Astronomers Seek Help From Public To Measure True Size Of Solar System
February 2, 2012

Astronomers Seek Help From Public To Measure True Size Of Solar System

Scientists are seeking help from amateur astronomers in a global initiative dubbed the Eros Parallax Project, which aims to calculate the true scale of the solar system by measuring the orbit of a nearby asteroid.

The 20-mile-wide Eros 433 is one of the largest near-Earth asteroids, with a highly elliptical orbit that brings it within 20 million miles of Earth every two years or so.

Eros is currently making its closest approach to Earth since 1975, coming within 16.6 million miles  – astronomically close, although not enough to risk any cataclysmic consequences.

A similar close pass of the asteroid in 1931 allowed scientists to refine their calculations of the true scale of the solar system by estimating the Earth-Sun distance (the astronomical unit).

This was the last significant refinement in the estimate of the scale of the solar system until interplanetary radar began obtaining direct distance measurements during the 1960s.

Members of the public that wish to participate in the Eros Parallax Project, which runs January 28th through February 3rd, need only a digital camera that can attach to a telescope or a long telephoto lens.

Volunteers can provide valuable data by taking pictures of Eros at specified times, analyzing the pictures using free online software, and then submitting the retrieved data to the project´s website.

The data will help scientists determine the size of Eros's orbit in actual miles, not just the orbit's size relative to Earth's orbit, which is all that classical position observations yield.

Once the true orbit size is known, Kepler's laws of planetary motion can be applied to produce the absolute -- not relative – sizes of all the other orbits in the solar system.   This limitation has been a central problem in astronomy for centuries.

Data and images obtained during the project will also be made available for classrooms to process themselves if they wish.

The Eros project will also help prepare students for the even rarer event coming this June: the transit of Venus, for which Astronomers Without Borders is organizing a similar solar-system measurement initiative.

Detailed instructions for participating in the Eros Parallax Project can be viewed at the Transit of Venus website.