Planets

It wasn’t that long ago that astronomers only knew of eight planets (nine before Pluto’s demotion back in 2006) – those here in our own solar system. Now we know of nearly 10,000 planets orbiting stars beyond our sun – known as exoplanets – and that flood of new worlds has ushered in something of a golden age for planetary scientists.

For astronomers like Marta Bryan, an assistant professor at the �ؿ�ζSM Mississauga and in the David A. Dunlap department of astronomy and astrophysics in the Faculty of Arts & Science, it means there’s no better time to be studying these distant worlds.

“This is such a dynamic field,” says Bryan, who joined U of T in January after four years as a postdoctoral researcher at the University of California, Berkeley. Studying the properties of exoplanets provides “a unique opportunity to put ourselves and our world in the broadest of contexts – how does our solar system, our planet and our species fit into our universe?”

Bryan, who specializes in the study of planetary formation and evolution, was recently awarded the Annie Jump Cannon Award from the American Astronomical Society for her work on exoplanets.

As the tally of exoplanets began to grow, astronomers noticed how diverse planetary systems appear to be, with planets varying widely in size, composition and surface temperature. Some orbit very close to their host stars, while others follow orbits comparable to the Earth’s, or to the giant outer planets in our solar system.

“We’ve found thousands of exoplanets, with a huge diversity of properties,” Bryan says. “For me, one of the driving goals in the field is to understand where that diversity comes from. What does the process of planet formation and evolution look like?”

Marta Bryan uses a range of observational techniques to detect and characterize gas giant planets outside our solar system to explore how planetary systems form and evolve (photo by Nick Iwanyshyn)

While much research on exoplanets has focused on the search for Earth-like worlds, Bryan is interested in gas giant planets, analogous to Jupiter and Saturn in our own solar system. That’s because their sheer heft means they play an important role in determining how smaller planets in the same system evolve.

As Bryan puts it, gas giant planets “dominate the dynamics” of whatever system they’re in. Which means that learning about gas giants can, in fact, help us understand something about Earth-like planets – worlds whose evolution may have been affected by the presence of these much more massive bodies.

As a result, Bryan says, “gas giant planets are an obvious place to start if we want to understand the physics of planet formation.”

The gas giant planets in our own solar system are thought to have played a crucial role over the past five billion years. Jupiter, for example, is believed to have migrated inward before reversing direction and ending up in its current position. Jupiter’s foray into the inner part of the solar system is thought to have stunted the growth of the inner planets, particularly Mars, by scattering some of the gas and dust that might otherwise have been gravitationally pulled toward the red planet.

“We think that Jupiter and Saturn played a dominant role in the early history of our solar system, helping to shape the formation and evolution of our terrestrial planets,” Bryan says. “As a result, we want to understand in the broader extrasolar context what role gas-giant analogs to Jupiter and Saturn have played in shaping the lives of terrestrial worlds.”

The future looks bright – data from the James Webb Space Telescope is already pouring in. Bryan is especially excited about large, ground-based telescopes with mirrors up to 30 metres across, which are currently being planned. These next-generation telescopes may even reveal “biosignatures” on other worlds – signs of life that can be inferred from the composition of a planet’s atmosphere.

And if astronomers do end up finding conclusive evidence of life beyond our own planet, such a discovery “would definitely be transformational,” Bryan says.

Planets in TRAPPIST-1 orbiting in synchronized harmonies, U of T astrophysicist and musicians discover

ullahnor — Wed, 10 May 2017 16:11:32 +0000

Planets in TRAPPIST-1 orbiting in synchronized harmonies, U of T astrophysicist and musicians discover

ullahnor Wed, 05/10/2017 - 12:11

Don Campbell

Author legacy

Don Campbell

Topic

Subheadline

They have created a digital symphony to highlight the unique configuration which saves TRAPPIST-1 from destruction

NASA's discovery of the TRAPPIST-1 planetary system earlier this year created excitement after three planets were found to be in the star's habitable zone. But it also created confusion since the system appeared to be highly unstable, in danger of smashing itself to bits.

Now a U of T astrophysicist may have helped solve that puzzle – with jazz music and animation.

