Supporting sentence: The Milky Way is a large spiral galaxy, which contains the Solar System, where the Planet Earth revolves around the sun. All objects in the Milky Way orbit the galactic center. It takes the Solar System 225–250 million years to complete one orbit around the galactic center, meaning it has orbited the galactic center 20–25 times since its formation. The Solar System's orbital speed within the Milky Way is 217 km/s.

Supporting sentence: The Milky Way consists of a bar-shaped core region surrounded by a warped disk of gas, dust and stars. Astronomers first began to conjecture that the Milky Way is a barred spiral galaxy in the 1960s. The conjectures were confirmed by the Spitzer Space Telescope observation in 2005 that showed the Milky Way's central bar to be larger than previously thought.

Supporting sentence: The Milky Way is visible as a hazy band of white light, some 30 degrees wide, arching in the night sky. Although all the individual naked-eye stars in the entire sky are part of the Milky Way Galaxy, the term “Milky Way” is limited to this band of light. The light originates from the accumulation of unresolved stars and other material located in the direction of the galactic plane. Brighter regions around the band appear as soft visual patches known as star cloud.

Supporting sentence: The history of the discovery of the Milky Way Galaxy began in the 18th century. This discovery was started by a French astronomer named Charles Messier. Charles Messier first observed a faint object that he called a nebula. Messier considered it a dim body in the sky and continued his observations together with his colleague, Pierre Mechain, eventually documenting 110 nebula objects, although at that time they did not know that some of them were actually galaxies. Messier once hesitated to distinguish between comets and galaxies, as both appeared as blurry objects, except that comet looked dimmer while galaxies appeared brighter. It was not until 1920 that Edwin Hubble revealed that Andromeda Nebula was actually a galaxy outside the Milky Way, after he calculated its distance from Earth and found it to be far beyond the Milky Way. Hubble's discovery became the starting point for scientists in defining galaxies, including the Milky Way Galaxy.

Supporting sentence: The Milky Way contains between 100 and 400 billion stars and at least that many planets. An exact figure would depend on counting the number of very-low-mass stars, which are difficult to detect, especially at distances of more than 300 ly (90 pc) from the sun. The Milky Way may contain ten billion white dwarfs, a billion neutron stars, and a hundred million stellar black holes. Filling the space between the stars is a disk of gas and dust called the interstellar medium.

Supporting sentence: The Galactic Center is the barycenter of the Milky Way and a corresponding point on the rotational axis of the galaxy. Its central massive object is a supermassive black hole of about 4 million solar masses, which is called Sagittarius A, part of which is a very compact radio source arising from a bright spot in the region around the black hole, near the event horizon. The Galactic Center is approximately 8 kiloparsecs (26,000 ly) away from Earth in the direction of the constellations Sagittarius, Ophiuchus, and Scorpius, where the Milky Way appears brightest, visually close to the Butterfly Cluster (M6) or the star Shaula, south to the Pipe Nebula.