HubbleSite reports:

Astronomers have put together the largest and most comprehensive “history book” of galaxies into one single image, using 16 years’ worth of observations from NASA’s Hubble Space Telescope.

The deep-sky mosaic, created from nearly 7,500 individual exposures, provides a wide portrait of the distant universe, containing 265,000 galaxies that stretch back through 13.3 billion years of time to just 500 million years after the big bang. The faintest and farthest galaxies are just one ten-billionth the brightness of what the human eye can see. The universe’s evolutionary history is also chronicled in this one sweeping view. The portrait shows how galaxies change over time, building themselves up to become the giant galaxies seen in the nearby universe. [Continue reading…]

Bjørn Ekeberg writes:

What do we really know about our universe?

Born out of a cosmic explosion 13.8 billion years ago, the universe rapidly inflated and then cooled, it is still expanding at an increasing rate and mostly made up of unknown dark matter and dark energy … right?

This well-known story is usually taken as a self-evident scientific fact, despite the relative lack of empirical evidence—and despite a steady crop of discrepancies arising with observations of the distant universe.

In recent months, new measurements of the Hubble constant, the rate of universal expansion, suggested major differences between two independent methods of calculation. Discrepancies on the expansion rate have huge implications not simply for calculation but for the validity of cosmology’s current standard model at the extreme scales of the cosmos.

Another recent probe found galaxies inconsistent with the theory of dark matter, which posits this hypothetical substance to be everywhere. But according to the latest measurements, it is not, suggesting the theory needs to be reexamined. [Continue reading…]