Astrophysics Flashcards

Question

M stars

Answer 1

Colour: red Temperature: \<3500K size: half the size of sun Spectra: Neutral atoms, titanium oxide Example: Antares + Betelgeuse

Answer 2

- stars are formed in a Nebula - A Nebula is a very large cloud of gas and dust in space

Answer 3

- Gravity makes dense region of gas more compact - soon take on definite shape and are called proto stars - Once the core of the protostar reaches a certain temperature, nunclear fusion begins and the protostar ignites to become a star - A star is a ball of plasma undergoing nuclear fusion and gives off large amounts of energy in the form of electromagnetic radiation - As long as there is a nuclear reaction taking place, the internal forces will balance the external forces

Answer 4

- A star in which hydrogen burning takes place - This thermonuclear fusion of hydrogen nuclei into helium nuclei

Answer 5

Gravitational forces that thend to collapse a star increase with mass So for the star to be in equilibirum, it means the outward pressure from the core must be larger Therefore, the nuclear reactions must run at a higher rate generating more power, which leads to the star having a higher luminosity

Answer 6

When the hydrogen in a main sequence star is consumed, fusion stops and the forces suddenly become unbalanced Mass and gravity cause the remaining gas to collapse on the core The collapsing outer-layers cause the core to heat up and the fusion of helium into carbon begins The forces regain balance and the outer shell expands rapidly A planetary nebula is created when this Red Giant blows off its outer layers after it has run out of carbon to burn. These outer layers of gas expand into space, forming a nebula which is often the shape of a ring or bubble.

Answer 7

If the mass of a star is 3 times that of our sun or greater, than the Red Giant will become a Red Supergiant When the massive Red Giant fuses all of the helium into carbon, fusion stops and the outer layers collapse on the core

Answer 8

The Core of the supergiant will then collapse in less than a second, combine protons and electrons into neutrons (creating a neutron star core) Other matter rebounds off the core and fusion again starts in the outer star layers causing a massive explosion called a supernova In a supernova, a massive shockwave is produced that blows away the outer galaxies of the star

Answer 9

Planetary Nebula breaks down to its core A white dwarf is very hot when it forms, but because it has no source of energy, it will gradually cool as it radiates its energy. This means that its radiation, which initially has a high color temperature, will lessen and redden with time. As it cools, the light it gives off will fade and form a Black Dwarf

Answer 10

Under the intense gravitational forces in a Supernova, the core collapses under the pull of gravity The core rises to temperatures as high as 100 billion Kelvin In such high temperatures and pressures, proyons and electrons can combine, in a reverse beta decay, to form neutrons and neutrinos In this way the centre of the core turns into a ball of neutrons wich will become a neutron star

Answer 11

If the mass of the surviving star is greater than 3 solar masses than a black hole forms A black hole is a core so dense and massive that it wil generate so much gravity not even light can escape it

Answer 12

Variation in Doppler shift Planetary transits Direct imaging

Answer 13

A giant planet and a star orbit around a common centre of gravity There will be times when the star will be moving towards the Earth, and times when the star will be moving away from the earth So there will be small changes to the spectrum of the star, which will be seen as small redshift and small blueshift

Answer 14

If an exoplanet crosses in front of a star's surface, then the brightness we see will drop by a small amount Therefore a light intensity vs time graph would show a suddent drop in intensity It allows rough estimations to be made of the planet's radius and thus mass

Answer 15

Light from the star has been digitally removed to enhance view of planets

Answer 16

Can observe visible, ultra-violet and infared rays

Answer 17

Used to observe high energy objects such as neutron stars and supernovae

Answer 18

Infared telescope in orbit around the sun at the same distance as the earth but a long way away - originally cooled by liquid helium

Answer 19

hi/ho | (Height of image/height of object)

Answer 20

A class of objects whose distances can be computed by comparing their observed brightness with their known luminosity.

Answer 21

Emmitters and absorbers of radiation

Answer 22

When yo heat something up from absolute zero it will give off shorter wavelengths as the temperature increases

Answer 23

- In the early universe protons and neutrons produced - protons are stable and neutrons decay into protons - Neutrons combine with protons to form Helium and Deutrium - These are stable, so no further decay occurs - Hence by comparing the number of free protons to the number of helium atoms we can test models for the formation of the universe - Big Bang fits this very well - the universe is made up of H and He

Answer 24

- Cosmic Microwave Background Radiation - Red shifted background radiation left behind after the big bang - radiation stretched that it is observed in the microwave region - hence cosmic microwave background radiation

Answer 25

- larger resolving power - resolving power proportional to D - Power is proportional D^2, more power detected by larger diameter telescope

Answer 26

A massive and extremely remote celestial object, emitting exceptionally large amounts of energy They are distant objects powered by black holes a billion times as massive as our sun.

Answer 27

parsec : distance to an object subtending 1 sec of arc to Earth’s orbit To prove a parsec convert it into radians then covert it into light years

Answer 28

Gives the ratio of the (recessional) velocity (of galaxies) to distance from Earth

Answer 29

increase in wavelength (of em radiation) due to relative recessive velocity between observer and source

Answer 30

Angle subtented by image at eye/ angle subtended by object at unaided eye

Answer 31

situated on the ground as it detects radio waves which are not absorbed by the atmosphere Large mirrors so collecting power very high

Answer 32

Careful consideration required for the position of an ultraviolet telescope because the majority of ultraviolet is absorbed by the atmosphere Better resolving power than radio wave telescope as ultraviolet has a shorter wavlength than radio waves

Answer 33

X-ray telescopes are usually situated in space because the atmophere prevents the majority of X-radiation reaching the Earth's surface. X rays are very penetrating and not easily reflected off metal surfaces

Answer 34

A bright star whose intensity caries over a matter of days. The period of the variation of intensity is linked directly to the absolute magnitude of the star

Answer 35

The image formed on the CCD is created by incident photons. These photons cause electrons to be released.  The electrons are trapped in (“potential wells” in the CCD)  The number of electrons liberated (in each pixel) is proportional to the intensity of the light/number of photons falling (on each pixel). or so that the pattern of the charge built up is related to the image.

Answer 36

Two objects will just be resolved when the first minimum/edg of the airy disc in the diffraction pattern of one image  Coincides with central maximum/centre of the airy disc of the other.

Answer 37

10-400 days

Answer 38

100-2500 nm

Answer 39

+15 to -10

Answer 40

Measurements of supernovae do not agree with predictions (from Hubble’s Law)  So Universe must be expanding at increasing rate/accelerating  (Controversial as) no known energy source for expansion or reference to dark energy