There are at least two types of mass in the Universe: dark mass (matter) and every day mass. The former represents about 83% of the matter in the Universe, but it has never been directly observed. In that way, it is “missing”. (Or at least it was before Zwicky proposed it – and it will still be “missing” if that theory, though generally accepted, proves to be wrong.) The latter type of mass, the sort we encounter every day, makes up 17% of the matter of the Universe, but of that 17%, some is “missing”. Until now:
Undergraduate Amelia Fraser-McKelvie made the breakthrough during a holiday internship with a team at Monash University’s School of Physics, locating the mystery material within vast structures called “filaments of galaxies”.
Monash astrophysicist Dr Kevin Pimbblet explained that scientists had previously detected matter that was present in the early history of the universe but that could not now be located.
“There is missing mass, ordinary mass not dark mass … It’s missing to the present day,” Pimbblet told AFP.
“We don’t know where it went. Now we do know where it went because that’s what Amelia found.”
Part of the reason dark matter has not been directly observed is that it doesn’t interact (by and large) with the electromagnetic spectrum. That makes it rather invisible – even if we utilize different wavelengths (such as infrared light or microwaves). But this other matter does interact with lightwaves. It just happens that the correct lightwaves are X-rays:
Fraser-McKelvie, an aerospace engineering and science student, was able to confirm after a targeted X-ray search for the mystery mass that it had moved to the “filaments of galaxies”, which stretch across enormous expanses of space.
This is pretty interesting stuff, especially since it was an undergraduate who combed the data to show that they had detected these “filaments”. She even got published in a prestigious journal, Monthly Notices of the Royal Astronomical Society. So congratulations to Amelia Fraser-McKelvie, and good luck in the future. I just hope her future work comes with more in-depth news articles for those of us who aren’t physicists.