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Emily Levesque Public Lecture: The Weirdest Stars in the Universe

Perimeter Institute for Theoretical Physics・61 minutes read

Dr. Emily Levesque will discuss peculiar stellar phenomena and their role in exploring the universe's history, evolution, and extremes. By studying titanium oxide absorption lines in red supergiants' spectra, researchers like Dr. Levesque were able to accurately measure their temperatures and correct their placement on the diagram.

Insights

Dr. Emily Levesque will discuss peculiar stellar phenomena, emphasizing their significance in studying the universe's history and evolution, using examples like Spica and Betelgeuse to illustrate the transition of stars over time.
Researchers like Dr. Levesque use titanium oxide absorption lines in red supergiants' spectra to accurately measure temperatures, correcting discrepancies in their placement on the Hertzsprung-Russell diagram.
The potential discovery of a Thorne-Zytkow object could revolutionize understanding of stable stellar interiors and element production, showcasing the ongoing advancements in stellar astronomy and the need for further observations to confirm significant findings.

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Recent questions

What is the Hertzsprung-Russell diagram?
A tool in astronomy to plot stars based on temperature and brightness.
How do researchers measure star temperatures accurately?
By analyzing titanium oxide absorption lines in red supergiants' spectra.
What is the significance of neutron stars in astronomy?
They are remnants of massive star cores, incredibly dense and small.
How are gamma-ray bursts detected in space?
Through observatories like the Swift spacecraft equipped with detectors.
What is the role of time domain astronomy in research?
To study fleeting events like gamma-ray bursts quickly.

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Summary

00:00

"Exploring Red Supergiants in Astronomy Lecture"

Perimeter Institute in Waterloo, Ontario, Canada hosts a public lecture series, with Greg Dick as the Director of Educational Outreach.
The lecture, lasting approximately one hour, will be followed by a Q&A session, with online viewers able to participate using the hashtag #PIlive.
Dr. Emily Levesque, an astronomy professor at the University of Washington, is the guest speaker, known for her research on massive stellar astrophysics.
Dr. Levesque will discuss peculiar stellar phenomena and their role in exploring the universe's history, evolution, and extremes.
The Hertzsprung-Russell diagram is used in astronomy to plot stars based on temperature and brightness, showcasing where normal stars typically appear.
Stars evolve over time, with massive stars like blue supergiants transitioning to yellow supergiants and eventually red supergiants.
Notable examples include Spica, a blue supergiant, and Betelgeuse, a red supergiant in the constellation Orion, known for its immense size.
Red supergiants exhibit unique features due to their size and temperature, such as convective cells on their surface, significantly larger than those on the Sun.
Red supergiants initially posed a challenge in stellar physics due to discrepancies in their placement on the Hertzsprung-Russell diagram, later resolved by analyzing their spectra.
By studying titanium oxide absorption lines in red supergiants' spectra, researchers like Dr. Levesque were able to accurately measure their temperatures and correct their placement on the diagram.

15:47

"Stellar Evolution: From Fusion to Black Holes"

An equation in astronomy relates a star's luminosity and temperature to its size, with L representing luminosity, pi and Sigma as constants, and temperature and radius as measured variables.
By solving for radius in the equation, researchers calculated the size of stars, leading to the discovery of the largest stars ever seen, including KY Sigma, which surpasses Jupiter's orbit and nears Saturn's size.
Stars progress through fusion processes, culminating in iron fusion, disrupting the delicate balance between gravity and fusion, leading to a core collapse supernova, an explosive end for massive stars.
Historical supernovae like the one in 1054, visible for two weeks, left behind the Crab Nebula, a supernova remnant, with modern supernovae being less dramatic, like the one in the Whirlpool Galaxy in 2005.
Supernova 2009 IP, initially thought to be a supernova, was actually a luminous blue variable, a star type that undergoes eruptions, showcasing variability and posing challenges in understanding their behavior.
Neutron stars, remnants of massive star cores, are supported by neutron degeneracy pressure, resisting gravitational collapse, incredibly dense and small, with some becoming pulsars emitting light from magnetic poles.
Pulsars were discovered by Jocelyn Bell Burnell in the 1960s, initially humorously nicknamed LGM 1-4, emitting regular signals resembling a heartbeat, later identified as neutron stars emitting detectable light.
Massive stars collapsing into black holes can produce gamma-ray bursts, with the core collapsing into a rapidly rotating black hole consuming the star and emitting high-energy jets, leading to a violent end similar to a supernova.
Vaillar satellites, launched to monitor nuclear tests, accidentally discovered gamma-ray bursts from space, showcasing the violent deaths of massive stars and the unique timescale of their demise.

