History of Star in Timeline

A star is a self-gravitating, luminous plasma spheroid, exemplified by the Sun. While many stars are visible as fixed points of light from Earth, their vast distances necessitate categorization into constellations and asterisms, with brighter stars receiving proper names. Astronomers maintain star catalogues, providing standardized designations for known stars. The observable universe contains an estimated 10^22 to 10^24 stars. However, only about 4,000 are visible to the naked eye from Earth, all residing within the Milky Way galaxy.

1913: Development of the Hertzsprung–Russell diagram

In 1913, the Hertzsprung–Russell diagram was developed, propelling the astrophysical study of stars.

1921: First stellar diameter measurements

In 1921, Albert A. Michelson made the first measurements of a stellar diameter using an interferometer on the Hooker telescope at Mount Wilson Observatory.

1925: Cecilia Payne-Gaposchkin proposes stars are primarily hydrogen and helium

In 1925, Cecilia Payne-Gaposchkin proposed that stars were made primarily of hydrogen and helium in her PhD thesis.

2005: Lowest iron content star measured

As of 2005 the star with the lowest iron content ever measured is the dwarf HE1327-2326, with only 1/200,000th the iron content of the Sun.

2012: IAU defines astronomical constant

In 2012, the IAU defined the astronomical constant to be an exact length in meters: 149,597,870,700 m.

2014: CODATA estimate of the Newtonian constant of gravitation G

In 2014, the most recent CODATA estimate of the Newtonian constant of gravitation G was used to derive the solar mass.

June 2015: Evidence for Population III stars reported

In June 2015, astronomers reported evidence for Population III stars in the Cosmos Redshift 7 galaxy at z = 6.60.

2015: IAU defines nominal solar values

In 2015, the IAU defined a set of nominal solar values (defined as SI constants, without uncertainties) which can be used for quoting stellar parameters.

2015: IAU nominal constants for stellar parameters

The 2015 IAU nominal constants will remain the same SI values as they remain useful measures for quoting stellar parameters, despite possible future observational uncertainties in values for luminosity, radius, mass parameter and mass.

2017: Study of Perseus molecular cloud

In a 2017 study of the Perseus molecular cloud, astronomers found that most of the newly formed stars are in binary systems, and proposed that all stars initially formed as binaries.