Dan Tamayo, a postdoc researcher at U of T Scarborough’s Centre for Planetary Science, fellow astrophysicist Matt Russo, who plays jazz, and musician Andrew Santaguida teamed up with a Toronto-based animation studio to illustrate the planetary system's remarkable configuration. Speeding up the planets’ orbital frequencies into the human hearing range, they've created an astrophysical symphony of sorts, playing out more than 40 light years away.

‘Peter Pan’ radio galaxies that never grow old: U of T astronomer part of discovery of 1,500 young galaxies

ullahnor — Mon, 13 Mar 2017 18:47:55 +0000

‘Peter Pan’ radio galaxies that never grow old: U of T astronomer part of discovery of 1,500 young galaxies

ullahnor Mon, 03/13/2017 - 14:47

Cutline

An artist’s impression illustrates high-speed jets from supermassive black holes. The jets have very strong emissions at radio wavelengths (photo image by ESA/Hubble, L. Calçada/ESO)

Chris Sasaki

Author legacy

Chris Sasaki

Topic

Breaking Research

Dunlap

Faculty of Arts & Science

Galaxy

Space

Planets

A team of astronomers has doubled the number of known young, compact radio galaxies – galaxies powered by newly energized black holes. The newly found 1,500 galaxies will help astronomers understand the relationship between the size of these radio sources and their age, as well as the nature of the galaxy itself.

In particular, it will help astronomers understand why there are so many more young radio galaxies than old.

“These compact galaxies used to be as rare as hen’s teeth,” says Professor Bryan Gaensler, a co-author on the paper and director of the Dunlap Institute for Astronomy & Astrophysics at the �ؿ�ζSM. “But now we’ve been able to discover a huge number of new cases. This breakthrough will let us begin to study the overall properties of these unusual and important objects.”

A radio galaxy is a galaxy that shines brightly at radio wavelengths. A super-massive black hole – typically with the mass of millions of suns – powers this outpouring of energy.

Gas and dust fall into the black hole, releasing vast amounts of energy. The energy is focused into two jets of particles, travelling in opposite directions at nearly the speed of light. As the jets blast through the galaxy, each generates its own lobe or hot-spot of radiation as it interacts with the gas in the galaxy.

In a survey of ninety thousand radio galaxies, the astronomers identified the radio compact galaxies among them. The results are described in a paper published Feb. 20 in the Astrophysical Journal.

“We do not understand how radio galaxies evolve,” says Joseph Callingham, a postdoctoral researcher from the Netherlands Institute for Radio Astronomy (ASTRON) and lead author on the paper describing the result.

“For a long time, we thought all small galaxies evolved into massive galaxies. However, we have now found far too many small galaxies relative to the large ones. This suggests some never make it to the ‘adult phase’.”

According to one model, compact radio sources are young because the jets have not had time to reach far beyond the central black hole. The hot-spots are relatively close together and look like compact sources. Over time, the jets reach farther out into the galaxy and even beyond its confines; the hot-spots are farther from each other, and they are seen as a more extended, double-lobed source.

In this simple model, the overabundance of young, compact radio galaxies raises the question: why don’t young, compact radio galaxies mature into old, extended radio galaxies?

However, another model argues that the relationship between the age and observed size of a radio galaxy is not so straightforward. That’s because a compact source may be compact not because it’s young, but because gas within the galaxy is dense enough to prevent the jets from extending far from the central black hole, meaning it remains compact despite its age.

“This study shows that it is possible a dense environment near the heart of the galaxy hinders and stops galaxy growth,” says Callingham, who did much of the research as a PhD student with the Australian Centre for All-shy Astrophysics (CAASTRO).

The astronomers made the discovery using data gathered with the Murchison Wide-field Array (MWA), an interferometric radio telescope in the Western Australian outback. The discovery was possible because, unlike conventional radio telescopes that observe tiny patches of the sky at a time, the MWA sweeps large areas of the sky and is capable of observing across a broader range of wavelengths.

What NASA’s big discovery means for the future of planetary research: U of T astronomer explains

ullahnor — Thu, 23 Feb 2017 18:44:22 +0000

What NASA’s big discovery means for the future of planetary research: U of T astronomer explains

ullahnor Thu, 02/23/2017 - 13:44

Cutline

Artist's impression of the surface of one of the planets (credit NASA/JPL-CALTECH)

Don Campbell

Author legacy

Don Campbell

Topic

Yesterday’s record-breaking announcement by NASA that seven Earth-sized planets have been discovered orbiting a single star is being hailed as an “accelerated leap forward” in the search for extraterrestrial life.

