Summary:

- The article discusses the exoplanet WASP-121b, which is a "hot Jupiter" type planet located about 850 light-years from Earth.
- WASP-121b is known for its extremely high temperature, with an average surface temperature of around 4,600 degrees Fahrenheit (2,550 degrees Celsius), making it one of the hottest exoplanets discovered.
- The article explains that the intense heat on WASP-121b causes the planet's atmosphere to expand and "puff up," giving it a distinctive shape that has been compared to a "hot air balloon" or a "puffy marshmallow."