Gliese 357 d

{{short description|Goldilocks Super-Earth orbiting Gliese 357}}

{{Infobox planet

| name = GJ 357 d

| image = 300px

| caption =

| apsis =

| discovery_ref =

| discoverer = Rafael Luque, Diana Kossakowski

| discovery_site = TESS

| discovered = 2019

| discovery_method = Radial velocity

| alt_names =

| periastron =

| apoastron =

| semimajor = {{Val|0.204|0.015|ul=AU}}

| avg_speed =

| eccentricity = ≈{{nowrap|0.033 ± 0.057}}

| period = {{Val|55.70|0.05|ul=days}}

| inclination = <{{Val|40|ul=deg}}

| angular_dist =

| long_periastron =

| time_periastron =

| semi-amplitude =

| mean_radius =

| surface_area =

| volume =

| density =

| mass = {{Val|6.1|1.0|ul=Earth mass}} {{Val|7.20|1.07|u=Earth mass}}

| surface_grav =

| escape_velocity =

| albedo =

| single_temperature = {{convert|219.6 ± 5.9|K|C F||lk=on}}

| star = Gliese 357

}}

Gliese 357 d is an exoplanet, considered to be a "Super-Earth" within the circumstellar habitable zone of its parent star.{{cite web|last=Falconer|first=Rebecca|url=https://www.axios.com/super-earth-31-light-years-away-may-support-life-d1d0298d-3c82-4f99-a4af-22774fc1ed70.html|title=Newly uncovered super-Earth 31 light-years away may be habitable|website=Axios|date=2019-08-01|access-date=2019-08-04|archive-date=2019-12-18|archive-url=https://web.archive.org/web/20191218061126/https://www.axios.com/super-earth-31-light-years-away-may-support-life-d1d0298d-3c82-4f99-a4af-22774fc1ed70.html|url-status=live}}{{Cite web|url=https://www.nbcnews.com/mach/science/potentially-habitable-super-earth-discovered-just-31-light-years-away-ncna1037491|title=Potentially habitable 'super-Earth' discovered just 31 light-years away|website=NBC News|date=31 July 2019 |language=en|access-date=2019-08-01|archive-date=2019-07-31|archive-url=https://web.archive.org/web/20190731230808/https://www.nbcnews.com/mach/science/potentially-habitable-super-earth-discovered-just-31-light-years-away-ncna1037491|url-status=live}}{{Cite web|url=http://www.nasa.gov/feature/goddard/2019/confirmation-of-toasty-tess-planet-leads-to-surprising-find-of-promising-world|title=NASA's TESS Helps Find Intriguing New World|last=Garner|first=Rob|date=2019-07-30|website=NASA|access-date=2019-08-01|archive-date=2019-08-01|archive-url=https://web.archive.org/web/20190801045621/https://www.nasa.gov/feature/goddard/2019/confirmation-of-toasty-tess-planet-leads-to-surprising-find-of-promising-world/|url-status=live}} The planet orbits Gliese 357, 31 light-years from the Solar System,{{Cite web|url=https://scitechdaily.com/tess-discovers-habitable-zone-planet-in-gj-357-system/|title=TESS Discovers Habitable Zone Planet in GJ 357 System|last1=Reddy|first1=Francis|last2=Center|first2=NASA’s Goddard Space Flight|date=2019-07-31|website=SciTechDaily|language=en-US|access-date=2019-08-01|archive-date=2019-08-01|archive-url=https://web.archive.org/web/20190801162521/https://scitechdaily.com/tess-discovers-habitable-zone-planet-in-gj-357-system/|url-status=live}} The system is part of the Hydra constellation.

The planet was discovered by the TESS team and announced in July 2019. The data confirming the presence of the planet was uncovered in ground-based observation dating back to 1998 while confirming the TESS detection of Gliese 357 b, a “hot earth” that orbits much closer to the parent star. Even though Gliese 357 d is 20% closer to Gliese 357 than Earth is to the Sun, Gliese 357 is much smaller than the Sun, receiving only as much energy as Mars. As a result, it is estimated that the average temperature is -64°F (-53°C), but this temperature is survivable for humans; if there is a thick enough atmosphere, the actual temperature could be much higher. If humans traveled there using modern spacecraft, it would take them about 660,000 years to get there.{{efn|Calculated assuming the spacecraft travels at 14 km/s. For comparison, the New Horizons spacecraft is exiting the solar system at a velocity of 13.7 km/s as of June 2024.}} The planet is 6.1 times more massive than Earth and 2.3 times Earth's size.{{Cite web|title=plot_GJ_357.png|date=2019-09-03|publisher=Planetary Habitability Laboratory|url=https://www.hpcf.upr.edu/~abel/phl/hec2/splots/plot_GJ_357.png}}