Astronomers have proposed using interferometry to make an extremely high- resolution telescope. This proposal involves placing a number of infrared telescopes in space, separating them by thousands of kilometers, and combining the light from the individual telescopes. One design of this kind has an effective diameter of \(6000 \mathrm{~km}\) and uses infrared radiation with a wavelength of \(10 \mathrm{~mm}\). If it is used to observe an Earthlike planet orbiting the star Epsilon Eridani, \(3.22\) parsecs (10.5 light-years) from Earth, what is the size of the smallest detail that this system will be able to resolve on the face of that planet? Give your answer in kilometers.

Short Answer

Expert verified
The smallest detail that this system will be able to resolve on the face of the planet orbiting Epsilon Eridani is approximately \(20.15 \mathrm{~km}\).

Step by step solution

01

Convert Given Parameters

The effective diameter is given in kilometers and the wavelength in millimeters. Converting these into the same unit (meters) to avoid errors in calculation, gives \(D = 6000 \times 10^3 \mathrm{~m}\) and \(\lambda = 10 \times 10^{-3} \mathrm{~m}\). The distance is given in parsecs. To convert it to meters, use the conversion factor, \(1 \mathrm{~pc} = 3.086 \times 10^{16} \mathrm{~m}\), so \(d = 3.22 \times 3.086 \times 10^{16} \mathrm{~m}\).
02

Calculate Angular Resolution

With values for the diameter and the wavelength, the angular resolution of the telescope can be found using the formula \[\theta = 1.22 \frac{\lambda}{D}\]. Substituting the values from the previous step yields \(\theta = 1.22 \times \frac{10 \times 10^{-3} \mathrm{~m}}{6000 \times 10^3 \mathrm{~m}}\). This simplifies to \(\theta = 2.03 \times 10^{-9} \mathrm{~rad}\).
03

Calculate the Smallest Observable Detail

The smallest observable detail can be calculated using the formula \(s = d \cdot \theta\). Substituting the values from the previous steps gives: \(s = 3.22 \times 3.086 \times 10^{16} \mathrm{~m} \times 2.03 \times 10^{-9} \mathrm{~rad}\). This simplifies to \(s = 20.15 \mathrm{~km}\).

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Angular Resolution
When we talk about the clarity with which a telescope can distinguish small details, we're referring to its 'angular resolution'. Think of this as the telescope's ability to take sharp photos rather than blurry ones, even from great distances. The angular resolution is measured in radians and signifies the smallest angle in which we can tell apart two points of light or objects in space.

Using this concept, astronomers can calculate how fine the details they can see with their telescopes are. They use the formula \theta = 1.22 \frac{\lambda}{D}\, where \theta\ is the angular resolution, \lambda\ is the wavelength of the light being observed, and \(D\) is the diameter of the telescope's aperture. The '1.22' comes from a calculation involving the diffraction pattern of a circular aperture.

Therefore, astronomers use this formula to evaluate the capability of a telescope's design, like the one proposed using interferometry, which allows for the creation of an 'effective' aperture much larger than what a single telescope can provide.
Infrared Telescopes
Infrared telescopes are the special 'glasses' that astronomers use to see a different 'color' of the universe. While our eyes can see visible light, infrared telescopes detect infrared radiation - a form of light that has longer wavelengths than what we can see. These telescopes can observe celestial objects that are too cool or too far away to emit much visible light, but which glow warmly in the infrared.

Unlike visible light, infrared can pass through dust clouds in space, allowing us to peek into regions where stars are being born. This capability makes infrared telescopes like the ones in our evoked astronomical interferometry system invaluable for understanding the more secretive corners of the cosmos. They are also placed in space to avoid Earth's atmosphere, which absorbs many of the infrared wavelengths.
Parsecs to Meters Conversion
A parsec is like a galactic ruler. It's a unit of measurement that astronomers use to gauge the staggering distances between stars and galaxies. One parsec is equivalent to 3.086 x \(10^{16}\) meters. To convert parsecs into meters, we multiply the number of parsecs by this conversion factor, giving us a distance in meters - something a bit more familiar to our everyday ways of measuring.

When a star, like Epsilon Eridani, is 3.22 parsecs away, we can convert this into meters by multiplying 3.22 by 3.086 x \(10^{16}\) meters. This sort of conversion allows astronomers to use Earth-based mathematical principles and physics to understand the properties and behaviors of celestial bodies at these immense distances.
Scientific Notation
Scientific notation is like shorthand writing for numbers that are too big or too small to be conveniently written in decimal form. In astronomy, where we deal with huge distances and timescales, it's essential for communication and calculation.

For example, the distance to a nearby star might be 40,000,000,000,000 kilometers, which is cumbersome to write and read. In scientific notation, this number becomes simply 4 x \(10^{13}\) kilometers. It's shorthand that makes big or tiny numbers more manageable by using powers of ten. This method reduces errors and streamlines calculations, such as those required when dealing with astronomical distances and the technical specs of equipment like telescopes.

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Most popular questions from this chapter

It has been suggested that extraterrestrial civilizations would choose to communicate at a wavelength of \(21 \mathrm{~cm}\). Hydrogen atoms in interstellar space naturally emit at this wavelength, so astronomers studying the distribution of hydrogen around the Galaxy would already have their radio telescopes tuned to receive extraterrestrial signals. (a) Calculate the frequency of this radiation in megahertz. Is this inside or outside the water hole? (b) Discuss the merits of this suggestion.

Use the Starry Night Enthusiast \({ }^{\text {TM }}\) program to examine the planet Mars. Open the Favourites pane and double-click on Solar System > Mars to view this planet from about \(6800 \mathrm{~km}\) above its surface. (Click on View > Feet to remove the astronaut's spacesuit from the view.) You can zoom in or out on Mars using the buttons in the Zoom section at the right of the toolbar. You can rotate Mars by placing the mouse cursor over the image and moving the mouse while holding down the mouse button. (On a two-button mouse, hold down the left mouse button.) Rotate Mars and zoom in and out to familiarize yourself with the different surface features. Based on what you observe, where on the Martian surface would you choose to land a spacecraft to search for the presence of life? Explain how you made your choice.

Suppose someone told you that the Viking Landers failed to detect life on Mars simply because the tests were designed to detect terrestrial life-forms, not Martian life-forms. How would you respond?

Search the World Wide Web for information about the Mars Express orbiter and the Spirit and Opportunity rovers. What discoveries have these missions made about water on Mars? Have they found any evidence that liquid water has existed on Mars in the recent past? Describe the evidence, if any.

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