Friday, April 4, 2014

APOD 4.2

The image below is one of the Veil Nebula, also known as the Cygnus Loop, located in the constellation of Cygnus 1,500 light-years away from Earth. It spans about 6 times the diameter of a full moon across the night sky (approximately 3 degrees). This translates to about 70 light-years across. The Veil Nebula is a supernova remnant. The gas and filaments of dust are still expanding from the massive explosion signaling the death of a star. The light from the supernova originally reached Earth about 5,000 years ago. The glowing gas is a result of the shock waves from the explosion of the star traveling through and exciting interstellar material. The red portrays atomic hydrogen and the blue portrays oxygen gas. The brightest portions of the Nebula are regarded as separate nebulae such as The Witch's Broom (along the top) and Pickering's Triangle (bottom right off-center).

Thursday, March 27, 2014

APOD 4.1

The image below is one of the constellation of Orion and M78 as well as other bright reflection nebula in the constellation. These include The Witch Head Nebula, Nebula NGC 1435 and Nebula NGC 1999. M78 and NGC 2078 are pictured below while the other reflection nebulae are not. M78 is five light years across and can be observed through a small telescope. M78 is contained in Orion's Molecular Cloud Complex that also contains the Great Nebula in Orion and the Horsehead Nebula. The fractal interstellar dust surrounding these nebulae absorbs light and also reflects the light of recently formed blue stars in the nebula. The same type of light scattering that occurs in our daytime sky occurs in this image creating the bluish hues portrayed in the image. 

Thursday, March 6, 2014

Henrietta Swan Leavitt Biography

                Just a little over a century ago, astronomer Henrietta Swan Leavitt made a remarkable discovery. Her discovery became a keystone in shaping modern astronomy. However, she was acclaimed only posthumously; she had no reward nor recognition from her peers for her amazing discovery.

                Henrietta Swan Leavitt was born in Cambridge, Massachusetts in 1869. She was the daughter of a Congregational minister which led to her strong role in her church and community. She followed a rigorous course of education from a young age. At age 20 she entered Radcliffe College and studied a broad variety of subjects: classical Greek, fine arts, philosophy, analytical geometry and differential calculus. Her advanced course work and exceptional achievements at school were enough to build a solid foundation for a successful career at school. Several years after graduation, she fell ill and her serious illness left her almost completely deaf. As she recovered from her illness she volunteered at the Harvard College Observatory and seven years later (1893) she was granted employment. However, at the time Henrietta entered the workforce, women were subjected to the prejudice that men were superior. She was labeled as a lowly book-keeping  'computer' in charge of cataloguing the brightness of stars. She earned a mere 25 cents an hour- the pay of a servant. She surpassed the qualifications to be hired as an astronomer or even a junior astronomical researcher, yet she was held back from her full potential because of her gender. She worked in a tight quarters with other female astronomers in a similar position under the leadership of Edward Pickering who "chose his staff to work, not to think" (Payne, AAVSO).

                Early in her career, Leavitt focused on Cepheid variables, a type of star that varies between larger, brighter states and smaller, dimmer ones. Even having personally discovered 2,400 (about half of the known total in her day) new variable stars, she received little recognition. Leavitt is also credited with the development of the Harvard Standard, a standard of photographic measurements that was officially accepted by the International Committe on Photographic Magnitudes in 1913. Her most remarkable recognition (1912) occurred while she was recording the various data on her Cepheid variables. She found an accurate and consistent relationship between the period of a given star's brightness and its absolute magnitude. This simple relationship made it possible, for the first time, to accurately measure stars' distances from Earth. Leavitt's discovery was published under Edward Pickering's name, making only one reference to Leavitt as the person who had simply 'prepared' the data. Leavitt's discovery catalyzed many more discoveries in the astronomical community. Many famous astronomers such as Edwin Hubble and Ejnar Hertzsprung would not have been able to make their contributions to astronomy without Leavitt's discovery.

