T-dwarf
An object with the spectral type T (also called T dwarf or methane brown dwarf) is either a brown dwarf or young free-floating planetary-mass object. A directly imaged exoplanet with a young age can also be a T-dwarf. T dwarfs are colder than L dwarfs, but warmer than Y dwarfs. Prototype Gliese 229B The first T-dwarf discovered was Gliese 229B, which was discovered in 1995. This object had a temperature below 1000 K and showed methane (CH4), water vapor (H2O) and carbon monoxide (CO) in its spectrum. In the upper atmosphere CO is converted into CH4 and H2O, while the opposite is true for the hotter lower atmosphere. It also showed absorption due to caesium (Cs), but absorption features commonly found in M-dwarfs ( CaH, FeH, TiO, and VO) were missing. Ammonia (NH3) was included in the analysis of the spectrum. Sodium (Na) and potassium (K) are also detected in this T-dwarf. Later work found a dynamical mass of 70 ± 5 for Gliese 229B, which is much higher than the cooling ...
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Brown Dwarf
Brown dwarfs are substellar objects that have more mass than the biggest gas giant planets, but less than the least massive main sequence, main-sequence stars. Their mass is approximately 13 to 80 Jupiter mass, times that of Jupiter ()not big enough to sustain nuclear fusion of hydrogen into helium in their cores, but massive enough to emit some light and heat from the deuterium fusion, fusion of deuterium (deuterium, 2H). The most massive ones (> ) can lithium burning, fuse lithium (lithium-7, 7Li). Astronomers classify self-luminous objects by Stellar classification#Spectral types, spectral type, a distinction intimately tied to the surface temperature, and brown dwarfs occupy types M (2100–3500 Kelvin, K), L (1300–2100 Kelvin, K), T (600–1300 Kelvin, K), and Y ( 80 ''M''J), which have spectral classes L2 to L6. Spectral class T As GD 165B is the prototype of the L dwarfs, Gliese 229B is the prototype of a second ne ...
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L Dwarf
An object with the spectral type L (also called L-dwarf) can be either a low-mass star, a brown dwarf or a young rogue planet, free-floating planetary-mass object. If a young exoplanet or planetary-mass companion is detected via direct imaging, it can also have an L spectral type, such as Kappa Andromedae b. Spectral characteristics Before 2MASS there were only six known objects with a spectral type later than M9.5V. With the discovery of 20 new late-type objects it was necessary to define the L-type and T-dwarf, T-type spectral types. Davy Kirkpatrick, Kirkpatrick et al. defined the two spectral types in 1999. In these L-dwarfs the metallic Oxide, oxides (Titanium(II) oxide, TiO, Vanadium(II) oxide, VO), which are present in red dwarfs, late M-dwarfs, are replaced with metallic Hydride, hydrides (e.g. Chromium(I) hydride, CrH, Iron(I) hydride, FeH) and neutral alkali metal, alkali metals (e.g. potassium, K, rubidium, Rb, cesium, Cs). The transition between L- and T-dwarfs is de ...
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Rogue Planet
A rogue planet, also termed a free-floating planet (FFP) or an isolated planetary-mass object (iPMO), is an interstellar object of planetary mass which is not gravitationally bound to any star or brown dwarf. Rogue planets may originate from planetary systems in which they are formed and later ejected, or they can also form on their own, outside a planetary system. The Milky Way alone may have billions to trillions of rogue planets, a range the upcoming Nancy Grace Roman Space Telescope is expected to refine. Some planetary-mass objects may have formed in a similar way to stars, and the International Astronomical Union has proposed that such objects be called sub-brown dwarfs. A possible example is Cha 110913−773444, which may either have been ejected and become a rogue planet or formed on its own to become a sub-brown dwarf. Terminology The two first discovery papers use the names isolated planetary-mass objects (iPMO) and free-floating planets (FFP). Most astronomical ...
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SDSS 1624+00
SDSS 1624+00 (also known as SDSSp J162414.371+002915.6) is the first T dwarf discovered in the field, meaning it does free-float in space and does not belong to a group of stars. The object was discovered after Gliese 229B and at around the same time Gliese 570D was discovered. SDSS 1624+00 was discovered in 1999 with preliminary data of the Sloan Digital Sky Survey. It was selected because of its extreme red color (i-z=3.77 ±0.21 mag). Optical spectroscopy was obtained with the Apache Point 3.5 m telescope and near-infrared photometry and spectroscopy with the United Kingdom Infrared Telescope. The spectrum showed absorption due to water vapor, methane and caesium and the spectrum was similar to Gliese 229B, but with SDSS 1624+00 showing a stronger potassium line. It is 1.2 mag fainter than Gliese 229B, which helped to constrain the distance to around 10 parsec. A red spectrum was obtained with the Keck Observatory. The researchers found that SDSS 1624+00 is likely w ...
