Vera+Rubin

= ﻿Vera Rubin = toc 1928 to Present By: Linnea Gies

 From a very early age the stars captivated Vera Cooper Rubin, who built her first telescope out of a cardboard tube at age ten (1). As a woman, the study of science was discouraged, yet when she received a scholarship from Vassar she ended up graduating “ as the only astronomy major in 1948” (2). Vera Rubin then studied physics at Cornell and from there went on to Georgetown University, where she earned her Ph.D. in 1954 (2). Rubin eventually took a research position at the Carnegie Institution in Washington, D.C., where she worked with Kent Ford, “an astronomer who had developed an extremely sensitive spectrometer” (2). It was in the 1970’s working along side Kent Ford at the Carnegie Institution in Washington that Rubin discovered and provided substantial evidence for the mystery that is dark matter.

What came first?
 Prior to Vera Rubin’s discovery of dark matter, Newton’s law of gravity defined the universe. Take our solar system, for instance: the Sun serves as the force of gravity, holding all of the planets in our system orbiting in their plain. The closer the planet is to the source of gravity (the Sun) the higher its velocity is because it has more force on a planet the closer it is. Therefore, the planets farther away, like Uranus and Neptune orbit at a lower velocity (the orbit slower). Scientists believed that this applied to spiral galaxies as well: the stars held in orbit by a black hole at the center, with the stars in the outer rings orbiting at a slower pace.

Vera Rubin's Scientific Breakthrough
At the Carnegie Institution Vera Rubin studied the dynamics of galaxies. She specifically chose to study the outside of galaxies because no one else had done it or was doing it (6). Lucky for her, she ended up being the one to find that the previously held notions concerning the rotation of spiral galaxies did not hold true. While studying the rotation curves in the Andromeda galaxy, Rubin discovered that the stars in the outside of the galaxy did not slow down as expected. A rotation curve "plots the rotational velocity of stars or gas clouds against their distance from the center of the galaxy...[and] summarizes the results of these orbital velocity measurements" (3). The rotation curve should have had a large dip as the distances got larger, however, the line became flat, showing that the orbital velocities stayed at a constant beyond “the inner few thousand light years” (3). It appeared that stars were held in space by some extra force of gravity, spinning at a velocity as fast at the one’s close to the black hole. According to Newton’s laws of motions, the stars should be flung out into space, since it is impossible that the gravity of the black hole has such a strong hold on the stars. But whether or not it made sense, something was holding the stars in their high velocity orbit. Rubin said that “there has to be a lot of mass to make the stars orbit so rapidly, but we can’t see it. We call this invisible mass dark matter” (1).

Below is a clearer view of what Rubin's rotation curve would have looked like:

Rubin got the term “dark matter” from something she learned in school about an astronomer named Fritz Zwicky (2). Zwicky made the first proclamation about dark matter in clusters of galaxies in the 1930’s (4). Unfortunately, he did not have enough evidence to give his hypothesis any ground, resulting in “most of his colleagues consider[ing] him an eccentric who leapt to premature conclusions” (4). Luckily, 30 years later Rubin could find that evidence to make his observation a lot more reasonable.

 Vera Rubin’s discovery was made possible by the help of Kent Ford and his spectrometer. To receive the results of Rubin’s studies, Rubin and Ford used the highly sensitive spectrometer to study the Doppler shifts across the disks of many galaxies (2). Like planets orbiting the sun, stars orbit a black hole along a plain that appears as a disk. When a star (a source of light) move towards us there is a decrease in wavelengths, which is a shift towards the blue end of the spectrum, and when the star moves away from us there is an increase in wavelengths, a red shift. This is the Doppler effect. Rubin and Ford measured these red and blue shifts of light from the stars moving towards and away from us, which allowed them to “calculate the orbital speeds of the stars in different parts of those galaxies” and therefore enabled Rubin to create a rotation curve for the bizarre behavior of the Andromeda galaxy (2).



What is Dark Matter?
We have known that gravity is what holds the universe together for a long time. However, we previously thought it was the gravity of the stars that held it all together, what Rubin proved to be wrong. And although we now know there is something holding everything together, we cannot explain what exactly it is. “At least ninety percent of the mass in galaxies, and therefore in the observable universe, is invisible and unidentified,” meaning that from what Vera Rubin found, galaxies need to contain at least ten times the amount of mass they already have in order for the stars to remain in their places at the outer rings of the galaxy (2). The problem was (and still is) that this extreme amount of mass is invisible to us. Professor Saul Perlmuter of the University of California- Berkeley explained that what we know about dark matter: it has mass (attracts gravity), and that that mass is extremely massive (7) He explained that the amount of mass we have found in things we can see, “the ordinary stuff,” is less than a fifth of what is needed to hold everything together (7). Dark matter is, simply put, “a name we give to whatever unseen influence is causing the observed gravitation effects” (5).

Vera Rubin's Impact on Science
Vera Rubin provided the evidence necessary to bring the hypotheses about dark matter to the forefront of science, even to the general public. Prior to her observations only a select few knew of the speculations about the dark matter out in the universe. After 1975 when she and Ford announced their findings everyone knew and almost everyone now accepts the notion of dark matter (8). Although they made their announcement in 1975 about they had found, there were still many critics. Rubin and Ford “constructed rotation curves for the hydrogen gas in many other spiral galaxies…and discovered that flat rotation curves are common” (4). Rubin and Ford, as well as other astronomers, kept measuring rotation curves of galaxies until there was enough evidence that by the 1980’s the critics could no longer deny the existence of //something// like dark matter (4). Today astronomers continue making strides towards understanding dark matter and finding out exactly what it is.

