ASU astronomers to explore the ‘cosmic dawn’ of the universe

September 14, 2016

Thirteen billion years ago, nearly every particle in the universe was affected by a new phenomenon: the emergence of starlight from the birth of stars in the first galaxies.

Throughout the universe, primordial gas was turned into ionized plasma, setting the conditions for the universe we see today.  The Hydrogen Epoch of Reionization Array (HERA) radio telescope in South Africa is a key ingredient in an international project, which ASU has joined, to investigate the early universe immediately after its birth in the Big Bang. Photo by Kathryn Rosie Download Full Image

How did the laws of physics enable the primordial gas that followed from the Big Bang to evolve into today’s complex universe? How is our universe able to support life, stars, galaxies, planets, even black holes? 

ASU’s cosmology group is seeking answers to these questions as part of an international experiment that has received nearly $10 million in funding from the National Science Foundation.

The experiment, an international collaboration called the Hydrogen Epoch of Reionization Array, or HERA, currently has 19 14-meter (42-foot) radio dishes aimed at the southern sky near Carnarvon, South Africa, and will soon up that number to 37 and then eventually to 240 by 2018.

“HERA builds on the lessons learned from two existing experiments, PAPER and MWA,” explained School of Earth and Space Exploration (SESE) associate professor and astronomer Judd Bowman, who is the project scientist for HERA.

“Over the last two years, the team has been applying those lessons to the design of HERA and testing prototype hardware on a small test array of 19 dishes. This additional funding will allow the team to begin HERA’s full-scale science program.”

ASU is a partner in HERA, which is led by the University of California, Berkeley. HERA will explore the first billion years of the universe, a period when hydrogen gas collapsed and led to the ignition of stars and galaxies throughout the universe.

In addition to Bowman, the ASU team includes post-doctoral scholars Danny Jacobs, Nithya Thyagarajan and Adam Beardsley, as well as graduate student Piyanat Kittiwisit. 

Jacobs, the commissioning scientist for HERA, is leading much of the software development needed to process and transfer data from the remote site back to the U.S. 

Jacobs will also be leading a team to South Africa this fall to aid in the construction and commission of the telescope. “We'll be getting HERA ready for the upcoming observing season when it will double in size and become more sensitive to potential cosmological signals.”

The HERA array, which could eventually expand to 350 telescopes, consists of radio dishes staring fixedly upwards, measuring radiation originally emitted at a wavelength of 21 centimeters — the hyperfine transition in the hydrogen atom — that has been stretched by a factor of 10 or more by the expansion of the universe since it was emitted some 13 billion years ago.

“We have learned a ton about the cosmology of our universe from studies of the cosmic microwave background, but those experiments are observing just the thin shell of light that was emitted from a bunch of protons and electrons that finally combined into neutral hydrogen 380,000 years after the Big Bang,“ said Aaron Parsons, A UC Berkeley associate professor of astronomy and principal investigator for HERA. “We know from these experiments that the universe started out neutral, and we know that it ended ionized, and we are trying to map out how it transitioned between those two.“

The strategy is to build a hexagonal array of radio dishes that minimizes the noise, such as radio reflections in the dishes and wires, that would obscure the signal. A supercomputer’s worth of field programmable gate arrays will cross-correlate the signals from the antennas to finely map a 10-degree swath of southern sky centered at -30 degrees latitude.

Using techniques adopted from PAPER and the MWA, the team will employ this computer-processing power to eliminate noise from the foreground astronomical radio sources in the band — 150-350 centimeters — to reveal the rapidly varying signal from neutral hydrogen as they tune across the radio spectrum.

Once astronomers understand the reionization process, they can use the new information to improve on other cosmological measurements. The reionized hydrogen gas around galaxies following reionization distorts signals from the oldest light in the universe — the cosmic microwave background (CMB) radiation. HERA will help astronomers correct for this distortion.

This will allow cosmologists, like SESE's Phil Mauskopf, to perform more precise searches with current and future CMB experiments for the signatures of primordial gravitational waves, which are predicted to have been produced when the universe expanded rapidly during the first fraction of a second of the Big Bang — a period known as inflation.

It will also help astronomers like SESE's Rogier Windhorst, James Rhoads and Sangeeta Malhotra, who are using other methods to directly observe the first galaxies responsible for the reionization of the hydrogen gas in the universe.

Other partners in HERA include Brown University, Massachusetts Institute of Technology, National Radio Astronomical Observatory, Scuola Normale Superiore in Pisa (Italy), Square Kilometer Array (South Africa), University of California Los Angeles, University of Cambridge (UK), University of Pennsylvania, and the University of Washington.

