How fast universe expanding

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Now, a highly anticipated independent technique that cosmologists hoped would solve the conundrum is instead adding to the confusion.

In results unveiled 1 on 16 July and due to appear in the Astrophysical Journal , a team led by astronomer Wendy Freedman at the University of Chicago in Illinois presents a technique that measures the expansion using red-giant stars.

It had promised to replace a method that astronomers have been using for more than a century — but for now, the speed measurement has failed to resolve the dispute because it falls half way between the two contentious values. If the cosmic-speed discrepancy is not resolved, some of the basic theories that cosmologists use to interpret their data — such as assumptions about the nature of dark matter — could be wrong.

American astronomer Edwin Hubble and others discovered in the s that the Universe is expanding by showing that most galaxies are receding from the Milky Way — and the farther away they are, the faster they are receding.

The roughly constant ratio between speed and distance became known as the Hubble constant. For each additional megaparsec around 3.

Over the decades, astronomers substantially revised down the estimate as measurement techniques improved. A team led by Nobel laureate Adam Riess at Johns Hopkins University in Baltimore, Maryland, has made the most precise measurements so far, and its latest value is 74, with an error margin of just 1. But a separate effort in the past decade has thrown a spanner in the works. Using standard theoretical assumptions about the cosmos, they calculated the Hubble constant as The difference between But they have struggled to find a tweak to the theory that could solve the problem and still be consistent with everything that is known about the Universe.

So, by measuring how bright they appeared on photographic plates, she could calculate how far away the stars were. Freedman, Madore and Myung Gyoon Lee first pointed out in that these peaking red giants can serve as standard candles. Now Freedman had put them to work. As we unloaded from the van, I asked her about her scheduled talk. When I got to my hotel room and checked Twitter, I found that everything had changed. Things were getting surd. Adam and I then went out to dinner and we were pretty perplexed, because in what we had seen up to this point, the cepheids and TRGBs were in really good agreement.

They soon homed in on the key change in the paper: a new way of measuring the effects of dust when gauging the intrinsic brightness of TRGBs — the first rung of the cosmic distance ladder. One of the all-time greatest cosmological discoveries, cosmic expansion implies that the universe has a finite age.

Big, bright cepheids pulsate more slowly than small, dim ones just as a big accordion is harder to compress than a tiny one. And so, from the pulsations of a distant cepheid, you can read off how intrinsically bright it is. Hubble then used cepheids to deduce the distances to nearby galaxies, which, plotted against their speeds, revealed cosmic expansion.

Hubble overestimated the rate as kilometers per second per megaparsec, but the number dropped as cosmologists used cepheids to calibrate evermore accurate cosmic distance ladders. His rivals claimed a value around , based on different astronomical observations. To build a distance ladder, you start by calibrating the distance to stars of known luminosity, such as cepheids.

These standard candles can be used to gauge the distances to fainter cepheids in farther-away galaxies. Crowding by other stars can make them look brighter and thus closer. Furthermore, even supposed standard-candle stars have inherent variations due to age and metallicity that must be corrected for.

Freedman devised new methods to deal with many sources of systematic error. The H 0 value of 72 that her team published in split the difference in the versus debate. She was gracious and he softened. In its analysis, Planck found H 0 to be Tommaso Treu , one of the founders of H0LiCOW and a professor at the University of California, Los Angeles, had dreamed ever since his student days in Pisa of measuring the Hubble constant using time-delay cosmography — a method that skips the rungs of the cosmic distance ladder altogether.

Instead, you directly determine the distance to quasars — the flickering, glowing centers of faraway galaxies — by painstakingly measuring the time delay between different images of a quasar that form as its light bends around intervening matter. But while Treu and his colleagues were collecting quasar data, Freedman, Madore and their graduate students and postdocs were pivoting to tip-of-the-red-giant-branch stars.

Whereas cepheids are young and found in the crowded, dusty centers of galaxies, TRGBs are old and reside in clean galactic outskirts. Earlier this year, he, Lisa Randall of Harvard University, and others proposed a possible solution to the Hubble constant tension. Their idea — a new, short-lived field of repulsive energy in the early universe — would speed up cosmic expansion, matching predictions to observations, though this and all other proposed fixes strike experts as a bit contrived.

He later said he was half kidding. Here I am, stuck in the middle with you. Another curveball came before lunch. The researchers obtained high-resolution infrared images of each galaxy with the Wide Field Camera 3 on the Hubble Space Telescope and determined how much each pixel in the image differed from the "average" -- the smoother the fluctuations over the entire image, the farther the galaxy, once corrections are made for blemishes like bright star-forming regions, which the authors exclude from the analysis.

Neither Blakeslee nor Ma was surprised that the expansion rate came out close to that of the other local measurements. But they are equally confounded by the glaring conflict with estimates from the early universe -- a conflict that many astronomers say means that our current cosmological theories are wrong, or at least incomplete. The extrapolations from the early universe are based on the simplest cosmological theory -- called lambda cold dark matter, or? CDM -- which employs just a few parameters to describe the evolution of the universe.

Does the new estimate drive a stake into the heart of? CDM is still alive. Some people think, regarding all these local measurements, that the observers are wrong. But it is getting harder and harder to make that claim -- it would require there to be systematic errors in the same direction for several different methods: supernovae, SBF, gravitational lensing, water masers.

So, as we get more independent measurements, that stake goes a little deeper. Ma wonders whether the uncertainties astronomers ascribe to their measurements, which reflect both systematic errors and statistical errors, are too optimistic, and that perhaps the two ranges of estimates can still be reconciled.

But assuming everyone's error bars are not underestimated, the tension is getting uncomfortable. In fact, one of the giants of the field, astronomer Wendy Freedman, recently published a study pegging the Hubble constant at The latest result from Adam Riess, an astronomer who shared the Nobel Prize in Physics for discovering dark energy, reports The new value of H0 is a byproduct of two other surveys of nearby galaxies -- in particular, Ma's MASSIVE survey, which uses space and ground-based telescopes to exhaustively study the most massive galaxies within about Mpc of Earth.

A major goal is to weigh the supermassive black holes at the centers of each one. To do that, precise distances are needed, and the SBF method is the best to date, she said. Combining that distance, million light years, with extensive spectroscopic data from the Gemini and McDonald telescopes -- which allowed Ma's graduate students Chris Liepold and Matthew Quenneville to measure the velocities of the stars near the center of the galaxy -- they concluded that NGC has a central black hole with a mass nearly 3 billion times that of the sun.

The other 20 came from another survey that employed HST to image large galaxies, specifically ones in which Type Ia supernovae have been detected. Most of the 63 galaxies are between 8 and 12 billion years old, which means that they contain a large population of old red stars, which are key to the SBF method and can also be used to improve the precision of distance calculations.

In the paper, Blakeslee employed both Cepheid variable stars and a technique that uses the brightest red giant stars in a galaxy -- referred to as the tip of the red giant branch, or TRGB technique -- to ladder up to galaxies at large distances.