Space

Research and Innovation

Subheadline

A team of researchers that includes a U of T postdoc may have solved the "final parsec problem" of astrophysics

A team of astrophysicists that includes the ��߲ݴ�ý’s Gonzalo Alonso-Álvarez has shown that pairs of supermassive black holes can merge together into a single, larger black hole – a major breakthrough in addressing what is known as the "final parsec problem."

Gonzalo Alonso-Álvarez (supplied image)

The longstanding astrophysics problem refers to a discrepancy between the detection of gravitational signals permeating the universe – which astrophysicists previously hypothesized had emanated from millions of merging pairs of supermassive black holes (SMBHs) – and theoretical simulations which showed that the approach of SMBHs stalls when they’re roughly one parsec (about three light years) apart.

Not only did the final parsec problem conflict with the theory that merging SMBHs were the source of the gravitational wave background, it was also at odds with the theory that SMBHs – each billions of times more massive than our Sun – grow from the merger of less massive black holes.

The new research, published in Physical Review Letters, has shown that pairs of SMBHs can indeed break through the one-parsec barrier and merge into a single black hole. This is demonstrated by calculations showing that SMBHs continue to draw closer because of previously overlooked interactions with particles within the vast cloud of dark matter surrounding them.

“We show that including the previously overlooked effect of dark matter can help supermassive black holes overcome this final parsec of separation and coalesce,” says Alonso-Álvarez, a post-doctoral fellow in the department of physics at U of T’s Faculty of Arts & Science and the department of physics and Trottier Space Institute at McGill University, who is first author on the paper. “Our calculations explain how that can occur, in contrast to what was previously thought.”

SMBHs are thought to lie in the centres of most galaxies. When two galaxies collide, the SMBHs fall into orbit around each other; as they revolve around each other, the gravitational pull of nearby stars tugs at them and slows them down, causing them to spiral inward toward a merger.

Previous merger models showed that when the SMBHs approached to within roughly a parsec, they begin to interact with the dark matter cloud or halo in which they are embedded. These models indicated that the gravity of spiraling SMBHs throws dark matter particles clear of the system.

The new model introduced by Alonso-Álvarez and co-authors James Cline, a professor at McGill University and the European Organization for Nuclear Research (CERN) in Switzerland, and Caitlyn Dewar, a graduate student at McGill, reveals that dark matter particles interact with each other in such a way that they are not dispersed. The density of the dark matter halo remains high enough that interactions between the particles and the SMBHs continue to degrade the SMBH’s orbits – clearing a path to a merger.

“The possibility that dark matter particles interact with each other is an assumption that we made, an extra ingredient that not all dark matter models contain,” says Alonso-Álvarez. “Our argument is that only models with that ingredient can solve the final parsec problem.”

The background hum generated by these colossal cosmic collisions is made up of gravitational waves of much longer wavelength than those first detected in 2015 by astrophysicists operating the Laser Interferometer Gravitational-Wave Observatory (LIGO). Those gravitational waves were generated by the merger of two black holes, both some 30 times the mass of the Sun.

The background hum has been detected in recent years by scientists operating the Pulsar Timing Array. The array reveals gravitational waves by measuring minute variations in signals from pulsars, rapidly rotating neutron stars that emit strong radio pulses.

In addition to providing insight into SBMH mergers and the gravitational wave background signal, the new result also provides a window into the nature of dark matter. “Our work is a new way to help us understand the particle nature of dark matter,” says Alonso-Álvarez. “We found that the evolution of black hole orbits is very sensitive to the microphysics of dark matter and that means we can use observations of supermassive black hole mergers to better understand these particles.”

For example, the researchers found that the interactions between dark matter particles they modeled also explains the shapes of galactic dark matter halos.

“We found that the final parsec problem can only be solved if dark matter particles interact at a rate that can alter the distribution of dark matter on galactic scales,” says Alonso-Álvarez.

“This was unexpected since the physical scales at which the processes occur are three or more orders of magnitude apart. That’s exciting.”

In photos: Under cloudy skies, U of T community gathers to experience near-total solar eclipse

Christopher.Sorensen — Tue, 09 Apr 2024 14:22:01 +0000

In photos: Under cloudy skies, U of T community gathers to experience near-total solar eclipse

Christopher.Sorensen Tue, 04/09/2024 - 10:22

Cutline

The April 8 solar eclipse in the skies over U of T Mississauga, where the clouds parted just in time to give watch party attendees a thrilling spectacle (photo by Nick Iwanyshyn)

Topic

Skies darkened and temperatures dropped as the solar eclipse swept across the ��߲ݴ�ý’s three campuses Monday, bringing community members together to marvel at the celestial spectacle.

