PHYS 182 Lecture Notes - Lecture 5: Canadian Hydrogen Intensity Mapping Experiment, Radiance, Fast Radio Burst
PHYS182: Our Evolving Universe
2017-09-19 LEC 5: Pulsars, Fast Radio Bursts, and Chime
Guest Lecturer: Emmanuel Fonseca
Chime: Canada’s hydrogen intensity mapping experiment
• Built in the Okanagan
• Cosmology experiment built to study dark energy, but turns out to be good to study pulsars and
FRBs
Fast Radio Bursts: FRBs
Astronomy and the EM Spectrum
• Astronomy is all about collecting electromagnetic radiation (EM), of which there is a spectrum
o Higher energy: UV, X-ray, gamma ray
o Lower energy: radio, microwave, infrared
• Can make different images of the Crab nebula using different parts of the spectrum
o Remnants of a star explosion
Radio Astronomy
• Radio astronomy is the study of radio radiation from celestial objects and regions
• Long wavelengths (~cm), low frequencies (~MHz)
• Biggest telescope in the world (Penticton, BC)
• Can do imaging and time-domain science (i.e. looking for signals in outer space)
o Time domain = pulses, bursts, bleeps…etc.
Radio Pulsars
• Pulsars are rotating neutron stars that emit beamed radiation
o Neutron star: weighs a bit more than the sun, but is about the size of a city
o Think of as “cosmic lighthouses”
o Pulsars are as close as you can get to a black hole
• ~2,600 pulsars currently known
o Estimated ~100k in our galaxy
• We don’t see the neutron star, we see pulses of light (think lighthouse) and infer that they are
there
o Pulsar rotation is as stable as atomic clocks, making them useful devices for studying
other phenomena
o Rotation is because they have intense magnetic fields, and the light shines out of the
poles of the magnetic field
o We see them as radio pulses
• Pulsars were discovered in 1967 by Dame Jocelyn Bell Burnell
Why Pulsars are Cool
• We can probe open questions in fundamental physics, especially in nuclear physics and
gravitation
o General relativity: black holes, time warps, gravity (Einstein)
o It also predicts the existence of gravitational radiation
• Example: the first non-controversial detection of gravitational waves came from pulsars
• Second Nobel prize for pulsar science given in 1992 for this measurement
• A binary system was found of 2 neutron stars
o Energy is removed from the system and the orbit shrinks over time
Document Summary
2017-09-19 lec 5: pulsars, fast radio bursts, and chime. Chime: canada"s hydrogen intensity mapping experiment: built in the okanagan, cosmology experiment built to study dark energy, but turns out to be good to study pulsars and. Why pulsars are cool: we can probe open questions in fundamental physics, especially in nuclear physics and gravitation, general relativity: black holes, time warps, gravity (einstein) If it was not dispersed, the radiation would arrive all at the same time, as opposed to dispersed systematically through time. The frb boon: perytons have distinct properties that can be distinguished from frbs, other telescopes (e. g. arecibo, green bank) detected frbs, also sparsely, consistent with telescope in australia, nearly all frbs have occurred once, except In 2015, mcgill grad student paul scholz found a bunch of bursts with the same large dispersion measure, in the same part of the sky: the dispersion/position parameters were the same as a previously found burst discovered by.
