# Help! Distance between Mu Leporis & Nihal?

1. May 21, 2004

### MonstersFromTheId

"Dammit Jim! I'm a writer, not a stellar cartographer!"

Doin some homework for a SF story.
I badly need to know the approximate distance between Mu Leporis and Nihal.

Also useful:
Distance from Sol to Mu Lep, distance from Sol to Nihal, warnings about any known odd ball physical effects or interstellar objects between Mu Lep and Nihal that shouldn't be overlooked in a chapter covering a trip between those two stars.
My impression is that there's no reason to expect a trip between Nihal and Mu Lep would involve passing through any known physical obstacles, that left uncovered in such a story, could quickly get my :-) "undying prose" covered by the remains of a knowledgeable reader’s lunch

Tx in advance for any help...
Monsters

2. May 21, 2004

### Janus

Staff Emeritus
About 26 lightyears
184 lightyears
160 lightyears

3. May 24, 2004

### MonstersFromTheId

Thanks Janus!
That's one very tough set of answers to try to did up if you don't know where to look. I really apriciate the help.

4. May 29, 2004

### Nereid

Staff Emeritus
Janus, would you mind giving us your sources, and/or a sketch of how you came up with these numbers?

I think quite a few readers may find it useful to know how to get answers to the kind of question which MonstersFromTheID asked

5. Jun 7, 2004

### Jenab

Bet it had to do with a star atlas and a table of absolute magnitudes. After that it's converting from spherical to rectangular coordinates, the pythagorean theorem and that m-M = 5 log D thingy.

Jerry Abbott

6. Jun 9, 2004

### Nereid

Staff Emeritus
So, Hipparcos (or Tycho) and the Hubble GSC2 perhaps? Then, just trigonometry.

But what about estimates of error? There's very little error in the RA and Dec of the two stars, but the distances?

Extension question: what we see today, from here on the Earth's surface, is the position of the two stars on the celestial sphere ... but they're not 'there' anymore! We can only see where they were, ~184 and ~160 years ago. Is there any relative motion among the three stars? If you were on a planet around one of the other two, where would Sol be? the other star? How much difference would there be in the apparent positions, given that the light times are quite different (~26 years vs ~184 or ~160)? How fast is the ~26 ly changing?

Last edited: Jun 9, 2004
7. Jun 11, 2004

### TeV

joke

Mu lep?
I didn't know LEP is being upgraded so fast!How long is it now?Over 100 ly?
It must be operating on the hell of the EeV now!Why wasn't I informed earlier about this?!

8. Jun 11, 2004

### Nereid

Staff Emeritus
But the only "leptons" it accelerates are tau neutrinos, via an as-yet undiscovered DM-interaction, which is why we've not heard of it yet!
:surprise: :tongue2:

9. Jun 12, 2004

### TeV

D**n it,the detecting techniques must be improved :rofl:

10. Jun 12, 2004

### Jenab

If you know that a star is on the main sequence, you can use its color temperature as an approximation to its effective temperature, and apply the mass-luminosity-radius relation inversely to get the star's luminosity.

T / 5770K = M^(a/4 - b/2)

L = M^a = (T/5770K)^{a / (a/4 - b/2) }

L = (T/5770K)^{ 4 / [1 - 2b/a] }

Typically, for stars having 0.8 to 2 solar masses...

a = ~4.0
b = ~0.72
L = ~ (T/5770K)^6.25

Let v=apparent visual magnitude
Let V=absolute visual magnitude

V = 4.75 - 2.5 log L

v - V = 5 log D

D = 32.61 {10^{ {v - 4.75 + 2.5 [ 4 / (1 - 2b/a) ] log (T/5770K) } / 5 } }

where the logarithms are base 10 and where D is the distance to the star in lightyears.

If you're a writer, though, your main concern should be how John Stirling (a.k.a. "Captain Good") is ever going to get out of the capsule at the bottom of the atmosphere of that gas giant planet, where the evil Galactic Overlord has imprisoned him. Getting a good story written is harder than the astrophysics.

Jerry Abbott

Last edited: Jun 12, 2004
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