New Hubble Constant Measurement Adds to Mystery of Universe’s Expansion Rate

Galaxies Used to Refine the Hubble Constant

Credit: NASA, ESA, W. Freedman (University of Chicago), ESO, and the Digitized Sky Survey

Astronomers have made a new measurement of how fast the universe is expanding, using an entirely different kind of star than previous endeavors. The revised measurement, which comes from NASA’s Hubble Space Telescope, falls in the center of a hotly debated question in astrophysics that may lead to a new interpretation of the universe’s fundamental properties.
Scientists have known for almost a century that the universe is expanding, meaning the distance between galaxies across the universe is becoming ever more vast every second. But exactly how fast space is stretching, a value known as the Hubble constant, has remained stubbornly elusive.
Now, University of Chicago professor Wendy Freedman and colleagues have a new measurement for the rate of expansion in the modern universe, suggesting the space between galaxies is stretching faster than scientists would expect. Freedman’s is one of several recent studies that point to a nagging discrepancy between modern expansion measurements and predictions based on the universe as it was more than 13 billion years ago, as measured by the European Space Agency’s Planck satellite.
As more research points to a discrepancy between predictions and observations, scientists are considering whether they may need to come up with a new model for the underlying physics of the universe in order to explain it. 
«The Hubble constant is the cosmological parameter that sets the absolute scale, size and age of the universe; it is one of the most direct ways we have of quantifying how the universe evolves,» said Freedman. «The discrepancy that we saw before has not gone away, but this new evidence suggests that the jury is still out on whether there is an immediate and compelling reason to believe that there is something fundamentally flawed in our current model of the universe.”
In a new paper accepted for publication in The Astrophysical Journal, Freedman and her team announced a new measurement of the Hubble constant using a kind of star known as a red giant. Their new observations, made using Hubble, indicate that the expansion rate for the nearby universe is just under 70 kilometers per second per megaparsec (km/sec/Mpc). One parsec is equivalent to 3.26 light-years distance.
This measurement is slightly smaller than the value of 74 km/sec/Mpc recently reported by the Hubble SH0ES (Supernovae H0 for the Equation of State) team using Cepheid variables, which are stars that pulse at regular intervals that correspond to their peak brightness. This team, led by Adam Riess of the Johns Hopkins University and Space Telescope Science Institute, Baltimore, Maryland, recently reported refining their observations to the highest precision to date for their Cepheid distance measurement technique.

How to Measure Expansion

A central challenge in measuring the universe’s expansion rate is that it is very difficult to accurately calculate distances to distant objects.
In 2001, Freedman led a team that used distant stars to make a landmark measurement of the Hubble constant. The Hubble Space Telescope Key Project team measured the value using Cepheid variables as distance markers. Their program concluded that the value of the Hubble constant for our universe was 72 km/sec/Mpc.
But more recently, scientists took a very different approach: building a model based on the rippling structure of light left over from the big bang, which is called the Cosmic Microwave Background. The Planck measurements allow scientists to predict how the early universe would likely have evolved into the expansion rate astronomers can measure today. Scientists calculated a value of 67.4 km/sec/Mpc, in significant disagreement with the rate of 74.0 km/sec/Mpc measured with Cepheid stars.
Astronomers have looked for anything that might be causing the mismatch. «Naturally, questions arise as to whether the discrepancy is coming from some aspect that astronomers don’t yet understand about the stars we’re measuring, or whether our cosmological model of the universe is still incomplete,» Freedman said. «Or maybe both need to be improved upon.»
Freedman’s team sought to check their results by establishing a new and entirely independent path to the Hubble constant using an entirely different kind of star.
Certain stars end their lives as a very luminous kind of star called a red giant, a stage of evolution that our own Sun will experience billions of years from now. At a certain point, the star undergoes a catastrophic event called a helium flash, in which the temperature rises to about 100 million degrees and the structure of the star is rearranged, which ultimately dramatically decreases its luminosity. 
Astronomers can measure the apparent brightness of the red giant stars at this stage in different galaxies, and they can use this as a way to tell their distance.
The Hubble constant is calculated by comparing distance values to the apparent recessional velocity of the target galaxies — that is, how fast galaxies seem to be moving away. The team’s calculations give a Hubble constant of 69.8 km/sec/Mpc — straddling the values derived by the Planck and Riess teams.
«Our initial thought was that if there’s a problem to be resolved between the Cepheids and the Cosmic Microwave Background, then the red giant method can be the tie-breaker,» said Freedman.
But the results do not appear to strongly favor one answer over the other say the researchers, although they align more closely with the Planck results.
NASA’s upcoming mission, the Wide Field Infrared Survey Telescope (WFIRST), scheduled to launch in the mid-2020s, will enable astronomers to better explore the value of the Hubble constant across cosmic time. WFIRST, with its Hubble-like resolution and 100 times greater view of the sky, will provide a wealth of new Type Ia supernovae, Cepheid variables, and red giant stars to fundamentally improve distance measurements to galaxies near and far.
The Hubble Space Telescope is a project of international cooperation between NASA and ESA (European Space Agency). NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy in Washington, D.C.


