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The Universe Flashcards

(59 cards)

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1
Q

How old is the Universe?

A

13.7 billion years old

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2
Q

How many galaxies are there?

A

Around a hundred billion

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3
Q

What will be left at the end of the Universe?

A

Photons

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4
Q

How many stars are in the Milky Way?

A

Around 300 billion

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5
Q

What are the dark patches in the night’s sky between us and other stars of the Milky Way?

A

Nebulae

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6
Q

What temperature are nebulae?

A

About 10 degrees centigrade above absolute zero

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7
Q

What is the nearest galaxy to us and how far away is it?

A

Andromeda; 2.5 million light years away

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8
Q

When will Andromeda collide with the Milky Way?

A

Around 3 billion years time

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9
Q

What is the closest star to our Sun and how far away is it?

A

Proxima Centauri (part of the 3 star system of Alpha Centauri, with Alpha Centuari A & B forming a binary pair; 4.22 light years away

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10
Q

What are all solar systems formed from?

A

Nebulae

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11
Q

Why did the early Solar System spin faster as matter coalesced?

A

To adhere to the Conservation of Angular Momentum. This same physical law also prevented the early Solar System from collapsing completely

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12
Q

What does the word ‘planet’ mean?

A

Wandering star

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13
Q

What are gas giants formed from?

A

Collections of ice and rock that become so massive that they attract hydrogen and helium gas left over from the formation of the Sun

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14
Q

As live stars are only able to form helium, where are the rest of the elements created?

A

In the core of red giants and in supernovae

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15
Q

What happens to stars that deplete their hydrogen supply?

A

Their cores contract and the outer layers expand, and they eventually explode, producing planetary nebulae or supernovae (depending on their mass) and then become white dwarfs, neutron stars or black holes (again, depending on their mass)

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16
Q

What kind of star is our Sun and what will it become?

A

It is a yellow dwarf and will become a red giant then a white dwarf then a black dwarf

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17
Q

Which kind of star is most prevelant in the Universe?

A

Red dwarfs

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18
Q

How long to red dwarfs live?

A

Trillions of years. They will be the last living stars in the Universe

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19
Q

What kind of star is Proxima Centauri?

A

Red dwarf

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20
Q

What is the brightest star in the night sky?

A

Sirius A

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21
Q

Why will the Sun become a red giant?

A

Over the life of a main sequence star, the outward pressure of fusion has balanced against the inward pressure of gravity. When the Sun runs out of hydrogen to fuse, the balance tips in the favor of gravity, and the star starts to collapse. But compacting a star causes it to heat up again and it is able fuse what little hydrogen remains in a shell wrapped around its core. This burning shell of hydrogen expands the outer layers of the star, and it becomes a red giant

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22
Q

How long will the Sun spend as a red giant?

A

1 billion years

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23
Q

How can a red giant produce elements other than helium?

A

When a star gets bigger, its heat spreads out, making its overall temperature cooler. But the core temperature of a red giant increases until it’s finally hot enough to fuse the helium created from hydrogen fusion. Eventually, it will transform the helium into carbon and other heavier elements

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24
Q

What happens when a red giant depletes its helium store?

Study These Flashcards
A

The star shrinks again until a new helium shell reaches the core. When the helium ignites, the outer layers of the star are blown off in huge clouds of gas and dust known as planetary nebulae. These shells are much larger and fainter than their parent stars

