122 Chapter 2 From the Solar System to the Milky Way
Several famous telescopes that aided scientists in making many important discoveries about
the universe are introduced below.
Mount Wilson Observatory 100-inch (2.54 m) Hooker Telescope
This telescope was used by Edwin Hubble (who will be introduced in Chapter 3)
to make his great discovery linked to the riddle of the galaxies and the birth of the
universe, now known as Hubble’s law. It was completed in 1917 and was known as
the world’s largest telescope for approximately 30 years.
Mount Palomar Observatory 200-inch (5.08 m) Hale Telescope
The Hale telescope snatched the title of “world’s largest telescope” from the Mount
Wilson Observatory when it was completed in 1948 and retained this distinction for
27 years. Its high performance helped 20th-century astronomers discover over 100
Hubble Space Telescope
Launched by the space shuttle Discovery in 1990, this man-made satellite telescope
orbits Earth at an altitude of approximately 600 km (373 miles). Although its aperture
of nearly 2.4 m (8 feet) is less than half that of the Mount Palomar Observatory tele-
scope, it can make high-precision astronomical observations, since it is unaffected by
the atmosphere or weather. It continues to make major discoveries such as proving the
existence of planets outside the solar system and clarifying the nature of dark matter.
National Astronomical Observatory of Japan Hawaii Observatory Subaru Telescope
This is the world’s largest optical infrared telescope. It was completed by the National
Astronomical Observatory of Japan in 1999, and the diameter of its primary reflecting
mirror is 8.2 m (27 feet)!
When a mirror is this large, it usually ends up being distorted by its own weight.
However, technology for correcting this distortion was reﬁned by the Mitsubishi Electric
Corporation, which enabled this telescope to be fully operational. The Subaru telescope
continues to produce magniﬁcent results, such as discovering an extremely distant
cluster of galaxies, nearly 12.88 million light-years from Earth.