Wednesday, September 28, 2011

First Astronomy Celebration: Supernovæ

Welcome to Astronomical Events Calendar's first astronomy celebration! After starting in April, 2011 (we've been online since February 2011 but on another site), we start our first astronomy celebration becasue Astronomical Events Calendar has reached 5000 pageviews*! Hopefully we will be doing our next astronomy celebration very soon - at 10000 pageviews, with many more after that to come! Thank you for visiting and I hope you enjoy our first astronomy celebration!

As we begin our first astronomy celebration, have I actually defined what an 'astronomy celebration' is? Here at Astronomical Events Calendar, every time we reach certain goal-points, i.e. every time we reach 5000, 10000, 15000 pageviews +, we post a celebration of our success for making astronomy known (after all that is why Astronomical Events Calendar was created - to promote and inform others about the wonderful world of astronomy!). This celebration's topic is on supernovæ - our festival incorporates all aspects of  what supernovæ are in exciting photodramas and special reports. Again, thank you for your support by visiting, and enjoy the celebration!

*We are at approximately at 5008 pageviews  09/28/2011 @ 04:27:50 pm EST!!


UPERNOVÆ are perhaps one of the most fascinating studying fields of stellar astronomy. When a star is born, it forms in a nebula (literally a 'star nursery'), but when a star dies, it becomes a supernova, going through much molecular change causing a powerful explosion, which gives astronomers much to study. By definition, a supernova is an “exploding star: a catastrophic explosion of a large star in the latter stages of stellar evolution, with a resulting short-lived luminosity from 10 to 100 million times that of the Sun.[1]” Although the definition is loquacious, it does sum in total what a supernova is and provides good insight on the result of an explosion. In a more transparent sense, a supernova is an extremely spontaneous outburst of luminosity and radiation that may (or in lesser cases) may outshine a single host galaxy. But, after approximately a few months or even weeks, the paroxysm ends, resulting in the fading of the star—the star is in the final stages of death, and might outburst again until its foremost death, where it turns into a supernova remnant; a very empyrean and seraphic state. From there, the fate of star is either one of three: to become a neutron star, a black hole, or a white dwarf, each of which are very powerful and exotic celestial phenomena.

The two words ‘supernova’ and ‘nova’ both posses a strong hold on each other’s meanings, but very differently do they translate. From the Latin (novus) for ‘new’, a nova is correctly defined a “star that flares and fades: a star that suddenly increases dramatically in brightness and then fades to its original luminosity over a short period of months or years.[2]” Whereas a nova is a star that periodically emanates radiation and luminosity, a supernova is the stage in which the explosion occurs, letting astronomers known when a star is in the final stages of dying. Although you might think that ‘supernova’ has been in used since the times of Copernicus and Galileo were observing the celestial sphere, it has not. ‘Nova’ has been in use, but Swiss astrophysicist and astronomer Fritz Zwicky first coined the term in 1926[3]. He used the Latin suffix super- translating as ‘more’ or ‘to a farther extent,’ correctly gives us what a supernova really means: a stellar phenomenon greater than a nova. Zwicky was also “the first [person] to understand that [supernovæ] resulted from the explosion of massive stars.[4]

Supernovæ, in astronomy, are events heard and discussed greatly by astronomers, and much is out there to provide us with the invaluable information of what a supernova is and its properties. One of the well-known instruments in space currently is the Chandra X-Ray Observer—a great aid in the discoveries and a great tool to learn more about them. Approximately every fifty years, a supernova occurs within our Galaxy and all the other billions of galaxies in the universe. Many stars die each day just as as many are born. Chandra describes this event as “one of the most violent events in the universe, and the force of the explosion generates a blinding flash of radiation, as well as shock waves analogous to sonic booms.[5]” Although supernovæ seem to be harmless bursts of energy as we here on earth perceive, supernovæ are, as Chandra says, one of the most violent interstellar astronomical phenomena—releasing tons of energy and sonic booms beyond audible comprehension. During an explosion, a single star (called at this point a supernova) can expel much (if not all) of the star’s composition and matter at expeditious rates of up to thirty-thousand kilometers per second, or a tenth the speed of light. From there, a shock wave is driven into the encircling interstellar medium, whereas the ‘interstellar medium’ is the empty space in the universe, not occupied by matter, like stars and planets. After the explosion, the supernova gathers up the expelled mass and brings it back together from the interstellar medium, to create a remnant.

