Both stars have large Doppler shifts. The Sun has maintained roughly the same brightness for more than 4 billion years. The Sun's source of energy is the nuclear fusion of hydrogen into helium. If nuclear reactions in the Sun's core stopped suddenly, the Sun would go dark immediately. As an interstellar cloud collapses to become a star, its central region eventually becomes opaque.
Many young stars emit an excess of cool infrared radiation.
The best theories of star formation include surrounding disks. A dwarf star that has exhausted all nuclear energy sources. The fusion of iron nuclei does not occur in stable stars.