Researchers including MITs Jacqueline Hewitt and Nicholas Kern share long-awaited outcomes, getting closer to the universes first stars.
All through history, humans have produced and shared stories that consider the development of stars– what they are and how the first stars came to be. Now, with new results from the Hydrogen Epoch of Reionization Array (HERA), a radio telescope located at the South Africa Karoo Astronomy Reserve, MIT scientists are one small, however substantial, step more detailed to comprehending that history.
By Maria Rose, MIT Kavli Institute for Astrophysics and Area Research
February 12, 2022
The HERA findings are in part so considerable because they were collected at such an early phase in HERAs advancement. To look back at the cosmic dawn, HERA utilizes low-frequency radio waves to determine signals that are not easily observed. With HERA, researchers can look at what is going on between galaxies and utilize that information to presume what galaxies are doing that we can not observe, and how galaxy development affects the space around it.
The 2nd part, which is what HERA has actually so far been looking for, is the disappearance of the 21 cm signal, which takes place when the hydrogen is ionized by the energy produced by additional star formation. Hewitt, project lead on broadening HERAs signal capability, has been working on the question of when the earliest stars formed because 2004.
HERA scientists are looking for the earliest indications of star development and galaxy structure. Particularly, researchers consisting of Jacqueline Hewitt, the Julius A. Stratton Professor of Physics at MIT, are attempting to understand what happened during a duration called the cosmic dawn, which took place about 400 million years after the Big Bang. In early fall 2021, Hewitt, Nicholas Kern, a Pappalardo Fellow in Physics at the MIT Kavli Institute for Astrophysics and Space Research, and other researchers from the global collaboration settled the long-awaited outcomes collected and evaluated over 4 years, during the first phases of the telescopes building.
Their study, published on February 7, 2022, in the Astrophysical Journal, presents new ceilings on radio signals from cosmic hydrogen, which suggests early star development and gives researchers a clearer photo of when the first stars and galaxies formed. These findings limit the theoretical designs that assume on the origins of the cosmic dawn.
Part of the HERA radio interferometric range in the South African Karoo desert throughout early building in 2016, pictured with site team for scale. Credit: Kathryn Rosie
The HERA findings are in part so considerable due to the fact that they were collected at such an early phase in HERAs advancement. The telescope, which operates as an array of radio meals, currently sits at just a fraction of its ultimate size– the data were gathered from simply 39 of HERAs 52 released antennae.
” Were not yet doing completely what we can do,” states Kern, the papers lead author. “This outcome is a presentation of the telescope as an entity. Its a presentation of a very first pass at an analysis of the data, which is kind of a framework, a bedrock, if you will, moving forward for all future analysis.”
Looking for a signal
To look back at the cosmic dawn, HERA utilizes low-frequency radio waves to recognize signals that are not quickly observed. This is different from other telescopes, such as the Hubble Space Telescope, which observe structures like galaxies that make up simply 5 percent of the observable matter in space. The other 95 percent of matter is what is between galaxies, consisting of low-density hydrogen. With HERA, scientists can look at what is going on between galaxies and utilize that info to infer what galaxies are doing that we can not observe, and how galaxy formation influences the area around it.
Members of the HERA partnership at a science meeting. The HERA team includes institutions across the U.S., Canada, Europe, and South Africa. Credit: Photo courtesy of the HERA team.
To understand this duration in deep spaces history, researchers are trying to find the “spin flip signal,” also understood as the 21-centimeter line, which is the wavelength of neutral hydrogen gas. This radio signal comes from intergalactic product between galaxies and is produced by the emission and/or absorption of hydrogen atoms provided off through this shift.
” What were taking a look at with HERA is: What does the spin flip signal appear like during this age?” says Steve Furlanetto, the HERA tasks lead theorist and an associate teacher of physics and astronomy at the University of California at Los Angeles.
Recognizing the Epoch of Reionization, or the timing of when the signal is observed, is whats crucial, he states. And then we desire to see if it vanishes because of reionization.”
The signal is very first altered when stars warm the hydrogen gas. The 2nd part, which is what HERA has actually so far been looking for, is the disappearance of the 21 cm signal, which occurs when the hydrogen is ionized by the energy produced by extra star formation.
