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Gregory W. Henry is a Senior Research Scientist at Tennessee State University. His research interests include Automated Astronomy with robotic telescopes, high-precision photometry, solar-type stars, extrasolar planetary systems, chromospherically active stars, pulsating variable stars, the Sun-Climate connection.
See the ORCID link below for a list of publications.
An astronomer is a scientist in the field of astronomy who focuses their studies on a specific question or field outside the scope of Earth. They observe astronomical objects such as stars, planets, moons, comets and galaxies – in either observational or theoretical astronomy. Examples of topics or fields astronomers study include planetary science, solar astronomy, the origin or evolution of stars, or the formation of galaxies. A related but distinct subject is physical cosmology, which studies the Universe as a whole.
The national flag of the United States, often referred to as the American flag or the U.S. flag, consists of thirteen equal horizontal stripes of red alternating with white, with a blue rectangle in the canton, referred to as the union and bearing fifty small, white, five-pointed stars arranged in nine offset horizontal rows, where rows of six stars alternate with rows of five stars. The 50 stars on the flag represent the 50 U.S. states, and the 13 stripes represent the thirteen British colonies that declared independence from Great Britain, which they obtained in their victory in the American Revolutionary War.
A galaxy is a system of stars, stellar remnants, interstellar gas, dust, and dark matter bound together by gravity. The word is derived from the Greek galaxias (γαλαξίας), literally 'milky', a reference to the Milky Way galaxy that contains the Solar System. Galaxies, averaging an estimated 100 million stars, range in size from dwarfs with less than a thousand stars, to the largest galaxies known – supergiants with one hundred trillion stars, each orbiting its galaxy's center of mass. Most of the mass in a typical galaxy is in the form of dark matter, with only a few percent of that mass visible in the form of stars and nebulae. Supermassive black holes are a common feature at the centres of galaxies.
The International Astronomical Union is a non-governmental organisation with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreach, education, and development through global cooperation. It was founded in 1919 and is based in Paris, France.
The Sun is the star at the center of the Solar System. It is a massive, hot ball of plasma, inflated and heated by energy produced by nuclear fusion reactions at its core. Part of this energy is emitted from its surface as light, ultraviolet, and infrared radiation, providing most of the energy for life on Earth. The Sun has been an object of veneration in many cultures. It has been a central subject for astronomical research since antiquity.
A star is a luminous spheroid of plasma held together by self-gravity. The nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night; their immense distances from Earth make them appear as fixed points of light. The most prominent stars have been categorised into constellations and asterisms, and many of the brightest stars have proper names. Astronomers have assembled star catalogues that identify the known stars and provide standardized stellar designations. The observable universe contains an estimated 1022 to 1024 stars. Only about 4,000 of these stars are visible to the naked eye—all within the Milky Way galaxy.
In astronomy, a variable-star designation is a unique identifier given to variable stars. It uses a variation on the Bayer designation format, with an identifying label preceding the Latin genitive of the name of the constellation in which the star lies. See List of constellations for a list of constellations and the genitive forms of their names. The identifying label can be one or two Latin letters or a V plus a number. Examples are R Coronae Borealis, YZ Ceti, V603 Aquilae.
Astronomy is a natural science that studies celestial objects and the phenomena that occur in the cosmos. It uses mathematics, physics, and chemistry in order to explain their origin and their overall evolution. Objects of interest include planets, moons, stars, nebulae, galaxies, meteoroids, asteroids, and comets. Relevant phenomena include supernova explosions, gamma ray bursts, quasars, blazars, pulsars, and cosmic microwave background radiation. More generally, astronomy studies everything that originates beyond Earth's atmosphere. Cosmology is a branch of astronomy that studies the universe as a whole.
Astrophysics is a science that employs the methods and principles of physics and chemistry in the study of astronomical objects and phenomena. As one of the founders of the discipline, James Keeler, said, Astrophysics "seeks to ascertain the nature of the heavenly bodies, rather than their positions or motions in space–what they are, rather than where they are." Among the subjects studied are the Sun, other stars, galaxies, extrasolar planets, the interstellar medium and the cosmic microwave background. Emissions from these objects are examined across all parts of the electromagnetic spectrum, and the properties examined include luminosity, density, temperature, and chemical composition. Because astrophysics is a very broad subject, astrophysicists apply concepts and methods from many disciplines of physics, including classical mechanics, electromagnetism, statistical mechanics, thermodynamics, quantum mechanics, relativity, nuclear and particle physics, and atomic and molecular physics.
