      

Biography Sources

"Méchain, Pierre-François-André." Complete Dictionary of Scientific Biography. Vol. 9. Detroit: Charles Scribner's Sons, 2008. 250-252. Gale Virtual Reference Library. Web. 6 Jan. 2011.

 

Frommert, Hartmut and Christine Kronberg.  "Pierre François André Méchain."  Students for the Exploration and Development of Space.  19 May 2008. <http://seds.org/messier/xtra/history/pmechain.html>  

 

Observation Post

While kyak camping from December 27th- December 30th as apart of a group called Paddle Florida, I was able to estimate the star visibility to be at 4th magnitude.  The light pollution in the Deland area, where most of the camp sites were located near, is far less detrimental to star gazing as Sarasota's.  It was truly incredible to be able to see at least twice as many stars in the sky as I am normally able to find.  I easily spotted Jupiter, the constellation Orion, Pegasus and Cassiopeia, but with improved visibility I also saw Capricorn and Pisces. 

Observation Post

Over the break, on the night of December 21st, I viewed the lunar eclipse at 3:30 AM and a meteor flash across the sky around 10 PM.  This meteor was likely apart of the Ursids meteor shower that occurred that night.  This astronomical combo of events was really exciting to watch.  The moon actually appeared much smaller than I had predicted, since I expected it to be the size of the Harvest moon.  Also the moon was at a rust orange at this stage.  This lunar eclipse was considered unique to astronomers since it also marked the day of winter solstice, which happens only three times between 1638 and 2094!