Nav: Home

To see the first-born stars of the universe

April 25, 2018

About 200 to 400 million years after the Big Bang created the universe, the first stars began to appear. Ordinarily stars lying at such a great distance in space and time would be out of reach even for NASA's new James Webb Space Telescope, due for launch in 2020.

However, astronomers at Arizona State University are leading a team of scientists who propose that with good timing and some luck, the Webb Space Telescope will be able to capture light from the first stars to be born in the universe.

"Looking for the first stars has long been a goal of astronomy," said Rogier Windhorst, Regents' Professor of astrophysics in ASU's School of Earth and Space Exploration. "They will tell us about the actual properties of the very early universe, things we've only modeled on our computers until now."

Windhorst's collaborator, Frank Timmes, professor of astrophysics at the School of Earth and Space Exploration, adds, "We want to answer questions about the early universe such as, were binary stars common or were most stars single? How many heavy chemical elements were produced, cooked up by the very first stars, and how did those first stars actually form?

Duho Kim, a School of Earth and Space Exploration graduate student of Windhorst's, worked on modeling star populations and dust in galaxies.

The other collaborators on the paper are J. Stuart B. Wyithe (University of Melbourne, Australia), Mehmet Alpaslan (New York University), Stephen K. Andrews (University of Western Australia), Daniel Coe (Space Telescope Science Institute), Jose M. Diego (Instituto de Fisica de Cantabria, Spain), Mark Dijkstra (University of Oslo), and Simon P. Driver and Patrick L. Kelly (both University of California, Berkeley).

The team's paper, published in the Astrophysical Journal Supplement, describes how the challenging observations can be done.

Gravity's magnifying lens

The first essential step in the task relies on the infrared sensitivity of the Webb Telescope. While the first stars were large, hot and radiated far-ultraviolet light, they lie so far away that the expansion of the universe has shifted their radiation peak from the ultraviolet to much longer infrared wavelengths. Thus their starlight drops into the Webb Telescope's infrared detectors like a baseball landing in a fielder's mitt.

The second essential step is to use the combined gravity of an intervening cluster of galaxies as a lens to focus and magnify the light of the first generation stars. Typical gravitational lensing can magnify light 10 to 20 times, but that's not enough to make a first-generation star visible to the Webb Telescope. For Webb, the candidate star's light needs boosting by factor of 10,000 or more.

To gain that much magnification calls for "caustic transits," special alignments where a star's light is greatly magnified for a few weeks as the galaxy cluster drifts across the sky between Earth and the star.

Caustic transits occur because a cluster of galaxies acting as a lens doesn't produce a single image like a reading magnifier. The effect is more like looking through a lumpy sheet of glass, with null zones and hot spots. A caustic is where magnification is greatest, and because the galaxies in the lensing cluster spread out within it, they produce multiple magnifying caustics that trace a pattern in space like a spider web.

Playing the odds

How likely is such an alignment? Small but not zero, say the astronomers, and they note the spider web of caustics helps by spreading a net. Moreover each caustic is asymmetrical, producing a sharp rise to full magnification if a star approaches from one side, but a much slower rise if it approaches from the other side.

"Depending on which side of the caustic it approaches from, a first star would brighten over hours -- or several months," Windhorst explained. "Then after reaching a peak brightness for several weeks, it would fade out again, either slowly or quickly, as it moves away from the caustic line."

A key attribute of the first stars is that they formed out of the early universe's mix of hydrogen and helium with no heavier chemical elements such as carbon, oxygen, iron, or gold. Blazingly hot and brilliantly blue-white, the first stars display a textbook simple spectrum like a fingerprint, as calculated by the ASU team using the open software instrument Modules for Experiments in Stellar Astrophysics.

Another object potentially visible by the same magnifying effect is an accretion disk around the first black holes to form after the Big Bang. Black holes would be the final evolutionary outcome of the most massive first stars. And if any such stars were in a two-star (binary) system, the more massive star, after collapsing to a black hole, would steal gas from its companion to form a flat disk feeding into the black hole.

An accretion disk would display a different spectrum from a first star as it transits a caustic, producing enhanced brightness at shorter wavelengths from the hot, innermost part of the disk compared to the colder outer zones of it. The rise and decay in brightness would also take longer, though this effect would likely be harder to detect.

Accretion disks are expected to be more numerous because solitary first stars, being massive and hot, race through their lives in just a few million years before exploding as supernovas. However, theory suggests that an accretion disk in a black hole system could shine at least ten times longer than a solitary first star. All else being equal, this would increase the odds of detecting accretion disks.

It's educated guesswork at this stage, but the team calculates that an observing program which targets several galaxy clusters a couple of times a year for the lifetime of the Webb Telescope could find a lensed first star or black hole accretion disk. The researchers have selected some target clusters, including the Hubble Frontier Fields clusters and the cluster known as "El Gordo."

"We just have to get lucky and observe these clusters long enough," Windhorst said. "The astronomical community would need to continue to monitor these clusters during Webb's lifetime."

