By Vinita Domier
A relatively bright and very rare cataclysmic stellar explosion known as a supernova was discovered on Jan. 21 in the Cigar Galaxy (M82) in the Ursa Major constellation. As supernova SN2014J is only about 12 million light years away, it is bright enough to be viewed in a small telescope by Northern Hemisphere observers. It is the closest Type Ia supernova discovered since 1972, and the closest supernova of any type discovered since 2004.
Davis Astronomy Club will have free telescope viewing of the supernova at 7 p.m. Saturday at Explorit Science Center, 3141 Fifth St. All ages are welcome to attend the featured presentation indoors, followed by the star party outdoors, weather permitting. We also will look at Jupiter and its moons.
Supernova SN2014J is in the northeastern sky in the evenings north of the Big Dipper bowl, and is visible all night for mid-latitude observers. SN2014J is expected to peak in brightness on Sunday before gradually fading out in the coming weeks. Since its discovery, it already has brightened from a visual magnitude of +11.7 to +10.6. Barring clouds, the new moon on Wednesday created ideal viewing conditions for the next seven to 10 days.
Supernovae occur at the end of the life cycles of big stars. Stellar evolution and life span are predetermined by the size of a star at the time of its formation. Stars are accreted in planetary nebulae, which are primarily composed of hydrogen gas.
Stars shine brightly for millions or billions of years while undergoing thermonuclear fusion reactions. Hydrogen gas is synthesized into heavier elements, and a tremendous amount of energy is released in the form of electromagnetic radiations and charged particles. More massive stars burn through their core fuel at a much faster pace, thereby significantly shortening their life spans.
Stars of different sizes “die” in very different ways when their gaseous fuel is all used up. A small star (size of our sun) transforms into a red giant, then expels its outer layers in planetary nebula, leaving behind a white dwarf core star that eventually may cool to a black dwarf. A much bigger star transforms into a red supergiant, then annihilates in a very bright cataclysmic Type II supernova explosion, leaving behind a dense neutron star core, or even a black hole.
When a white dwarf star is in a binary or multi-star system, its gravity pulls in gaseous material from the close companion star. If the white dwarf reaches the Chandersekhar limit of critical mass (1.44 times solar mass), it becomes unstable and explodes in a bright Type Ia supernova.
Astronomers use Type Ia supernovae as “standard candles” to determine the distances to galaxies where they have been detected, and have used the distance and spectral red-shift data to infer the existence of dark energy that is speeding the universe’s expansion.
Explorit’s coming events:
* Explorit’s “Beautiful World: Science and Art” exhibition is open to the public every Wednesday, Saturday and Sunday from 1 to 5 p.m. and every Friday from 3 to 6 p.m. Admission is $5 per person; Explorit members, teachers and children ages 2 and under are free.
* After-School Science Adventures for students in kindergarten through sixth grade begin Wednesday afternoons at Explorit in February. Call 530-756-0191 for more information or to register.