Jan H. Oork Biography

Born in 1900, Jan H. Oort was one of the greatest astronomers of the twentieth-century. Oort, who lived to be ninety-two, made a number of very important discoveries regarding astronomy, especially regarding galactic motion. Born in Franeker, Friesland, Oort later moved to the United States to study at Yale University. Oort moved back to the Netherlands after graduating from Yale, and that was where he spent the rest of his career.

Oort began his career in astronomy as a text book writer. He eventually became the director of the Leiden Observatory and worked as secretary and president of the International Astronomical Union. Working with both theoretical and observed date, Oort made many important contributions to astronomy, beginning with one he made while still in his early twenties.

Oort first impressed the astronomy world when he proved that the Milky Way is rotating, using Kapteyn’s two streams of stars as evidence. He also used the motion of the stars surrounding the Sun to show that the Sun is not located in the center of the galaxy, but in fact, it is found more than half way into the disk from the nucleus. He also discovered that the center of the galaxy is located in the constellation Sagittarius. In addition, Oort was the first to discover dark matter, which is matter that does not emit enough radiation to be detected. It is now believed that over 90% of the galaxy is made up of the substance.

Another contribution made by Oort was his foresight in the area of radio astronomy. He was one of the first scientists to believe that radio waves could be used to map out the galaxy. Prior to the use of radio astronomy, Oort hypothesized that the galaxy’s spiral arms, were rich in hydrogen and were areas of star formation. As a result or World War II, radio technology was improved and eventually used to prove Oort’s hypothesis to be correct.

Oort’s most famous contribution was probably the theoretical discovery of the Oort Could. Named for the astronomer, the cloud has never been observed, but it is commonly accepted amongst astronomers that the cloud exists. The Oort Cloud lies far beyond Pluto encircling the outer edge of the galaxy. After studying long-period comets, Oort found that most seemed to come from the area that he designated as the Oort Cloud, and he proposed that this cloud is the home to 100,000s of comets.

One interesting anecdote about Oort’s life is that he was one of the few people able to see the Halley’s Comet twice. He saw it for the first time when he was ten years old, and again when he was eighty-six.

Oort made major contributions to the field of astronomy. He was honored with many prestigious awards including the Bruce Medal and the Vetliesen Prize, and is remembered as one of the greatest astronomers in modern history.

Works Cited

"Comet Pioneer: Jan Hendrik Oort." Space Science. 27 Feb. 2004. European Space Agency. 19 May 2008 .

"Jan Hendrick Oort." The Bruce Medalists. 19 May 2008 .

Wilford, John N. "Jan H. Oort, Dutch Astronomer in Forefront of Field, Dies At 92." 12 Nov. 1992. New York Times. 19 May 2008 fullpage.html?res=9E0CE6DF1531F931A25752C1A964958260&sec=&spon=&pagewanted=1>.

4.7 APOD

This is a photo taken from on board the International Space Station. The picture shows a spacecraft, called Soyuz TMA-12, bringing new supplies and members to the ISS. Three new astronauts were delivered on this mission. In the shot, you can see the docking system used to connect the spacecraft to the ISS. The supplies brought by the Soyuz TMA-12 will help astronauts make repairs to the ship, and do research regarding the effects of radiation on vitamin molecules and better ways to live in space. The ISS is currently orbiting about 350 km from Earth's surface and it can be seen by observors with the naked eye. The ISS is run in cooperation between several differnt countries including the United States, Russia, Canada, and Japan, among others.

4.6 APOD

The giant black nebula rests on top of a thick star field. The dark black nebula, made up of dust and gas, is likely a star forming region. Located in the constellation Scorpio, the nebula spans up to 40 light-years across. The dark black cloud, a cometary globule, is shaped by the ultrviolet radiation that is emitted by the bright stars that surround it. The red color comes from hydrogen gas. The small blue reflection nebulae around the dark cloud are hot young stars embedded in cosmic dust. Some say that the dark cloud looks ominous against the bright background. The name dark tower is an allusion to Shakespeare's play "King Lear," in which Gloucester's son Edgar acts as though he is a crazy begger, named Tom. Tom says, "Child Rowland to the dark tower came, His word was still 'Fie, foh, and fum, I smell the blood of a British man'." This was also referenced in a poem by Robert Browning.

4.5 APOD

This is a really cool picture of NGC 6188. This emission nebula is located about 4000 light-years away in the constellation Ara. The glow comes from the intense ultraviolet radiation and stron winds emitted by the young stars in this cluster which is only a few million years old. The area of young stars likely developed as a result of strong winds and supernova explosions that may have compressed molecular gas. Spanning about 300 light-years across, the false color photograph was taken by the Hubble. The colors come from the ionization of hydrogen, sulfer, and oxygen, which create red, green and blue shades in this picture. This nebula can be seen in the Southern Hemisphere, although it requires a very strong telescope to see the large cloud in any detail.

4.4 APOD

This nebula was created by the interaction between dust and gas with the light and wind from hot young stars. Known as the Fox Fur Nebula, it is located in the constellation of Monoceros. The Fox Fur Nebula is just a small section of a larger area known as The Christmas Tree Cluster. The red color in the photograph comes from ionized hydrogen gas. The blue comes from dust clouds that are reflecting light. This is located just north of the Cone Head Nebula, a mysterious star nursery. The Fox Fur Nebula is located about 2500 light-years away from earth.