Some people have wondered if there is a telescope that can see the future. The short answer to this is no. So far, there hasn’t been a telescope that can go that far ahead. We can only see the universe as it was, in the developing stage, and as it is now.
Others also wonder if telescopes are really looking and going back into the past. Technically speaking, that’s not what telescopes do. So how far can a telescope see? This depends on several factors, particularly whether the telescope is space-based or ground-based (on earth).
In this article, we’ll explore different types of telescopes, their usefulness, and their limitations.
How Do Telescopes Work?
Telescopes are not time machines. They work by receiving an undisturbed beam of light that has traveled from past time and has appeared in the universe presently. By studying this light, they can predict what galaxy it came from. The same goes for the distant stars it has been able to capture.
Let’s say you had an injury that scared your right knee when you were young. When you look at that scar twenty years later, you’re actually not going back in time. You’re looking at the scar presently to explain what happened in the past.
It is almost impossible to tell how far any telescope can see, but it is quite obvious that space-based telescopes will have more advantages when it comes to viewing our universe.
You will soon find out that telescopes can also perform incredible functions and discoveries that have shaken the field of science, though a cheap store-bought telescope will not be able to see into space the same way as a professional one.
How Far Do Ground Telescopes See?
Here are some notable ground telescopes and their range of use:
The Southern African Large Telescope (SALT)
This telescope weighs 4,500 kg. Located in Sutherland, it made its first observation in 2005.
SALT is an optical telescope that increases the brightness and size of distant angular objects. It’s designed primarily for spectroscopy (the study of how light is emitted and absorbed) and is the largest in the Southern hemisphere.
It is made up of ninety-one hexagonally shaped mirror segments with each a meter in diameter. Its mirror measures 36.4 ft by 32.2 ft. It has up to 70% of the visible sky to access because of the mirror’s altitude design.
SALT can see miles into space and can detect ten billion times the faintest star the human eye has seen. Some of its discoveries include:
- A cosmic explosion more powerful than the average supernova. It has been tagged as one of the mightiest outbursts in history
- A binary star system (two stars orbiting each other) in an hourglass nebula which had been captured by the HST on January 18th, 1996
- The rotation of one of the largest spiral galaxies, spinning up to 570 km per second
- The first white dwarf pulsar
Gran Telescopio Canarias (GTC)
Located in Roque de Los Muchachos, Gran Telescopio Canarias (GTC) has a mirror with a diameter of 34.1 ft (10.4 m). The single primary mirror is made up of 36 hexagonal pieces that can be easily separated from each other and alter the shape of each piece.
It is also made up of a secondary and tertiary mirror that works hand in hand with the primary mirror and can be found on a large mechanical steel part called the telescope mount.
The biggest ground-based optical telescope took seven years to complete and cost €130 million. Although bad weather conditions delayed its installation, it finally saw light in 2007 and two years after, scientific observations began.
GTC can observe the nature of black holes, the history of distant galaxies, how stars were born and developed, dark matter, etc. It was built to detect infrared and optical light ranges.
Its visibility capabilities are over 4 million times better than human vision. Plus, GTC’s large size and scientific advancements in its production allow it to see better and farther than any other ground-based optical telescope.
GTC’s notable discoveries include:
- The farthest black hole that belonged to an exceptional family of the galaxy
- A faint halo of stars which is about 500 million light-years away from the galaxy UGC0180
- A small galaxy cluster forming in the early universe
- The deepest image of a galaxy from the Earth
Limitations to Ground-Based Telescopes
- They are limited by atmospheric turbulence
- Most optical telescopes cannot view satellites in the daytime
- They can only see visible light-view
- They are limited by clouds over Earth’s atmosphere .
- Weather can also be a barrier
How Far Do Space Telescopes See?
Some well-known space telescopes include:
The Hubble Space Telescope
This powerful telescope weighs equivalent to two mature elephants (about 24,500 pounds), and has the length of a typical school bus. The Hubble space telescope (HST) is powered by solar and it captures objects in space. It can travel five miles per second, which is incredible.
It makes use of Wide Field Camera 3 as its main camera, and this can see three different types of light (near-ultraviolet, near-infrared and visible light) one after the other, two of which the human eyes cannot see (near-ultraviolet and near-infrared).
The part that collects the light is the primary mirror. This light is then sent off to the secondary mirror. The primary mirror can collect more light than the human eyes can (over 40,000) and they are focused back through a hole by the secondary mirror.
The mirror is very sensitive to temperature change so it needs thermal protection and must be within a restricted temperature range to perform properly, while the spectrograph reads ultraviolet light among other functions.
How Far Can the HST See?
The furthest the HST has observed is the faraway galaxy GN-z11 about 13.4 billion light-years. It is possible to see GN-z11 again because of the expansion of the universe but this will be in 32 billion light-years.
The HST has also seen one of the brightest stars 28 billion light-years away. Named Earendel, it is said to have been about 500 times bigger than our sun and is the farthest any star has ever been detected, about 900 million years after the big bang happened.
