What Are Star Remnants?

In the popular movie and comic book “The Fantastic Four”, the heroes have incredible powers granted them by exposure to cosmic rays. As their leader, a man with unrivalled intelligence and scientific learning, could tell them, it is believed that cosmic rays originate with what is known as a “Supernova remnant”, or star remnant.

A Look at Star Remnants

When a star ends its life cycle one of two things happen; after attaining a red giant phase, a star will either cool and shrink, becoming a white dwarf, or it will explode in a supernova (and eventually shrink and collapse, becoming either a neutron star or a black hole.) It is this second instance, the supernova, that results in what is known as “star remnants” or “supernova remnants”, commonly referred to as SNR. With the word remnants in the name it may seem like star remnants are scattered pieces of the former star, and in a sense this is true, but a SNR is actually a structure in space, part of the universal (literally) cycle of life and death.

What is a SNR

A SNR is a structure that is left over after a star goes supernova. The explosion of a supernova, which emits so much energy at once that it can briefly outshine the entire galaxy it lives in, ejects radiation and star material into the surrounding area. As much energy as our Sun emits over its entire 10 billion year life time is put out all at once. It travels out at a speed roughly one percent of the speed of light, or 3 million metres per second. Compare this to the fasted wind in our solar system, found on the planet Saturn, which is 500 metres per second.

The resultant shockwave when this star material hits the interstellar gas in the region can cause temperatures to rise to 10 million Kelvin. Yet all of this is contained in a shell, which will eventually cool. This leads to the cooling of the interior, which in turn causes the speed of the ejecta to slow.

Studying SNR

Supernovas don’t happen every day, at least not in the Milky Way. In our galaxy one supernova comes along about every 50 years. Considering, however, that a supernova occurs at the end of a lifespan of what could be billions of years, two supernovas a century is an interesting occurrence. In order to study SNR, however, it is critical to observe other galaxies if a scientist does not want to wait fifty years. The discovery of SNR and supernovas in progress is typically done by observing a galaxy and comparing the observations to earlier photographs and looking for changes. While SNR’s can’t be predicted with much accuracy, the sudden appearance of an object of luminosity that is dwarfing that of the entire galaxy is a good clue that a supernova just occurred.

Final Thoughts

It is interesting to note that the discovery and examination of star remnants greatly depends on the amateur astronomer. Amateurs outnumber the pros by a wide margin, and, as in many areas of astronomy, their constant vigilance often gives clues to the pros of where to look for new discoveries.

Related Articles in the 'The Stars' Category...

• How Big Are the Stars?
• How Far Away are the Stars?
• Main Sequence Life of Stars
• Pioneer Plaques
• Star Formation
• The Death of Stars
• The Milky Way
• Types of Star
• Using Constellations to Find Other Constellations
• What's Inside a Star