INSpiREzine Stars! | Page 14

STAR: AN ASTRONOMICAL OBJECT

WHAT IS A

A Star is Born:

The Life Cycle of a Star

23

On clear nights, we can see the stars as

twinkling points of light in the sky. But

what exactly are we looking at?

A star is an astronomical object

consisting of a luminous spheroid of

gas, mostly hydrogen & helium, held

together by opposing forces of

energy. At its core, energy is created

by nuclear fusion causing the gases to

expand and exert an outward pressure.

This outward pressure is balanced by

the inward pull of gravity, leaving the

star in hydrostatic equilibrium. This

balance of forces lasts for most of a

star’s life.

The nearest star to Earth is the Sun.

Many other stars (9,096)are visible to

the naked eye at night, appearing as a

multitude of fixed luminous points in

the sky due to their immense distance

from the Earth. However, most of the

estimated 200 sextillion (2×10 ) stars

in the Universe are invisible to the

naked eye from Earth.

Historically, the most prominent stars

were grouped into constellations and

asterisms, the brightest of which

gained proper names. Astronomers

have assembled star catalogues that

identify the known stars and provide

standardized stellar designations.