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Astronomy enthusiasts always love discovering new things about the universe, especially when answering questions surrounding time travel.
But how does peering at distant galaxies help unveil the past through a telescope?
Telescopes can “look into the past” using the light emitted from different galaxies millions of years ago. The farther away the object is, the longer it will take for its light to reach Earth. The phenomenon is also known as the “lookback time.”
For instance, when we say a galaxy is 140 million light-years away, it means that the light emitted by the galaxy traveled for 140 million years before reaching the Earth.
The beam of light appears undisturbed since it travels through a mostly-empty vacuum of space for millions of years. Thus, we can infer what the galaxy that emitted the light looked like millions of years ago by looking at the present state of the light beam.
In this article, we’ll see how astronomers and telescope enthusiasts look back in Time, which telescopes are best for this purpose, and what discoveries humans have made through this phenomenon.
Can a telescope see the past?
A telescope is not capable of looking at the past. Think of an old picture you see of yourself. When you look at the old photo, you’re looking at a past version of yourself or “looking back in time.”
However, you aren’t looking at the past. You are no longer the younger version, nor does your younger version exist in any dimension or corner of the entire universe.
So, telescopes do not look back in Time since the past no longer exists.
The light you observe through a telescope has taken Time to travel to us. The more the distance is in light years, the farther away the galaxy we observe. That means we’re just looking at something that happened in the past rather than observing events through the telescope in real time.
In some cases, like when observing a distant galaxy, the light you observe may be billions of years old. The telescope only observes light traveling through space for a long time.
So a telescope is a powerful tool that allows us to understand the wonders of the early universe, but it cannot observe the events that have already occurred in the past.
How do telescopes allow us to look back in time?
Observing the cosmos during its past epochs can be tricky since distant objects appear fainter than closer ones. But how do we know all this?
Telescopes look back in time using the principle of light travel time. Light travels at a constant speed through the vacuum, around 299,792,458 meters per second. When a telescope observes this light, we measure the distance in light years. That means the farther the celestial body is, the longer it will take for the light to reach here.
When observing distant galaxies through a telescope, we also have to consider the constant speed of light. You also have to be familiar with concepts like time dilation.
As the universe expands, distant celestial bodies are moving away from us. So, we observe these bodies as they were, not as they are now.
This phenomenon is known as the Cosmological redshift combined with the principle of light travel time to give us a glimpse of the past.
Human eyes can only view a portion of the range of radiation. The radiations are part of the electromagnetic spectrum, and the part we can see is “visible light.”
Thus, we miss out on important information depicted by other radiation types.
The electromagnetic spectrum shows vital information when observing the cosmos, galaxies, and celestial bodies. That is where a telescope helps capture critical information.
For instance, the Hubble Space Telescope detects a range of ultraviolet and infrared wavelengths and visible light.
You may also like to read more about Why Observatories Are Built on Mountain Tops.
Let’s look at some factors that allow telescopes to look back in time.
Capturing light from distant objects
Light travels at a constant speed, but the light emitted by space objects is significantly away. Thus, it takes a long time for that light to reach us. By using a telescope, we can gather and focus the light, allowing us to observe distant objects in space.
Telescopes concentrate the light using a combination of mirrors and lenses. The primary mirror or lens is an essential element of the telescope. Only telescopes capable of detecting infrared light can see far-away galaxies.
The captured light from distant objects is refracted or reflected by a smaller lens or mirror called the eyepiece, which magnifies the image for the observer.
A refractor telescope like the Observer 90mm Equatorial Refractor Telescope is a great option for observing faint sky objects, such as distant galaxies and nebulas. It’s considered a medium-sized telescope that’s ideal for advanced novice astronomers.
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You may also like to read more about how to Increase the Magnification of a Telescope.
Studying distant objects to learn about the universe in the past
Studying distant objects helps us learn about past galaxies’ formation and evolution. For instance, scientists estimated that the universe is about 13.8 billion years old.
Scientists reached this conclusion by observing galaxies, their composition, brightness, and size. We can also learn more about stars, their formation, and evolution by looking at their past.
Studying light emitted from these stars helps us to determine their brightness, temperature, and composition.
Beginner astronomy enthusiasts can start their stargazing journey by studying objects in the sky using a home telescope like the Sky-Watcher Pro ED 80mm Doublet APO Refractor Telescope, the all-rounder Celestron NexStar 8SE Telescope, or the Orion 6 Inch f/4 Newtonian Astrograph Reflector Telescope.
Using advanced technology to overcome limitations of viewing distant objects
Telescopes with larger lenses can gather more light and depict clearer images of distant objects. With technological advancement, telescopes now also come with adaptive optics that correct the distortion caused by the Earth’s atmosphere.
Interferometry is another technique that combines signals to produce images with a finer resolution. This can be done through a technique called “Very Long Baseline Interferometry” or by connecting the telescopes physically.
Telescopes with larger lenses, like the Celestron PowerSeeker, are a great option for viewing distant objects. Although you might not be able to view far-away galaxies from your home. Click here to purchase this amazing telescope on Amazon.
Studying spectra of distant objects
Studying spectra is a sophisticated form of study. Spectra is a type of electromagnetic radiation divided into its component wavelengths.
This type of study is known as spectroscopy. The spectral lines help determine the element, the element’s density, the temperature, and the object’s chemical composition. Scientists use this technique to study distant stars and galaxies.
