can someone do me a favour and translate into AU how far out the C and D stars are, please?
i don't understand arc-seconds and arc minutes, but i get AUs.
Psi Serpentis question
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can someone do me a favour and translate into AU how far out the C and D stars are, please?
i don't understand arc-seconds and arc minutes, but i get AUs.
Arcseconds and arcminutes are measures of the angular separation between two objects in the sky. An arcminute is 1/60 of a degree, and an arcsecond is 1/60 of an arcminute. To convert that to distance, you need to know how far the star system is and apply the small-angle formula. In this case, since they're all about the same distance from us, it's a simple matter of arithmetic and we don't need the formula; if 5.9 arcmin corresponds to 5200 AUs, then Psi Ser C is (3.5/5.9)*5200 = about 3100 AU and Psi Ser D is (2.9/5.9)*5200 = about 2600 AUs.
Note that the entry says Psi Ser E is "at least 5200" AU from the A/B pair. A single measurement doesn't really tell you what the stars' actual distance from each other is, because unless you're looking from directly perpendicular to the orbital plane, they'll appear to move closer and farther from each other as they orbit. They could actually be farther apart than this; these numbers just represent the component of their separation that's perpendicular to our line of sight. (Imagine there are two pieces on opposite corners of a chessboard with 1-inch squares and you're looking at them from the side. To you, they look like they're 8 inches apart left-to-right; but they're also 8 inches apart front-to-back, so their actual distance is 8 times the square root of 2 or 11.3 inches.) So these are all minimum figures; Psi Ser C is at least 3100 AU from the A/B pair and Psi Ser D is at least 2600 AU away.
Note that the entry says Psi Ser E is "at least 5200" AU from the A/B pair. A single measurement doesn't really tell you what the stars' actual distance from each other is, because unless you're looking from directly perpendicular to the orbital plane, they'll appear to move closer and farther from each other as they orbit. They could actually be farther apart than this; these numbers just represent the component of their separation that's perpendicular to our line of sight. (Imagine there are two pieces on opposite corners of a chessboard with 1-inch squares and you're looking at them from the side. To you, they look like they're 8 inches apart left-to-right; but they're also 8 inches apart front-to-back, so their actual distance is 8 times the square root of 2 or 11.3 inches.) So these are all minimum figures; Psi Ser C is at least 3100 AU from the A/B pair and Psi Ser D is at least 2600 AU away.
so, you could easily have planets orbiting PS A, B, C, D or E without the stars affecting the planets (around the other stars) too adversely?
^^Oh, easily. At that distance, there'd be no significant effect at all from the other stars' gravity. A & B are close enough that their planetesimal disks might be truncated so they'd have smallish planetary systems, but they could still have them.
goody. PS A is the home-star for my alien ally race in my OU-book. :smug: i'm giving them a mythology based around the stars as their 5 gods...
Well, keep in mind that Psi Ser A is actually a close binary pair, at least according to one source: http://www.stellar-database.com/Scripts/search_star.exe?Name=psi+serpentis
So it's more like six gods, two of which would be twins.
So it's more like six gods, two of which would be twins.
GodThingFormerly
A Different Kind of Asshole
Wouldn't work. With those separations and brightnesses, an observer at any one of those stars would just see the others as relatively bright points of light in the night sky. The only exception is that if the planet orbited the A component, its inhabitants would presumably be able to see the disks of both stars making up the close binary pair. Unfortunately, ISDb doesn't give enough information about the separation of that pair; presumably its binary nature has been deduced purely from spectroscopy rather than direct observation. So it would be a matter of speculation just how close together they are. Indeed, I can't find confirmation anywhere else that Psi Ser A even is a close binary. It's possible ISDb's info is erroneous or at least unverified.