HERA: Hydrogen Epoch of Reionization Array

To begin this blog post, I first want to address and provide necessary information on our ninth conceptual objective, “I can describe: a) the functions of a telescope, b) types of telescopes, and c) why some telescopes are placed on the ground and some in space.”

A) The three main functions of a telescope include light gathering, resolution, and magnification. Light gathering is a measure of how much light the primary mirror in a reflector, and lens in a refractor can collect from objects in the distance. Resolution is a measure of the amount of detail one can possibly see in the image. This coincides with the aperture. When the aperture is doubled, the resolving details become half the size. Magnification helps the image produced by the telescope to be large enough to see the details in it.

B) There are two basic types of telescopes: refractor telescopes and reflector telescopes. Refractor telescopes use transparent lenses to collect and focus light. Reflector telescopes use a primary mirror to gather light. Some of the other types of telescopes include but are not limited to gamma-ray wavelength telescopes, visible wavelength telescopes, x-ray wavelength telescopes, inferred wavelength telescopes, and radio wavelength telescopes.

C) Some telescopes are placed in space because they are able to observe other frequencies. Certain types of light (x-rays, gamma-rays, most ultraviolet, and infrared) are only able to be studied from space because Earth’s atmosphere blocks them from ever reaching Earth’s surface. On the other hand, some telescopes are placed on the ground because they can observe light (visible light and radio) that is not blocked by Earth’s atmosphere but reaches Earth’s surface.

With all this being said, the article I found entitled, “Telescope Eyeing Universe’s First Stars Gets (Another) Big Boost,” from space.com, coincides with our ninth conceptual objective accordingly. In this article, the author, Calla Cofield, talks about the radio telescope HERA; HERA stands for Hydrogen Epoch of Reionization Array. HERA is located in the South African Karoo Astronomy Reserve. It is located on Earth, because it is a radio telescope and is able to observe radio wavelengths from Earth’s surface. It does not need to be in space to accomplish its task. HERA will be used to investigate a period in time when the very first generations of stars and galaxies formed, altering the cosmic landscape. A $5.8 million grant, from the Gordon and Betty Moore Foundation, will allow the team that works on HERA to increase the number of antennas in the array from 240 to 350; this will boost HERA’s collecting area by about 50 percent! The HERA team will also make modification to the telescope’s instrumentation, allowing scientists to look even further back in time to before there were galaxies. With the money and upgrades, HERA will be able to provide some clues about the first objects identities, and how the objects affected their environment in the universe. The H in HERA stands for hydrogen; the instrument’s antennas are tuned to detect a wavelength of light that is emitted by hydrogen atoms which is known as the “21-centimeter line”  (referring to the size of the wavelength — 21 centimeters). The 21 centimeter line, or hydrogen line, refers to the electromagnetic radiation spectral line that is created by changes in energy states of neutral hydrogen atoms; this is why HERA is a radio telescope, and why it is located on the ground. Below is an image of the construction of HERA.


This article supported and coincided with what we have discussed over the past few class periods. For example, we did a lecture tutorial entitled Telescopes and Earth’s Atmosphere, which had a figure that we had to look at and answer questions on. The figure (pictured below) showed different wavelengths of light that are able to penetrate Earth’s atmosphere.

IMG_3114.JPG As depicted in the figure, and as discussed in the lecture tutorial and in class, we know that radio waves are able to penetrate the atmosphere and make it down to Earth’s surface. Therefore, the fact that HERA is a radio telescope and is located on the ground makes complete sense.

All in all, I thought that this article was interesting. I did not necessarily enjoy it, nor hate it, but it definitely coincided with our discussion. Before learning about this conceptual objective, I honestly didn’t ever think about the fact that the location of a telescope really mattered, let alone that there were different types of telescopes. This article helped illustrate what the lecture tutorial and some of class discussion covered. In my opinion, this was one of the harder conceptual objectives we have covered thus far; however, it was also one of the more interesting objectives that we have talked about, although I was bored with it at times.





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