James Webb never ceases to fascinate us with his images. Last week, we were presented with images of the M74 galaxy, a photo that looks like it came straight out of a Marvel superhero movie.
The image shows an incredible whirlpool that appears to lead directly to the center of the galaxy. This also shows the power of the MIRI instrument used to obtain the images. Looking in the mid-infrared, this camera is particularly sensitive to interstellar dust.
Stars are born in clouds of molecular gas, and these clouds typically contain a lot of dust. Although the mass of gas is much greater, dust is primarily responsible for the electromagnetic emission, which we can capture precisely in the mid-infrared.
It is also worth remembering that in spiral galaxies (like our own Milky Way) these clouds meet in the spiral arms. That’s why we see the pattern so clearly in the space telescope image, simply reflecting the places with the highest density of clouds of gas and dust.
All great, but what about this ghost galaxy story? Has she already died?
No, the galaxy didn’t die — after all, galaxies don’t die.
Although individual stars can disappear or explode as supernovae, the vast majority of stars in a galaxy will last hundreds of billions of years, much longer than the current age of the universe.
So why do we use that name? We saw it all over the headlines as if it was something supernatural, but the explanation is simple, and it has nothing to do with anything otherworldly.
The point is that M74, the “ghost galaxy”, is a low surface brightness galaxy. This means that the luminosity of each piece of this galaxy is relatively low, when compared to other companions. This makes it a difficult object to observe, with a lower contrast.
Difficult for amateur astronomers, of course. When you have a $10 billion space telescope, things change, and we can see the ghost galaxy in all its splendor.