Since December 2007, over 50 Australian schools including
interstate schools and overseas institutions have used the Parkes
Radio Telescope to collect data on pulsars for analysis. Students
have controlled the telescope via the internet to observe several
pulsars. Fact # 1 Frequently Asked Questions answered at:
http://outreach.atnf.csiro.au/education/pulseatparkes/teachers/teachers.html
Slide 5
What is a Pulsar? In 1934 Walter Baade and Fritz Zwicky
proposed the existence of a new type of star -neutron star In 1967
Jocelyn Bell discovered a pulsar(media reported the discovery as
little green men) Properties density of 10 17 Kg/m -3 Thimbleful
has a mass of 10 9 tonnes Rotates once to several hundred times per
second Acceleration due to gravity at surface of pulsar is ~ 10 12
m.s -2 cf 10 m.s -2 at Earths Escape velocity ~ 50% of the speed of
light.
Slide 6
A pulsar is a rapidly rotating neutron star. Jets of
electromagnetic radiation stream from the pulsar and are observed
as pulses of radio waves because of this rotation. The Parkes Radio
telescope has been instrumental in discovering nearly two-thirds of
all known pulsars. Fact # 4
Slide 7
Typical pulsar diameters are approximately 20 to 25 kilometres
with a mass roughly 1.4 times the mass of the Sun. The mean density
is approximately 6.7 x 10 14 grams/cm 3 which is equivalent to a
single sugar cube weighing as much as all of humanity
(approximately the weight of 7 billion people). Fact # 5
Slide 8
The 64 metre Parkes radio telescope was built in 1961 and has
operated continuously for over 50 years. It is a world class
instrument at the forefront of radio astronomy due to continual
upgrades. It is now 10,000 times more sensitive than when it was
first built. Fact # 6
Slide 9
PSR B 1919+21 Pulsating source of radio Location of the pulsar
(right ascension, declination) The complete pulsar catalogue can be
found at: http://www.atnf.csiro.au/research/pulsar/psrcat/ The
pulsar catalogue has over 1,900 pulsars and can be accessed
electronically at the link below. Some pulsars have two different
designations (B and J). The designation B indicates 1950
coordinates which were used prior to 1993, whereas the J
designation is now used in 2000 coordinates. The J designation also
uses a more accurate declination. The example below includes both
designations for the same pulsar. Before 1993 PSR J 1919+2153 After
1993 Fact # 7
Slide 10
Fact # 8 A pulsar map was included on the Pioneer 10 and 11
probes launched in 1972 and 1973 respectively. They show the
position of the Sun, relative to 14 pulsars, so that our position
in space can be calculated by extra-terrestrials that encounter the
probes.
Slide 11
Fact # 9 The line graph indicates the number of known pulsars
from 1967 to 2011. Discovery of the first pulsar PSR B 1919+21 in
July 1967 by Jocelyn Bell.
Slide 12
The nearest millisecond pulsar (MSP)discovered in 1992 during
the Parkes 70 cm survey is approximately 510 light years away. It
is known as PSR J0437-4715 and it has a period of 5.757451831072007
0.000000000000008 milliseconds It is the most stable natural clock
in the whole universe. Fact # 10
Slide 13
The Parkes radio telescope is so sensitive that a mobile phone
call from Pluto would be considered a really strong signal. Fact #
12
Slide 14
Australian and U.S. astronomers used CSIRO's Parkes radio
telescope to measure the distortion of space-time around the pulsar
J0437-4715 and its companion white dwarf. In this pulsar system,
the pulsar's radio waves travel through the curved space- time
around its white dwarf companion, and arrive on Earth a little
later than if they had travelled through undistorted space-time.
The effect, called the Shapiro delay, was first proposed in 1964 by
Irwin I. Shapiro. The data clearly showed the predicted delay,
making this the first test of general relativity in which the
geometry of the system has been used to predict a relativistic
effect. This provided another confirmation of Einstein's general
theory of relativity. Fact # 14
Slide 15
75% of all known pulsars have a period of less than a second.
In 1999, Astronomers using the Parkes radio telescope found the
pulsar J 2144-3933. This pulsar, which spins only once every eight
seconds, defied existing theories on the upper limit for pulsar
periods. Fact # 15
Slide 16
Astronomers using the Parkes radio telescope in conjunction
with the 76-metre Lovell Telescope in England have discovered a
possible diamond planet orbiting a newly detected pulsar, PSR
J1719-1438 located 4,000 light years away. Fact # 16
Slide 17
Fact # 17
Slide 18
The first confirmed exoplanets discovered several years before
the first detections of exoplanets around normal solar-like stars,
were found in orbit around a millisecond pulsar, PSR B1257+12.
These planets remained for many years the only Earth-mass objects
known outside our solar system. And one of them comparable to that
of our Moon in mass, is still today the smallest-mass object known
beyond the solar system. Fact # 18
Slide 19
PSR J1023+0038, is the fastest known millisecond pulsar. It
lies 4,000 light years away in the constellation Sextants and spins
at a rate of 592 times a second. After discovery in 2007, the
Parkes radio telescope was used to get the first full orbit
observations. Astronomers have long thought that millisecond
pulsars are ordinary pulsars spun up with the help of an orbiting
companion star. The companion dumps matter onto the pulsar, causing
it to spin far faster. Fact # 19
Slide 20
The magnetic axis of a pulsar aligned with the radio beam is
usually not aligned with the rotation axis. Fact # 20
Slide 21
The hard disk drive of a computer rotates at high speed,
commonly 7,200 revolutions per minute or 120 revolutions per
second. The time to complete one revolution is 8.33 milliseconds.
This is similar to the pulsar J1518+0204 which has a period of 7.9
milliseconds and hence rotates slightly quicker at 127 revolutions
per second. period = 8.33 milliseconds period = 7.9 milliseconds
Fact # 21
Slide 22
Millisecond pulsars (MSPs) have rotational periods in the range
from 1 to 30 milliseconds. They have been detected in radio, x-ray
and gamma ray portions of the electromagnetic spectrum. One theory
about their formation is that they begin life as longer period
pulsars but are spun up or "recycled" through accretion of a
companion star. The transfer of angular momentum from the accretion
of the companion can theoretically increase the rotation rate of
the pulsar to hundreds of times a second, as is observed in
millisecond pulsars. Fact # 22
Slide 23
Two main types of pulsars Normal pulsars Are quite young, 10 7
years Periods from 0.03 10 seconds Mostly single (non-binary)
Formed in supernova Magnetic field strength approximately 10 12
gauss Millisecond pulsars Are very old, 10 9 years Periods from 1
30 milliseconds Mostly binary Accretion from companion spins up the
neutron star to a millisecond pulsar Magnetic field strength
between 10 8 -10 9 gauss Fact # 23
Slide 24
Fact # 25 The first binary pulsar was discovered by the Parkes
radio telescope in 2003. One of the pulsars has a period of 22
milliseconds and the other pulsar has a period of 2.7 seconds. The
orbital period for the binary pulsar system is 2.4 hours. The is a
highly relativistic binary system which is a laboratory for testing
Einsteins general theory of relativity.