Other collaborators are the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, and the University of KwaZulu Natal in Durban, University of Western Cape in Cape Town and Rhodes University in Grahamstown, all in South Africa.

Karin Valentine

Media Relations & Marketing manager, School of Earth and Space Exploration


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10 things to know during Hispanic Heritage Month

Why does Hispanic Heritage Month start in the middle of the month? Read on.
Hispanic and Latino are not interchangeable, and other facts for heritage month.
September 14, 2016

ASU — where nearly a fifth of students identify as Hispanic/Latino — to host festivals, food events, films and more

Sept. 15 marks the start of Hispanic Heritage Month. It’s a time to honor the contributions that Hispanics and Latinos have made to science, the arts, social justice and more.

It’s also time to notice the unusual timing — a midmonth start — for a heritage month. (Want to know why? Keep reading.)

Hispanics/Latinos represent nearly one-fifth of the United States’ population — and of Arizona State University’s students. In the last 10 years their enrollment has more than doubled, from 7,300 in 2005 to nearly 17,000 in 2015. At ASU, the heritage month is being celebrated with a number of events, including festivals, traditional foods, film screenings, discussions and dance.

The history of nationally observing Hispanic/Latino heritage dates back to President Lyndon Johnson’s 1968 proclamation of Hispanic Heritage Week, to include Sept. 15 and 16 to honor the independence days of several Latin American neighbors. However, it was not until 1988 that Congress would pass a law establishing National Hispanic Heritage Month designating a “31-day period beginning Sept. 15 and ending on Oct. 15.”

10 things to know as we celebrate Hispanic Heritage Month

1. Why the mid-month start? Sept. 15 (1821) is an important date because it honors the day of independence for Costa Rica, El Salvador, Guatemala, Honduras and Nicaragua.

2. Sept. 16 is also a key date: Mexico's day of independence (1810). Many mistake Cinco de Mayo for our southern neighbor's independence day, but the widely celebrated May 5 holiday commemorates the victory at the Battle of Puebla in 1862 where Mexican forces defeated the French invaders.

3. Hispanics/Latinos are considered the largest ethnic or racial minority in the United States at more than 56 million, more than 17 percent of the total population, according to the U.S. Census.

4. At ASU, there were 13,208 students during fall 2015 who identified as Hispanic/Latino — more than 18 percent of the student population.

5. ASU is No. 1 among Pac-12 universities for the number of Latino graduates.

6. ASU was ranked 13th in Hispanic Outlook in Higher Education magazine’s 2015 rankings of U.S. higher-education institutions for the number of undergraduate degrees conferred to Hispanics in several key areas.

7. Oct. 12 is often celebrated as Columbus Day. However, in many Latin American countries and in various U.S. communities, it is celebrated as Día de la Raza — among other names — to honor the discovery of the Americas as well as mixed Indigenous and European heritages.

8. Hispanic and Latino are not the same thing. The term “Hispanic” once represented a relationship to the people of ancient Hispania — the Iberian Peninsula, principally divided by modern Spain and Portugal. Currently, it is widely regarded as a term that signifies the cultural resonance to contemporary Spain and to countries once colonized by Spain (thus, those living in Brazil would not be included). Latino generally refers to someone from Latin American origin or ancestry.

9. The term Hispanic was adopted by the U.S. government in the early 1970s after Grace Flores-Hughes and what was then known as an U.S. Department of Health, Education and Welfare interdepartmental committee convened to develop a comprehensive term to describe people of Spanish, Mexican, Central and South American or Caribbean (Spanish speaking) descent.

10. Prior to 1970, Spanish and Latin American immigrants were classified as “white” and grouped with European Americans. It was not until 1970 when a separate question on origin or descent was asked on the census. However, this question appeared to only 5 percent of the population. In June 1976, Congress passed a law mandating the collection and analysis of data for “Americans of Spanish origin or descent.” A separate question on Hispanic origin or descent appeared on the 1980 census. Seventeen years later, revised standards on race classifications resulted in Hispanic becoming “Hispanic or Latino.” The term “Latino” would later appear in the 2000 census and further amended in the 2010 census.

The events celebrating Hispanic Heritage Month at ASU are part of the broader cultural engagement at the university. Culture @ ASU aims to create a community that values, appreciates and accepts others through a variety of events and activities, while introducing students to the rich cultural fiber at ASU.


The Hispanic Heritage Month Planning Committee contributed to this story. Top photo from the ASU Chicano/a Research Collection and University Archives.