Small uranium crystals in the nuclei of white dwarf stars could trigger nuclear reactions that destroy stars Emily Conover reported in “Uranium snowflakes can cause supernovae” (SN: 24/04/21, p. 5).
Two main types, or isotopes, of uranium on Earth are uranium-238 and uranium-235. But only uranium-235 is fissile or can withstand a fission chain reaction, reader Leon Maya observed, and this isotope is less common. Maya I was wondering if the relationship between isotopes also extends to white dwarfs.
The short answer is yes, Conover of. Since uranium-235 is fissile, it is the isotope that could cause explosions in white dwarfs. And because it decays faster than uranium-238, uranium-235 is usually less abundant, either on Earth or in white dwarfs.
In general, scientists think that much of the uranium present on planets and stars was formed from neutron star fusions (SN: 11/11/17, p. 6). The Earth has a low concentration of uranium-235 because the fusion that forged its uranium occurred a long time ago, Conover of. "But a white dwarf that formed shortly after the fusion of a neutron star would have a significantly larger uranium-235 fraction than Earth's."
Tuning the cosmos
A cluster of distant galaxies emits an unusual radio wave pattern that is shaped like a giant jellyfish. Ken Croswell reported in “‘ USS Jellyfish ’is a cosmic rarity” (SN: 24/04/21, p. 10).
Astronomers can detect the cluster at frequencies similar to those of FM radio stations, Croswell reported. Reader Mike Neary We wonder why researchers consider these radio frequencies low, given that frequencies reside in the “very high frequency” band of the International Telecommunication Union, which ranges from 30 to 300 megahertz.
Radio frequencies from 30 to 300 MHz are high for the Earth but low for the cosmos, Croswell of. Take the low frequency matrix or LOFAR. This network of radio telescopes detects cosmic frequencies between 10 and 240 MHz, the lowest frequencies observable from Earth. In contrast, the best-known frequency in radio astronomy, emitted by hydrogen atoms in space, is 1,420 MHz, a wavelength of 21 centimeters.
The video killed the radio star
Zoom and the COVID-19 pandemic helped open a new era of video calling, a technology consumers had rejected for decades. Anushree Dave reported in "How long did it take the videophone to pick up?" (SN: 24/04/21, p. 22).
Several readers reflected on the social impact of technology and what the video call could mean for the future.
Reader Leah O & # 39; Connor praised the benefits of video calling for deaf or hard of hearing people. “Zoom and some other platforms now have computer-generated subtitles that are almost better than live subtitles,” he wrote. "The video call also allows for lip reading and American sign language … I hope the video call never goes away."
Although many people relied on the video call during the pandemic to foster a sense of togetherness and community, reader Mike Bushroe meditated on the negative associations with technology that some people might develop. People can learn to connect video calls with pandemic trauma, Bushroe observed, including the persecution of businesses and public places, the isolation of loved ones, the economic impact of all lost jobs, and the risk of getting caught and possibly dying from the virus. Those negative associations can persist long after the pandemic, and people may need to be cured of the trauma to “start thinking about meetings and Zoom meetings solely on their own merits,” he wrote.
While many readers have been waiting for the future of video calling, From Dave reminded the story to the reader A. Michael Noll of his past as a researcher at Bell Telephone Laboratories and AT&T. "I posted a lot about the Picturephone and worked in video conferencing (technology) in the seventies" Noll he wrote. He even contributed to the videophone sequence in the 1968 film 2001: A Space Odyssey.