THIS WEEK

12 | NewScientist | 31 July 2010

BLACK holes do not have a reputation for giving up their secrets, but they could prove instrumental in uncovering exotic particles that are difficult to detect on Earth.

If conditions are right, a particle scattering from a spinning black hole will trigger the formation of a new particle. This also causes the black hole to lose a little angular momentum, an effect known as “superradiance”.

Asimina Arvanitaki of the University of California, Berkeley,

and colleagues say this loss of angular momentum could be exploited in the hunt for hypothetical particles called axions, which could constitute the invisible cold dark matter that appears to hold galaxies together.

According to the team’s calculations, a single axion emitted by a spinning black hole could trigger the emission of more axions to form a cloud orbiting the black hole. The creation of each axion would draw rotational energy away from the hole. The cloud eventually gets so dense that some of it will collapse and fall into the hole while the rest is flung outwards and may escape the black hole’s gravitational field altogether.

The entire process would then start anew, with the black hole spinning more slowly than before. “It basically continues until the black hole loses all of its spin,” says co-author Sergei Dubovsky of Stanford University in California. The efficiency of the effect depends on the mass of a black hole, so the signature of the axions would therefore be a lack of fast-spinning black holes of a certain mass (Physical Review D, vol 81, p 123530). The particles could also reveal their

presence in bursts of gravitational waves radiated when their clouds are torn apart around the black hole or when particles move from one axion cloud to another.

“It’s surprising you can learn about such a small, light particle by looking at a big, complicated, macroscopic object in the sky,” says Andrew Strominger of Harvard University.

Axion particles will be difficult to create in the laboratory. “We’re running into a roadblock where we can’t build accelerators much bigger than the Large Hadron Collider,” says Strominger. “This kind of observation is a very novel way of connecting the large and the small.” Rachel Courtland n

“The emission of axions basically continues until the black hole loses all of its spin”

InsIghTRegulation could save personal genome scanning, not kill itARE we witnessing the beginning of the end of “personal genomics”? After a bruising hearing in the US Congress last week, and with the Food and Drug Administration flexing its regulatory muscles, that is what some commentators predict.

“There’s no question that the sheer scale and ferocity of this combined inquisition from the FDA and Congress will forever change the face of the personal genomics landscape,” wrote Daniel MacArthur in his Genetic Future blog, predicting “excessive, innovation-crushing regulation”.

But this doesn’t have to be the end of the industry. If it embraces sensible regulation, then it has the chance to shift personal genomics from a minority recreational pursuit to the heart of clinical medicine. We all stand to benefit from such a shift, by being prescribed drugs that work better for our particular genetic make-up, for example.

The star turn at last week’s congressional hearing was a report from the US Government Accountability Office (GAO) in which investigators recounted their experience of submitting samples for DNA testing to the four leading personal genomics

companies – 23andMe, DeCode Genetics, Navigenics and Pathway Genomics. Like others who have had their genomes scanned by different firms, the GAO investigators obtained varying predictions of their risks of developing common diseases.

This is not surprising, given that the companies use different combinations of genetic markers and different

algorithms to make predictions from these markers. More damning was a compilation of the conversations between undercover GAO investigators and representatives of genetic testing firms, including two of the personal genomics companies. Congress heard evidence that a Navigenics sales rep offered ill-informed advice on the genetics of breast cancer. And while New Scientist

warned last year of the potential for genome scans to be abused by people submitting samples from others obtained without their consent, Congress heard that one of Pathway’s sales team actually encouraged someone to send in a sample from her fiancé for testing for disease risks without his knowledge.

Some form of regulation is clearly needed. If it is not too heavy-handed, the FDA’s involvement could help move the industry into the mainstream. Genome scans could be useful in predicting a person’s response to commonly used drugs, helping to determine, for example, the optimum dose they should receive. If so, then FDA involvement will be crucial as drug labels will need to indicate how prescriptions should be modified in the light of genetic information.

The future for the personal genomics industry may lie in working with doctors and health insurers to test patients and help improve clinical practice. Navigenics is already working primarily through doctors. Given the limited number of people interested in having their genomes scanned for curiosity’s sake – just a few tens of thousands are thought to have purchased scans so far – simple economics may send others down the same path. Peter Aldhous n

Your personal genomics tubes are ready for your sample now

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Spinning black holes could hint at exotic matter

100731_N_p12.indd 12 27/7/10 16:59:15