Ray Villard
Space Telescope Science Institute, Baltimore, Maryland

Louise Lerner
University of Chicago, Chicago, Illinois

Related Links:

Archive link

Lunar Reconnaissance Orbiter Camera Simulates View from Lunar Module

NASA — Lunar Reconnaissance Orbiter (LRO) patch.

July 16, 2019

Image credits: NASA/Goddard Space Flight Center/Arizona State University

The only visual record of the historic Apollo 11 landing is from a 16mm time-lapse (6 frames per second) movie camera mounted in Buzz Aldrin’s window (right side of Lunar Module Eagle or LM). Due to the small size of the LM windows and the angle at which the movie camera was mounted, what mission commander Neil Armstrong saw as he flew and landed the LM was not recorded. The Lunar Reconnaissance Orbiter Camera (LROC) team reconstructed the last three minutes of the landing trajectory (latitude, longitude, orientation, velocity, altitude) using landmark navigation and altitude call outs from the voice recording. From this trajectory information, and high resolution LROC Narrow Angle Camera (LROC NAC) images and topography, we simulated what Armstrong saw in those final minutes as he guided the LM down to the surface of the Moon. As the video begins, Armstrong could see the aim point was on the rocky northeastern flank of West crater (190 meters diameter), causing him to take manual control and fly horizontally, searching for a safe landing spot. At the time, only Armstrong saw the hazard; he was too busy flying the LM to discuss the situation with mission control.

After flying over the hazards presented by the bouldery flank of West crater, Armstrong spotted a safe spot about 500 meters down track where he carefully descended to the surface. Just before landing, the LM flew over what would later be called Little West crater (40 meters diameter). Armstrong would visit and photograph this crater during his extra-vehicular activity (EVA). Of course, during the landing, Armstrong was able to lean forward and back and turn his head to gain a view that was better than the simple, fixed viewpoint presented here. However, this simulated movie lets you relive those dramatic moments.

Image above: In this image, the Lunar Module descent stage and astronaut tracks are clearly visible — something Armstrong did not see during the landing. The incidence (solar) angle on the Narrow Angle Camera image is within a degree as when Apollo 11 landed (just after sunrise), so you see the same dramatic shadows. Image Credits: NASA/Goddard/Arizona State University.

How accurate is our simulated view? We reconstructed the view from Aldrin’s window from our derived trajectory, and you can view it side-by-side with the original 16mm film. You be the judge!

What Aldrin Saw: Original Film vs. Reconstruction

Video above: This video compares film from the landing of Apollo 11 (left) with a simulated reconstruction (right) based on data from NASA’s Lunar Reconnaissance Orbiter. Video Credits: NASA/Goddard Space Flight Center/Arizona State University.

— Additional multimedia from the LROC website maintained by Arizona State University:

ACKNOWLEDGMENT: A time-synchronized version of the original 16mm film (Apollo Flight Journal) and the First Men on the Moon website, which synchronizes the air-to-ground voice transmission with the original 16mm film, greatly aided the production of this work. These sources were played side-by-side with our reconstruction during its production, allowing us to better match the reconstruction to the 16mm film and altitude callouts.

Apollo 11:

LRO (Lunar Reconnaissance Orbiter):

Images (mentioned), Video (mentioned), Text, Credits: NASA/Karl Hille.

Greetings, Orbiter.chArchive link

Space Station Science Highlights: Week of July 8, 2019

ISS — Expedition 60 Mission patch.

July 16, 2019

The three members of Expedition 60 currently aboard the International Space Station conducted scientific investigations last week on improved lighting, bone health, growing and enjoying food in space and more. The space station supports commercial microgravity research and development and serves as a unique asset for NASA’s Artemis program, an effort to return humans to the Moon and to go on from there to Mars.

