Can the James Webb Space Telescope really see the past? (2024)

FAQs

Can the James Webb Space Telescope really see the past? ›

The cosmic dark ages wouldn't end until a few hundred million years later, when the first stars and galaxies began to form. The James Webb Space Telescope was not designed to observe as far back as the Big Bang, but instead to see the period when the first objects in the universe began to form and emit light.

How far back will Webb see? Webb is able to see what the universe looked like around a quarter of a billion years (possibly back to 100 million years) after the Big Bang, when the first stars and galaxies started to form.

Capturing more light allows Webb to see more distant, ancient objects. As described above, the telescope is peering at stars and galaxies that formed over 13 billion years ago, just a few hundred million years after the Big Bang.

Light travels at a constant speed (3×10⁸ meters per second). So, the farther away an object is, the longer it takes for the light to reach us. By the time the light reaches us from very distant stars, the light we are looking at can be billions of years old. Thus, we are looking at events that happened in the past.

Because light takes time to travel from one place to another, we see objects not as they are now but as they were at the time when they released the light that has traveled across the universe to us. Astronomers can therefore look farther back through time by studying progressively more-distant objects.

Webb is a powerful time machine with infrared vision that is peering back over 13.5 billion years to see the first stars and galaxies forming out of the darkness of the early universe.

Using its infrared-sensing instruments, the telescope can peer past dusty regions of space to study light that was emitted more than 13 billion years ago by the most ancient stars and galaxies in the universe.

We know that light takes time to travel, so that if we observe an object that is 13 billion light years away, then that light has been traveling towards us for 13 billion years. Essentially, we are seeing that object as it appeared 13 billion years ago.

Up until the discovery of JADES-GS-z13-0 in 2022 by the James Webb Space Telescope, GN-z11 was the oldest and most distant known galaxy yet identified in the observable universe, having a spectroscopic redshift of z = 10.957, which corresponds to a proper distance of approximately 32 billion light-years (9.8 billion ...

We do not know the exact age of the universe, but we believe that it is around 13 billion years - give or take a few billion. Astronomers estimate the age of the universe in two ways: (a) by looking for the oldest stars; and (b) by measuring the rate of expansion of the universe and extrapolating back to the Big Bang.

How far into the past can we see? ›

We can see light from 13.8 billion years ago, although it is not star light – there were no stars then. The furthest light we can see is the cosmic microwave background (CMB), which is the light left over from the Big Bang, forming at just 380,000 years after our cosmic birth.

If there were intelligent beings 65 million light years away with advanced telescopes, they might be able to observe the dinosaurs on Earth. However, this is highly unlikely as the light from the dinosaurs would have dissipated over such a vast distance, making them nearly impossible to detect.

A light-year (ly) is the distance that light can travel in one year. In one year, light travels about 5,880,000,000,000 miles or 9,460,000,000,000 kilometers. So, this distance is 1 light-year.

That's because over time, space has been expanding, so the distant objects that gave off that light 13.8 billion years ago have since moved even farther away from us. Today, those distant objects are a bit more than 46 billion light years away.

Stars are like your very own sparkly, astronomical time machine, taking you back thousands of years. All of the stars you can see with the unaided eye lie within about 4,000 light-years of us. So, at most, you are seeing stars as they appeared 4,000 years ago.

So far, what we can say with confidence is that travelling into the future is achievable, but travelling into the past is either wildly difficult or absolutely impossible.

James Webb Space Telescope can see back to 0.3 billion years when the first stars begin to appear. Between 0.3 and 1 billion years old, the first galaxies are forming. The Hubble Space Telescope can see back roughly 1 billion years.

Webb primarily observes infrared light, which can sometimes be felt as heat. Because the telescope observes the very faint infrared signals of very distant objects, it needs to be shielded from any bright, hot sources.

The universe began 13.8 billion years ago, and in its early years, it looked completely different than it does now. For nearly 400,000 years, the entire cosmos was opaque, which means we have no direct observations of anything that happened during that time.