Not only did it set a new record for the greatest number of habitable-zone planets found orbiting a single star – three in this case – but it also means researchers may soon be able to study the atmospheres of these planets since they're so close.

Dan Tamayo (below) is a researcher at U of T Scarborough’s Centre for Planetary Science (CPS). He spoke to U of T's Don Campbell about what NASA’s big discovery means for the future of research on planets outside our solar system.

How big of a discovery is this and why should we be excited?

This is a HUGE deal, way bigger than previous discoveries. These are all small planets, roughly the size of Earth, and we expect there are billions of them in our galaxy. But planets this small are really hard to detect. In fact, we’ve only just started detecting planets this small in the last few years.

It’s exciting because these planets may have a solid surface capable of hosting biological life. Most of the thousands of exoplanets we’ve discovered are bigger and therefore probably more gaseous like Neptune or Jupiter.

Of the small planets we do discover, the vast majority are very close to their host star where it’s easier to detect them. This means they’re typically at scalding hot temperatures where it’s difficult to imagine life evolving. The planets in the TRAPPIST-1 system are also very close, but the star is so tiny and lukewarm – as far as stars go – that their surface temperatures are likely in the range to host liquid water. So these are prime candidates to look for life.

What does this discovery mean for future exoplanet research, especially the James Webb Space Telescope set to launch in 2018?

The James Webb Space Telescope is the successor to Hubble and is right in the sweet spot to observe the atmospheres of these planets. Because the system is so close to Earth it means we can get great information on their atmospheres. It may be possible to detect whether or not these planets have ozone in their atmospheres. That wouldn’t be a slam dunk for life but would easily make them prime exoplanets to study.

Why is the “habitable zone” so important in the search for life beyond our solar system?

We know that liquid water is essential to life on Earth so it makes sense to look for life on planets capable of hosting water. The habitable zone is the Goldilocks range of distances from a star that’s just right for life – so where it’s not too hot or not too cold for surface water. Of course, not all life in the universe needs to rely on liquid water but then what would we look for? Pragmatically, looking for water is a good starting point.

The planets “e,” “f,” and “g” — are directly in the “habitable zone” of this star system (credit NASA)

How does the TRAPPIST-1 star compare to the sun? What does the planets being tidally locked mean in terms of harbouring conditions for life?

This system is crazy. The star is puny, only about the same size as Jupiter but is about 100 times more massive. The planets are packed extremely close to the star. The innermost planet is only about four times farther from the star than our moon is from us. The outermost planet orbits about 10 times closer than Mercury does around the sun.

It’s true that these planets could be tidally locked like the moon is around us, always keeping the same face pointed toward the star. That would mean hot temperatures on the star-facing side and frigid ones on the other side, unless you had a thick atmosphere to move warm air around. That certainly poses challenges for life, but anything’s possible. It’s possible that life could thrive in a band around the region of the planet that separates the day side from night.

Since the system is relatively close will it make discovering life, or at least the conditions necessary for life, easier?

A real game changer is that TRAPPIST-1 is close to us. Forty light years may seem incredibly far, but that makes it one of the 300 closest stars to us. By comparison, the previously known Earth-like planets in the habitable zone are roughly 1,000 light years away. That makes it all but impossible to study their atmospheres with current technology. Not only does TRAPPIST-1 open that window in a big way, we have 7 planets to look at!

The system is also positioned in such a way that from our point of view on Earth, the planets cross in front of their star. This makes it possible to learn about the chemistry on the planet by analyzing the starlight as it passes through the atmosphere, and seeing the signature of different chemical compounds absorbing the light.

Planets

In search of other worlds: Astronomer explores how planets form and evolve

Planets in TRAPPIST-1 orbiting in synchronized harmonies, U of T astrophysicist and musicians discover

Read more at The New York Times

‘Peter Pan’ radio galaxies that never grow old: U of T astronomer part of discovery of 1,500 young galaxies

What NASA’s big discovery means for the future of planetary research: U of T astronomer explains