Allan Sandage Biography

Allan Sandage

Allan Sandage was an American astronomer born in 1926 who died in 2010. Sandage worked with Carnegie Observatories in Pasadena, and is distinguished for approximating the Hubble constant and the age of the universe.

Sandage's influence is pervasive. After graduating from the University of Illinois, he obtained his Ph.D. from Caltech, advised by Walter Baade, a German astronomer. He actually was a grad student assistant of Edwin Hubble, perhaps influencing his work related to Hubble's constant. He continued in Hubble's footsteps, carrying on his research program after Hubble's death. Baade then discovered two populations of Cepheid variables in the Andromeda Galaxy. Since Hubble had only considered one of the populations, the estimate of the age of the universe doubled from 1.8 to 3.6 billion years. Sandage demonstrated that H II regions do not comprise stars and are inherently brighter than stars in distant galaxies, contrary to the assumption that the brightest stars in galaxies are of equal intensity. This increased the age of the universe yet again to 5.5 billion years.

From the 1950s to the 1980s, Sandage was the premier observation cosmologist (study of the universe). He used a variety of methods for measurement, from local indicators in the Milky Way to extremely distant galaxies. In 1958 Sandage started to work at the Palomar Observatory. It was from there that he published the first reasonable estimate of the Hubble constant, the ratio of the recession velocity of a distant object to its "proper distance." Sandage's value was 75 km/s/Mpc, much lower than Hubble's 250 km/s/Mpc. This is quite impressive, considering one 2011 study estimated it at 73.8 km/s/Mpc. However, he later decreased his estimate even further to 50 km/s/Mpc, corresponding to a Universe age of 20 billion years!

Sandage utilized photometry on globular clusters, coming to the conclusion that they were about 25 billion years old. Accordingly, he concluded that the Universe expanded and contracted with a period of 80 billion years. However, most estimates place the Universe as 14 billion years old. He co-wrote an extremely influential paper with Eggen and Lynden-Bell on the collapse of a proto-galactic gas cloud into the Milky Way. Sandage wrote a paper called "The Ability of the 200-inch Telescope to Discriminate Between Selected World Models" wherein he described observational cosmology as essentially a search for the Hubble constant and the deceleration parameter q₀. He basically created a blueprint for how to use a large telescope to perform observational tests. He published an atlas of galaxies that employed the Hubble classification scheme in 1961 and again in 1981.

He devised a way to measure the temporal variation of extra-galactic redshift, which became known as the Sandage-Loeb test. He also discovered jets erupting from the core of the M82 galaxy, which had been occurring for 1.5 million years. He stayed at Carnegie Observatories up until his death, having published over 500 papers in his life.

APOD 4.5

18 May 2011 - The Last Launch of Space Shuttle Endeavor

On Monday, the shuttle Endeavor launched for the last time. It carried six astronauts and docked with the International Space Station. They are going to deliver an apparatus that can detect antimatter, dark matter, and strangelets called the Alpha Magnetic Spectrometer. Dark matter is any matter whose existence can be deduced based on gravitational effects on the surroundings but cannot be "seen" by usual means. Antimatter is a counterpart to normal matter (much less abundant than it) and when combined with matter, causes fulminating cataclysms. Strangelets are objects that have strange combinations of up and down quarks. The last shuttle launch will occur in mid-July, and I will endeavor to go see it.

Biography Sources

Works Cited

"Allan Sandage - Telegraph." Telegraph.co.uk - Telegraph Online, Daily Telegraph and Sunday Telegraph - Telegraph. Web. 16 May 2011. <http://www.telegraph.co.uk/news/obituaries/science-obituaries/8150004/Allan-Sandage.html>.

"Allan Sandage, 1926-2010." Astronomy Now Online. Web. 16 May 2011. <http://www.astronomynow.com/news/n1011/16Sandage/>.

"Allan Sandage." Wikipedia. Web. 16 May 2011. <http://en.wikipedia.org/wiki/Allan_Sandage>.

Overbye, Dennis. "Allan Sandage, Astronomer, Dies at 84 - Charted Cosmos’s Age and Expansion - NYTimes.com." The New York Times - Breaking News, World News & Multimedia. 17 Nov. 2010. Web. 16 May 2011. <http://www.nytimes.com/2010/11/17/science/space/17sandage.html>.

APOD 4.4

16 April 2011 - The Tadpoles of IC 410
This false color image shows an emission nebula known eloquently as IC 410. It's so incredible how two tadpoles can randomly form out of cosmic dust and look so beautiful. A narrow band filter traces atoms and makes sulfur red, hydrogen atoms green, and oxygen blue. The cluster NGC 1983 energizes the gas of IC 410. The "tadpoles" are an enormous 10 light years in length. The trails lead away from the center, caused by cosmic "wind."

