The Milky Way is an incredibly dynamic galaxy with a vast array of occurrences happening at various scales of both space and time. Some of these events happen with remarkable frequency, while others are more rare.
At the smaller scale, stars are constantly being born and dying. In regions like the Orion Nebula, stars form regularly as gas clouds collapse under gravity, igniting nuclear fusion in new stars. Estimates suggest that our galaxy produces around seven new stars per year on average. On the other hand, supernovae, the explosive deaths of massive stars, occur about once every 50 years in our galaxy.
The Milky Way also contains countless planets, many of which have complex interactions with their stars and neighbors. While exoplanet formation and evolution proceed over millions to billions of years, astronomers are able to detect phenomena such as transits and eclipses on much shorter timescales routinely due to the sheer number of stellar systems.
At a larger scale, the movement and interaction of entire star systems and stellar materials are ongoing processes. Our solar system, for instance, takes around 230 million years to complete one orbit around the galaxy’s center. Moreover, the Milky Way is on a collision course with the Andromeda Galaxy, with which it will merge in about 4.5 billion years, although gravitational interactions are already underway.
Furthermore, the Milky Way’s population of stars experiences dynamic changes both in location and velocity, and observations of these stellar motions can happen in observational human timescales, thanks to contemporary technologies.
All in all, the Milky Way is a bustling cosmic metropolis with different processes operating on varying timescales, from near-instantaneous events like gamma-ray bursts to processes spanning millions or billions of years.