25
What is a supergiant?
A red ot bloe star of 10-70 solar masses that always explode as Type II supernovae at the end of their lives and form black holes
26
What is the lifespan of a supergiant?
30 million to just a few hundred thousand years
27
Where is Betelgeuse and what kind of star is it?
In the constellation Orion and is a red super giant
28
How old is Betelgeuse?
8.5 million years old. It is expected to explode as a supernova as bright as the moon in the night sky within the next 1,000 years or so
29
What is a supernova?
An explosion of a star
30
What is a type I supernova?
A supernova that happens in binary star systems, when one of the stars, a carbon-oxygen white dwarf, steals matter from its companion star. Eventually, the white dwarf accumulates too much matter. Having too much matter causes the star to explode, resulting in a supernova
31
What is a type II supernova?
A supernova that occurs at the end of a single star’s lifetime. As the star runs out of nuclear fuel, some of its mass flows into its core. Eventually, the core is so heavy that it cannot withstand its own gravitational force. The core collapses, which results in the giant explosion of a supernova
32
How are most of the heavy elements in the Universe created?
In supernovae
33
What is a white dwarf?
What remains of a red giant once the outer layers are blown off to form a planetary nebulla. It is a faint, small (about the size of Earth), very dense, hot star that is made mostly of carbon.
34
What are the only things denser than white dwarfs?
Neutron stars and black holes
35
What do white dwarfs become when they lose their heat?
black dwarfs
36
How many black swarfs are there currently in the Universe?
zero - it would take a white dwarf a hundred million billion years to cool enough to become a black dwarf
37
What is a brown dwarf?
Substellar objects not massive enough to ever fuse helium into hydrogen, but still massive enough to fuse deuterium (about 13 Jupiter masses)
38
What is a neutron star?
It is the collapsed core of a giant star (the core being between 1 and 3 solar masses). They are almost completely composed of neutrons due to the compression of protons and electrons. They result from the supernova explosion of a massive star, combined with gravitational collapse, that compresses the core past white dwarf star density to that of atomic nuclei
39
What is the diameter of a neutron star?
Around 20 km, but has the mas of about 1.4 solar masses
40
What is a pulsar?
Rotating neutron stars observed to have pulses of radiation at very regular intervals that typically range from milliseconds to seconds. Pulsars have very strong magnetic fields which funnel jets of particles out along the two magnetic poles. These accelerated particles produce very powerful beams of light
41
How are black holes formed?
They are formed when the mass of a star’s core that dies in a supernova explosion is more than about three times the mass of the Sun, the force of gravity overwhelms all other forces
42
What is accretion?
The coming together and cohesion of matter under the influence of gravitation to form larger bodies
43
How massive are stellar mass black holes?
10 to 24 times as massive as the Sun
44
How many black holes are there in the Milky Way?
Estimated to be between ten million to a billion
45
How massive are supermassive black holes?
Millions, if not billions, of times as massive as the Sun
46
Where can supermassive black holes be found?
At the centre of virtually all large galaxies
47
What are comets primarily composed of?
Amonia, methane and water with only a small amount of rocky material
48
What are the four components of a commet?
The nucleus, the coma (the hale around the nucleus formed when solar radiation vaporises the ice), the ion tail (resulting from solar winds blowing gas particles directly away from the Sun) and the dust tail (formed from dust and rocky material that is left behind as it moves along its orbit)
49
Where do comets originate from?
Either the Örpik-Oort Cloud (long-period) or the Kuiper Belt (short period)
50
What are asteroids?
Small bodies orbiting the Sun that are composed primarily of rock or metal
51
What does asteroid mean?
Star-shaped
52
Why are asteroids irregular in shape?
They are too small to exert enough gravitational pull to become spherical in shape
53
What do comets become once the ice has gone?
Asteroids
54
What are metiorites?
Fragments of meteoroids (small rocks - smaller than asteroids - in orbit around the Sun) which have fallen to Earth
55
What are meteors?
Meteoroids that burn up when entering the Earth's atmosphere, causing shooting stars
56
What is a meteor shower?
The phenomena that occurs when the Earth moves through the debris stream of an orbiting comet (or occasionally asteroids)
57
Where do the majority of meteorites come from?
The majority are from asteroids, though some originate from comets, the Moon and Mars
58
How heavy is the largest known meteorite on Earth?
60 tonnes (Hoba meteorite found in Namibia)
59
What essential complex organic compounds have been found on meteorites?
Amino acids

Astronomy (2 decks)

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