August 03, 2020
Enjoy these interesting stories from the scientific community.
*-- Astronomers track down 'lost' worlds spotted but unconfirmed by TESS survey --*
One by one, an international team of astronomers is rediscovering "lost" worlds first spotted, but unconfirmed, by NASA's TESS telescope.
One of those rediscovered worlds, described this week in the Astrophysical Journal Letters, is NGTS-11b, an exoplanet with the size and mass of Saturn but an orbit of just 35 days. NGTS-11b circles a star located 620 light-years away from Earth.
NASA's TESS telescope usually scans sections of the sky for 27 days. The observatory's images often capture transits, the dip in starlight that happens when an exoplanet orbits across the face of its host star.
But because many orbits take more than 27 days, TESS regularly captures just one transit. To confirm the presence of an exoplanet is a distant star system, and not an asteroid or some other anomaly, astronomers must observe a second transit.
Without a second transit, many of the exoplanet candidates initially spotted by TESS are effectively "lost," like an unstudied artifact collecting dust in a museum closet.
Scientists with the Next-Generation Transit Survey are using single-transits captured by TESS as a jumping off point for discovering potentially habitable exoplanets.
"By chasing that second transit down we've found a longer period planet. It's the first of hopefully many such finds pushing to longer periods," lead study author Samuel Gill said in a news release.
"These discoveries are rare but important, since they allow us to find longer period planets than other astronomers are finding. Longer period planets are cooler, more like the planets in our own solar system," said Gill, a researcher at the University of Warwick.
Planets with more intimate orbits around their host stars are typically too hot to support life, whereas exoplanets with longer orbital periods -- those spotted but unconfirmed by TESS -- are more likely to have life-supporting temperatures.
With average surface temperatures upwards of 160 degrees Celsius, NGTS-11b is still too hot to host liquid water and support life, but its not as intolerable as most exoplanets initially discovered by TESS.
"While we have discovered many planets that orbit close to their host star, we know of fewer at longer periods and cooler temperatures, which makes NGTS-11b an interesting find that takes us one step closer to finding planets in the Goldilocks zone," said study co-author Ed Gillen.
"Longer period planets like NGTS-11b may help us to better understand the various evolutionary processes that planetary systems undergo both during and after their formation," said Gillen, a researcher with the University of Cambridge's Cavendish Laboratory.
*-- Scientists find 'ring of fire' on surface of Venus --*
Scientists have discovered a "ring of fire" on the surface of Venus -- a belt of active mantle plumes.
Unlike Earth's Ring of Fire, which is fueled by plate tectonics, the ring of fire on Venus is caused by vertical hotspot volcanism, the same phenomenon that produced the Hawaiian Islands.
Researchers discovered the new ring of fire after conducting an extensive survey of Venus' coronae population. The team of scientists detailed their discovery this week in the journal Nature Geoscience.
More than 30 years ago, NASA's Magellan spacecraft captured images of dozens of unusual circular structures, called coronae, on the surface of Venus. Ever since, scientists have been trying to decipher their geological origins and the underlying conditions that shape them.
Planetary scientists agree that coronae are produced by mantle plumes.
Hot molten rock is carried upwards by convection currents, forming a mushroom-like shape at the top. As the rising column of molten rock melts the crust, the head of the plume expands, forming the circular structure.
Eventually, the plume may sink back down beneath the rim of the coronae, causing the structure to contract and crack.
Despite the seemingly homogeneous formation process, the topography coronae isn't uniform. For the new research, scientists used computer models to study variation in surface topography of different coronae and suss out links to geological commonalities beneath the surface.
"Every corona structure has a specific signature that indicates what is going on beneath it," Anna Gülcher, a doctoral student at ETH Zurich, said in a news release.
Coronae positioned above active mantle plumes look different than coronae situated atop an inactive plume that has sunk and cooled.
When researchers classified and mapped the two different types, they found the majority of coronae above active mantle plumes were situated along a continuous belt -- a kind of ring of fire, only fueled by volcanism.
As for why the coronae are organized in this pattern, and what such behavior says about Venus' mantle, researchers aren't sure.
With more observational data and more powerful simulations, researchers said they hope to delve deeper into the origins and evolution of Venus' coronae-forging mantle plumes.
According to the study's authors, Venus could serve as a model for studying the kind of hotspot volcanism that may have dominated early Earth.