Pulsar – Timelines, Introduction, Articles | Global Oneness

13 Jun 2014 | Author: | Comments Off on Pulsar – Timelines, Introduction, Articles | Global Oneness
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A Wisdom Archive on Pulsar

Introduction to Pulsar including Timelines, Articles and Videos • pulsar: any of various astronomical objects, probably rapidly rotating neutron stars, that emit short, repeating pulses of radio waves.

Some short facts about pulsar (more in-depth further down): A stellar source of radio waves, characterized by the rapid frequency and regularity of the bursts of radio waves emitted. The time between successive pulses is milliseconds for pulsars in binary systems and up to 4 seconds for the slowest. Some pulsars emit pulsed radiation in other bands of the electromagnetic spectrum, including visible light, as well as radio waves.

A pulsar is a rotating neutron star, with a mass similar to the Sun’s but a diameter of only about 10 kilometres. The pulses occur because the neutron star is rotating very rapidly: a beam of radio emission sweeps past an observer once per rotation. The pulses are very regular, apart from the occasional glitch, and all single pulsars are slowing down as they lose rotational energy.

Some X-ray pulsars are in binary systems where complex dynamical effects cause the spin rate to speed up, and these millisecond pulsars are the fastest known. Millisecond pulsars not currently in binary systems are thought to have once belonged to pairs that have been split apart. Most have been discovered in globular clusters, where stars are densely packed and gravitational interactions can easily occur.

At least one pulsar appears to have another neutron star as a companion, and another has two or three planet-sized companions. Their presence is deduced from variations in the arrival time of pulses. Pulsars are formed in supernova explosions, though only two – the Crab Pulsar and the Vela Pulsar – are within currently observable supernova remnants.

– Astronomy and space exploration, www.spacetravel.org

Variable radio star having stable, very short (around one second) periods of pulsations. Electrons moving rapidly in a pulsar’s magnetic field produce narrow beams of radiation which sweep around as the pulsar spins (analogous to sweeping search-light beams).

– Planetary Science Research Discoveries

A rotating neutron star which generates regular pulses of radiation. Pulsars were discovered by observations at radio wavelengths but have since been observed at optical, X-ray, and gamma-ray energies.

– Physical Science, www.sciencemaster.com

A stellar source, such as a rotating single star or pair of stars, emitting electromagnetic radiation which is characterised by rapid frequency and regularity.

– Science, European Space Agency

Commentary by various sources on Pulsar: • The Crab Nebula (catalogue designations M1, NGC 1952, Taurus A) is a supernova remnant and pulsar wind nebula in the constellation of Taurus. – Source: CrystaLinks

• Most of the matter in a star is blown away in the explosion (forming nebulae such as the Crab Nebula) but what remains will collapse into a neutron star (a pulsar or X-ray burster) or, in the case of the largest stars, a black hole. – Source: CrystaLinks – Water

• At the center of the nebula lies the Crab Pulsar, a neutron star (or spinning ball of neutrons), 28?30 km across, which emits pulses of radiation from gamma rays to radio waves with a spin rate of 30.2 times per second. The nebula was the first astronomical object identified with a historical supernova explosion. – Source: CrystaLinks

• A long look at a young pulsar with NASA’s Chandra X-ray Observatory revealed unexpectedly rapid cooling, which suggests that it contains much denser matter than previously expected. The pulsar’s cool temperature and the vast magnetic web of high-energy particles that surrounds it have implications for the theory of nuclear matter and the origin of magnetic fields in cosmic objects. – Source: CrystaLinks

• The infrared telescope surveyed the scene around a pulsar, the remnant of an exploded star, and found a surrounding disk made up of debris shot out during the star’s death throes. The dusty rubble in this disk might ultimately stick together to form planets. This is the first time scientists have detected planet-building materials around a star that died in a fiery blast. – Source: CrystaLinks – Water

• The Polish astronomer Aleksander Wolszczan claimed to have found the first extrasolar planets in 1993, orbiting the pulsar PSR 1257+12. Subsequent investigation has determined that these objects are not ’true’ planets in that they are technically ’sub-brown dwarf masses orbiting an object that is or once was a star’; it is believed that they are unusual remnants of the supernova that produced the pulsar, and did not form as conventional planets do. – Source: CrystaLinks

• Astronomers using the H.E.S.S. telescopes have discovered the first ever modulated signal from space in Very High Energy Gamma Rays. the most energetic such signal ever observed. Regular signals from space have been known since the 1960s, when the first radio pulsar (nicknamed Little Green Men-1 for its regular nature) was discovered. This is the first time a signal has been seen at such high energies. 100,000 times higher than previously known. – Source: CrystaLinks – Water

Introduction to topics related to Pulsar with links to further reading: Pulse Nulling – A drop to a low level in the intensity of radio emission from a pulsar. The phenomenon, which is common, lasts for a few pulses, after which the intensity of emission returns to normal.

– Astronomy and space exploration, www.spacetravel.org

Hercules X-1 – An X-ray pulsar in the constellation Hercules, consisting of a rotating neutron star which is accreting matter from its companion in a binary system. The rotation period of the neutron star is 1.2 seconds and the orbital period of the system 1.7 days.

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– Astronomy and space exploration, www.spacetravel.org

Dispersion Measure Dm – A quantity that indicates the delay between arrival times from a pulsar of radio pulses at different frequencies. Arrival times are spread by the presence of electrons in the interstellar medium. If the density of electrons is known from independent measurements, the dispersion measure of a pulsar may be used to calculate its distance.

– Astronomy and space exploration, www.spacetravel.org

Glitch – A sudden change in the rotation rate of a pulsar. These are particularly prominent in the Vela Pulsar and the Crab Pulsar but many others also show them. In the Vela pulsar the jumps amount to 200 nanoseconds, which is twenty times larger than the steady decrease in period.

Glitches are thought to be caused by starquakes.

– Astronomy and space exploration, www.spacetravel.org

Vela Pulsar – A pulsar in the constellation Vela, associated with a supernova remnant 10,000 years old. It is one of the strongest radio pulsars, and the strongest gamma-ray source in the sky. It was discovered in 1968 during a general search for pulsars in the southern hemisphere and has a short period, 89 milliseconds, characteristic of young pulsars. The period is steadily increasing at a rate of 10.7 nanoseconds a day as the pulsar loses energy.

Since observations of it started, the pulsar has also undergone several major glitches in which the period has suddenly decreased by about 200 nanoseconds.

– Astronomy and space exploration, www.spacetravel.org

Some Timelines for Pulsar: 1967, Nov 28, The first pulsating radio source (pulsar) was detected.

1989, Jan 18, Astronomers discovered pulsar in remnants of Supernova 1987A (LMC).

1968, Feb 29, The discovery of the first ’pulsar,’ a star which emits regular radio waves, was announced by Dr. Jocelyn Bell Burnell at Cambridge, England.

1996, Jun 9, An article described the pulsar B1257+12, 1,300 light-years away, measured by Alex Wolszczam. Measurements indicate a planetary system nearby. Other stars with planets include 51 Pegasi, 70 Virginis, 47 Ursae Majoris and 55 Cancri.

It was later proposed that the evidence for the planets was caused by energy waves circling their home star.

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