The Milky Way's Mass is Much Lower Than We Thought

By Brian Koberlein - September 30, 2023 01:40 PM UTC | Milky Way
How massive is the Milky Way? According to a new study using data from ESA's Gaia spacecraft, less than we thought. A new estimate puts the Milky Way's mass at 200 billion times the mass of the Sun, which is 4-5 times less than previous estimates that pegged it closer to a trillion solar masses. Using detailed information about millions of stars, astronomers were able to build an extremely accurate rotation curve for the Milky Way and use that to estimate its mass. They found that the rotation of the Milky Way isn't typical for large spiral galaxies, decreasing its estimated mass.
Continue reading

It's Official, Antimatter Falls Down in Gravity, Not Up

By Brian Koberlein - September 29, 2023 03:12 PM UTC | Physics
Since the discovery of antimatter decades ago, particle physicists have wondered if these particles were repulsed by gravity. Einstein predicted that despite having opposite charges to its regular matter counterparts, antimatter should still behave like matter does concerning gravity. This has been tricky to confirm experimentally since it's hard to make enough antimatter to observe its behavior. Particle physicists have finally pulled it off, using the ALPHA-g experiment at CERN, generating antihydrogen atoms and then dropping them in a 3-meter tall vertical shaft.
Continue reading

Dark Matter Could Be Annihilating Inside White Dwarfs

By Brian Koberlein - September 29, 2023 01:00 PM UTC | Physics
Astronomers still don't know what dark matter is, but one of its characteristics is that it has a small "cross section," which means that it doesn't interact with regular matter or itself. However, if it's possible to trap dark matter in a region dense enough, it might interact and annihilate, releasing gamma radiation. A new paper suggests that astronomers use gamma-ray observatories to scan white dwarf stars to discover whether there's an excess of radiation coming from them. This might mean there's dark matter trapped inside, providing more clues to its nature.
Continue reading