George Ellery Hale: The Visionary of Giant Observatories

A Childhood Marked by Astronomy and Innovation

Born on June 29, 1868 in Chicago (Illinois), George Ellery Hale (1868-1938) grew up in an affluent family. His father, William Hale, was an engineer and businessman who encouraged his early interest in science.

Education and early achievements:

• Studied at Massachusetts Institute of Technology (MIT) (1886-1890)
• Invented the spectroheliograph at age 20 (1888) to study solar prominences
• Co-founded the Journal of Astrophysics (1895) with James Keeler
• Received honorary doctorate from University of Chicago (1894)

From the beginning of his career, Hale combined a passion for solar astronomy with exceptional talent for fundraising and organizing ambitious scientific projects.

The Revolution of Modern Observatories

1. Yerkes Observatory (1897)

At just 28 years old, Hale convinced industrialist Charles Yerkes to finance the construction of the world's largest refracting telescope:

• 40-inch (1.02 m) diameter lens
• Cost: $300,000 (equivalent to ~$10M today)
• Location: Williams Bay, Wisconsin
• Affiliated with University of Chicago, it became the center of American astrophysical research

2. Mount Wilson Observatory (1904)

Hale realized that reflecting telescopes were the future of astronomy. He secured funding from the Carnegie Institution to build:

• 60-inch (1.52 m) telescope (1908) - first large modern reflector
• 100-inch (2.54 m) "Hooker Telescope" (1917)
  • Discovery by Edwin Hubble of the expanding Universe (1929)
  • Evidence of the Sun's differential rotation (Hale, 1908)
• First observations of stellar magnetic fields (1908)

3. Palomar Project (1928-1948)

Hale launched the 200-inch (5.08 m) telescope project, completed after his death:

• Funded by the Rockefeller Foundation ($6 million)
• Pyrex mirror (low-expansion glass) cast by Corning
• Inaugurated in 1948 as the Hale Telescope
• Remained the world's largest telescope until 1975

Major Contributions to Astrophysics

1. Solar Physics

Hale revolutionized our understanding of the Sun:

• Discovery of solar magnetic fields (1908) via the Zeeman effect
• Theory of sunspots as magnetic phenomena
• Solar magnetic cycle of 22 years (double the 11-year sunspot cycle)
• Publication of The New Solar Physics (1910)

2. Stellar Astrophysics

His research expanded our knowledge of stars:

• Spectral classification of stars with Annie Jump Cannon
• Study of magnetic variable stars
• Discovery of galactic magnetic fields (1930s)

3. Scientific Organization

Hale played a key role in institutionalizing astrophysics:

• Founding of the International Astronomical Union (IAU) (1919)
• Creation of Caltech (California Institute of Technology, 1910)
• Editor of the Astrophysical Journal (1895-1938)
• Founding member of the National Academy of Sciences

Legacy and Posterity

Despite health problems (hypertension, nervous disorders), Hale left an immense scientific legacy:

• Father of modern observational astrophysics
• Mentor to generations of astronomers:
  • Edwin Hubble (Hubble's law, 1929)
  • Walter Adams (stellar spectroscopy)
  • Harlow Shapley (Milky Way structure)
• The SOHO space telescope (1995) carries an instrument in his honor
• Asteroid (1024) Hale and Hale lunar crater are named after him

He died on February 21, 1938 in Pasadena (California), leaving behind a revolution in our understanding of the Universe. His approach combining cutting-edge technology, international collaboration and long-term vision became the model for major scientific projects of the 20th century.