The discovery of Dark Energy in 1998 by two teams helped us learn what will happen at the end of the Universe. It was the work of the Supernova Cosmology Project and High-Z Supernova Search Team whose competing studies of the deceleration parameter using Type Ia supernova gave us a glimpse of the ultimate fate of the universe. Their discovery of Dark Energy, the cosmic negative pressure that’s pushing the universe apart was confirmed by NASA’s WMAP and ESA’s Planck Microwave Satellites. The data is now completely in, and the results and implications are astonishing. Dark energy may, in fact, be Phantom Energy, which will cause a Big Rip as the universe accelerates exponentially in its expansion. There could also be a grand heat death of the cosmos where it just gets larger and darker and colder for all time.

Deceleration parameter: https://en.wikipedia.org/wiki/Deceler...
Type Ia supernova: https://en.wikipedia.org/wiki/Type_Ia...
Supernova Cosmology Project: http://www-supernova.lbl.gov
High-Z Supernova Search Team: ttps://www.cfa.harvard.edu/supernova/HighZ.html
Planck Microwave Satellite: http://www.esa.int/Our_Activities/Spa...
Dark Energy: https://science.nasa.gov/astrophysics...
Dark Energy: https://en.wikipedia.org/wiki/Dark_en...
Phantom Energy: https://en.wikipedia.org/wiki/Phantom...
Ultimate fate of the universe: https://en.wikipedia.org/wiki/Ultimat...
Heat death of the universe: https://en.wikipedia.org/wiki/Heat_de...
The Big Rip: https://en.wikipedia.org/wiki/Big_Rip
Graphical timeline from Big Bang to Heat Death: https://en.wikipedia.org/wiki/Graphic...
Planck 2018 results. VI. Cosmological parameters: https://arxiv.org/pdf/1807.06209.pdf
Equation of state (cosmology): https://en.wikipedia.org/wiki/Equatio...)