History of Star in Timeline

A star is a self-gravitating, luminous plasma spheroid. The Sun is Earth's nearest star. Visible at night as fixed points of light due to their vast distances, prominent stars are grouped into constellations and asterisms, and catalogued with standardized designations. An estimated 10^22 to 10^24 stars exist in the observable universe, with only approximately 4,000 visible to the naked eye within the Milky Way galaxy.

1913: Development of the Hertzsprung-Russell Diagram

In 1913, the Hertzsprung-Russell diagram was developed, which greatly propelled the astrophysical study of stars.

1921: First Measurement of a Stellar Diameter

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 in her PhD thesis that stars are primarily made of hydrogen and helium, a groundbreaking discovery in stellar composition.

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 Defined 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 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, which are the first stars to form after the Big Bang.

2015: IAU Defined 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

In 2015, the IAU nominal constants will remain the same SI values as they remain useful measures for quoting stellar parameters.

2017: Study of Perseus Molecular Cloud

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