There are hundreds of billions of stars all around us in the universe. We, the common people, have been hearing the names of some of these stars for a long time. Apart from the Sun, the most famous star on Earth after the Polaris is Sirius. The reason why this star is famous is its brightness. This Sirius is the brightest of all the stars we see in the night sky. Today we will try to know a few things about this star.
The
naming of the star Sirius is derived from the Greek word 'Seirios' which means
incandescent or scorching. There are several other names for this star, such as
Alpha Canis Majoris (α Canis Majoris) or Dog Star.
The
magnitude of brightness of Sirius is -1.6. The smaller the mathematical
magnitude of the brightness of the cosmic objects visible in the sky, the more
the object is considered to be brighter. In terms of brightness, our nearest
star, the Sun, has a magnitude of -26.7. Sirius is twice as bright as Canopus,
the second brightest star in the night sky.
In
terms of distance, this star is 8.6 light years or 2.64 parsec away from our
Sun. (Light Year: The distance that light travels in a year. Parsec: the
largest unit of distance measured in the universe. 1 parsec is equal to 3.26
light years. It is an acronym for Parallax Second). The name Sirius, as we know
it, is a combination of two stars. Their combined mass is much greater than the
mass of the Sun and about 25 times in luminosity. The proximity to Earth makes
this pair of stars look so bright.
As
mentioned earlier, Sirius is actually a combination of two stars, Sirius-A and
Sirius-B. Sirius-A is a A1 class star and faint Sirius-B is a DA2 class star.
These two stars are orbiting each other in every 50.1 years. The shortest
distance between them during this rotation period is 8.2 AU and the longest
distance is 31.5 AU. (AU or Astronomical Unit: The average distance between
Earth and Sun) However, the average distance between Sirius-A and Sirius-B is
20 AU which is equal to the distance from the Sun to Uranus. The last time
these two stars came close (Periastron) was in 1994 when it became virtually
impossible to observe these two stars separately. The last time the two stars
were at their farthest point (Apostron) was in 2014, which means that it takes
40 years for two stars to be closest and farthest twice in a row.
Sirius-A
has a surface temperature of 9,940 Kelvin or 9,666.85 degree Celsius. With the energy
it has, this star will be able to pass another 100 crore or 1 billion years at
ease. Then it will turn from the Main Sequence Star to the Red Giant Star. The
star we see from Earth is actually Sirius-A. Sirius-B is so faint that, it is
virtually impossible to see it with the naked eye in the bright light of
Sirius-A.
Today,
Sirius-B is said to be faint, but we find that the Sirius-B, we see, is only
0.01 percent of the full brightness of the original star of the past. In the
past, this star was a giant star. Even the Sirius-B was bigger than Sirius-A.
When it was the main sequence star, its size was 5 times larger than the Sun.
The phase that Sirius-B has achieved today is the result of a supernova
explosion of 12 crore or 120 million years ago. At present, the mass of
Sirius-B is 1.2 times larger than that of the Sun and the surface temperature
is 25,200 Kelvin or 24,926.85 degree Celsius, which is much higher than that of
Sirius-A. The size of Sirius-B is now equal to Earth. The existence of carbon
and oxygen has been found in Sirius-B due to the nuclear fusion. But since the
nuclear fusion of hydrogen has stopped completely so there is no new
heat-generating reaction inside the core of Sirius-B. As a result of it,
Sirius-B gradually began to cool by radiating heat. Thus for another 200 crore
years or 2 billion years, Sirius-B will radiate all the heat inside it and
change to another form. The estimated age of this constellation is 23 crore or
230 million years. At first, the two stars were bluish-white and orbited each
other for 9.1 years. Although Sirius-B is far ahead of Sirius-A in terms of
X-ray scattering. (The link to know more about the life history of the star is https://spacejagat.blogspot.com/2020/06/the-brief-story-of-stellar-life.html )
Sirius
has been studied by various scientists at different times. The first person to
be named in this regard was Ptolemy, an Egyptian mathematician under the Roman
Empire. He went on to record some information about it. Then, in 1717, the
British astronomer Edmund Haley discovered the pattern of the rotation of a
stationary star based on Ptolemy's research. Among those stars was Sirius. From
then on, the work of measuring the velocity of different stars began. Finally,
in 1868, Sirius became the first star whose speed could be measured. Sir
William Higgins made this impossible task possible in those days. The scientist
Christian Huygens was the first to attempt to measure distance between Earth
and Sirius in 1698, and his method was mentioned in his book Cosmethorus. In
1844, the German astronomer Friedrich Bassel first observed the motion of
Sirius and concluded that Sirius had an invisible companion. But he could not
say anything correctly. Later, on 31st January 1862, the American astronomer
Alvan Graham Clark first observed Sirius's obscure companion, now called
Sirius-B or 'The Pup'. Later that year, on March 7, the existence of
Sirius-B was confirmed. Since 1894, there has been an orbital irregularity of
Sirius every 6 to 6.4 years. Here, scientists thought that Sirius might have
another red dwarf star or massive brown star with a mass 0.05 times the mass of
the Sun. It was named Sirius-C. However, recent observations and research by
the Hubble Telescope have not provided any evidence for the existence of
Sirius-C. Since then, Sirius' orbital irregularities have been a mystery to
scientists.
