History of Star in Timeline

Stars are luminous spheres of plasma bound by their own gravity. The Sun is the closest star to Earth. Visible at night as fixed points of light due to their distance, prominent stars are grouped into constellations and have proper names. Astronomers catalogue stars, providing standardized designations. The observable universe contains an estimated 10^22 to 10^24 stars, but only about 4,000 are visible to the naked eye, all 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: Stars primarily made of 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 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 the 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 CODATA estimate of the Newtonian constant of gravitation G was used to derive the solar mass to be approximately 1.9885×10 kg.

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.