Our solar system only has one star, the Sun and it’s massive. With an estimated diameter of 1,391,980 km, it’s more than 10 times larger than the planet Jupiter and 109 times than our own planet, Earth. But how does it fare among the other stars in the Milky way galaxy or in the observable universe? Well, you might be surprised to find out that the Sun is actually far more smaller than some of the stars.
Before we began, there are certain things that you should know-
- Massive stars are expressed in solar unit, where 1 R☉ equals to 695,700 kilometers (actual radius of the Sun).
- Stellar radius/diameters are not precise in almost all the cases as they are approximated with the help of Stefan-Boltzmann law, so there is a plenty of room for errors.
- The size of a star is mainly derived from some important parameters such as stellar luminosity and temperature.
- Inflated atmospheres of supergiants can change size drastically over time. The calculated stellar luminosity of pulsating and variable stars are highly unreliable.
Optical image of Arcturus
Distance: 36.7 light years
Solar Radius: 25.4 R☉
Arcturus or Alpha Boötis is the brightest star in the in the constellation of Boötis and the Northern Celestial Hemisphere. Along with Spica, and Regulus/ Denebola, Arcturus form the popular Spring triangle asterism. Due to its relatively close distance, Arcturus is one of the best studied massive stars. According to the studies, it’s an aging star, more than 7 billion years old and already exhausted its hydrogen core. Compared to the Sun it’s 1.5 times more massive and 25 times its diameter.
Image Courtesy: Wikimedia Commons
Distance: 65.3 light years
Solar Radius: 44.2 R☉
Aldebaran is a red giant of spectral class K, which has evolved from its main sequence phase after depleting its hydrogen core. This has led Aldebaran to astronomically expand 44 times or nearly 61 million kilometers the total diameter of the sun.
One can easily locate Aldebaran in the night sky. All you have to do is to follow the Orion’s belt in a straight line from right to left (in the Southern hemisphere) or left to right (in the Northern Hemisphere) and the very first brightest star you will find is Aldebaran.
13. Rigel A
Distance: 860 light years
Solar Radius: 115 R☉
Rigel A is the most prominent star in the Rigel multiple star system located in the constellation Orion. While it’s outshone by the star Betelgeuse located in the same constellation, its luminosity is around 300,000 times higher than that of the Sun. Rigel A is classified as a blue supergiant, with exhausted hydrogen core which caused it to inflate almost 100 times more than the Sun’s radius.
12. Antares A
Comparing Antares, Arcturus and the Sun
Distance: 550 light years
Solar Radius: 165 R☉
Officially known as Alpha Scorpii, Antares is the biggest and the brightest star in the constellation Scorpius with mass approximately 12 times that of the Sun. While the actual size of Antares is highly disputed due to its inflated outer regions, it does appear to pulsate from the Earth’s point of view.
Just like most of the red giant, Antares is also expected to explode to form a supernova sometime in the next hundred thousand years or so. Apparently, it also has a companion star, designated as Antares B, a B-type main sequence star separated by an angular break-up of 3.3 arcseconds.
11. Pistol Star
Image Courtesy: NASA and UCLA
Distance: 25,000 light years
Solar Radius: 306 R☉
Surrounded by one giant pistol shaped Nebula near the center of the Milky Way galaxy, the pistol star belongs to a rare class of luminous blue variables with luminosity more than 1.6 million times that of the Sun. This distant star was first detected with the help of Hubble Space telescope in the 1990s by astronomers from the University of California. While scientists are currently unable to calculate its approximated age, they believe it will explode in a hypernova in some 3 million years.
10. CW Leonis
CW Leonis In UV /Image Courtesy: NASA
Distance: 310 light years
Solar Radius: 390 – 500 R☉
Located in the constellation Leo, CW Leonis is probably the closest carbon star (a bright red giant with more carbon in its atmosphere than oxygen) to our solar system and the Earth. Based on the available data, researchers are certain that the star will become a white dwarf someday in the far future. It is also suggested that the star is accompanied by a possible binary star in a close proximity.
Betelgeuse captured by ALMA /Image Courtesy: ALMA (ESO/NAOJ)
Distance: Approx. 724 light years (disputed)
Solar Radius: 887- 955 R☉
Betelgeuse or Alpha Orionis is one of the biggest stars in the night sky and the second brightest star in the constellation of Orion. It is well known for its distinctly bright reddish appearance and semi-regular shape. If this red supergiant were in the middle of our solar system, it would entirely engulf the orbits of all the inner planets including Earth and Mars and quite possibly Jupiter. It became the first ever star other that the Sun, whose angular size was measured successfully.
