Questions tagged [doppler-effect]

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1answer
96 views

Universe expansion

I'm reading the book "The theory of everything". In the second chapter it says the Universe is expanding, and we know this because the measurements made using the doppler efect to other galaxies gives ...
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2answers
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Cosmological redshift vs doppler redshift

I'm reading Harrison's "Cosmology: Science of the universe" because Harrison focuses on the distinction between cosmological redshift (he calls it expansion redshift) and the Doppler redshift. He ...
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3answers
147 views

How to Distinguish between Temperature and Doppler effect using Black-body radiation?

I understand that the radiation of a body can be described using the curve for black-body radiation. In the sense that a hotter body will be blue shifted and a cooler body will be red shifted. The ...
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0answers
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Doppler Spectroscopy - Finding mass of an exoplanet

An astronomer, T observed the spectrum of a distant star X. The spectral lines were observed to have tiny blueshifts and redshifts regularly with a period of 1.27 years. T concluded that the star is ...
5
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1answer
72 views

How are exoplanets with 10,000 day periods discovered with the radial velocity method?

The radial velocity technique has apparently been used to discover exoplanets with extremely long orbital periods of ~10,000 days. For example, see this link: https://exoplanetarchive.ipac.caltech....
5
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1answer
310 views

Are there any examples where the transverse doppler effect is applied in astronomy?

Are there any astronomical examples where the transverse doppler effect(Horizontal doppler effect) is applied (Derives a meaningful result)?
16
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3answers
3k views

Energy loss from Doppler effect

The energy of electromagnetic radiation is related to frequency; higher the frequency, higher the energy level. If electromagnetic waves have lower frequency when they arrive on Earth than originally ...
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2answers
138 views

Would you expect this planet to be hotter or colder than earth?

I have a lab where given the mass of a star being $1.23$ times the math of our sun, some planets wobble of central start is $273$ days, and the velocity of 79 m/s. I found that the mass of the planet ...
0
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1answer
104 views

What are evidences of stationarity of rotation of galaxies

Recently I have found the article Does There Really Exist the Problem of the Dark Matter in Spiral Galaxies? which states that dark matter does not exist because astronomers are wrong assuming ...
0
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1answer
228 views

How strong is the gravitational stretch we experience from the edge of the universe?

How much gravitational effect do we experience (e.g. maybe -.00001 G or smaller) from the edge of the visible universe? By edge of the visible universe, I am talking about the region of the cosmic ...
0
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1answer
227 views

Question about Hubble parameter (Hubble constant) and measuring it

I see this question in "An introduction to modern cosmology - Andrew Liddle - Wiley Publication": In the real Universe the expansion is not completely uniform. Rather, galaxies exhibit some ...
2
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1answer
265 views

Question about doppler effect

We know that we can use Doppler effect to determine equatorial velocity of a planet. We send a electromagnetic wave with wavelength $\lambda_0$ to an equatorial edge of planet and we get wavelength $\...
10
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1answer
2k views

How do scientists determine if a star's color is due to Doppler shift vs the star's composition vs temperature?

When looking at visible light coming from, say a star, scientists can determine by the shifting of the light towards the red or the blue end of the spectrum to determine if it is moving towards or ...
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2answers
70 views

Can we tell how fast bodies are moving away by measuring their frequency?

It's clear the universe is expanding because light from distant bodies, like galaxies, are shifted towards the red side of the spectrum. In other words, the light measured is more red than it should ...
2
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1answer
554 views

How do we know galaxy GN-z11 is as far away as it is?

The news media recently reported that galaxy GN-z11, formed just 400 million years after the big bang, is much further away than originally thought at perhaps 13.2 billion light years. They say, ...
3
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2answers
429 views

Gravitational red shift vs Doppler redshift: Is the universe really expanding?

Is it possible that the redshift observed by Edwin Hubble is really from a gravitational redshift and the universe isn't expanding as he has predicted? What I think I know thus far is this: Redshift ...
2
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2answers
150 views

How to disentangle a very distant star's relative velocity vs. redshift distance

We measure a star's relative velocity towards or away from us via its Doppler-shifted spectrum. This is also how we measure the distance of very distant stars: measuring the shifts in the spectrum ...
3
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1answer
2k views

How do we know that light is redshifted/blueshifted and not the original light of a star/galaxy? [duplicate]

If a star/galaxy is moving towards us, then its light is blueshifted, and if it is moving away from us, then its light is redshifted. How do we exactly know that the color we are seeing is not part of ...