Astrophysics is the branch of astronomy that employs the principles of physics and chemistry "to ascertain the nature of the astronomical objects, rather than their positions or motions in space". Among the objects studied are the Sun, other stars, extrasolar planets, the interstellar medium and the cosmic microwave background. Emissions from these objects are examined across all parts of the electromagnetic spectrum, the properties examined include luminosity, density and chemical composition; because astrophysics is a broad subject, astrophysicists apply concepts and methods from many disciplines of physics, including classical mechanics, statistical mechanics, quantum mechanics, relativity and particle physics, atomic and molecular physics. In practice, modern astronomical research involves a substantial amount of work in the realms of theoretical and observational physics; some areas of study for astrophysicists include their attempts to determine the properties of dark matter, dark energy, black holes, other celestial bodies.

Topics studied by theoretical astrophysicists include Solar System formation and evolution. Astronomy is an ancient science, long separated from the study of terrestrial physics. In the Aristotelian worldview, bodies in the sky appeared to be unchanging spheres whose only motion was uniform motion in a circle, while the earthly world was the realm which underwent growth and decay and in which natural motion was in a straight line and ended when the moving object reached its destination, it was held that the celestial region was made of a fundamentally different kind of matter from that found in the terrestrial sphere. During the 17th century, natural philosophers such as Galileo and Newton began to maintain that the celestial and terrestrial regions were made of similar kinds of material and were subject to the same natural laws, their challenge was. For much of the nineteenth century, astronomical research was focused on the routine work of measuring the positions and computing the motions of astronomical objects.

A new astronomy, soon to be called astrophysics, began to emerge when William Hyde Wollaston and Joseph von Fraunhofer independently discovered that, when decomposing the light from the Sun, a multitude of dark lines were observed in the spectrum. By 1860 the physicist, Gustav Kirchhoff, the chemist, Robert Bunsen, had demonstrated that the dark lines in the solar spectrum corresponded to bright lines in the spectra of known gases, specific lines corresponding to unique chemical elements. Kirchhoff deduced that the dark lines in the solar spectrum are caused by absorption by chemical elements in the Solar atmosphere. In this way it was proved that the chemical elements found in the Sun and stars were found on Earth. Among those who extended the study of solar and stellar spectra was Norman Lockyer, who in 1868 detected radiant, as well as dark, lines in solar spectra. Working with the chemist, Edward Frankland, to investigate the spectra of elements at various temperatures and pressures, he could not associate a yellow line in the solar spectrum with any known elements.

He thus claimed the line represented a new element, called helium, after the Greek Helios, the Sun personified. In 1885, Edward C. Pickering undertook an ambitious program of stellar spectral classification at Harvard College Observatory, in which a team of woman computers, notably Williamina Fleming, Antonia Maury, Annie Jump Cannon, classified the spectra recorded on photographic plates. By 1890, a catalog of over 10,000 stars had been prepared that grouped them into thirteen spectral types. Following Pickering's vision, by 1924 Cannon expanded the catalog to nine volumes and over a quarter of a million stars, developing the Harvard Classification Scheme, accepted for worldwide use in 1922. In 1895, George Ellery Hale and James E. Keeler, along with a group of ten associate editors from Europe and the United States, established The Astrophysical Journal: An International Review of Spectroscopy and Astronomical Physics, it was intended that the journal would fill the gap between journals in astronomy and physics, providing a venue for publication of articles on astronomical applications of the spectroscope.

Around 1920, following the discovery of the Hertzsprung–Russell diagram still used as the basis for classifying stars and their evolution, Arthur Eddington anticipated the discovery and mechanism of nuclear fusion processes in stars, in his paper The Internal Constitution of the Stars. At that time, the source of stellar energy was a complete mystery; this was a remarkable development since at that time fusion and thermonuclear energy, that stars are largely

The Chénier Cell known as the South Shore Gang, was a Montreal based Front de libération du Québec terrorist cell responsible for a decade of bombing, armed robbery and kidnapping that led to the October Crisis. The Chénier Cell was named after the Lower Canada Rebellion patriote movement leader Jean-Olivier Chénier. A violent Quebec sovereignty movement, the Chénier Cell attempted to usurp the elected Government of Quebec and create a Québécois people's uprising to establish a new Quebec state independent of Canada; the four known members of the Chénier Cell were: Paul Rose, Jacques Rose, Francis Simard and Bernard Lortie. On October 5, 1970, members of another Montreal based FLQ cell, the Liberation Cell, kidnapped the United Kingdom Trade Commissioner James Richard Cross from his Montreal home. On October 8, 1970, the FLQ Manifesto was broadcast by CBC/Radio-Canada as one of the many demands required for the release of James Cross; the manifesto criticised big business, the Catholic Church, René Lévesque, Robert Bourassa and declared Pierre Trudeau "a queer".

