In 1960, American astronomer A.R. Sandage made a groundbreaking discovery that would change our understanding of the universe. He identified celestial bodies known as Quasars, short for Quasi Stellar Sources or Quasi Stellar Objects (QSO). Although quasars appear similar to stars in telescopic images, they are not stars. One of the key features of quasars is the red shift observed in their spectrum, which indicates their extreme distance and high velocity moving away from Earth.
Why Quasars Look Like Stars
Quasars resemble stars because their angular diameter is around one arc second, which makes them difficult to resolve with our current telescopes. Telescopes are unable to distinguish such small angular sizes, as they fall outside the resolution range of most instruments. The angular diameter of actual stars is even smaller, which is why stars also appear as mere points of light through our telescopes.
The Initial Observation of Quasars: A Mysterious Radio Source
The discovery of quasars was not only a visual observation but also a result of detecting strong radio waves from a specific part of the sky. In 1960, astronomers observed a powerful radio signal and, upon further investigation, realized it wasn’t coming from stars or any known celestial bodies. This led to the identification of quasars, marking the beginning of a new era in astronomy.
Discovery of Quasar 3C 272
In 1962, a major milestone in quasar research was reached with the discovery of quasar 3C 272. It was detected by a radio telescope in Australia, with a red shift of about 0.158, significantly higher than the typical red shift observed in nebulae. This confirmed the existence of quasars and their unusual properties beyond any doubt, giving scientists a new area to explore in the universe.
Quasars: Unique Characteristics and Mysteries
Quasars differ significantly from stars, despite their similar appearance in images. One of the most noticeable differences is their color. Quasars are bluer than stars but not as blue as some other celestial objects. This characteristic has helped astronomers differentiate between stars and quasars, leading to the realization that many blue-looking objects are actually quasars. By 1995, scientists had discovered around 1,000 quasars, but their true nature and distance from Earth remain unsolved mysteries.
The Structure of a Quasar
Quasars possess a massive nucleus, which is slightly smaller than one light year in size. Surrounding this nucleus are excited gases, which glow due to radiation emanating from the central region. These gases produce a broad spectrum of radiation, with some quasars emitting frequencies between 30 MHz and 100 MHz. Scientists believe that the energy emitted from quasars is gravitational rather than nuclear, making them one of the most energetic objects in the universe. A quasar’s lifespan is estimated to be around 10 years, during which time they emit roughly 10% of their erg energy.
Theories on the Origin and Distance of Quasars
Despite extensive research, the exact distance of quasars from Earth has yet to be determined. Their characteristics, similar to those of nebulae, suggest that quasars could be active centers of nebulae. Some studies propose that around 10 million years ago, the number of quasars in the universe was much higher, which coincides with the period when nebulae were being formed. This raises the possibility that quasars played a role in the birth of nebulae, further deepening the mystery surrounding these enigmatic celestial bodies.
Quasars and Their Cosmic Significance
The discovery of quasars has revolutionized our understanding of the universe. Although much is still unknown about them, their unique characteristics, immense energy, and potential connection to nebulae formation continue to intrigue scientists. As technology advances, astronomers are hopeful that the mysteries surrounding quasars will eventually be unraveled, providing further insight into the origins and evolution of the universe.