Hundreds of community members gathered outside and donned safety glasses to gaze skyward in hopes of witnessing the eclipse from the three campuses, which were adjacent to the path of totality. Others tuned into a livestream hosted by U of T’s Dunlap Institute for Astronomy & Astrophysics.

While gathering clouds obscured the sun around Greater Toronto, the skies cleared just in time to give a lucky few a clear view of the rare astronomical alignment – including those who gathered for a free viewing party at U of T Mississauga.

Here’s how the day unfolded through the lenses of photographers at the university:

(photo by Matthew Volpe)

On U of T’s St. George campus, hundreds pulled out their phones to capture the CN Tower as the city lights pierced through a blackened mid-day sky.

(photo by Nick Iwanyshyn)

Clouds gave way to clear skies at just the right moment for hundreds of people gathered at U of T Mississauga to witness the solar eclipse.

(photo by Nick Iwanyshyn)

While Mississauga was not in the path of totality, the near-total eclipse turned the sky slate grey and deep blue, while a chill in the air cooled the warm spring day.

(photo by Dan Weaver)

At U of T Scarborough, community members convened outside the Science Wing as overcast skies loomed over the Ma Moosh Ka Win Trail.

(photo by Nick Iwanyshyn)

A station set up by Vera Velasco, a U of T Mississauga plant physiologist at Growth Facilities research greenhouse and growth chambers, walked attendees at the viewing party through an experiment tracking how the eclipse impacts photosynthesis. As the eclipse occurred, Velasco and fellow researchers also showed its colours using a spectrometer.

(photo by Nick Iwanyshyn)

Astronomer Marta Bryan, an assistant professor in U of T Mississauga’s department of chemical and physical sciences, spoke to the crowd about the science behind the solar eclipse, complete with a demonstration from some of the younger audience members playing sun, moon and Earth.

(photo by Nick Iwanyshyn)

While it's possible to see a total solar eclipse from somewhere on Earth every few years, it will be another 120 years before viewers in southern Ontario are treated to an eclipse as total as the one on April 8. "It's truly a once-in-a-lifetime event for all of us," Bryan says.

Read a Q&A with astrophysicist Laurie Rousseau-Nepton about Indigenous perspectives on the eclipse

Total solar eclipse is a cosmic marvel to be shared with loved ones – in keeping with Indigenous teachings

Christopher.Sorensen — Fri, 05 Apr 2024 20:27:49 +0000

Total solar eclipse is a cosmic marvel to be shared with loved ones – in keeping with Indigenous teachings

Christopher.Sorensen Fri, 04/05/2024 - 16:27

Cutline

Laurie Rousseau-Nepton, an assistant professor in U of T’s David A. Dunlap department of astronomy and astrophysics and the Dunlap Institute for Astronomy & Astrophysics, says she’s planning to experience the eclipse alongside a sea of spectators at Montreal’s Parc Jean-Drapeau (supplied image)

Adina Bresge

Topic

Eclipse

Indigenous

Subheadline

"It will probably take 100 years before we get to see another one,” says astrophysicist Laurie Rousseau-Nepton of U of T’s Dunlap Institute"

��߲ݴ�ý astrophysicist Laurie Rousseau-Nepton is brimming with anticipation for her first total solar eclipse.

As eager as she is to witness the celestial spectacle on Monday, Rousseau-Nepton says she’s equally as excited to share in the communal awe of people coming together to marvel at the cosmos.

An assistant professor in the Faculty of Arts & Science’s David A. Dunlap department of astronomy and astrophysics and Dunlap Institute for Astronomy & Astrophysics, Rousseau-Nepton says she’s planning to experience the eclipse alongside a sea of spectators at Montreal’s Parc Jean-Drapeau.

“We’re all going to be there experiencing this – most of us for the first time, and maybe for the only time in our lives,” she says. “It will be so special not only for me, but for everybody that will be there.”

Rousseau-Nepton recently spoke to U of T News about this rare astronomical alignment, the scientific opportunities it presents and Indigenous knowledge about eclipses.

What makes this eclipse special?

The upcoming eclipse on April 8th is a total solar eclipse that will be visible in the south part of the country close to major city centres. That means a lot of people will be able to see a total solar eclipse, which is extremely rare. It will probably take 100 years before we get to see another one.

We are very lucky on Earth. Our moon is just about the right size and distance to create this beautiful little display. When the moon is positioned between us and the sun, it will block out the light – and for a few minutes, it will be completely dark. We’ll see things that we never see normally: stars during the day, some planets as well, and the sun’s corona.

This eclipse is also happening close to the maximum of the sun cycle. The sun has a magnetic cycle that lasts about 11 years, and the maximum is expected to be in 2025. That means there’s going to be more sunspots, more solar eruption and people who are able to see auroras in the North will get to see some beautiful displays.

