Stephenson 2 DFK 1 facts for kids
 Stephenson 2 DFK 1 together with its supposed parent cluster Stephenson 2 (upper left), viewed by the Two-Micron All Sky Survey. Credit: Université de Strasbourg/CNRS (2003) |
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| Observation data Epoch J2000 Equinox J2000 |
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|---|---|
| Constellation | Scutum |
| Right ascension | 18h 39m 02.3709s |
| Declination | -06° 05′ 10.5357″ |
| Characteristics | |
| Evolutionary stage | Red supergiant, possible extreme red hypergiant |
| Spectral type | ~M6 |
| Apparent magnitude (G) | 15.2631±0.0092 |
| Apparent magnitude (J) | 7.150 |
| Apparent magnitude (H) | 4.698 |
| Apparent magnitude (K) | 2.9 |
| Astrometry | |
| Radial velocity (Rv) | 89 km/s |
| Proper motion (μ) | RA: −3.045±0.511 mas/yr Dec.: −5.950±0.480 mas/yr |
| Parallax (π) | −0.0081 ± 0.3120 mas |
| Distance | 18,900 ly (5,800 pc) |
| Details | |
| Radius | 2,150 R☉ |
| Luminosity | 436,516 (90,000–630,000) L☉ |
| Temperature | 3,200 K |
| Other designations | |
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Stephenson 2 DFK 1, Stephenson 2-18, 2MASS J18390238-0605106, IRAS 18363-0607, DENIS J183902.4-060510, MSX6C G026.1044-00.0283
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| Database references | |
| SIMBAD | data |
Stephenson 2 DFK 1, also known as Stephenson 2-18, is a giant star in space. It is found in the Scutum constellation. This star is either a red supergiant or an even bigger red hypergiant.
It is located near a group of stars called Stephenson 2. This group is about 19,000 light-years away from Earth. Stephenson 2 DFK 1 is one of the biggest and brightest stars we know of in our Milky Way galaxy.
Stephenson 2 DFK 1 is incredibly huge. Its estimated radius is about 2,150 times bigger than our Sun. This means it could hold nearly 10 billion Suns inside it! If you could travel around its surface at the speed of light, it would take almost 9 hours. For comparison, it would only take 14.5 seconds to go around the Sun. If Stephenson 2 DFK 1 were in the middle of our Solar System, its outer edge would reach past the orbit of Saturn.
Contents
How We Found This Star
The group of stars called Stephenson 2 was first found in 1990. An American astronomer named Charles Bruce Stephenson discovered it. He used special infrared surveys to see stars that are usually hidden.
The brightest star in this area was first called '1'. Scientists thought it might not be part of the Stephenson 2 group. This was because it was so bright and a bit far away from the main cluster.
Later, the same star was given the number 18. It was thought to be part of a smaller group near Stephenson 2. This is why it's often called St2-18. To avoid confusion, scientists sometimes add "DFK" to its name, like Stephenson 2 DFK 1.
Scientists have studied Stephenson 2 DFK 1 many times. They use powerful telescopes to learn about its properties. These studies help us understand how giant stars behave.
How Far Away Is It?
When Stephenson 2 was first found, scientists thought it was very far away. They estimated it was about 30,000 light-years from Earth. This was much further than we think it is today.
In 2007, a study suggested it was closer. They estimated the distance to be about 19,000 light-years. This distance is based on how fast the star group is moving.
Another study in 2010 also found a similar distance. They said it was about 18,000 light-years away. This places the star in the Scutum–Centaurus Arm of our Milky Way galaxy. However, it's important to know that measuring these distances is very hard. There can be a lot of uncertainty in the numbers.
Some scientists think Stephenson 2 DFK 1 might not be part of the Stephenson 2 group at all. This is because its speed is a bit different from the other stars in the cluster. If it's not part of the cluster, its exact distance might be different too.
What Is It Like?
Its Type
Stephenson 2 DFK 1 is usually called a red supergiant. These are very large and bright stars. But some scientists think it might be a red hypergiant. This would make it even more extreme.
It might be close to a stage where it loses its outer layers. After this, it could become a luminous blue variable or a Wolf–Rayet star. These are other types of very active, massive stars.
How Bright Is It?
Scientists measure a star's total brightness, called its bolometric luminosity. The first estimate for Stephenson 2 DFK 1's brightness was in 2010. It was thought to be about 90,000 times brighter than our Sun.
Two years later, a new calculation was made. This one suggested it was much brighter, almost 440,000 times brighter than the Sun.
The most recent estimate says it could be up to 630,000 times brighter than the Sun. This makes it one of the brightest stars known. However, its light is a bit unusual. This makes it harder to measure its exact brightness.
How Hot Is It?
In 2012, scientists estimated Stephenson 2 DFK 1's surface temperature. They found it to be about 3,200 K. This is quite cool for a star. It's even cooler than what most star theories predict for red supergiants.
How Big Is It?
Based on its brightness and temperature, its radius is estimated to be about 2,150 times the Sun's radius. This is much larger than what most theories predict for the biggest red supergiants (around 1,500 times the Sun's radius).
If this estimate is correct, it means Stephenson 2 DFK 1 is bigger than other famous giant stars. These include Antares A, Betelgeuse, VY Canis Majoris, and UY Scuti.
Losing Mass
Stephenson 2 DFK 1 is losing a lot of its material into space. It loses about 1.35 times the mass of the Earth every year. This is one of the highest rates known for any red supergiant.
It's possible that it recently lost a huge amount of its outer layers. This would explain why it gives off so much infrared light. Some studies show it has strong emissions, which means it's losing a lot of mass.
Is It Part of the Cluster?
Scientists have debated whether this star truly belongs to the Stephenson 2 cluster. Its speed is a bit slower than the other stars in the group. This makes some scientists think it might not be connected.
However, some argue that it could still be a member. The difference in speed might be because the star is expanding. This expansion could make it seem like it's moving differently.
Another idea is that Stephenson 2 DFK 1 is part of a related group of stars. This group, called Stephenson 2 SW, is thought to be at the same distance as the main cluster.
Why Are We Not Sure?
There's still some uncertainty about Stephenson 2 DFK 1. Its distance is not perfectly known, and its membership in the cluster is debated. Its speed is also different from other stars in Stephenson 2. Because of this, some scientists think it might be a red supergiant that is not related to Stephenson 2 or other nearby star clusters.
The estimated size of 2,150 times the Sun's radius might also be too high. Theories suggest that the largest red supergiants are around 1,500 times the Sun's radius. Also, estimates for its brightness vary a lot. This means we are still learning about this amazing star.
See also
In Spanish: Stephenson 2-18 para niños
- R136a1 – one of the most massive and luminous stars known
- List of largest known stars
- List of most massive stars
- Westerlund 1 W26
- NML Cygni
