Dragonfly 44

This was recently in the news and it brings up the subject of dark matter again.

Astronomers on Maunakea in Hawaii used two telescopes to investigate a dim galaxy that has the same mass as our galaxy, the Milky Way, but only a hundredth of the number of stars. That means that it is composed of 99.9 percent dark matter.

The way they did this was to use the DEIMOS instrument installed on Keck II to measure the velocity of stars in that dim galaxy for 33.5 hours over 6 nights. Then they used the Gemini-Multi-Object Spectrograph on the 8-in Gemini North telescope to find a halo of spherical star clusters orbiting around the core of the galaxy. By calculating the motion of these stars they came up with the mass of the galaxy and it was much higher than the numbers of stars would suggest. The mass turned out to be a trillion times the mass of our sun, which is what the mass of the Milky Way galaxy is.

Unfortunately, this galaxy is 300 million light years away. What astronomers want to find is a dark matter galaxy that's closer so they can look for signals that could reveal what dark matter is made of.

Why is this important? There are several reasons. One is that we had no idea that dark matter galaxies were in existence, and we certainly don't know why they would even form. There is much more dark matter in the universe than normal matter that we can see. The real question is: what is dark matter. Discoveries like this could lead to an explanation of what dark matter is.

It's hard for us to imagine matter as being invisible. It's almost as if it's a ghost. How could this be possible? Ordinary baryonic matter only amounts to 4.9 % of the universe, while dark matter is at 26.8 %. There is no doubt that this stuff exists. Many observations have proven that, but no observation has determined what it's made of.

Baryonic matter is made from protons and neutrons. Everything that we can see is made from this kind of matter. Dark matter is made from something else, something that keeps it from acting like normal matter.

The only thing we can be sure of is that dark matter has mass and therefore has a gravitational effect on normal matter, the kind that makes up stars, galaxies and black holes. At the same time this dark matter can pass through ordinary matter without interacting with it. That's scary! It could mean that dark matter particles are passing through us constantly without us realizing it.

My take on this is that dark matter could be some supersymmetry particle that can interact with the supersymmetry partner of the Higgs boson. I'm not the only one proposing this.
Maybe will soon find out what it really is.

Oh, and by the way, the latest estimate of the number (2 trillion) of galaxies in the universe doesn't change the idea of dark matter. More on this later.

Thanks for reading.