Astronomical Instruments, Celestial Measurements, and Distances

Question 1

Astronomical Unit (AU)

Answer 1

A way of measuring distances in Astronomy. It equals roughly 93 million miles which is (not so) coincidentally the same distance between the Sun and Earth. Using this we can determine distances when a light year is too large a unit of measurement. For example, Jupiter is roughly 5 AU from the Sun which means it’s 5 times the distance from the Sun that Earth is.

Question 2

Light Year

Answer 2

The distance that light travels in one year, roughly 6 trillion miles or 63,000 AU.

Question 3

Parsec

Answer 3

A unit of measurement in Astronomy, equal to about 206,000 AU or 3.2 light years.

Question 4

Absolute Magnitude

Answer 4

A measure of intrinsic brightness used for celestial objects.

Question 5

Hertzsprung Russell Diagram

Answer 5

A Hertzsprung Russell Diagram is used to determine the relationship between a star’s absolute magnitude, type and temperature in scatter-graph form.

• Russell Diagram show the values of luminosity and color (which is linked to temperature) against each other.

Question 6

Spectroscope

Answer 6

A Spectroscope is used to measure light over the electromagnetic spectrum. Often this means that it breaks down the light into its individual wavelengths, much like a prism breaks down sunlight into individual colors. This is useful for a variety of purposes, including identifying what objects are composed of based on their visible spectrum.

Question 7

Absorption lines

Answer 7

Absorption Lines are when a certain shade of color on that strip is black, indicating that a particular frequency of light has been blocked.

• Let’s use UV light as an example. In Earth’s atmosphere there are substances that block particular frequencies of light. One of these is ozone (which blocks UV light). If we were looking at the sun through Earth’s atmosphere, the UV light would show as an absorption line (black stripe) on a spectrum since it’s been blocked.

Question 8

Emission Lines

Answer 8

The opposite of an absorption line is an Emission Line. This indicates the emission of a particular wavelength of light (rather than the absorption), it shows up as a bright line on a spectrum.

• An Absorption line on a spectrum means a wavelength has been blocked and an Emission line means that particular wavelength is present.

Question 9

Angstrom

Answer 9

Used to measure wavelengths of electromagnetic radiation and named after Anders Angstrom. Radio waves have the longest wavelength and Gamma rays have the shortest.

Question 10

Doppler Effect

Answer 10

The Doppler Effect describes how a wave’s frequency changes based on the motion of the observer in relation to the source of the wave.

• A common example is the change in the frequency of sound waves from a passing car or an ambulance siren. You can usually tell it’s getting closer by the rise in pitch as it approaches. That’s actually the sound waves getting more and more compressed the closer the source come to you, the listener. Once the source passes, the sound waves get longer and longer which changes how they sound again.
• Using the Doppler Effect, astronomers can detect the relative motion of celestial objects and even determine their speeds.

Question 11

Radial Velocity

Answer 11

Radial Velocity is the speed at which an object is moving towards or away from the viewer here on earth. This is one of the ways that astronomers determine whether stars have exo-planets. If a star does have an exoplanet, the radial velocity of the star will slightly change when the planet’s gravity affects its orbit. This is also the way that astronomers know that the universe is expanding, by measuring the radial velocities of galaxies as they are moving away from us.

Question 12

Parallax

Answer 12

Parallax is the apparent shift in the position of an object when the angle of viewing is changed.

• That sounds kind of complicated but it really isn’t. Think about it this way: Let’s say you’re standing in a field and there are two fence posts directly in front of you but a few hundred yards away. One is at 100 yards and the other is at 500 yards. If you take a few steps to the left, both fence posts will appear to move as your perspective changes, but the one at 100 yards will appear to move much more than the one at 500 yards.

Question 13

Triangulation

Answer 13

Astronomers will note the angle of a star which they wish to find out the distance. They will then wait a period of time (say 6 months) and will take the angle of the star again. Since the earth has moved around the sun during this time, the angle is completely different. Using a healthy dose of Trigonometry, they can accurately determine the distance by computing the difference of those two angles. This method works on stars up to 400 light years away.

Question 14

Proper Motion

Answer 14

Proper Motion is the movement of the star itself rather than the observer. It is measured by taking the angle of the star’s movement over time compared to the center of the solar system. In this way, stars will often seem to move to different constellations over time. The more the angle changes over a short period of time, the closer the star can be assumed to be.”m

Question 15

Telescope

Answer 15

A device that is used to see distances far beyond normal eyesight. The first telescope, invented in the Netherlands in 1608, was refractive and was not used for astronomy.

Question 16

Refracting Telescope

Answer 16

The use of the telescope for astronomy was pioneered by Galileo. It operates by having two lenses (objective and eyepiece) that focus the light from an image so that the viewer can see it more clearly. This is your typical “Tube” telescope. The downside of refractive telescopes is that they cannot see the entire spectrum of light due to the glass and the size of the lens is limited. Creating a lens free of imperfections is more difficult the larger the size. These problems were mostly solved with the invention of the reflective telescope.

Question 17

Reflective Telescope

Answer 17

Uses curved mirrors to reflect gathered light and form an image. Light enters the telescope and is then reflected towards an eyepiece through a series of mirrors. The first practical reflective telescope was built by Isaac Newton. This type of telescope allows much larger lenses to be used than refracting telescopes since the entire mirror can be supported instead of just the edges of the lens. As a general rule of thumb, the maximum useful magnification is between 50 and 60 times the diameter of the lens or mirror. Most telescopes used by professional astronomers today are reflective.

Question 18

Radio Telescope

Answer 18

A Radio Telescope is used to see celestial bodies in the “radio spectrum. Since there is so much radio interference around population centers, they’re usually placed far away from cities and inside valleys to avoid that interference. Radio waves have extremely long wavelengths, so it’s important to collect as many of them as you can. Due to this, radio telescopes tend to have very large dishes.

Question 19

X-ray Telescope

Answer 19

Like the Radio Telescopes, an X Ray Telescope is able to see beyond the visible spectrum and identify objects that may otherwise be obscured. They are usually required to be either in the upper atmosphere or space-based as the Earth’s atmosphere absorbs X-rays.

• While we can’t see black holes with any normal telescope, the X-ray energy coming from them is easily seen by an X-ray telescope.

Question 20

Solar Mass

Answer 20

Astronomers use Solar Mass as a way of determining the size of celestial bodies. One solar mass is equal to the size of our sun. Knowing this, we can easily get a frame of reference for other stars. If we say another star is 15 solar masses in size, we can instantly draw a comparison – It’s fifteen times the size of our sun.