Edge-On Spiral Galaxy NGC 891
http://apod.nasa.gov/apod/ap100225.html
This is an edge-on picture of the unbarred spiral galaxy NGC 891. An unbarred spiral galaxy is a spiral-shaped galaxy without a central bar formation. It is about 30 million light years away in the constellation Andromeda. NGC 891 was discovered in 1784 by William Herschel. It is similar to the Milky Way, with a disk shape and bulge in the center. Star formation or supernova explosions are likely causes for the streaks of dust that extend outward from the galaxy.
Friday, February 26, 2010
Thursday, February 25, 2010
Astronomer Biography 3
PERCIVAL LOWELL
Percival Lowell was born on March 13, 1855, into a prominent Bostonian family. He developed interest in many fields during his early schooling, and graduated from Harvard University in 1876 with distinction in mathematics. He traveled around the Far East after graduating, and published several books, including The Sound of the Far East, about his experiences.
After reading La planète Mars by Camille Flammarion and hearing about the supposed Martian canals drawn by Giovanni Schiaparelli, Lowell resolved to devote himself to studying the planet full-time. He decided to build his own observatory using his wealth and resources. He wanted superior conditions so he could make superior observations, so he chose a mesa in Flagstaff, Arizona as the site for his new observatory because of its elevation, clear weather, and distance from lights. This was the first major observatory whose location was deliberately chosen because of optimal conditions for observation.
Lowell obtained some equipment and soon began his work. He published Mars in 1895, in which he supported the presence of canals on Mars and theorized that it was possible that intelligent life existed on the planet. He asserted that the general physical conditions on Mars could allow for life, that there appeared to be arid conditions on Mars so inhabitants would need irrigation systems, and that there were markings on the planet that appeared to be canals. He acknowledged that all this could mean nothing, but personally believed that there was life on Mars.
By 1896 Lowell was observing Mars at night and Mercury and Venus during the day. He took a break from his work when his health deteriorated, but observations at Flagstaff continued. He returned in 1901, and in 1905, he published Mars and its Canals, which was followed by Mars as the Abode of Life in 1908. Both books expanded on his earlier theories; he continued to argue that there was an extensive system of canals on Mars. However, many astronomers did not agree with him, and few believed that the supposed canals were as extensive and regular as Lowell stated. Lowell also supported the idea that the lighter areas on Mars were deserts, while the darker areas were vegetation.
In 1909, the sixty-inch Mount Wilson Observatory telescope revealed that the canals were likely irregular geological features, formed naturally by erosion or other means. The theory was definitively disproved by close-up images taken by Mariner 4 in 1965.
Lowell did not focus solely on Mars. He made maps of Venus and observed unusual features and a dark spot. However, it was later discovered that Venus’s atmosphere was opaque, so these observations were probably imagined; Lowell may have been seeing the blood vessels in his own eye. He confirmed Schiaparelli’s conclusion that Mercury’s rotational period is as long as its orbital period, although later studies revealed that it is actually only two-thirds as long. He helped find an accurate value for Uranus’s rotation and studied the clouds on Jupiter and the structure of Saturn’s rings.
Because of discrepancies in the expected orbits of Uranus and Neptune, Lowell hypothesized that there was an unknown mass near or beyond those planets that was perturbing their orbits. He began a search for this Planet X. This search was not completed during his lifetime, but it led to the discovery of Pluto in 1930. However, Pluto did not have sufficient mass to account for the unexpected orbits of Uranus and Neptune. This was later discovered to be caused by an inaccurate estimate of Neptune’s mass.
Although most of Lowell’s major work turned out to be invalid, he was a very influential astronomer. He started the practice of building observatories at locations with optimal conditions. He was responsible for significantly increasing the general public’s interest in astronomy and especially in Mars. However, his greatest contribution to astronomy was the result of his search for Planet X: the discovery of Pluto.
Works Cited
"Lowell, Percival." Complete Dictionary of Scientific Biography. Vol. 8. Detroit: Charles
Scribner's Sons, 2008. 520-523. Gale Virtual Reference Library. Web. 23
"Lowell, Percival (1855-1916)." The Worlds of David Darling. Web. < http://www.daviddarling.info/encyclopedia/L/LowellP.html >.
"Percival Lowell, Astronomer." The Hunterian Museum and Art Gallery - Scotland's oldest public museum. Web. < http://www.hunterian.gla.ac.uk/archive/mars/percivallowell.html >.
"Percival Lowell." Lowell Observatory. Web. < http://www.lowell.edu/Research/library/paper/lowell.html >.
"Percival Lowell." Universe Today. Web. < http://www.universetoday.com/guide-to-space/astronomy/percival-lowell/ >.
Percival Lowell was born on March 13, 1855, into a prominent Bostonian family. He developed interest in many fields during his early schooling, and graduated from Harvard University in 1876 with distinction in mathematics. He traveled around the Far East after graduating, and published several books, including The Sound of the Far East, about his experiences.