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Y Dwarf
An object with a spectral type Y (also called Y dwarf) is either a brown dwarf or a rogue planet, free-floating planetary-mass object. They have temperatures below around 500 Kelvin (227°C; 440°F) and are colder than T dwarf, T-dwarfs. Y-dwarfs have a similar spectrum when compared to the giant planet Jupiter. Early theories and discovery When the spectral classes of L dwarf, L dwarfs and T dwarf, T dwarfs were defined it was mentioned that the letter Y was available for an additional spectral class. In the early 2000s it was already theorized that objects "beyond the T dwarfs" should exist and that these objects would bridge the gap between T dwarfs and the giant planet, giant planets of the Solar System. Objects colder than T dwarfs would primarily emit infrared as thermal radiation, so observations and discoveries with infrared telescopes such as Wide-field Infrared Survey Explorer, WISE, Spitzer Space Telescope, Spitzer and James Webb Space Telescope were anticipated. Model ...
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H Band (infrared)
In infrared astronomy, the H band refers to an atmospheric transmission window centred on 1.65 micrometres with a Full width at half maximum of 0.35 micrometresIan McClean, Electronic Imaging in Astronomy, Second Edition, Springer, 2008. (in the near-infrared). Save for a limited amount of absorption by water vapor, Earth's atmosphere is highly translucent at the wavelengths covered by the H band. The window is also notably less likely to be contaminated by infrared excess than other bands. The band is useful for a range of infrared observations including the imaging of sunspots, spectroscopic investigation of late-type stars, and imaging planetary phenomena such as extraterrestrial vortices or volcanic activity in the Solar System. In addition stellar atmospheres are highly transparent in the H band and stellar light in the window originates from deeper in the stellar atmosphere than any other band. It also includes within it access to several sets of spectral lines including f ...
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K Band (infrared)
In infrared astronomy, the K band is an atmospheric transmission window centered on 2.2  μm (in the near-infrared 136 THz range). HgCdTe-based detectors are typically preferred for observing in this band. Photometric system In astronomy, a photometric system is a set of well-defined passbands (or optical filters), with a known sensitivity to incident radiation. The sensitivity usually depends on the optical system, detectors and filters used. For each photometric s ...s used in astronomy are sets of filters or detectors that have well-defined windows of absorption, based around a central peak detection frequency and where the edges of the detection window are typically reported where sensitivity drops below 50% of peak. Various organizations have defined systems with various peak frequencies and cutoffs in the K band, including , and KS, and Kdark. Table 1., Filter sets used at Mauna Kea and the South Pole. See also * Absolute magnitude References Electromagn ...
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Sloan Digital Sky Survey
The Sloan Digital Sky Survey or SDSS is a major multi-spectral imaging and spectroscopic redshift survey using a dedicated 2.5-m wide-angle optical telescope at Apache Point Observatory in New Mexico, United States. The project began in 2000 and was named after the Alfred P. Sloan Foundation, which contributed significant funding. A consortium of the University of Washington and Princeton University was established to conduct a redshift survey. The Astrophysical Research Consortium (ARC) was established in 1984 with the additional participation of New Mexico State University and Washington State University to manage activities at Apache Point. In 1991, the Sloan Foundation granted the ARC funding for survey efforts and the construction of equipment to carry out the work. Background At the time of its design, the SDSS was a pioneering combination of novel instrumentation as well as data reduction and storage techniques that drove major advances in astronomical observations, dis ...
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SDSS 1021
SDSS may refer to: * Sloan Digital Sky Survey, a major multi-filter imaging and spectroscopic redshift survey * Social Democratic Party of Slovakia * Spatial Decision Support System, a GIS based decision aiding system * Independent Democratic Serb Party, a political party of Croatian Serbs (''Samostalna demokratska srpska stranka'' in Serbo-Croatian) * South Delta Secondary School South Delta Secondary (SDSS) is a public high school in Tsawwassen, British Columbia, Canada. There are approximately 1,500 students enrolled in each grade 8 through 12 (as of 2019/2020). Graduation rates in the years 2005 to 2010 vary between 9 ...

Potassium
Potassium is a chemical element; it has Symbol (chemistry), symbol K (from Neo-Latin ) and atomic number19. It is a silvery white metal that is soft enough to easily cut with a knife. Potassium metal reacts rapidly with atmospheric oxygen to form flaky white potassium peroxide in only seconds of exposure. It was first isolated from potash, the ashes of plants, from which its name derives. In the periodic table, potassium is one of the alkali metals, all of which have a single valence electron in the outer electron shell, which is easily removed to create cation, an ion with a positive charge (which combines with anions to form salts). In nature, potassium occurs only in ionic salts. Elemental potassium reacts vigorously with water, generating sufficient heat to ignite hydrogen emitted in the reaction, and burning with a lilac-flame color, colored flame. It is found dissolved in seawater (which is 0.04% potassium by weight), and occurs in many minerals such as orthoclase, a ...
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SDSS 0837
SDSS may refer to: * Sloan Digital Sky Survey, a major multi-filter imaging and spectroscopic redshift survey * Social Democratic Party of Slovakia * Spatial Decision Support System, a GIS based decision aiding system * Independent Democratic Serb Party, a political party of Croatian Serbs (''Samostalna demokratska srpska stranka'' in Serbo-Croatian) * South Delta Secondary School South Delta Secondary (SDSS) is a public high school in Tsawwassen, British Columbia, Canada. There are approximately 1,500 students enrolled in each grade 8 through 12 (as of 2019/2020). Graduation rates in the years 2005 to 2010 vary between 9 ...