Using galaxies as giant gravitational lenses, an international group of astronomers headed by Max Planck@TUM tenure track professor Sherry Suyu measured independently how fast the Universe is expanding. The newly measured expansion rate for the local Universe is consistent with earlier findings. These are, however, in intriguing disagreement with measurements of the early Universe. This hints at a fundamental problem at the very heart of our understanding of the cosmos.
The Hubble constant — the rate at which the Universe is expanding — is one of the fundamental quantities describing our Universe. A group of astronomers, the H0LiCOW collaboration (H0 Lenses in COsmograil’s Wellspring), used the NASA/ESA Hubble Space Telescope and other telescopes in space and on the ground to observe five galaxies in order to arrive at an independent measurement of the Hubble constant.
HE0435-1223, located in the centre of this wide-field image, is among the five best lensed quasars discovered to date.
Image: ESA/Hubble, NASA
The new measurement is completely independent of — but in excellent agreement with — other measurements of the Hubble constant in the local Universe that used Cepheid variable stars and supernovae as points of reference.
The collaboration is led by Sherry Suyu, who recently moved from the Academia Sinica Institute of Astronomy and Astrophysics (ASIAA) in Taipei (Taiwan) to Garching (Germany) where she works now as a group leader at the Max Planck Institute for Astrophysics and at the Technical University of Munich as a tenure track professor in the Max Planck@TUM program.
A new kind of physics?
However, the value measured by Suyu and her team, as well as those measured using Cepheids and supernovae, are different from the measurement made by the ESA Planck satellite. But there is an important distinction — Planck measured the Hubble constant for the early Universe by observing the cosmic microwave background.
While the value for the Hubble constant determined by Planck fits with our current understanding of the cosmos, the values obtained by the different groups of astronomers for the local Universe are in disagreement with our accepted theoretical model of the Universe.
“The expansion rate of the Universe is now starting to be measured in different ways with such high precision that actual discrepancies may possibly point towards new physics beyond our current knowledge of the Universe,” elaborates Suyu.
Seeing around the corner with gravitational lenses
The targets of the study were massive galaxies positioned between Earth and very distant quasars — incredibly luminous galaxy cores. The light from the more distant quasars is bent around the huge masses of the galaxies as a result of strong gravitational lensing – an effect first predicted by Swiss astronomer Fritz Zwicky 80 years ago. This creates multiple images of the background quasar and its host galaxy, some smeared into extended arcs.
Because galaxies do not create perfectly spherical distortions in the fabric of space and the lensing galaxies and quasars are not perfectly aligned, the light from the different images of the background quasar follows paths which have slightly different lengths.
Since the brightness of quasars changes over time, astronomers can see the different images flicker at different times, the delays between them depending on the lengths of the paths the light has taken. These delays are directly related to the value of the Hubble constant.
“Our method is the most simple and direct way to measure the Hubble constant as it only uses geometry and General Relativity, no other assumptions,” explains co-lead Frédéric Courbin from EPFL, Switzerland.
Using the accurate measurements of the time delays between the multiple images, as well as computer models, allowed the team to determine the Hubble constant to an impressively high precision: the error is only 3.8 percent. “To reach that accuracy, we even considered the lensing effects of all other nearby galaxies in our analysis,” explains Stefan Hilbert from the Cluster of Excellence Origin and Structure of the Universe.
“An accurate measurement of the Hubble constant is one of the most sought-after prizes in cosmological research today,” highlights team member Vivien Bonvin, from EPFL, Switzerland. And Suyu adds: “The Hubble constant is crucial for modern astronomy as it can help to confirm or refute whether our picture of the Universe — composed of dark energy, dark matter and normal matter — is actually correct, or if we are missing something fundamental.”
Max Planck@TUM: TUM and the Max-Planck-Gesellschaft (MPG) offer a joined career path for highly qualified early career scientists. It combines research as a Max Planck Research Group Leader with a Tenure Track professorship at TUM. For more information, please see here: https://www.tum.de/en/about-tum/working-at-tum/faculty-recruiting/tum-faculty-te...
