Arno Penzias

Arno Penzias

Physicist
Date of Birth: 26.04.1933
Country: Germany

Biography of Arno Allan Penzias

Arno Allan Penzias, an American astrophysicist, was born in Munich, Germany, to Karl Penzias, a Polish citizen involved in the leather trade, and his wife Inge (nee Eisenreich) Penzias. Coming from a Jewish family, they managed to leave Germany just before World War II. In the spring of 1939, Arno and his younger brother were sent to England, followed shortly by their father, and a few months later, their mother, at the beginning of the war. After reuniting, the family left England in December 1939 and arrived in New York in early 1940. Arno's father worked on a construction site in the Bronx for a while, and then got a job at the carpentry workshop of the Metropolitan Museum. To supplement the family income, Arno's mother, who took the name Justine, found work at a sewing studio. In 1947, Arno enrolled in Brooklyn Technical High School, where, despite his interest in electronics, he focused on studying chemistry. Four years later, he continued his education at the tuition-free City College in New York City. In his first year, Arno dedicated himself entirely to physics, as his teacher convinced him that this field would provide a means of earning a living. In 1954, Arno graduated from college, ranking among the top graduates. After completing a Reserve Officers' Training Corps program in college, Arno served two years in the Signal Corps at Fort Devens, Massachusetts. In late 1956, he entered the graduate program at Columbia University, where he was taught by I.A. Rabi, Polykarp Kusch, Lee Tsung-Dao, and Charles X. Townes. Two years prior to this, Townes had created the first maser - a device that emits and amplifies high-frequency radio waves. Under Townes' guidance, Arno built a second maser, which was used as an amplifier in a microwave receiver, becoming part of his doctoral dissertation defended at Columbia University. Arno believed that the maser, designed to emit radio waves at a wavelength of 21 cm, could help determine the hydrogen content in a number of galaxies. Arno connected the maser to the antenna at the Marine Research Laboratory in Maryland Point, Maryland, but the resulting spectrum did not contain any hydrogen lines. Later, Arno concluded that "the equipment was more accurate than the observations." Unsatisfied with the results, Arno turned to the director of the radio research laboratory at Bell Telephone Company in Crawford Hill, New Jersey, Rudolf Kompfner, seeking permission to repeat the experiment. He intended to use a 20-foot antenna with a horn reflector installed in Holmdel, New Jersey, to receive signals from the unguided satellite Echo, whose launch was expected in 1960. Instead, Kompfner offered Arno a full-time job, which he accepted in 1961. A year later, he obtained his doctorate from Columbia University.
Discovery of Cosmic Microwave Background Radiation

