Stirring the interstellar soup

This serene spiral galaxy hides a cataclysmic past. The galaxy IC 758, shown here in today’s NASA/ESA Hubble Space Telescope Picture of the Week, is situated 60 million light-years away in the constellation Ursa Major.

In this Hubble image captured in 2023, IC 758 appears peaceful, its soft blue spiral arms curving gently around its hazy barred centre. But in 1999, astronomers spotted a powerful explosion in this galaxy: the supernova SN 1999bg. SN 1999bg marked the dramatic end of a star far more massive than the Sun.

It’s not yet known how massive this star was before it exploded. Researchers will use these Hubble observations to measure the masses of stars in SN 1999bg’s neighbourhood, which will help them estimate the mass of the star that went supernova. The Hubble data may also reveal whether SN 1999bg’s progenitor star had a companion, which would give additional clues about the star’s life and death.

A supernova represents more than just the demise of a single star — it’s also a powerful force that can shape its neighbourhood. When a massive star collapses, triggering a supernova, its outer layers rebound off its shrunken core. The explosion stirs the interstellar soup of gas and dust out of which new stars form. This interstellar shakeup can scatter and heat nearby gas clouds, preventing new stars from forming, or it can compress them, creating a burst of new stars. The cast-off layers also become ingredients for new stars.

[Image Description: A spiral galaxy with a generally soft and slightly faint appearance. It glows most brightly around the pale yellow bar across its centre. It has two spiral arms which wrap around the centre, quickly broadening out to join a wide, faint circular halo around the galaxy. Glowing, sparkling patches in the disc show stars forming in nebulae. Behind the galaxy, distant galaxies appear as orange dots on a black background.]