On beyond Webb

Which raises a point. While the Webb Space Telescope will be a technical marvel, it will not have a long operational lifetime like the Hubble Space Telescope. Launched in 1990, the Hubble Telescope is in low Earth orbit and has been serviced by astronauts five times.

The Webb Space Telescope, however, will be placed at a gravitationally stable point in interplanetary space, 1.5 million kilometers (930,000 miles) from Earth. It has been designed to operate for 5 to 10 years, which might with care stretch to about 15 years. But there's no provision for servicing by astronauts.

Accordingly, Windhorst notes that ASU has joined the Giant Magellan Telescope Organization. This is a consortium of universities and research institutions that will build its namesake telescope on a high and dry mountaintop at Las Campanas Observatory in Chile. The site is ideal for infrared observing.

Upon completion in 2026, the GMT will have a light-collecting surface 24.5 meters (80 feet) in diameter, built from seven individual mirrors. (The Webb Space Telescope's main mirror has 18 sections and a total diameter of 6.5 meters, or 21 feet.) The GMT mirrors are expected to achieve a resolving power 10 times greater than that of the Hubble Space Telescope in the infrared region of the spectrum.

There will be a period during which the Webb Telescope and the Giant Magellan Telescope will both be in operation.

"We're planning to make observations of first-generation stars and other objects with the two instruments," Windhorst said. "This will let us cross-calibrate the results from both."

The overlap between the two telescopes is important in another way, he said.

"The GMT's operational lifetime will continue for many decades into the future. This is unlike the Webb Telescope, which will eventually run out of thruster fuel to maintain its orbit in space."

When that happens, contact with the Webb Telescope will be lost and its mission will come to an end.

Said Windhorst, "One way or another, we are confident we can detect the first stars in the universe."
-end-


Arizona State University

Related Black Hole Articles:

Scientists make waves with black hole research
Scientists at the University of Nottingham have made a significant leap forward in understanding the workings of one of the mysteries of the universe.
Collapsing star gives birth to a black hole
Astronomers have watched as a massive, dying star was likely reborn as a black hole.
When helium behaves like a black hole
A team of scientists has discovered that a law controlling the bizarre behavior of black holes out in space -- is also true for cold helium atoms that can be studied in laboratories.
Star in closest orbit ever seen around black hole
Astronomers have found evidence of a star that whips around a likely black hole twice an hour.
Tail of stray black hole hiding in the Milky Way
By analyzing the gas motion of an extraordinarily fast-moving cosmic cloud in a corner of the Milky Way, Astronomers found hints of a wandering black hole hidden in the cloud.
Hubble gazes into a black hole of puzzling lightness
The beautiful spiral galaxy visible in the center of the image is known as RX J1140.1+0307, a galaxy in the Virgo constellation imaged by the NASA/ESA Hubble Space Telescope, and it presents an interesting puzzle.
Clandestine black hole may represent new population
Astronomers have combined data from NASA's Chandra X-ray Observatory, the Hubble Space Telescope and the National Science Foundation's Karl G.
When will a neutron star collapse to a black hole?
Astrophysicists from Goethe-University Frankfurt have found a simple formula for the maximum mass of a rotating neutron star and hence answered a question that had been open for decades.
Behemoth black hole found in an unlikely place
Astronomers have uncovered a near-record breaking supermassive black hole, weighing 17 billion suns, in an unlikely place: in the center of a galaxy in a sparsely populated area of the universe.
Behemoth black hole found in an unlikely place
Astronomers have uncovered one of the biggest supermassive black holes, with the mass of 17 billion Suns, in an unlikely place: the centre of a galaxy that lies in a quiet backwater of the Universe.

Related Black Hole Reading:

Black Hole (Pantheon Graphic Novels)
by Charles Burns (Author)

Winner of the Eisner, Harvey, and Ignatz Awards

The setting: suburban Seattle, the mid-1970s. We learn from the outset that a strange plague has descended upon the area’s teenagers, transmitted by sexual contact. The disease is manifested in any number of ways — from the hideously grotesque to the subtle (and concealable) — but once you’ve got it, that’s it. There’s no turning back.

As we inhabit the heads of several key characters — some kids who have it, some who don’t, some who are about to get it — what unfolds isn’t the expected battle to fight... View Details


Black Holes (A True Book)
by Ker Than (Author)

Describes how black holes form, their different sizes, how scientists find black holes in space, and if anything can escape from its gravitational pull. View Details


A Black Hole Is Not a Hole
by Carolyn Cinami DeCristofano (Author), Michael Carroll (Illustrator)

Budding astronomers and scientists will love this humorous introduction to the extremely complex concept of black holes. With space facts and answers about the galaxies (ours, and others) A Black Hole is NOT a Hole takes readers on a ride that will stretch their minds around the phenomenon known as a black hole.

