- 3778 - UNIVERSE - expanding at ever faster rate? The night sky may look deceptively still, but the universe is constantly expanding, which means everything keeps moving away from everything else. The space between things is expanding. A new map of the distances of tens of thousands of galaxies is helping researchers calculate the universe's age and expansion rate with unprecedented precision.
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--------------------- 3778 - UNIVERSE - expanding at ever faster rate?
The universe is thought to be about 13,800,000,000 years old.
------------------------------ Understanding the Universe
- To calculate the expansion rate of the universe, scientists use a unit of measurement known as the “Hubble constant“, which is estimated to be about 46.6 miles per second for every megaparsec, or 3.26 million light-years. That means at 3.26 billion light-years distance the galaxies away are moving away from each other at 46,600 miles per second. This rate is 167,760,000 miles per hour for galaxies separated by over 3 billion lightyears distance.
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- Eight different methods of measuring galaxy distances were used to get this expansion rate. By comparing these different methods, the scientists were able to develop the above more accurate map.
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- Researchers measured the distance between 56,000 galaxies and their velocities as they move farther away. The distances and velocities of these galaxies, many of which host hundreds of billions of stars, can provide insight into the size of the universe and help scientists pinpoint the date of the Big Bang with more precision.
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- How can something infinite be mapped?
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- Nobody knows how far the universe reaches, but to construct the expanding universe map the research team determined the distances and velocities of thousands of galaxies eight different ways. They used data from their own studies and others, with most of the data coming from the “ALFALFA HI survey” from the Arecibo Observatory in Puerto Rico.
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- Galaxies are always rotating, and the rate of that rotation, along with luminosity and other elements, such as the "barcodes" of light that scientists call spectra, can reveal the distance of each galaxy. The longer the light has been traveling through the universe the more its bandwidth is stretched out. Wider bandwidth is lower frequency, into the microwave region. This tells us how far the light has traveled.
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- The map shows the positions and real colors of 200,000 galaxies, using two decades' worth of data collected by the Sloan Digital Sky Survey. The interactive map can be downloaded for free at “ mapoftheuniverse.net “ , allowing the public to access information that was previously available only to scientists.
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- Astrophysicists around the world have been analyzing this data for years, leading to thousands of scientific papers and discoveries.
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- The survey is an effort to capture a huge proportion of the night sky through the 2.5-meter telescope at Apache Point Observatory in New Mexico. Every night for eight years, the telescope has aimed its 120-megapixel camera on 1.5 square degrees of the sky at a time, around eight times the area of the full moon, at slightly different locations, to capture a broad perspective of the universe.
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- Astronomers used these data to recreate a slice of the universe containing 200,000 galaxies. Each dot on the above map is a galaxy with billions of stars and planets. Our own galaxy, the Milky Way, is just one of these dots located at the very bottom of the map.
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- The colors on the map are created by the expansion of the universe. As the universe expands, the wavelengths of light traveling to Earth are stretched to redder regions of the electromagnetic spectrum. The more distant a light source, the more extreme this redshift.
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- At the very top of the map is the universe's first light, emitted around 13.7 billion years ago, shortly after the Big Bang, as the universe expanded and cooled enough to allow electrons to form atoms with protons. The reduction of free electrons meant that photons, individual packets of light that act as both particles and waves, were suddenly not being infinitely bounced around and were instead free to travel. In an instant, the universe effectively went from being opaque to transparent.
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- At the opposite end of the interactive map is the Milky Way, including the solar system and Earth as they exist today. The speck at the very bottom, just one pixel is our galaxy, the Milky Way, which has billions of stars and planets.
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- This is mind blowing if you try to think about it!
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- From this speck at the bottom, we are able to map out galaxies across the entire universe, and that says something about the power of astronomy.
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December 8, 2022 UNIVERSE - expanding at ever faster rate? 3778
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