Supernovæ Classification

Based on the knowledge that supernova can explode differently, astronomers have divided them into classes based on their properties and characteristics. But it has not always been this way. Supernovæ were first categorized in 1941 when Rudolph Minkowski realized that more than two different types existed. Although it has been a common error of many people to assume that only two different classes exist[6], it is not true. According to Cosmos, an astronomical encyclopædia written by research astronomers, supernova are “classified based on the presence or absence of certain features in their optical spectra taken near maximum light.[7]” What this means, is astronomers divide supernovæ based on what they are comprised of or lack only during maximum light. In Figure 1, we see the classification of different supernova, which are divided into four ‘types,’ although this fact is well debated (you will see Type Two supernovæ divided into two types, based on light curves they emit.) To explain Figure 1, we see the initials SN eminent on the top; this SN respectively stands for ‘supernova,’ where division starts.

Fig. One in link below.

The H (and no H) beneath ‘supernova (SN)’ stands for ‘hydrogen,’ and ‘no hydrogen,’ specifying whether hydrogen is emitted during the explosion, tell us much about division. Type Two supernovæ will always use hydrogen, ergo as seen in their spectra, meaning, when astronomers view supernovæ, they may look through a different eyepieces to view different things (like infrared filters). Supernovæ with this presence of hydrogen are therefore classified in Type II, whereas where the presence of no hydrogen, is divided into Type I, which can be subdivided from there. The Si is placed in meaning for silicon, or the absence of silicon. If silicon is present (as seen through special filters like hydrogen before), then the supernovæ is a Type Ia, and thus thermonuclear.


[1] Definition provided by the Encarta World English Dictionary, copyright 2009 by Microsoft. Accessed September 27, 2011 from
[2] Ibid. except for link; accessed September 27, 2011 from
[3] Date provided by Merriam and Webster’s Dictionary, copyright 2011 by Mirriam-Webster. Accessed September 27, 2011 from
[4] Fox, Derek. “Fritz Zwicky Advanced X-Ray Astrophysics Facility.” Accessed September 27, 2011 from
[5] Chandra X-Ray Observer, “Supernovæ and Supernovæ Remnants.” The Chandra X-Ray Observatory (November 16, 2010). Accessed September 28, 2011, from
[6] (From comment section). Andrea Thompson, “What is a Supernova?” (May 4, 2009). Accessed September 28, 2011 from
[7] Swinburne University of Technology. “Supernova Classification.” COSMOS—the SAO Encyclopædia of Astronomy. Accessed September 29, 2011 from
[8] Powell, Richard. “The Hertzsprung-Russell Diagram.” Accessed September 30, 2011 from
[9] Hillebrandt, Wolfgang, and Niemeyer, Jens C. “Type Ia Supernova Explosion Models.” Annual Review of Astronomy and Astrophysics 38 (2000): 191–230.
[10] The Astrophysics Spectator. “Thermonuclear Supernovæ.” May 2, 2009; Accessed September 30, 2011 from
[11] Swinburne University of Technology. “Type Ib Supernovæ.” COSMOS—the SAO Encyclopædia of Astronomy Accessed October 1, 2011 from
[12]Swinburne University of Technology. “Type Ic Supernovæ.” COSMOS—the SAO Encyclopædia of Astronomy Accessed October 1, 2011 from

[13] Swinburne University of Technology. “Type II Supernovæ.” COSMOS—the SAO Encyclopædia of Astronomy Accessed October 1, 2011 from
[14] Branch, David & Doggett, Jesse B. A Comparative Study of Supernova Light Curves. The Astronomical Journal—Volume 90, Number 11. November 1985. Accessed October 1, 2011 from
[15] Ibid. Images on page 2304 of study, page 2 in PDF file.

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