This is the APOD of October 20, 2007. It was taken in Fort Davis, Texas, on an almost moonless night. This is obviously a picture of the Milky Way, but taken so as to seem like it's just an extension of the dirt road. The picture is composited and one of the links actually leads to a photo gallery of composited pictures that deal with astronomical events (it's actually pretty cool. One of the pictures looks like a guy is about to walk into a nebula or exploding star or something). The APOD goes on to talk abotu the origins of the name Milky Way and the name galaxy (which apparently derives from the Greek word for milk. Cool beans.) One link shows alternate names for the M.W. like Silver Road, Bird's Path, and so on. The appearance of the Milky Way itself is due to innumerable stars and dark galactic clouds. Yay Galileo.
Friday, October 26, 2007
APOD 2.1
This is the APOD of October 20, 2007. It was taken in Fort Davis, Texas, on an almost moonless night. This is obviously a picture of the Milky Way, but taken so as to seem like it's just an extension of the dirt road. The picture is composited and one of the links actually leads to a photo gallery of composited pictures that deal with astronomical events (it's actually pretty cool. One of the pictures looks like a guy is about to walk into a nebula or exploding star or something). The APOD goes on to talk abotu the origins of the name Milky Way and the name galaxy (which apparently derives from the Greek word for milk. Cool beans.) One link shows alternate names for the M.W. like Silver Road, Bird's Path, and so on. The appearance of the Milky Way itself is due to innumerable stars and dark galactic clouds. Yay Galileo.
Friday, October 12, 2007
Biography - James Gregory
James Gregory (more correctly spelled Gregorie) was born in Drumoak, Scotland in 1638. In his early years, he was taught by his mother, Janet Anderson, whose brother, Alexander Anderson, was a student of François Viète, a French mathematician and astronomer. After his father’s death, Gregorie was sent by his older brother David to Aberdeen in order to attend grammar school. Gregorie later attended Marischal College.
Gregorie moved to London in 1662, where he befriended Robert Moray of the Royal Society and published Optica Promota. In Optica Promota, Gregorie proves a reflective sine law that, unbeknownst to him due to his rural location when he worked on the book, Descartes had already proven (known as Descartes law of sines). In fact, though Gregorie puts forth many ideas about lunar, solar, and stellar parallax and other astronomical ideas and applications, many of these had already been promoted by other current astronomers. Gregorie simply wasn’t aware of the current knowledge at the time the book was written. He did, however, describe a method for the use of Venus’s transit in order to measure the distance of the Earth to the Sun (or the Astronomical Unit). Edmund Halley, the English astronomer, would later promote Gregorie’s method and it would become the basis of the first effective measurement of the Astronomical Unit.
Gregorie’s most important contribution to astronomy in the Optica Promota was his design for a new telescope, located in the Epilogue. Gregorie believed that a telescope that utilized both mirrors and lenses, rather than one or the other, would correct several defects in the current design of telescopes. In his new design, the “catadioptrical” telescope, a parabolic mirror reflects parallel incident rays to a primary focus. The light is then reflected back through a hole in the center of the first mirror by a small concave elliptical mirror to a secondary focus, and from there through a plano-convex lens to the eye. Gregorie used the available books in Aberdeen on optics and astronomy to create this telescope, including Kepler’s Paralipomena. Gregorie was unable to actually create the telescope, but in 1663 Robert Hooke created a six foot telescope of Gregorie’s design. However, Isaac Newton, with whom Gregorie would later correspond, objected that Gregorie dialed to polish the conical mirrors correctly and in about 1668 Newton reveals an improved design to Gregorie’s original telescope. Gregorie actually wanted to build an observatory at St. Andrews, where he taught, and teach the “new” science, but the students had rebelled against the faculty and administration would not permit Gregorie to do so.
Some of Gregorie’s most important additions to scientific knowledge actually came in the form of mathematics. Gregorie began to embrace his mathematics side in Italy, where he moved in late 1663, to study under Evangelista Torricelli’s pupil Stefano degli Angeli. Gregorie published Vera circuli et hyperbolae quadratura in 1667 and Geometrioe pars universalis in 1668. Gregorie determined that quadrature of the circle (making a square with a straight edge and a compass that had the same area as a circle) was impossible. Additionally, he proposed that the areas of a circle and hyperbola could be obtained in the form of infinite convergent series. He was also one of the first modern mathematicians to think about transcendental numbers, such as pi and e. Furthermore, his work provided the basis for the Taylor series, a way to make sine, cosine, and logarithmic functions be able to be described in polynomial terms.
James Gregorie died in 1675 in Edinburgh, Scotland. He was showing his students Jupiter’s satellites through a telescope when a stroke blinded him. He died a few days later.
Gregorie moved to London in 1662, where he befriended Robert Moray of the Royal Society and published Optica Promota. In Optica Promota, Gregorie proves a reflective sine law that, unbeknownst to him due to his rural location when he worked on the book, Descartes had already proven (known as Descartes law of sines). In fact, though Gregorie puts forth many ideas about lunar, solar, and stellar parallax and other astronomical ideas and applications, many of these had already been promoted by other current astronomers. Gregorie simply wasn’t aware of the current knowledge at the time the book was written. He did, however, describe a method for the use of Venus’s transit in order to measure the distance of the Earth to the Sun (or the Astronomical Unit). Edmund Halley, the English astronomer, would later promote Gregorie’s method and it would become the basis of the first effective measurement of the Astronomical Unit.
