South Oakleigh College ASTROPHYSICS: Sirius

Sunday, June 14, 2009

Sirius

Sirius is the brightest star in the night sky. It appears bright for two reasons.

Firstly it is close to us compared to much brighter stars, which are much more distant. It is only 8.6 light years away [light travelling at 300,000,000 km per second, takes 8.6 years to reach us].

Secondly it is 25 times more luminous than the Sun (if Sirius was our star we would need to always wear dark sun glasses outside, as daylight would be 25 times as strong).

What the naked eye perceives as a single star is actually a binary star system, consisting of the very brightly luminous star Sirius A, and a faint white dwarf companion Sirius B.

A binary star system is one in which two stars are orbiting each other.

Sirius is in the constellation Canis Major (English translation = Big Dog).

It can be seen in Melbourne in late spring as a very bright star rising in the east early in the evening.

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AstroPhysics

Astronomy or Astrophysics is the scientific study of stars, planets, comets and galaxies. Astronomy is one of the oldest sciences when people sought to understand the bright lights in the night sky. The invention of the telescope enabled great progress to be made.

The scientific age began when Galileo Galilei , in Florence, Italy built a telescope similar to the design created by Hans Lippershey In 1610 Galileo published his findings that Jupiter had moons. As a result of Galileo's observations he theorised that the Sun is orbited by Earth and the planets. That the moon is not a planet but orbits the Earth. That Jupiter has its own moons. He challenged the belief that the Earth is the center of the Universe with all the planets, the Sun and the Moon and the Stars in orbit around around the Earth.
Galileo also used his telescope to discover that the Milky Way is composed of stars.

Modern telescopes on Earth have discovered a lot of other galaxies other than the Milky Way, during the 20th Century. It was Edwin Hubble who discovered in 1923, that galaxies exist outside of the Milky Way.

In 1990 a telescope, known as the Hubble Space Telescope, was launched into orbit around the Earth, 600km above the Earth and therefore above the Earth's atmosphere. Being above the atmosphere means that the images captured by the telescope are much clearer than are possible on the surface of the Earth, and therefore much more distant objects can be seen and analysed. Check out these sites [ http://hubblesite.org/ and http://hubble.nasa.gov/ ]