AST 104 JEFFERY IAL EXAM 3 (FINAL EXAM!!)

Black holes:

EXIST

"Let's play Jeopardy! For $100, the answer is: The theoretical defining characteristic of a black hole is this surface from which and from below which light cannot escape. The multitudinous massive compact objects that we have observed since the 1970s and call black holes are black holes by convention. Whether the conventional black holes or some fraction of them have the theoretical defining characteristic is not yet known."

event horizon

"Let's play Jeopardy! For $100, the answer is: He/she is the discoverer of the analytically exact solution for the general relativity in massless-space outside of a non-rotating, chargeless, spherically symmetric mass distribution." Who is ___________ , Alex?

Karl Schwarzschild (1873-1916)

The radius of the event horizon of a Schwarschild black hole is the radius.

Schwarzschild

The Schwarzschild and Kerr solutions of general relativity predict a region of infinite density: in the Schwarzschild solution this region is a point and in the Kerr solution it is an infinitely thin ring. This region is called the:

singularity

The formula for the Schwarzschild radius is RSch = 2GM c 2 = 2.9532 M M⊙ km , where G = 6.67384 × 10−11 (in MKS units) is the gravitational constant, M is the mass of an object, c is the speed of light, and M⊙ = 1.9885 × 1030 kg is the mass of the Sun. This formula follows from general relativity for a non-rotating, spherically symmetric mass distribution, but it also accidently can be obtained by setting the escape velocity equal to the speed of light in the Newtonian formula for the escape velocity from a spherically symmetric mass distribution. According to general relativity if any object is compressed within its Schwarzschild radius it:

must become a black hole.

Compact X-ray sources in binary systems where the source seems to have MORE than 3 M⊙ are:

black hole candidates.

Probably because of complex magnetic and electric field effects about rotating black hole candidates, these candidates exhibit:

jets of glowing gas.

These black hole candidates are found in the centers of large galaxies. They have masses of order 106 M⊙ to 109 M⊙. The name given to the kind of black holes these objects may be is:

supermassive black hole

It is believed that black holes can lose rest mass energy and thus mass by:

HAWKING radiation

If the Sun instantaneously and without any other catastrophic effects collapsed to being a black hole, what would happen to the Earth?

The Earth's orbit would be unaffected, but the Earth's surface temperature would soon fall too low to sustain life.

The more massive the star is, the faster it evolves in general. But black hole candidates in binary systems (which are presumably the compact remnants of ordinary stars) are sometimes less massive than their ordinary star companions. Resolve this paradox.

The black hole candidate progenitor was more massive than the companion, but lost significant mass in late stellar evolution and even more mass in the supernova explosion that is believed to have preceded the formation of the candidate.

"Let's play Jeopardy! For $100, the answer is: They are large, gravitationally-bound systems of stars that range from dwarf versions that are kiloparsec in size scale to the large ones that are tens of kiloparsecs or even a couple hundred kiloparsecs in size scale."

galaxies

Galaxies come in five main types: ellipticals, lenticular, unbarred spirals, barred spirals, and

irregulars.

"Let's play Jeopardy! For $100, the answer is: In the celestial-sphere picture of the sky, this object is luminous band on celestial sphere that straddles a great circle that is at an angle of about 60◦ to the celestial equator."

Milky Way

The center of the Milky Way is in:

Sagittarius.

The first three persons to speculate about the structure of the Milky Way in context of Newtonian physics in the 18th century seem to have been:

Thomas Wright, Immanuel Kant, and J. H. Lambert.

"Let's play Jeopardy! For $100, the answer is: He/she attempted to map the Milky Way using star counts (or star gauges)."

William Herschel (1738-1822)

"Let's play Jeopardy! For $100, the answer is: He/she obtained a roughly correct size estimate for the Milky Way and was the first to roughly correctly locate the center of the Milky Way using Cepheid variable stars in globular clusters in the halo of the Milky Way."

Harlow Shapley (1885-1972)

Clouds in space or, historically, those objects regarded as cloud-like are called:

nebulae

The spiral nature of some nebulae was discovered using visual astronomy and the largest telescope of its time: the 183-cm diameter Leviathan of Parsontown located at Birr Castle, Parsontown, Ireland. Because the spiral nebula are rather faint, it takes are large telescope to make out the spiral arms visually. With long-exposure photography it is relatively easy to discover spirals. But visual astronomy beat the recently invented photography by some years in this case: the discovery was made in 1845 April by the builder of the Leviathan:

the Earl of Rosse (1800-1867)

On 1920 April 26, a debate about the nature of the spiral nebulae was held at a meeting of the National Academy of Sciences in Washington, D.C. The debaters both made sound points in the printed presentations that they later made if not on the day of. This debate is called the Great Debate or the:

Shapley-Curtis debate

Using Cepheid variable stars as distance indicators and the inverse square law for electromagnetic radiation flux, this famous astronomer was able to prove that M31 (the Andromeda spiral nebulae) was a giant star system (i.e., a galaxy) outside of the Milky Way. His/her name is:

Edwin Hubble (1889-1953)

Edwin Hubble (1889-1953) was able to prove the extragalactic nature of the spiral nebulae because, among other things, he had available the world's:

largest telescope of his day

A characteristic nearest neighbor distance between galaxies is of order:

1 Mpc

In the Hubble sequence of galaxies, the main types are:

elliptical, lenticular, unbarred spiral, barred spiral, and irregular

"Let's play Jeopardy! For $100, the answer is: They are the subtypes of the Hubble type barred spiral." What are ___________ , Alex?