Rubin as a Woman Pioneer, Her Achievements, and Her Work Today
Although, Rubin is best known for her evidence on dark matter, she has been an advocate for women in astronomy since college, when she was denied admittance to Princeton because “Princeton does not accept women” (2). She is considered a “woman pioneer” after fighting “through severe criticisms of her work to eventually be elected to the National Academy of Sciences (at the time, only three women astronomers were members) and to win the highest American award in science, the National Medal of Science” (9). Today Rubin continues to study galaxies and is still making new discoveries about them. She continues to find irregularities about the dynamics of galaxies. For instance, she recently discovered a disk galaxy (NGC 4550) “in the Virgo cluster in which half the stars go clockwise and half the stars go counterclockwise—intermingled in the same disk” (1).

Rubin’s work with spiral galaxies not only enlightens us to what our own solar system is and can be doing, but it opens our eyes to the possibilities of things in our universe that go completely against the norm. The possibility of bizarre, unexplained behavior makes the impossibilities of our universe seem possible. Vera Rubin shed light on the fact that there is room for endless discoveries in our universe: “In a very real sense, astronomy begins anew. The joy and fun of understanding the universe we bequeath to our grandchildren--and to their grandchildren. With over 90% of the matter in the universe still to play with, even the sky will not be the limit” (10).

 Below is a video about Vera Rubin and Dark Matter. media type="youtube" key="E_sJ_erk9KY" height="383" width="640"

Sources:
 * 1) "Astronomer Vera Rubin—The Doyenne of Dark Matter." //DISCOVER Magazine: Science and Technology News, Science Articles//. 1 June 2002. 18 July 2010. .
 * 2) Soter, Steven, and Neil DeGrasse Tyson. “Vera Rubin and Dark Matter.” //Cosmic Horizons: Astronomy at the Cutting Edge//. New York: New, 2001. .
 * 3) Bennett, Jeffrey O. //The Cosmic Perspective.// San Francisco: Pearson Addison-Wesley, 2010. 651.
 * 4) Bennett, Jeffrey O. //The Cosmic Perspective.// San Francisco: Pearson Addison-Wesley, 2010. 654.
 * 5) Bennett, Jeffrey O. //The Cosmic Perspective.// San Francisco: Pearson Addison-Wesley, 2010. 650.
 * 6) “The Mystery of Dark Matter.” //YouTube//. 09 Mar. 2010. Web. 18 July 2010. . 2:01.
 * 7) “The Mystery of Dark Matter.” //YouTube//. 09 Mar. 2010. Web. 18 July 2010. . 5:26.
 * 8) “The Mystery of Dark Matter.” //YouTube//. 09 Mar. 2010. Web. 18 July 2010. <http://www.youtube.com/watch?v=E_sJ_erk9KY>. 5:00.
 * 9) <span style="font-family: Arial,Helvetica,sans-serif; font-size: 10pt;">"Vera Cooper Rubin: Shedding Light on Dark Matter." //Vassar Innovators//. Dec. 1997. Web. 18 July 2010. <http://innovators.vassar.edu/innovator.html?id=68>.
 * 10) <span style="font-family: Arial,Helvetica,sans-serif; font-size: 10pt;">Thompson, Katrina. "Vera Rubin's Dark Universe." //Lake Afton Public Observatory//. Web. 23 July 2010. <http://www.webs.wichita.edu/lapo/vr.htm>.

Picture and Video Sources (in order of appearance):
 * 1) Archives and Special Collections. Vera Cooper Rubin. //Innovators//. Vassar, Dec. 1997. Web. 18 July 2010. <http://innovators.vassar.edu/innovator.html?id=68>.
 * 2) //Cosmic Variance | Discover Magazine//. Photograph. //Discover Blogs//. Discover Magazine, 30 Aug. 2005. 20 July 2010. <http://blogs.discovermagazine.com/cosmicvariance/2005/08/>.
 * 3) "Chapter 13: Some Answers to the Missing Mass Problem." //Reinventing the Universe//. Web. 23 July 2010. <http://deceptiveuniverse.com/Chapter13.htm>.
 * 4) "NGC 4414." //Space Wallpaper//. 25 July 2010. <http://www.spacewallpapers.net/spacewallpapers.html>.
 * 5) Clifford. "Dark Matter in 3D." //Asymptotia//. 7 Jan. 2007. Web. 23 July 2010. <http://asymptotia.com/2007/01/07/dark-matter-in-3d/>.
 * 6) // Clifford. "Simulation of Dark Matter." //Asymptotia//. 8 Jan. 2007. 23 July 2010. <http://asymptotia.com/2007/01/07/dark-matter-in-3d/>.//
 * 7) Siegal, Ethan. "The Last 100 Years: 1929, Hubble, and a Vast Universe : Starts With A Bang." //ScienceBlogs//. 12 June 2009. Web. 23 July 2010. <http://scienceblogs.com/startswithabang/2009/06/the_last_100_years_1929_hubble.php>.
 * 8) //Vera Rubin Measuring Spectra//. Photograph. //American Museum of Natural History//. By Vera Rubin. 2000. Web. 23 July 2010. <http://www.amnh.org/education/resources/rfl/web/essaybooks/cosmic/p_rubin.html>.
 * 9) "The Mystery of Dark Matter.” //YouTube//. 09 Mar. 2010. Web. 18 July 2010. <http://www.youtube.com/watch?v=E_sJ_erk9KY>.

External Links:
 * 1) Stephen Hawking: WikiSpace
 * 2) [|Rubin and Dark Matter]
 * 3) [|NASA Dark Matter: Image of the Day]
 * 4) [|"A Dim Light Shines on Dark Matter"]
 * 5) [|"Shedding Light on Dark Matter"]
 * 6) [|Deceptive Universe: Some Answers to the Missing Mass Problem] This is a very interesting website, giving an "alternative" to dark matter (more than that denying that it exists altogether).