Image above: The NanoRack CubeSat Deployer (NRCSD) is a self-contained CubeSat system for deploying small satellites staged from the space station. The NRCSD-16 investigation consists of seven separate satellites: EntrySat, IOD-1 GEMS, KRAKsat, Swiatowid and Virginia CubeSat Constellation (VCC). Image Credits: NASA/Johnson Space Center.

Here are details on some of the science conducted on the orbiting lab during the week of July 8:

Let there be better light

The crew set up a light meter and performed an ambient meter reading for the Lighting Effects investigation. Spaceflight exposes crew members to sleep and wake schedules not connected to sunlight, which can cause insomnia and fatigue and negatively affect crew alertness and health. Adjusting light sources to simulate a more regular day and night schedule could improve crew circadian rhythms, sleep, and cognitive performance. This investigation examines the effects of changing space station lighting from fluorescent light bulbs to solid-state light-emitting diodes (LEDs) with adjustable intensity and color.

Animation above: NASA astronaut Nick Hague sets up the JEM Internal Ball Camera, a free-floating, remote-controlled panoramic camera that helps crews monitor operations and provides real-time video and image downloads to remote operators. Animation Credit: NASA.

In search of stronger bones

The crew participated in a blood draw for Medical Proteomics, an investigation by the Japanese Space Agency (JAXA) to evaluate changes of proteins in blood serum, bone and skeletal muscles after space flight. It also combines research results for space mice, astronauts, and patients on the ground to identify proteins related to osteopenia using the latest proteome analysis technique. Use of these marker proteins could benefit future assessment of the health of astronauts and osteoporosis patients on Earth.

Improving the menu in space

Food is critical for providing necessary calories and nutrients and has behavioral and psychological implications for astronauts. Studies on the space station have tested equipment and procedures for growing plants in space and have explored how the food supply affects the health and wellbeing of the crew. Last week saw work on several food-related investigations.

Image above: Leafy greens grown for the Veg-04 investigation to explore the viability of growing fresh food in space to support astronauts on long-term missions. The crew harvested the plants after 28 days of growth, stowing samples for analysis and taste testing the rest. Image Credit: NASA.

Crew members completed the Veg-04A investigation, harvesting and preparing half of the Mizuna leaves for return to ground for growth analysis. The crew consumed the other half of the leaves and competed surveys on the effects of growing the crop and on its taste. They also completed questionnaires for Food Acceptability, which examines changes in the appeal of the space station food supply. Whether crew members like and actually eat something may directly affect caloric intake and associated nutritional benefits and, in turn, the health of astronauts, especially on long-term missions.

Animation above: NASA astronaut Christina Koch harvests Mizuna leaves for the Veg-04 investigation. Animation Credit: NASA.

Other investigations on which the crew performed work:

— Team Task Switching looks at whether crew members have difficulty switching from one task to another and the effects of such switches to reduce negative consequences and improve individual and team motivation and effectiveness.

— The ISS Experience creates short virtual reality videos from footage taken during the yearlong investigation covering different aspects of crew life, execution of science, and the international partnerships involved on the space station.

— Standard Measures captures a consistent and simple set of measures from crew members throughout the ISS Program to characterize adaptive responses to and risks of living in space.

— The Two Phase Flow investigation examines the heat transfer characteristics of flow boiling in microgravity, creating a database on the heat transfer efficiency of liquids in space that can inform design of thermal management systems for future spacecraft.

— Cerebral Autoregulation tests whether the brain’s ability to self-regulate blood flow improves in microgravity, using non-invasive tests to measure blood flow in the brain before, during, and after a long-duration spaceflight.

— The RADI N2 investigation seeks to better characterize the neutron radiation environment aboard the space station to help define the risk it poses to crew members and support development of advanced protective measures for future spaceflight.

— Genes in Space-6 determines the optimal DNA repair mechanisms that cells use in the spaceflight environment. It induces DNA damage and evaluates the entire mutation and repair process in space for the first time, using the miniPCR and Biomolecule Sequencer tools aboard the space station.

— The Actiwatch is a wristwatch-like monitor containing an accelerometer to measure motion and color sensitive photodetectors for monitoring ambient lighting to help analyze the crew’s circadian rhythms, sleep-wake patterns, and activity.

Space to Ground: Farm-to-Table: 07/12/2019

Related links:

Expedition 60:


Lighting Effects:

Medical Proteomics:


Food Acceptability:

Spot the Station:

Space Station Research and Technology:

International Space Station (ISS):

Images (mentioned), Animations (mentioned), Video (NASA), Text, Credits: NASA/Michael Johnson/Vic Cooley, Lead Increment Scientist Expedition 60.

Best regards, Orbiter.chArchive link