Determining the orbital radius of extrasolar planets

AI Thread Summary
To determine the orbital radius of extrasolar planets, one can use a formula that relates the orbital period to the radius. The period is relatively easy to observe, but the mass of the star, which is also needed for the calculation, is more challenging to determine. By applying the concept that the centripetal force required for circular motion is equal to the gravitational force between the planet and the star, one can derive the necessary equations. Observations of the star's characteristics can help estimate its mass, facilitating the calculation of the orbital radius. Understanding these relationships is crucial for analyzing extrasolar planetary systems.
aggieg
Messages
2
Reaction score
0

Homework Statement


Basically I don't understand how you do this - the course I'm doing keeps mentioning the orbital radius of extrasolar planets but doesn't tell you HOW to find it?
Can anyone please help - in plain English, please, I'm not a natural scientist!


Homework Equations





The Attempt at a Solution

 
Physics news on Phys.org
We have a formula relating the period of the orbit to its radius. It is easy to observe the period, so the radius can then be calculated. The longer answer is that the formula has the mass of the star in it and that mass is not easy to observe. I think some guessing is involved but I don't really know. Stars are very interesting and a lot is known about how they work, so perhaps there is a way to guess the mass fairly well from observations of the star's characteristics.
 
Delphi51 said:
We have a formula relating the period of the orbit to its radius. It is easy to observe the period, so the radius can then be calculated. The longer answer is that the formula has the mass of the star in it and that mass is not easy to observe. I think some guessing is involved but I don't really know. Stars are very interesting and a lot is known about how they work, so perhaps there is a way to guess the mass fairly well from observations of the star's characteristics.

Hi Delphi
Yes, it's actually the formula I'm trying to find
Best wishes
AggieG
 
There is a lovely way to find the satellite formula for circular motion. You begin by saying Fc = Fg
meaning that the centripetal force required to hold the planet in circular motion is provided by the gravitational force between planet and star. Then fill in the detailed formulas for Fg and Fc (choosing the one with the period T in it rather than the one with velocity).
 

Thread 'Errors and significant figures'

I multiplied the values first without the error limit. Got 19.38. rounded it off to 2 significant figures since the given data has 2 significant figures. So = 19. For error I used the above formula. It comes out about 1.48. Now my question is. Should I write the answer as 19±1.5 (rounding 1.48 to 2 significant figures) OR should I write it as 19±1. So in short, should the error have same number of significant figures as the mean value or should it have the same number of decimal places as...
View full post »
Thread 'Collision of a bullet on a rod-string system: query'

Thread 'Collision of a bullet on a rod-string system: query'

In this question, I have a question. I am NOT trying to solve it, but it is just a conceptual question. Consider the point on the rod, which connects the string and the rod. My question: just before and after the collision, is ANGULAR momentum CONSERVED about this point? Lets call the point which connects the string and rod as P. Why am I asking this? : it is clear from the scenario that the point of concern, which connects the string and the rod, moves in a circular path due to the string...
View full post »
Thread 'A cylinder connected to a hanging mass'

Thread 'A cylinder connected to a hanging mass'

Let's declare that for the cylinder, mass = M = 10 kg Radius = R = 4 m For the wall and the floor, Friction coeff = ##\mu## = 0.5 For the hanging mass, mass = m = 11 kg First, we divide the force according to their respective plane (x and y thing, correct me if I'm wrong) and according to which, cylinder or the hanging mass, they're working on. Force on the hanging mass $$mg - T = ma$$ Force(Cylinder) on y $$N_f + f_w - Mg = 0$$ Force(Cylinder) on x $$T + f_f - N_w = Ma$$ There's also...
View full post »

Similar threads

Calculating Angle & Speed to Reach Planet's Moon from Station Orbit
Replies
1
Views
2K
Orbital Periods of Planets vs Comets
Replies
1
Views
1K
From circular orbit to elliptical orbit
Replies
3
Views
2K
Orbital speed variation as a planet orbits the Sun
Replies
5
Views
1K
Calculate Orbital Radius of Planet X
Replies
7
Views
3K
Determine the Orbital Radius of a planet
Replies
4
Views
8K
Calculate Average Temperature of Planet in 0.4 AU Orbit: Albedo 30%
Replies
5
Views
2K
How Do You Calculate the Mass of a Planet in Circular Orbit?
Replies
4
Views
5K
Find Density Given Period of Orbit
Replies
12
Views
5K
Planet orbiting around a star whose mass changes
Replies
7
Views
2K

Hot Threads

Recent Insights

Back
Top