ASTR Ch. 3 HMWK

The value of X-ray and gamma-ray astronomy is based on the fact that some of the most energetic sources in the cosmos radiate at these wavelengths. Magnetic storms in stellar atmospheres (including storms on the Sun), exploding stars and their nebular remnants, the regions surrounding neutron stars and black holes, and the innermost regions associated with active galactic nuclei characterize the highest energy, shortest wavelength regime. What would you need to obtain a successful X-ray image of a high-energy source?

A telescope designed and built to be launched into space. A cosmic source of high temperature.

At these wavelengths, it is necessary to build telescopes with very large light-collecting__________ to obtain maps of sufficient sensitivity to faint cosmic signals.

areas

At these wavelengths, it is necessary to build telescopes with very large signal-sensing ________ to obtain maps of sufficient detail.

baselines

Astronomical observations at these wavelengths can be obtained even during .

storms

Considering the properties of the other parts of the electromagnetic spectrum, which type of radiation do you think was able to penetrate the dust and smog to obtain the image on the right?

Infrared

Ranking Task: Reflecting Telescopes and Light Collection

Left to Right 1. Large Binocular Telescope Two 8.4-m mirrors 2. Keck1 : One 10-m mirror 3. Hobby-Ebberly : One 9.2-m mirror 4. Subaru One 8.3-m mirror 5. Gemini North: One 8.3-m mirror 6. Magellan 11: One 6.5-m mirror Larger mirrors have a larger light-collecting area. Remember that the light-collecting area is proportional to the square of the mirror diameter. For example, if Mirror A has twice the diameter of Mirror B, then Mirror A has 2x2 = 4 times the light-collecting area of Mirror B.

Considering the properties of the different bands of the electromagnetic spectrum, which spectral region do you think was used to take each photo?

Photo 1 is infrared; Photo 2 is visible

Sorting Task: Characteristics of Reflecting and Refracting Telescopes

Reflecting: worlds largest telescope, most commonly used by professionals astronomers today, the hubble space telescope Refracting:incoming light passes through the glass, very large telescope becomes top heavy, the worlds largest is 1 meter in diameter, galileos telescope

Astronomical sources emit electromagnetic radiation at various wavelengths. Some sources might emit just visible and infrared radiation. Other sources might emit gamma, UV, visible, and infrared radiation. Some of that radiation travels in the direction of Earth and can be detected with the right telescopes placed in the right locations. Some wavelengths can be read in the atmosphere. However, the majority of wavelengths are either read from space or Earth's surface. Which observations would require you to launch a telescope above the Earth's atmosphere? Please drag each observing mode below into either the ground-based (Surface) zone or space-borne (Space) zone, depending on the respective observing requirements.

Space Zone: Far-infrared, far- UV, X-ray, Gamma-Ray Surface: Radio, visible

Shown following are the primary mirror arrangements and total light-collecting area of five different telescopes. Notice that although the arrangements look similar to those in Part B, the light-collecting areas are not the same. Also listed is an amount of time (exposure time) that each telescope will be pointed at the same distant galaxy. Again assume that the quality of these mirrors, the detectors, and the observing conditions are identical. Rank the telescopes from left to right based on the brightness of the image each telescope will take of the galaxy in the time indicated, from brightest to dimmest. To rank two (or more) telescopes as equal, drag one on top of the other(s).

all equal to each other As your answer correctly indicates, it is the product of the light-collecting area and the exposure time that determines the total amount of light collected from a distant object.

Shown following are the primary mirror arrangements and total light-collecting area of five different telescopes. Each mirror uses a different segmented arrangement, but assume that they are all equivalent in quality and in their ability to focus light. Also assume that the telescopes use identical detectors and have the same observing conditions. Rank the telescopes from left to right based on their ability to detect very dim objects, from greatest to least. To rank two (or more) telescopes as equal, drag one on top of the other(s).

all on each other, all surface area is 100^2 If all else is equal (such as mirror quality, detector, and observing conditions), the ability to detect dim objects depends only on light-collecting area. Because all the telescopes shown have the same light-collecting area, they all can detect dim objects equally well. The arrangement of the mirrors does not matter, as long as they are arranged and shaped so they bring light to a perfect focus.

If our eyes were sensitive only to X rays, the world would appear __________.

dark because X-ray light does not reach Earth's surface

If you had only one telescope and wanted to take both visible-light and ultraviolet pictures of stars, where should you locate your telescope?

in space While visible light can be observed from the ground, ultraviolet light can be easily observed only from space. Indeed, the capability of observing ultraviolet light is a major advantage of the Hubble Space Telescope over larger ground-based telescopes.

The James Webb Space Telescope is designed primarily to observe __________.

infrared light Its location in space allows it to observe infrared wavelengths that do not penetrate our atmosphere to the ground.

Radio astronomers have pioneered the use of multiple telescopes working in concert that can produce maps of radio emission as detailed as optical images. These arrays of multiple telescopes are known as ______________

interferometers

Which of the following forms of light can be observed with telescopes at sea level?

visible light radio waves Both visible light and radio waves pass almost freely through Earth's atmosphere, and therefore are easily observed with ground-based telescopes. The only other light that can be observed with ground-based telescopes is infrared, but it can be detected only at high altitudes (such as mountaintops) and even then only in selected portions of the infrared spectrum.