Astro Exam 3
How far away would a star with a parallax of 0.2 arcsec be from us?
5 parsecs
Some objects in space just don't have what it takes to be a star (just like many hopefuls in Hollywood don't.) Which of the following is a "failed star", an object with too little mass to qualify as a star?
A brown dwarf
If everything in the solar system is moving around, why do the Perseid meteors repeat regularly around August 11th or so?
Because the Earth in its orbit intersects the same swarm of meteor particles at the same time each year
The most common element in the Sun is
Hydrogen
What features are abundant on Callisto and Ganymede and almost absent on Europa and Io?
Impact Craters
Why do astronomers today think that we have an asteroid belt and not a planet between Mars and Jupiter?
Jupiter's gravity prevented material in that zone from getting together
The telescope in space that allowed astronomers to find thousands of exoplanets and exoplanet candidates by making very careful measurements during a planet transit was called:
Keplar
Which law do astronomers use to determine the masses of the stars in a spectroscopic binary system?
Keplars third law
After a lot of work, a group of graduate students has finally measured the wavelengths of many dozens of lines in the spectrum of a distant star. If a number of the lines come from molecules such as titanium oxide, the star is likely to be which spectral type:
M
Which of the following types of star is the coolest (has the lowest surface temperature)?
M
Which element plays the same role on Titan as water does on Earth (existing as gas, liquid, and solid)?
Methane
The moon Triton orbits which of the planets?
Neptune
Which of the following worlds does NOT have a ring?
Pluto
What is the best reason astronomers have come up with to explain why sunspots are cooler and look darker?
Sunspots are places where the strong magnetic fields in the Sun resist the upward motion of bubbling hot gases from underneath
A type of planet that our surveys of exoplanets are revealing around other stars, but we don't have any examples of around the Sun are:
Super-Earth's
One region on Earth that has become a rich source of new meteorites in recent decades (including the meteorite from Mars that got famous because some scientists claimed they had found evidence for the building blocks of life on Mars) is:
The Antarctic
A type of star that has turned out to be extremely useful for measuring distances is
The Cepheid variables
Between 1992 and today, astronomers using large telescopes have discovered many icy pieces that orbit in the same region as the orbit of Pluto. These are believed to be members of the
The Kuiper Belt
The large reservoir of comet nuclei far beyond Pluto, from which we believe new long-period comets come into the inner solar system, is called:
The Oort Cloud
Which part of a comet is the DENSEST?
The nucleus
Which of the following statements about the Sun's photosphere is NOT TRUE?
The photosphere is significantly hotter than all the layers of the Sun beneath it (further inward)
Which of the following statements about Saturn's rings is TRUE?
The rings are made of billions and billions of individual "moonlets" (small chunks)
Astronomers call the vast, rotating cloud of vapor and dust from which the solar system formed:
The solar nebula
What do astronomers think is the origin of the many irregular moons around the outer planets (irregular meaning they are orbiting backwards and/or have eccentric orbits)?
These moons were likely formed elsewhere and captured by the giant planets
How can astronomers measure the age of a meteorite that fell from the skies?
They measure the amount still left of radioactive materials in the meteorite, and how much has turned into decay products
According to the formula E=mc2,
a little bit of mass can be converted into a substantial amount of energy
When two objects in orbit have periods of revolution that are simple ratios of each other (such as 1 to 2 or 1 to 3) we say that we have:
a resonance
The typical meteor is
a small solid particle, no bigger than a pea
Which of the following looks the brightest in the sky?
a star with magnitude -1
If there are at least a million asteroids, how did spacecraft like Galileo survive their trip through the asteroid belt?
although there are many asteroids, they are widely spaced (there is lots of space between them)
Which of the following statements about spectroscopic binary stars is FALSE?
an analysis of the ways the lines in the spectrum change allows us to calculate the star's distance directly
Which of the following is NOT a way that the moon Titan probably resembles the Earth?
at its surface the temperature and pressure are just right for water to exist in all three phases (gas, liquid, and ice)
Why did it take astronomers until 1838 to measure the parallax of the stars?
because the stars are so far away that their annual shift of position in the sky is too small to see without a good telescope
The rings of the outer planets consist of
billions of chunks (of various sizes) that all orbit the equator of each planet
Two stars that are physically associated (move together through space) are called
binary stars
Today, astronomers can measure distances directly to worlds like Venus, Mars, the Moon, or the satellites of Jupiter by
bouncing radar beams off them
How did Henrietta Leavitt "calibrate" her period-luminosity relationship for Cepheid variable stars? In other words, how did she make the general idea into a numerical rule?
by finding cepheids in star clusters whose distance was known in another way
How were the rings of Uranus discovered?
