Civil Rights
Movements, leaders, victories and the continuing fight for equality.
q2K BHP
Black History Portal
THE BHP WIRE —
HIDDEN TRUTHS
What's New!
Explore the people, places, events, achievements, struggles and stories that shaped our journey.
Movements, leaders, victories and the continuing fight for equality.
Innovation, patents, science, technology and world-changing contributions.
Pioneers, champions, Negro Leagues, records, activism and excellence.
Meet the people whose lives, choices and achievements shaped the journey.
Black towns, communities, institutions and places where history happened.
Moments that changed communities, movements, institutions and the nation.
Mansa Musa was the ruler of the Mali Empire in West Africa. Details recorded here should be sourced; unknown information is left blank.
MORE →Reflects the personal views, recollections, and perspective of the author, Mike Davis.
This is a personal recollection on the Move fire on May 13, 1985
Transit-timing variation is a method for detecting exoplanets by observing variations in the timing of a transit. This provides an extremely sensitive method capable of detecting additional planets in the system with masses potentially as small as that of Earth. In tightly packed planetary systems, the gravitational pull of the planets among themselves causes one planet to accelerate and another planet to decelerate along its orbit. The acceleration causes the orbital period of each planet to change. Detecting this effect by measuring the change is known as transit-timing variations.[1][2][3][4][5][6][7][8] "Timing variation" asks whether the transit occurs with strict periodicity or if there exists a variation.
The first significant detection of a non-transiting planet using transit-timing variations was carried out with NASA's Kepler telescope. The transiting planet Kepler-19b shows transit-timing variation with an amplitude of 5 minutes and a period of about 300 days, indicating the presence of a second planet, Kepler-19c, which has a period that is a near-rational multiple of the period of the transiting planet.[9][10]
In 2010, researchers proposed a second planet orbiting WASP-3 based on transit-timing variation,[11][12] but this proposal was debunked in 2012.[13]
Transit-timing variation was first convincingly detected for planets Kepler-9b and Kepler-9c [14] and gained popularity by 2012 for confirming exoplanet discoveries.[15]
Exoplanet TOI-199c was also discovered using this method.[16]
TTV can also be used to indirectly measure the mass of the exoplanets in compact, multiple-planet systems and/or system whose planets are in resonant chains. By performing a series of analytical (TTVFaster[17]) and numerical (TTVFast[18] and Mercury[19]) n-body integrations of a system of six gravitationally interacting, co-planar planets, the initial mass estimates for the six inner planets of TRAPPIST-1, along with their orbital eccentricities, were determined.[20]
{{citation}}: Cite uses deprecated parameter |citeseerx= (help)
Source: Wikipedia. Article content is retrieved live through the MediaWiki API.
Transit-timing variation is a method for detecting exoplanets by observing variations in the timing of a transit. This provides an extremely sensitive method capable of detecting additional planets in the system with masses potentially as small as that of Earth. In tightly packed planetary systems, the gravitational pull of the planets among themselves causes one planet to accelerate and another planet to decelerate along its orbit. The acceleration causes the orbital period of each planet to change. Detecting this effect by measuring the change is known as transit-timing variations. "Timing variation" asks whether the transit occurs with strict periodicity or if there exists a variation. The first significant detection of a non-transiting planet using transit-timing variations was carried out with NASA's Kepler telescope. The transiting planet Kepler-19b shows transit-timing variation with an amplitude of 5 minutes and a period of about 300 days, indicating the presence of a second planet, Kepler-19c, which has a period that is a near-rational multiple of the period of the transiting planet. In 2010, researchers proposed a second planet orbiting WASP-3 based on transit-timing variation, but this proposal was debunked in 2012. Transit-timing variation was first convincingly detected for planets Kepler-9b and Kepler-9c and gained popularity by 2012 for confirming exoplanet discoveries. Exoplanet TOI-199c was also discovered using this method. TTV can also be used to indirectly measure the mass of the exoplanets in compact, multiple-planet systems and/or system whose planets are in resonant chains. By performing a series of analytical (TTVFaster) and numerical (TTVFast and Mercury) n-body integrations of a system of six gravitationally interacting, co-planar planets, the initial mass estimates for the six inner planets of TRAPPIST-1, along with their orbital eccentricities, were determined.
