Humanity’s exploration of the cosmos is a tale of incredible firsts, discoveries driven by a scientific curiosity that has shaped our understanding of the universe and, ultimately, our place within it.
Join us as we show you where four incredible scientific “firsts” unfolded in the northern hemisphere night sky, ranging from our species’ earliest steps on another world, to the first telescopic discovery of a moon by one of history’s greatest astronomers and more.
1 – The first steps on the moon
Apollo 11 set down on the moon and established Tranquility Base on July 20, 1969, marking the first time in history that humans had landed and set foot on the surface of another world. It remains one of the most impressive technological achievements in humanity’s short history — one that NASA and its partners are struggling to repeat in the modern day with its Artemis program, decades later.
The Apollo 11 landing site is far too small to spot from Earth. However, you can find the general location of Tranquility Base with the help of a 6-inch telescope or binoculars when the vast basaltic plain of Mare Tranquillitatis (the Sea of Tranquility) is bathed in sunlight in the weeks preceding the full moon.
First, find Mare Tranquillitatis, which appears as a dark scar a little above the lunar equator on the eastern (or right) side of the moon’s surface. Next, find the Ritter and Sabine craters to the southwestern edge of the lunar sea. Trace an imaginary line from the bottom of Ritter through the middle of Sabine and follow it for roughly 2.5 times the width of the latter to find the approximate location of the Apollo 11 landing site. You can also find the other five Apollo-era landing sites using our handy observer guide!
2 – The first confirmed exoplanet orbiting a sun-like star
Michel Mayor and Didier Queloz made history in October 1995 when they announced the discovery of the first exoplanet known to orbit a sun-like star. The world, designated 51 Pegasi b, or “Dimidium”, is thought to be a “hot Jupiter” — a breed of giant exoplanets that orbit incredibly close to their parent stars.
Dimidium is located 50 light-years from Earth and was only discovered thanks to the minute “wobble” in light from its parent star 51 Pegasi, which arose as the exoplanet’s gravity tugged on the host star over the course of its 4-day orbit, according to NASA.
To find the ancient light of the star 51 Pegasi, you’ll first need to locate the constellation Pegasus, whose stars glow low on the eastern horizon in the hours preceding sunrise in early spring. Next, find Scheat and Markab — two of the bright stars that form part of the Great Square of Pegasus. 51 Pegasi is a dimmer point of light roughly halfway between the two.
3 – The first star photographed beyond the sun
Astronomer William Cranch Bond teamed up with early photographer J.A. Whipple to capture the first image of a star other than our sun, which they achieved using the Great Refractor telescope at Harvard University on the night of July 16-17, 1850.
About 145 years later, the red giant Betelgeuse would become the first star beyond our sun to have its surface directly imaged by astronomers using the Hubble Space Telescope, as it glowed around 650 light-years from Earth in the constellation Orion.
Vega is found rising above the northeastern horizon in the constellation Lyra after sunset in early spring and soars high overhead as the night wears on, before finally fading from sight almost directly overhead as the sun rises.
4 – The first moons discovered with a telescope
The invention of the telescope in the early 1600s saw the discovery of hitherto unknown moons and planets orbiting within our solar system. The first such discovery was made by famed astronomer Galileo Galilei in 1609, who observed Jupiter with his own version of a “spyglass” telescope and was surprised to find four star-like objects orbiting the gas giant.
We now know those objects to be the natural satellites Io, Europa, Ganymede and Callisto, which astronomers refer to as the Galilean moons in honor of their discoverer. The moons are easy to spot with any modern-day telescope with an aperture of 4-inches or more, or a pair of binoculars!
To follow in the footsteps of Galileo, you simply need to find Jupiter glowing as a steady point of light close to the dimmer stars of the constellation Gemini above the western horizon at sunset. The Galilean moons will appear as bright specks of light arrayed in a line around the gast giant’s disk through a small telescope, much like they did to the old master when he discovered them hundreds of years ago.
Feeling inspired to explore the wonders of the night sky up close? Then be sure to check out our roundups of the best telescopes and binoculars, along with our expert’s tips for new stargazers.
Editor’s Note: If you would like to share your astrophotography with Space.com’s readers, then please send your photo(s), comments, and your name and location to spacephotos@space.com.