Credit: CSIRO
SYDNEY: A new technique for calculating the weight of unknown planets has been invented by an international team of astronomers.
Based on pulsar signals, the technique does not require a planet to be seen to be weighed, and so has further implications than simply confirming known weights of planets in the Solar System.
“It works like a kind of cosmic GPS,” said Matthew Bailes of the Swinburne University of Technology, one of the international team who pioneered this new weighing technique. Not only can it be used to study known planets, he said, but it can also be used to find new ones.
The weight of gravity
Traditionally, astronomers have weighed planets by measuring the orbits of their moons or of spacecraft flying past them – because mass creates gravity, and a planet’s gravitational pull determines the orbit of anything that goes around it, both in duration and size.
This new method is based on corrections astronomers make to signals from pulsars, the small spinning stars that deliver regular ‘blips’ of radio waves.
Like a GPS, which uses the time-delay between satellites to determines position, this method uses the time-delay between pulsars to determine the weight of planets and planetary systems (planets and their moons and rings), said Bailes.
Discovering unknown planets
“In the short term, spacecraft will continue to make the most accurate measurements for individual planets,” said George Hobbs of the CSIRO, another member of the team, in a statement.
“But the pulsar technique will be the best for planets not being visited by spacecraft, and for measuring the combined masses of planets and their moons.”
“This is first time anyone has weighed entire planetary systems,” said team leader David Champion of the Max Planck Institute for Radio Astronomy in Germany.
“And we’ve provided an independent check on previous results, which is great for planetary science.”
Weighing planets not yet known
Although Bailes is encouraged by the results of the method, he predicts the real excitement lays in the future, as pulsar timing continues to improve, and the possibility exists that the technique could discover new planets or other bodies in the Solar System.
