Galaxies & Cosmology – A. Our Galaxy (the "Milky Way") & others Flashcards
Describe the appearance of the Milky Way as seen with the naked eye.
With the naked eye it looks like a furry light irregular column in the sky. We only see this bright long area.
Describe the appearance of the Milky Way as seen with binoculars.
With binoculars, the Milky Way’s haziness is cleared a little and we can make out small stars.
Describe the appearance of the Milky Way as seen with a small telescope.
With a telescope we can see that the Milky Way comprises of countless stars which we can see clearly. Sweeping along the Milky Way this continues, we will see less stars than in the Milky Way plane.
Why do astronomers use 21 cm radio waves rather than visible light to determine the rotation of our Galaxy.
It is more accurate to study the rotation of our galaxy by radio waves because we can only see part of the sky with visible light. The 21cm (centimetre) range is known as the Hydrogen line which allows us to see past clouds of interstellar cosmic gas and dust. The centre of the galaxy has a lot of this.
What does a spiral galaxy look like?
The spirals arms wind around the nucleus.
What does a barred spiral galaxy look like?
Spiral Barred (or Barred Spiral) The spirals extend from a bar through the nucleus.
What does an elliptical galaxy look like?
These come in a general ellipse shape. Some are spherical, some are cigar shaped. Typically they are brighter towards the centre.
What does an irregular galaxy look like?
Irregular galaxies do not fit into the tuning fork diagram and usually bear no relation to the shapes of other galaxies or have any obvious symmetry. Their strange shape may have arisen because of disturbances from other galaxies.
What type of galaxy is the Milky Way?
Spiral galaxy (Sb).
Galaxies emit large quantities of which radiation in addition to visible light?
Like stars and nebula, galaxies emit radiation that can be seen in the electromagnetic spectrum. This includes visible light, radio waves, ultra-violet, infrared, x-rays and gamma rays.
How is an Active Galactic Nucleus (AGN) powered?
The area at the centre of an AGN is powered by a supermassive black hole. The amount of material spinning around the black hole forms an accretion disc. The heat caused by its speed and the effect of it falling into the black hole produces enormous radiation across the electromagnetic spectrum.
What are some types of active galaxies?
Seyferts, Quasars, Blazers,
How do astronomers obtain evidence for the existence and properties of AGNs.
Scientists cannot see the black hole but they can sometimes see radiation at different wavelengths forming an accretion disc, or by looking for jets of material thrown out of the galaxy by the gravity of the black hole.
Describe the Local Group of galaxies.
We also have companion galaxies orbiting very close to the Milky Way in the form of Magellanic Clouds. The nearest, the Large Magellanic Cloud orbits just 170,000 light years away from us. The Small Magellanic Cloud is slightly further, while the Andromeda Galaxy, the largest galaxy in the Local Group is 2 million light years away. Other notable galaxies include the Triangulum Galaxy
Can galaxies be grouped in larger clusters and super-clusters?
Yes, The Milky Way Group is part of a larger group again called a cluster. We are in the Virgo Supercluster.
