NML Cygni

NML Cygni or V1489 Cygni is a red hypergiant star^[2] and one of the largest stars currently known, at about 1,650 times the Sun's radius (equal to 7.67 astronomical units), thus a diameter of about 2,295,000,000 kilometres (1.426×10⁹ mi). If placed at the center of the Solar System, NML Cygni's surface would extend beyond the orbit of Jupiter, filling over half the gap between Jupiter and Saturn's orbit. It contains the volume of approximately 3.6 billion times that of the Sun.

It is one of the extreme luminous hypergiant stars.^[3] Its distance from Earth is estimated to be around 1.6 kpc, or about 5,300 light-years.^[3]

NML Cygni is a part of the Cygnus OB2 association. The Cyg OB2 association spans nearly 2° on the sky, or ∼30 pc in radius at the distance of 1.74 ± 0.2 kpc, thus it is one of the closest massive associations to the Sun.^[4] It has an estimated mass loss rate of 2×10⁻⁴M_⊙yr⁻¹.^[5] The annual parallax of this star is measured to be around 0.62 milli-arc-seconds.^[2]