Our Universe is mysterious yet beautiful. We’re blessed with nebulae, cosmic clouds, planets, moons, and more stars than we can count. Stars are always fascinating!!They appear tiny when seen from the earth due to the larger distance but actually are way more bigger.
The Milky Way galaxy is the home to billions of stars, many of which are brighter,hotter and larger than the sun. Stars are luminous objects of diverse shapes. There are lots of stars in the Universe, we can say almost uncountable.
We may have questions like how big are they? Are all stars of Similar shape or size? If not ,then which is the biggest star of this entire Universe?? What is it like?? Who discovered it?? Well, Stephenson 2-18 is the largest star of the universe but formerly it was Uy Scuti.
Here in this article we will explore all details about Stephenson 2-18, what makes it unique and astounding, its significance, Special features and we will do Comparisons with other known stars like Uy scuti ,Our Sun etc.
Introduction
Stephenson 2-18 also known as Stephenson 2 DFK 1, RSGC2-18 holds the record of largest star surpassing other stars like VY Canis Majoris and UY Scuti. However before the discovery of this red supergiant , Uy scuti was considered as the largest star. But with more accurate observation, it turns out that it is not nearly as large as once thought. So at present, Stevenson 2-18 is the record holder.
Stephenson 2-18 is the part of a relatively small cluster of stars known as Stephenson 2 and is basically the 18th star in there.
This substantial star lies in the constellation of scutum which is a type of small constellation located in the southern celestial hemisphere (southern sky) in our Galaxy Milky Way. So, Stephenson 2-18 belongs to the Milky Way Galaxy which is a huge collection of stars ,dust and gas. The sun also lies in the Milky Way Galaxy, held in one of the spiral arms, about 25,000 light-years away from the centre of the galaxy.
It is a red supergiant star located in the constellation of Scutum. It is one of the largest stars known, with a radius of 2,150 times that of the Sun. This means that if this Stephenson were placed at the centre of the Solar System, its outer layers would extend past the orbit of Saturn.
Stephenson 2-18 is also one of the most luminous stars known, with a luminosity of 440,000 times that of the Sun. This means that it emits more light than 440,000 Suns combined. It is located about 19,000 light-years from Earth. It is a member of the open cluster Stephenson 2, which is about 1.5 billion years old. It is a very unstable star. It is expected to explode as a supernova within the next few million years.
Distance from Earth
Stephenson 2-18 is around 19000 light years away from the earth which is equal to almost 6000 parsecs. However, the former largest star; Uy scuti is just around 9500 light years away from the earth.
History of Discovery
This star was discovered by the astronomer Charles Bruce as a cluster of red supergiants in a photographic deep Infrared Survey in the year 1990.
However, Stephenson 2-18 was discovered in 2007 by a team of astronomers led by Brian Skiff. The team was using the 2MASS infrared survey to search for new stars in the constellation of Scutum. The team was surprised to find a star that was so large and luminous. They named the star Stephenson 2-18 after the open cluster that it is a member of.
Position in space
This star is a super giant of the spectral type M6 and a member of the open cluster. Further, this red hypergiant is located within the constellation of scutum, the same as the second largest star of the universe i.e Uy Scuti. This substantial star is located 18900 light years away from the earth.
Size and mass
This tremendously bright supergiant is located in the constellation of scutum and has extreme luminosity. This means that if Stephenson 2-18 were placed at the centre of the Solar System, its outer layers would extend past the orbit of Saturn. The radius of this biggest star is almost 2150 times the sun’s, whereas its volume is nearly 10 billion times of our Sun.
Significance
It is very difficult to determine the size of stars ,and most difficult for single Stars. Depending upon the different variables, type of instrument used ,a star may have a fairly accurately determined size, or one with a wide range of error. Uy Scuti once held the record of largest star but with more accurate observations ,it doesn’t not even fall under top 10.
The radius of Stephenson 2-18 is way larger than that of Uy Scuti. Thus, new stars discovered with a large radius signify that our technologies for searching astronomical bodies have really improved and are more precise than the previous one.
Interesting Facts About Stephenson 2-18
- The precise mass of the St2-18 is not known yet, but according to an estimation of scientists, it could be around 30 to 50 times the sun’s mass. Some data suggests, Stephenson 2-18 is so large that it could fit about 13 quadrillion Earths and 10 billion stars as the size of the sun inside it
- 2. Stephenson 2-18 is a part of a relatively small open cluster of stars known as Stephenson -2 which is 1.8 billion years old and St2-18 is basically the 18th Star in there.
- 3.Although huge red supergiants have modest luminosity ,it is one of the most luminous red supergiant stars of the universe with a spectral type of M6. Stephenson 2-18 has a luminosity equal to that of 440,000 Suns put together Whereas the usual luminosity of any red supergiant star is around 30,000 to 50,000 times the sun’s luminosity .Thus this much of high luminosity is totally unusual for this largest star. Due this anomalous property it exists at the top right corner of the Hertzsprung–Russell diagram for its M6 spectral type.