If you’re looking for a competent telescope for studying stars, check out the Celestron Astromaster telescopes that come with coated glass to give a crisp and clear image of the stars.
It’s a must-have telescope for stargazing enthusiasts looking for a home telescope.
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Studying redshift of distant objects
Redshifts help astronomers measure how the universe expands and how much the wavelength of the emitted light increases due to the expansion. Scientists connect the redshift to the Doppler Effect and measure it using spectroscopy.
The redshift helps determine the distance and velocity of distant galaxies, celestial objects, and quasars and also helps measure the amount of dark matter in the universe.
Observing Cosmic Microwave Background radiation
Most of us have heard about the Big Bang and how it changed the course of the entire universe. The cosmic microwave background (CMB) is leftover radiation from the Big Bang.
You cannot observe the CMB directly, but it’s everywhere in the universe. You need specialized instruments like the Atacama Cosmology Telescope to detect faint microwaves for observing CMB radiation.
Using gravitational lensing effect
A gravitational lens occurs when a massive amount of matter creates a gravitational field that magnifies and distorts the light from distant galaxies in the same line of sight.
So, the gravitational lensing effect distorts the image of a background galaxy while amplifying its light. Another popular application for this effect is the study of dark matter. It can also be used to study the universe’s properties, the distribution of matter, and the universe’s curvature.
Using time-domain astronomy
Time-domain astronomy is the study of how celestial bodies change with Time. It studies phenomena like pulsar variability, explosive events such as the flaring of galaxies, and the variability of stars.
You can also use time-domain astronomy to study transients, which are short-timed astronomical events like gravitational wave events, gamma-ray bursts, and supernovae. Telescopes are used to observe the same sky patch at different times repeatedly.
What telescopes can observe distant objects and study the distant past?
Telescopes like the Spitzer Space Telescope and the Hubble Space Telescope have allowed scientists to unveil different galaxies and nebulas far away in the cosmos and our solar system.
The James Webb Space Telescope
The James Webb Space Telescope is the most powerful telescope ever created that will allow us to observe our universe more closely. It launched in 2021 and is the largest infrared telescope ever used.
It can observe distant and early galaxies and stars that formed right after the Big Bang.
The Euclid Space Telescope
The Euclid Space Telescope is developed to explore the evolution of the dark universe. Dark energy and dark matter are strongly related to the universe’s expansion and govern the growth of cosmic structures.
However, scientists are still determining what dark matter is. Euclid will help determine how the universe expanded and formed over cosmic history. It’ll be able to measure the redshifts of galaxies too.
The Large Synoptic Survey Telescope
The LSST is a ground-based observatory that began its operations in early 2020. LSST will use weak gravitational lensing to study the properties of galaxy clusters and the distribution of dark matter.
Moreover, the LSST will also be able to study the properties of the solar system, transient objects like supernovae, and the Milky Way.
The WFIRST Space Telescope
The Wide Infrared Survey Telescope (WFIRST) is a space-based observatory launched in mid-2020. It aims to study the properties of exoplanets and dark energy.
It employs microlensing to detect and study exoplanets that are too far away to be detected by other methods.
What discoveries were made by looking back in Time?
Looking back in Time has led to several important discoveries in cosmology and astronomy. We now know how the galaxies emerged from the “dark ages” shortly after the Big Bang and how the first stars reheated the cold and dark universe.
Discoveries like the Cosmic Microwave Background, the accelerating expansion of the universe, the first galaxies, distant quasars, and the cosmic web are some discoveries we’ve made by looking back in time.
Let’s discuss some of the most potent discoveries ever made in astronomy and cosmology.
The discovery of the oldest galaxy
The James Webb Space Telescope discovered the oldest galaxies when the universe was only 350 million years old. Astronomers know that the light from these galaxies took more than 13.4 billion years to reach Webb Space, so the galaxies must have started to form much earlier.
These are followed by the GN-z11, a galaxy discovered in 2016 when the universe was just 400 million years ago. This is followed by the EGS-zs8-1, a galaxy discovered in 2015 located 13.2 billion light years away.
The discovery of the first stars
The first stars formed when the universe was only 100 million years old. These massive stars ended their lives as supernovae and seeded interstellar space with heavy elements.
The earliest range of stars, known as the Population III stars, are thought to form in the period of reionization. The oldest known star, SMSS J031300.36-670839.3, was found in 2016 and is estimated to be about 13.6 billion years old.
The discovery of the most distant supernova
A supernova detected at a distance of 10.5 billion light-years is the most distant. The massive star exploded when the universe was just a quarter of its current age.
Supernovas are very luminous and form when a massive star collapses on itself due to the pull of gravity.
Can a telescope see the Big Bang?
We observe galaxies and stars when their light reaches the Earth.
The Big Bang occurred 13.8 billion years ago approximately, and its light is yet to reach the Earth. You can’t see the Big Bang because light didn’t exist, and there were no such things as photons.
After the universe cooled down after 380,000 light years, proper atoms formed. This is when light could travel distances along the universe. This light is known as microwave background radiation, which is known as the afterglow of the Big Bang.
How a telescope helps unveil the universe’s secrets
Telescopes are a powerful tool that allows us to unveil secrets of the universe and study the distant past of the universe.
Using the light emitted from distant objects, we can study the properties of the early universe, like the formulation and evolution of stars, galaxies, and quasars.
