“Twinkle Twinkle little star
How I wonder what you are “
This line from the most popular nursery rhyme has a profound “meaning”.
The child looks at a star and is filled with wonderment. As a child whenever I used go to my ancestral village I used to spend hours looking at the starry heavens at night. In places far away from big cities you can see tens of thousands of stars on a clear night. In cities there is too much light and you cannot see much. A few days back I looked up at the sky and I could not see more than 5-10 stars. When was the last time you saw a night sky filled with countless stars?? As technology grows would we have so much light at night that would not be able to see the stars. Would our children not wonder about stars? It is wonder that is the foundation of Science. Or would our children confuse Science with Technology and say uneducated statements like ” Science makes our lives easier” : :-O !!
Today in VERITAS we shall wonder about a little star. The name of this star is Betelgeuse and it is not a little star. It is the biggest star known to us. It is about 700 times wider than the sun ie if Betelgeuse were placed where the sun is now its surface would extend beyond the orbits of Mars and even Jupiter… it is that big. The surface temprature of this star is about 6000F which is a lot cooler than our Sun’s 10,000 F. Its low temperature makes it appear red in color.
We have all seen Betelgeuse. It lies at the shoulder of the Orion constellation(“the hunter”). For an idea of its position see the attached gif file. The name Betelgeuse comes from an Arabian phrase: “Armpit of the giant”. We can see the Orion constellation only in winters(in the northern hemisphere). The distance of this star from earth is about 600 light years.
Betelgeuse belongs to a category of stars which called supergiants. Red supergiants are those stars which are approaching their death. A middle age star like our sun has two forces which balance each other: the gravity which pulls the surface inside and the pressure of the nuclear fusion which pushes it outside. When a star is about to die( its hydrogen has nearly finished in the core) then there is no force to counter gravity in the core: . So the core contracts. This causes a lot of heat and starts off bigger nuclear reactions and the star begins finishing up its hydrogen rapidly and starts expanding at a very fast speed. It then becomes a red super giant. Betelguese is a star going through this expansion. Such a star has a very small dense core surrounded by a gassy exterior. Some very violent reactions are going on in the core: the core is fusing not only hydrogen into helium but also bigger elements together(nitrogen , Silicon… all the way to iron!). One day the core will blow up in a huge explosion leaving the exterior of the star in space as a huge huge cloud. This cloud would later form new stars. The death shall be a new beginning. All that would be left of such a huge giant is a small neutron star : about the size of a town.This is the remnant of the dense core. A single spoonful of this neutron stars would weigh a million kgs.
Betelgeuse was the first star to be pictured as a disc ie the first star whose “surface” was photographed. Is this the largest star? Maybe not… Some Astronomers believe that Mira in the constellation Cetus is probably larger. The Story of Mira we shall take up in some later VERITAS.
“Up above the sky so high… like a diamond in the sky”
Go, wondrous creature! mount where Science guides:
Go, measure earth, weigh air, and state the tides:
Instruct the planets in what orbs to run,
Correct old time and regulate the Sun;