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Life of a Star

When these happened

21 dated records from 1 BCE to 2027. Each is drawn as wide as its date is certain — a band is a band because nobody knows the year, not because the drawing is imprecise.

0500100015002000The Sun forms and settles onto the main sequence — ~4.6 billion years agoThe first stars form from metal-free gas — ~13.6 billion years agoA guest star appears in Taurus and is recorded in East Asia — 1054 (first sighting commonly given as 4 July; contested)Alvan Graham Clark sees Sirius B — 1862-01-31Hertzsprung and Russell independently plot luminosity against temperature — 1911-1913Payne concludes that stars are mostly hydrogen - and disclaims it — 1925A maximum mass for ideal white dwarfs is published — 1931Baade and Zwicky propose supernovae and neutron stars — 1934B2FH sets out the synthesis of the elements in stars — 1957A regularly pulsing radio source is identified — 1967-11-28A pulsar is found inside the Crab Nebula — 1968SN 1987A: neutrinos from a collapsing core reach Earth — 1987-02-23 ~07:35 UT (neutrinos); optical discovery 1987-02-24Hubble photographs the Pillars of Creation — 1995A neutron-star merger is detected in gravitational waves and light — 2017-08-17Betelgeuse fades by more than a magnitude — 2019-10 to 2020-03Neutrinos from the solar CNO cycle are detected — 2020A radius is measured for the heaviest known neutron star — 2021JWST finds the compact object in SN 1987A — 2024-02-22Gaia stops observing — 2025-01-15A close companion to Betelgeuse is probably detected — 2025-07 (reported; detection observation December 2024)Gaia Data Release 4 scheduled — 2026-12 (planned)
21 shown · 21 dated · 0 cannot be placed on an axis · Approximate or contested. Draw a band and do not sharpen its edges.
In order21
  1. ~4.6 billion years agoThe Sun forms and settles onto the main sequence

    It happened, and the record is settled.

  2. ~13.6 billion years agoThe first stars form from metal-free gas

    Sources disagree, or the dating is contested. Stated, not resolved.

  3. 1054 (first sighting commonly given as 4 July; contested)A guest star appears in Taurus and is recorded in East Asiasources disagree about the date

    Sources disagree, or the dating is contested. Stated, not resolved.

  4. 1862-01-31Alvan Graham Clark sees Sirius B

    It happened, and the record is settled.

  5. 1911-1913Hertzsprung and Russell independently plot luminosity against temperature

    It happened, and the record is settled.

  6. 1925Payne concludes that stars are mostly hydrogen - and disclaims it

    It happened, and the record is settled.

  7. 1931A maximum mass for ideal white dwarfs is published

    It happened, and the record is settled.

  8. 1934Baade and Zwicky propose supernovae and neutron stars

    It happened, and the record is settled.

  9. 1957B2FH sets out the synthesis of the elements in stars

    It happened, and the record is settled.

  10. 1967-11-28A regularly pulsing radio source is identified

    It happened, and the record is settled.

  11. 1968A pulsar is found inside the Crab Nebula

    It happened, and the record is settled.

  12. 1987-02-23 ~07:35 UT (neutrinos); optical discovery 1987-02-24SN 1987A: neutrinos from a collapsing core reach Earth

    It was measured or witnessed, with the observation cited.

  13. 1995Hubble photographs the Pillars of Creation

    It was measured or witnessed, with the observation cited.

  14. 2017-08-17A neutron-star merger is detected in gravitational waves and light

    It was measured or witnessed, with the observation cited.

  15. 2019-10 to 2020-03Betelgeuse fades by more than a magnitude

    It was measured or witnessed, with the observation cited.

  16. 2020Neutrinos from the solar CNO cycle are detected

    It was measured or witnessed, with the observation cited.

  17. 2021A radius is measured for the heaviest known neutron star

    It was measured or witnessed, with the observation cited.

  18. 2024-02-22JWST finds the compact object in SN 1987A

    It was measured or witnessed, with the observation cited.

  19. 2025-01-15Gaia stops observing

    It happened, and the record is settled.

  20. 2025-07 (reported; detection observation December 2024)A close companion to Betelgeuse is probably detected

    It was measured or witnessed, with the observation cited.

  21. 2026-12 (planned)Gaia Data Release 4 scheduleda declared target, not a prediction

    A programme target or declared plan. NEVER a prediction.