If we’re really lucky and there’s a solar eruption at the same time, we’ll be able to see features of the sun beyond the corona. It’s a little bit like winning the lottery. It might not happen, but it is possible.

What are some of the scientific opportunities this eclipse presents?

During totality, the moon will block the sunlight completely – you’ll still be able to see the moon, but it’ll look slightly different.

The light that will be visible on the surface of the moon is actually the light that first bounces on the Earth’s atmosphere, then goes back onto the moon and back to us. So that light is ultimately light from the Earth’s atmosphere glow. That’s something we can study by pointing instruments at the moon in that moment to get a glimpse of the Earth’s glow and measure it.

What does Indigenous Knowledge tell us about eclipses?

In the Innu community, we have this hero called Tshakapesh – he is known as the man on the moon. After a long life full of adventures, he ended up on the moon and that’s where he is now, looking at us. In one story, Tshakapesh was hunting and trapping when he felt like something was following him. He wanted to trap it, so he put a snare where the snow had melted on a very defined path. And the next morning, the sun got trapped into it. That story is closely related to a lunar eclipse of the sun, when the moon is slightly farther away from us, so we see a line of light around the sun during totality. That line of light represents the snare that Tshakapesh used to capture the sun. The story also involves animals that release the sun – and during the eclipse, we can see some constellations and stars that represent the spirits of those animals.

Across Canada, in many Indigenous stories the eclipse is often a sign of peace. For the Haudenosaunee, the Great Law of Peace was signed by the Six Nations during a total solar eclipse nearly 1,000 years ago. The eclipse is also related to Grandmother Moon, the Skywoman that came down to Turtle Island. During the eclipse, Grandmother Moon meets with someone from her family, so it’s a special moment that they get to see each other for a few hours before leaving again for a long time. It’s seen as a great time for reunion, peace and spending time with your family.

What are your tips for viewing the eclipse?

First, we want to protect our eyes and the best way to do that is with solar eclipse glasses – and you want to be careful with which ones you buy to make sure they’re certified.

If you want to take photos of eclipse, you might be able to get good images during the moment of totality because the lack of sunlight will create a lot of contrast. But during the partial eclipse, the intense sunlight can cause significant glare that will make it hard to see all the details. A good trick is to put those solar eclipse glasses in front of the lens of your camera, which will dampen the amount of sunlight coming in so you can better capture the eclipse.

As for location, it might be nice to have some elevation because the eclipse generates a shadow that you can see from up high. If you really want to see the total eclipse, I would suggest to be mobile in a car, or any way you can move to another place if a cloud comes by. But ultimately, I would say the most important thing is to experience the eclipse with people you love. So, wherever you are, it’s fine.

Watch a video about Indigenous perspectives on the eclipse

Register for the Dunlap Institute’s eclipse livestream

U of T astrophysicist offers tips for enjoying April 8 solar eclipse

Christopher.Sorensen — Mon, 01 Apr 2024 14:01:04 +0000

U of T astrophysicist offers tips for enjoying April 8 solar eclipse

Christopher.Sorensen Mon, 04/01/2024 - 10:01

Cutline

Special eclipse glasses are a must for looking safely at the sun – particularly in Toronto, which will be just outside the path of the total eclipse on April 8 (photo by Don Campbell)

Topic

Subheadline

"The further you travel towards the central line of the total eclipse, the longer you will be able to experience it"

Being in the path of a total solar eclipse is rare. Since it’s only visible across a thin stretch of the Earth’s surface, it only happens once every 375 years on average.

While Toronto will only get a partial eclipse on April 8, a total eclipse will be viewable just a short distance from the city.

“If you have the chance to take the day off to go and see it, I strongly encourage you to do so,” says Hanno Rein, an astrophysicist at the ��߲ݴ�ý. “It's a rare event and it's worth it.”

Writer Don Campbell spoke to Rein, an associate professor in the department of physical and environmental sciences at U of T Scarborough, for his advice on the best locations to watch the total eclipse, tips for safe viewing and why it promises to be a memorable event for millions.

Why do you think we are so captivated by a solar eclipse?

The rarity of an eclipse makes it very special. Beyond that, it'll be completely dark in the middle of the day. If that is not captivating, I'm not sure what is!

What can those in Toronto expect to see on April 8?

Toronto will only get a partial eclipse, which is still very exciting – but it’s very different from seeing a total eclipse. Even one per cent of sunlight is still very bright so you won’t see prominences in the sun's corona, which are the loops of plasma that extend out from its surface, or stars in the sky.

If you want to see a total eclipse in Toronto, you will be out of luck. The next one takes place in 2144.

Where can we view a total eclipse?

If you live in Toronto, you will need to travel. Burlington is the first city south-west of Toronto where you can see the total eclipse for a few seconds. The further you travel towards the central line of the total eclipse, the longer you will be able to experience it. Buffalo is almost exactly on the central line and totality will last there for about four minutes.