by using the Kuiper Airborne Observatory (the telescope aboard an airplane) to observe Uranus moving in front of a distant star
More than 75% of the known asteroids:
can be found in a belt between Mars and Jupiter
Coronal Mass Ejections from the Sun have many serious effects on or near the Earth. Which of the following is NOT one of these effects?
causing huge cyclones around the equator of the Earth
Which part of the Sun's atmosphere is the hottest?
corona
One of the best proofs that our theory of how the solar system formed is correct is that astronomers now observe
disks around other stars which show evidence of gaps where planets may be forming
When a chunk of cosmic material the size of a golf ball or a baseball hits the Earth's atmosphere it makes a
fireball
When astronomers say that Ganymede is a differentiated body, they mean that it:
has a heavier core, surrounded by a lighter, icy mantle and crust
When an astronomer rambles on and on about the luminosity of a star she is studying, she is talking about:
how much energy the star gives off each second
A main difference between asteroids and comets is that asteroids are mostly made of rock and comets are mostly made of
ice
Which of the following characteristics of a single star (one that moves through space alone) is it difficult to measure directly?
its mass
Astronomers now realize that active regions on the Sun are connected with
loops of magnetic field emerging from the surface of the Sun
Stars that lie in different places on the main sequence of the H-R diagram differ from each other mainly by having different:
masses
The first technique that allowed astronomers to find exoplanets involved:
measuring changes in the radial velocity (Doppler shift) of the star caused by the pull of orbiting planets
Chunks of solid material that survive passing through the Earth's atmosphere and are found on the Earth's surface are called
meteorites
Astronomers estimate that about 25 million meteors strike the Earth's atmosphere each day. How come we haven't run out of meteors in the long history of the Earth?
meteors are pieces of dirt left over from the formation of our solar system and from old comets; there is a huge supply of small dirt particles from both sources
Most of the stars we can see with the unaided eye from Earth are
more luminous (intrinsically brighter) than the Sun
Today we realize that the source of energy for the Sun is a process called
nuclear fusion
As astronomers use the term, the parallax of a star is
one half the angle that a star shifts when seen from opposite sides of the Earth's orbit
Where in the Sun does fusion of hydrogen occur?
only in the core
Where on the H-R Diagram would we find stars that look red when seen through a telescope?
only on the right side of the diagram and never on the left
The Murchison meteorite that was found in Australia in 1969 is important to scientists because it contained
organic materials, such as amino acids
You are out on the beach, enjoying the warm sunshine with friends. As you glance up at the Sun (only briefly we hope), the part of the Sun that you can see directly is called its:
photosphere
The material inside the Sun is in the form of a
plasma
Loops of ionized plasma that connect sunspot pairs are called
prominences
When energy is first produced by fusion deep in the core of the star, that energy moves outward mostly by what process?
radiation
One way to find a new meteorite is to:
search the area beneath or close to the point where a bright fireball was seen to burn out
The majority of the moons orbiting the outer (jovian) planets are:
small moons orbiting in a retrograde direction (opposite to the direction their planet turns and orbits)
When two light elements collide to undergo nuclear fusion,
some of the energy in their mass is released
An H-R Diagram plots the luminosity of stars against their:
surface temperature
Astronomers now believe that the differences in composition among the planets reflect what characteristic in the early solar system
temperature
Which of the following is not a characteristic that worlds in our solar system have in common:
that all the planets have solid surfaces on which we can see impact craters
Some years some meteor showers, such as the Leonids, feature many more meteors than at other times. What is the cause of these "meteor storms"?
the dust freed from some comets is clumpy and not evenly distributed along its orbit
Comets change as they approach the Sun in their orbits. Which of the following statements about a comet approaching the Sun is FALSE?
the gravity of the comet nucleus holds on to the evaporated material, and it all eventually freezes back into the nucleus
The measurement of cosmic distances was helped tremendously by the discovery, in the early part of the 20th century, that in Cepheid variable stars, the average luminosity was related to:
the length of time they took to vary
Ninety percent of all stars (if plotted on an H-R diagram) would fall into a region astronomers call:
the main sequence
Which of the following pieces of observational evidence does our modern "solar nebula" theory of the formation of the solar system NOT explain directly?
the plane of the orbit of Pluto
The apparent brightness of stars in general tells us nothing about their distances; we cannot assume that the dimmer stars are farther away. In order for the apparent brightness of a star to be a good indicator of its distance, all the stars would have to be:
the same luminosity
alley's Comet was given that name because Edmond Halley was
the scientist who pointed out that the orbit of the comet was such that it should return every 76 years or so
In the formula E=mc2, the letter c stands for
the speed of light
Sunspots are darker than the regions of the Sun around them because
they are cooler than the material around them (although still very hot compared to Earth temperatures)
A light curve for a star measures how its brightness changes with
time
Saturn's ring particles are composed mainly of:
water ice
