How Far Can The Most Powerful Telescope See?

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Humans are born to explore. From the earliest steps of our primitive ancestors in the African plains, we’ve always endeavored to explore the world around us. This curiosity is also what drives our motives to explore space. Space has always fascinated us, “the final frontier” as we often call it. If the universe intrigues you and star-gazing is your thing, check out these amazing telescopes to help you explore space like never before.

On the front lines of space exploration is NASA’s Hubble, the world’s most powerful telescope. The Hubble has helped us explore the cosmos which are 10 to 15 billion light years from Earth. We have put these gargantuan distances of the cosmic scale into perspective, in this article.

Intergalactic Distances- What Is A Light Year?

How far can the Hubble telescope see? To get an idea, we first need to understand the concept of light years. Although it sounds counterintuitive, a light year is actually a unit of measurement of distance.

It is basically the distance traveled by light in a 1 year time span. The speed of light, denoted as c, is approximately 186,000 mi/s. According to special relativity, the speed of light is the upper limit of speed at which conventional matter or information can travel. 

To give you an idea of how fast light actually is, light can travel 7 times around the earth in just a second. In a year, light travels approximately 5.88 trillion miles! The Hubble’s XDF (eXtreme Deep Field) project captured images of galaxies 13.2 billion light years away. Just to put that number into perspective, 13.2 billion light years is 77,616,000,000,000,000,000,000 miles. 

That’s 77,616 followed by 18 zeros! But how does the Hubble telescope manage to capture such detailed images of galaxies billions of light years away? Let’s find out.

The Hubble Telescope

The Hubble Telescope is one of the largest and most versatile space telescopes. The telescope is one of NASA’s Great Observatories and was launched into orbit in 1990. Almost 30 years since its launch, the Hubble is still one of the greatest tools we have when it comes to deep space exploration. It has released some of the most awe-inspiring images humanity has ever witnessed.

The Hubble’s location in space, approximately 336 miles up, gives it an enormous advantage over ground-based telescopes. This is because the Earth’s atmosphere tends to distort and block the path of incoming light. The Hubble’s optics are designed to capture a wide range of the light spectrum from ultraviolet light and visible light to near-infrared light. 

Hubble’s light-gathering power is simply mind-blowing. Its ability to capture an enormous amount of light allows you to view the faintest, most distant celestial bodies with ease. Its 7.9-foot mirror enables it to obtain a diffraction-limited resolution of 0.05 arcseconds. This gives it the sharpest and most detailed views of the distant universe. 

Without the Earth’s atmosphere or rotation to contend with, the Hubble can simply point at an interesting spot in space to make an observation. These observations can then be superimposed to produce a deep, long-exposure image. Using this technique the Hubble can explore the farthest galaxies of the universe.

Exploring Deep Space: A Peek Into The Past

The Hubble has captured the farthest view of the Universe yet. The XDF, eXtreme Deep Field, is a picture that combines 10 years of Hubble’s telescopic views of a patch of sky, revealing galaxies we never knew existed. Only the light accumulated over so many observations can reveal such distant galaxies. Some of these galaxies are so faint, they are only one ten-billionth of the brightness that the human eye can perceive.

When looking at such distant galaxies we not only get to look deeper into space but also peek into its past. According to NASA, the XDF is a “time tunnel into the distant past”. When we look at distant galaxies, we see what they looked like when the universe was much younger.

Back to the concept of light-years, when we describe an object as 1 light year away, it basically means the light emitted by it takes exactly 1 year to reach us. Some of the most distant galaxies viewed by the Hubble are 13.2 billion light years away. Meaning, the light emitted by these galaxies 13.2 billion years ago is only now being captured by Hubble’s cameras. 

The universe is estimated to be 13.8 billion years old. Some of the youngest galaxies captured by the Hubble formed only 450 million years after the Big Bang giving birth to the universe. The farthest of them is GN-z11. The discovery of this galaxy has led to many questions, considering the galaxy is forming stars at a rate 20 times greater than what the Milky Way does today. 

This questions pre-existing theories and notions regarding the early universe. Astrophysicists had earlier speculated that such massive galaxies should not have existed so early in the universe’s history. The discovery of GN-z11 shows that our knowledge of the universe is still very limited.

The Limits Of The Hubble Telescope And The Future Of Deep Space Exploration

Exploring deep space can help us understand how young galaxies formed and functioned in the early universe. Some of these discoveries are already questioning former beliefs and theories regarding the early universe. However, we have reached the limits of the Hubble’s capabilities. 

The 7.9-foot primary mirror of the Hubble fits a certain range of wavelengths. This is fundamentally limiting. As light travels through space, the fabrics of space are constantly expanding. This expansion stretches the wavelength of light that is emitted with intrinsically short wavelengths. This phenomenon is known as redshift and it depends on the expansion rate of the universe. The redshift of a particular light source is used to accurately decipher the distance of the object. 

The Hubble’s wavelength range sets a fundamental limit to how deep into space we can see. So, how far can the most powerful telescope see? As of now the answer is around 13.2 billion light years away and just around 400 million years into the formation of the universe.

Although we have reached the limits of the Hubble’s capabilities, future observatories are likely to take us deeper into space and farther back in time than ever before. The James Webb Space Telescope (JWST) is expected to be launched in 2021. Not only is it larger, but it also operates at lower temperatures allowing it to capture longer wavelengths. NASA’s proposed flagship, WFIRST, will have 50 times the field of view of the Hubble, making it ideal for large surveys. 

Astrophysicists are constantly pushing the frontiers of what is known. With advancements in space technology, we can go deeper and further back in time than ever before, unraveling the greatest mysteries of the mind-bending universe.