Port Hope is the first town east of Toronto where you can see the total eclipse for a few seconds. In Kingston you can see the total eclipse for about two minutes. If you make it across the border to Watertown, N.Y., by 3:25 p.m., then you will experience a total eclipse for about four minutes.

I’ve made a map that shows where and when the eclipse shadow will take place over the GTA. I also created a free app that calculates accurate timing of the eclipse and what it will look like based on your location.

This map created by U of T Scarborough astrophysicist Hanno Rein charts the eclipse shadow across southern Ontario.

What should we do to safely view the eclipse?

Do not look directly at the sun. I can’t emphasize that enough. You can do permanent damage to your eyes if you do. If you’re in Toronto, you will need eclipse glasses at all times to safely look at the sun. Sunglasses, even if they are very dark, or other home-made filters, are not safe.

Some places, like the Toronto Public Library, are handing out glasses for free. At U of T Scarborough, we handed out 1,000 pairs over the past month to students, staff and faculty, but unfortunately, we are all out. You can also buy glasses online, but make sure not to get ripped off. Glasses selling for more than $3 or $4 per pair are a scam.

Do you have any other tips for viewing the eclipse?

I recommend not taking pictures during the eclipse because it will be over quickly. Just relax and enjoy the experience. There will be millions of people taking photos and many people will be using fancy camera gear, so there will be plenty of photos online to appreciate afterwards.

Be sure to check the forecast. You might be able to travel to an area with no clouds. For this time of year in the GTA there is a 60 to 70 per cent chance of cloud coverage. If there are clouds, it will still get very dark, but you won’t see the corona (outermost part of the atmosphere around the sun) during totality, which is disappointing.

Roads and public transit will likely be very busy, so pack some drinks and food and head out before sunrise to beat the traffic. Try not to stand on a busy road because drivers will be distracted during the eclipse. It’s also possible that streetlights might turn on, so try to find an area where there are no streetlights.

Register to watch the Dunlap Institute’s livestream of the eclipse

'A black box in astronomy knowledge': PhD researcher probes the earliest stars in the universe

Christopher.Sorensen — Tue, 26 Mar 2024 18:20:25 +0000

'A black box in astronomy knowledge': PhD researcher probes the earliest stars in the universe

Christopher.Sorensen Tue, 03/26/2024 - 14:20

Cutline

PhD researcher Margaret Ikape presents at the Astronomy on Tap T.O. event (photo by Alicia Richardson)

Michael Pereira

Topic

Astronomy & Astrophysics

Graduate Students

Subheadline

Margaret Ikape is working to determine the properties of the first stars and how they influenced everything that followed

As a child, Margaret Ikape had a prime view of the stars from her hometown of Lagos, Nigeria.

“When I was really young, I saw a shooting star. And that got me looking up at the night sky a lot more,” Ikape says. She recalls thinking: “Can I count all the stars? Can I really go to a star? What would it be like if I could really go to a star? How long would it take?”

Today, Ikape is still looking at stars with the same curiosity, albeit ones that are much farther away. A PhD researcher at the ��߲ݴ�ý’s Dunlap Institute for Astronomy & Astrophysics and David A. Dunlap Department of Astronomy & Astrophysics, she’s working to tell the story of the first stars in the universe, and how they influenced everything that followed.

Theory predicts that ultraviolet light from the first stars was so powerful that it ionized — or split — some of the first hydrogen atoms back into protons and electrons. This period of cosmic history is known as the Epoch of Reionization (EoR). During this time, the first stars and galaxies began to form, and with them, the universe as we know it today.

Ikape is working to determine the properties of these first stars, like how big they were and how long the reionization took. “That period is like a black box in astronomy knowledge. We know it happened, because the universe is ionized today, but we don’t know many details about it,” Ikape says.

A representation of the evolution of the universe over 13.77 billion years (image by NASA / WMAP Science Team)

Current optical telescopes cannot see back far enough to capture the EoR, so Ikape uses thousands of computer simulations to reimagine it and test theories in a kind of virtual sandbox shaped by what we know of the universe. Some of these simulations require significant processing power and must be run through the “Helen” computing cluster, named after renowned Canadian astronomer Helen Sawyer Hogg.

Ikape also learns about the EoR by studying the first light emitted in the universe, the Cosmic Microwave Background (CMB). As light from the CMB travels to Earth, it passes through all that is between us and the point in cosmic history at which the CMB was emitted, approximately 380,000 years after the Big Bang. Ikape can isolate how light from the CMB was impacted by the EoR and analyze it to tell us more about this time.