After reading La planète Mars by Camille Flammarion and hearing about the supposed Martian canals drawn by Giovanni Schiaparelli, Lowell resolved to devote himself to studying the planet full-time. He decided to build his own observatory using his wealth and resources. He wanted superior conditions so he could make superior observations, so he chose a mesa in Flagstaff, Arizona as the site for his new observatory because of its elevation, clear weather, and distance from lights. This was the first major observatory whose location was deliberately chosen because of optimal conditions for observation.
Lowell obtained some equipment and soon began his work. He published Mars in 1895, in which he supported the presence of canals on Mars and theorized that it was possible that intelligent life existed on the planet. He asserted that the general physical conditions on Mars could allow for life, that there appeared to be arid conditions on Mars so inhabitants would need irrigation systems, and that there were markings on the planet that appeared to be canals. He acknowledged that all this could mean nothing, but personally believed that there was life on Mars.
By 1896 Lowell was observing Mars at night and Mercury and Venus during the day. He took a break from his work when his health deteriorated, but observations at Flagstaff continued. He returned in 1901, and in 1905, he published Mars and its Canals, which was followed by Mars as the Abode of Life in 1908. Both books expanded on his earlier theories; he continued to argue that there was an extensive system of canals on Mars. However, many astronomers did not agree with him, and few believed that the supposed canals were as extensive and regular as Lowell stated. Lowell also supported the idea that the lighter areas on Mars were deserts, while the darker areas were vegetation.
In 1909, the sixty-inch Mount Wilson Observatory telescope revealed that the canals were likely irregular geological features, formed naturally by erosion or other means. The theory was definitively disproved by close-up images taken by Mariner 4 in 1965.
Lowell did not focus solely on Mars. He made maps of Venus and observed unusual features and a dark spot. However, it was later discovered that Venus’s atmosphere was opaque, so these observations were probably imagined; Lowell may have been seeing the blood vessels in his own eye. He confirmed Schiaparelli’s conclusion that Mercury’s rotational period is as long as its orbital period, although later studies revealed that it is actually only two-thirds as long. He helped find an accurate value for Uranus’s rotation and studied the clouds on Jupiter and the structure of Saturn’s rings.
Because of discrepancies in the expected orbits of Uranus and Neptune, Lowell hypothesized that there was an unknown mass near or beyond those planets that was perturbing their orbits. He began a search for this Planet X. This search was not completed during his lifetime, but it led to the discovery of Pluto in 1930. However, Pluto did not have sufficient mass to account for the unexpected orbits of Uranus and Neptune. This was later discovered to be caused by an inaccurate estimate of Neptune’s mass.
Although most of Lowell’s major work turned out to be invalid, he was a very influential astronomer. He started the practice of building observatories at locations with optimal conditions. He was responsible for significantly increasing the general public’s interest in astronomy and especially in Mars. However, his greatest contribution to astronomy was the result of his search for Planet X: the discovery of Pluto.
Works Cited
"Lowell, Percival." Complete Dictionary of Scientific Biography. Vol. 8. Detroit: Charles
Scribner's Sons, 2008. 520-523. Gale Virtual Reference Library. Web. 23
"Lowell, Percival (1855-1916)." The Worlds of David Darling. Web. < http://www.daviddarling.info/encyclopedia/L/LowellP.html >.
"Percival Lowell, Astronomer." The Hunterian Museum and Art Gallery - Scotland's oldest public museum. Web. < http://www.hunterian.gla.ac.uk/archive/mars/percivallowell.html >.
"Percival Lowell." Lowell Observatory. Web. < http://www.lowell.edu/Research/library/paper/lowell.html >.
"Percival Lowell." Universe Today. Web. < http://www.universetoday.com/guide-to-space/astronomy/percival-lowell/ >.
Friday, February 19, 2010
APOD 3.5
WISE Infrared Andromeda
http://apod.nasa.gov/apod/
This is a picture of the Andromeda galaxy, taken in infrared light and rendered as a false color image. It is a mosaic of pictures taken from the Wide-field Infrared Survey Explorer. The yellow and red portions of the picture consist of dust heated by the galaxy's younger stars, and the blue areas are created by its older stars. Andromeda, or M31, is 2,500,000 light years away and is the farthest object from the Milky Way that is visible with the naked eye. It has twice the diameter of the Milky Way, but may be less massive. 2006 observations by the Spitzer Space Telescope suggest that Andromeda has about one trillion stars, which is large compared to the estimated 200-400 billion stars of the Milky Way.
http://apod.nasa.gov/apod/
This is a picture of the Andromeda galaxy, taken in infrared light and rendered as a false color image. It is a mosaic of pictures taken from the Wide-field Infrared Survey Explorer. The yellow and red portions of the picture consist of dust heated by the galaxy's younger stars, and the blue areas are created by its older stars. Andromeda, or M31, is 2,500,000 light years away and is the farthest object from the Milky Way that is visible with the naked eye. It has twice the diameter of the Milky Way, but may be less massive. 2006 observations by the Spitzer Space Telescope suggest that Andromeda has about one trillion stars, which is large compared to the estimated 200-400 billion stars of the Milky Way.
