Astr 121 Exam 1 Flashcards Set (Ultimate)

Scientific notation of 1,232,000,000

1.232 × 10⁹

Scientific notation of 0.00000453

4.53 × 10⁻⁶

Prefix for one million

Mega

Value of one astronomical unit (A.U.)

150 million kilometers

Main way we see history in astronomy

The light from stars takes time to travel to Earth, so we see them as they were in the past.

Correct order of steps in the scientific method

Observation, hypothesis, experiment, conclusion

Difference between a hypothesis and a theory

A theory has been proven by experiments, while a hypothesis is a proposed explanation.

Example of a pseudoscientific argument

Relying on anecdotal evidence without supporting experiments

Apparent size of an object in the sky

Angular size

Star located directly above Earth's north pole

Polaris

Meaning of 'circumpolar'

Stars that never set at a particular latitude

Two hemispheres divided by the celestial equator

Northern and Southern

Tycho Brahe's contribution to Kepler’s work

Accurate data on planetary positions

Kepler’s second law of planetary motion

Planets sweep out equal areas in equal times.

Orbital period of a planet 100 A.U. away from the Sun

100 years

Difference between weight and mass

Mass measures the amount of matter; weight is the force of gravity on that mass.

Newton's law of gravitation

The force of gravity between two objects is inversely proportional to the square of the distance between them.

Effect of tripling the distance between Earth and Sun on gravitational force

It decreases by a factor of 9.

Galileo's method to measure the speed of light

Use a rotating mirror

Electromagnetic spectrum

The entire range of frequencies of electromagnetic radiation.

Speed of light

3 x 10⁸ meters per second.

Cause for an electron to transition to a higher energy level

Absorption of a photon.

Black body spectrum

A spectrum emitted by a glowing solid object.

Law relating temperature of a body to peak wavelength of its emission

Wien's Law.

Most important property of a telescope

Light-gathering ability.

Type of telescope most modern astronomers use

Reflecting telescopes.

Relation of telescope's light-gathering power to its objective lens area

It is proportional to the square of the diameter.

Function of a spectrograph in astronomy

Record and analyze light from astronomical objects.

Why astronomers use CCD cameras instead of photographic plates

They provide better resolution and can store data electronically.

Function of adaptive optics

To increase the resolution of telescopes by compensating for atmospheric distortion.

Composition of the Sun

Mostly hydrogen and helium.

What are sunspots?

Cooler areas caused by magnetic activity.

How solar activity affects Earth

It causes solar winds that may impact satellites and communication systems.

Thermonuclear fusion

The process by which nuclei combine to release energy.

Time taken for photons created in the Sun's core to reach its surface

Several hundred thousand years.

Solar neutrino problem

The discrepancy in the number of neutrinos detected from the Sun.

Most common element in the Sun

Hydrogen

The part of the Sun we see from Earth

The photosphere

Hottest part of the Sun's atmosphere

The corona

Cause of aurorae on Earth

Solar wind particles spiraling into Earth's atmosphere

Active regions in the Sun's atmosphere are connected with

The Sun's magnetic field

Effect of lower solar activity like the Maunder Minimum

Cooler temperatures

Part NOT included in the Sun's active regions

Radiative zone

Reason sunspots appear darker

They are cooler than the surrounding material

What the Sun's 11-year cycle indicates

The number of sunspots cyclically increases and decreases

Challenge to the theory that the Sun burns coal

Dating of radioactive rocks shows that Earth and Sun are billions of years old.

Power source of the Sun

Fusion of hydrogen into helium

Average time for a photon to reach the Sun's surface

Close to a couple hundred thousand years

Initial movement of energy outward from the Sun's core

Radiation

Main method of energy transport in the final 30% of its journey

Convection

What proves the Sun's energy source

Neutrinos

E=mc² explanation

A little bit of mass can be converted into a substantial amount of energy

Start of the fusion process in the Sun

Two protons

End product of the proton-proton chain

Helium-4

Reason the Sun doesn't collapse under its own gravity

Nuclear fusion balances gravity by maintaining high temperature and pressure

How astronomers study the Sun's interior

Study oscillations (pulsations) of the Sun's surface

What does redshift indicate about a galaxy's movement?

