Our universe tells its story in many colors. In this episode we look at three stories of star formation, told in radio light, that describe how our universe formed stars, shed carbon, and formed structures that include our galaxy.
Today’s news focuses on the history of our universe’s star formation. This is one more instance of astronomers finding novel ways to do science initially planned for JWST using other instruments on and above our world.
Massive stars put out the bulk of their light in the ultraviolet, and our universe’s expansion stretches this light out, pushing it through the visible light spectrum and all the way out to the infrared and radio. If successfully launched, JWST will be able to detect this early light, but today astronomers are turning to ground-based radio dishes to get at a start at this early universe science.
Our big picture understanding describes a universe where star formation started a few hundred thousand to a million years after the Big Bang, with the first galaxies appearing to be established a few hundred million years after the Big Bang. The universe continues to evolve, lighting up as galaxies quickly evolve toward well-established morphologies with peak star-formation occurring 2-5 billion years after the Big Bang. In our universe’s more than 13 billion year history, the structures established in those early eons formed the gravitational foundations around which everything we see today has gathered.
While we had seen hints of the most massive of these early structures with radio and infrared telescopes, we haven’t been able to the smaller, more typical systems until now. The MeerKAT telescope in South Africa is one of the most sensitive radio telescopes ever built and it recently used it’s array of 64 dishes to peer at one of the most radio dark areas of the sky to see if it could detect the faint young galaxies that should fill the sky. The detectors on these dishes were specifically tuned to detect the light of short lived massive stars that only live for 30 million years, making it possible for them to filter their view to only star forming galaxies. After combining 130 hours of observations of an area just 5 times the size of the full moon, they discovered tens of thousands of star-bursting galaxies shining during the peak period of star formation 8-11 Billion years ago, and that star formation peak was even brighter and more active than previously predicted. This work will be published in the Astrophysical Journal and was led by Tom Mauch.
MeerKAT is an amazing radio array, but it is only a precursor of the instruments that are yet to come. In the coming years, a global consortium of nations and institutes will be building the Square Kilometer Array, or SKA, in Southern Africa and Australia. The continent spanning instrument will provide increased sensitivity and resolution, making it possible to see even more details about our early universe.
Credit: ALMA (ESO/NAOJ/NRAO), NASA/ESA Hubble Space Telescope, Fujimoto et al.
- Carbon Cocoons Surround Growing Galaxies – ALMA Spots Earliest Environment Pollution in the Universe (ALMA)
MeerKAT isn’t the only game in town. In Chile, the Atacama Large Millimeter Array is also observing the radio sky. This different facility has different capabilities, and one of its strengths is detecting different elements. In a new study coming out in the Astrophysical Journal, a team led by Seji Fujimoto studied the region around young galaxies that were also observed by the Hubble Space Telescope. The light from these systems was released just 1 billion years after the Big Bang. They found that the clouds of material surrounding these galaxies was already rich in carbon at this early time. This means that 1 billion years after the Big Bang, stars had already been born, lived, and died in ways that released these newly formed carbon atoms back into the Universe to be recycled into new stars. The amount detected is more than previously expected. According to Rob Ivison, the Director for Science at the European Southern Observatory. “Energetic jets and radiation from supermassive black holes in the centers of the galaxies could also help transport carbon outside of the galaxies and finally to throughout the Universe. We are witnessing this ongoing diffusion process, the earliest environmental pollution in the Universe.”
- ESO Telescope Images Stunning Central Region of Milky Way, Finds Ancient Star Burst (ESO)
- Star formation in the center of the Milky Way came in bursts, new study shows (Max Planck)
Looking across the universe, we can see how things evolved by looking at light that has traveled for more or less time. By looking at a variety of systems across the history of the universe, we begin to get a sense of how things change, but these diverse snapshots aren’t always enough to put together the detailed movie we want. In looking at our own galaxy, it had been assumed that across it’s history, star formation had churned along in the center of the galaxy at a regular pace, but new results published in Nature Astronomy finds that isn’t actually the case. Rather, it now appears that 90% of the stars formed at least 8 billion years ago, while another 5% of the stars formed in a second burst 1 billion years ago.
To get at this new understanding, astronomers needed to be able to both peer through the gas and dust between our solar system and the center of the galaxy, and to also be able to resolve individual stars in this incredibly dense region. This is possible using the new HAWK-I instrument on the 8-meter Very Large Telescope in Chile. Once light from the individual stars could be separated, it was possible to plot the stars in a color magnitude diagram and see if the distribution of stars was consistent with continuous star formation, or bursts. The results are striking, and the question now becomes, what happened to drive these two discrete events.
Science is a process. We are constantly striving to answer the fundamental questions of how did it all start, how did it change over time, and how will it all end using imperfect and partial data. With time, our data improves and with each new data set, we must refine the story we tell to reflect our new understanding of reality.
It’s a process, and with today’s new results we have see everything grind one more step closer to a true understanding.
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And that rounds out our show for today.
Thank you all for listening. The Daily Space is produced by Susie Murph, and is a product of the Planetary Science Institute, a 501(c)3 non profit dedicated to exploring our Solar System and beyond. During the month of December, we are doing a massive funding drive to ensure not just this show but all of CosmoQuest’s non-profit programs can thrive in 2020. You can help us out by tuning into our 40 hour telethon – our hangoutathon – this coming weekend on Twitch.tv/CosmoQuestX, or by contributing through streamlabs.com/CosmoQuestX
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