The Smallest Stars In The Universe
The massive stars in the universe are either red hypergiants or red supergiants;
in extreme cases, they are more than 1,500 times bigger than the Sun. But what about
the smallest stars? Are there stars smaller than our Sun? Well, actually there are. The
smallest stars in the universe are generally the tiny (astronomically speaking) red dwarfs. These
red dwarfs are the most abundant and among the least luminous stars in the universe. The smallest
stars in the universe are generally the tiny (astronomically speaking) red dwarfs. These
red dwarfs are the most abundant and among the least luminous stars in the universe. One popular
example of a red dwarf is the Proxima Centauri located 4.2 light years away from the Earth.
It has only 12% of the Sun’s mass and is about 14% of its total size. The radius of Proxima is
about 100,000 km. That’s pretty small right, but it’s not the smallest star discovered till now.
Curious to know the smallest stars ever discovered?? Keep Watching!!
Here's the exciting list of some of the smallest stars in the universe:
1- CM Draconis A which is an eclipsing binary system approximately 47 light-years away in the
constellation of Draco (the Dragon). The system consists of two nearly identical red dwarf stars
located in the constellation Draco. The two stars orbit each other with a period of 1.27 days with
a separation of 2.7 million kilometres (0.018 AU). Along with two stars in the triple system
KOI 126, the stars in CM Draconis are the lightest stars with precisely measured masses and radii.
Consequently, the system plays an important role in testing stellar structure models for
very low mass stars. These comparisons find that models underpredict the stellar radii
by approximately 5%. This is attributed to consequences of the stars' strong magnetic
activity. According to the system's entry in the Combined General Catalogue of Variable Stars, at
least one of the components is a flare star and at least one is a BY Draconis variable. CM Draconis A
has a mass of about 0.2310 the solar mass and a radius of about 0.2534 the solar radius.
2- Ross 154 which is a star in the southern zodiac constellation of Sagittarius. It has an apparent
visual magnitude of 10.44, making it much too faint to be seen with the naked eye. The distance
to this star can be estimated from parallax measurements, which places it at 9.69 light-years
(2.97 parsecs) away from Earth. It is the nearest star in the southern constellation Sagittarius,
and one of the nearest stars to the Sun. Moreover, It is a red dwarf, meaning it’s producing energy
by burning hydrogen in its core. Compared to the Sun, Ross 154 has only 17% of its mass
and about 24% of its radius. Ross 154 has a mass of about 0.17 the solar mass and a
radius of about 0.24 the solar radius and Due to its relatively higher rotational speed,
astronomers believe that it might be younger than the Sun. In about 157,000 years or so,
this star will make its closest approach to the Sun at 6.39 light years.
3- CM Draconis B which is the second red dwarf in the CM Draconis star system
mentioned above. It is slightly less massive and has a smaller radius than CM Draconis
A. It is also cooler than its companion. CM Draconis B has a mass of about 0.2141
the solar mass and a radius of about 0.2396 the solar radius.
4- Barnard’s Star which is a red dwarf about six light-years away from Earth in the constellation
of Ophiuchus. It is the fourth-nearest-known individual star to the Sun after the three
components of the Alpha Centauri system, and the closest star in the northern celestial hemisphere.
Its stellar mass is about 14% of the Sun's. Despite its proximity, the star has a dim
apparent magnitude of +9.5 and is invisible to the unaided eye; it is much brighter in the
infrared than in visible light. Barnard's Star is among the most studied red dwarfs
because of its proximity and favorable location for observation near the celestial equator.
Historically, research on Barnard's Star has focused on measuring its stellar characteristics,
its astrometry, and also refining the limits of possible extrasolar planets. Although Barnard's
Star is an ancient star, it still experiences star flare events, one being observed in 1998.
Barnard’s star has a mass of about 0.144 the solar mass and a radius of 0.196 the solar radius.
5- Ross 248 which is a small star approximately 10.30 light-years (3.16 parsecs) from Earth in
the northern constellation of Andromeda. Within the next 80,000 years, Ross 248 is predicted to
be the nearest star to the Sun for a brief time, overtaking the current nearest star and triple
system, Alpha Centauri. Despite its proximity it is too dim to be seen with the naked eye.
This star has about 12% of the Sun's mass and 16% of the Sun's radius, but only 0.2% of the Sun's
luminosity. It has a stellar classification of M6 V, which indicates it is a type of main-sequence
star known as a red dwarf. This is a flare star that occasionally increases in luminosity.
Ross 248 has a mass of about 0.136 the solar mass and a radius of 0.16 the solar radius.
6- Wolf 359 which is a red dwarf star located in the constellation Leo, near the ecliptic.
At a distance of approximately 7.9 light years from Earth, it has an apparent magnitude of 13.54
and can only be seen with a large telescope. Wolf 359 is one of the nearest stars to the Sun;
only the Alpha Centauri system (including Proxima Centauri), Barnard's Star and the
brown dwarfs Luhman 16 and WISE 0855−0714 are known to be closer. Its proximity to
Earth has led to its mention in several works of fiction. Its radius is estimated to be about 16%
of that of the Sun or in other words somewhere about 110,000 km. To understand it better,
we can compare Wolf 359 with the planet Jupiter, which is slightly smaller with an equatorial
radius of about 71,492 km. Furthermore, Wolf 359 is also characterized as a flare star due to the
sudden bursts in its luminosity. This is due to elevated magnetic activity on its surface.