The Orion Arm, also known as the Orion–Cygnus Arm, is a minor spiral arm within the Milky Way Galaxy spanning 3,500 light-years in width and extending roughly 10,000 light-years in length. This galactic structure encompasses the Solar System, including Earth. It is sometimes referred to by alternate names such as the Local Arm or Orion Bridge, and it was previously identified as the Local Spur or the Orion Spur. It should not be confused with the outer terminus of the Norma Arm, known as the Cygnus Arm.
OB stars are hot, massive stars of spectral types O or early-type B that form in loosely organized groups called OB associations. They are short lived, and thus do not move very far from where they formed within their life. During their lifetime, they will emit much ultraviolet radiation. This radiation rapidly ionizes the surrounding interstellar gas of the giant molecular cloud, forming an H II region or Strömgren sphere.
The Milky Way is the galaxy that includes the Solar System, with the name describing the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye. The term Milky Way is a translation of the Latin via lactea, from the Greek γαλαξίας κύκλος, meaning "milky circle". From Earth, the Milky Way appears as a band because its disk-shaped structure is viewed from within. Galileo Galilei first resolved the band of light into individual stars with his telescope in 1610. Until the early 1920s, most astronomers thought that the Milky Way contained all the stars in the Universe. Following the 1920 Great Debate between the astronomers Harlow Shapley and Heber Doust Curtis, observations by Edwin Hubble showed that the Milky Way is just one of many galaxies.
Planetary habitability is the measure of a planet's or a natural satellite's potential to develop and maintain environments hospitable to life. Life may be generated directly on a planet or satellite endogenously or be transferred to it from another body, through a hypothetical process known as panspermia. Environments do not need to contain life to be considered habitable nor are accepted habitable zones (HZ) the only areas in which life might arise.
In astronomy, Durchmusterung or Bonner Durchmusterung (BD) is an astrometric star catalogue of the whole sky, published by the Bonn Observatory in Germany from 1859 to 1863, with an extension published in Bonn in 1886. The name comes from Durchmusterung, a German word used for a systematic survey of objects or data. The term has sometimes been used for other astronomical surveys, including not only stars, but also the search for other celestial objects. Special tasks include celestial scanning in electromagnetic wavelengths shorter or longer than visible light waves.
The Smithsonian Astrophysical Observatory Star Catalog is an astrometric star catalogue, created by Smithsonian Institution, a research institute. It was published by the Smithsonian Astrophysical Observatory in 1966 and contains 258,997 stars. The catalogue was compiled from various previous astrometric catalogues, and contains only stars to about ninth magnitude for which accurate proper motions were known. Names in the SAO catalogue start with the letters SAO, followed by a number. The numbers are assigned following 18 ten-degree bands of declination, with stars sorted by right ascension within each band.
The QS World University Rankings is a portfolio of comparative college and university rankings compiled by Quacquarelli Symonds, a higher education analytics firm. Its first and earliest edition was published in collaboration with Times Higher Education (THE) magazine as Times Higher Education–QS World University Rankings, inaugurated in 2004 to provide an independent source of comparative data about university performance. In 2009, the two organizations parted ways to produce independent university rankings, the QS World University Rankings and THE World University Rankings.
A stellar collision is the coming together of two stars caused by stellar dynamics within a star cluster, or by the orbital decay of a binary star due to stellar mass loss or gravitational radiation, or by other mechanisms not yet well understood.
The Stars virus is a computer virus which infects computers running Microsoft Windows. It was named and discovered by Iranian authorities in April 2011. Iran claimed it was used as a tool to commit espionage. Western researchers came to believe it is probably the same thing as the Duqu virus, part of the Stuxnet attack on Iran.
Stellar chemistry is the study of chemical composition of astronomical objects; stars in particular, hence the name stellar chemistry. The significance of stellar chemical composition is an open ended question at this point. Some research asserts that a greater abundance of certain elements in the stellar mass are necessary for a star's inner solar system to be habitable over long periods of time. The hypothesis being that the "abundance of these elements make the star cooler and cause it to evolve more slowly, thereby giving planets in its habitable zone more time to develop life as we know it." Stellar abundance of oxygen also appears to be critical to the length of time newly developed planets exist in a habitable zone around their host star. Researchers postulate that if our own sun had a lower abundance of oxygen, the Earth would have ceased to "live" in a habitable zone a billion years ago, long before complex organisms had the opportunity to evolve.
Time-domain astronomy is the study of how astronomical objects change with time. Though the study may be said to begin with Galileo's Letters on Sunspots, the term now refers especially to variable objects beyond the Solar System. Changes over time may be due to movements or changes in the object itself. Common targets included are supernovae, pulsating stars, novas, flare stars, blazars and active galactic nuclei. Visible light time domain studies include OGLE, HAT-South, PanSTARRS, SkyMapper, ASAS, WASP, CRTS, GOTO and in a near future the LSST at the Vera C. Rubin Observatory.
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