Quiz 2 Review - Chapter 20: Our Universe

Unlike planets, stars:

Stars -undergoes nuclear reactions that burn hydrogen in their cores -very high temperatures in core to burn H -very high mass, at least 75x the mass of Jupiter!

The _______ was born from a Nebula, when a cloud of dust and gas known as a solar nebula, collapsed, and in the middle of this formation, matter condensed into a burning ball of gas that became our ________.

Sun

How does a lunar eclipse occur?

When the Earth is in between the Sun and Moon, Earth's shadow blocks sunlight, making Moon appear dark

How does a solar eclipse occur?

When the Moon is in between the Earth and Sun, the Moon blocks Sunlight from part of Earth.

With all these collisions (from Earth's formation), and the release of heat by radioactive isotopes, early Earth was completely _________.

melted

How do Nebula "Stellar Nurseries" form?

• Accumulation of interstellar gas and dust due to gravitational forces. • If some pockets have enough mass star formation (term 5).

Early Earth characteristics:

- After the surface cooled: reddish sky over bright green oceans. Why? No free oxygen. - Oceans were filled with dissolved iron, making them green. - The atmosphere was rich in methane, making it reddish.

Describe Orion

- Closest large star-forming region to Earth, - It is very bright - Can be spotted with the naked eye, while offering a peek at stellar birth for those with telescopes.

Star Formation steps

- Gravitational forces increase (with enough mass) and get converted to the kinetic energy of the fast-moving atoms in between interstellar gas, which collide with one another and generate heat. - When the temperature reaches 10 million degrees Kelvin (18 million degrees Fahrenheit), nuclear fusion begins. - The outward pressure created by the fusion reactions prevents further collapse, and the clump of burning hydrogen gas stabilizes and becomes a star. AKA Stars form when a cloud of gas, out in a nebula, collapses under the influence of gravity.

Solar systems are believed to form based on the Nebular hypothesis:

- Our solar system began forming within a concentration of interstellar dust and hydrogen gas. - This cloud contracted under its own gravity and our protoSun formed in the hot dense center. - The remainder of the cloud formed a swirling disk called the solar nebula. - Basically, this cloud spinning faster as it collapsed, due to the preservation of angular momentum. - The dust particles combined to form planetesimals.

What supports this model (term 11)?

-Modern telescopic observations show evidence for such flattened disks. We see stars forming in the depths of giant clouds of gas and dust, and we even see young stars with disks of debris around them, which look just like the debris disk we think the planets formed from. -Observed compositional trend from metal and rock in the inner (warmer) solar system, to gases and ices in the outer (colder) solar system, supports this model. -Sun, Moon, Earth, and meteorites all appear to have same age (about 4.6 billion years) suggesting they formed in a single event

What other observations lead to the proposal of the model (term 11) in the first place?

1) All the planets orbit the Sun in the same direction. 2) Most of their moons also orbit in that direction. 3) Most planets (and the Sun) rotate in the same direction

The Big Bang Hypothesis became the Big Bang Theory with what evidence?

1) the galaxies are moving away from each other; 2) the farther away they are, the faster they're moving; 3) All of space is filled with the cosmic microwave background radiation-the leftover light from the explosion, which has stretched into longer radio waves.

Approximately, how old is the universe?

13.8 billion years old

The Hubble Space Telescope began observing "deep fields" in what year?

1995

What is a nebula (aka a molecular cloud)?

A cloud of gas and dust in interstellar space. These are immense and common. This is where stars (suns) are born.

Super moon

A full moon that appears larger and brighter.

What type of theory is the Big Bang Theory?

A robust theory - one that is consistent with all evidence and has yet to be proven wrong.

What's a galaxy?

A system of billions of solar systems, clouds, space dust, and millions to trillions of stars.

Early planet Earth was created when?

About 4.6 billion years ago.

Where is the Milky Way galaxy within our solar system?

Actually, the solar system (including our Sun) is within the Milky Way galaxy, on one of the spiral arms, about halfway out in the disk of the galaxy.

What was needed to get deep field photographs?

An "empty" piece of sky was needed that contained no bright sources of visible light that might drown out fainter objects. The direction chosen was away from the millions of faint stars and dust of the plane of our own galaxy, the Milky Way

(Continuation of term 35) After O2 was added, what happened to form Banded Iron Formations?

Each released molecule of O2 reacted with a dissolved atom of iron, making it settle to the bottom as a solid.

______________________ developed photosynthesis and added O2 to the air and water, causing big changes.

Early bacterial life

What happened that lead to the creation of the mantle and crust?

Earth completely melted. This allowed the heavier iron to sink to form the core, the lighter rock rose to eventually become the mantle and crust.

Why solar and lunar eclipses only occur two times each year?

Eclipses only occur when the Moon crosses the orbital plane and at the same time is directly in line with the Sun and Earth. And the plane along which the Moon orbits Earth is not exactly parallel to the plane in which Earth orbits the Sun. The planes are approximately 5 degrees out of alignment, as shown in this figure.

Why was early Earth like this (follow-up to term 33)?

Evidence for this is to be found in Banded Iron Formations (layered iron-rich rock), which record the fact that huge amounts of iron were dissolved in the oceans. This can only happen when there is no free oxygen (O2 ).

Who proposed that the universe began with a great explosion, later on called the "Big Bang" hypothesis?

Father Georges Henri Joseph Édouard Lemaître (who was a priest, astronomer, physicist).

A standardized way to describe the direction in which to observe stars and other astronomical objects is called a(n) _______ of _________. This helps us explain many features and events, such as eclipses.

Frame (of) reference

In the 1920's, what was Edwin Hubble's (and his team's) observation?

He found that most of the galaxies are moving away from each other.

What else should have been created by the explosion (in regards to term 21)?

However, an explosion should have also created light, which should still be detectable. Unfortunately, the technology needed to detect the leftover light from the big bang did not exist then (in the 1920s). So, a 'prediction' was made by the hypothesis that the leftover light should exist.

When and how was that leftover light (reference to term 22) detected?

In 1965 by radio telescopes.

How did the Hubble Space Telescope avoid the blurring effect on the atmosphere?

It floats in orbit. And doesn't have bright sources of light at other wavelengths, such as X-ray or radio waves.

What is the Milky Way Galaxy?

It is an average-sized, spiral galaxy that contains the solar system. It is formed through consolidation and organization of a hugh rotating mass of dust, gas, and other material.

What are Stromatolites?

Laminated rock formed by the growth of cyanobacteria.

What are three important types of large features in the Universe?

Nebulas, galaxies, and stars.

Was there free oxygen in early planet Earth?

No, not until photosynthetic organisms evolved.

How do planets form?

Planets, form when material in the disk around a pre-existing star begins to condense around rock/ice cores.

(Continuation of term 36) After all of the iron was scrubbed from the oceans, what process happened over the next 1 billion years?

The O2 rose into the atmosphere and removed the methane.

What evidence supports the Big Bang Theory?

The galaxies are almost all moving away from each other, and the further away the galaxies are, the faster they're moving away. This is just what you'd expect from an explosion.

How were oceans formed?

The melting released volcanic gases. The early atmosphere was mostly likely steam from all these volcanic emissions. Said steam atmosphere cooled and eventually formed the oceans.

Perigee

The point in the orbit of the moon or a satellite at which it is nearest to the earth.

What is the leftover light called?

This light is cosmic microwave background (CMB) radiation, or radiation from the birth of the universe.

Why do astronomers want to observe more distant galaxies?

To shed light on how they form, and how their shapes and sizes change over time.