Researchers believe the star is relatively younger with age less than 1 billion years.
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7- Proxima Centauri which is a small, low-mass star located 4.244 light-years
(1.301 pc) away from the Sun in the southern constellation of Centaurus.
Its Latin name means the "nearest star of Centaurus". Proxima Centauri is a red dwarf star
with a mass about an eighth of the Sun's mass and average density about 33 times that of the Sun.
Because of Proxima Centauri's proximity to Earth, its angular diameter can be measured directly.
Its actual diameter is about one-seventh the diameter of the Sun. Although it has a very low
average luminosity, Proxima is a flare star that undergoes random dramatic increases in brightness
because of magnetic activity. The star's magnetic field is created by convection throughout the
stellar body, and the resulting flare activity generates a total X-ray emission similar to
that produced by the Sun. The mixing of the fuel at Proxima Centauri's core through convection,
and its relatively low energy-production rate, mean that it will be a main-sequence star for
another four trillion years. Additionally, it has a radius of about 0.14 the solar radius.
8- Luyten 726-8 A and B, Gliese 65 or Luyten 726-8 is a binary star system located about 8.7 light
years away from the Sun in the constellation of Cetus. Both the stars in this system have similar
radius, however Luyten 726-8 A is slightly more massive than its sibling Luyten 726-8
B. They also exhibit similar brightness when seen from the Earth. Both the stars,
Luyten-726-8 A and B are variable stars (a star with fluctuating brightness) and
flare star (sudden outburst of powerful flares) simultaneously. However, Luyten-726-8 B appears
to be more active and violent than its companion. Their radii are of about 0.14 the solar radius
and their masses are approximately 0.102 and 0.100 the solar masses, respectively.
9- OGLE-TR-122 B, OGLE-TR-122 is a binary stellar system
containing one of the smallest main-sequence stars whose radius has been measured.
It was discovered when the Optical Gravitational Lensing Experiment (OGLE) survey observed the
smaller star eclipsing the larger primary. The orbital period is approximately 7.3 days.
The system's primary is thought to resemble the Sun. The smaller star, OGLE-TR-122B,
is estimated to have a radius around 0.12 solar radii, or around 20% larger than Jupiter's,
and a mass of around 0.1 solar masses, or approximately 100 times Jupiter's. This makes
its average density approximately 50 times the Sun's. Its mass is close to the lowest possible
mass for a hydrogen-fusing star, estimated to be around 0.07 or 0.08 solar masses. The observed
transit provides the first direct evidence for a star with a radius comparable to Jupiter's.
10- TRAPPIST-1 which is an ultra cool red dwarf star with a radius slightly larger than the
planet Jupiter, while having 84 times Jupiter's mass. It is located 39.6 light-years (12.1 pc)
from the Sun in the constellation Aquarius. Seven temperate terrestrial planets have been detected
orbiting the star, a larger number than detected in any other planetary system except Kepler-90.
Although it is slightly larger than Jupiter, it is about 84 times more massive.
High-resolution optical spectroscopy failed to reveal the presence of lithium,[33] suggesting
it is a very low-mass main-sequence star, which is fusing hydrogen and has depleted its lithium,
i.e., a red dwarf rather than a very young brown dwarf. If by any chance the star were smaller than
its current state, it wouldn’t have the needed mass to burn hydrogen and would be a brown dwarf.
Various scientific researches have concluded that TRAPPIST-1
is about 7.6 billion years old with an error of 2.2 billion years. Because of its low luminosity,
TRAPPIST-1 can live as long as 12 trillion years, which is much longer than the Sun.
11- 2MASS J0523-1403 which is a very-low-mass red dwarf about 40 light-years from Earth in
the southern constellation of Lepus. With a very faint visual magnitude of 21.05
and a low effective temperature of 2074 K it is visible primarily in large telescopes
sensitive to infrared light. 2MASS J0523−1403 was first observed as part of the Two Micron
All-Sky Survey. 2MASS J0523−1403 has a luminosity of 0.000126
the solar luminosity, a radius of 0.086 the solar radius, and an effective temperature
of 2074 Kelvin. These values are currently the lowest known for a main-sequence star.
12- EBLM JO555-57Ab which is the smallest star ever discovered, EBLM J0555-57 is a triple star
system approximately 600 light-years from Earth. EBLM J0555-57Ab, the smallest star in the system,
orbits its primary star with a period of 7.8 days, and at the time of discovery, was the smallest
known star with a mass sufficient to enable the fusion of hydrogen in its core. EBLM J0555-57,
also known as CD−57 1311, is a triple star system in the constellation Pictor,
which contains a visual binary system consisting of two sun-like stars separated by 2.5":
EBLM J0555-57Aa, a magnitude 9.98 spectral type F8 star, and EBLM J0555-57B,
a magnitude 10.76 star. No orbital motion has been detected but they have almost identical radial
velocities and are assumed to be gravitationally bound. EBLM J0555-57Ab’s radius is comparable to
that of Saturn’s and it has a mass of about 0.081 the solar mass or 85.2 Jovian masses.
Thanks For Watching Everyone!! Do you know why the smallest neutron stars, white
dwarfs or stellar mass black holes in the list? Did you learn anything new from this video? Let me
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