Today’s Google Doodle celebrates Dilhan Eryurt, a Turkish astrophysicist who played a huge role in the way we understand how the Sun was formed.
But who was she, what were some of her notable achievements, and why has Google chosen today to honour her?
Here’s everything you need to know.
Scientist, scholar of high mathematics and astronomy. She was born on the 29th of November 1926 in Izmir. She was interested in mathematics starting from early ages. After graduating from Ankara Girls High School she chose Istanbul University High Mathematics and Astronomy Department for her undergraduate education. Eryurt’s interest in astronomy appeared during her university years. She received her first scientific fundaments there, including from foreign professors. Upon graduation, also under the influence of her new enthusiasm of astronomy she became an assistant of Prof. Dr. Tevfik Okyar Kabakçıoğlu who was responsible for opening a department of astronomy in Ankara University. However, since there was no empty position, she continued working for two years without any payment. She wrote her PhD in Astrophysics again in Ankara University (1953). Her research fields are astrophysics, structure and developments of stars, sun models and neutrino problem.
As Dilhan Eryurt went to USA after long years, she received the scholarship of National Academy of Sciences and started to work in Goddard Space Research Institute of NASA at New York. She became an associate professor under the supervision of Prof. Dr. A. E. Kreirken at Ankara University, Department of Astrophysics. In 1959 she went to Canada for two years, using the scholarship given to her by the International Agency of Atom Energy. There she met real astrophysics. Prof. Dr. Cameron suggested her three topics to make researches on and she chose hydrogen stars. Later, since it was first necessary to calculate the opposite of a gas, which consisted of hydrogen, she produced the computer software she was asked for. The first thing she learnt with this work, which would later be published, was the “fitting” method… Eryurt after her researches in Canada started to work in Indiana University with a scholarship she received from USA. She worked with Prof. Dr. M. Wrubel who was known with making star models in Indiana.
Prof. Eryurt, as she also stated before, passed to NASA after Indiana. Working together with Dr. Cameron who came there earlier, they analyzed all evolutions of low massed and high massed stars. So that a giant dust and gas cloud in the space can transform into a star, the nuclear heat in it must be increased and nuclear energy can come into being. First phases of the star, phases of collapse make it possible that the heat in the center is increased and the required heat is obtained. For that, the mass of the star must reach a certain size so that it can provide the necessary heat. If mass of the star cannot create this heat by collapsing, nuclear reaction cannot begin. The problem in which Eryurt especially was interested here was “What is the limit of low masses or what is the limit of mass for small stars?” and she worked on this problem. The first study of Eryurt on that issue was about stars which only consisted of hydrogen.
Dilhan Eryurt states the meaning of this knowledge in the evolution of a star as the necessary conditions for the formation of a star. During her researches in which she used the method of “Fitting” Prof. Eryurt advanced by adding new options to the program continuously. Thus, she developed the method of fitting and as a result produced a new program. This was the most perfect program of that period, but later her students developed this program by adding whirling to it.
Prof. Eryurt made researches on the evolution of the sun together with Prof. Cameron. Since the sun evolution model, which was valid at that time, was criticized, it was necessary to produce a new model, which included the latest theories. It was also decided to analyze heat, intensity, radiation and the interaction between sun and planets with the new model. It was accepted within the previous theory that the sun was colder in its first formation and slowly reached its status of today. It was believed that the sun was less bright during the period of four billion years after its constitution and then slowly started to shine, thus reached its brightness of today.
The most important aspect of Eryurt’s study on this issue is that it was realized that the sun was much brighter than now during its first constitution, its heat slowly decreased and later reached its state of today. If it is necessary to explain shortly the special content of this mechanism; the sun’s first bright then decreasing state depends on the burning of hydrogen in it. After reactions of hydrogen started the superficial heat slowly increases. As it is known the sun has burnt half of its hydrogen until today and reached its state of today. In other words, this means a decrease, which means there are 4.5 billions of years until the consumption of sun. This new model, which is still valid is a discovery of Dilhan Eryurt to a large extent. Thus Prof. Eryurt has contributed to the knowledge about the constitution of the sun. The importance of this study is: If the earth came into being during the brightest period of the sun, the elements which constituted this planet were exposed to thousands of degrees heat for tens of thousands of years, which is a great and direct impact to the physical and chemical properties of the earth. Naturally a similar impact comes into question for our satellite, moon. This impact of high heat was important for the Apollo Moon Trip Project designed to be realized in 1960s because of the environment the astronauts would meet who would take this trip. Eryurt was also interested in the issue of “neutrinos” aside from her works in NASA institute about the constitution of stars and evolution of sun.
Dr. Dilhan Eryurt is completely a “wonder-woman”. Because the word “evolution” can annoy even people of today, let alone people 50 years ago. This is also possible to observe in magazine articles, which explain her… Eryurt calls her achievement as “evolution of stars” but journalists and authors continuously use the word “history of stars”. Eryurt during her stay in USA came to Turkey for several times. Her purpose was to transfer her knowledge and experience to Turkey and raise students. But she learnt that this task was more difficult than the evolution of stars. First she worked as a guest professor in Middle Eastern Technical University in 1968 for one year. Aside from her courses she also organized scientific gatherings. As she organized the 1st National Astronomy Assembly only 25 people joined it. There was an association of astronomy earlier in Turkey but that association organized touristic trips instead of scientific gatherings. However, she witnessed that associations in USA always organized scientific gatherings. During gatherings she joined there she told about her scientific studies and attracted a very considerable attention. In Turkey on the other hand, let alone gatherings, it was even difficult to give a lecture on astrophysics, because there was nobody to listen to it…
Prof. Dr. Dilhan Eryurt returned to METU Department of Physics in 1973 with a firm position and established here the Department of Astrophysics. In 1988 she first served as the Head of Physics Department in the Faculty of Science-Literature in METU, later Dean of the same faculty for five years. She retired in 1993… Prof. Dr. Dilhan Eryurt received the Apollo Achievement Award in 1969, which was given by NASA. Later she worked in institutes which were responsible of developing the first unmanned space vehicles to be orbited around the earth. Another achievement award she received was TÜBİTAK’s “Service to Science and Encouragement” in 1977…
Many articles of her were published in professional magazines of USA, Canada and other countries under her name or as a joint author… She is an honorary member of national and international professional associations such as International Astronomical Union, American Astronomical Society and Turkish Astronomical Society and Turkish Academy of Sciences. Bilim ve Teknik Magazine prepared a special section for her in its November 1997 issue.
REFERENCE: Alper Akoğlu / Astrofizikte Öncü Bir Bilim Kadını – Prof Dr. Zeki Aslan / Yıldızların Evrimi ile Kırk Yıl – Prof. Dr. Nilgün Kızıloğlu / Çalışmayı Seven Bir Bilim Kadını – Prof. Dr. Halil Kırbıyık / Alçak Gönüllü Bir Bilim Kadını (Bilim ve Teknik, Kasın 1997), İhsan Işık / Ünlü Bilim Adamları (Türkiye Ünlüleri Ansiklopedisi, C. 2, 2013) – Encyclopedia of Turkey’s Famous People (2013).