“Margaret’s work connects models and simulations of how the first stars in the universe lit up and ionized the surrounding gas with our observations of the cosmic microwave light—so she is the detective piecing the story together,” says Associate Professor Renée Hložek, Ikape’s PhD supervisor.

Ikape has forecasted that a new generation of telescopes will unlock more details about this mysterious period and the universe’s first stars, including the Simons Observatory and the fourth-generation ground-based cosmic microwave background experiment, or CMB-S4. She co-authored research that predicts that the CMB-S4 will help scientists close in on when the EoR began and how long it lasted.

A nine-year Wilkinson Microwave Anisotropy Probe (WMAP) heat map of temperature fluctuations in the CMB (photo by NASA/WMAP)

When she isn’t unpacking the mysteries of distant stars, Ikape is involved in outreach initiatives on the ground.

She’s an instructor with the Pan-African School for Emerging Astronomers, a bi-annual school for emerging astronomers in Africa that aims to introduce astronomy undergraduate students to research practices and career avenues in the field, and participated in its inaugural program in Zambia in 2022.

In Toronto, Ikape was recently a speaker at Astronomy on Tap and has given presentations on astronomy at libraries, high schools and even a long-term care home.

“We are lucky to have students like Margaret at the Dunlap Institute; she combines her scientific curiosity with a passion for sharing what she learns with the broader community and training the next generation of bright minds,” Hložek says.

“The universe fascinates me a lot and I’m super excited every time I think about it," Ikape says. "So I think that everybody should know about it.”

U of T researcher seeks out new insights on the universe's oldest galaxies

Christopher.Sorensen — Thu, 08 Feb 2024 19:27:46 +0000

U of T researcher seeks out new insights on the universe's oldest galaxies

Christopher.Sorensen Thu, 02/08/2024 - 14:27

Cutline

Jacqueline Antwi-Danso, a postdoctoral researcher with the David A. Dunlap department of astronomy and astrophysics, is studying massive galaxies that formed “when the universe was still just a baby” (supplied image)

Chris Sasaki

Topic

Astronomy & Astrophysics

Black

Indigenous

Statistical Sciences

Subheadline

"We're trying to understand why these galaxies formed the way they did and how they became so big so quickly"

Jacqueline Antwi-Danso remembers a book from her junior high school library describing how stars are born and how the most massive stars die in gigantic explosions called supernovae.

“The book explained that there were objects out in space that gave off so much energy we could see and study them and make precise observations of their physical properties,” says Antwi-Danso, who credits her parents for nurturing her interest in education and reading while growing up in Ghana. “That just blew my mind.”

Today, Antwi-Danso is an NSERC Banting postdoctoral fellow at the ��߲ݴ�ý’s David A. Dunlap department of astronomy and astrophysics in the Faculty of Arts & Science. Her work focuses on studying massive galaxies that formed “when the universe was still just a baby.”

She is also active in supporting Black, Latinx and Indigenous women who are interested in a career in science.

She recently spoke to U of T’s Chris Sasaki about her career, research and goals.

Was there an important milestone in your journey to becoming an astronomer?

After high school, my plan was to take a gap year to figure out if I wanted to stay in Ghana and do something in the sciences at the university level or go elsewhere.

That’s when an opportunity came my way. There was a program run by the American Embassy in Accra for Ghanaian high school students interested in studying in the U.S. It provided mentorship for things like how to apply to schools in the U.S., how to write a good college application and how to select courses. They also helped you think about what you wanted to do in your career.

It was a big turning point in my life when I was selected to join the program. That’s how I learned about opportunities outside of Ghana and realized that if I was going to study astronomy, I would have to leave because we don't have astronomy at the collegiate level. And so, I made my decision to study astronomy at Texas Christian University.

Large, relatively nearby galaxies like this one took billions of years to form. Antwi-Danso is trying to determine how large galaxies in the very distant universe formed in a small fraction of that time (photo by ESA/Hubble & NASA, D. Jones Acknowledgement: G. Anand, L. Shatz.)

As an astronomer, what questions are you trying to answer?

I study massive galaxies in the very distant universe – some of the very first structures that formed after the Big Bang nearly 14 billion years ago. We're trying to understand why these galaxies formed the way they did and how they became so big so quickly. We’re finding them at increasingly earlier times, as far back as when the universe was just four per cent of its current age.

This goes against our understanding of the hierarchical formation of large structures – where massive galaxies like our Milky Way galaxy were formed from the merger of galaxies that were formed from stars, which, in turn, formed from clouds of gas and dust.

For our galaxy, it took billions of years to attain its current stellar mass. These distant, massive galaxies had only a fraction of the time to go through this process, so we have no idea how they formed so quickly. So, one of two things is happening: either there's something wrong with our observations or we need to revise our current models. That's the big problem I'm working on and I’m actually looking for a summer undergraduate student to work on this project.

