Since the launch of NASA's $690 million Fermi Gamma-ray Space Telescope on June 11th, 2008, the Large Area Telescope (LAT); named after Enrico Fermi, the Italian physicist whose pioneering work in particle physics led him to propose that cosmic particles could be accelerated to high speeds; researchers are now able to peer within the vastly forceful hearts of pulsars.
The Fermi telescope's first mission was to test out its LAT which resulted in its first successfully created an "all sky map in gamma rays" that displayed "the glowing gas of our Milky Way galaxy, blinking spinning stars called pulsars and a flaring galaxy billions of light-years away."
Science Daily explains that: "The gamma-ray-only pulsar lies within a supernova remnant known as CTA 1, which is located about 4,600 light-years away in the constellation Cepheus. Its lighthouse-like beam sweeps Earth's way every 316.86 milliseconds and emits 1,000 times the energy of our sun. The first discovered is estimated to be "a 10,000-year-old stellar corpse sweeps a beam of gamma-rays toward Earth....it is a pulsar and "...is the first one known to "blink" only in gamma rays... A pulsar is a rapidly spinning neutron star, the crushed core left behind when a massive sun explodes. "
Science Daily further explains: "The LAT scans the entire sky every 3 hours and detects photons with energies ranging from 20 million to over 300 billion times the energy of visible light. The instrument sees about one gamma ray each minute from CTA 1. That's enough for scientists to piece together the neutron star's pulsing behavior, its rotation period, and the rate at which it's slowing down."
It is believed that: "A pulsar's beams arise," according to Science Daily, "because neutron stars possess intense magnetic fields and rotate rapidly. Charged particles stream outward from the star's magnetic poles at nearly the speed of light to create the gamma-ray beams the telescope sees. Because the beams are powered by the neutron star's rotation, they gradually slow the pulsar's spin. In the case of CTA 1, the rotation period is increasing by about one second every 87,000 years."
This measurement is also vital to understanding the dynamics of the pulsar's behavior and can be used to estimate the pulsar's age. From the slowing period, researchers have determined that the pulsar is actually powering all the activity in the nebula where it resides," as explained by Science Daily.
"Previously to the Fermi's LAT discovery, scientists have detected some 1,800 pulsars and were only able to detect little wisps of energy from all but a handful of them,... Now, for dozens of pulsars, we're seeing the actual power of these machines," noted Stanford University's pulsar astronomer Roger Romani.
Peter Michelson, also of Stanford University and the principal investigator for the LAT said; "This is the first example of a new class of pulsars that will give us fundamental insights into how stars work."
"This observation shows the power of the LAT,... It is so sensitive that we can now discover new types of objects just by observing their gamma-ray emissions," Michelson added.
NewScientist reports: "NASA's Fermi telescope has found a dozen pulsars that can be detected only by the gamma rays they emit, and not by lower-energy radio waves characteristic of most pulsars."
Romani and fellow scientists who met at the American Astronomical Society in Long Beach, California for the groups annual meeting discussed the LAT Fermi telescope findings. Speaking for his colleges, Romani expressed the groups enthusiasm and reiterated that the Fermi data represent "first wave of such discoveries,... (in) a new era of high-energy pulsar physics."
When first discovered in 1967, by Jocelyn Bell Burnell and Anthony Hewish, a great deal of conjecture arose that speculated that the "incredibly regular radio emissions" of the pulsars, that emitted a beam of electromagnetic radiation that could only be detected when the emission beam points directly towards the Earth; giving the appearance of a regular signal from some extraterrestrial civilization. However, further studies revealed that the energy pulsed (hence pulsar) by the very dense neutron stars, which demonstrated a highly precise period of rotation and the pulsed energy that emanated from a particular region of the pulsar that correspondingly beamed the electromagnetic radiation toward the Earth at very regular intervals in "narrow, lighthouse-like beams emanating from the stars' magnetic poles."
Such has been science's conceptional understanding of neutron stars since the late 1960s.
Andrea Thompson, of MSNBC.com, explains the difficulties inherent to our four decade long means of understanding the operation of pulsars: "And while radio beams are easy to detect, they account for only a tiny fraction (a few parts in a million) of a pulsar's total power. Gamma rays, on the other hand, account for 10 percent or more. That's where Fermi comes in" she explains.
Romani picks up on Thompson's account and adds: "For the first time, Fermi is giving us an independent look at what heavy stars do."
Michelson continues: "This is the first example of a new class of pulsars that will give us fundamental insights into how these collapsed stars work."
NASA's Goddard Space Flight Center's Alice Harding reiterates the picture that is emerging about gamma-ray-only pulsars, to say: "We think the region that emits the pulsed gamma rays is broader than that responsible for pulses of lower-energy radiation,... The radio beam probably never swings toward Earth, so we never see it. But the wider gamma-ray beam does sweep our way."
Astrophysicist Alice Harding reflects on past understandings of pulsar operation"We used to think the gamma rays emerged near the neutron star's surface from the polar cap, where the radio beams form,... The new gamma-ray-only pulsars put that idea to rest."
Andrea Thompson, provides a summary of "The picture that is now emerging is one of pulsed gamma rays arising far above the neutron star. For the Vela pulsar, the brightest persistent gamma-ray source in the sky, the emission region is thought to lie about 300 miles from the star, which itself has a diameter of just 20 miles."
Thompson continues: "Particles produce the gamma rays as they accelerate along arcs of the pulsar's open magnetic field. This model means that gamma rays would be beamed broadly across the sky, not in the narrow beam like the radio signals."
Romani confirms the four decade-old pulsar model when he declares the new data from LAT "puts the nail in the coffin of the classic polar cap model."
As far as questions that still remain unanswered; are considerations "as to whether gamma ray emission starts at high altitudes over the star or from the star's surface and emanates all the way out,"still provide plenty of debate among experts."
Alice Harding, addressing the location question of where gamma ray emissions initiate and adds that: "So far, Fermi observations to date cannot distinguish which of these models is correct."
Romani differs with Harding by stating: "what you see depends on where you look."
NewScientist contends that: "...gamma rays seem to be produced in vast, trumpet-shaped sheets along the equator high above the star's surface. There, the star's spin pulls magnetic fields - as well as electrons and their antimatter counterparts, positrons - to nearly the speed of light. The fast-moving particles radiate gamma rays as they swirl around in space.... Pulsars thus blast radiation from two regions - their equator and their magnetic poles," and Romani differs with Harding by stating: "what you see depends on where you look."
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