Millimetre emission of microquasar jets detected for the first time
The jets of a Galactic microquasar have been imaged for the first time using wavelengths as short as a millimetre. The striking corkscrew shape of the rotating jets shows up beautifully in the picture taken using the Atacama Large Millimeter/submillimeter Array (ALMA), currently the largest radio telescope in the world. The image verifies a completely independent prediction made on the basic of optical measurements using the Global Jet Watch observatories (multi-longitude small telescopes in schools). This work, published in the Astrophysical Journal Letters, demonstrates for the first time the link between the characteristics of the plasma shortly after launch from near the black hole, and the structures further out on length scales 5000 times larger than our solar system, identifying that the hot plasma propagates ballistically through space.
The microquasar studied is named SS433 and is a black hole orbited by a "normal" companion star. The black hole’s gravity sucks material from the companion’s stellar wind into an accretion disk surrounding the black hole. From this disk are propelled jets of fast protons and electrons outward from its poles at about a quarter of the speed of light. The disk in SS433 wobbles like a child’s spinning top, causing its jets to trace the distinctive corkscrew pattern in the sky every 162 days.
The Global Jet Watch telescopes, controlled from Oxford but distributed around the globe, provide continual, round-the-clock optical spectroscopy and identify the launch vectors and dates of packets of hot plasma. The subsequent ALMA observation date provides the time of flight of these blobs of plasma away from the black hole. ALMA’s exquisite sensitivity to polarised radiation reveals where particle acceleration happens (entirely post-launch) and where the packets of hot plasma expand, collide and gain energy. The Global Jet Watch data allowed the team, led by Professor Katherine Blundell, to predict what the jets ought to look like further away from the black hole if they were still radiant at wavelengths as short as a millimetre.