Jacqueline Antwi-Danso speaks to students at a meeting of the American Astronomical Society (supplied image)

You’re working to support Black, Indigenous and Latinx women in science. Can you tell me more about that?

The League of Underrepresented Minoritized Astronomers (LUMA) is a peer mentoring organization for women in astronomy, physics and the planetary sciences that was formed in 2015 by Catherine Espaillat, who is the director of the Institute for Astrophysical Sciences at Boston University. She started LUMA because, as a Dominican American grad student, she felt isolated.

There weren’t many people in her field who looked like her, with whom she shared backgrounds. So, she created LUMA to be a community of people with similar experiences who could provide each other with support. I joined because I also realized there weren't many people in my field who looked like me. There were even fewer African astronomers. And, like Catherine, I wanted a place where we could come together as a community and support each other.

Do have you have plans to do the same type of work here in Canada?

I would like to continue this work, so I've been learning about and trying to understand what the Canadian science landscape looks like. I think the challenge in Canada is similar to the challenge that LUMA faces in the U.S. – there are very few Black, Indigenous or Latinx women in science in either country. So, yes, I would like to do similar work here. I just don't know what that looks like yet.

What about in Ghana?

One thing that I had in mind was trying to create some sort of pipeline for students in Ghana who might be interested in astronomy and might want to study in the U.S. or Canada. There are challenges, of course, but I’m talking to people who have been involved in similar projects and have found solutions to these challenges. For example, it might mean helping by providing mentorship to students who are already interested in physics and to students who are a little further along in their studies. I'm hopeful there are a number of ways to make this work.

How do you feel about receiving the NSERC Banting fellowship?

I’m very grateful and humbled to receive it. For me, it represents an exciting opportunity to work independently on my research, especially at U of T with all the people in the Dunlap Institute (for Astronomy & Astrophysics), the department of astronomy and astrophysics, CITA (Canadian Institute for Theoretical Astrophysics) and the department of statistical sciences. I feel like U of T is the perfect place for me because I’m combining astronomy with statistics and cosmological simulations to understand these really massive, distant galaxies. I’m having the time of my life, and I’m looking forward to seeing what the next few months will bring.

With the launch of its first satellite, student team charts a course to new knowledge

rahul.kalvapalle — Fri, 19 Jan 2024 17:44:03 +0000

With the launch of its first satellite, student team charts a course to new knowledge

rahul.kalvapalle Fri, 01/19/2024 - 12:44

Cutline

A Falcon 9 rocket lifts off from Vandenberg Space Force Base on Nov. 11, 2023, carrying a satellite designed and built by the ��߲ݴ�ý Aerospace Team (photo courtesy of SpaceX)

Safa Jinje

Topic

Electrical & Computer Engineering

Aerospace

Faculty of Applied Science & Engineering

Graduate Students

Mechanical & Industrial Engineering

Undergraduate Students

UTIAS

Subheadline

“We worked on this project for so long with such a narrow focus that actually seeing it deployed was very rewarding”

Students in the ��߲ݴ�ý’s Faculty of Applied Science & Engineering recently gathered in the basement of the Sandford Fleming Building – known to many as “The Pit” – to witness the deployment of HERON Mk. II into space.

The 3U CubeSat satellite, built and operated by the space systems division of the ��߲ݴ�ý Aerospace Team (UTAT), was launched into orbit on a Falcon 9 rocket on Nov. 11, 2023 as part of SpaceX’s Transporter-9 rideshare mission that lifted off from the Vandenberg Space Force Base near Lompoc, Calif.

The feat was entirely student funded with support from U of T Engineering through student levies and UTAT-led fundraising efforts.

“The experience of the launch was very surreal,” says master’s degree student Benjamin Nero, HERON’s current mission manger.

“We worked on this project for so long with such a narrow focus that actually seeing it deployed was very rewarding.”

“There are any number of things that could go wrong that might prevent a satellite from deploying,” adds Zachary Teper, a fellow master’s degree candidate who is part of the technical development team working on HERON’s ground station.

“So, watching each of the call outs coming out of the SpaceX mission control, seeing the rocket go up and meet every one of its mission objectives and then finally seeing our satellite get ejected out of the dispenser in the correct trajectory was a big relief – because we knew that it was finally in space and on the right path.”

Members of the UTAT space systems division gather on the sixth-floor roof of the Bahen Centre for Information Technology with the fully assembled ground station (photo by UTAT Space Systems)

Launching HERON – short for High frequency Educational Radio communications On a Nanosatellite – was the culmination of years of teamwork that brought together the efforts of more than 100 students.

HERON Mk. II, the second iteration of UTAT’s spacecraft, was originally designed and built between 2016 and 2018 for the fourth edition of the Canadian Satellite Design Challenge. Since space systems division was formed in 2014, many of the students who worked on the initial HERON design and build have since graduated. But the current operations team continued to develop the satellite and renew the student levy that allowed them to secure their space launch.