Wednesday, February 17, 2010
Observations 3.1
2/3/10
9:20 PM
Mars was about 45 degrees above the horizon to the east. It was about 10 degrees east of Pollux. Auriga and Capella were almost overhead, and Sirius was twinkling brightly as usual to the southeast. When facing south, Orion's Belt was about 55 degrees above the horizon.
2/4/10
8:15 PM
Trees and low clouds obscured most of the sky up to 30 degrees above the horizon. I could make out most of Lepus, which is 5 to 10 degrees south of Orion. Mars was about 35 degrees above the horizon to the east. I saw Perseus and the area where Aries is located.
2/11/10
8:30 PM
Mars was close to Cancer in the sky. I saw Orion, Taurus, Auriga, Perseus. I located Eridanus for the first time, but could barely make out most of its stars.
2/16/10
7:20 PM
Stargaze
The moon was in the waxing crescent phase to the west. Mars was to the east. With binoculars, I saw M31 to the northwest, west of Cassiopeia, and the Pleiades, which were overhead. Aries was to the west. I recognized Triangulum for the first time to the west, fairly high above the horizon. The cloud of the Milky Way was faintly visible. I saw the Double Cluster of Perseus southeast of Cassiopeia, Lepus and Columba south of Orion, and the kids in Auriga. I traced Eridanus southwest of Orion. I saw the area of the sky where Monoceros is located, in the middle of Canis Major, Canis Minor, and Orion. I looked at M42 in Orion through the telescope. Sirius appeared to be an even brighter blue through binoculars. With the telescope, I distinguished the double stars of Castor.
9:20 PM
Mars was about 45 degrees above the horizon to the east. It was about 10 degrees east of Pollux. Auriga and Capella were almost overhead, and Sirius was twinkling brightly as usual to the southeast. When facing south, Orion's Belt was about 55 degrees above the horizon.
2/4/10
8:15 PM
Trees and low clouds obscured most of the sky up to 30 degrees above the horizon. I could make out most of Lepus, which is 5 to 10 degrees south of Orion. Mars was about 35 degrees above the horizon to the east. I saw Perseus and the area where Aries is located.
2/11/10
8:30 PM
Mars was close to Cancer in the sky. I saw Orion, Taurus, Auriga, Perseus. I located Eridanus for the first time, but could barely make out most of its stars.
2/16/10
7:20 PM
Stargaze
The moon was in the waxing crescent phase to the west. Mars was to the east. With binoculars, I saw M31 to the northwest, west of Cassiopeia, and the Pleiades, which were overhead. Aries was to the west. I recognized Triangulum for the first time to the west, fairly high above the horizon. The cloud of the Milky Way was faintly visible. I saw the Double Cluster of Perseus southeast of Cassiopeia, Lepus and Columba south of Orion, and the kids in Auriga. I traced Eridanus southwest of Orion. I saw the area of the sky where Monoceros is located, in the middle of Canis Major, Canis Minor, and Orion. I looked at M42 in Orion through the telescope. Sirius appeared to be an even brighter blue through binoculars. With the telescope, I distinguished the double stars of Castor.
Friday, February 12, 2010
APOD 3.4
The Einstein Cross Gravitational Lens
http://apod.nasa.gov/apod/ap100207.html
This is a picture of the Einstein Cross, which is a case of gravitation lensing. The galaxy in the picture appears to have four nuclei rather than one. However, this is highly unlikely; a more probable explanation for what is seen is that the actual nucleus is not visible, and the light that appears to be coming from four sources is actually originating from a single quasar behind the galaxy. The galaxy's gravitational field breaks this light into the four images. Quasars likely form when matter in a large galaxy fall toward a central super-massive black hole. They are the brightest objects in the universe.
http://apod.nasa.gov/apod/ap100207.html
This is a picture of the Einstein Cross, which is a case of gravitation lensing. The galaxy in the picture appears to have four nuclei rather than one. However, this is highly unlikely; a more probable explanation for what is seen is that the actual nucleus is not visible, and the light that appears to be coming from four sources is actually originating from a single quasar behind the galaxy. The galaxy's gravitational field breaks this light into the four images. Quasars likely form when matter in a large galaxy fall toward a central super-massive black hole. They are the brightest objects in the universe.
Friday, February 5, 2010
APOD 3.3
Stardust in Perseus
http://apod.nasa.gov/apod/ap070511.html
This picture shows a region of dust, gas, and stars in the direction of Perseus. Several reflection nebulae are visible in the picture. The largest blue shape is NGC 1333, which is a bright emission and reflection nebula. NGC 1333 is a star-forming region; it contains hundreds of young stars. The red area next to NGC 1333 is hydrogen released by forming stars. Dark dust nebulae are also visible in the picture; these nebulae obscure newly-formed stars and protostars.
http://apod.nasa.gov/apod/ap070511.html
This picture shows a region of dust, gas, and stars in the direction of Perseus. Several reflection nebulae are visible in the picture. The largest blue shape is NGC 1333, which is a bright emission and reflection nebula. NGC 1333 is a star-forming region; it contains hundreds of young stars. The red area next to NGC 1333 is hydrogen released by forming stars. Dark dust nebulae are also visible in the picture; these nebulae obscure newly-formed stars and protostars.
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