Questions Show: Orbit of the Planets, Green Stars, and Oort Cloud Contamination

We're back to a themeless questions show. We're right across the Universe this time. Why are the planets lined up in a nice flat plane? Why are there no green stars? And is the Oort Cloud contaminating our understanding of the cosmic microwave background radiation? If you've got a question for the Astronomy Cast team, please email it in to info@astronomycast.com and we'll try to tackle it for a future show. Please include your location and a way to pronounce your name.

Orbit of the Planets, Green Stars, and Oort Cloud Contamination

Please vote for Astronomy Cast in the People's Choice Podcast Award! (Astronomy Cast is in the Science and Technology Section, near the bottom.)  Vote every day!

Why are the planets lined up in a nice, flat plane?

• NASA's Astrobiology site answers the question
• The Ecliptic Plane – GSU
• XKCD comic on centrifugal force

Why aren't there any green stars?

• Why aren't there any green stars? – Astronomy Cafe
• Do green stars exist? – Goddard Space Flight Center
• Blackbody radiation -- GSU

Is the Oort Cloud contaminating our understanding of the cosmic microwave background?

• Pamela's Star Stryder post about the CMB & the Oort cloud
• Background on the CMB – Goddard
• Daniel Babich's paper, "What Can the CMB Tell Us About the Outer Solar System?"

Are there any places on Earth where the moon doesn't rise or set for a period of time?

• Q & A on the moon — Inconstant Moon
• Sun & Moon rise and set tables – US Navy
• Rise, Set and Twilight Definitions — US Navy
• Check out Stellarium software and see for yourself!

If we could land on a white dwarf, what would it look like?

• White dwarf stars — Goddard SFC
• Biggest Diamond in the Universe — Universe Today

How do we know our galaxy is a spiral galaxy?

• Sloan Digital Sky Survey
• PlanetQuest's 3-D Guide to the Universe
• The Milky Way Has Only Two Arms — Universe Today
• Spectroscopic Parallax – Australian Telescope

Was space always dark?

• Transparency of the universe – GSFC
• Dark Ages of the Universe – Scientific American
• Cosmic Backlighting: the CMB – Pamela's Star Stryder
• Fluctuations in the CMB – GSFC

Are we expanding along with the universe?

• How Fast is the Universe Expanding? — GSFC
• The Expanding Universe — SDSS

1. Writingindependence Says:
   October 31st, 2008 at 9:10 am

   Uranus has the weird rotational axis going sideways too. What's going on with our proto solar nebula hypothesis?

   Maybe that model needs to be junked, seems we picked up a hitchhiker that coalesced on a different planar orientation than the local norm; or was it far enough out from the sun, slow of period, to simply adopt its own bearings of accretive self organization? Entrainment and the forcing function of the other bodies would seem to govern an extended global attractor basin anisotropy be it ever so weak by the force of gravity over such great distances. Then, given the suspect status of pluto, and Uranus at the edge or limit of planetary attachment, the breakdown of that global basin's influence follows naturally. Neptune is farther out but 2 earth masses heavier than Uranus.

   I would hazard to guess a far more comprehensive model of p.s.n (proto solar nebulae) would be required in any case to address other issues like abundances, something applying a rescaled model or renormalization of not only separate locales but a representatively entire stellar migratory trajectory's corridor over the span of the entire history of the sun's evolution.

   We should get out of the isolated bubble model. The biggest gas giants are indeed a fractal scaling down of the solar system with so many moons of their own.

2. William Says:
   October 31st, 2008 at 2:07 pm

   Contrary to the answer given in the this podcast, there are places on the earth where the moon is above for more than 24 hours at a time.

   Inside the Artic Circle during the Northern Summer Solstice, the Sun does not set below the horizon.

   If you consider the days around New Moon, the moon will be relatively close to the Sun.

   Being in close proximity to the Sun, the Moon itself therefore does not set below the horizon.

   For those of you with access to planetarium programmes, set your location to the North Pole and the date to the start of June. Then advance the time hour by hour and you'll see the sun circle the horizon with the Moon leading or following it, all the time above the horizon. It doesn't set for well over a week!

3. david dickinson Says:
   November 7th, 2008 at 6:50 am

   During the Winter Solstice in the northern hemisphere, the full Moon is also above the horizon as seen from far northern latitudes for over a week at a time… this is because the full Moon occupies the same region of the ecliptic that the Sun does in the summer. I've set up a simulation of this phenomena on our site, http://www.astroguyz.com, to illustrate this bizzare motion; the time lapse is set for Alert, Canada, during next month's full Moon.

4. Richard Webb Says:
   November 10th, 2008 at 7:37 pm

   As a substance is heated, it emits a blackbody radiation spectra that shifts its peak spectral output from red, to orange, to yello, to green, to blue, and beyond. However, this spectrum is never very narrow, so even when the peak is green, plenty of blue and red are also being emitted. This link shows the colors associated with different temperatures: http://en.wikipedia.org/wiki/Color_temperature Also, this site http://www.techmind.org/colour/coltemp.html has a very nice color ramp image http://www.techmind.org/colour/blackbodyglowinfinity.png Note that 6500 K is what is commonly regarded as a reference white color in the video industry. Colors hotter than this appear bluer, but never greener. Colors cooler that 6500K appear redder.

   The greenest color you can get from this is white, but you cannot get any greener than that.

Leave a Reply