General Science Class 4th (MCQs=282)

A supernova (pl.: supernovae or supernovas) is a powerful and luminous explosion of a star. A supernova occurs during the last evolutionary stages of a massive star, or when a white dwarf is triggered into runaway nuclear fusion. The original object, called the progenitor, either collapses to a neutron star or black hole, or is completely destroyed to form a diffuse nebula. The peak optical luminosity of a supernova can be comparable to that of an entire galaxy before fading over several weeks or months

The word supernova has the plural form supernovae (/-viː/) or supernovas and is often abbreviated as SN or SNe. It is derived from the Latin word nova, meaning 'new', which refers to what appears to be a temporary new bright star. Adding the prefix "super-" distinguishes supernovae from ordinary novae, which are far less luminous. The word supernova was coined by Walter Baade and Fritz Zwicky, who began using it in astrophysics lectures in 1931.[1][2] Its first use in a journal article came the following year in a publication by Knut Lundmark, who may have coined it independently.[2][3]

Supernova neutrinos are weakly interactive elementary particles produced during a core-collapse supernova explosion.[1] A massive star collapses at the end of its life, emitting on the order of 1058 neutrinos and antineutrinos in all lepton flavors.[2] The luminosity of different neutrino and antineutrino species are roughly the same.[3] They carry away about 99% of the gravitational energy of the dying star as a burst lasting tens of seconds.[4][5] The typical supernova neutrino energies are 10 to 20 MeV.[6] Supernovae[a] are considered the strongest and most frequent source of cosmic neutrinos in the MeV energy range. Since neutrinos are generated in the core of a supernova, they play a crucial role in the star's collapse and explosion.[7] Neutrino heating is believed to be a critical factor in supernova explosions.[1] Therefore, observation of neutrinos from supernovae provides detailed information about core collapse and the explosion mechanism.[8] Further, neutrinos undergoing collective flavor conversions in a supernova's dense interior offers opportunities to study neutrino-neutrino interactions.[9] The only supernova neutrino event detected so far is SN 1987A.[b] Nevertheless, with current detector sensitivities, it is expected that thousands of neutrino events from a galactic core-collapse supernova would be observed.[11] The next generation of experiments are designed to be sensitive to neutrinos from supernova explosions as far as Andromeda or beyond.[12] The observation of supernovae will broaden our understanding of various astrophysical and particle physics phenomena.[13] Further, coincident detection of supernova neutrino in different experiments would provide an early alarm to astronomers about a supernova.

Based on evidence and scientific analysis, Venus is the planet in our solar system that is most similar to Earth in terms of overall size and bulk composition: - Venus has a diameter of 7,520 miles, very close to Earth's diameter of 7,926 miles. The two planets are essentially the same size. - Venus and Earth also have nearly identical densities, suggesting they have a comparable proportion of iron-rich core to mantle and crust. This implies a highly similar interior structure and composition on an bulk planetary scale. - Venus likely formed from a similar accumulation of rocks and metals as Earth, resulting in minerals and elements in corresponding proportions. The two planets share a comparable geochemical makeup. - Both Venus and Earth are categorized as terrestrial planets composed primarily of silicate rocks and iron, as opposed to the gas giants Jupiter, Saturn, Neptune and Uranus. They are more closely matched in their fundamental constitution. - While Venus' highly carbon dioxide-dominated atmosphere is very different from Earth's, this does not alter the underlying geological and chemical similarities in the two planets' rocky cores and interior compositions. So in summary, based on converging lines of evidence related to size, density, formation history and bulk mineralogy, Venus emerges as the terrestrial planet in our solar system that is most analogous to Earth in terms of its overall mass, dimensions and fundamental composition. The atmospheres and surface environments of the two worlds have certainly diverged, but their roots appear to lie in closely comparable origins.