ASTR 129 Exam Chap 8

About how old is the solar system?

4.5 billion years

The orbital speed of the solar nebula at Pluto's average distance from the Sun is about 5 km/sec. When the solar nebula was about 3000 AU in radius, how fast would the same material have orbited? (Remember that when the cloud was larger, motions were more random, so we can calculate only the average.) Use the law of conservation of angular momentum (see Section Conservation Laws in Astronomy).

v = 70 m/s

What is Jupiter's main ingredient?

hydrogen & helium

Which of the following did not occur during the collapse of the solar nebula?

Concentrating denser materials nearer the Sun

The solar nebula is 98% ...

Hydrogen & Helium

What is the leading hypothesis for the origin of the Moon?

It formed from the material ejected from Earth in a giant impact

which of the following is not true about the young Sun?

It was much brighter and hotter than it is today

What fraction of the large moons of the planets orbit in the same direction as their planets rotate?

Most

Part A: How massive would Earth have been if it had accreted hydrogen compounds in addition to rock and metal? Assume the same proportion of the ingredients as listed in the table. Part B: What would Earth's mass be, if it had been possible to capture hydrogen and helium gas in the proportion listed in the table?

Part A: M icy earth/M real Earth = 3.3 Part B: M gaseous Earth/M real Earth = 170

You are dating rocks by their proportions of parent isotope potassium-40 (half-life 1.25 billion years) and daughter isotope argon-40. Part A: Find the age of a rock that contains equal amounts of potassium-40 and argon-40. Part B: Find the age for a rock that contains three times as much argon-40 as potassium-40.

Part A: t= 1.25 billion years Part B: t= 2.50 billion years

You are dating Moon rocks based on their proportions of uranium-238 (half-life of about 4.5 billion years) and its ultimate decay product, lead. Part A: Find the age for a rock for which you determine that 61% of the original uranium-238 remains, while the other 39% has decayed into lead. Part B: Find the age for a rock for which you determine that 73% of the original uranium-238 remains, while the other 27% has decayed into lead.

Part A: t= 3.21 billion years Part B: t= 2.04 billion years

You are dating Moon rocks based on their proportions of uranium-238 (half-life of about 4.5 billion years) and its ultimate decay product, lead. Part A: Find the age for a rock for which you determine that 55% of the original uranium-238 remains, while the other 45% has decayed into lead. Part B: Find the age for a rock for which you determine that 68% of the original uranium-238 remains, while the other 32% has decayed into lead.

Part A: t= 3.88 billion years Part B: t= 2.50 billion years

How many of the planets orbit the Sun in the same direction that Earth does?

all

which lists the major steps of solar system formation in the correct order?

collapse, condensation, accretion

leftover ice-rich planetesimals are called

comets