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▲ addaon 3 days ago

Is kJy as a brightness unit the abomination I think it is?

▲bqmjjx0kac 3 days ago | parent | next [-]

You nerd sniped me :) In this context, I believe it is a kilo-Jansky, not a kilo-Joule * year.

https://en.wikipedia.org/wiki/Jansky

▲dotancohen 2 days ago | parent [-]

I don't think that replacing two ill fitting but probable units with a single obscure unit is much of an improvement!

▲8bitsrule 2 days ago | parent | next [-]

It appears to have something to do with CGS units.

1 Jy = 10-23 erg s-1 cm-2 Hz-1 (cgs)

only their figure: L9.9 GHz < 2.1 × 10^25 erg s−1 Hz−1

leaves out the cm-2. (So not a density, like Jy. Perhaps 'L' is luminosity? ... As in: "The solar luminosity unit is a measure of the Sun's radiant energy and is equal to 3.828×10^(26) Watts." -(NRAO)

While groping, I found this helpful page called Brightness in Radio Astronomy: http://physics.wku.edu/~gibson/radio/brightness.html

▲dotancohen 2 days ago | parent [-]

I was thinking maybe joules/year e.g. energy/time might be some brightness indicator for some astronomical definition of brightness - especially in the non-optical wavelengths.

But that's division, not multiplication. Another thread in my brain thought maybe the product of the two could be useful for people in that field, sort of how ISP is useful to people in rocketry but us normal people need to divide it by G(earth) to get something intuitive.

▲guenthert 2 days ago | parent | prev | next [-]

I don't think it's obscure in that field or for the target audience. You might want to read the soon to be published distilled and transposed article in popular mechanics ...

▲rbanffy 2 days ago | parent | prev [-]

It’s mentioned in Contact, both movie and book.

▲dotancohen 2 days ago | parent [-]

Thanks. That was one of only two movies based on a book that I enjoyed as much as the book.

▲hdgvhicv 2 days ago | parent | prev [-]

erg s−1 Hz−1 Gave me a headache