image title
ASU scientist: There are a range of planets we don't have in our solar system.
Check out the newest and sexiest field in astronomy — exoplanets.
December 23, 2015

ASU astrophysicist an expert on the search for another Earth

One of the best things in science fiction is bizarre alien planets. Ice planets, lava planets, water planets, planets with two suns, planets where you can see Saturn-like rings in the sky.

Nowadays, that’s one of the best things in astronomy too, because all those types of planets actually exist.

Welcome to exoplanets, the newest and sexiest field in astronomy, where in the hunt for alien worlds the Holy Grail is discovering another Earth.

Almost every week another discovery in the field makes the news. Earlier this month researchers found out 10 Jupiter-like planets they studied aren’t as hot and dry as suspected; clouds are hiding signs of water.

Astrophysicist Jennifer Patience of Arizona State University’s School of Earth and Space Exploration is an expert in exoplanets. She is involved in high-precision imaging of exoplanet systems and protoplanetary disks (a rotating circumstellar disk of dense gas surrounding a young newly formed star). She was involved in the first image detection of a multi-planet system around a particular type of star in 2008. She discussed the latest trends in the 23-year-old field.

“There are thousands of exoplanets known — several thousand,” Patience said. “My group is specifically looking for them. … I think people are sometimes surprised to realize how many planets are out there. They’re still being discovered. One of the up-and-coming areas is characterizing those planets. There’s often quite a bit of differences with our own solar system, so it’s a chance to explore the diversity of the planets that are out there.”

The first exoplanet was discovered in the early 1990s. It was found around a pulsar, a remnant of a supernova. It wasn’t seen; it was measured.

“When a planet orbits a star, it has a tiny gravitational tug on the star, just as the star has a tug on the planet,” Patience said. “We measure that shift in the velocity of the star. That’s how the first exoplanet was discovered. We didn’t see it.”

That changed in 2009, when the $600 million Kepler space observatory launched into orbit by NASA, with the aim of determining how common Earth-like planets are across the Milky Way galaxy. What Kepler has turned up is startling.

“There have been real surprises,” Patience said. “A lot of these exoplanets are very different from our own solar system.”

Planets with dual suns have been discovered — think Tatooine in “Star Wars.”

“There are planets with the Tatooine arrangement, with double stars,” she said. “Those are some of the interesting, very different systems compared to our own. There are planets in orbit around a pair of stars. There are also examples of planets where there is a planet around one star, but that star has a neighboring star. You can get different arrangements of the binaries.”

There are a range of planets out there we don’t have in our solar system. Some are giant — 20 times bigger than Jupiter. Some have entire solar systems packed into a tight orbit like Mercury’s. If you were standing on the surface of one, the others could appear like the moon does in Earth’s night sky if they were close enough.

“You could see some amount of the size of the planet,” Patience said.

Many exoplanets are too close to their host stars to be habitable. “They can be up into the thousands of degrees,” Patience said. Most are giants, so they’re gaseous. If they turn out to be rocky, they could potentially be lava worlds.

A planet surrounded by beautiful rings.

One planet scientists have 
dubbed a super-Saturn 
has more than 30 rings 
200 times larger than Saturn’s.

Photo courtesy Ron Miller; 
top image by JPL/Caltech

“If a rocky planet is that close to the host star, you’d have to be thinking about some amount of molten material,” Patience said.

One planet scientists have dubbed a super-Saturn has more than 30 rings 200 times larger than Saturn’s. If it replaced Saturn in our solar system, its rings would be more visible than the moon.

“There’s a lot of diversity out there,” Patience said. “They’re all very interesting, but in very different ways. … We’re really working toward the characterization aspects of these new systems.”

The closest exoplanet is a little more than 16 light-years away (or about 96 trillion miles).

“There are thousands known, and there are many fewer that we’ve been able to investigate the atmospheres,” Patience said. “It’s a lot harder to investigate the atmospheres.”

Depending on the temperature of the star, there is a range of orbits where liquid water could be present. They can’t be too close to the star like Mercury because they’d be too hot. They can’t be too far away like Mars, because they’d be cold.

“It’s also sometimes called the Goldilocks zone,” Patience said. “There is this growing number of planets that are in the habitable zone. For the most part they are around those smaller stars because the orbits that could be searched so far are closer orbits. To catch the habitable zone you need to be around the lower-mass stars.”

There are around 25 Goldilocks planets: Earth-size, and in the right orbit. Last month the most promising Earth-like planet — Kepler 438b — was found to be possibly uninhabitable. The planet is in the Goldilocks zone, but it orbits a cooler low-mass star. This type of star has a lot of flare activity, so the planet is bombarded by intense radiation and plasma flares.

“Although it’s in the liquid water zone, it might have other complications,” Patience said of Kepler 438b.

Kepler 438b is tidally locked to the star, so the same face of the planet is always turned to the star (similar to the moon and Earth). Could there be a thin habitable edge at the line between the star side and the dark side? Imagine living in Arizona, but not being able to go to California because there’s too much radiation, and not being able to go to New Mexico because it’s dark and frigid.