On October 10, 1970, the Chénier Cell kidnapped the Vice-Premier of Quebec and Labour Minister, Pierre Laporte. The kidnappers approached Laporte, while he was playing football with his nephew on his front yard and forced him into their vehicle at gunpoint; the members of the Chénier Cell believed many other Québécois people would follow them in an uprising to create an independent state. On October 15, 1970, the Government of Quebec put forward a request for the Canadian Armed Forces to support the Service de police de la Ville de Montréal. On October 16, 1970, the Federal Government of Canada proclaimed the existence of a state of "apprehended insurrection" under the War Measures Act; these emergency regulations made membership a criminal act. In addition, normal liberties were suspended and arrests and detentions were authorized without charges. On October 17, 1970, the day after the Government of Canada invoked the War Measures Act, the Chénier Cell announced that they had executed Laporte.

Laporte was found strangled in the back of a stolen motor vehicle abandoned near the Montreal Saint-Hubert Longueuil Airport. In late December 1970, four weeks after the members of the Liberation Cell were found by authorities, the Chénier Cell members were located in a farmhouse basement at Saint-Luc, Quebec; the Chénier Cell members were put on trial and three were convicted for kidnapping and murder, while Jacques Rose was convicted of being an accessory after the fact with all members pleading "responsible". Timeline of the Front de libération du Québec List of terrorist attacks in Canada

Joshua "Josh" Lafazan is an American politician, the legislator for the 18th District of the Nassau County Legislature. He is the second youngest public servant. Lafazan was placed on the Long Island Press Power List of the 50 most influential people on Long Island in 2012, his book, titled Political Gladiators: How Millennials Can Navigate the 21st Century Political Minefield and WIN!, was published in November 2015, tells experiences of other politicians who were elected at a young age. Lafazan has been featured as a speaker in TedX conferences, he is a professor at Long Island University, instructing a course focusing on how to run for public office as a young candidate. Josh Lafazan graduated from Syosset High School in June 2012, he attended Nassau Community College, received the State University of New York Chancellor's Award for Student Excellence. He was named a recipient of the New York State School Boards Association Lifetime Achievement Award in 2016. Lafazan attended Cornell University for his Bachelor of Science degree and Harvard University for his Master of Education degree.

During the latter part of his senior year of high school, Lafazan had been campaigning for a trustee position on the Syosset Board of Education, which he won in May of that year with 82 percent of the vote. He was re-elected to the board in 2015 for another three-year term. On April 26, 2013, Josh was elected to the Long Island Council on Alcoholism and Drug Dependence, in which they credited him for founding Saferide Syosset, an outreach program to help guide teenagers on how to get home when impaired. On June 8, 2017, Lafazan announced, he won on November 7, 2017, with 56 percent of the vote, against incumbent Republican Donald MacKenzie. Lafazan resigned from his position on the school board on December 31, 2017, based on a clause in the Nassau County Charter that provides a possible conflict with holding both positions. Lafazan has authored and passed multiple notable pieces of legislation in his tenure as a legislator. "Timothy's Law" was passed in August 2018, which established a 24-hour hotline for substance abuse intervention.

Related legislation mandated the creation of a smartphone application containing resources for substance abuse, such as treatment center locations. The "Dignity For Our Heroes" package, signed into law in April 2019, marked veterans as a protected status under the County's Human Rights Law, in addition to creating the Nassau Commission on Ending Veteran Homelessness, which guides projects meant to reduce the number of veterans who are housing insecure in the region. Lafazan was re-elected for his second term in 2019 with over 70 percent of the vote against Republican challenger Timothy Jenks