Chapter 14: Problem 13

When quasi-stellar radio sources were first discovered and named, why were they called "quasi-stellar"?

Short Answer

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Answer: Quasars exhibit enormous energy emissions, including radio waves and visible light, which are billions of times more luminous than a typical star. They also have large redshifts, indicating that they are moving away from Earth at incredibly high speeds, and are found at great distances, making them some of the most distant objects in the universe. While they appeared star-like in their initial observations, it was later discovered that quasars are actually powered by supermassive black holes at the centers of galaxies. These unique characteristics led to the adoption of the name "quasi-stellar", meaning "almost star-like".

Step by step solution

Definition of "quasi-stellar"

"Quasi" means "resembling" or "almost", and "stellar" refers to stars. Together, the term "quasi-stellar" means "resembling a star" or "almost star-like".

First observation of quasars

Quasars, which stand for "quasi-stellar radio sources", were first discovered in the 1960s. At that time, astronomers detected strong radio waves coming from a celestial object that appeared star-like but couldn't be classified as a typical star due to its unique characteristics.

Characteristics of quasars

Quasars are characterized by enormous energy emissions, including radio waves and visible light. These emissions are billions of times more luminous than a typical star. Additionally, quasars are found at incredible distances from Earth, meaning they are some of the most distant objects in the universe. They emit redshifted light, indicating that they are moving away from Earth at incredibly high speeds.

Real nature of quasars

While quasars initially appeared to be star-like, further studies revealed that they are actually powered by supermassive black holes at the centers of galaxies. These black holes have mass millions or billions of times greater than the Sun, and as they consume surrounding gas and dust, they emit a huge amount of energy in the form of radiation, including radio waves.

The reason for the name "quasi-stellar"

The name "quasi-stellar radio source" or "quasar" was chosen because these objects appeared star-like in their initial observations, but had unique radio emissions that distinguished them from typical stars. The word "quasi" implies that these objects are almost, but not quite, stars.

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When quasi-stellar radio sources were first discovered and named, why were they called "quasi-stellar"?

Short Answer

Step by step solution

Definition of "quasi-stellar"

First observation of quasars

Characteristics of quasars

Real nature of quasars

The reason for the name "quasi-stellar"

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