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We now offer the Cool It! card game in our Science Store. Cool It! is the new card game from UCS that teaches kids about the choices we have when it comes to climate change.

# Orbital Data for the Planets & Dwarf Planets

Planet Semimajor
Axis
(AU)
Orbital
Period
(yr)
Orbital
Speed
(km/s)
Orbital
Eccentricity
(e)
Inclination
of Orbit
to Ecliptic
(°)
Rotation
Period
(days)
Inclination
of Equator
to Orbit
(°)
Mercury 0.3871 0.2408 47.9 0.206 7.00 58.65 0
Venus 0.7233 0.6152 35.0 0.007 3.39 -243.01* 177.3
Earth 1.000 1 29.8 0.017 0.00 0.997 23.4
Mars 1.5273 1.8809 24.1 0.093 1.85 1.026 25.2
Jupiter 5.2028 11.862 13.1 0.048 1.31 0.410 3.1
Saturn 9.5388 29.458 9.6 0.056 2.49 0.426 26.7
Uranus 19.1914 84.01 6.8 0.046 0.77 -0.746* 97.9
Neptune 30.0611 164.79 5.4 0.010 1.77 0.718 29.6

### Dwarf Planets

Ceres 2.76596 4.599 17.882 0.07976 10.587 0.378 ~3
Pluto 39.5294 248.54 4.7 0.248 17.15 -6.4* 122.5
Haumea 43.335 285.4 4.484 0.18874 28.19 0.163 ?
Makemake 45.791 309.88 4.419 0.159 28.96 ? ?
Eris 67.6681 557 3.436 0.44177 44.187 > 8 hrs ? ?

* Negative values of rotation period indicate that the planet rotates in the direction opposite to that in which it orbits the Sun. This is called retrograde rotation.

The semimajor axis (the average distance to the Sun) is given in units of the Earth's average distance to the Sun, which is called an AU. For example, Neptune is 30 times more distant from the Sun than the Earth, on average. Orbital periods are also given in units of the Earth's orbital period, which is a year.

The eccentricity (e) is a number which measures how elliptical orbits are. If e = 0, the orbit is a circle. Most of the planets have eccentricities close to 0, so they must have orbits which are nearly circular.

#### Shop Windows to the Universe Science Store!

The Summer 2010 issue of The Earth Scientist, available in our online store, includes articles on rivers and snow, classroom planetariums, satellites and oceanography, hands-on astronomy, and global warming.

## Traveling Nitrogen Classroom Activity Kit

Check out our online store - minerals, fossils, books, activities, jewelry, and household items!...more

## Eccentricity of an Orbit

Most objects in orbits move along an elliptical path. An ellipse is a shape that can be thought of as a "stretched out" circle or an oval. An ellipse can be very long and thin, or it can be quite...more

## Dwarf Planets

In 2006 the International Astronomical Union (IAU) approved a new classification scheme for planets and smaller objects in our Solar System. Their scheme includes three classes of objects: "small solar...more

## Pluto

Pluto is a frigid ball of ice and rock that orbits far from the Sun on the frozen fringes of our Solar System. Considered a planet, though a rather odd one, from its discovery in 1930 until 2006, it was...more

## Makemake: a Dwarf Planet

Makemake is a dwarf planet in our Solar System. Makemake was discovered on March 31, 2005 by a team of astronomers led by Mike Brown of the California Institute of Technology. The International Astronomical...more

## Eris - a dwarf planet

Eris is a dwarf planet that was discovered in 2005. Eris is a trans-Neptunian object (TNO) that orbits the Sun on the frozen fringes of our Solar System beyond the Kuiper Belt. Eris takes 557 years to...more

## Elliptical Orbits

When one object is in orbit around another object, the orbit is usually an elliptical orbit. For example, all of the planets in our Solar System move around the Sun in elliptical orbits. An ellipse is...more

## Kepler's Second Law: The Speeds of Planets

Kepler's second law he again discovered by trial and error. After some experimentation, Kepler realized that the line connecting the planet and the Sun sweeps out equal area in equal time. Look at the...more

Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part is sponsored in part through grants from federal agencies (NASA and NOAA), and partnerships with affiliated organizations, including the American Geophysical Union, the Howard Hughes Medical Institute, the Earth System Information Partnership, the American Meteorological Society, the National Center for Science Education, and TERC. The American Geophysical Union and the American Geosciences Institute are Windows to the Universe Founding Partners. NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. Contact NESTA for more information.