Zooniverse

I have been doing the bubble drawing experiment in Zooniverse for several weeks. It is sometimes difficult to determine where the bubbles are because they are so vaguely defined. I have found many fuzzy red objects and galaxies as well.

APOD 4.2

6 April 2011 - The Perfect Spiral
M74 is a spiral galaxy in the constellation Pisces that offers an almost perfect head-on view. It contains about 100 billion stars and is 32 million light years away. Considering that the picture is half the width of the full moon, it actually covers quite a large surface area of the sky. It's compelling to think that this majestic structure is right in front of our eyes, but we can't see it because of the long exposure times required to reveal most of the stars. M74 has multiple blue clusters and cosmic dust lanes. Some exposure in the infrared revealed a part of the hydrogen emission spectra.

APOD 4.1

1 April 2011 - It's Raining On Titan
Titan, Saturn's largest moon, has been experiencing rainstorms of methane near its equator. The rains were visible from space as a dark band around the moon. Ironically, this deluge occurred at the same time as Earth's April showers and the geographical distribution of precipitation is similar to that of Earth. Methane on Titan behaves almost like water does on Earth, with lakes evaporating to form clouds which release methane rain.

APOD 3.8

27 March 2011 - Valles Marineris: The Grand Canyon of Mars
Mars' main valley, the largest in the solar system, extends for 3000 km and is up to 600 km wide and 8 km deep. It's hard to believe it is almost a quarter of the planet's circumference! Valles Marineris is a large tectonic crack that occurred when the Martian crust was rising in the west. Over time, it was widened by erosion. Some channels have formation characteristics indicative of water or carbon dioxide. There is another theory that it was formed by subsurface magma. Regardless, it is clear that Valles Marineris is a gold mine for potential research on martian geology.

APOD 3.7

13 March 2011 - A Mars Panorama from the Phoenix Lander

The Phoenix lander was designed to study the history of water and habitability potential of Mars.This panoramic, 360 degree image combines 100 distinct photos.The probe used solar panels to maintain energy levels and dug trenches to analyze the soil. The lander descended near the North Pole to search for signs of life. The existence of subterranean ice and perchlorate salts has been confirmed. This is a very exciting time as we attempt to delve deeper into the history of Mars.

Ejnar Hertzsprung

Alex Kiefer

Mr. Percival

Astronomy

25 February 2011

Ejnar Hertzsprung

Ejnar Hertzsprung was born October 8^th 1873 in Copenhagen. His father studied astronomy but was unable to get a job, opting instead to be director of an insurance company. After high school, Ejnar studied chemistry at Copenhagen Polytechnics. From 1898 to 1901, Hertzsprung worked on acetylene-lighting in St. Petersburg. He began studying chemistry at W. Ostwald in Leipzig in 1902. Unfortunately, the death of his brother caused him to return to Copenhagen to live with his mother and sister. He worked as a private scientist, publishing his first results on stereo-photography and spectrophotometry, surprisingly having nothing to do with astronomy. After 1902, he regularly visited the University Observatory and the privately owned Urania Observatory in Copenhagen.

Karl Schwarzschild invited Hertzsprung to work in Guttingen in 1902. In 1909, he stayed at the Potsdam Astrophysical Observatory until moving to Leiden to join De-Sitter. He worked at the Leiden Observatory from 1919-1944, directing it after 1935. He retired in Denmark, although he kept working into his 90's.

Hertzsprung published “Zur Strahlung der Sterne” in “Zeitschrift für Wissenschaftliche Photographi.” in 1905. He obtained the following results: Stars in the late spectral-classes are divided into two series with different luminosity; luminous red stars must be very large; the scarcity of “red giants” shows that these stars are in a stage of fast evolution; there must be a connection between the spectrum and luminosity of stars. In 1907, he published “Zur Bestimmung der photographischen Sterngrössen,” combining photography with astronomy. He sent a preprint to Swarzschild, prompting him to propose Hertzsprung as an excellent professor.
While traveling to the US in 1910, Swarszchild met Henry Norris Russell, who had independently reached the same results as Hertzsprung. It was published as the Hertzsprung-Russell diagram in 1911. The Hertzsprung-Russell diagram plots absolute magnitude versus spectral type, and naturally reveals the main-sequence of stars, red giants and white dwarfs. In modern Hertzsprung-Russell diagrams, the rather vague measurement of spectral type has been replaced with the B-V color index, resulting in the alternate name color-magnitude diagram. Sometimes versions of the CMD with apparent magnitude on the y-axis are used in clusters where all the stars are similar distances. Another version of the H-R diagram plots the luminosity versus the effective surface temperature, useful for describing the evolution of stars.

From 1913 to 1917, Hertzsprung claimed that the color of the star is directly related to its temperature. He thought blue stars were the hottest and largest while red dwarfs were the smallest and coolest. He also theorized that stars begin as hot and gradually cool to a red dwarf, which has since been disproven.

