Why Study Pulsars?
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A supernova recorded in 1054 A.D formed the famous Crab Nebula. Spanning nearly 10 light-years across, the nebula's center is home to a pulsar: a rapidly spinning neutron star with the mass of our sun, but only a few kilometers in diameter. Image Credit: NASA, ESA, J. Hester, A. Loll (ASU)
Aaron asks,
Dear Astronomer, What can be learned by analyzing pulsars?
I ask because a friend of mine asked what pulsars are.
I explained, and he then asked, “Why look for them?” I didn’t have a good answer. Help?
Great question Aaron!
Quite often astronomers are asked why they study a particular subject of interest. I’ve been asked a few times why I research variable stars ( more about that some other time ). Some astronomers study specific subjects because they sort of “fell” into that field, while others are passionate about a particular piece of the cosmic puzzle. Quite often astronomers study a subject so that they can add to the body of scientific knowledge, which may allow other scientists to better research their own chosen field.
In the case of Pulsars, let’s take a step back and examine what they are, so we can better understand why they are scientifically important to astronomers…
A diagram of a pulsar showing its rotation axis, its magnetic axis, and its magnetic field. Image Credit: NASA
As stars fuse their hydrogen into helium and “evolve” into later-stage stars, the end result varies, more or less, on their mass. Small stars like our sun will flare into a red giant, and then eventually shrink down to a small white dwarf. Stars a bit larger than our sun can form neutron stars – not too much bigger though, as very massive stars will implode into a black hole.
Interestingly enough, we can thank these supernova explosions for “enriching” the regions of space near them. Most all elements past Iron on the periodic table like Gold, Aluminum, Sodium, and Uranium are formed from supernovae. Without elements like Iron, producing Earth-like planets would be nearly impossible.
At the center of many supernova remnants, like the Crab Nebula, observers can usually detect neutron stars, and in many cases, pulsars.
Pulsars are neutron stars, but not all neutron stars are pulsars. Essentially a rapidly spinning neutron star emits “beams” of high energy radiation. The diagram to the right shows the relationship between a neutron stars rotational axis, and its magnetic field.
The neutron star’s rotation causes the previously mentioned beam of radiation to “sweep” across space. If Earth is in the path of these beams, then we can detect a signal from them, very similar to how ocean-going ships on Earth detect the beam of light from a nearby lighthouse. By analyzing the timing of the pulses, astronomers can determine how fast the neutron star is spinning.
As a sort of cosmic “lighthouse”, pulsars can provide a wealth of information to astronomers. The extreme density of neutron stars (only black holes rival neutron stars in terms of mass/size ratio) combined with their extreme rotational speed help researchers use Einstein’s theory of relativity to better understand time, space, and gravity.
So there you have it. A bit of a recap on pulsars and neutron stars, along with some information on why we study them. Hopefully I’ve been able to shed a little more light on the subject.
If you’d like to learn more about pulsars, visit: http://outreach.atnf.csiro.au/education/everyone/pulsars, or http://imagine.gsfc.nasa.gov/docs/science/know_l2/pulsars.html
Ray Sanders is a Sci-Fi geek, astronomer and blogger. Currently researching variable stars at Arizona State University, he writes for Universe Today, The Planetary Society blog, and his own blog, Dear Astronomer
2012-12-04 08:06:52
Source: http://www.dearastronomer.com/2011/11/10/why-study-pulsars/
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