An international team of astronomers, including a researcher from Curtin University, has answered a long standing question about the enigmatic jets emitted by black holes, in findings published recently in prestigious journal Nature.<\/p>\n
Jets are narrow beams of matter spat out at high speed from near a central object, like a black hole.<\/p>\n
The team studied the radio waves and X-rays emitted by a small black hole a few times the mass of the Sun. The black hole in question was known to be active, but the team\u2019s radio observations did not show any jets, and the X-ray spectrum didn\u2019t reveal anything unusual.<\/p>\n
However, a few weeks later, the team took another look and this time saw radio emissions corresponding to the sudden appearance of these jets, and even more interestingly, lines had appeared in the X-ray spectrum \u2013 the tell-tale signature of ordinary atoms \u2013 around the black hole.<\/p>\n
\u201cIntriguingly, we found the lines were not where they should be, but rather were shifted significantly,\u201d Dr James Miller Jones from the Curtin University node of the International Centre for Radio Astronomy Research (ICRAR), who led the radio observations, said.<\/p>\n
The same effect occurs when a siren from a vehicle changes pitch as it moves towards or away from us, as the sound wave is shortened or lengthened by the movement.<\/p>\n
\u201cIt led us to conclude the particles were being accelerated to fast speeds in the jets, one directed towards Earth, and the other one in the opposite direction,\u201d team member Dr Simone Migliari from the University of Barcelona said.<\/p>\n
Dr Miller-Jones said this was the first strong evidence of such particles in jets from a typical small black hole.<\/p>\n
\u201cUntil now, we weren\u2019t sure what they are made of, or what powers them,\u201d European Southern Observatory astronomer Dr Mar\u00eda D\u00edaz Trigo, lead author of the study, said.<\/p>\n
\u201cWe\u2019ve known for a long time that jets contain electrons, but haven\u2019t got an overall negative charge, so there must be something positively charged in them too,\u201d Dr Miller Jones said.<\/p>\n
\u201cUntil now it wasn\u2019t clear whether the positive charge came from positrons, the antimatter \u2018opposite\u2019 of electrons, or positively charged atoms. Since our results found nickel and iron in these jets, we now know ordinary matter must be providing the positive charge.\u201d<\/p>\n
Positively charged atoms are much heavier than the positrons astronomers thought might make up the jets, and therefore the jets can carry away far more energy from the black hole than previously confirmed.<\/p>\n
What\u2019s more, astronomers aren\u2019t sure whether the jets are powered by the spin of the rotating black hole itself, or whether they are instead launched directly from the disk of matter that surrounds the black hole.<\/p>\n
\u201cOur results suggest it\u2019s more likely the disk is responsible for channelling the matter into the jets, and we are planning further observations to try and confirm this,\u201d Dr Miller-Jones said.<\/p>\n
Using the X-ray data, the team also determined the jets were moving at two-thirds of the speed of light, or 198,000 km\/s, the most accurate determination to date of the jet speed from a run-of-the-mill black hole a few times the mass of the Sun.<\/p>\n
For their observations, the team used the European Space Agency\u2019s XMM-Newton satellite to observe X-ray emission from the black hole, as well as CSIRO\u2019s Australia Telescope Compact Array for the radio observations.<\/p>\n
The paper, Baryons in the relativistic jets of the stellar-mass back holes candidate 4U1630-47 can be found at www.nature.com, published 13\/11\/2013. DOI: 10.1038\/nature12672<\/p>\n","protected":false},"excerpt":{"rendered":"
An international team of astronomers, including a researcher from Curtin University, has answered a long standing question about the enigmatic jets emitted by black holes, in findings published recently in prestigious journal Nature.<\/p>\n","protected":false},"author":4275,"featured_media":9816,"template":"","meta":{"_acf_changed":false,"_oasis_is_in_workflow":0,"_oasis_original":0,"_oasis_task_priority":"","_relevanssi_hide_post":"","_relevanssi_hide_content":"","_relevanssi_pin_for_all":"","_relevanssi_pin_keywords":"","_relevanssi_unpin_keywords":"","_relevanssi_related_keywords":"","_relevanssi_related_include_ids":"","_relevanssi_related_exclude_ids":"","_relevanssi_related_no_append":"","_relevanssi_related_not_related":"","_relevanssi_related_posts":"","_relevanssi_noindex_reason":"","wds_primary_category":0,"wds_primary_research-areas":0,"footnotes":""},"categories":[4],"tags":[],"research-areas":[],"class_list":["post-18213","media-release","type-media-release","status-publish","has-post-thumbnail","hentry","category-research"],"acf":{"post_options":{"":null,"additional_content":{"title":"Media Contact","content":"
Dr James Miller-Jones, ICRAR, Curtin University
\nTel: 08 9266 9141
\nMobile: 0488 484 825
\nEmail:\u00a0james.miller-jones@icrar.org<\/a><\/p>\n