The list of exoplanets detected by the Kepler space telescope contains bodies with a wide variety of properties, with significant ranges in orbital distances, masses, radii, composition, habitability, and host star type. As of June 16 2023, the Kepler space telescope and its follow-up observations have detected 2,778 planets, including hot Jupiters, super-Earths, circumbinary planets, and planets located in the circumstellar habitable zones of their host stars. Kepler has detected over 3,601 unconfirmed planet candidates and 2,165 eclipsing binary stars. In addition to detecting planets itself, Kepler has also uncovered the properties of three previously known extrasolar planets. Public Kepler data has also been used by groups independent of NASA, such as the Planet Hunters citizen-science project, to detect several planets orbiting stars collectively known as Kepler Objects of Interest. Kepler, launched on March 7, 2009, was designed to observe a fixed portion of the sky in visible light and measure the light curves of the various stars in its field of view, looking for planets crossing in front of their host stars via the transit method. Since the launch of the spacecraft, though, both the Kepler team at NASA and independent researchers have found new ways of detecting planets, including the use of the transit timing variation method and relativistic beaming. In addition, gravitational microlensing has been proposed as a method of using Kepler to detect compact objects, such as white dwarfs, neutron stars, and black holes. Kepler has also measured the reflected light from some planets already known, discovering planets undetectable with the transit method as well as improving knowledge of the characteristics of planets already discovered. On February 26, 2014, NASA announced the discovery of 715 newly verified exoplanets around 305 stars by the Kepler Space Telescope. The exoplanets were found using a statistical technique called "verification by multiplicity". 95% of the discovered exoplanets were smaller than Neptune and four, including Kepler-296f, were less than 2 1/2 the size of Earth and were in habitable zones where surface temperatures are suitable for liquid water. On May 10, 2016, NASA announced that the Kepler mission has verified 1,284 new planets. Based on some of the planet's sizes, about 550 could potentially be rocky planets. Nine of these orbit in their stars' habitable zone.
The habitability of natural satellites is the potential of moons to provide habitats for life. Natural satellites are expected to outnumber planets by a large margin and the study of their habitability is therefore important to astrobiology and the search for extraterrestrial life. Planetary mass, atmosphere, and geology are all important factors but there are significant environmental variables specific to moons. All planetary mass moons of the Solar System are tidally locked, the most significant difference in comparison to the planetary habitability of bodies that have "cleared their neighbourhood." They also tend to have more surface area relative to volume, thus dissipating heat and atmosphere quickly, as well as orbital resonances with other moons that stabilize their orbits but can lead to a stasis inimical to natural selection. With a surficial solvent, thick atmosphere, and dominant size over satellite companions within the Saturnian system, Titan best meets the known habitability criteria within the solar system though at great distance from the sun. Research suggests that deep biospheres like that of Earth are also possible. The strongest candidates therefore are currently icy satellites such as those of Jupiter and Saturn—Europa and Enceladus respectively, in which subsurface liquid water is thought to exist. While the lunar surface is hostile to life as we know it, a deep lunar biosphere (or that of similar bodies) cannot yet be ruled out; deep exploration would be required for confirmation. Exomoons are not yet confirmed to exist and their detection may be limited to transit-timing variation, which is not currently sufficiently sensitive. It is possible that some of their attributes could be found through study of their transits. Despite this, some scientists estimate that there are as many habitable exomoons as habitable exoplanets. Given the general planet-to-satellite(s) mass ratio of 10,000, gas giants in the habitable zone are thought to be the best candidates to harbour Earth-like moons. Tidal forces are likely to play as significant a role providing heat as stellar radiation.
Sarah Ballard (born 1984) is an American astronomer who is a professor at the University of Florida. She has been a Torres Fellow at the Massachusetts Institute of Technology, a L'Oreal Fellow, and a NASA Carl Sagan Fellow. Ballard was part of a collaborative team that was the first to successfully use the transit-timing variation method. This resulted in her team's confirmation of this theoretical search procedure and the discovery of the Kepler-19 planetary system with that technique. Ballard took part in the discovery of four exoplanets (early numbered) in the Kepler spacecraft mission prior to its finding of significant quantities of planets around other stars. Ballard has spoken about her experience as a victim of sexual harassment, about imposter syndrome, and about the controversy over the proposed Thirty Meter Telescope at the Mauna Kea Observatories.
Before the 1921 destruction of Tulsa’s Greenwood District, Black residents had created a remarkable center of business and community life. The district included stores, professional offices, entertainment venues and homes owned by Black citizens. Understanding Greenwood means learning what was built—not only what was burned.
MORE →Mae Jemison, aboard Space Shuttle Endeavour in 1992.
