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Gliese 1002 Exoplanet System

Two Earth-mass planets in the habitable zone of a nearby M-dwarf //

Gliese 1002 (GJ 1002) is a real exoplanet system consisting of an M5.5V red dwarf and two known planets. The star is located a fairly close 15.8 light years from Earth, with 12% of the mass and 13.7% of the radius of the Sun. Its surface temperature is a cool 3024 K and outputs light at only 0.14% of solar luminosity. GJ 1002's age has not yet been measured, but it exhibits low flare activity, very weak X-ray emissions and a slow 126-day rotation period, all indicative of an older star.

The two planets of GJ 1002 were discovered in 2022 and are termed GJ 1002 b and GJ 1002 c. They are thought to be terrestrial in origin, with calculated minimum masses of 1.08 times and 1.36 times Earth respectively. GJ 1002 b is the inner planet with a 10.3-day orbit, roughly half of GJ 1002 c's 21.2-day trek. Both objects reside in the habitable zone of their host star and are theoretically capable of hosting liquid water. However, debate is ongoing as to whether low-mass red dwarf stars can really sustain habitable planets: intense stellar flares in their youth can strip away planetary atmospheres and it is also not clear if they output sufficient ultraviolet light to kickstart the photochemical reactions for life. The GJ 1002 system could help us answer these questions once next-generation observatories are operational for follow-up atmospheric studies. Lastly, there are hints in existing data of a much more massive companion planet in a wider orbit; other Earth-mass planets towards the outer edge of the habitable zone are also not ruled out. Whatever the case, the story of this exoplanet system isn't likely to be over anytime soon.

In this simulation, characteristics of the GJ 1002 system are replicated from literature wherever possible or inferred in cases of knowledge gaps:

• I've envisioned GJ 1002 b as a tidally-locked cool desertic terra with an average temperature of ~214 K. While it is in the habitable zone, stellar flares from a young GJ 1002 soon depleted it of its initial water, leaving a barren and lifeless world. GJ 1002 b was able to recover some of its atmosphere but is now dominated by rocky plateaus overlooking its vast plains of regolith, disturbed only by the wind and the occasional dust storm. The cold of its night side permits carbon dioxide and other gases to precipitate from the atmosphere, encrusting half the planet in snow.
  
• I've envisioned GJ 1002 c as a tidally-locked temperate marine terra with an average temperature of ~280 K. It originally formed as an ocean planet and despite also losing a large proportion of its water, it was more successful in replenishing its stocks through a combination of sustained geology, underground aquifers and a robust magnetic field. Its most prominent surface feature is huge canyons spanning thousands of kilometres, sometimes splitting entire continents in half. While being further from its star, GJ 1002 c possesses a thicker atmosphere with a stronger greenhouse effect, allowing it to experience warmer temperatures. That said, the night-side remains a cold ~190 K.

LHS 2, JP11 5942, PLX 9.0, USNO 210, FBS L 10-3, Karmn J00067-075, PLX 9.01, WISEA J000642.61-073237.0, FBS 0004-077, 2MASS J00064325-0732147, PM 00042-0747, Zkh 3, GEN# +9.80158027, NLTT 248, TIC 176287658, [RHG95] 19, G 158-27, NSV 15022, UBV M 53816, Gaia DR3 2441630500517079808, GJ 1002, 8pc 213.00, UCAC4 413-000170, Gaia DR2 2441630500517079808.

• Mascaeño, A.S., González-Álvarez, E., Osorio, M.Z., Lillo-Box, J., Faria, J.P., Passegger, V.M., Hernández, J.G., Figueira, P., Sozzetti, A., Rebolo, R. and Pepe, F., 2023. Two temperate Earth-mass planets orbiting the nearby star GJ 1002. Astronomy & Astrophysics, 670, p.A5.