Why Neil deGrasse Tyson and Emily Rice Think You Should Pay Attention to Low-Mass Stars
StarTalk・48 minutes read
Big stars have shorter lifetimes, while small stars have longer lifetimes. Low mass stars like brown dwarfs can last for trillions of years.
Insights
- Big stars have shorter lifetimes, while small stars like brown dwarfs can last for trillions of years, with their mass defining their classification between planets and stars.
- The magnetic field generation in brown dwarfs is not fully understood, with the belief that they become fully convective at some point, leading to varying magnetic fields across different types, showcasing differences from stars like the Sun in structure and energy transport.
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Recent questions
What are brown dwarfs?
Brown dwarfs are objects between planets and stars, not reflecting light like planets or shining brightly like stars. They were theorized in the 1960s and discovered in the 1990s. Brown dwarfs have a mass below 13 Jupiter masses, preventing fusion like stars but sharing similarities with massive exoplanets.
How do low mass stars differ from high mass stars?
Low mass stars, like brown dwarfs, have longer lifespans compared to higher mass stars. They can last for trillions of years due to their lower mass preventing fusion. This difference in lifetimes is a key distinction between low and high mass stars in the universe.
What is the relationship between mass composition and magnetic field strength in brown dwarfs?
Brown dwarfs have magnetic fields, but the exact mechanism behind their generation is not fully understood. It is believed that brown dwarfs become fully convective at some point, leading to the creation of a magnetic field. The variation in magnetic field strength across different types of brown dwarfs adds complexity to this relationship.
How do brown dwarfs impact galactic archaeology?
Galactic archaeology involves studying low mass stars with low metallicity to understand their age and formation history. Brown dwarfs, being low mass stars, play a crucial role in this field of study. By examining brown dwarfs, researchers can gain insights into the early stages of star formation and the evolution of galaxies.
What are the advantages of planets around brown dwarfs for finding Earth-sized planets?
Planets around brown dwarfs or low mass stars offer advantages for finding Earth-sized planets due to indirect methods and proximity to the star. The TRAPPIST-1 system, with seven Earth-sized planets, is a significant discovery around a small star, providing potential habitable zones for further exploration and understanding of exoplanets. This proximity allows for detailed observations and potential habitability studies of these planets.
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Summary
00:00
"Star lifetimes, brown dwarfs, and spectral types"
- Big stars have shorter lifetimes, while small stars have longer lifetimes.
- Low mass stars can last for trillions of years.
- Star Talk Cosmic Queries Edition with Chuck Nice and Emily Rice.
- Emily Rice is involved in a cosmic-themed fashion line called Star Torist.
- The term "brown dwarfs" was coined by Jill Tarter in 1975.
- Brown dwarfs are objects between planets and stars, not reflecting light like planets or shining brightly like stars.
- Brown dwarfs were theorized in the 1960s and discovered in the 1990s.
- The spectral classification system for stars includes letters like OBAFGKM, rearranged by temperature.
- Brown dwarfs introduced new spectral types L, T, and Y.
- Emily Rice is part of a group called Beauty and NYC, focusing on women-led research in astrophysics.
14:28
"Brown Dwarfs: Mass, Fusion, and Evolution"
- Brown dwarfs are defined by their mass, with a demarcation at 13 Jupiter masses separating them from planets and stars.
- Fusion occurs in objects above 13 Jupiter masses, involving hydrogen, lithium, and deuterium.
- Objects below 13 Jupiter masses do not undergo fusion, but this distinction does not significantly impact their structure or evolution.
- Brown dwarfs share similarities with massive exoplanets, making them easier to detect than Earth-like exoplanets.
- Conferences now focus on both brown dwarfs and exoplanets, fostering collaborations and knowledge exchange.
- Low-density stars plateau in size due to core physics, leading to decreasing density as mass decreases.
- The formation of low-density stars remains a mystery, with uncertainties surrounding their abundance and formation processes.
- Stars stabilize after formation, maintaining mass, temperature, and luminosity for extended periods.
- Brown dwarfs gradually cool and fade over time, leading to challenges in determining their age and mass.
- Ambiguities like the age-mass degeneracy and degeneracy pressure complicate the accurate measurement of high-mass objects like brown dwarfs.
28:14
Magnetic Fields in Brown Dwarfs
- Caleb from Wit People asks about the relationship between mass composition and magnetic field strength in brown dwarfs.
- Brown dwarfs have magnetic fields, but the generation of these fields is not fully understood.
- Brown dwarfs are believed to become fully convective at some point, leading to the creation of a magnetic field.
- The magnetic fields in brown dwarfs are thought to vary across different types.
- The term "Dynamo" is used as a broader term for generating magnetic fields.
- The difference in magnetic field generation between brown dwarfs and stars lies in the structure and energy transport within them.
- Stars like the Sun have clearer mechanisms for magnetic field generation compared to brown dwarfs.
- Collisions between brown dwarfs could potentially lead to hydrogen fusion and the creation of a new star.
- Low mass stars, like brown dwarfs, have longer lifespans compared to higher mass stars like the Sun.
- Galactic archaeology involves studying low mass stars with low metallicity to understand their age and formation history.
42:34
Advancements in Space Telescope Technology and Exoplanets
- Matt Curtis and Chuck discuss the advancements in Space Telescope technology and the direct imaging of exoplanets, mentioning the challenges and improvements needed for clearer images.
- They highlight two directly imaged exoplanets, one around the star Fomalhaut and the other in the HR 8799 system, emphasizing the limited resolution of the images but the ability to observe planet orbits.
- The HR 8799 system, with planets larger than Jupiter, showcases the potential for detailed observations and animations of planet movements around a star.
- Paula from Slovakia asks about the habitability of planets around brown dwarfs or low mass stars, with Matt explaining the advantages of these stars for finding Earth-sized planets due to indirect methods and proximity to the star.
- The TRAPPIST-1 system, with seven Earth-sized planets, is discussed as a significant discovery around a small star, offering potential habitable zones for further exploration and understanding of exoplanets.
