Chapter 13: The Universe & Its Stars

Key Ideas – Chapter 13 1.Technology has advanced our understanding of the universe 2.Nuclear fusion powers the stars & is the force behind solar flares, prominences, sunspots & solar wind 3.A star’s mass determines the stages of its life cycle 4.Galaxies, star clusters, & nebulas can be distinguished by their structures & characteristics

Figure 2, P. 414

Visible Light Spectrum 1.Red = Long Wavelength at 4.3 – 4.6 x Hz 2.Blue = Short Wavelength at 6.0 – 6.7 x Hz

Boat Moving Through Water & Making Waves Figure 3, P. 414 & Figure 4, P. 415

Red Shift/Blue Shift Star Light is ‘blue-shifted’

COBE DMR Image Figure 7, P. 417

COBE Image COBE image shows tiny variations in cosmic background radiation is a remnant of the Big Bang

Data From WMAP Figure 8, P. 417

WMAP Data from the Wilkinson Microwave Anisotropy Probe (WMAP) confirmed the age of the universe is 13.7 billion years Warmer (red) and colder (blue) colours represent different densities of matter in early universe

Parallax Figure 1, 2, & 3, P Baseline

Parallax In order to calculate how far away a star is, astronomers use a method called parallax. Because of the Earth's revolution about the sun, near stars seem to shift their position against the farther stars. This is called parallax shift. By observing the distance of the shift and knowing the diameter of the Earth's orbit, astronomers are able to calculate the parallax angle across the sky (using trigonometry)

Apparent/Absolute Magnitude 1.Different absolute magnitudes of Light 2.Same apparent magnitude of light 5 m 50 m

Nuclear Fusion Figure 1, P. 425

Nuclear Fusion: required for a star to be born 1.2 protons create deuterium 2.addition of a 3 rd proton creates helium helium-3 nuclei fuse to form helium and release  2 free protons along with  considerable energy

Birth of a Star: Balancing Nuclear Fusion & Gravity 1.Gravity pulls gas and dust inward toward the core. 2.Inside the core, temperature increases as gas atom collisions increase. 3.Gas pressure & temperature increases ignite nuclear fusion 4.Outward pressure from nuclear fusion RESISTS the collapse of the nebula When gas pressure = gravity, the protostar has reached equilibrium

Solar Anatomy

Sun Spots Sun Spots: dark areas large enough to swallow several Earths

Sun’s Surface Gases move to the sides of the granule and sink back into the Sun at the darker, cooler boundaries of the granule (see Fig. 4 P. 427) The dark spots are called Sun Spots

Solar Flares & Solar Wind Solar Flares: Brief explosions of large quantities of gas & charged particles produced by changing magnetic field lines around sun spots Solar Prominences: Ionized gases form looping structures along magnetic field lines lasting for weeks

Star Life and Death

NASA: HR Diagram Video Above: well known stars in the Milky Way galaxy

Local Group of Gallaxies

Extending out Light Years The Milky Way is the central player in a cast of additional smaller, irregular galaxies and other stellar clusters that remain within the M.W. halo. Here is a map of some of these objects:

Figure 3-6, P. 438

Classifying Galaxies: Hubble sequence Edwin Hubble Classified galaxies according to four basic shapes: 1.Elliptical Galaxies 2.Spiral Galaxies 3.Barred Galaxies 4.Irregular Galaxies

What is at the Centre of the Milky Way?

Sagittarius A* A supermassive black hole, Sagittarius A*, exists at the centre of the core Mass of black hole = Solar Masses Diameter of black hole = 15 times that of Sun

Globular ClusterOpen Cluster 1. Number of stars Thousands - millionsA few hundred 2. Age of stars All very oldYoung stars 3. Shape and size of cluster Spherical, light years in diameter Spread out, 30 light years in diameter 4. Location in Galaxy Near galactic centreOnly in the galactic disk

Dark Energy & the Expansion of the Universe Patricia Burchat: Shedding light on dark matter

1.The more shallow the curve, the faster the rate of expansion. 2.Curve changes noticeably about 7 billion years ago, when objects in the universe began flying apart at a faster rate. 3.Astronomers theorize that the faster expansion rate is due to a mysterious dark energy that is pulling galaxies apart. Image courtesy of NASA/STScI/Ann Field. Dark Energy and Dark Matter