Groundbreaking milestones in space and cosmology, keyed to the month they occurred. From the Big Bang to Falcon 9 landings.
After 13 years exploring the Saturn system, Cassini deliberately dove into the planet's atmosphere to protect its potentially habitable moons from contamination. It transmitted science data until it burned up.
SOURCENASA's Double Asteroid Redirection Test intentionally rammed a 570 kg spacecraft into the moonlet Dimorphos at 22,530 km/h, successfully changing its orbit — the first practical test of planetary defense.
SOURCEThe Sun crosses the celestial equator moving south. Day and night are approximately equal worldwide, and northern autumn (or southern spring) officially begins. Also marks the start of Libra in the astronomical zodiac.
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A collapsing molecular cloud fragment gave birth to the Sun and its planets. Meteorite dating pins this event to within a few million years, with September marking it in Sagan's Cosmic Calendar.
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Johann Galle found Neptune within 1° of where Urbain Le Verrier had calculated it should be, based on perturbations in Uranus' orbit — a triumph of Newtonian physics.
SOURCEWilliam Cranch Bond and George Phillips Bond, along with William Lassell independently, discovered Hyperion — later revealed to have chaotic rotation and a peculiar sponge-like appearance.
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The most distant human-made object, now over 24 billion km from Earth in interstellar space. Carries the Golden Record — a message to any who might find it.
SOURCEMichel Mayor and Didier Queloz announced the first confirmed planet orbiting a normal star other than our Sun. A 'hot Jupiter' completing an orbit every 4.2 days, it overturned assumptions about planetary formation and won them the 2019 Nobel Prize.
SOURCENASA confirmed the probe had crossed the heliopause the previous August, becoming the first human-made object to enter the space between stars.
SOURCELIGO detected the merger of two black holes 1.3 billion light-years away — the first direct observation of gravitational waves, exactly a century after Einstein predicted them. Announced Feb 2016; the discovery signal remains dated Sep 14, 2015.
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