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Astronomy


Eclipsed

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So yesterday was the first day in my Astronomy Class and I learned that the word Astronomy exists and =/= Astrology,

And that the seasons are actually not based on Earth's distance from the sun during its yearly orbital revolution, but rather by Earth's tilt on its axis.

ie. Earth's distance to the sun during its orbit is actually the closest during January, but the reason it is Winter is because the Earth is tilted away from the sun. Likewise during Summer, we're tilted towards the sun for them maximum heat

I was lied to all these years, next you'll tell me the planet is round!

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Just now, Down said:

AMA about astronomy, I work in laboratory astrophysics. Which contrary to what the name implies means I know a lot about lasers and ultra-vacuum and spectroscopy and shit but nothing about astrophysics and astronomy. :Teeku:

who would win in a fight, neil degrasse tyson or carl sagan

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51 minutes ago, Down said:

AMA about astronomy, I work in laboratory astrophysics. Which contrary to what the name implies means I know a lot about lasers and ultra-vacuum and spectroscopy and shit but nothing about astrophysics and astronomy. :Teeku:

In layman's terms, can you please explain to me how spectroscopes work? I think they determine a star's elemental makeup by measuring the wavelength of the light it emits but I'm not sure

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6 minutes ago, Funyarinpa said:

In layman's terms, can you please explain to me how spectroscopes work? I think they determine a star's elemental makeup by measuring the wavelength of the light it emits but I'm not sure

I'll try to be simple.

Each element/Atom has its own specific wavelengths emitted determined by it's electrons' "position movement" within the atom. Thus each element gives a very specific pattern of wavelengths. These are called energy spectrums. Thus by examining the patterns we can tell what elements are within the star.  Additional info is that the light emitted is due to the electron transitioning energy states. These are actually quite simple as they do not require a large amount of complex math so you can check it out yourself for more :D  

 

Edit: I found a useful pic to describe this Hydrogen_spectra.jpg

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1 hour ago, Nosebleed said:

Uuuh, we learn that the seasons are caused by the Earth's axis in like middle school. What the hell were you learning up until now? :sachi:

Oh, but the Earth is definitely flat! Don't let all those big scientists fool you!

I don't know!!! I don't remember squat about earth/physical science, just biology/chemistry/physics 

 

14 minutes ago, madvanced said:

So is this the "Let's lynch eclipsed with pitch forks and burn him in the stake" thread? If so I'm quite possibly available and perhaps mildly aroused at such an idea.

I HAVE RIGHTS

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5 minutes ago, Funyarinpa said:

In layman's terms, can you please explain to me how spectroscopes work? I think they determine a star's elemental makeup by measuring the wavelength of the light it emits but I'm not sure

The simplest spectroscope you could imagine, and indeed what was used by astronomers a century or two ago, is a prism. A prism deviates each wavelength of light by a different angle and thus allows to view what we call the "spectrum" of the light, i.e. what wavelength we can find in it. Spectroscopy in general is very broad, though.

The explanation iamnoob gave is actually only partial: if you observed the light of the sun through a prism, as you know, you'd see a continuous spectrum (i.e. all the wavelength would be there). That's because the light emitted by stars does not come from the transitions of the atoms in it, but from what is called "black-body radiation", which is purely due to temperature. A physical body without particular other optical properties (hence the black-body term) will emit light according to its temperature, in the form of a continuous spectrum. The peak of this spectrum depends on temperature: on the surface of the sun, around 6000K, the center is around visible light. Cooler stars will look red, hotter stars blue. For bodies at ~300K (30°C) it would be pretty far in the infrared. Yes, we do radiate too.

What happens then is that a part of that black-body radiation is absorbed by the molecules within the stars (the absorption spectrum of a molecule is simply the complementary of its emission spectra), creating small gaps in the otherwise continuous spectrum (not really visible with the naked eye and a simple prism). We can compare those gaps with the known emission spectras of various molecules we test on earth and match them onto the star's spectra.

Emission spectras are more useful when we want information on other stuff like gas clouds in the interstellar medium. Molecules in those regions can get into excited states because of all the shit going around (cosmic rays etc) and then emit light at specific wavelengths which allows us to identify them.

Of course that's only the basics of it: in reality it's more complicated. Stars are mostly made of hydrogen, so it's very easy to see the marks of hydrogen in a spectrum. There's also a bunch of Helium, but the rest is only there as tiny fractions, which means you won't see clear gaps in the spectrum but only slight deviations to the anticipated black-body radiation... There is a whole range of techniques available to astronomers though.

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Maybe not related to astronomy but definable to space. Two games that anyone even mildly interested in space should try are the famous Universe Sandbox 2 (http://store.steampowered.com/app/230290/) Where you can do really anything you want. Want to put VY Canis Majoris in our solar system? Do it! 

The other one is Space engine (http://en.spaceengine.org/) it's a free game in which you can literally go anywhere you want. Want to go to a galaxy 25Gly away and check for life on some planet? Then Space Engine is for you. And it's free!

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2 hours ago, Kiriririri said:
3 hours ago, Eclipsed said:

And that the seasons are actually not based on Earth's distance from the sun during its yearly orbital revolution, but rather by Earth's tilt on its axis.

ie. Earth's distance to the sun during its orbit is actually the closest during January, but the reason it is Winter is because the Earth is tilted away from the sun. Likewise during Summer, we're tilted towards the sun for them maximum heat

People don't know this? :sachi: 

;_; I'll admit, I thought this for very very many years of my life as well. Probably found out like, mid-high school. (I am mid-college now)

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Seems like basic knowledge to me. I know those facts since long ago, only that I don't use them in everyday life so I've gotta think a little to recall them. But when asked about seasons, yes, that's the proper thing to say. Maybe the club will be more interesting later.

Anyway you can just use the thread to discuss astronomy a la Hoshimemo.

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