Hertzsprung determined the distance to the Small Magellan Cloud, the first extra-galactic distance ever determined, in 1913 using the delta-Cephei type of variable stars.

Most of Hertzsprung's work was not done in the field, but desk work analyzing data from other scientists. He was the first astronomer to advocate the use of absolute magnitude. At Potsdam, he developed a technique for observing double stars, using a great refractor which eliminated errors, and improved results to ten times the accuracy of ordinary refractors. He also took a large number of exposures on one plate to achieve greater accuracy.

APOD 3.6

23 Feb 2011 The Solar System From MESSENGER
MESSENGER took several panoramic pictures of the solar system through the plane of the ecliptic from the distance of Mercury. It's pretty amazing to have all of the Sun's planets in one photo. The fact that they're all points of lights gives one an idea of how small and distant the planets are, and how much light is reflected off of them. It also solidifies Pluto's having been smacked down by the mighty fist of the planetary selection gods.

Stargaze 02/20/11

We had a stargaze for 2 hours on the service road. Through the telescope, we looked at M42, the Orion Nebula. The nebulosity was easily visible, which I found pretty amazing. We also observed M35, an open cluster in Gemini. We looked at the spectroscopic binary of Algol and everybody tried to determine where, on a clock face, the smaller star was. There were 10 first-magnitude stars visible: Aldebaren, Capella, Castor, Pollux, Procyon, Sirius, Rigel, Betelgeuse, Canopus, and Algol. At the end of the stargaze, we saw the waning gibbous moon, which had an orange tint because of refraction through the atmosphere.

Sources for Ejnar Hertzsprung

Works Cited

"Ejnar Hertzsprung." Wikipedia, the Free Encyclopedia. Web. 18 Feb. 2011. <http://en.wikipedia.org/wiki/Ejnar_Hertzsprung>.

Herrmann, D. B. Ejnar Hertzsprung :. 1981. Print.

"Hertzsprung." RUNDETAARN. Web. 18 Feb. 2011. <http://www.rundetaarn.dk/engelsk/observatorium/hertz.html>.

"The Sun: Man's Friend & Foe - Hertzsprung." Thinquest. Web. 18 Feb. 2011. <http://library.thinkquest.org/15215/History/hertzsprung.html>.

APOD 3.5

14 Feb 2011 The Rosette Nebula
The Rosette Nebula is an extremely large nebula! It covers an area 5 times the size of the full moon. The nebula looks like a long tunnel with the stars at the end, due to the stellar wind clearing out the dust in the center. The stars in the Rosette Nebula formed 4 million years ago. The red dust on the outer rim is due to hydrogen. This is located in the constellation Monoceros that we had this week.

APOD 3.4

9 February 2011
Stars Versus Mountains
NGC 2174 is an HII emission nebula in the constellation Orion. The mountainous structures in this picture comprise interstellar dust, which as we have recently studied, is a substance thinner than air containing mostly hydrogen and helium. It's pretty surprising that it covers an area of the full moon, but it wouldn't look nearly this glamorous in the nighttime sky because it's been false color-mapped. The fact that a substance so thin can produce these features in high enough quantities, gives one a sense of how vast the distances between stars are.

APOD 3.3

4 February 2011 Zeta Oph: Runaway Star

Zeta Ophiuchi is a runaway star moving about 24 km/s through interstellar space, that probably resulted from its binary partner exploding as a supernova. Its life span will be about 8 million years, and I was surprised to find that it would be one of the brightest stars in the sky if it wasn't surrounded by interstellar dust. Zeta Oph actually "pushes" the dust out of its way on its headlong journey through the cosmos, causing the infrared arc shape.

APOD 3.2

28 January 2011
When I first saw "NanoSail," I thought the sail would be a large device for collecting light samples or heating or something like that. When I read on and realize it was actually a solar wind-driven spacecraft, I was blown away! It was so amazing that the sail spontaneously unfurled itself, it's almost suspicious. The NanoSail D is more than just the plaything of a group of NASA engineers; solar sail technology could be used in the future to slow down descents of satellites and reduce space debris.

Stargaze 01/23/11

At the service road, we observed M42 through the binoculars, which was in Orion southeast of the belt. We observed Jupiter and its moons in the telescope on low power, and on high power the red stripe was easily visible. We also saw the double cluster in Casseopeia by following one of the arms of the worm asterism. Through the telescope, we saw M31, the Andromeda Galaxy, and could make out the elliptical shape. The Almaak binary star revealed differences in chromatic perception, since the bigger star was reported as both red and gold, while the smaller was blue or purple. We saw Murphak, Algol, and a cluster that resembled a butterfly in Perseus. We looked at Trapezium and, while we could easily see the 4 vertices, the 5th star was hard to discern. Finally, we saw the Eskimo Nebula in Gemini. Total time: 2 hours

APOD 3.1

January 18 2011
This picture depicts a garden in Kona, Hawaii that was designed as a microcosm of the Milky Way galaxy. At first when I saw it, I thought "that's cool that they made arms out of plants from the real galaxy," but I didn't realize they were so thorough as to grow specific leaves that represent stars. That is an incredible testament to our mastery of both astronomy and botany. I found it funny that the peaceful-looking fountain represented a violent, spaghettifying black hole.

