Stellar Evolution, Supernovae, and High-Energy Phenomena

Twenty-four question-and-answer flashcards covering stellar evolution, white dwarfs, supernovae, pulsars, and gamma-ray bursts as presented in the lecture notes.

What does the Hubble image of NGC 3603 (Figure 23.1) reveal about the stellar life cycle?

It shows dusty gas clouds where stars are forming, a central cluster of hot young stars only a few million years old, and an aging star ejecting a ring of gas as it nears the end of its life.

How do mass and radius relate for white dwarfs according to Figure 23.2?

As a white dwarf’s mass increases, its radius becomes smaller—more-massive white dwarfs are actually more compact.

Which astrophysicist laid the theoretical groundwork for understanding stellar corpses such as white dwarfs and neutron stars?

Subrahmanyan Chandrasekhar (1910–1995).

After the Sun becomes a red giant again, what happens to its core and outer layers (Figure 23.4)?

The core collapses and heats up while the outer layers are lost, exposing a hot core that forms a planetary nebula and then cools into a white dwarf.

Roughly what fraction of the Sun’s mass is expected to be lost during its giant stages?

About 46–50 % of its mass.

What type of star is Sirius B and how does it compare to Sirius A in X-rays (Figure 23.5)?

Sirius B is a hot white dwarf; it appears brighter in X-rays than the larger but cooler main-sequence star Sirius A.

How far away is the Sirius star system and where does it rank in proximity to Earth?

Approximately 8.6 light-years away, making it the fifth-closest stellar system to Earth.

Just before collapse, the core of a massive star resembles what structure and what element dominates its center (Figure 23.6)?

An onion-like structure with an iron core surrounded by layered shells of lighter elements.

Relative to its host galaxy, how bright can a supernova appear at peak (Figure 23.7)?

It can be as bright as an entire galaxy, outshining all the galaxy’s stars combined.

What are two key facts about the Kepler supernova remnant (Figure 23.8)?

It is about 400 years old, spans roughly 14 light-years, and its shell is expanding at about 2,000 km/s while being rich in iron.

Supernova 2014J in M82 was classified as what kind of supernova, and what binary scenario is thought to trigger it (Figure 23.10)?

A type Ia supernova, likely triggered when a white dwarf in a binary system accreted enough mass from its companion to explode.

In which galaxy is SN 1987A located, and what distinctive feature does its remnant show (Figure 23.11)?

It lies in the Large Magellanic Cloud and exhibits bright inner and outer rings of expelled material.

What causes the increasing number of bright spots in the ring around SN 1987A over time (Figure 23.12)?

High-speed ejecta from the supernova colliding with dense clumps in the older ring, heating them and making them glow.

Why did the light curve of SN 1987A decline more slowly between days 40 and 500 (Figure 23.13)?

Energy was being supplied by the radioactive decay of newly formed elements such as nickel and cobalt.

What object sits at the center of the Crab Nebula and what speeds do its emitted particles reach (Figure 23.14)?

A rapidly rotating pulsar whose particles stream outward at roughly half the speed of light.

How does the ‘lighthouse’ model explain pulsar pulses (Figures 23.15–23.16)?

Radiation beams emerge from the magnetic poles of a neutron star; because the magnetic and rotation axes are misaligned, the beams sweep past Earth and create periodic pulses.

What record-setting features characterize the ‘speeding pulsar’ shown in Figure 23.17?

It leaves a 37-light-year-long jet trail and is travelling 2.5–5 million mph away from its supernova remnant.

In a close binary, what ultimately drives a white dwarf to explode as a type Ia supernova (Figure 23.18)?

Accreting matter from its companion until it exceeds the Chandrasekhar limit and undergoes runaway thermonuclear burning.

What did the Compton Gamma-Ray Observatory reveal about the sky distribution of gamma-ray bursts (Figure 23.19)?

GRBs are distributed isotropically—uniformly in all directions—with no concentration along the plane of the Milky Way.

What did Hubble images of the 1997 GRB afterglow show about its host galaxy (Figure 23.20)?

The GRB was offset from the center of its host galaxy, indicating the burst occurred away from the galactic nucleus.

Which burst’s exceptionally bright afterglow in both X-ray and visible light was recorded by Swift in March 2008 (Figure 23.22)?

GRB 080319B.

What is the leading model for long-duration gamma-ray bursts as illustrated in Figure 23.23?

Core collapse of a massive star into a black hole that ejects narrow, relativistic jets producing the observed burst if one jet is aimed toward Earth.

What unique capability allows the Swift spacecraft to study GRBs effectively (Figure 23.24)?

On-board gamma, X-ray, and UV detectors coupled with the ability to rapidly reorient itself to any newly detected burst, enabling prompt multi-wavelength observations.

What is the approximate value of the Chandrasekhar limit that a white dwarf cannot exceed without collapsing?

About 1.4 times the mass of the Sun.