Double-Radio Sources,quasars,and BL Lacertae Objects Are Now Considered to Be

question 153

Multiple Choice

Double-radio sources,quasars,and BL Lacertae objects are now considered to be the same basic type of object-an accretion disk producing two oppositely directed jets-but they appear to us to be very different because:

• A) the relativistic particles ejected in the double jets are different in each case: electrons in double-radio sources, protons in quasars, and quarks in BL Lacertae objects.
• B) they are at different distances from Earth, so we see more detail and different properties in those that are closer to Earth.
• C) they are of different ages.
• D) we view them at different angles to the line of the double jets. Face-on to the accretion disk the source will look like a BL Lacertae object, edge-on as double-radio sources, and between these positions a quasar.

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