A
strange fact about this Sirius is that this dual star system is slowly
advancing towards our solar system and currently its speed is -5.5 km per
second. Here the - (negative) sign means that Sirius is heading towards the
solar system, including the Earth. In this way, Sirius will move forward for
the next 60,000 years, and with this progress, brightness of Sirius will
continue to increase. Then again the distance of Sirius with the solar system
will continue to decrees and the brightness will also continue to decrease.
However, it is true to say that for the next 2,10,000 years, this dual star
system will be the brightest star in the night sky on Earth. Besides, another
surprising piece of information must be mentioned here. The orbital speed of
Sirius is only 16 km per second which is less than the farthest man-made
spacecraft Voyager-I. This slow motion of Sirius is not only wonderful but also
completely mysterious.
Another
aspect of Sirius that has not been explained to date is its colour. This dual
star system basically belongs to which colour is a long debatable subject, so
there has been a lot of talk about it for centuries. Some say Sirius is
actually an orange star, some say blue. Thus the presence of different colors
like white, red etc. has been heard. Even Sir John Herschel, an eminent English
scientist, expressed his views on this subject in 1839. In fact, in the last
few thousand years, various opinions have emerged about the colour of Sirius.
But it is also true that the evolution of stars have never been possible in
this period from the time the discussion of the colour of Sirius began, because
if we discuss the various stages of the life history of the star, it will be
seen that this time is short compared to the total life span of the star. So
here again the topic of the mysterious third star Sirius-C comes up again,
which is probably the reason why Sirius is so different in color. But in no way
direct or indirect, Sirius-C was found. So this is a mysterious and
controversial issue about Sirius.
Sirius
is a star that can be seen with the naked eye all year round except for certain
parts of the earth. The star becomes no longer visible as it moves from 73
degree north latitude to higher latitude. There are times in the year when the
sun sets in the clear skies of the Southern Hemisphere and moves below the
horizon, causing twilight to be clearly seen with the naked eye. Sirius will be
available in 2023 for the purpose of long-term observation.
In
1909, Danish scientist Ejnar Hertzsprung considered Sirius a member of the
orbiting group of Ursa Mejor. (A cluster of stars, including Ursa Major, which
were born together from one place 300 crore years ago and have approximately
the same velocity.) It was later determined that Sirius could be a member of
the Sirius Super Cluster in 2003. In addition to Sirius in this super cluster,
there are about a hundred stars like Beta Aurigae, Beta Creteris, Beta Eridani,
Beta Serpentis, Alpha Coronae Borealis etc. This super cluster is one of three
super clusters located within 500 light years or 153.36 parsec from the Sun.
Of
the eight nearest stars to the Sun, two are considered to be the stars of
Sirius. In terms of distance, these two stars are in the fifth place from the
Sun. The nearest star to Sirius is Procyon, which is 5.24 light-years or 1.61
parsec from Sirius.
This
star is still important in different cultures of different countries. The
presence of Sirius has been observed in ancient Greek, Roman, and Egyptian
civilizations. Also in Western European and Scandinavian countries, in Africa,
Mali, Senegal, Zambia, Mauritius, countries of Asia like India, China, Japan,
Korea, Syria, Iran, countries of Oceania like Polynesia, Fiji, among the
ancient tribes of New Zealand, and in various cultures and folklores of North
America and Hawaii the name of Sirius have been found. The name of two-star
system is even mentioned in the holy scriptures of some of the religions of
world.
In
India, Sirius is referred to as deer hunter or hunter or Mrgavyadha. Rudra or
Shiva is represented through this star. In Malayalam culture, it is known as
Makarajyoti in honor of which the Sabarimala shrine has been established in
Kerala.
The
importance of the name Sirius can be seen in many cases in the present age. The
name of the star is associated with an Australian warship in the eighteenth
century and a university in Sydney. The name of Sirius is associated with
famous American automobile company, American ships and a radio station in that
country. Beside these, the name is also very much associated with many stories,
novels, fairy tales, science-fictions, television programs, dramas, science
researches, music tunes created at different times. Examples include the
character of Sirius Black of the novels and movies of Harry Potter, which once
gained response from teenagers around the world.
The
importance of Sirius in various arenas of our lives can be seen from time
immemorial. In the meantime, we have sent our representative for the purpose of
endless journey in the year 1977. As our representative, Voyager-II is slowly
moving towards Sirius with the Golden Record, the index of our identity in the
Infinite Universe. Hopefully, if all goes well and our spacecraft remains
intact, Voyager-II will pass Sirius at the distance of 4.3 light-years, or 1.32
parsec, over the next 2,96,000 years. (The link to know more about the journey
of Voyager is https://spacejagat.blogspot.com/2020/02/voyeger.html )
But
it doesn't have to stop here. We need to know more closely about the other cosmic
objects around us, including Sirius. The scientific explanation of the creation
of this infinite universe will one day be fully revealed to us through the
unraveling of the vast information hidden in them. For this, we have to
constantly and relentlessly observe and research.
DECLARATION: All
The Images Have Been Sourced From Google.
