Like a magnificent jewel adorning the vast expanse of the night sky, the Milky Way is a breathtaking sight to behold. Its soft glow, created by an incomprehensible number of stars too distant to be seen individually, casts a spell on all who gaze upon it. The very name “Milky Way” evokes a sense of enchantment and wonder, derived from the Greek “galaktikòs kýklos” meaning “milky circle”, and the Latin “via lactea”. First studied by Galileo Galilei, who used his telescope to distinguish individual stars within the hazy band of light, the Milky Way has been the subject of fascination and intrigue for centuries.
As we have come to understand more about the Milky Way, we have discovered that it is a barred spiral galaxy, with a diameter estimated at 26.8 ± 1.1 kiloparsecs (87,400 ± 3,590 light-years). Recent simulations suggest that it may extend up to a diameter of almost 2 million light-years, containing a vast area of dark matter and visible stars. It is home to an estimated 100-400 billion stars, and a comparable number of planets. Our own Solar System is located on the inner edge of the Orion Arm, one of the spiral-shaped concentrations of gas and dust that make up the Milky Way.
At its heart lies the Galactic Center, an intense radio source known as Sagittarius A*, which houses a supermassive black hole of 4.100 (± 0.034) million solar masses. Stars and gases in the Milky Way orbit at approximately 220 kilometers per second, revealing that much of the galaxy’s mass (about 90%) is invisible to telescopes, neither emitting nor absorbing electromagnetic radiation. This mysterious mass has been dubbed “dark matter”.
The Milky Way is not alone in the cosmos, as it is part of the Local Group of galaxies, and ultimately the Laniakea Supercluster. But with its stunning beauty and captivating mysteries, it continues to hold a special place in our hearts and minds, inspiring us to reach for the stars and unlock the secrets of the universe.