The swirling spiral of the elegant galaxy M99 is on display in this week’s image from the Hubble Space Telescope. As a prototypical spiral galaxy, like our Milky Way, M99 has the classical rotating disk of stars, gas, and dust, which is concentrated and bright in the center and reaches out into space with spiral arms. But his particular galaxy isn’t just any spiral galaxy — it is a “grand design” spiral galaxy, a classification given to the neatest and most orderly spiral galaxies whose arms are particularly prominent and well-defined.
The galaxy M99 is located in the constellation of Coma Berenices and is around 42 million light-years from Earth. As well as being visually stunning, this galaxy is an interesting target of research and has been imaged by Hubble’s Wide Field Camera 3 instrument twice, for two different research projects.
The first project M99 was observed for is one which looked at the difference between two types of explosions that can occur at the end of a star’s life: Novae and supernovae. Supernovae are the more dramatic, famous events, in which massive stars run out of fuel and explode in huge, bright events which can send out shockwaves and leave behind distinctive remnants. The less famous novae are dimmer events that happen when white dwarfs in a binary system with a larger star suck off layers of matter from that star’s outer shell.
However, there may be events that exist in between the brightness of these two types of events. “Current astronomical theories predict that sudden, fleeting events could occur that shine with a brightness between that of novae and supernovae,” Hubble scientists write. “Although shrouded in mystery and controversy, astronomers observed such an event in M99 and turned to Hubble for its keen vision to take a closer look and precisely locate the fading source.”
The other project for which M99 was observed was to look at how young stars form from clouds of cold dust, in a project called Physics at High Angular resolution in Nearby GalaxieS with the Hubble Space Telescope (PHANGS-HST).
