Cosmic Duo Spins Matter From Light

Nov. 28, 2006 — Astronomers have found a gigantic cosmic "Rumpelstiltskin" that is spinning light into matter and giving off lighthouse-like pulses of gamma rays.

The bizarre duo responsible for this miraculous feat of physics is a giant blue star and either a black hole or a rapidly spinning neutron star.

Together, the pair is dubbed LS 5039. The blue star is about 20 times the mass of our sun and is in a very close four-day orbital dance with its unseen compact companion.

The two are separated by a distance that ranges from about 20 to 40 million miles — just a fraction of the distance between Earth and the Sun.

The smaller companion (either a black hole or neutron star) had been spotted previously by radio and X-ray telescopes as it spews out jets of near-light-speed particles from its poles.

"It could also be a rapidly rotating, magnetized neutron star like the Crab Pulsar," said Mathieu de Naurois, of the Laboratoire de Physique Nucleaire des Hautes Energies in Paris, France.

The jetting of near-light-speed particles is what creates gamma rays — the most energetic kind of light there is — as the emitted particles slam into each other.

De Naurois is part of the international High Energy Stereoscopic System team which detected LS 5039’s curious telltale gamma ray pattern using a specialized telescope array in Namibia. They reported their discovery in the latest issue of the journal Astronomy & Astrophysics.

"There are several tens of similar systems in the Milky Way detected primarily (in) X-rays," said Demo Kazanas an astrophysicist at NASA’s Goddard Space Flight Center. "This is important because it is detected at photon energies a billion times larger than X-rays. It is also important because it is the first such binary system which shows modulation at these high energies."

It's that modulation, or variation, of the most powerful sort of light in the universe which signals that matter is being made out of light.

"We’re talking about light that’s a trillion times more powerful than the light we see with our eyes," said cosmic gamma ray researcher Dave Thompson, also of NASA/Goddard.

This extremely high energy enables gamma ray photons to do something that lower energy light photons can’t —  invoke Einstein’s famous equation, E = mc2, and convert light (the "E" part of the equation) into matter (the "m" term).

This happens when the gamma ray photons created by the jets slam into the photons from the blue star. Together they have enough energy to generate matter. The collisions effectively absorb the gamma rays by converting them into matter.

"This is something that can only happen with gamma rays," said Thompson. No other light has enough energy to create matter, and therefore be absorbed in this way.

This gamma-ray eating process makes the brightness of the gamma rays from the jets vary in a regular pattern over the four-day orbits of the two bodies.

When, from our view on Earth, the compact companion is buried deep in the light of the large blue star or on the far side of that star, the gamma rays from the jets are gobbled up by the "fog" of light and the matter-making collisions around the big star.

But when the black hole is on the near side of the star to Earth, we are peering through less fog and can detect some of the gamma rays that escape from the system. This creates the lighthouse-like pulsing.

Because LS 5039 is the clearest case of this gamma-ray absorption, scientists hope it will serve as a small-scale model of the gamma ray signals from gigantic quasars.

The light-spinning, "Rumpelstiltskin" duo may manage an impressive feat, but quasars, which are gamma-ray emitting mega-black holes, with the mass of billions of stars at the centers of galaxies, are in another league, altogether.