Gregorie’s most important contribution to astronomy in the Optica Promota was his design for a new telescope, located in the Epilogue. Gregorie believed that a telescope that utilized both mirrors and lenses, rather than one or the other, would correct several defects in the current design of telescopes. In his new design, the “catadioptrical” telescope, a parabolic mirror reflects parallel incident rays to a primary focus. The light is then reflected back through a hole in the center of the first mirror by a small concave elliptical mirror to a secondary focus, and from there through a plano-convex lens to the eye. Gregorie used the available books in Aberdeen on optics and astronomy to create this telescope, including Kepler’s Paralipomena. Gregorie was unable to actually create the telescope, but in 1663 Robert Hooke created a six foot telescope of Gregorie’s design. However, Isaac Newton, with whom Gregorie would later correspond, objected that Gregorie dialed to polish the conical mirrors correctly and in about 1668 Newton reveals an improved design to Gregorie’s original telescope. Gregorie actually wanted to build an observatory at St. Andrews, where he taught, and teach the “new” science, but the students had rebelled against the faculty and administration would not permit Gregorie to do so.
Some of Gregorie’s most important additions to scientific knowledge actually came in the form of mathematics. Gregorie began to embrace his mathematics side in Italy, where he moved in late 1663, to study under Evangelista Torricelli’s pupil Stefano degli Angeli. Gregorie published Vera circuli et hyperbolae quadratura in 1667 and Geometrioe pars universalis in 1668. Gregorie determined that quadrature of the circle (making a square with a straight edge and a compass that had the same area as a circle) was impossible. Additionally, he proposed that the areas of a circle and hyperbola could be obtained in the form of infinite convergent series. He was also one of the first modern mathematicians to think about transcendental numbers, such as pi and e. Furthermore, his work provided the basis for the Taylor series, a way to make sine, cosine, and logarithmic functions be able to be described in polynomial terms.
James Gregorie died in 1675 in Edinburgh, Scotland. He was showing his students Jupiter’s satellites through a telescope when a stroke blinded him. He died a few days later.
Works Cited
"James Gregory (Astronomer and Mathematician)." Wikipedia. 09 Oct. 2007 .
"James Gregory." Dictionary of Scientific Biography. 6th vol. New York: Charles Scribner's Sons, 1981.
Group Observation at Suncoast Community Church
From 7:40-9:00 I observed with the group and Mr. Percy at the church. It took a while to get the telescope set up, but when it was, we first observed Jupiter and its four moons. The first three moons appear closer to Jupiter, orbiting it in almost even rings around the moon (or at least that's what it looked like), but the fourth moon, Callipto, was much farther away from the planet. When we put a higher intensity eyepiece into the telescope, we could more easily percieve the two dark bands on the planet. With my binoculars (7x35 mag, or 580 at 1000 ft), I could see a few moons outside Jupiter but with difficulty - if I hadn't know they were there, I would have assumed that the moons were just fuzzy dots because I couldn't stay still. Mr. Percy used a green laser to point out Constellations and we could easily see: Scorpius, the teapot/Sagittarius, Cepheus, Andromeda, the Square Pegasus, Hercules, the constellations Altair, Cygnus, Lyra and more importantly their stars for the Summer Triangle. The constellations are much bigger than I thought, and you can actually see all of them in a field as opposed to at my house, where there are too many trees to see clearly.
Through the telescope we also observed Epsilon lyrae, Albiero (beta Cygnie, where we looked for the different colors of the stars - the fainter one was blue, the brighter one more yellow-white). Through my binoculars I could also see M31, a galaxy and a satellite galaxy next to it. I didn't realize you could see so much more with the binoculars, but I saw nebulas and galaxies with them.
It was pretty rockin' awesome.
Through the telescope we also observed Epsilon lyrae, Albiero (beta Cygnie, where we looked for the different colors of the stars - the fainter one was blue, the brighter one more yellow-white). Through my binoculars I could also see M31, a galaxy and a satellite galaxy next to it. I didn't realize you could see so much more with the binoculars, but I saw nebulas and galaxies with them.
It was pretty rockin' awesome.
APOD 1.7
This picture is of the shells around galaxy NGC 474, near the constellation Pisces. Astronomers aren't certain if the shells are tidal tails or density waves. Tidal tails happen when a galaxy enters another galaxy's gravity and one gets slung around the other, causing the gravity to rip some stars and planets out of a galaxy's gravity and giving it a tail like appearance. Density waves, on the other hand, look more like shells around the galaxy and happen when one galaxy merges or attacks or crashes into or whatever another galaxy. Either way, the shells are probably caused by galaxy on galaxy contact. Whatever the reason, this picture supports the idea that large galaxies have halos created by interactions with smaller galaxies. This suggests the origins of the halo around our own Milky Way galaxy.
Friday, October 5, 2007
1.6 APOD
The APOD of October 2, 2007 shows an analemma that features a total solar eclipse. An analemma is when a photographer goes outside everyday at exactly the same time and takes a picture of the sun (this is the result - a figure 8 pattern). This particular picture features a solar eclipse and as such is called a Tutulemma (because of the Turkish word for eclipse). One of the links is "great planning" which takes you to a picture on wikipedia of a train that crashed out of the two story station.... Wow. Astronomers have a weird sense of humor.
The sun's apaprent shift is caused by the rotation of the Earth and by the tilt of Earth's axis. The solar eclipse in this picture is from March 29 of 2006. The base image is from that date, in Turkey.
(I wanna go to a water park in Turkey to watch a total solar eclipse...)
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