Our Galaxy-The Milky Way
Describe the appearance of the Milky Way as seen with the naked eye and binoculars or a small telescope
NAKED EYE- There's no clear shape, only a faint, cloudy line stretching across the sky BINOCULARS OR SMALL TELESCOPE: A fuzzy band of light stretching across the sky with brighter patches, light and dark regions and more detail visible
Demonstrate an understanding of the size and shape of our galaxy and the location of the Sun, dust, sites of star formation and globular clusters
Our galaxy is a spiral shape of type Sb. The stars are spread out over different arms, with our Sun on the Orion Arm. Stars are more densely packed at the central bulge of the galaxy. When the Milky Way is looked at from the side, another region is seen extending above and below the flattened disc. This region is known as the halo and contains very much older stars found in globular clusters.
Demonstrate an understanding that the observed Milky Way forms the plane of our own galaxy
The faint band of light that we call the Milky Way is actually the plane of the disk of our galaxy. When we look at the night sky, we see the Milky Way when we look along the plane of this disk, but when we look in other directions, out of the plane, we see far fewer stars
Demonstrate an understanding of how astronomers use 21cm radio waves rather than visible light to determine the rotation of our galaxy
--21cm radio waves are used to investigate the Milky Way because much of the galaxy is transparent to them, so they give us a way to see clearly across the entire galaxy even when visible light is blocked by gas and dust in the spiral arms. --In the spiral arms of the Milky Way galaxy are vast areas of hydrogen gas where new stars are forming. Looking at the spectral line for neutral hydrogen atoms at 21 cm tells astronomers the position of each arm of the galaxy. If the hydrogen line is in the normal position, the arm is moving at the same speed relative to our position. Most of the hydrogen lines are shifted from the normal position due to the Doppler shift, being slightly redshifted. This difference in the position of the hydrogen line shows that the arm is moving away from us. The amount of redshift allows astronomers to work out the speed at which each spiral arm is moving away from us relative to our position. This information is vital for astronomers to accurately work out:- The speed of movement of the spiral arms of the Milky Way, relative to our position The rotation curve of the galaxy can be worked out (how fast each region of the Milky Way is rotating the further away from the centre of the galaxy you travel) Using the rotation curve and speed/velocity values, astronomers can work out distances to certain points in the Milky Way Calculations can be carried out from this information that tell us the mass of the galaxy - and that what is found is more than what we see (there is plenty of unseen matter out there that needs to be discovered)
