In a frenzy of citizen science and rapid astronomical observations, the audience of Stargazing Live on ABC TV has helped identify two new exploding stars — gathering enough data to estimate the age of the universe.
To go with Wednesday night's discovery of a type Ia supernova 1.1 billion light-years away, further observations on Thursday night suggested a second type Ia blast slightly closer, at a distance of 945 million light-years.
And once again the huge Anglo-Australian Telescope (AAT), which towers over the Siding Spring Observatory in the Warrumbungles — currently playing host to Stargazing Live for three nights — swung towards the distant galaxy that had emitted the tell-tale flash.
Sure enough, the rainbow of colours detected from that faraway source by the AAT was exactly what astronomers expect from a type Ia supernova.
In fact, it appears to be fading away already; the explosion itself likely took place several weeks ago — plus the 945 million years it took for the light to reach Earth.
Type Ia explosions are the most precious quarry of the Supernova Sighting project, run by the Australian National University's Skymapper team and hosted by zooniverse.org.
These are the supernovae, sometimes called "standard candles", that allow astronomers to estimate the size of the cosmos and how fast it is expanding. Detecting two within 48 hours is no mean feat.
"We got more than 1.7 million classifications from the viewers of Stargazing Live, which is absolutely phenomenal," said Becky Smethurst of the University of Nottingham, who helped manage the citizen science effort from Siding Spring.
Cosmic calculation
Any type Ia supernova provides scientists with a fresh measure of the speed at which the universe is growing.
This is because they always explode with about the same amount of energy, so how bright they appear in the sky acts as a reliable measure of distance.
Combined with the "redshift" of the dying star's host galaxy — the warping of its light, which tells us how fast it is moving away from us — that puts a figure on cosmic expansion.
If cosmologists know how fast the universe is expanding, they can work backwards to find out how much time has passed since the Big Bang, said Brad Tucker, cosmologist at the Australian National University.
The Stargazing Live effort, which involved at least 6,000 citizen scientists, has added two new data points to the bank of estimates already available.
In a "back-of-the-envelope" calculation, the team has estimated a new age for the universe that includes the two new supernovae.
"A very rough estimate puts the cosmos about 500,000 years older than calculations based on previous data alone," said Chris Lintott, the principal investigator of zooniverse.org and professor of astronomy at Oxford University.
In other words, the cosmos appears to be 13,798,150,576 years old (give or take) instead of 13,797,616,664.
"It's a very rough calculation but it's been great fun to try and pull it off. Two type Ia supernovae in two days: that's a very good week for us!"
