Calculating Halley's Comet Period and Next Approx. Viewing Date

In summary, the conversation is about calculating the period and next appearance date of Halley's Comet, which has a semi-major axis of 17.96 AU and eccentricity of 0.9673. The relevant equation is Period = T = 2pi(sqrt(a^3/u), but the value of (u) for Halley's Comet is unknown. The assumption is made that Halley's Comet orbits the Sun, not Earth, and the question remains whether it is possible to solve the problem using only the given values.
  • #1
carney
4
0

Homework Statement


Halley’s Comet passed perihelion on 9 February 1986. It has a semi-major axis
a = 17.96 AU and eccentricity e = 0.9673. (One astronomical unit (AU) is the distance
between the Earth and the Sun.) Calculate the period of Halley’s Comet and the
approximate date on which you might next see it.

Homework Equations



Period = T = 2pi(sqrt(a^3/u)

The Attempt at a Solution


I realize all this information is available over the internet but I need to work it out by hand.
I attempted this question first using the value for 'a' given and the standard gravitational parameter (u) of Earth 3.986E14 but realized this is wrong and that halley's comet would have a different value of (u). I assume the equation for the value of (u) of halley's comet will be related to its eccentricity but can't seem to work it out. Any ideas?
 
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  • #2
In determining (u), what does Halley's comet orbit?
 
  • #3
Janus said:
In determining (u), what does Halley's comet orbit?

i just assumed from the question that it was orbiting earth.
 
  • #4
What do comets typically orbit?
 
  • #5
Janus said:
What do comets typically orbit?

thats a very bad assumption. they orbit the sun and i can just look that value up. but using what I've been given and only those values is it possible to work this question out?
 
  • #6
:eek:


It is an excellent assumption.

carney, I give you my blessing to assume your calculations are meant to have Halley's comet orbitng the Sun, not Earth.
 

1. How is Halley's Comet period calculated?

The period of Halley's Comet is calculated using Kepler's third law of planetary motion, which states that the square of the orbital period (P) is proportional to the cube of the semi-major axis (a) of the orbit. By measuring the distance of the comet from the Sun at different points in its orbit, scientists can calculate its semi-major axis and therefore determine its period.

2. What is the current period of Halley's Comet?

The current period of Halley's Comet is approximately 75-76 years. Its last appearance was in 1986 and it is expected to return in 2061.

3. How accurate are the predictions for Halley's Comet's next viewing date?

The predictions for Halley's Comet's next viewing date are accurate to within a few months. However, the comet's path and brightness can be affected by various factors such as gravitational pulls from other planets, making the exact date and appearance difficult to predict with absolute certainty.

4. Can Halley's Comet be seen from anywhere on Earth?

Yes, Halley's Comet can be seen from anywhere on Earth when it is visible. However, the viewing conditions may vary depending on your location and the time of the year. For optimal viewing, it is recommended to be in a dark, clear sky away from light pollution.

5. How often does Halley's Comet pass through the inner Solar System?

Halley's Comet passes through the inner Solar System approximately every 75-76 years. It has been observed and recorded since ancient times, with its last appearance in 1986 and its next expected appearance in 2061.

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