Astronomers at NASA and the University of Washington estimated the total internal heating rate and depth to potential subsurface oceans for 17 potentially cold ocean planets. These planets are low-mass exoplanets with surface temperatures and densities consistent with icy surfaces and large amounts of water. content. Like the icy moons of our solar system, these planets could be astrobiologically important worlds with habitable environments beneath their icy surfaces.
This artist’s impression shows Proxima b orbiting Proxima Centauri, the closest star to our solar system at just 4.23 light years. The double star Alpha Centauri AB also appears in the image between the exoplanet and Proxima itself. Image credit: M. Kornmesser / ESO.
Ocean planets have been proposed as a class of low-density terrestrial exoplanets with significant liquid water layers.
They exist in different climatic states, including ice-free, partially ice-covered, and completely frozen surfaces.
“Our analysis suggests that the surfaces of these 17 alien worlds may be covered in ice, but they are affected by internal heating due to the decay of radioactive elements and tidal forces from their host stars,” said NASA Goddard researcher Dr. Lynne Quick. “We predict that it will receive enough water to maintain its internal ocean.” Space flight center.
“Due to the amount of internal heating the planets experience, all the planets in our study may also exhibit polar volcanic eruptions in the form of geyser-like plumes.”
Dr. Quick and his colleagues examined the status of 17 confirmed exoplanets. These planets are roughly Earth-sized but less dense, suggesting they may have significant amounts of ice and water instead of dense rock.
Although the exact composition of these planets remains unknown, all initial estimates of surface temperatures from previous studies indicate that they are much cooler than Earth, and their surfaces may be covered with ice. This suggests that there is a possibility that
The authors improved their estimates of each exoplanet’s surface temperature by recalculating them using the known surface brightness and other properties of Europa and Enceladus as models.
They also estimated the total internal heating of these exoplanets by using the shape of each exoplanet’s orbit to capture the heat generated from the tides and adding it to the heat expected from radioactive activity. did.
Because oceans cool and freeze at the surface while being heated from within, estimates of surface temperature and total heating provide information about the thickness of each exoplanet’s ice layer.
Finally, they compared these numbers to Europa’s and used Europa’s estimated level of geyser activity as a conservative baseline for estimating the exoplanet’s geyser activity.
They predict surface temperatures will be up to 33 degrees Celsius (60 degrees Fahrenheit) cooler than previous estimates.
Artist’s impression of the planetary system LHS 1140. Image credit: Sci.News.
Estimated ice shell thicknesses ranged from approximately 58 m (190 ft) for Proxima b and 1.6 km (1 mi) for LHS 1140b to 38.6 km (24 mi) for LHS 1140b. MOA-2007-BLG-192Lbcompared to an estimated European average of 29 km (18 mi).
The estimated geyser activity was only 8 kg/s for Kepler 441b, 2,000 kg/s for Europa, 290,000 kg/s for LHS 1140b, and 6 million kg/s for Proxima b.
“Our models predict that oceans could be found relatively close to the surfaces of Proxima b and LHS 1140b, and that geyser activity rates could exceed those of Europa by hundreds to thousands of times. “The telescope has the best chance of detecting geological activity on these planets because of their presence,” said Dr. Quick.
“This activity can be seen when an exoplanet passes in front of its star. Certain colors of the star’s light can be dimmed or blocked by water vapor from geysers. there is.”
“If water vapor is detected sporadically and the amount of water vapor detected changes over time, it would suggest the presence of a cryovolcanic eruption.”
“Water may contain other elements and compounds, which could reveal whether it can support life.”
“Elements and compounds absorb light of certain characteristic colors, so analysis of starlight allows scientists to determine the composition of geysers and assess the potential habitability of exoplanets. Become.”
a paper Regarding the survey results, astrophysical journal.
_____
Lynne C. Quick other. 2023. Prospects for polar volcanic activity on cold ocean planets. APJ 956, 29; doi: 10.3847/1538-4357/ace9b6
Source: www.sci.news
