Introduction to Astronomy Series

It emerged from Bobby's excellent talk last night that John Flamsteed himself cast a horoscope for the time of laying the foundation stone of the Royal Observatory.

This article (scroll down) has an image of the horoscope and a bit of commentary - noting in particular the Latin phrase which (as we learned) translates as "May this keeping you laughing, my friends"!

Elsewhere, a list of other books worth considering...

An interesting question submitted by one of our members...

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In the first part there was a lot of information about red-shift and the expansion of the galaxy.

When the red-shift was observed and the law proposed the existence of dark matter and dark energy was not know.

Has any research been done into the effect of dark matter/energy on light. Could the DM/E cause an effect the appears to be red-shift.

Sound also has a similar property, the doppler effect. But the pitch of the sound can be changed by introducing lighter gasses, such as helium, or heaver gasses, such as Radon.

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So the next time you playground with a party balloon to make a high-pitched voice, you can claim you're doing an experiment on the Doppler effect and dark energy/dark matter!

Well, maybe not. Anyone have any serious suggestions?

quick search gave me this

dark matter and dark energy have an effect no different from comparable mass-energy densities of ordinary matter distributed in the same places would. This is true for dark matter, but not for dark energy. Dark matter, like ordinary matter, causes light rays to converge, hence the phenomenon of gravitational lensing."

source:  https://www.physicsforums.com/threads/do-dark-matter-and-dark-energy-have-an-effect-on-the-red-shift.940668/

Here's some links that may help get you started not meant to  be exhaustive by any means but a quick 20 minutes of search but get's  you pointed in  right direction

60-Second Adventures in Astronomy :by open university  voiced by David Mitchell
https://www.open.edu/openlearn/science-maths-technology/science/across-the-sciences/60-second-adventures-astronomy-0#

How galaxies are  formed
https://science.howstuffworks.com/dictionary/astronomy-terms/galaxy3.htm

Michelle Thaller
https://youtu.be/S0xvS0Nsj6s

Conservation of angular momentum : Bozeman  Science
https://youtu.be/hgcudPr73LU

The Life Cycle of Stars: insitute of physics
https://youtu.be/PM9CQDlQI0A

Classification of Stars: Spectral Analysis and the H-R Diagram
https://youtu.be/Y5VU3Mp6abI

HR Diagram Explained :High School Physics Explained
https://youtu.be/I6E0jNYEe9Q

The Sky at Night 2019 Guides Stars
https://youtu.be/6_O_p2YBEmI

The accelerating Universe: Nobel Laureate Brian Schmidt
https://youtu.be/55pcpTjd3BY

Hubble - 15 years of discovery
https://youtu.be/XeZ3APhUT2Q

Deep Universe: Hubble's Universe Unfiltered
https://youtu.be/W4GKf623Exk

Flight Through the Orion Nebula in Visible and Infrared Light
https://youtu.be/07dve0EnUX8

Who's Afraid of a Big Black Hole! - BBC Horizon
https://youtu.be/2Ux8qxe3_kI

What Was There Before The Big Bang? | Earth Unplugged
https://youtu.be/Ps74ykTk1uc

What is Space Time and How it Works | Documentary Adexon Sceince Network
https://youtu.be/Eb8c_302lxs

Michio Kaku  : The Universe in a Nutshell
https://youtu.be/0NbBjNiw4tk

One of our Members asked about the size of other stars relative to the size of our star, the Sun.

This video sheds some light (sorry!) - even though the planets are spinning in the wrong direction!

https://youtu.be/HEheh1BH34Q

@andy-sawers

Hi Andy,

1) Both dark matter and dark energy contribute to the critical mass of the universe, i.e. to the fact that it is almost the mass required to stop expansion. 

2) Dark matter interacts gravitationally - i.e. it bends light ("gravitational lensing") and influences the rotation speed of galaxies (two of the typical proofs for its existence).

3) However, because it feels and exerts gravitation, it is much more concentrated inside our galaxy (or, generally, around concentrations of mass - look at the bullet cluster). So while the contribution of dark energy to the mass/energy density of our universe is much higher overall than that of dark matter, the density of dark matter inside our solar system is ~1000 times higher than that of dark energy. There is an excellent worksheet on the Royal Observatory website which my children pointed me to recently ( https://www.rmg.co.uk/discover/teacher-resources/exotic-matter-solar-system ).

Regards

Thomas

@andy-sawers

Star radii: Stephenson 2-18 has >2000 times the radius of the sun - that's twice from the sun the distance to Jupiter...

This should provide an overview: https://en.wikipedia.org/wiki/List_of_largest_stars