THE SOUTHWORTH PLANETARIUM
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Founded January 1970
Julian Date: 24592546.18
2020-2021: LXXXVIII
THE DAILY ASTRONOMER
Thursday, February 11, 2021
Exploratorium XXI: The Cosmic Hand
*Location*
17,000 light years away
*Time*
17,000 years ago
Please....take another quick look.....
Did you see the "Cosmic Hand" also known as the "Hand of God.?"
Absolutely astounding, isn't it? Just when you thought that we couldn't
do anything else to antagonize the University's council of the white, we
decided to devote an entire DA to this most remarkable celestial object.
We'll resist the temptation to assign a metaphysical significance to this
discovery and stick solely to astronomy.
The "Hand of God" is only a quaint sobriquet designed to make the
secularists seethe. The actual name is PSR B1509-58, a magnificent "pulsar
wind nebula" located more than 17,000 light years away in the southern
constellation Circinus.* Actually, PSR B1509-58 is just one object
within that nebula and , ironically, isn't visible to us. Pulsars form
after highly massive stars go supernova. Stars that are between 4 - 8
times more massive than the Sun produce pulsars after these explosions.
(More massive stars create black holes.) This pulsar is actually a rapidly
spinning neutron star, so named as its has two high energy radio lobes that
appear to emit pulses when they sweep across our view. Compared to
yesterday's millisecond pulsar that completes about 365 rotations per
second, PSR B1509-58 is comparatively lazy, for it spins only seven times
a second.
The pulsar is embedded within that "blue" glowing core deep within the
nebula. The material we observe within this region consists of gases the
original supernova violently expelled about 17000 years ago.** As the
nebula spins, it pushes high energy rays into the surrounding magnetic
field, resulting in the emission of x-rays. The image you saw on the link
was not optical, but was instead captured by the Nuclear Spectroscopic
Telescope Array (NuSTAR), an orbiting observatory that observes such
objects in the X-ray EM spectrum. PSR B1509-58 was actually first
discovered by the Chandra X-Ray Observatory in 2009.
In this image we observe not only the cloud's gradual but inexorable
expansion related to the supernova explosion. We also see how the cloud
reacts to and is energized by the pulsar shrouded within it. The pulsar
'heats' the nebula, inducing the energy emission. That much seems clear.
What remains unresolved is the "hand." The nebula does seem to resemble
an outstretched hand reaching from the pulsar toward an entirely separate
reddish cloud named RCW 89. The fingers, incidentally, extend through 50
light years of space.
The question that remains unanswered pertains to these fingers. Has the
nebula actually assumed a shape reminiscent of a human hand; or is it
merely an optical illusion? Granted, addressing this issue will do
little to resolve the controversy about its age (see second footnote) or
the actual interplay of energy and matter within the cloud. What we will
know, however, is whether or not an invisible hand large enough to
encompass hundreds of star systems actually floats out there in the void.
Tell us that's an issue not worth exploring.
*I think this is the very first time we've happened upon this
constellation. Invented by French astronomer Nicolas Louis de Lacaille
(1713-1762), Circinus represents a compass well below our sight line. (One
would have to venture below the Tropic of Cancer to see it.) This faint
and small constellation resembles a thin triangle quite close to Alpha
Centauri, the closest star to our solar system.
**Just an important side note: astronomers calculate a pulsar's age
through the "spin down" rate. A pulsar's spin rate is greatest just after
its formation, but then through time the rotation rate slows. This spin
rate decrease varies with pulsars relative to the brake function. Based
on the pulsar's rotation rate and mass, the supernova is believed to have
occurred 1700 years ago. However, some researchers insist that the
supernova nebula expansion rate and current size suggests the event
occurred much earlier. The discrepancy has not yet been resolved, but we
thought we'd mention it so as to point out that the 1700 year figure is not
certain.
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