Image copyright Stephen Johnson Image caption Northern lights are usually seen in northern hemisphere skies and elsewhere only at night. These were photographed in a NASA aircraft last year
Scientists consider searching for life on other planets to be their top priority for human endeavour, followed by living off the ocean.
The findings are published in the Journal of Physics Letters.
Australian Dr Stephen Johnson, from the University of Western Australia, said the increase in star formation over a period of 100,000 years was equivalent to “500 times the yearly growth in the number of stars”.
His research was based on a series of calculations used by the US National Science Foundation, which funded the study.
“The next century will see planetary astronomers search for exoplanets – planets beyond our solar system – with the goal of finding an Earth-like planet that could support life,” said Dr Johnson.
“This objective does not hinge on discoveries of directly observable planets, but rather on the detection of evidence of ‘subpolar’ temperatures – those so cold that liquid water or life as we know it cannot form.”
Playful solar system
By studying a detailed record of the electric activity of dust grains in the night sky at night, Dr Johnson was able to see the activity of millions of stars over a relatively short period of 100,000 years, from 1945 to 1997.
He found that they had, on average, warmed up at the same time, over what is known as a loop, from 0°C at day to -100°C at night, a condition that is believed to be important for the environment of the planets that lie beyond the solar system.
He found that that cooling appeared to be happening at the same time that planets in our own solar system were forming.
Only the two most distant of these planets, Uranus and Neptune, had warmed up over the long period.
Similar activity could be seen in other rocky planets around other stars, including the three innermost planets of our own solar system – Jupiter, Saturn and Uranus.
This pattern suggested that planetary formation was taking place over vast areas.
“We expected to find that similar quantities of dust grains would also form in warm, dim stars,” Dr Johnson said.
“But what surprised us was the amount of dust grains around relatively young stars – that was a surprise.”
Dr Johnson’s work emerged from his previous research into the interaction between the Earth and the Sun, where he showed that water is locked up in ice at night due to an interaction between the layers of ice and the magnetic field of the Sun.
Image copyright Getty Images Image caption Ice comes from the solid layer of water and ice crystals on the surface
He said that a combination of the information about the temperature of the stars at night and the expansion of ice under the Earth’s magnetic field could hold the key to understanding whether planets in the inner solar system could support life.
Stephen Johnson is currently on sabbatical at the University of Michigan.