“The original objective for HERON was to conduct a biology experiment in space,” says Nero, who joined the team in 2019 during his second year of undergraduate studies. “But because of delays in the licensing process, we were unable to continue that mission objective. So, we re-scoped and shifted our focus to amateur radio communication and knowledge building.”

From left to right: HERON Mk. I (2016), HERON Mk. II Prototype (2018), HERON Mk. II Softstack (2020), HERON Mk. II Flight Model (2021) (photos by UTAT Space Systems)

Once the satellite’s final assembly was completed in 2021, the team began flight model testing and assembling a ground station, while also managing the logistics of the regulatory approvals needed to complete the launch.

“It’s difficult to put something in space, both technically and bureaucratically,” says Nero. “There are a lot of different governments that care about what you’re doing and want to know when and how you’re doing it.”

Getting to space was a significant milestone for the team, but it’s still only the beginning of their work.

“The goal for us as a design team is to start gathering institutional knowledge that we didn’t have before,” says Reid Sox-Harris, an undergraduate student who is HERON’s ground station manager and the electrical lead for UTAT’s next space mission, FINCH (Field Imaging Nanosatellite for Crop residue Hyperspectral mapping).

“We’ve never operated a satellite. So, we’re taking a lot of lessons learned with us through this process.” 

For example, when a satellite is deployed for the first time, the ground control team only has a rough idea of its movement and eventual location. They must simulate the launch to figure out exactly where it is before they can establish a connection. And when they receive new positional data, they must rerun their simulation.

“We have to take into account effects such as air resistance, or the sun’s solar cycles and the gravitational effects of the sun, the moon and the Earth – it’s a fairly complicated simulation,” Sox-Harris says.

Nero adds: “Part of the difficulty with a simulation is that a model is only useful for a certain period. An old estimate could result in as much as a few kilometres of drift from the satellite’s actual position per day.”

HERON’s ground station on the roof of the Bahen Centre (photo by UTAT Space Systems)

The team was not only tasked with designing a ground station capable of communicating with a satellite more than 500 kilometres away, but one that can survive a frigid and snowy Canadian winter.

“For any project, the most important thing you should be doing is testing,” says second-year student Swarnava Ghosh, who primarily works on the ground station software. “One challenge with our ground station currently is that there are too many variables that are not fully tested – and everything needs to be perfect in the chain for the communication to work. If the ground station is not pointing in the right direction, we won’t get a signal and we won’t establish communication. And if the amplifier is not working, then we won’t establish communication.” 

The team is confident that they will ultimately resolve any outstanding issues and establish communications with HERON. More importantly, they will be able to take what they’ve learned and apply it to the next mission.

“With FINCH, we want to make sure the ground station software and satellite can communicate on the ground,” says Sox-Harris. “Right now, there are over 500 kilometres between the satellite and ground station, so we can’t fly up there and test whether a command has worked.”

FINCH is set to launch in late 2025 on a rideshare rocket flight. Its current mission objective is to generate hyperspectral imaging maps of crop residue on farm fields in Manitoba from a low-Earth orbit.

There are many technical developments that are new to FINCH that weren’t applicable to HERON, the team says, including a novel optic system for remote sensing that is being developed by students.

“The risks associated with FINCH are mitigated by the work that is being performed by HERON right now. We’re learning many lessons that will be directly applicable to our next mission, and we’ll continue to learn from HERON for at least another year or more,” says Sox-Harris.

“This means the FINCH mission can be more complicated, it can move faster and ultimately we can have better reliability, which is something that we always strive for in aerospace.”

U of T astronomers discover first population of binary stripped stars

rahul.kalvapalle — Wed, 20 Dec 2023 15:22:31 +0000

U of T astronomers discover first population of binary stripped stars

rahul.kalvapalle Wed, 12/20/2023 - 10:22

Cutline

Artist's impression of a massive star stripping the hydrogen envelope of its companion star in a binary system (illustration by Navid Marvi, courtesy of the Carnegie Institution for Science)

Michael Pereira

Topic

Breaking Research

Astronomy & Astrophysics

Research and Innovation

Subheadline

New findings confirm the existence of hot helium stars long thought to be at the heart of hydrogen-poor supernovae and neutron star mergers

Astronomers at the ��߲ݴ�ý have discovered a population of massive stars that have been stripped of their outer hydrogen layer by companion stars.

For over a decade, scientists have theorized that approximately one in three massive stars are stripped of their hydrogen envelope in binary systems (systems where two stars are gravitationally bound to one another). Yet, until now, only one possible candidate had been identified.

