One of the most well known telescopes to ever be launched into space is the Hubble Space Telescope. For decades, it has been a tool used to measure a certain phenomena first observed by the astronomer the telescope was named after. It is used to measure the rate at which the universe is expanding.
It is the most precise measurement of the rate of expansion yet made, and it confirms something that’s been bothering astronomers for a while. The universe appears to be expanding faster than our measurements of the cosmic background radiation indicate it should be, suggesting either one of the measurements is wrong, or the expansion is being influenced by an unknown force.
As the universe expands, galaxies get further apart. Investigations into the way this is happening have been central to some of the most important discoveries in cosmology over the last century, but it seems we’re not done yet.
We can precisely measure the rate at which a galaxy is moving away from us from how much the wavelength of its light has stretched (known as red shift). Measuring the distance is harder, relying on the brightness of specific stars and supernovas known as “standard candles”. Comparing their brightnesses can indicate distance.
NGC 3972 is one of the galaxies whose Cepheid variable stars were studied to help measure the expansion of the universe. NASA, ESA, A Reiss (STScl/JHU)
Using Hubble’s more exact measurements of certain standard candles, a paper to be published in The Astrophysical Journal reports the Hubble constant, a measure of the expansion of the universe, as 67 (42 miles) kilometers per second per megaparsec. This means that for every additional million parsecs (3.3 million light-years) away from us a galaxy is, its speed increases by 67 kilometers (42 miles) per second.
The problem is this figure is 9 percent larger than the value we calculate using observations of the situation shortly (378,000 years being “shortly” to cosmologists) after the Big Bang. This is based on the Planck satellite’s measurements of the cosmic background radiation created at that time, processed using models of how this should’ve changed as the universe evolved.
Previous estimates of the current Hubble constant had also been higher than that derived from the Planck data, but there was uncertainty in the measurements. Using new methods to calibrate the brightness of Cepheid variables, the standard candles used to measure relatively nearby galaxies, Hubble decreased its uncertainty range to 2.3 percent. Getting the Hubble constant accurate to within 10 percent was one of Hubble’s original goals, so this dramatically exceeds that. With this newfound precision, the chance of the current and early universe expansions aligning drops to one in 5,000, which seems a bit low to rely on.
Three steps astronomers used to measure the universe’s expansion rate: 1) Using Hubble to measure the distances of stars called Cepheid variables, via parallax. 2) Applying the calibrations from these to Cepheids in nearby galaxies that have recently hosted Type Ia supernovas. 3) Knowing the distances to these supernovas, calibrating this to measure the distances to galaxies so distant we can’t see the Cepheids. NASA, ESA, A. Feild (STScl), and A. Reiss (STScl/JHU)
Professor Adam Riess of the Space Telescope Science Institute said “Both results have been tested multiple ways, so barring a series of unrelated mistakes, it is increasingly likely that this is not a bug but a feature of the universe.” Adam shared a 2011 Nobel Prize in physics because he discovered the universe’s expansion is actually becoming faster, not slowing down. The idea promoted the concept of “dark energy.”
If this info is correct, the laws of physics could change as we know them.
Theories of “dark energy” are now gaining traction: a force pushing the acceleration of the universe’s expansion, is also accelerating itself.Some even theorize that a currently invisible type of subatomic particle, subservient to gravity but basically immune to the other 3 fundamental forces, is at play.
It’s called a sterile neutrino, and if it exists, it would travel around the speed of light and affect the evolution of the universe.
Each of these theories, if correct, would interfere with the models we use to apply the data from the early universe to today’s situation. They’d also keep many theoretical physicists busy for year.
IMAGE CRDITS iflscience.
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