# How fast does the Earth go at perihelion and aphelion?

* I need to find the approximate speeds of
the earth's orbit at perhilion and aphelion (this year, for
example, if it makes a difference). I have given myself a
crash course in astronomy over the course of the last three
months and command a fair if somewhat pedantic understanding
of the underlying principles. The earth's mean revolutionary
velocity is easily found, but i have not found these precise
figures and am not much of a math whiz. Can you help me?
*

The formula for the velocity of an object at some distance r from the Sun is:

v = sqrt[GM*(2/r-1/a)]

Where G is the universal gravitational constant, M is the mass of the Sun, and a is the planet's semimajor axis.

At perihelion, Earth's distance from the Sun is r=a(1-e) and at aphelion, it's r=a(1+e).

G=6.673*10^{-11} N m^2/kg^2

M=1.989*10^{30} kg

a=1.496*10^{11} m

e=0.017

So plugging in the numbers, the speed at perihelion is 30,300 m/s and at aphelion it's 29,300 m/s.

# Still Curious?

**Get More 'Curious?' with Our New PODCAST:**

- Podcast? Subscribe? Tell me about the Ask an Astronomer Podcast
- Subscribe to our Podcast | Listen to our current Episode
- Cool! But I can't now. Send me a quick reminder now for later.

**Related questions:**

- At what speed does the earth move around the sun?
- How can I find the distance to the Sun on any given day?

**More questions about The Earth:** Previous | Next

# How to ask a question:

If you have a follow-up question concerning the above subject, submit it here. If you have a question about another area of astronomy, find the topic you're interested in from the archive on our site menu, or go here for help.

Main Page | About Us | For Teachers | Astronomy Links | Ask a Question | View a Random Question | Our Podcast

Table 'curious.Referrers' doesn't existTable 'curious.Referrers' doesn't existURL: http://curious.astro.cornell.edu/question.php?number=614

This page has been accessed *38249* times since March 20, 2004.

Last modified: *March 20, 2004 1:02:15 PM*

Ask an Astronomer is hosted by the Astronomy Department at Cornell University and is produced with PHP and MySQL.

**Warning: Your browser is misbehaving! This page
might look ugly.** (Details)