# Calculating Speed of Halley's Comet at Aphelion/Perihelion

• swelzba9
In summary, the conversation is about finding the speed of Halley's Comet in km/sec at aphelion and perihelion using a specific formula. The person asking for help has not been able to get practical answers and is wondering if they need to convert their units. The other person suggests considering conservation of angular momentum as another equation for a simultaneous solution.
swelzba9
I am trying to figure out the speed of Halley's Comet in km/sec. at aphelion and perihelion... my answers just don't seem to be practical.. please help thanks...

I am using

v² = (4Π²a³) / (P²) * ((2/r) - (1/a))

where a = mean distance from the sun (semimajor axis of the ellipse)
P= sidereal period (75 years)
r = distance of the object from the Sun at a given instant

a=16.8 A.U. c=16 A.U.

"r" at perihelion = a-c "r" at aphelion = a + c

I see that you have quoted units in terms of years and astronomical units. Did you convert these units to seconds and meters, respectively?

As a reference point for your answers, know that the Earth moves through space in its orbit about the sun around 30 km/s, which is quite fast relative to what we are accustomed to in our daily experiences living on earth.

Maybe this will add another equation for a simultaneous solution? Conservation of angular momentum. Perihelion and aphelion are the two points where the radius vector from the sun to the comet is perpendicular to the tangential velocity of the comet, so the sin theta drops out of the expression for angular momentum and it's just mvr. Then mass cancels out, so v_perihelion r_perihelion = v_aphelion r_aphelion.

## What is the speed of Halley's Comet at aphelion?

The speed of Halley's Comet at aphelion, which is the farthest point in its orbit from the sun, can vary depending on its position and the gravitational pull of other celestial bodies. However, on average, it travels at a speed of about 70,000 miles per hour.

## How is the speed of Halley's Comet at aphelion calculated?

The speed of Halley's Comet at aphelion is calculated using the formula for orbital speed, which takes into account the distance from the sun and the mass of the sun. This formula is v = √(GM/R), where G is the gravitational constant, M is the mass of the sun, and R is the distance from the sun to the comet.

## What is the speed of Halley's Comet at perihelion?

The speed of Halley's Comet at perihelion, which is the closest point in its orbit to the sun, can also vary but is generally much faster than at aphelion. On average, it travels at a speed of about 157,000 miles per hour.

## How does the speed of Halley's Comet at perihelion compare to other objects in our solar system?

The speed of Halley's Comet at perihelion is quite fast compared to other objects in our solar system. For example, Earth travels around the sun at a speed of about 67,000 miles per hour at its closest point, while the fastest known object in our solar system, the Parker Solar Probe, travels at a speed of about 430,000 miles per hour.

## Does the speed of Halley's Comet change over time?

Yes, the speed of Halley's Comet can vary over time due to the changing gravitational forces and other factors in the solar system. In fact, its speed can change significantly each time it completes an orbit around the sun, which takes about 75-76 years.

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