Who Is It Named After?
This telescope is named after Edwin P. Hubble, an American astronomer. He was born in Missouri in 1889 and began studying astronomy after practicing law for a year. His classification scheme is still used today and his works led to the big bang theory after he was able to point out that the galaxy showing the solar system was one of many and that the universe was expanding. This led to Hubble’s law.
The Hubble space telescope was launched into orbit via a space shuttle on the 24th of April, 1990 and it’s still in space orbiting 547 km above the Earth, traveling 8km every second. It orbits the earth every 97 minutes.
The discoveries by this space telescope have not just revolutionized the field of astronomy but science as a whole. They showed us how little we knew about space and how much there is to find out. These discoveries include:
- Hydra and Nix, the two moons of Pluto
- In 1995, over 1,500 galaxies the size of a grain of rice were found by astronomers
- The age of the universe was made known through the HST (13.8 billion years)
- A 3-D map of the dark matter
- Hubble showed that disks of dust and gas are all around many young stars
- The rate at which the universe was expanding
- The comet Shoemaker-Levy 9 which collided with Jupiter in 1994
- Every galaxy is anchored by black holes at the center
Limitations of The Hubble Space Telescope
Since its launch into space, Hubble has discovered millions of distant galaxies, planet formation, distant objects, dust clouds, how old the universe is, etc. But despite these incredible discoveries, it has its limitations:
- It is very difficult to maintain and service due to its location
- Hubble can’t observe the sun because it’s too sensitive to heat and light. For this reason, it is pointed away from the sun and cannot observe certain stars, Mercury, or Venus.
- It can’t observe the Earth
- It can be very hard to operate
The James Webb Space Telescope
On the 25th of December, 2021, the James Webb Space Telescope was launched. It was planned for over ten years and has been expected for twenty years. Many believed that it was named after James E. Webb, who ran the space agency from 1961 to 1968.
JWST is NASA’s largest and most powerful space telescope. It weighs 6,500 kg (14,300 lbs). The Webb telescope is 43.5 feet long (13.2 m) and its diameter is 14 feet (4.2 m). It began service in February 2022.
JWST is sensitive to infrared light and can sight the heat of an insect from the distance of the moon. It is expected to discover the history of the universe, from when the big bang happened and beyond.
This $10 billion space telescope will also be able to spot the earliest stars, both nearby galaxies, and distant ones. The images and videos obtained from it will be more than ten times closer and clearer than its predecessors.
To capture very small details, the JWST has a primary mirror of 21.3 ft (6.5 m), the largest to have ever been launched in space. It is hexagonal, and its ability to fold made it possible for it to fit in a rocket. Light is collected in the primary mirror and then into the secondary mirror, which then focuses the light on the instrument of the telescope via a hole.
How Far Can JWST See?
JWST can see as far back as 13 billion years, after the big bang, when galaxies just started developing and when the first stars were being formed. It will be able to detect other planets as well as planets in our solar system.
This is an infrared telescope that can view the universe in a longer wavelength of infrared light. It will be able to see distant individual galaxies because the continuous expansion of the universe causes light from far objects to stretch out, a phenomenon known as redshift, which pushes the light out of visible range into the infrared.
One limitation that has been pointed out about this telescope is how far it is from the Earth, making it difficult to repair and maintain.
How Are Space Telescopes Different From Ground-Based Telescopes?
- Objects may appear fuzzy in ground-based telescopes because of the turbulence in the atmosphere which blurs light traveling through
- Ground-based telescopes are cheaper and easier to build and maintain
- Ground-based models cannot detect wavelengths and frequencies like the space telescope
- Ground-based telescopes can be built bigger and can gather more visible light
- Space-based telescopes have a better and clearer view of the universe
- Space telescopes can easily become out of date because of the difficulty to update their instruments
- Space telescopes can see more types of light than ground-based telescopes
- Despite their high price, space-based telescopes still have some limitations
What Is the Difference Between Wavelengths and Light-Year?
These two terms can be easily mixed up. These simple definitions will help you understand what they mean and why it is useful when observing space.
A light-year is a unit used to express the length of astronomical distances which is equivalent to about 5.88 trillion miles (9.5 trillion km). To determine this, multiply the number of seconds in a year by the number of kilometers or miles light travels in a year. In other words, it is the distance light travels in one year. A light-year is equivalent to six trillion miles.
Wavelength indicates the distance between one crest or trough of a wave to the other. The human eye can see light with a wavelength between 400-and 800 nanometers. Light waves exist in space, they are quite different from other types of waves and they don’t grow smaller with distance.
We hope this guide has helped you learn more about how far a telescope sees.
Telescopes, whether space-based or ground-based, have completely changed the way we view our universe, giving us clarity about our solar system, stars, and planets beyond the one we live in.
Astronomers find that these two types of telescopes are best-used hand in hand to compensate for wherever the other lacks.
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