                Little is known about Leavitt's personal life as she left behind no diaries or memoires and she kept mostly to herself. Her peers remembered her as having a shy disposition so no one could tell how she dealt the frustrations of her debasement because of her gender. However, one of her peers described her as "possessing the best mind at the Observatory" (PBS). She lived so quietly that her death in 1921 went almost completely unnoticed. In 1925 the Swedish mathematician Gösta Mittlag-Leffler wrote her a letter nominating her for the Nobel Prize in Physics for 1926. He was completely unaware that she had passed away four years ago and Harlow Shapley, Pickering's successor attempted to steal her Nobel Prize by replying to Mittlag-Leffler taking credit for Leavitt's discovery.

                Even today, Henrietta Leavitt's name is not as recognized as it should be considering her discovery radically changed modern astronomy. Her only lasting recognition is a minor lunar crater and a virtual space theatre that bear Henrietta Swan Leavitt's name. One can only hope that the day will come when Henrietta Leavitt receives the recognition she deserves.

Monday, February 24, 2014

Astronomer Biography Sources - Henrietta Leavitt

"Henrietta Leavitt." PBS. PBS, 1998. Web. <http://www.pbs.org/wgbh/aso/databank/entries/baleav.html>.

"1912: Henrietta Leavitt Discovers the Distance Key." Everyday Cosmology. Observatories of the Carnegie Institution for Science, n.d. Web. <http://cosmology.carnegiescience.edu/timeline/1912>.

"Henrietta Leavitt." Henrietta Leavitt. She Is an Astronomer, n.d. Web. <http://www.sheisanastronomer.org/index.php/history/henrietta-leavitt>.

"Henrietta Swan Leavitt - Lady of Luminosity." The Woman Astronomer. The Woman Astronomer, 01 Jan. 2008. Web. <http://www.womanastronomer.com/hleavitt.htm>.

Friday, February 14, 2014

APOD 3.5

The image below shows Asteroid Itokawa. This image was taken by the Hayabusa spacecraft launched by Japan to better understand the composition of asteroids. In addition to taking images, the spacecraft determined the mass of the asteroid by measuring the attraction of the drifting Hayabusa spacecraft. Some of the composition of the asteroid were also studied with the debris from the impact of pellets fired from Hayabusa to Itokawa. The mysterious surface of the asteroid is astoundingly devoid of craters.One hypothesis to explain this oddity is that Itokawa is simply a floating mass of rock and ice chunks loosely held together by the weak gravitational force. If craters ever formed, the rocks and ice would merely settle in those places covering up the craters. Upon further research, astronomers discovered that one part of the interior of the asteroid Itokawa has a much higher average density than the other part.

Friday, February 7, 2014

APOD 3.4

The image below is of Herbig-Haro object 24 taken by the Hubble Space Telescope in infrared light. Herbig-Haro objects are small patches of nebulosity associated with newly born stars. They are formed when thin jets of gas ejected by younger stars collide with clouds of dust and gas. Herbig-Haro objects are everywhere in star-forming regions and many form aorund a single star. Because of the rarity of them, astronomers estimate they only last a few thousand years. The star forming region is located 1,500 light years away from Earth in the Orion B molecular cloud complex. The jet in HH24 contains electrons and protons moving at hundreds of kilometers per second and it is studied to better understand young stellar objects (stars in the earliest stages of development). The dust and gas that encircles these baby stars often contribute to the formation of powerful jets.

Friday, January 31, 2014

APOD 3.3

The image below shows the spiral galaxy M83 (otherwise known as The Southern Pinwheel). This is one of the closest and brightest spiral galaxies in the sky. It is located in the constellation of Hydra (visible in April at 9 PM) and it is easily observed with binoculars. M83 is located 15 million light-years away. It is the perfect place to observe supernova remnants as well as the various stages of the stellar birth and death (spanning over 50,000 light-years). The newest generation of stars (roughly 1 million years old) are visible in large clusters at the edge of the spiral arms. The surrounding gas clouds absorb the ultraviolet light that these stars generate which gives the galaxy the spots of pink light. The stellar winds from the youngest, most massive stars blow away some of this gas revealing bright blue star clusters. The older stars in the galaxy appear yellow or orange.