8. KW Sagittarii
Distance: 7,800 light years
Solar Radius: 1,009 R☉
The red supergiant KW Sagittari is located nearly 7,800 light years away from our solar system in the constellation of Sagittarius, near the galactic core. If KW Sagittarii is placed at the center of our solar system instead of the Sun, then it would entirely consume the orbit of Mars and quite possibly the Asteroid belt.
7. NML Cygni
Comparison of planets and stars/ Image Courtesy: Dave Jarvis
Distance: 5,300 light years
Solar Radius: 1,183 R☉
NML Cygni was first discovered by three astronomers Neugebauer, Martz, and Leighton in 1965, who noted an extremely luminous red star. Cygni’s total volume is about 20 billion times that of our Sun. With that setting, if placed in the center of our planetary system, it would easily engulf the orbit of Jupiter and possibly beyond.
6. SMC 018136
Small Magellanic Cloud/ Image Courtesy: ESA/Hubble
Solar Radius: 1,310 R☉
SMC 018136 is an extra galactic M-type supergiant star located in the Small Magellanic Cloud. With bolometric power of over 200,000 times, effective temperature of 3,575 K and radius over 1,300 times the Sun it is without a doubt one of farthest massive stars discovered to date.
5. VV Cephei A
Distance: 4.900 light years
Solar Radius: 1,400 R☉
VV Cephei A is the main component of the VV Cephei eclipsing binary star system located nearly 5,000 light years away at the constellation of Cepheus. This red hypergiant star is estimated to be between 1,050 and 1,100 times the radius of the Sun.
4. VY Canis Majoris
A comparison between the Sun and VY Canis Majoris.
Distance: 3,816 light years
Solar Radius: 1,420 R☉
VY Canis Majoris once held the title of the biggest star in the Milky way galaxy before a much bigger star was detected. Located in the southern constellation of Canis Majoris, it is just too faint to be observed with the naked eye. It is also one of the most luminous stars of its type (M-type hypergiant). The estimated mass of VY Canis Majoris is about 17 times than that of the Sun.
Over the years, there has been lots of controversies regarding its actual solar radius and luminosity. According to some scientists, the star’s enormous solar radii fall far beyond the prediction of the current stellar theory which makes it highly susceptible body. Rather than a hypergiant, many believe that the star is a normal supergiant, with a reduced radius of 600 R☉.
3. Westerlund 1-26
Westerlund 1 in infrared from 2MASS/ Image Courtesy: NASA
Distance: 11,500 light years
Solar Radius: 1,530 – 1,580 R☉
Lying on the outskirts of the Westerlund 1 super star cluster, the Westerlund 1-26 is the second biggest star in the Milky Way galaxy. Even though, its stellar classification is still not clear, it appears to be 3.5 to 4 billion times bigger than the Sun. Located at an astronomical distance of 11,500 light years, Westerlund 1-26 is almost impossible to observe in visible wavelengths due to the presence of huge interstellar dust.
2. WOH G64
Large Magellanic Cloud
Distance: 163,000 light years
Solar Radius: 1,540 R☉
WOH G64 is currently the biggest star in the Large Magellanic Cloud (MIlky Way’s satellite galaxy). Situated at a staggering distance of 163,000 light years from the Earth, this extragalactic star is about 5 billion times bigger compared to the Sun. The star was first detected by three astronomers Westerlund, Olander and Hedin in the 1970s.
1. UY Scuti
UY Scuti compared to the Sun/ Image Courtesy: Philip Park
Distance: 9,500 light years
Solar Radius: 1,708 R☉
UY Scuti was first discovered in the 19th century by a team of German astronomers at the Bonn Observatory, Germany. At that time the star was named BD -12 5055. Located in the constellation of Scutum, it’s currently the largest star known to us. According to estimations, UY Scuti has a radius of 1,708 solar radius and thus 5 billion times bigger than the Sun.
Just for the sake of simplicity, based on the above numbers if this supergiant is somehow placed at the center of our solar system, then its outer atmosphere would most probably engulf the orbit of Saturn. The current stellar model suggests that it will explode to form a supernova before evolving into a yellow giant or a Wolf-Rayet star.