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Radio wavelength emissions are the typical radio waves you use to receive signals sent from your favorite radio station. They occupy the frequency range above 1 meter, and as such, the detection of radio emissions from outside our atmosphere requires sophisticated radiotelescope arrays.

The universe is a continuous cycle of creation and destruction. The irregular colliding galaxy M82 is a good example of this cycle in action. Textbooks have described M82 as an exploding galaxy based on its convoluted and striated appearance. Astronomers finally began to realize that what they were witnessing was not death alone but also a violent birth. A collision interaction with its huge neighbor M81 seems to have disrupted M82 so that gas and dust are rapidly being converted into stars, creating a strange corollary of a starburst galaxy. As these stars age, some explode as supernovas, compressing the surrounding gas and triggering still more star formation.^42b

This "starburst" process has been understood in principle and yet never observed in detail. The same interstellar medium that gives rise to new stars also obscures any light coming from where the event itself. Radio waves, however, can penetrate freely through the murk. Scientists have used the Multi-Element Radio-Linked Interferometer Network (MERLIN) to scrutinize the inner regions of M82. The result offers an in-depth look at the galactic upheaval that creates stars en masse.

To generate the image, the Manchester team combined its MERLIN observations with data collected by the Very Large Array (VLA) radio telescope in Socorro, N.M. The composite result covers an area roughly 3,000 by 2,000 light-years across (M82 as a whole is about 40,000 light-years wide) with a resolution comparable to that of the best ground-based optical telescopes. Each of the spherical shapes is debris from the thermonuclear detonation of a short-lived, massive star called a supernova remnant. Some 50 supernovas have occurred in this region within the past 1,000 years, more than 10 times the rate in our own galaxy. M82 is considered a laboratory for understanding the birth and death of high-Mass_solar stars. As the supernova remnants expand, it gradually blurs into the more diffuse radio glow of M82, a relic of older explosions that took place as long as 10 million years ago.

The galactic collisions that produce starburst galaxies are rare in our part of the cosmos. At 10 million light-years distant, M82 is the nearest major starburst galaxy. However, collisions were far more ubiquitous in the early universe, and starbursts were critical events in the evolution of galaxies. Astronomers look to this starburst galaxy as a Rosetta Stone to help them understand how amorphous blobs of gas transformed into the star-studded, organized systems that we see today.

To accomplish this, scientists at the MERLIN facility are again teaming up with their counterparts at the VLA to study the extremely remote objects spotted in the Hubble Deep Field. These radio observations should be able to demonstrate whether the irregular shapes seen by the space telescope are indeed young galaxies which are experiencing early star formation. Such a finding would establish a crucial developmental link between our modern cosmos and the near-formless era of the big bang.

Radio astronomers have found a way to use the twinkling of stars to measure the velocity and distance of these speeding neutron stars that are up above the world so high that they have escaped from the galaxy.^42c In the hope of finding new pulsars and calculating just how fast they can travel, astronomers have devised a method that combines computer modeling with two of the world's largest radio telescopes, the Very Long Baseline Array (VLBA) and the Arecibo Observatory, to measure the speed and distance of these dense, spinning objects that lie well above the galactic plane.

Five years ago astronomers developed a mathematical model for tracking the path of radio waves as they travel through the ionized gas that fills the interstellar medium (ISM). This resulted in giving them a way to calculate the distance to most pulsars. The fastest pulsar recorded to date is B2224+65 in the Guitar Nebula, which is moving at 1,600 kilometers (994 miles) a second. A neutron star is born about once every 100 years in the galaxy and that about one in four neutron stars will eventually escape. Over the age of our galaxy, the Milky Way, this means that about 25 million neutron stars have escaped.

The problem is that this model cannot estimate distances to pulsars that have escaped from the Milky Way. Now, scientists t have found a way to calculate both the distance and the speed of these stellar remnants by measuring the rate at which they twinkle and combining this with their angular motion in the sky as measured by the VLBA.

In more technical terms, the astronomers are measuring the interstellar scintillation (ISS) of pulsars. ISS is analogous to the twinkling of stars but occurs in the radio signals from celestial sources rather than in optical light. The twinkling of light from distant stars as seen from Earth is caused by the atmosphere, but radio scintillation results as radio waves travel through interstellar gas and the turbulence that resides in it.

To calculate the speed and distance of very faint pulsars will require measurements from both Arecibo Observatory in Puerto Rico and the VLBA. The VLBA is a radio interferometer, consisting of 10, 25-meter (27 yards) dishes spread across the United States from the Virgin Islands to Hawaii. Recorded data from the 10 dishes are played back into a central computer to mimic a single, giant telescope. It produces radio images of compact radio sources with great resolution and quality.