- 3.Stephenson 2-18’s photosphere or effective temperature is around 3200K which is less .The reason behind this is red supergiant stars are cool in nature.
- 3.Stephenson 2-18 is located about 19,000 light-years from Earth .
- 4.When Stephenson 2-18 is replaced with our Sun, it is considered that it may swallow up each and every object of the solar system including all of our planets due to its larger size and strong gravity.
- 5.Stephenson 2-18 is a very unstable star. It is expected to explode as a supernova within the next few million years.
- 6.Its external temperature is less than our sun.
Comparisons
Stephenson 2-18 vs Uy Scuti
The formerly largest star of the universe, UY scuti has an estimated ratio of 1.188 billion kilometres and lies in the constellation of the scutum. According to recent measurements Uy Scuti is no longer the largest star of the Universe , it does not even fall in top 10. It lies somewhere in top 100.
If Uy scuti were the centre of our solar system, its photosphere would reach just past the orbit of Jupiter; however Stephenson 2-18 ‘s photosphere would engulf the orbit of Saturn. Stephension is bigger than Uy scuti by 422 solar radii and the gravity of Stephenson 2-18 is way more stronger than that of Uy scuti. Further, Uy Scuti belongs to M2 Spectral type Star whereas Stephenson 2-18 falls under M6 Spectral type Star.
The difference between Uy scuti and Stephenson 2-18 is tabulated below:
| Features | Stephenson 2-18 | Uy scuti |
| 1.Radius | 1.4958 billion km | 1.1883 billion km |
| 2.Distance from earth | 18,900 light years | 9,459 light years |
| 3.Luminosity | 437,000 L☉ | 340,000 L☉ |
| 4.Surface Temperature | 3,200 K | 3,365 K |
| 5.According to Volume , | 10 billion suns can fit inside Stephenson 2-18 | 5 billion suns can fit inside Uy scuti. |
Stephenson 2-18 and Uy Scuti Similarities
- Both are red supergiant stars .
- 2. Both exist in the same constellation called Scutum.
- 3. They have almost the same effective temperature.
Stephenson 2-18 vs Uy sun
The Sun is the hot glowing ball of hydrogen and helium which is 4.5 billion years old. This yellow dwarf star lies in the centre of our solar system and has a radius of 696,340 km. Difference between Stephenson 2-18 and Uy Sun is tabulated below:-
| Features | Stephenson 2-18 | Uy Sun |
| Radius | 1.5 billion km | 700,000 |
| Effective temperature | 5500k | 3200k |
| Type | Yellow dwarf star | Red supergiant, largest star in the Universe |
Stephenson 2-18 vs Uy Scuti vs vy Canis Majoris
Canis Majoris is an oxygen rich extreme red supergiant which is smaller than both Stephenson 2-18 and Uy scuti. The overview of Canis Majoris is tabulated below:-
Uy Scuti Vs Canis Majoris
Both Uy Scuti and Canis Majoris were considered as the biggest star of the Universe at some points. But now none of them falls under the category of Top 10 biggest stars.
Uy Scuti is larger than that of Canis Majoris. The diameter of VY Canis Majoris is 1.9758 billion kilometres while UY Scuti has a diameter of 2.4 billion kilometres.
UY Scuti is situated in the constellation Scutum, the shield but VY Canis Majoris is hidden away in Canis Major, the big dog.
Stephenson 2-18 vs earth
Earth is very tiny in comparison to Stephenson 2-18 . You might be shocked that; the largest star of the universe Stephenson 2-18 can hold 13 quadrillion Earths in it.
Quasi star vs Stephenson 2-18
Quasi stars are the biggest stars, even giant stars like Stephenson 2-18 ,Uy Scuti are smaller in front of it; despite this Quasi star does not hold the record of largest star because these stars are hypothetical, and are just ideas, and likely not existent.
Stephenson 2-18 Real Image
Stephenson, the member of the open cluster, occupies an area of 1.8′ of the sky but is not visible in amateur telescopes. The cluster can be seen in infrared light and is not detected in visible light because it is heavily obscured.
The first image of Stephenson 2-18 was captured in 2007 by the 2MASS infrared survey. The image was taken using the 2MASS All-Sky Survey Camera, which is a 1.3-meter telescope located at the Cerro Tololo Inter-American Observatory in Chile.
The image of this giant star was captured by a team of astronomers led by Brian Skiff. The team was using the 2MASS infrared survey to search for new stars in the constellation of Scutum.
Conclusion
Stephenson 2-18 is one of the most amazing stars in the universe. This large, luminous, and unstable star is expected to explode as a supernova within the next few million years. This star is a reminder of the power and beauty of the universe and of course is a mystery in itself.
Among the stars discovered till date , Stephenson 2-18 is the largest star. Though it is the largest known star discovered so far there could be much bigger stars than this in our incredible universe. All the astronomical bodies of the Universe are still not discovered. With the advancement in science and technology we might be able to calculate the precise size of these objects in the Universe and get another new largest star. Who knows??