Instruments used: The study used, alongside the NASA/ESA Hubble Space Telescope, the Keck Telescope, ESO’s Very Large Telescope, the Subaru Telescope, the Gemini Telescope, the Victor M. Blanco Telescope, the Canada-France-Hawaii telescope and the NASA Spitzer Space Telescope. In addition, data from the Swiss 1.2-metre Leonhard Euler Telescope and the MPG/ESO 2.2-metre telescope in Chile were used.
Precision of the Hubble constant: The H0LiCOW team determined a value for the Hubble constant of 71.9±2.7 kilometres per second per Megaparsec. In 2016, scientists using the Hubble Space Telescope measured a value of 73.24±1.74 kilometres per second per Megaparsec. In 2015, the ESA Planck Satellite measured the constant with the highest precision so far and obtained a value of 66.93±0.62 kilometres per second per Megaparsec.
This research was presented in a series of papers to appear in the Monthly Notices of the Royal Astronomical Society:
1. Suyu et al.; H0LiCOW I. Program Overview
Submitted to MNRAS, https://arxiv.org/abs/1607.00017
2. Sluse et al.; H0LiCOW II. Spectroscopic survey and galaxy-group identification of the strong gravitational lens system HE0435-1223
Submitted to MNRAS, https://arxiv.org/abs/1607.00382
3. Rusu et al.; H0LiCOW III. Quantifying the effect of mass along the line of sight to the gravitational lens HE 0435-1223 through weighted galaxy counts
Submitted to MNRAS, https://arxiv.org/abs/1607.01047
4. Wong et al.; H0LiCOW IV. Lens mass model of HE 0435-1223 and blind measurement of its time-delay distance for cosmology
Accepted by MNRAS, https://arxiv.org/abs/1607.01403
5. Bonvin et al.; H0LiCOW V. New COSMOGRAIL time delays of HE 0435−1223: H0 to 3.8% precision from strong lensing in a flat ΛCDM model
Accepted by MNRAS, https://arxiv.org/abs/1607.01790
6. Ding et al.; H0LiCOW VI. Testing the fidelity of lensed quasar host galaxy reconstruction
MNRAS (2016) 465 (4): 4634-4649, https://arxiv.org/abs/1610.08504
Max Planck Institute for Astrophysics
Tel.: +49 89 30000 2015
Max Planck Institute for Astrophysics
Tel.: +49 89 30000 3980
Junior Research Group Leader
Excellence Cluster Universe
Tel: +49 89 35831 7148
Dr. Ulrich Marsch | Technische Universität München
Unconventional superconductor may be used to create quantum computers of the future
19.02.2018 | Chalmers University of Technology
Hubble sees Neptune's mysterious shrinking storm
16.02.2018 | NASA/Goddard Space Flight Center
For the first time, a team of researchers at the Max-Planck Institute (MPI) for Polymer Research in Mainz, Germany, has succeeded in making an integrated circuit (IC) from just a monolayer of a semiconducting polymer via a bottom-up, self-assembly approach.
In the self-assembly process, the semiconducting polymer arranges itself into an ordered monolayer in a transistor. The transistors are binary switches used...
Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale
Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...
For photographers and scientists, lenses are lifesavers. They reflect and refract light, making possible the imaging systems that drive discovery through the microscope and preserve history through cameras.
But today's glass-based lenses are bulky and resist miniaturization. Next-generation technologies, such as ultrathin cameras or tiny microscopes, require...
Scientists from the University of Zurich have succeeded for the first time in tracking individual stem cells and their neuronal progeny over months within the intact adult brain. This study sheds light on how new neurons are produced throughout life.
The generation of new nerve cells was once thought to taper off at the end of embryonic development. However, recent research has shown that the adult brain...
Theoretical physicists propose to use negative interference to control heat flow in quantum devices. Study published in Physical Review Letters
Quantum computer parts are sensitive and need to be cooled to very low temperatures. Their tiny size makes them particularly susceptible to a temperature...
15.02.2018 | Event News
13.02.2018 | Event News
12.02.2018 | Event News
19.02.2018 | Materials Sciences
19.02.2018 | Materials Sciences
19.02.2018 | Life Sciences