Observing Stars

Observing the stars You can see the sky at night by the radiation and reflection of the light. "Light" is a well-known term in the electromagnetic spectrum including visible, ultraviolet, infrared, microwave, radio, x-ray and gamma ray regions. The size of the spectrum is so large that there are no obvious areas and some areas overlap each other. Each of these regions in the electromagnetic spectrum represents transverse waves which interact perpendicular to one another and proceed as electric and magnetic fields with different wavelength ranges.

Gaia includes three devices to observe stars. These instruments determine the position, color and movement of stars over time. Gaia uses parallax measurements to calculate the distance of the star that the astronomer considers to be the most important data point. Gaia does this by examining the apparent movement of the star at two different points on its orbit and separating it from the actual movement of the galaxy. The spacecraft watches the goal stars for about 70 times in 5 years. This is the planned duty period. As we are about to finish the duty, Gaia sent back a lot of data.

Evolution of stars has not been studied by observing the life span of a single star because most stellar changes are too late to discover for centuries. Instead, astrophysicists use a computer model to simulate the structure of stars and understand how stars evolved at various points in the life cycle. The evolution of a star begins with the collapse of the gravitational force of macromolecular clouds. Typical macromolecular clouds are around 100 light years (9.5 x 1014 km) and include up to 6,000,000 solar masses (1.2 x 1037 kg). When it collapses, huge molecular clouds divide into smaller fragments. In each of these fragments, the collapsed gas emits gravitational potential energy as heat. As the temperature and pressure rise, the debris condenses into a rotating sphere called the star of the primitive star.

The stars are formed by cold gas in the galaxy and form massive molecular clouds. Several galaxies are observed to form stars at very high speed. This is known as a starburst. If they keep doing so, they will consume their natural gas reserves below the life of the galaxy. Therefore, starburst activities usually last only about 10 million years, which is a relatively short period of time in the history of the Milky Way. In the early history of the universe, the starburst galaxy is more common, still accounting for about 15% of the total star productivity.

In the 1920 's, Edwin Hubble observed stars with different brightness in the light called Andromeda Nebula. He knows that the brightness of these stars will change with their true brightness. Then he saw how bright they looked to find the distance to Andromeda Nebula. Many astronomers thought that the Andromeda Nebula was a solar system within the boundary of the Milky Way at that time. Mr. Hubble shows that this light is actually an independent galaxy - the Andromeda galaxy we know today - the largest spiral galaxy outside our Milky Way