There may have been recent supernovae in our Galaxy that have not been observable even though they are incredibly luminous. How is it this possible?

While contemplating the cosmos, one can't help but be mesmerized by the dramatic finales of stars known as supernovae. A supernova is what occurs when a star reaches the ultimate phase of its life, concluding its multi-million-year journey through the universe in a grand spectacle of light and energy. To understand supernovae, imagine a star several times the mass of our Sun exhausting its nuclear fuel. Without the outward pressure from nuclear reactions to counterbalance gravity, the star's core collapses under its own weight. Within seconds, this collapse triggers a massive explosion, liberating energy that briefly overshadows the collective brightness of billions of stars in its galaxy.

During these cataclysms, supernovae forge heavy elements such as iron—the very material that composes much of the Earth and is an integral part of our bodies. They also shoot these elements into space, seeding future generations of stars and planets. Despite their brilliant flares, which can outshine entire galaxies, some supernovae evade detection from Earth. This paradoxical invisibility underlines the importance of the interstellar medium in governing what we can observe in our galactic neighborhood.

The Milky Way Galaxy, our cosmic home, belongs to a family of galaxies known as barred spiral galaxies. Imagine a grand pinwheel spinning in space, with the Sun located about two-thirds of the way out from the center on one of its spiral arms. The Milky Way boasts a central bulge brimming with ancient stars, enveloped by a flat disk where new stars are born within clusters and nebulae.

The spiral arms, features defining the galaxy's structure, do more than provide a picturesque tableau; they play a pivotal role in the process of star formation. These arms teem with molecular clouds and are often sites where stars end their lives in a spectacular supernova. However, the beauty of the galactic structure also harbors complexities like vast distances between stars, variations in star density, and the presence of dust and gas that can obscure celestial events such as supernovae, making it a challenging endeavor to unravel the true nature of our galaxy.

Between the stars that stud the night sky lies the interstellar medium (ISM)—a rich mixture of gas, dust, and cosmic particles. Though seemingly serene to the casual observer, the ISM is anything but. It's a dynamic arena where interstellar clouds clump together under gravity to birth stars, where the remnants from dead stars enrich the galactic neighborhood, and where the energy from supernovae can trigger the formation of new stars.

The ISM plays a crucial role in the lifecycle of galaxies, acting both as a cradle for star formation and a veil that can conceal stellar explosions. Dust particles within the ISM absorb ultraviolet and visible light, while allowing infrared and radio waves to pass. This absorption can be so extensive that, occasionally, it completely hides a supernova within our own galaxy from our view. Therefore, when studying the galaxy, astronomers must account for the curtains of dust laid out by the interstellar medium to truly comprehend the stellar stage.