A ‘comet outburst’ lit up the far reaches of space in 20-day explosion

A Nasa satellite has captured the sudden moment ice and dust explodes from a comet into the dark void of space.

The Transiting Exoplanet Survey Satellite (TESS) recorded the spontaneous outburst from comet 46P/Wirtanen as it sprayed debris out into space. Over the course of 20 days, the TESS satellite collected imagery that allowed scientists to piece together a timelapse of the event.

‘TESS spends nearly a month at a time imaging one portion of the sky. With no day or night breaks and no atmospheric interference, we have a very uniform, long-duration set of observations,’ explained Tony Farnham, a research scientist at the University of Maryland’s Department of Astronomy.

‘As comets orbit the Sun, they can pass through TESS’ field of view. Wirtanen was a high priority for us because of its close approach in late 2018, so we decided to use its appearance in the TESS images as a test case to see what we could get out of it.

‘We did so and were very surprised!’

According to the bods at Nasa, comets are known to ‘experience occasional spontaneous outbursts that can significantly, but temporarily increase the comet’s activity.’

The space agency has explained that the reasons for this yet are unknown – but they hope to learn more by studying the celestial bodies as they blaze through space.

‘A number of potential trigger mechanisms have been proposed, including a thermal event, in which a heat wave penetrates into a pocket of highly volatile ices, causing the ice to rapidly vaporize and produce an explosion of activity, and a mechanical event, where a cliff collapses, exposing fresh ice to direct sunlight,’ Nasa wrote in a statement.

‘Thus, studies of the outburst behavior, especially in the early brightening stages that are difficult to capture, can help us understand the physical and thermal properties of the comet.’

In this case, Nasa estimates that about one million kilograms of material was thrown out which could have left a crater on the comet of around 20 meters across.

‘The initial brightening of the outburst occurred in two distinct phases, with an hour-long flash followed by a more gradual second stage that continued to grow brighter for another 8 hours,’ explained Nasa.

‘This second stage was likely caused by the gradual spreading of comet dust from the outburst, which causes the dust cloud to reflect more sunlight overall. After reaching peak brightness, the comet faded gradually over a period of more than two weeks.

‘Because TESS takes detailed, composite images every 30 minutes, the team was able to view each phase in exquisite detail.’

For the rest of us non-specialised space folk, it’s just a bit of a reminder of the colossal processes going on beyond the Earth’s boundaries.