Propinqua

Propinqua is a L-type brown dwarf located within the constellation of Pegasus, and it is the closest procedurally generated object in terms of distance to Earth at about 8.04 light years. It has an absolute magnitude of about 17ᵐ82 despite its propinquity to Earth, consequently being invisible to the naked eye. Propinqua's planetary system is comprised of 3 known exoplanets, 3 candidate exoplanets, and an dust disc belt located in the inner region.
==Discovery==
Propinqua was discovered on February as a potential nearby object detected from an ground-based observatory by directly imaging it. It's distance was measured later using the stellar parallax method, which is a distance measurement technique commonly used around nearby objects to determine its distance to Earth by an object's shift in position in the night sky as the Earth travels half way around the Sun by about 6 months.
==Characteristics==
Propinqua has a diameter of 0.1222±0.004 D☉, a mass of 0.63507±0.005 M♃ and a density of 373.56 g/cm³. These physical characteristics are quite the norm for an average L-type brown dwarf as well they are dim and a hassle to observe as Propinqua has a luminosity of 6.3512·10⁻⁶ L☉ and an absolute magnitude of 17ᵐ82. Hα emissions are identified on Propinqua, suggesting a possibility of a chromospheric activity. It also has a rotational period of 5ʰ58ᵐ and a temperature of 1865 K.
===Aurorae===
Propinqua was found to possess an aurorae by a team of astronomers using a centimeter-wavelength radio observatory in April. The cause of its existence is not yet fully understood, but a nearby orbiting exoplanet may emit an inundation of materials through volcanic activity captured by Propinqua's strong magnetic field and flowing them down into the atmosphere, where it stimulates the methane molecules, glowing and producing an aurorae. It's mainly pink in color, and it's a million times more powerful than the aurorae on Earth.
==Planetary system==
Proqinqua's planetary system consists of 3 known exoplanets, 3 unconfirmed exoplanets and an dust disc located in the inner region as mentioned earlier. All the exoplanets are suspected to be unable to host life and the inner exoplanets are expected to be tidally locked with their own parent brown dwarf according to computer models and simulations.
===Confirmed exoplanets ===
The first discovered exoplanets orbiting Propinqua are Proqinqua b and c. They were discovered by using a ground-based observatory, and detected anomalies alone couldn't be explained by stellar activity, suggesting the presence of an orbiting exoplanet. After further analysis and using radial velocity, both exoplanets were confirmed to have been discovered, and they announced their discovery in mid-October. Both exoplanets may be super-Earths or mini-Neptunes according to their measured minimum masses, and both are too cold to support life due to the cold nature of L-type brown dwarfs.
In late March, another exoplanet was discovered by accident as the ground-based observatory was studying the two discovered exoplanets. It's given a label as Propinqua d and to further confirm this, the candidate exoplanet was inspected more with radial velocity for two years, and the team discovered the signal spike that periodicity repeats for 275 days or 9 months detected in radial velocity. As such, it's at last confirmed and announced to the public. It may be rocky unlike the first two based on their reported minimum mass. It orbits farther out than Proqinqua b and c and similarly has a frigid temperature like the two.
===Unconfirmed exoplanets===
Propinqua is known to host orbiting unconfirmed exoplanets that are not yet confirmed to be false positives, although one exoplanet, Propinqua e, was a former refuted exoplanet. The exoplanet was discovered in June using radial velocity, a common method to find exoplanets around stars. Although further analysis of the exoplanet suggests the weak 2.5-day periodic signal spike might've instead originated from chromospheric activity due to its insufficient data from the signal and its sudden disappearance doesn't contribute its confirmation. Later on, a dust disc was discovered relatively near the brown dwarf. Its inner edge lies close to the orbit of Propinqua e, which could support its existence, and computer models and simulations further back up the exoplanet's probable existence as it doesn't dissipate the dust disc but instead, keeping the disc stable though special orbital resonances. If its existence were to be confirmed, its surface condition could be the same as the Galilean moons, despite being the innermost exoplanet.
Two years after the discovery of Propinqua e, two candidate exoplanets were detected with the same technique known as radial velocity. They are known as Propinqua f and g with a 93 and 434 day signal. Albeit no evidence of the signal has been found again, it more closely favors spurious effects emitting from Propinqua. Both exoplanets orbit Propinqua at a much greater distance, and the estimated minimum mass may indicate it might be a super-Earth or a mini-Neptune.
===Dust disc===
A team of astronomers using an astronomical interferometer detected a dust belt surrounding Propinqua at a distance to its brown dwarf of about 0.01-0.02 AU. It lies inside the orbit of Propinqua b, and its inner edge seems to end on the orbit of an unconfirmed exoplanet, Propinqua e, suggesting its existence could be true. It has a relatively cold temperature despite its propinquity to its brown dwarf, at about -100 °C.
The Propinqua planetary system
Exoplanets	Mass 	Semi-major axis 	Orbital period 	Eccentricity
e (?) 	≥0.2±0.1 M🜨 	0.0143 AU +0.00084-0.00095	2.540 days +0.011-0.016 	0.001 +0.0069-0.0042
Dust disc 	— 	~0.01-0.02 AU 	— 	—
b 	≥1.45±0.4 M🜨 	0.0255 AU +0.021-0.026 	6.064 days +0.041-0.035 	0.06 +0.053-0.067
c 	≥0.54±0.2 M🜨 	0.0618 AU +0.085-0.088 	22.892 days +0.021-0.026	0.001 +0.02-0.031
f (?) 	≥1.77±0.51 M🜨	0.1586 AU +0.084-0.073 	93.660 days +0.073-0.081	0.006 +0.06-0.07
d 	≥1.26±0.36 M🜨	0.3254 AU +0.012-0.016 	275.3 days +0.049-0.052 	0.002 +0.01-0.02
g (?) 	≥1.03±0.11 M🜨	0.441 AU +0.11-0.12 	1.19 years +0.24-0.22 	0.081 +0.2-0.09
==Gallery==
File:Propinqua-001.png|Artist impression of Propinqua, with its discovered aurorae visible for the favor of highlighting it.
File:Propinqua-002.png|Artist impression of the dust disc surrounding Propinqua. Propinqua e, b and c are visible from this image.
File:Propinqua-003.jpg|Artist impression of all the confirmed and candidate exoplanets of Propinqua, in order of distance. (Note such exoplanet appearances may not be accurate as it's partially based on the available data, although ring systems and liquid bodies on the surface are not discovered yet in the system as it's only in terms of aesthetic. )
File:Propinqua-004.png|Artist impression of a Propinqua c's surface. Propinqua b eclipses Propinqua as seen from the surface.
Category:Procedural objects
Category:Objects
Category:Brown dwarfs
Category:Planetary system