Top Astronomical Discoveries Made by Radio Telescopes

Image Credit: Radio Telescope by Ton Zhou
Image Credit: Radio Telescope by Ton Zhou

Aside from sending out expeditions, space exploration is made possible with the use of certain instruments; more specifically – telescopes. However, astronomers do not solely rely on optical telescopes to observe space. Some really distant objects which can’t be seen even with the most powerful optical telescopes are reached, instead, through the use of radio telescopes.

What is a Radio Telescope?

After cosmic radio emissions were first reported in 1933 by Karl Jansky, an astronomer from Wheaton in Illinois, in 1936 a radio engineer and amateur astronomer named Grote Reber built a radio telescope in his backyard in order to continue investigating the phenomena. This was then the first telescope to receive radio waves.

Radio telescopes make it possible to observe radio waves from space. It works similarly with optical telescopes, but instead of visible light, radio waves are reflected. Radio waves and microwaves also have longer wavelengths than visible light, which astronomers use to gather data such as frequency, power, and timing of radio emissions from objects. In turn, this enables them to deduce information about space that isn’t achievable with optical telescopes.

In short, radio telescopes can show us things about the universe that optical telescopes cannot and through their use astronomers can improve our understanding of the Universe. Ever since the creation of the first telescope, more and more astronomical objects have been discovered, and these telescope have continued to improve over time, as listed by Below are some of the most significant radio telescope discoveries that have paved way to more explorations.

1: Mercury’s Orbit and Venus’ Temperature

Radio telescopes helped astronomers to discover things about the planets within our solar system, specifically about Mercury’s orbit and Venus’ temperature. It was first believed that Mercury’s rotational period matches its orbital period which is 88 Earth days. However, in 1965, Gordon Pettengill and Rolf Dyce bounced radar signals off Mercury to measure the spin rate of the planet, using the then 300-meter Arecibo Radio Observatory in Puerto Rico

They subsequently discovered that its rotation rate is 59 days instead of 88, indicating that Mercury rotates three times for every two revolutions around the Sun, and its day is exactly 2/3 of its 88-day year.

Since Venus’ surface is hidden with thick atmosphere and clouds, it was a challenge for astronomers to study its features before radio telescopes. Radio telescopes work by collecting radio emissions from planets, which is why Venus’ thick cloak of clouds wasn’t much of an obstacle. Radio waves can penetrate said obstacle, thus allowing researchers to finally see Venus’ surface.

Through radio waves, astronomers have learned about the planet’s surface temperature which is now known to be about 462 °C (863 °F). Radio emissions from Venus also helped them learn about the planet’s rotation, atmosphere, and surface features.

2: First Binary Pulsar and Millisecond Pulsar

Russell Hulse and Joseph Taylor’s discovery of pulsars using radio telescopes in 1974 is the reason why they were awarded the 1993 Nobel Prize in Physics. Using a giant 1,000 foot diameter radio telescope at Arecibo in Puerto Rico, the two scientists from Princeton University discovered a binary pulsar, now called PSR1913+16, or Hulse–Taylor binary.

A binary pulsar is a pulsar in orbit with a white dwarf or neutron star nearby to balance its mass and gravitational direction. The binary pulsar that they discovered is 20,870 light years away from Earth and has a pulse period of about 59 milliseconds, which varies by about one part in 1,000 every 7.75 hours.

On the other hand, millisecond pulsars or recycled pulsars are neutron stars with a very fast rotational period. The first-millisecond pulsar was discovered in 1983 by Donald C. Backer, Miller Goss, Michael Davis, Carl Heiles, and Shrinivas Kulkarni using the Arecibo telescope. The millisecond pulsar known as PSR B1937+21 rotates with a period of 0.00155780644887275 seconds or about 642 times a second, and was the fastest pulsar known for 20 years.

3: Quasars

Radio telescopes see about 10% of the known quasars or “quasi-stellar radio source” in space. These objects emits large amounts of energy and have a star-like image in a telescope, hence, the name quasi-stellar.

Their discovery in 1963 supported the Big Bang theory while undermining the Steady State theory of the universe, since the structure of quasars is very different from the structure of the universe today. A quasars’ core and jets are visible with radio telescopes, while only the core is visible using optical telescopes.

4: First Imaging of an Asteroid

The first asteroid to be modeled by radar imaging is 4769 Castalia. It was discovered by Eleanor F. Helin when the Arecibo radar/radio telescope picked up the asteroid as it passed by Earth within 5.6 million kilometers (3.5 million miles) on August 25, 1989.

Scott Hudson and Steven J. Ostro used the detailed time-delay and Doppler data from the radio waves to produce a 3D computer model of the dumbbell-shaped Castalia. It was also the first time scientists had used technology to create an image of what the asteroid looks like.

Castalia is about 1.8 kilometers (1.1 miles) across at its widest with a mass of 0.0005 kg. Its orbit takes 1.1 years to travel around the Sun. Another close approach will occur again on Aug 26, 2046, as it gets close to us by 3,754,906.55 km.

5: Discovery of Exoplanets

On January 9, 1992, astronomers Alex Wolszczan and Dale Frail discovered exoplanets that are orbiting a pulsar named PSR 1257+12. Like most of the discoveries on this list, it happened on the Arecibo Observatory in Puerto Rico.

Exoplanets are planets that exist outside our Sun’s solar system. The discovered exoplanets are about four times as massive as our planet, and their proportions closely resemble the spacing between Mercury, Venus, and Earth.

These planets are believed to be orbiting the aforementioned pulsar located about 2,300 light-years away in the constellation Virgo. The innermost one circles it every 67 days, while the outer one circles every 98 days. There’s also a possible third planet which is farther from the pulsar and orbits it about every 360 days.

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