The 21 cm line from the cosmic dawn has not yet been definitively discovered. The new results from HERA provide data– more sensitive than previous outcomes by a factor of 10– on the nature of the spin flip signal from when the universe was 500 million years old.
A first appearance
With these outcomes, the HERA group has been able to offer proof that eliminate a number of possible theories about galaxy formation. Most notably, the information reveal that there should have been some mechanism for warming up the hydrogen in area, which implies that galaxies must have black holes.
Part of the HERA? radio interferometric variety in the Karoo desert, South Africa. Credit: Dara Storer
” If you had galaxies that didnt have black holes, thats essentially something you can rule out,” Furnaletto says. “There should be heating, which, in the context of these models, indicates that there should be black holes near which X-rays are produced.”
With financing from the Gordon and Betty Moore Foundation and the National Science Foundation, HERA will run at 350 antennas and with a brand-new antenna design that will allow the telescope to catch lower frequency radio waves and view points at higher redshifts, efficiently seeing even more back in time.
Hewitt, project lead on expanding HERAs signal capacity, has actually been working on the question of when the earliest stars formed because 2004. She has led the prototyping of the new low-frequency parts, and is developing more techniques to analyze the current and future datasets. The new antennae style, from Cambridge University, must be installed by early 2022, and will drastically increase the variety of details they have the ability to obtain.
” This extension to lower frequencies is essential because it gets us to this period prior to the first stars,” says Hewitt, describing that the increased range will help them discover more about earlier phases of cosmic history.
” Its remarkable how it works. “Thats kind of fantastic that we can in fact do that.”
Recommendation: “First Results from HERA Phase I: Upper Limits on the Epoch of Reionization 21 cm Power Spectrum” by Zara Abdurashidova, James E. Aguirre, Paul Alexander, Zaki S. Ali, Yanga Balfour, Adam P. Beardsley, Gianni Bernardi, Tashalee S. Billings, Judd D. Bowman, Richard F. Bradley, Philip Bull, Jacob Burba, Steve Carey, Chris L. Carilli, Carina Cheng, David R. DeBoer, Matt Dexter, Eloy de Lera Acedo, Taylor Dibblee-Barkman, Joshua S. Dillon, John Ely, Aaron Ewall-Wice, Nicolas Fagnoni, Randall Fritz, Steven R. Furlanetto, Kingsley Gale-Sides, Brian Glendenning, Deepthi Gorthi, Bradley Greig, Jasper Grobbelaar, Ziyaad Halday, Bryna J. Hazelton, Jacqueline N. Hewitt, Jack Hickish, Daniel C. Jacobs, Austin Julius, Nicholas S. Kern, Joshua Kerrigan, Piyanat Kittiwisit, Saul A. Kohn, Matthew Kolopanis, Adam Lanman, Paul La Plante, Telalo Lekalake, David Lewis, Adrian Liu, David MacMahon, Lourence Malan, Cresshim Malgas, Matthys Maree, Zachary E. Martinot, Eunice Matsetela, Andrei Mesinger, Mathakane Molewa, Miguel F. Morales, Tshegofalang Mosiane, Steven G. Murray, Abraham R. Neben, Bojan Nikolic, Chuneeta D. Nunhokee, Aaron R. Parsons, Nipanjana Patra, Robert Pascua, Samantha Pieterse, Jonathan C. Pober, Nima Razavi-Ghods, Jon Ringuette, James Robnett, Kathryn Rosie, Peter Sims, Saurabh Singh, Craig Smith, Angelo Syce, Nithyanandan Thyagarajan, Peter K. G. Williams, Haoxuan Zheng and The HERA Collaboration, 7 February 2022, Astrophysical Journal.DOI: 10.3847/ 1538-4357/ ac1c78.
This work is supported, in part, by the National Science Foundation with institutional assistance from the HERA cooperation partners, and by the Gordon and Betty Moore Foundation. HERA is hosted by the South African Radio Astronomy Observatory, which is a center of the National Research Foundation, an agency of the Department of Science and Innovation.