Using the Sun as a cosmic detector, part II

By Hamish Johnston

Edwin Cartlidge has just written a nice article for us about how the Sun could be used to test alternative theories of gravity. The idea is that gravitational quirks would manifest themselves as deviations in the expected properties of the Sun such as its acoustic modes and neutrino output.

The Sun offers an ideal laboratory for studying gravity because it is extremely massive and so close that we can detect tiny fluctuations in its behaviour. Now, physicists in the US think that the Sun could also be used to detect primordial black holes, which are smallish black holes that may have been formed in the early universe. Such black holes could vary greatly in mass – from that of a small asteroid to several Earth masses – and are expected to endure for at least as long as the age of the universe.

Physicists have yet to detect primordial black holes but Michael Kesden of New York University and Shravan Hanasoge of Princeton University believe that they could be spotted when they travel through the Sun.

The pair calculate that a primordial with a mass of about 10¹⁸ kg and passing through the Sun would induce transient seismic oscillations that could be detected by solar observatories. A simulation of such oscillations is shown above (image courtesy of the American Physical Society).

However, other astronomical measurements have put limits on how likely it is for a primordial black hole to collide with the Sun – and the suggestion is that it’s extremely unlikely.

But there is good news: in the race to find more planets orbiting stars other than the Sun, astronomers have built telescopes that are very good at astroseismology. Kesden and Hanasoge believe that these could be use to survey the heavens for signs of primordial black holes.

The physicists describe their work in Phys. Rev. Lett. 107 111101 and you can read the paper here.