Arno's first work in the Bell Labs was focused on finding a way to increase the accuracy of the antenna located in Andover, Maine, which was used to receive signals from the communication satellite Telstar. Due to various factors, including gravitational and weather conditions, the steel antenna could bend. Arno quickly solved the problem by placing a second receiver inside the antenna, aimed at a known source of radiation, such as the remains of a supernova. Having the opportunity to continue working on satellite communication with a horn antenna, Arno preferred fundamental research in radio astronomy, hoping to detect the hydroxyl molecule (containing one hydrogen atom and one oxygen atom) in interstellar space. However, although Arno achieved positive results in this project, he was preceded by a research group from the Massachusetts Institute of Technology, who were the first to detect this cosmic molecule.
In 1963, working with Robert W. Wilson, Arno began adapting the horn antenna for use in radio astronomy. The precise tuning and ultra-high sensitivity of its amplifier allowed scientists to measure the intensity of several extraterrestrial radio sources. Moreover, they were able to filter out radio interference caused by local sources, such as the Earth's surface, atmosphere, and the antenna itself. This made it possible to measure the intensity of the background radiation from any area of the sky near an interesting source. In 1964, scientists used their system to measure the radio signals from Cassiopeia A, an object that is the remnant of a supernova and the most powerful radio source in the constellation Cassiopeia. However, the results of measuring the background puzzled the researchers, as the interference was so strong that it could not be attributed to any known sources. The anomalies persisted in repeat measurements. Arno and Wilson inspected the entire system in search of the source of interference, closing riveted connections and cleaning the antenna from bird droppings, but it had no significant impact on the measurement results.
Radio waves, like any electromagnetic radiation, are usually characterized by wavelength or frequency. However, one of the characteristics can also be temperature, as all objects emit wavelengths determined by their temperature, and the higher the temperature, the shorter the wavelength. While cold objects also emit, the characteristic wavelength is so large that it is not visible to the human eye. The eye sees cold objects thanks to reflected light, but in darkness, where there are no light sources, cold objects are invisible. The background radiation, or radio interference, observed by Arno and Wilson, had wavelengths so large that they were significantly below the threshold of visibility. It corresponded to the wavelength emitted by a black body at a temperature of 3.5° Kelvin, which only slightly exceeds absolute zero - the temperature at which all thermal motion ceases. While Arno and Wilson were studying the unexpected background radio emissions, a theoretical group at Princeton University, led by Robert Dicke, was developing a cosmological model of an expanding and contracting Universe. If the Universe originated, as George Gamow suggested, as a result of the so-called "Big Bang," then according to Dicke, radiation from it could be observed even after 18 billion years of cooling. Dicke's colleague, P.J.E. Peebles, estimated the present background radiation to be 10°K (later reduced to 3.5°K) and spoke about it in a lecture at the Johns Hopkins University.
Among the scientists who attended Peebles' lecture was Bernard F. Burke, a radio astronomer from the Massachusetts Institute of Technology. During a phone conversation with Burke in 1965, Arno mentioned the unexplained interference that he and Wilson had to observe. Learning from Burke about Peebles' work, Arno contacted not only him but also Dicke and his colleagues at Princeton, who were building an antenna to measure the predicted cosmic background radiation. As a result of this meeting, two articles were published simultaneously, one by the Princeton group on the cosmological theory and the other by Arno and Wilson on the measurements of the background radiation. The observations continued for several years, and the radiation corresponded to the wavelength distribution predicted by the "Big Bang" cosmology. (Gamow and his collaborators made similar predictions in 1948, but leading radio astronomers of that time did not consider it possible to experimentally verify them with modern instruments.)
Arno and Wilson then undertook a new study of the carbon laser (an amplifier that produces an intense monochromatic beam of light), hoping to use it to transmit communication signals through the Earth's atmosphere. However, the study ended in failure. In the late 1960s, they returned to radio astronomy. In collaboration with physicist-atomic scientist Keith Jefferts from Bell Laboratories, they built a receiver capable of detecting radiation with a wavelength of about a millimeter. In 1970, they attached their receiver to the newly constructed 36-foot radio telescope at the National Radio Astronomy Observatory in Kitt Peak, Arizona. Aiming it at the Orion Nebula, the scientists saw a spectral line (characteristic emission wavelength) of carbon monoxide on the display. Subsequent research revealed six more interstellar molecules. Arno continues to work on astrophysics, primarily focusing on the origin of chemical elements.
In 1978, Arno and Wilson were awarded half of the Nobel Prize in Physics "for the discovery of cosmic microwave background radiation." The other half of the prize was awarded to Pyotr Kapitsa. Presenting the laureates, member of the Royal Swedish Academy of Sciences, Lennart Hultén, noted "their exceptional persistence and craftsmanship, which led (Arno and Wilson) to a discovery that allowed for the introduction of experimental methods and direct observation into a field like cosmology."
Recognizing Arno's outstanding organizational abilities, Bell Laboratories entrusted him with several management positions: head of the Radio Physics Research Division at Crawford Hill (1972), director of the Radio Research Laboratory (1976), and vice president of Research (1981). Since 1972, Arno has also been a member of the scientific council of the Department of Astrophysical Sciences at Princeton University.
Arno became a naturalized U.S. citizen in 1946 and adopted the name Allan, by which he has been known since arriving in America. He married Anne Pearl Barres, a legal consultant, in 1954. The newlyweds settled in Highland Park, New Jersey, and had a son and two daughters.
A member of the National Academy of Sciences, American Academy of Arts and Sciences, and the American Astronomical Society, Arno also served on the Board of Trustees of Trenton College and the Astronomical Advisory Committee of the National Science Foundation. Among the awards he has received are the Henry Draper Medal of the National Academy of Sciences (1977) and the Herschel Medal of the Royal Astronomical Society (1977). He has been awarded an honorary doctorate from the Paris Observatory.

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