“This is certainly an area that’s under research,” Patience said. “What is the full scope of those effects? … That’s what’s really exciting about this field. It’s a chance to encounter planetary systems that we don’t have analogs of in our own solar system. We can investigate what are the implications of having one hemisphere irradiated and one dark side. What are the wind patterns? What is the climate? There are a lot of interesting questions.” 

image title
ASU engineers are taking concrete pavements to the next level.
December 23, 2015

ASU engineers are ratcheting up research for more resilient concrete pavements

Aging roadways pose a growing threat to transportation infrastructure that’s critical to the health of economies throughout the world.

Beyond the daunting task of funding extensive restoration efforts, there’s an equally pressing challenge to find ways to rebuild major roads that are more sustainable.

The need is one of the main motivating factors behind a new international initiative called Infravation, a combination of infrastructure and innovation.

The European Commission — an offshoot of the European Union — initiated the effort, inviting engineers and scientists in Europe and the United States to propose research projects to develop technological solutions.

The commission considered around 100 proposals. Fewer than 10 have been selected, including two projects to be led by researchers in the United States, one of them by Arizona State University engineer Narayanan Neithalath.

High-performance concrete materials in demand

Neithalath has been experimenting with what are called phase-change materials to produce more resilient concrete surfaces for roads and bridges.

Working with colleagues at the University of California, Los Angeles (UCLA), he is finishing up a National Science Foundation-funded project that is exploring the use of a phase-change material solution for reducing or preventing temperature-related cracks in concrete pavement.

Through the new Infravation project, he and his UCLA partners will expand their work in collaboration with researchers at Delft University of Technology in the Netherlands, the Swiss Federal Institute for Materials Science (commonly known as EMPA) and the Tecnalia Research and Innovation organization in Spain.

Since cement concrete is a major component of transportation infrastructure, countries throughout the world are extremely interested in long-lasting and high-performing concrete materials, Neithalath said.

His Infravation group has been awarded $1.6 million to find out whether concrete solutions containing a phase-change material can significantly enhance the durability of concrete pavements and bridge decks. 

Guys looking cool in a lab.
ASU engineer Narayanan Neithalath (right) will lead an international project to develop ways of making concrete pavements more durable. Civil engineering doctoral student Akash Dakhane will assist him. Photo by Nora Skrodenis/ASU


Helping pavements cope with stress

Phase-change materials are substances that respond to temperature variations by changing their state from solid to liquid or vice versa, and can be sourced from petroleum (such as paraffin wax) or be plant-based.

“We know how the materials perform under laboratory conditions. Now we have to see if it holds up when applied at larger scales and real-life loading and environmental conditions,” said Neithalath, an associate professor of civil, environmental and sustainable engineering in ASU’s Ira A. Fulton Schools of Engineering.

Like other phase-change materials, the substance his team is working with is especially effective at absorbing and releasing thermal energy. It means that over a wide range of temperature variations, it can store significantly more heat per unit of volume than water, rock or masonry.

That ability makes this phase-change material a good choice for mixing with concrete to boost its resistance to crack-inducing stresses. For instance, in hot weather the material can absorb much of the heat, thus protecting the concrete from a level of heat that can trigger fracturing.

“The important thing is to have a material that helps concrete pavements cope with different kinds of stresses put on it,” Neithalath said. “You need materials that can melt or solidify in response to varying environmental conditions without weakening the structural integrity of the pavement.”

Goal is to optimize durability

Beyond how well the phase-change material performs in that particular fashion, his team needs to answer other big questions.

What changes in the road design and construction techniques are necessary to optimize the use of the crack-reducing phase-change materials?

What are the most effective ways to embed phase-change material into vast amounts of concrete?

Can the new system provide enough durability to justify additional costs?

How can this phase-change material be safely disposed of when the new road pavements are eventually replaced?

In addition, it will likely be necessary to devise strategies for use of the material on bridge decks that are different than how the material would be used in pavements for roadways built on solid ground.

Finding answers “will require us to more fully understand the properties of the material and how it will behave in a range of situations,” said Neithalath, who is also on the faculty of the graduate studies program in materials science and engineering.

“I think we can take concrete pavements to the next level.”
— ASU engineer Narayanan Neithalath

Components for progress in place

Fellow ASU civil engineers on the project team, Subramaniam Rajan and Mikhail Chester, will apply their specific expertise to aid Neithalath in pursuit of answers and solutions.

Professor Rajan will provide computer modeling to validate results of extensive experiments with the material.

Assistant professor Chester will perform cost-benefit analysis as well as life-cycle analysis of the new pavement material — a major step in predicting how it will measure up to sustainability expectations.

The project will also provide opportunities for a number of ASU post-doctoral lab assistants and engineering graduate students to get valuable research experience.

“We will have good research teams at each of the institutions in different countries that are partners in this project. We have experts for every component of what we need to accomplish our goal,” Neithalath said. “I think we can take concrete pavements to the next level.”

Joe Kullman

Science writer, Ira A. Fulton Schools of Engineering