Size comparison: Arcturus vs R136a1

Size comparison between the two stars, Arcturus and R136a1.

Arcturus is an old star, its surface gravity is low. It is close to the sun. Its temperature is average. While R136a1 is a very young star, with a fairly high surface gravity, a very high temperature. Its luminosity is much higher.

Object	Arcturus	R136a1
Type	Star, red giant	Star, Wolf-Rayet
Age	7.1 billion years	300,000 years
Diameter	35,374,170 km	49,301,000 km
Mean radius	17,687,080 km	24,650,500 km
Mass	2.13 × 1030 kg	4.55 × 1032 kg
Surface gravity	0.46 m/s²	100 m/s²
Circumference	111.1 million km	161.1 million km
Surface area	3.93 × 1015 km2	8.26 × 1015 km2
Volume	2.31 × 1022 km3	7.06 × 1022 km3
Sun distance	36.7 light years	163,000 light years
Luminosity	6.49 × 1028 W	3.32 × 1033 W
Photosphere temperature	4,286 K	56,000 K
Spectral classification	K1.5 IIIFe-0.5	WN5h
Absolute magnitude	-0.31	-8.09
Right ascension	14h 15m 39,67s	5h 38m 42,43s
Declination	+19° 10′ 56,67″	−69° 06′ 02,2″

Note: if one of the objects is not visible, it just means that it is too tiny to be displayed compared to the other one.