Test 1 Flashcards

Question

How atmosphere interferes with telescopes

Answer 1

Atmosphere refracts starlight in random directions very quickly - stars "twinkle" On the mountain top, there is less distortion

Answer 2

Detect radio waves, not visual light Longer wavelength; bigger "dish" for the same resolution Radio waves are millions of times longer than optical wave Intrinsic resolution is much lower Can be combined to give a much bigger "radius" without extending the collecting area

Answer 3

``` Made a catalog of stars Name, brightness, position Distance to the moon and sun Trigonometry May have ranked the stars on a scale of 1 to 6 ```

Answer 4

bigger, brighter star

Answer 5

Smaller and dimmer

Answer 6

How it appears to us but not necessarily the way it is

Answer 7

zero magnitude negative magnitudes A -1 magnitude star is 100 times bright than a 4th magnitude star

Answer 8

Sun -26.74 | Sirius, magnitude -1.46

Answer 9

Venus, -4.92 to -2.98

Answer 10

decrease brightness x100 | or by 5 magnitudes

Answer 11

Measure stellar positions

Answer 12

Measures stellar positions | Remember: where are you my gaia

Answer 13

Not all stars have constant brightness, stars with periodic changes in brightness are called variable stars Henrietta Swan Leavitt

Answer 14

Any instrument that spreads the light out into a spectrum. e.g. a prism, CD, grating Remember spectro spectrum

Answer 15

1. A solid, liquid, or dense gas excited to emit light will radiate at all wavelengths and thus produce a continuous spectrum. 2. A low-density gas excited to emit light will do so at specific wavelengths and thus produce an emission spectrum. 3. If light comprising a continuous spectrum passes through a cool, low-density gas, the result is an absorption spectrum.

Answer 16

A featureless blackbody would look hotter or colder. - Spectral lines are not evenly spaced - A fingerprint that we can match to their original wavelength - Spectrum of a star (or galaxy) gives its speed "in the line of sight

Answer 17

- Powered by a central star at the end of its life (white dwarf) - Outer layers lost, and then "lit up" - Seeing emission lines from gas; explains the distinct colors

Answer 18

Contain bright young stars Diffuse gas Molecular clouds Distinct colors in photographs

Answer 19

Associated with historic accounts of stellar explosions | Can because by accretion on white dwarf

Answer 20

Either their birth or death Can see stars within them, sometimes behind them Not stars, but clearly related to stars

Answer 21

Harlow Shapley: Nebulae are "local" Heber D. Curtis: Nebulae are galaxies The Great Debate would see the two scientists argue the scale of the Universe and whether ‘spiral nebulae’ (what we now know as spiral galaxies) were small and nearby, or huge and far away. The participants were Heber D. Curtis, then of Lick Observatory, and Harlow Shapley of Mount Wilson Solar Observatory. In brief, the controversy concerned the scale and makeup of the universe. Shapley argued that the universe was comprised of a single galaxy, while Curtis held that it contained many galaxies. In holding these positions, each came to different conclusions regarding the celestial objects astronomers at the time called “spiral nebulae,” the nature of which was still unclear in 1920. Curtis thought that the spiral nebulae were galaxies external to our own, while Shapley disagreed, holding instead that they were clusters made up mostly of gas. On this point, Curtis turned out to be correct, as subsequent data bore out. But Shapley was correct in arguing that our galaxy was larger than previously thought, and for showing that our Sun was not at the center of its galaxy.

Answer 22

Temporary stars Commonly observed in Milky Way No supernova in Mikly way observed since the 1600s Gas accreting in a thin layer on a white dwarf Burns via normal nuclear fusion

Answer 23

Cepheids are bright and rare, stars that brighten and dim periodically - Have to calibrate the distance scale - Have parallax The key step in the cosmic distance ladder

Answer 24

the wavelength of the light is stretched, so the light is seen as 'shifted' towards the red part of the spectrum. - The greater the speed the greater the shift

Answer 25

type of supernova that occurs in binary systems (two stars orbiting one another) in which one of the stars is a white dwarf. The other star can be anything from a giant star to an even smaller white dwarf. Beyond this "critical mass", they reignite and in some cases trigger a supernova explosion.

Answer 26

Hubble's law, also known as the Hubble–Lemaître law, is the observation in physical cosmology that galaxies are moving away from the Earth at speeds proportional to their distance. In other words, the farther they are the faster they are moving away from Earth. Data from Cepheid variables and other astrophysical sources calculated the Hubble constant to be 50,400 mph per million light-years (73.4 km/s/Mpc) in 2016 The fact that the Hubble expansion rate of the Universe changes over time teaches us that the expanding Universe isn't a constant phenomenon. ... But the "Hubble constant" itself is a misnomer. It has a value today that's the same everywhere in the Universe, making it a constant in space, but it's not a constant in time.

Answer 27

Not diluted by expansion Whereas the density of regular matter is decreased Eventually, dark energy becomes the more dominant component Drives accelerated expansion Associated with negative pressure

Answer 28

It Will eventually become constant Changing slowly When our universe is 10x its age will be 83% of today's value

Answer 29

Hubble's constant is always decreasing If it decreases slowly enough distant objects appear to accelerate Cosmological constant: Hubble's constant approached a fixed value over the next billions of trillions of years.

Answer 30

The exception to general relativity Density increases as it expands The universe ends with a "big rip" Only possibility

Answer 31

Hubble's constant is 0 when the universe "turns around" | Negative during the contracting phase

Answer 32

Three classical tests: - Perihelion precession of mercury - time dilation - bending of starlight Also: - Binary neutron stars, "solar system tests", "frame dragging, black hole physics, and gravitational waves

Answer 33

Precession—the change in orientation of the Earth's rotational axis—alters the orientation of the Earth with respect to perihelion and aphelion. If a hemisphere is pointed towards the sun at perihelion, that hemisphere will be pointing away at aphelion, and the difference in seasons will be more extreme

Answer 34

Special relativity: moving clocks tick more slowly | General relativity: a clock in strong gravitational field ticks more slowly than a clock in a weak one

Answer 35

Jacobus Kapteyn Through: Parallax: find the distances of nearby bright stars Proper motion: stars appear to move relative to other stars

Answer 36

Harlow Shapley: - obtained distances from RR Lyrae variables - Gets distance wrong but shape right

Answer 37

100,000 light years

Answer 38

- Gas and dust concentrated in the disk | - Consists of 10^11 - 10^12 stars

Answer 39

Karl Jansky in the 1930s

Answer 40

Moving (accelerated) charged particles

Test 1 Flashcards

(68 cards)