22 : Cosmic Collisions BETTER
NASA has selected proposals for four missions that would study cosmic explosions and the debris they leave behind, as well as monitor how nearby stellar flares may affect the atmospheres of orbiting planets. googletag.cmd.push(function() googletag.display('div-gpt-ad-1449240174198-2'); ); Following detailed evaluations, the agency intends to select two proposals in 2021 to be the next astrophysics missions under the Explorers Program. The selected missions will be targeted for launch in 2025.
22 : Cosmic Collisions
"These promising proposals under the Explorers Program bring out some of the most creative, innovative ways to help uncover the secrets of the universe," said Thomas Zurbuchen, associate administrator of the agency's Science Mission Directorate in Washington. "From studying stars and planets outside our solar system to seeking answers to the largest cosmic mysteries, I look forward to the breakthrough science from these modest size missions."
Protected by the umbrella of the atmosphere, Earth speeds through a cosmic rain of comets, asteroids, meteors, dust and other rubble left over from the creation of the solar system. There may be 100 billion comets in all, most clustered in a loose shell of debris called the Oort Cloud about 1 1/2 light years from the sun. Each comet, with a nucleus up to 30 miles in diameter, is embedded in a cloud of gas and dust, moving in a highly elliptical orbit around the sun.
Last August, the comet Swift-Tuttle, its orbit perturbed by Jupiter and other planets, passed close enough to Earth to cause one of the most intense meteor storms in a century as the planet brushed its tail. NASA was worried enough to postpone the launch of a space shuttle until the danger passed and took precautions to safeguard its orbiting Hubble telescope from collisions.
The cosmic origins of elements heavier than iron are mysterious. One elemental birthplace came to light in 2017 when two neutron-rich dead stars collided and spewed out gold, platinum and other hefty elements (SN: 10/16/17). A few years later, a smashup of another neutron star and a black hole left scientists wondering which type of cosmic clash was the more prolific element foundry (SN: 6/29/21).
Still, the ultimate element factory ranking remains up in the air. The scientists compared just these two types of collisions, not other possible sources of heavy elements such as exploding stars (SN: 7/7/21).
Finding the heavy element strontium in the afterglow of a neutron star merger (illustrated) provides the most direct evidence yet that these collisions set off an exotic chain of chemical reactions called the r-process.
Kilonovas are rare, massive explosions caused by the catastrophic collisions between neutron stars, which are the incredibly dense remnants of exploded stars, or collisions between neutron stars and black holes.
The merger poses no real danger of destroying Earth or our solar system, researchers said. The stretches of empty space separating the stars in the two galaxies will remain vast, making any collisions or serious perturbations unlikely. 041b061a72