SBa, SBb, and SBc

"Let's play Jeopardy! For $100, the answer is: It's a common misconception that he/she originally theorized that galaxies evolved from ellipticals to unbarred spirals or barred spirals. In fact, he/she emphasized that his/her classification scheme was entirely empirical." Who is ___________ , Alex?

Edwin Hubble (1889-1953)

"Let's play Jeopardy! For $100, the answer is: Galaxies of this Hubble type range in size from about 105 M⊙ (small dwarfs) to 1013 M⊙ (large giants), consist mainly of Population II and old Population I stars, and have relatively little dust and gas." What is the type ___________, Alex?

elliptical

The 8 elliptical subtypes E0 through E7 do NOT give unambiguous information about the intrinsic properties of the ellipticals because they are assigned:

just on the basis of the shape of the galaxy projected on the sky

Lenticular (SO and SBO) galaxies have:

disks, but no well-defined spiral arms.

Spiral galaxies are divided into ordinary spirals (or just spirals without qualification) and

barred spirals.

Based on the appearance of their spiral arms, spiral galaxies are divided into grand-design spirals and:

flocculent spirals

To see a spiral or lenticular galaxy parallel to the disk is to see it _________ and to see it perpendicular to the disk is to see it _________.

edge-on; face-on

One can usually tell the subtype of a spiral or barred spiral seen EDGE-ON because a subtype indication is provided by:

the relative size of the bulge.

A well known example of an irregular galaxy (of subtype Irr I) is the:

Large Magellanic Cloud (LMC)

Grand-design and flocculent spiral arms are believed to be caused by, respectively, ___________ and ______________.

spiral density waves; self-propagating star formation plus differential rotation

The Andromeda galaxy (M31), the Large Magellanic Cloud (LMC), and the Small Magellanic Cloud (SMC) are all:

naked-eye objects: i.e., they can all be seen by the naked eye.

"Let's play Jeopardy! For $100, the answer is: These objects are themselves grouped into larger structures: clusters (poor and rich), superclusters, filaments, sheets and, in a zero or near-zero population sense, voids." What are ___________ , Alex?

galaxies

The Milky Way belongs to a poor irregular cluster called:

the Local Group.

The nearest rich cluster contains over 2000 galaxies, covers about 10◦×12◦ on the sky in the constellation Virgo, is about 15 Mpc away, and has a diameter of about 3 Mpc. It is an irregular cluster. It is called the:

Virgo cluster.

Superclusters for the most part do not seem to be gravitationally bound systems. If this is so, then their component clusters will:

progressively move apart with the expansion of the universe.

These structures, which are roughly spherical, are of order 30 Mpc to 120 Mpc in diameter. They are rather empty, but may contain hydrogen gas and strings of dim galaxies. They are called:

voids.

"Let's play Jeopardy! For $100, the answer is: The large-scale structure of galaxy groupings is often described by this adjective." What is ___________, Alex?

web-like

In formation of elliptical galaxies most of the star formation must have occurred and exhausted the gas before the gas could collapse to a disk OR a disk formed, but the disk and gas:

were eliminated by collisions and mergers in galaxy rich environments

The science of the universe as a whole is called:

cosmology.

The big bang is:

a theoretical origin of the universe or our pocket universe.

Given v as recession velocity and r as cosmological physical distance, Hubble's law is:

v = Hr.

"Let's play Jeopardy! For $100, the answer is: He/she is the person who observationally discovered Hubble's law." Who is ____________, Alex?

Edwin Hubble (1889-1953)

The Hubble length is 4.283h −1 70 Gpc (where h70 is the reduced Hubble constant: it is equal to 1 to within a few percent). It is a characteristic size scale for the:

observable universe.

The Einstein universe presented by Einstein in 1917 is a/an universe model.

static, hyperspherical

"Let's play Jeopardy! For $100, the answer is: These models were the among the first plausible universe models to predict the expansion of the universe."

Friedmann-Lemaˆıtre

"Let's play Jeopardy! For $100, the answer is: In the Friedmann-Lemaˆıtre models, it is the parameter that that specifies the geometry of the universe: if less than 1, the universe is hyperbolic and infinite; if equal to 1, the universe is flat and infinite; if greater than 1, the universe is hyperspherical and finite."

Ω (spelt Omega)

The curvature of space in Friedmann-Lemaˆıtre models is determined by the total density parameter (i.e., total Ω or Omega). This parameter is the ratio of total universal average mass-energy density to the critical mass-energy density. The curvature possibilities are:

hyperbolic (Ω < 1), flat (Ω = 1), and hyperspherical (Ω > 1).

According to observations of several kinds beginning in 1998, it seems that the universal expansion is currently:

accelerating.

The simplest explanation considered for the accelerating expansion of the universe is:

a cosmological constant dark energy.

After the dark energy (whatever that is) the most abundant form of energy in the universe is apparently some form of matter known only (at least to circa 2017) through its gravitational effects. We call this matter:

dark matter.

The Friedmann-Lemaˆıtre-Λ model (i.e., the Friedmann-Lemaˆıtre model with a non-zero cosmological constant Λ) with parameters adjusted to fit current observations (circa 2005) is called the Λ-CDM model or the:

concordance model.

In big bang nucleosynthesis, the major products are:

hydrogen and helium in about a 3:1 mass ratio.

Most of the heavy elements (those for carbon and up certainly) in the universe were formed in:

stars and supernovae

The relic primordial electromagnetic radiation field from the early universe is usually called the:

Cosmic Microwave Background (CMB)

Five observational evidences are:

big bang cosmology.

"Let's play Jeopardy! For $100, the answer is: It is name for the super-expansion that our pocket universe may have undergone at very early times. What is __________, Alex?

inflation