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5 Amazing Discoveries Made Through Radio Telescopes

When it comes to telescopes, it’s more common to hear about the optical rather than radio ones. Optical telescopes work by collecting light and bouncing it towards what’s being looked at through the eyepiece. As reviewed by Telescopic Watch, Celestron is one of the leading and best optical telescopes on the market.

Radio Telescopes work differently, however. They rely on wavelengths they collet and astronomers use them to form an image of what they are trying to look at. This way, astronomers can see and understand what can’t be seen through optical telescopes and even the naked eye. This field of study is called Radio Astronomy.

Radio astronomy was actually accidentally discovered. This started in 1933 when an engineer named Karl Jansky was called by Bell- a telephone company during that time, to check on a static interference that its phone lines had. Since then, radio telescopes have been further developed and so radio astronomy became a thing. 

For the longest time, the largest radio telescope in the world was found in the Arecibo Radio Observatory in Puerto Rico. However in 2016, China has finally complete the latest largest radio telescope in the world. It amazingly covers 196,00 square meters, far from Arecibo’s area coverage of 73,000 square meters.

Since radio were developed, significant discoveries have been made. Here we list 5 amazing discoveries that were made through the use of radio telescopes.


Mercury’s Orbit

Using the radio telescope in the Arecibo Observatory in Puerto Rico, radio astronomer and planetary cist Gordon Pettengill discovered that Mercury’s rotation takes 59 days. This is contrary to what was delivered by astronomers before Pettengill’s discovery.

Astronomers used to believe that Mercury takes 88 days to fully rotate. Pettengill and fellow radio astronomer Rolf Dice bounced radar signals towards Mercury to get an accurate measure of its spin rate.



Pulsars and spinning neutron stars that produce electromagnetic waves and a bit of visible light. They have pules of radiation that are detected to happen with an interval that ranges from milliseconds to seconds. Astronomers can only observe these when they face the Earth because they can only be observed through a radio telescope.

Since they a basically neutron stars, the pulsars are remnants of giant or sun-like stars. The first pulsar was discovered in 1967 by radio astronomers Jocelyn Bell Burnell and Anthony Hewish. They named this pulsar LGM-1. As of now, there have been approx. 2000 pulsars discovered by radio astronomers.



Quasars are extremely luminous and that’s why they are also known as the brightest celestial objects. They are also the most distant celestial objects that have ever been discovered in the universe. However, Quasars were not noticed for a very long time. Because of how luminous Quasars are, they were believed to be stars in the early days of astronomy. When radio telescopes were used for astronomical studies, it was when Quasars became a point of interest because they defy studies made with the use of optical telescopes.

Discovered in 1963, the existence of Quasars are also said to be evidence of the Big Bang Theory. The first Quasars were named 3C 48 & 3c 273.


Extra Solar Planets

Extra Solar Planets, also known as Exoplanets, were first discovered in 1991. This was not really the first time Exoplanets were noticed. Before astronomers Alex Wolszczan & Dale Frail confirmed the existence of Exoplanets, this was first noted in 1917 however the then lack of technology could not confirm Exoplanets.

Exoplanets are planets that are outside of the solar system. The two astronomers who discovered the first known Exoplanets discovered them through the use of the radio telescope in the Arecibo Observatory. As of 2018, there are already approximately 2,300 confirmed Exoplanets that were discovered by different observatories around the world. 


21 CM Hydrogen Line

The 21 CM Hydrogen Line was discovered and observed by Edward Purcell & Harold Ewen in 1951 and since then radio astronomers have been mapping neutral hydrogen in the galaxy. This helps astronomers map the hydrogen in the galaxy, which eventually lead to the publishing of the spiral structure of the Milky Way.   

Studying the 21 hydrogen line helps astronomers understand the universe better since hydrogen is the most abundant element in our galaxy. Interestingly, SETI sees the hydrogen line as something very significant to the quest to find to life outside of Earth. 


Radio Astronomy Now

It has been a while since significant and game changing discoveries were made through a radio telescope. Radio astronomers are continuously providing observations with the hope to learn something new about the universe.  

With China completing the largest telescope in the world, there are a lot of positive steps taken in modern astronomy.


Kids Fun Facts Corner

# 1. Through radio telescopes and radio astronomy physicist Gordon Pettengill at the Arecibo Observatory confirmed the number of days it takes for Mercury’s rotation. (59 days)

# 2. The first pulsar ever to be discovered named LGM-1 was discovered by a radio telescope in 1967.

# 3. Quasars are detected and studied in great detail by radio telescopes.

# 4. Through radio telescope technology planets have been confirmed to exist outside of our solar system. These planets are called Exoplanets.

# 5. The 21 CM Hydrogen line was discovered by radio telescope technology.


Q&A Corner

Q. In what year was radio astronomy discovered?

Q. In what country is the Arecibo Observatory located?

Q. In what year was the first Quasar discovered using radio telescope technology?

Q. In what year were Exoplanets discovered using radio telescope technology?

Q. What nation in 2016 is in built the largest radio telescope in the world?

Download questions about radio telescopes here: radio telescopes (answers are on this page) 

For more information related to radio telescopes visit 

Key Vocabulary Radio. Telescope. Universe. Earth. Astronomers. Discoveries.