Type Ia supernovae are crucial to our understanding of cosmology. But we still don't fully understand what causes them.

Observations from the Dark Energy Spectroscopic Instrument suggest that the rate of cosmic expansion may be changing over the time. While this wouldn't rule out general relativity, it opens the door to modified gravity models, which may better match the data.

Thanks to Hubble, JWST, and the Planck mission, we're starting to see cracks in the current ideas in cosmology, expressed by the Hubble Tension, the Cosmic Shear Tension, and the role dark energy plays in the expansion of the Universe over time. Good news: powerful new instruments are already surveying the Universe and should measure any deviations from the widely held cosmological models. It's a fun time to be an astronomer.

Astronomers are collecting evidence for the gravitational wave background of the Universe, caused by merging supermassive black holes. Now, the MeerKAT radio telescope has confirmed the discovery first made by the NANOGrav experiment, but in a third of the time. For the last five years, MeerKAT has monitored dozens of millisecond pulsars once a week, detecting subtle changes in their radio emissions as gravitational waves flow by.

The planetary science community argues back and forth about when Venus was last habitable. Did it lose its oceans billions of years ago, or more recently? A new paper suggests that Venus has been a hellscape for its entire history. No oceans, ever. This result comes from the ratio of atmospheric chemicals and how quickly they're replenished by volcanic outgassing. On Earth, volcanic eruptions are mostly steam from interior water, but on Venus, they're 6% water at most.