It has been said that all the light ever radiated by all the stars that ever existed in the history of observable universe –a bubble 14 billion light-years in radius, which represents how far we have been able to see since its beginning– is still with us, filling the universe with a sea of photons, the cosmic fog known as the extragalactic background light –providing as much illumination as a 60-watt bulb seen from 2.5 miles away.
“You know, our sun looks just like thousands of other stars in the sky. You’d never guess that there are planets going around it, and that one of those planets has people who consider themselves very intelligent. There would be no way of knowing that,” said Cornell University icon, astronomer Carl Sagan, in a 1973 interview with Rolling Stone, long before Michel Mayor and Didier Queloz announced the first discovery of a planet outside our solar system, an exoplanet, orbiting a solar-type star in our home galaxy, the Milky Way in 1995. The planet, 51 Pegasi b, a gaseous ball comparable with the solar system’s biggest gas giant, Jupiter was detected at the Haute-Provence Observatory in southern France, using custom-made instruments.
In 2018, an international team of astronomers proposed that around 8 billion to 10 billion years ago an unknown massive dwarf galaxy dubbed the “Sausage” –with a total mass in gas, stars and dark matter more than 10 billion times our sun– crashed head-on into our Milky Way galaxy, ripping the dwarf to shreds, leaving its stars moving in long, narrow needle-like radial orbits. This defining event in the early history of the Milky Way reshaped the structure of our galaxy into its warped, twisted shape shown above, with the Sausage debris scattered around the inner parts of the Milky Way, creating the ‘bulge’ at the galaxy’s center and the surrounding ‘stellar halo.’
“Hubble simply doesn’t go far enough into the infrared” to see the hidden galaxies of the early universe, said Rogier Windhorst of Arizona State University, co-author of a new study using the near-infrared capabilities of NASA’s Hubble Space Telescope to probe known quasars, ‘quasi-stellar radio sources’, in hopes of spotting the surrounding glow of their host galaxies, without significant detections, suggesting that cocoons of dust that absorb visible light within the galaxies is obscuring the light of their stars.
“Historically, our assumption has been that the region around Jupiter is fairly empty, cleaned out by the giant planet’s gravity, but our results teach us that there is a region that is constantly being fed,” said Kathryn Volk at the University of Arizona Lunar and Planetary Laboratory in 2019 about a constant source of new objects that may help explain the surprising rate of icy body impacts with Jupiter, such as the Shoemaker-Levy 9 event in 1994 when over twenty fragments of comet that collided with Jupiter were observed by astronomers at hundreds of observatories around the world.
