KICP in the News, 2018

In 2017, a big year for science, we learned from cosmic discoveries
The Hill, January 11, 2018
In 2017, a big year for science, we learned from cosmic discoveries
by Michael S. Turner, The Hill

Our Universe is unfathomably large - billions of years old, billions of light-years across, and filled with hundreds of billion of galaxies, each with hundreds of billions of stars and planets. It often is beyond the reach of our instruments and our minds. Nonetheless, driven by curiosity, each year we make discoveries that expand our view of it, surprise us and help us to understand our place within it.

The big event of 2017 was the collision of two neutron stars in a relatively nearby galaxy, 140 million light years away. Such events are commonplace, happening many times a day, yet this was one was special because for the first time, the National Science Foundation's Laser Interferometer Gravitational-wave Observatory (LIGO) detected tiny ripples in the fabric of space-time that the cataclysmic event created. LIGO alerted astronomers, and GW170817 became the most well-studied astrophysical event, viewed with radio, infrared, visible, x-ray and gamma-ray "eyes."

Here is but one thing we learned: most, if not all, of the heaviest elements in the periodic table, e.g., gold and platinum, were made by colliding neutron stars.

Of course, LIGO thrilled us in 2016 with its announcement that it had detected gravitational waves from colliding black holes; this past December, three American scientists (Barry Barish and Kip Thorne of Caltech, and Rainer Weiss of MIT) were honored with the Nobel Prize for that discovery.

Closer to home, in October we were surprised by the first interstellar asteroid ever seen. We are used to asteroids - debris left over from the formation of our solar system - visiting us. In fact, the PanSTARRS1 telescope on Haleakala that discovered Oumuamua (for "scout"), as it is now officially known, searches for near-Earth objects that are potentially Earth-threatening. Oumuamua is not bound to our sun; it flew in from the direction of the Lyra constellation, passed between Mercury and the sun, and flew out again in the direction of the Pegasus constellation.

As large as an aircraft carrier and similarly shaped, Oumuamua reminded us that we are connected to the rest of the cosmos. Our solar system likely has shed asteroids and even planets that have flown by other stars with planets, and four NASA spacecraft - Pioneers 10 and 11 and Voyagers 1 and 2 - have left our solar system. The Voyagers carry the Golden Record of sounds recorded from Earth that Carl Sagan and his team put together to introduce us to the larger Universe.

It has been more than 20 years since we discovered the first exoplanets (planets orbiting around other stars). NASA's Kepler satellite has been the exoplanet workhorse, having discovered more than 4,000 exoplanets and 600 planetary systems. Astronomers have identified around 10 exoplanets in the habitable zone. Last year's big news was the discovery of the TRAPPIST 1 system, seven terrestrial-like planets orbiting a red dwarf star about 40 light years away. Five of the seven planets are similar in size to Earth and three are in the habitable zone, the sweet spot where liquid water - and hopefully life - can exist. We are well on our way to answering a very big question: Are we alone?

Moving to the far reaches of the Universe, the most distant quasar seen yet was discovered last year. The light we see began the journey to us when the Universe was only about 700 million years old. It presents us with a mystery: How did the billion-solar-mass black hole that powers this quasar form so early in the history of the Universe? (All galaxies, including our Milky Way, have massive black holes at their centers and go through an early "quasar phase" when their black holes shine brightly because of infalling matter.) LIGO and other gravitational-wave detectors coming on line in the future should shed light on this question.

While the great American eclipse of 2017 was not a surprise and did not lead to any startling discoveries, millions of Americans including me - were awed by it as the path of totality traversed the United States from Oregon to Georgia. In this amazing natural phenomenon, the moon nicely fits over the sun and blocks its light, allowing us to look directly at the sun without being blinded and view its - beautiful corona.

The corona of the sun is much hotter (millions of degrees) and wispier than its surface, extending many solar radii beyond the disk of the sun. The corona is responsible for much of the sun's activity that impacts our planet, including solar flares and coronal mass ejections, and how the corona works is still a mystery. Later this year, NASA will launch the Parker Solar Probe, which will orbit the sun on a highly elliptical path that will take it inside the sun's corona - really! - more than 20 times to make measurements that could solve some of mysteries of the corona.

Science is now a global activity that the United States no longer dominates. But as these discoveries illustrate, we continue to lead. Our success has involved three critical elements: thinking bold, throwing deep and sticking with it.

The LIGO Nobel Laureates were bold enough to think that you could detect a change in distance of one-thousandth the size of a proton between two mirrors separated by four kilometers. The NSF threw deep when it invested close to $1 billion over 25 years to build LIGO. And NASA stuck with it when Hubble had initial mirror problems, and more recently when it found a work-around to keep Kepler producing science after two gyros failed at the end of its four-year planned mission.