The findings, published in Science, shed light on the hot helium stars that are believed to be the origins of hydrogen-poor core-collapse supernovae and neutron star mergers.

“If it turned out that these stars are rare, then our whole theoretical framework for all these different phenomena is wrong, with implications for supernovae, gravitational waves and the light from distant galaxies,” said Maria Drout, assistant professor in the David A. Dunlap department of Astronomy & Astrophysics at the ��߲ݴ�ý and an associate at the Dunlap Institute for Astronomy & Astrophysics.

“This finding shows these stars really do exist.”

It also opens up possibilities for more detailed research going forward. “For example, predictions for how many neutron star mergers we should see are dependent on the properties of these stars, such as how much material comes off of them in stellar winds," Drout says. "Now, for the first time, we’ll be able to measure that, whereas people have been extrapolating it before."

Assistant Professor Maria Drout with the Magellan Telescope at Las Campanas Observatory (photo by Tom Holoien/Maria Drout)

Drout and her colleagues propose that these newly discovered stars will eventually explode as hydrogen-poor supernovae. These star systems are also thought to be necessary to form neutron star mergers.

In fact, the researchers believe that a few objects in their current sample are stripped stars with neutron star or blackhole companions. These objects are at the stage immediately before they become double-neutron-star or neutron-star-plus-blackhole systems that could eventually merge.

“Many stars are part of a cosmic dance with a partner, orbiting each other in a binary system. They’re not solitary giants but part of dynamic duos, interacting and influencing each other throughout their lifetimes,” says Bethany Ludwig, a PhD student in the David A. Dunlap department of Astronomy & Astrophysics and third author on the paper. “Our work sheds light on these fascinating relationships, revealing a universe that is far more interconnected and active than we previously imagined.

“Just as humans are social beings, stars too, especially the massive ones, are rarely alone.”

(Left to right): Bethany Ludwig, Anna O’Grady, Maria Drout and Ylva Götberg (all authors on the paper) at the Magellan Telescopes at Las Campanas Observatory in Chile (photo by Ylva Götberg)

As stars evolve and expand to become red giants, the hydrogen at the outer edges of one can be stripped by the gravitational pull of its companion star – leaving a very hot helium core exposed. The process can take tens of thousands or even hundreds of thousands of years.

Stripped stars are difficult to find because much of the light they emit is outside of the visible light spectrum and can be obstructed by dust in the universe or outshone by their companion stars.

Drout and her collaborators began their search in 2016. Having studied hydrogen-poor supernovae during her PhD, Drout set out to find the stripped stars thought to be at the heart of these supernovae during a NASA Hubble postdoctoral fellowship at the Observatories of the Carnegie Institution for Science.

The researchers, who include co-author Ylva Götberg, assistant professor at the Institute of Science and Technology Austria, later designed a survey to look in the ultraviolet part of the spectrum where extremely hot stars emit most of their light. Using data from the Swift Ultra-Violet/Optical Telescope, they collected brightness data for millions of stars in the Large and Small Magellanic Clouds, two of the closest galaxies to Earth.

Ludwig, who developed the first wide-field UV catalogue of the Magellanic Clouds, used UV photometry to detect systems with unusual UV emissions – signaling the possible presence of a stripped star.

The researchers used this ultraviolet dataset of the Large and Small Magellanic Clouds, the two closest major galaxies to our own, to identify the candidate systems (image by NASA/Swift/S. Immler (Goddard) and M. Siegel (Penn State)

The team carried out a pilot study of 25 objects, obtaining optical spectroscopy with the Magellan Telescopes at Las Campanas Observatory between 2018 and 2022, and demonstrated that the stars were hot, small, hydrogen-poor, and in binary systems – all consistent with their model predictions.

Currently, the researchers are continuing to study the stars identified in the paper and expanding their search to find more. They will be looking both within our own Milky Way and nearby galaxies with approved programs on the Hubble Space Telescope, the Chandra X-ray Telescope, the Magellan Telescopes and the Anglo-Australian Telescope.

As part of this publication, all theoretical models and data used to identify these stars have been made public and available to other scientists.

Collaborating institutions include the ��߲ݴ�ý, the Observatories of the Carnegie Institution for Science, Max-Planck-Institut für Astrophysik, Anton Pannekoek Institute for Astronomy, Dunlap Institute for Astronomy & Astrophysics and Steward Observatory.

Astrophysicist Laurie Rousseau-Nepton discusses Indigenous contributions to her field on CTV's The Social

Christopher.Sorensen — Thu, 02 Nov 2023 16:01:42 +0000

Astrophysicist Laurie Rousseau-Nepton discusses Indigenous contributions to her field on CTV's The Social

Christopher.Sorensen Thu, 11/02/2023 - 12:01

Cutline

(supplied image)

Topic

Indigenous