Redshift indicates that the galaxy is moving away from us.

How do you calculate the speed of a galaxy if an emission line shifts from 500 nm to 550 nm?

The speed can be calculated using the redshift formula, indicating a speed of approximately 0.1c.

What does an absorption line shift from 1000 nm to 1100 nm indicate?

It indicates the object is moving away from us at approximately 0.1c.

What is the first type of telescope used in astronomy?

The refractor telescope.

Why do telescopes perform better in space?

They avoid atmospheric interference.

What is the best measure of a telescope’s capability?

Its light-gathering ability.

What is the misconception about mirrors filtering UV light?

Mirrors reflect UV light; they do not filter it.

How to find the eyepiece focal length for high magnification in a telescope?

Use the formula: magnification = telescope focal length / eyepiece focal length.

How does a larger telescope diameter affect light collection?

It collects four times more light than a smaller telescope.

How does wavelength affect resolution in astronomy?

Shorter wavelengths improve resolution.

What improves resolution in radio telescopes?

Connecting multiple dishes together.

What is the difference between Greenbank and an interferometer?

Greenbank is a single-dish radio telescope.

Why might mirrors be seen as less efficient than lenses?

Some believe mirrors absorb more light, but they are generally more efficient.

What materials are radio telescope dishes made from?

Conducting materials.

What is the JWST's classification?

The JWST is a space telescope.

What is a key advantage of CCDs over traditional photodetection methods?

CCDs are much more efficient, capturing a greater percentage of light.

What instrument analyzes light into its component wavelengths?

A spectrograph.

Why are telescopes positioned near the equator?

To maximize the area of the sky covered due to the rotation of the Earth.

What function does adaptive optics serve in telescopes?

To correct for atmospheric distortion in real-time.

Which type of telescopes are used to detect X-rays?

X-ray telescopes, which must be used above the atmosphere.

Wavelength corresponding to a frequency of 1000 kHz (c = 3 x 10⁸ m/s)

300 m

False statement about the speed of light

It may be different in different places and times in the universe.

What are isotopes?

Two versions of an element that differ in terms of number of neutrons.

False statement about electromagnetic radiation

All wavelengths of electromagnetic radiation carry the same energy.

Definition of wavelength in light

The distance between the crests of the waves.

Electromagnetic wave with the longest wavelength

Radio waves.

Reason telescopes must be placed in space for certain wavelengths

Our atmosphere blocks these wavebands.

Color of light with the highest frequency among yellow, red, and blue

Blue.

False statement about photons

They are all blocked by the Earth's atmosphere regardless of frequency.

False statement about measurements of the speed of light

Galileo first measured its speed using lamps separated by great distances.

False statement about blackbodies of different temperatures

The 5000 K blackbody's color would be at a shorter wavelength than that of the 10,000 K blackbody.

Wavelength of peak emission for the Sun (5800 K) using Wien's law

517 nm.

Reason different elements give off or absorb different spectral lines

The spacing of energy levels for electrons is different in each element.

Observed spectrum when electrons fall to lower energy levels in a gas cloud

An emission line spectrum.

How absorption lines are produced in a spectrum

A cool gas sits in front of a continuous source filtering out specific wavelengths.

Brightness comparison at 1 m vs. 10 m distance from a light bulb

100x brighter at 1 m.

Brightness change when a star doubles its temperature

Increases by 16x.

Brightness change when a star doubles its radius but remains the same temperature

Increases by 4x.

Waveband with the greatest energy for a photon of light

Gamma-rays.

What is FALSE about Kepler's laws of planetary motion?

He derived his three laws from Newton's equations.

What is the semi-major axis in an ellipse?

Half of the longest axis through the ellipse center.

What happens to a planet when it is near aphelion in its orbit?

It is moving its slowest in its orbit.