APOD 1.8

     The image below captures the beauty of the Great Carina Nebula discovered in 1752 by Nicholas Louis de Lacaille. The Carina Nebula, also known as NGC 3372, is the creator of the one of the most conspicuous, massive, and luminous stars in our Milky Way Galaxy, Eta Carinae. Eta Carinae has a mass about 120 times that of our own Sun. Because of its age and large size, Eta Carinae is expected to explode into supernova or hypernova in the astronmically near future. 

     Although this nebula is an outstanding 7,500 light-years away from Earth, it can still be easily distinguished in the night sky with the naked eye. This image taken by Lorand Fenyes captures the beauty of the interstellar and cosmic dust that make up the nebula. The interstellar dust is made up of particles of carbon, ice, and iron compounds and scatters blue light. This scattering gives the nebula its red color. The clouds that surround the nebula are thick knots of molecular gas and dust that are opaque, but are still less dense than the clouds in Earth's atmosphere.

APOD 1.7

Pictured below is Comet ISON's transit across our sky two weeks ago. Comet ISON was discovered in September 2012 by Vitali Nevski and Artyom Novichonok. This comet will be entering the inner solar system following its hyperbolic trajectory from the Oort Cloud, a spherical cloud of icy cosmic dust grains in the midst of planet formation (planetisimals). The Mars Reconnaissance Orbiter captured the image below as Comet ISON made its closest approach to the planet. The comet itself isn't as bright as astronomers had previously predicted however the low brightness of the tail allows astronomers to observe the nucleus of the comet for more accurate research. As the comet approaches Earth, within the next week, it has the potential to become just as bright or even brighter than the moon, becoming the brightest object in the night sky. The comet will continue its approach into the inner solar system and ultimately pass within a few solar radii of the Sun's surface. If Comet ISON survives the trip near the sun (it reaches perihelion on November 29th) it will pass by the Earth at the nearest point some time in December 2013.

Christen Sørensen Longomontanus

Christen Sørensen (born as Christian Severin; also known as Longomontanus) was born in Longberg, Denmark in 1562. Born in to a poor family, Sørensen did not complete his education until the age of twenty-six. In 1590, Sørensen began working at Tycho Brahe's observatory, Uraniborg, as his primary assistant. Working for Brahe allowed Sørensen some close insight of Brahe's advanced astronomical research and observations. However, the two worked so closely that it is difficult to distinguish specifically how and what Sørensen contributed to Brahe's work. Some sources attribute the development of Tycho's Lunar Theory to Sørensen as he was the one who surpervised the compilation of Brahe's star catalog. Upon Tycho's death and in Sørensen's absence, Johannes Kepler , another assistant to Brahe, took it upon himself to continue Brahe's research using his own methods. Sørensen attempted to dissuade Kepler of his methods and ultimately never accepted Kepler's findings and research.

Sørensen managed to carry on Tycho Brahe's legacy without the key component of his observations and star charts (in Kepler's possession at the time). Sørensen is acknowledged for writing a testimonial for Brahe's work: Astronomica Danica (published in 1622). In this testament, Sørensen detailed the various geocentric (Ptolemaic and Tychonic) and heliocentric (Copernican) models while finally expressing his support for the Tychonic system, a combination of the planetary motions of the Copernican model and the geocentrism of the Ptolemaic model.

In 1597 Uraniborg was forced to shut down and Sørensen was left to pursue his education independently. At first he was able to continue working for Tycho Brahe (during which time the Lunar theory was established), but after Brahe's death in 1601, Sørensen began touring German universities and soon found his niche at the University of Copenhagen. In 1605, Chancellor Christian Friis of the University of Copenhagen sponsored Sørensen and he became a well known professor. By 1621, Sørensen transitioned from a professor of mathematics to a professor of astronomy and higher mathematics. Sørensen has left his legacy at the University of Copenhagen by establishing a tradition of astronomical education and drafting the Round Tower observatory; he was unable to see its completion before his death on October 8th, 1647.

Christen Sørensen is an often overlooked figure in the astronomical world. Although his contributions to the development of theories of planetary motion in the 17th century were extremely valuable, he is often hidden behind the shadow of Tycho Brahe and other great astronomers of the time period. 

APOD 1.6

The image below shows the remnants of the explosion of a star in the constellation Vera, part of a group of constellations called Argo. The explosion of the star is thought to have been seen by the earliest humans in recorded history, but its aftermath is still visible today. When the star first exploded, the outer layers of the destroyed star pushed into the interstellar medium surrounding the star. This interstellar medium consists of large clouds of mostly hydrogen that are usually hard to detect as they emit very little light and absorb few, very specific wavelengths of light. The clashing of the outer layer of the star and the interstellar cloud created a spherical shock wave that is observable with x-rays. The image below shows the filaments of the shock wave, which are colored as the escaping gas decays and reacts with the interstellar medium. Sitting at the center of the explosion is a pulsar, a dense, highly-magnetized, rotating neutron star. This particular neutron star rotates completely ten times within one second.