Certainly, cosmic discoveries help us to understand our place in the Universe, but they also inspire and awe us, young and old.

Michael S. Turner is a theoretical cosmologist who coined the term "dark energy" in 1998. He is the Bruce V. and Diana M. Rauner Distinguished Service Professor at the University of Chicago, and is the former assistant director for mathematical and physical sciences for the National Science Foundation.


Related Links:
KICP Members: Michael S. Turner
Scientific projects: Laser Interferometer Gravitational-wave Observatory (LIGO)
Dark Energy Survey finds remains of 11 galaxies eaten by the Milky Way
UChicago News, January 16, 2018
This image shows the entire Dark Energy Survey field of view - roughly one-eighth of the sky - captured by the Dark Energy Camera, with different colors corresponding to the distance of stars. (Blue is closer, green is farther away, red is even farther.) Several stellar streams are visible in this image as yellow, blue and red streaks across the sky.   <i>Courtesy of Dark Energy Survey</i>
This image shows the entire Dark Energy Survey field of view - roughly one-eighth of the sky - captured by the Dark Energy Camera, with different colors corresponding to the distance of stars. (Blue is closer, green is farther away, red is even farther.) Several stellar streams are visible in this image as yellow, blue and red streaks across the sky.

Courtesy of Dark Energy Survey
UChicago News

Scientific collaboration including UChicago and labs releases three years of data

Scientists have released the preliminary cosmological findings from the Dark Energy Survey - research on about 400 million astronomical objects, including distant galaxies as well as stars in our own galaxy.

Among the highlights of the first three years of survey data, presented Jan. 10 during the American Astronomical Society meeting in Washington, D.C., is the discovery of 11 new stellar streams - remnants of smaller galaxies torn apart and devoured by our Milky Way.

The results were announced by the Dark Energy Survey, an international collaboration of more than 400 members including scientists from UChicago, Argonne and Fermilab, that aims to reveal the nature of the mysterious force of dark energy.

The public release fulfills a commitment scientists on the survey made to share their findings with the astronomy community and the public. The data cover about 5,000 square degrees, or one-eighth of the entire sky, and include roughly 40,000 exposures taken with the Dark Energy Camera. The images correspond to hundreds of terabytes of data and are being released along with catalogs of hundreds of millions of galaxies and stars.

"There are all kinds of discoveries waiting to be found in the data," said Brian Yanny of Fermi National Accelerator Laboratory, Dark Energy Survey data management project scientist. "While DES scientists are focused on using it to learn about dark energy, we wanted to enable astronomers to explore these images in new ways, to improve our understanding of the universe."

The Dark Energy Camera, the primary observation tool of the Dark Energy Survey, is one of the most powerful digital imaging devices in existence. It was built and tested at UChicago-affiliated Fermilab, the lead laboratory on the Dark Energy Survey, and is mounted on the National Science Foundation's 4-meter Blanco telescope in Chile. The DES images are processed by a team at the National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign.

One new discovery enabled by the data set is the detection of 11 new streams of stars around our Milky Way. Our home galaxy is surrounded by a massive halo of dark matter, which exerts a powerful gravitational pull on smaller, nearby galaxies. The Milky Way grows by pulling in, ripping apart and absorbing these smaller systems. As stars are torn away, they form streams across the sky that can be detected using the Dark Energy Camera. Even so, stellar streams are extremely difficult to find since they are composed of relatively few stars spread out over a large area of sky.

"It's exciting that we found so many stellar streams," said astrophysicist Alex Drlica-Wagner of Fermilab and the Kavli Institute for Cosmological Physics at UChicago. "We can use these streams to measure the amount, distribution and 'clumpiness' of dark matter in the Milky Way. Studies of stellar streams will help constrain the fundamental properties of dark matter."

Prior to the new discoveries, only about two dozen stellar streams had been discovered. Many of them were found by the Sloan Digital Sky Survey, a precursor to the Dark Energy Survey. The effort to detect new stellar streams in the Dark Energy Survey was led by University of Chicago graduate student Nora Shipp.

"We're interested in these streams because they teach us about the formation and structure of the Milky Way and its dark matter halo. Stellar streams give us a snapshot of a larger galaxy being built out of smaller ones," said Shipp. "These discoveries are possible because DES is the widest, deepest and best-calibrated survey out there."

Since there is no universally accepted naming convention for stellar streams, the Dark Energy Survey has reached out to schools in Chile and Australia, asking young students to select names. Students and their teachers have worked together to name the streams after aquatic words in native languages from northern Chile and aboriginal Australia.

Funding: U.S. Department of Energy Office of Science, National Science Foundation

- This release was originally posted on the Fermi National Accelerator Laboratory website.


Related Links:
KICP Members: Alex Drlica-Wagner
KICP Students: Nora Shipp
Scientific projects: Dark Energy Survey (DES)