The Hubble constant is named after 20th Century Carnegie astronomer Edwin P.Hubble, who astonished the world by discovering that our universe is expanding now and has been growing continuously since its inception. Astronomers now know that the universe exploded into being in a Big Bang about about 13.7 billion years ago. Determining Hubble's constant, a direct measurement of the rate of this continuing expansion, is critical for gauging the age and size of our universe.
Spitzer's new measurement, which took advantage of long-wavelength infrared instead of visible light, improves upon a similar, seminal study from NASA's Hubble Space Telescope by a factor of three, bringing the uncertainty down to only three percent, a giant leap in accuracy for a cosmological measurement. The newly refined value, in astronomer-speak, is: 74.3 ± 2.1 kilometers per second per megaparsec (a megaparsec is roughly 3 million light-years).
"Spitzer is yet again doing science it wasn't designed to do," said Michael Werner, the mission's project scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif., who has worked on the mission since its early concept phase more than 30 years ago. "First, it surprised us with its pioneering ability to study exoplanet atmospheres, and now, in the mission's later years, it's become a valuable cosmology tool."
In addition, the findings were combined with published data from NASA's Wilkinson Microwave Anisotropy Probe (WMAP) to obtain an independent measurement of dark energy, one of the greatest mysteries of our cosmos. In the late 1990s, astronomers were shocked to learn that the expansion of our universe is speeding up over time, or accelerating. Dubbed dark energy, this force or energy is thought to be winning a battle against gravity, pulling the fabric of the universe apart. Research documenting this acceleration garnered the 2011 Nobel Prize in physics.
"This is a huge puzzle," said lead author Freedman. "It's exciting that we were able to use Spitzer to tackle fundamental problems in cosmology: the precise rate at which the universe is expanding at the current time, as well as measuring the amount of dark energy in the universe from another angle."
Spitzer was able to improve upon past measurements of Hubble's constant due to its infrared vision, which sees through dust to provide better views of variable stars called Cepheids. These pulsating stars are vital "rungs" in what astronomers called the cosmic distant ladder: a set of objects with known distances that, when combined with the speeds at which the objects are moving away from us, reveal the expansion rate of the universe.
Cepheids are crucial to these calculations because their distances from Earth can be readily measured. In 1908, Henrietta Leavitt discovered that these stars pulse at a rate that is directly related to their intrinsic brightness. To visualize why this is important, imagine somebody walking away from you while carrying a candle. The candle would dim the farther it traveled, and its apparent brightness would reveal just how far.
The same principle applies to Cepheids, standard candles in our cosmos. By measuring how bright they appear on the sky, and comparing this to their known brightness as if they were close up, astronomers can calculate their distance from Earth.
Spitzer observed ten Cepheids in our own Milky Way galaxy and 80 in a nearby neighboring galaxy called the Large Magellanic Cloud. Without the cosmic dust blocking their view at the infrared wavelengths, the research team was able to obtain more precise measurements of the stars' apparent brightness, and thus their distances, than previous studies had done. With these data, the researchers could then tighten up the rungs on the cosmic distant ladder, opening the way for a new and improved estimate of our universe's expansion rate.
"Just over a decade ago, using the words 'precision' and 'cosmology' in the same sentence was not possible, and the size and age of the universe was not known to better than a factor of two," Freedman said. "Now we are talking about accuracies of a few percent. It is quite extraordinary"
The research team included former and current Carnegie scientists Barry Madore, Vicky Scowcroft, Andrew Monson, Chris Burns, Mark Seibert, Eric Persson, and Jane Rigby.
The Carnegie Institution for Science is a private, nonprofit organization headquartered in Washington, D.C., with six research departments throughout the U.S. Since its founding in 1902, the Carnegie Institution has been a pioneering force in basic scientific research. Carnegie scientists are leaders in plant biology, developmental biology, astronomy, materials science, global ecology, and Earth and planetary science.
Wendy Freedman | EurekAlert!
APEX takes a glimpse into the heart of darkness
25.05.2018 | Max-Planck-Institut für Radioastronomie
First chip-scale broadband optical system that can sense molecules in the mid-IR
24.05.2018 | Columbia University School of Engineering and Applied Science
The more electronics steer, accelerate and brake cars, the more important it is to protect them against cyber-attacks. That is why 15 partners from industry and academia will work together over the next three years on new approaches to IT security in self-driving cars. The joint project goes by the name Security For Connected, Autonomous Cars (SecForCARs) and has funding of €7.2 million from the German Federal Ministry of Education and Research. Infineon is leading the project.
Vehicles already offer diverse communication interfaces and more and more automated functions, such as distance and lane-keeping assist systems. At the same...
A research team led by physicists at the Technical University of Munich (TUM) has developed molecular nanoswitches that can be toggled between two structurally different states using an applied voltage. They can serve as the basis for a pioneering class of devices that could replace silicon-based components with organic molecules.
The development of new electronic technologies drives the incessant reduction of functional component sizes. In the context of an international collaborative...
At the LASYS 2018, from June 5th to 7th, the Laser Zentrum Hannover e.V. (LZH) will be showcasing processes for the laser material processing of tomorrow in hall 4 at stand 4E75. With blown bomb shells the LZH will present first results of a research project on civil security.
At this year's LASYS, the LZH will exhibit light-based processes such as cutting, welding, ablation and structuring as well as additive manufacturing for...
There are videos on the internet that can make one marvel at technology. For example, a smartphone is casually bent around the arm or a thin-film display is rolled in all directions and with almost every diameter. From the user's point of view, this looks fantastic. From a professional point of view, however, the question arises: Is that already possible?
At Display Week 2018, scientists from the Fraunhofer Institute for Applied Polymer Research IAP will be demonstrating today’s technological possibilities and...
So-called quantum many-body scars allow quantum systems to stay out of equilibrium much longer, explaining experiment | Study published in Nature Physics
Recently, researchers from Harvard and MIT succeeded in trapping a record 53 atoms and individually controlling their quantum state, realizing what is called a...
25.05.2018 | Event News
02.05.2018 | Event News
13.04.2018 | Event News
25.05.2018 | Event News
25.05.2018 | Machine Engineering
25.05.2018 | Life Sciences