A rotating antenna assembly mounted on Ford Model-T wheels captured faint, persistent radio interference that redefined the boundaries of modern observational science. Constructed in Holmdel, New Jersey, this apparatus allowed Karl Guthe Jansky to identify the first extraterrestrial radio waves, shifting the focus of astronomy from purely visible light to the vast, unseen spectra of the cosmos.
Background and Early Research
Born in 1905 in Norman, Oklahoma, Jansky was raised in an environment shaped by engineering and academic rigor. His father, Cyril M. Jansky, served as a dean at the University of Oklahoma, and his brother, Cyril Jansky Jr., specialized in radio transmitter development. After earning a Bachelor of Science in physics from the University of Wisconsin–Madison in 1927, Jansky joined Bell Labs in 1928. Due to a chronic kidney condition, he was stationed at a field site in Holmdel, New Jersey, tasked with analyzing background noise that impeded trans-Atlantic voice transmissions.
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To pinpoint the source of atmospheric interference, Jansky built a directional antenna operating at 20.5 MHz. The structure, which measured 30 meters in diameter and 6 meters in height, rested on a turntable supported by Ford Model-T wheels. This configuration allowed for precise azimuthal rotation. By monitoring the device's output, he classified static into three categories: local storms, distant storms, and a mysterious, continuous hiss that persisted regardless of weather patterns.
Cosmic Discovery
The mysterious signal exhibited a daily cycle of 23 hours and 56 minutes, matching the length of a sidereal day. This confirmed that the origin was not terrestrial or solar but astronomical. In 1933, Jansky identified the center of the Milky Way, located in the constellation Sagittarius, as the primary source of this radiation. He hypothesized that this 'star noise' resulted from the thermal agitation of charged particles within interstellar gas, formally announcing his findings to the Institute of Radio Engineers later that year.
Legacy and Scientific Reception
Despite the magnitude of his discovery, the professional community was slow to embrace radio astronomy. The limitations of the Great Depression, coupled with Jansky's lack of formal astronomical training, delayed widespread integration of his methods. His research remained largely dormant until figures like Grote Reber and John D. Kraus expanded upon his initial survey. Jansky succumbed to a heart condition in 1950 in Red Bank, New Jersey, and is interred at Forest Hill Cemetery.
Fast facts
- Born: 1905, Norman, Oklahoma
- Died: 1950, Red Bank, New Jersey
- Education: University of Wisconsin–Madison
- Primary Employer: Bell Labs
- Discovery Date: September 16, 1932
- Field of Study: Radio Astronomy
- Burial Site: Forest Hill Cemetery
Questions readers ask
What caused the radio hiss discovered by Jansky?
He concluded the signals originated from the center of the Milky Way, caused by the thermal agitation of charged particles in interstellar gas.
Why was the antenna nicknamed a merry-go-round?
The large directional antenna was mounted on a turntable supported by Ford Model-T wheels, allowing it to rotate 360 degrees.
Achievements
- Affiliated with Bell Labs
- Educated at University of Wisconsin–Madison
- Worked as astronomer, physicist and inventor
