'Weigh' the planets

Astronomers at the Max Planck Institute for the Astronomical Society in Germany say they have developed a new method for weighing the masses of planets in the solar system, using radio signals from small stars called pulsars.

This is the first time that scientists have weighed the masses of Mercury, Venus, Mars, Jupiter, Saturn, and even their satellites.

Scientists have discovered how to use radio signals from pulsar stars to weight planets.

So far, astronomers have weighed planets by measuring the orbits of the moon or spacecraft flying around them. The mass that creates a planet's gravity determines the trajectory of anything around it: the orbital size and the time it takes to complete a cycle.

The new measurement method is based on refining the signals received from the pulsar, the small stars that make up the constant beating of radio waves.

The mass of the Jupiter system is determined to be 0.0009547921 times the sun, more accurately than measured by the Pioneer and Voyager spacecraft, and is consistent with the Galileo spacecraft.

To do this, astronomers have used the astronomical calendar where all the planets coexist in a given time, combining the measured values. Most of the data was recorded using the CSIRO Parker radio telescope in eastern Australia, the Arecibo telescope in Puerto Rico, and the Effelsberg telescope in Germany.

Although spacecraft measurements will continue to provide accurate data for a short time, the pulsar technique will allow repeated measurements of planets inaccessible to the spacecraft. In the future, new techniques combined with existing data will help to weight the planet's mass more accurately.