Questions tagged [units]
Use for questions about standards of measurement used for different types of quantities, and for conversions between units.
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Astrodynamic Canonical Units [closed]
Maybe this is more appropriate for the Physics or Maths, but anyway.
I am struggling with applying Canonical units with formulas. I am struggling specifically with how they are used, am I to convert ...
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Natural units of star clusters angular momentum and energy
I'm calculating the total angular momentum of a bunch of theoretical stars of a few solar masses, separated by a few light years, moving at velocities of about a few dozens of km / sec.
Mechanical ...
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How are people converting intensities in Janskys to Kelvin?
I'm reading some ALMA proposals and I am often seeing a conversion from Jy to Kelvin when, for example, people quote noise levels or source flux.
For example on their sensitivity calculator
(https://...
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Why don't astronomers use meters to measure astronomical distances?
In astronomy distances are generally expressed in non-metric units like: light-years, astronomical units (AU), parsecs, etc. Why don't they use meters (or multiples thereof) to measure distances, as ...
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wavelength-based IFU data cubes VS velocity-based IFU data cubes
I have 2 simulated IFU data cubes of the same observation, let's say A and B. The 3rd dimension of cube A is in wavelengths. In order to create cube B I just rebinned cube A in log-wavelengths and ...
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${\rm W/m}^2$ to Jansky [duplicate]
Lets assume I have a source and receive $8 \times 10^{-20}$ ${\rm Wm}^{-2}$ in (400-750) nm filter. How do you convert this received flux to the unit Jansky, is there a formula? (Ultimately, I want to ...
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Why levels of radio contours maps are given in mJy/beam and what does it mean?
I know what a jansky is, but I don't understand what beam (in $\frac{1 Jy}{beam}$) is.
If jansky is a unit of flux density, what kind of unit is $\frac{1 Jy}{beam}$?
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Does the age of the universe take into account General Relativity / Special Relativity?
It is generally accepted that the age of the universe is approximately 12-15 billion years old based on the speed of the expansion of the universe. Since everything is moving very fast away from us, ...
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Converting ångström spectral dimension to galaxy speed (km/s)
I have a spectral cube (in FITS format) whose spectral dimension is in ångströms. The sampling along the spectral dimension is 0.28A (CDELT=0.28). The observation in the cube is Ha emission of a ...
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Is the Earth-Sun distance 1.012 AU?
Wolfram Alpha's query: Sun Earth distance in AU gives:
1.012 au (astronomical units)
They definitely use this value in other places too - e.g. Earth-Sun $L_1$ distances from Earth and from Sun ...
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Astrophysical "unitised" version of the Gravitational constant
This question relates formalising the gravitational constant, $G$, (which in S.I. units is usually quoted as $\sim6.67\times10^{-11}\,\mathrm{m}^{3}\,\mathrm{kg}^{-1}\,\mathrm{s}^{-2}$) in units which ...
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What is projected separation and how can I make sense of its unit (h^-1 kpc)?
I have been reading this paper on the separation of a binary quasar in which it states:
At a projected separation of 8.3/h kpc (Omega_matter = 1), CTQ 839 would be the smallest projected separation ...
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How to scale down solar system data to simulatable values
Okay, I am seriously ashamed for asking this especialy when I geniualy study on physics but there is something that bugs me with the simulation I am working on.
I am re-creating the solar system in an ...
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What are the units of distance in this subtended angle calculation?
I'd like to find the distance at which a 2.4 cm coin is subtended by an angle of 10". I've drawn my diagram and found that $D=\dfrac{d}{\alpha}$ using the small angle approximation. Since $10" = 4.85\...
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How often and over what period is Earth’s rotation averaged to compute UT1?
I understand that UT1 (and for that matter UT0, UT2, etc.) are based on averages of actual earth rotation, and serve as a form of mean solar time. However it’s not clear to me when these averages are ...
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