31:10

Swift spacecraft detects gamma-ray bursts swiftly

Gamma-ray bursts are flashes from dying stars in other galaxies, prompting the use of dedicated telescopes like the Swift spacecraft.
The Swift spacecraft is equipped with gamma-ray, x-ray, ultraviolet, and optical detectors to observe and study gamma-ray bursts quickly.
Swift orbits Earth, detecting gamma-ray bursts and sending notifications to astronomers for immediate study.
Time domain astronomy focuses on studying fleeting events like gamma-ray bursts quickly.
In reality, astronomers receive notifications on their phones for gamma-ray bursts, triggering urgent observations with advanced telescopes like the Keck 10-meter telescopes.
Observations are dependent on clear nights for accurate data collection, with extensive efforts to eliminate background noise and ensure data accuracy.
Discoveries from observations are shared through scientific publications like the Astrophysical Journal and public repositories like the gamma-ray burst circulars Network.
Gravitational waves are ripples in space-time, detected by observatories like LIGO, which confirmed the collision of two neutron stars emitting gamma rays and light.
Time domain astronomy led to the rapid detection of gravitational waves and light from colliding neutron stars, showcasing the importance of quick and precise observations.
An amusing example involves the mistaken discovery of potassium flare stars due to matches being struck in a telescope room, highlighting the need for thorough investigation in scientific discoveries.

46:02

"Stellar Discoveries: Potassium Flares and Perytongs"

Potassium flare stars were initially debunked but later confirmed by another observer who noted excess potassium in a star's spectrum.
Parkes Observatory in Australia observed fast radio bursts, initially dubbed "Perytongs," which were later discovered to be caused by microwave interference.
Perytongs were found to cluster around lunchtime due to microwave use, causing brief radio emission flashes.
A Thorne-Zytkow object is formed by a red supergiant absorbing a neutron star, creating a unique chemical signature in its spectrum.
Detection of excess molybdenum, lithium, and rubidium in a star's spectrum indicated a potential Thorne-Zytkow object, a significant find in stellar astronomy.
Observations of the star with the unique spectrum fit the predictions of Thorne-Zytkow objects, but further observations are needed for confirmation.
The potential discovery of a Thorne-Zytkow object could revolutionize understanding of stable stellar interiors and element production in stars.
The speaker expressed excitement at the prospect of witnessing a galactic supernova in the Milky Way, highlighting the impact such an event would have on astronomy and public interest.
The audience was invited to ask questions, with one attendee inquiring about data sharing practices in gamma-ray burst research.
The speaker concluded the presentation by thanking the audience and offering to address any further questions, emphasizing the interactive nature of the session.

01:00:59

"Collaborative Scientists Study Gravitational Waves and Stars"

Scientists collaborate by sharing data and analysis, encouraging teamwork and information exchange.
Gravitational waves and light travel at the speed of light, with signals produced in a specific order.
Neutron stars disrupt the core of giant stars, affecting fusion processes and potentially causing them to run out of fuel.
Supernovae from star systems with massive stars can rival the moon's brightness, lasting for about a week or two.
Polaris, a yellow supergiant, will continue to exist for a while, but its evolutionary state and lifespan are uncertain due to difficulties in studying such rare stars.

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