In lively and text, the book starts off with a thorough explanation of gravity and the role it plays in the formation of black holes. Paintings by Michael Carroll, coupled with real telescopic images, help readers visualize the facts and ideas presented in the... View Details


Black Holes: A Very Short Introduction (Very Short Introductions)
by Katherine Blundell (Author)

Black holes are a constant source of fascination to many due to their mysterious nature. This Very Short Introduction, addresses a variety of questions, including what a black hole actually is, how they are characterized and discovered, and what would happen if you came too close to one.

Professor Katherine Blundell looks at the seemingly paradoxical, mysterious, and intriguing phenomena of black holes. Outlining their nature and characteristics, both those resulting from the spectacular collapse of heavy stars, and the giant black holes found at the centres of galaxies, she... View Details


The Little Book of Black Holes (Science Essentials)
by Steven Gubser (Author), Frans Pretorius (Author)

Dive into a mind-bending exploration of the physics of black holes

Black holes, predicted by Albert Einstein’s general theory of relativity more than a century ago, have long intrigued scientists and the public with their bizarre and fantastical properties. Although Einstein understood that black holes were mathematical solutions to his equations, he never accepted their physical reality―a viewpoint many shared. This all changed in the 1960s and 1970s, when a deeper conceptual understanding of black holes developed just as new observations revealed the existence of quasars... View Details


Black Hole Blues and Other Songs from Outer Space
by Janna Levin (Author)

The authoritative story of Rainer Weiss, Barry Barish, and Kip Thorne’s Nobel Prize–winning discovery of gravitational waves—by an eminent theoretical astrophysicist and award-winning writer.

With A New Preface

In 1916, Einstein predicted the presence of gravitational waves. One century later, we are recording the first sounds from space, evidence of the waves’ existence caused by the collision of two black holes. An authoritative account of the headline-making discovery by theoretical astrophysicist and award-winning writer Janna Levin, Black Hole Blues... View Details


Black Holes and Time Warps: Einstein's Outrageous Legacy (Commonwealth Fund Book Program)
by Kip S. Thorne (Author), Stephen Hawking (Foreword)

Winner of the 2017 Nobel Prize in Physics

Ever since Albert Einstein's general theory of relativity burst upon the world in 1915 some of the most brilliant minds of our century have sought to decipher the mysteries bequeathed by that theory, a legacy so unthinkable in some respects that even Einstein himself rejected them.

Which of these bizarre phenomena, if any, can really exist in our universe? Black holes, down which anything can fall but from which nothing can return; wormholes, short spacewarps connecting regions of the cosmos; singularities, where... View Details


Death by Black Hole: And Other Cosmic Quandaries
by Neil deGrasse Tyson (Author)

“[Tyson] tackles a great range of subjects . . . with great humor, humility, and―most important― humanity.” ―Entertainment Weekly

Loyal readers of the monthly "Universe" essays in Natural History magazine have long recognized Neil deGrasse Tyson's talent for guiding them through the mysteries of the cosmos with clarity and enthusiasm. Bringing together more than forty of Tyson's favorite essays, ?Death by Black Hole? explores a myriad of cosmic topics, from what it would be like to be inside a black hole to the movie industry's... View Details


Black Hole: How an Idea Abandoned by Newtonians, Hated by Einstein, and Gambled On by Hawking Became Loved
by Marcia Bartusiak (Author)

The contentious history of the idea of the black hole—the most fascinating and bizarre celestial object in the heavens

For more than half a century, physicists and astronomers engaged in heated dispute over the possibility of black holes in the universe. The weirdly alien notion of a space-time abyss from which nothing escapes—not even light—seemed to confound all logic. This engrossing book tells the story of the fierce black hole debates and the contributions of Einstein and Hawking and other leading thinkers who completely altered our view of the universe.
View Details


Black Holes (Kindle Single)
by Bantam

The legendary physicist explores his favorite subject in a pair of enlightening, accessible, and cleverly illustrated essays for curious readers, originally delivered as BBC lectures.
 
“It is said that fact is sometimes stranger than fiction, and nowhere is that more true than in the case of black holes. Black holes are stranger than anything dreamed up by science-fiction writers, but they are firmly matters of science fact.”
 
For decades, Stephen Hawking has been fascinated by black holes. He believes that if we understood the challenges they... View Details

Best Science Podcasts 2018

We have hand picked the best science podcasts for 2018. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Inspire To Action
What motivates us to take up a cause, follow a leader, or create change? This hour, TED speakers explore stories of inspirational leadership, and what makes some movements more successful than others. Guests include high school history teacher Diane Wolk-Rogers, writer and behavioral researcher Simon Sinek, 2016 Icelandic presidential candidate Halla Tómasdóttir, professor of leadership Jochen Menges, and writer and activist Naomi Klein.
Now Playing: Science for the People

#474 Appearance Matters
This week we talk about appearance, bodies, and body image. Why does what we look like affect our headspace so much? And how do we even begin to research a topic as personal and subjective as body image? To try and find out, we speak with some of the researchers at the Centre for Appearance Research (CAR) at the University of the West of England in Bristol. Psychology Professor Phillippa Diedrichs walks us through body image research, what we know so far, and how we know what we know. Professor of Appearance and Health Psychology Diana Harcourt talks about visible...