APOD 2.6

14 December 2010
The Delta IV Heavy rocket makes liftoff in this photo, so named because it uses three boosters, and delta is the third Greek letter. After watching a video of the launch preparations, I was fascinated by how the Air Force managed to move one of the service towers on a track to get it out of the way. It just seemed amazing how something could be sturdy enough to tower hundreds of feet in the air and still be movable.

APOD 2.7

January 3 2011
The colossal, cross-constellational asterism known as the Winter Hexagon is shown here. This geometrical shape comprises the stars Capella, Aldebaran, Rigel, Sirius, Procyon, and Castor/Pollux. While this isn't as distinguishable to me as the Summer Triangle, it is impressive for such a large shape to exist naturally in the cosmos. This picture was taken in a relatively dark part of Colorado, but I think it would be even easier to recognize in a brighter area: even though the vertices would be darker, there would be fewer visible stars surrounding them.

APOD 2.8

14 January 2011
This picture shows the Quadrantid Meteor Shower, which emits over 100 meteors per hour from 2003 EH1, a radiant meteor near Polaris. The Quadrantids were named after the obsolete constellation Quadrans Muralis. Two of the meteors show up in the time exposure as crossing star trails, which I found interesting because the stars were visible for hours on end, yet the meteors lasted only seconds and still seem as bright as the star trails.

Sun Images

3D sun

Sun in infrared

Sun in radio

Sun in x-ray

William Rutter Dawes

Alex Kiefer

Mr. Percival

Astronomy

11 Jan 2011

William Dawes

        William Rutter Dawes was born March 19 1799 and died February 15 1868. He was British, born in London and raised in West Sussex. He was named after his father, who was a mathematics teacher. His father wanted him to be a clergyman in the Church of England, but Rutter Dawes opted instead to be a physician.

        Dawes’ interest in astronomy began when he met William Lassell upon moving to Liverpool in 1826. He wrote a letter to John Herschel explaining how he used a 1.6 inch refractor, Flamsteed’s Atlas and Rees’s Encyclopedia to draw diagrams of all known binary stars. In 1829, he took up astronomy as a profession after observing with Lassell. He also became a friend and apprentice of John Herschel. Dawes upgraded Herschel’s telescope to a 3.8 inch Dolland refractor which greatly improved the resolution for identifying binary stars. Dawes thus earned the nickname “eagle eye Dawes.” Dawes was elected a fellow of the Royal Astronomical Society in 1830.

        Dawes was influenced to return to religion by Rev. Thomas Waffles of the Independent Chapel on Great George Street in London. Dawes led his own congregation in Ormskirk. But when his wife died in 1839, he renounced his own congregation and joined that of George Bishop in London. Bishop’s observatory had a 7 inch refractor telescope, which Dawes used freely until 1844. He married a rich woman in 1842, and built his own personal observatory with a 6.5 inch Merz refractor. He discovered Saturn’s crepe ring along with W.C. Bond, but the latter worked at Harvard and his news didn’t cross the Atlantic before Dawes announced his discovery. Lassell attempted to observe the crepe ring with his 24 inch reflector, to no avail. However, when he visited Dawes and used the 7 inch refractor, making it out in a few minutes.

        After winning the RAS’s Gold Medal in 1855, he moved to Haddenham in 1857 and provided free medical service to its residents. His second wife died in 1860, and he observed until 1865, making drawings of Mars during its opposition in 1864. In 1867, Richard Proctor made a map of Mars based on them. He was elected a Fellow of the Royal Society, and died 4 years later.

        Dawes’s legacy consists of multiple craters on Mars and the moon and a gap in Saturn’s C ring which are named after him. Also, the Dawes limit, a formula used to calculate the resolving power of a telescope, is named after him because of its importance in observing binary stars, a focus of Dawes’s.

Works Cited

Oates, Michael. "William Rutter Dawes (1799 - 1868)." The Home of Amateur Astronomy in the UK. 30 Nov. 2009. Web. 11 Jan. 2011. <http://www.mikeoates.org/astro-history/dawes.htm>.

"William Rutter Dawes." Wikipedia, the Free Encyclopedia. 8 Sept. 2010. Web. 11 Jan. 2011. <http://en.wikipedia.org/wiki/William_Rutter_Dawes>.