Kepler's new mission: spotting black holes and supernovae

Analysis NASA's precious $530m Kepler space telescope's exoplanet-hunting powers may have been destroyed by the failure of its gyroscopic stabilisers, but it turns out the craft is still capable of functioning as a useful astronomical instrument.

Back in August, the Kepler mission solicited proposals for new science missions that would work with the reduced sensitivity of the instrument, and this week's Kepler conference at the NASA Ames Research Centre in California is the venue for announcing the preferred missions.

This won't seal the future of Kepler, since the recommendations will still have to go back to NASA for funding approval; a decision won't be made public until early 2014. However, it should at least provide some measure of assurance for keen Kepler-watchers that the spacecraft will still be able to deliver useful science.

One of the proposals endorsed by the mission was put up by Dr Brad Tucker, a research astrophysicist who divides his time between the Australian National University and the University of California at Berkeley. He worked with Rob Olling from the University of Maryland, and collaborators from US institutions including Notre Dame, Space Telescope Science Institute, Hawaii, and the Gemini Observatory.

Dr Tucker outlined the proposed new science mission to The Register, explaining that if NASA okays the project, a large chunk of Kepler's future will be helping to unravel the mysteries of black holes and supernovae. Kepler's well-equipped to do that job thanks to its extra-atmospheric location, and its large field of vision.

Rather than the narrow focus of an Earth-bound optical telescope, Dr Tucker explained, Kepler can examine large slabs of the sky, and repeat those observations on cycles as short as every ten minutes. It's rather like watching paint dry: it might seem dull to look at a whole wall, but if you watch the wall long enough, you really will see the paint dry.

“One thing we've already learned is that black holes are much more active than we can see from Earth,” he said. Published observations show that from the ground, we only see large events, and only catch them over periods of years.

With Kepler, Dr Tucker said, it will be possible to see interactions between black holes and much smaller stars than we see from the ground.

“We'll be able to see the moment that a black hole swallows a star, or ejects one. And we can see much smaller features that only last for a few hours – that's something you just can't see from the ground.”

For example, while observations of black holes consuming huge objects – up at the galactic scale – what Kepler should be able to catch is the absorption of stars of much smaller mass - perhaps, hopefully, the same order of mass as the Sun.

Moreover, the characteristics of the “blip” that pops up in Kepler's data should tell us more about the star that's interacting with the black hole – its mass, temperature, and so on.

The other thread to Dr Tucker's proposal is to use Kepler to get much better observations of exploding stars: to see details of their behaviour hidden from ground-based telescopes but visible to Kepler's still-impressive optics.

Such activities, he said, would include watching shock waves travelling through stars before the explosion happens: “we can see the burp before the supernova blows up. For larger stars, there should be faint and subtle events, like very small burps before the big explosion.”

There will also be chances to observe the brief cooling and material ejections that happen in the immediate pre-explosive life of the supernova – and these phenomena, taken together, will help provide a better understanding of “what is physically causing the explosion,” he said.

Here's another example of the kind of phenomena Kepler will still be able to see: the shock waves passing through a star ... just before it goes supernova.

Many of these phenomena have been predicted but not observed – but there's also the likelihood that astronomers will also get to see brand-new phenomena that aren't yet in the science, something that would delight the theorists who get to work out what happened, and try to formulate predictions about the behaviour of future supernovae.

Why hasn't all this been observed before? The short answer is that it has. However, the extreme sensitivity of Kepler in its planet-hunting years was a challenge for supernova-watchers, he explained. The data coming from Kepler was, for his purposes, too good, too detailed, too voluminous to work with easily.

“A reduced sensitivity mission is perfect for our science,” he said.

That, of course, will now be in the lap of the funding gods at NASA. ®