In the winter of 1995, scientists directed the Hubble Telescope towards an area of the sky near the Big Dipper. This spot was dark and devoid of light pollution from surrounding stars. The location appeared empty, making the whole endeavor risky. The question was, what, if anything, would show up?
Over ten consecutive days, the telescope took nearly 150 hours of exposure of that same area. The result was nothing short of spectacular: an image of over 1,500 distinct galaxies glimmering in a tiny sliver of the universe.
To understand the scale of this image, imagine holding a ballpoint pen at arm’s length in front of the night sky, focusing on its very tip. That is what the Hubble Telescope captured in its first Deep Field image. In other words, those 3,000 galaxies were seen in just a tiny speck of the universe, approximately one two-millionth of the night sky.
To put this in perspective, consider that the average human measures about 1.7 meters. With Earth’s diameter at 12,700 kilometers, that’s nearly 7.5 million humans lined up head to toe. The Apollo 8 astronauts flew a distance of 380,000 kilometers to the moon. Our relatively small Sun has a diameter of about 1.4 million kilometers, or 110 times the Earth’s diameter.
Going a step further, the Milky Way holds somewhere between 100 to 400 billion stars, including our Sun. Each glowing dot of a galaxy captured in the Deep Field image contains billions of stars at the very least.
Almost a decade after taking the Deep Field image, scientists adjusted the optics on the Hubble Telescope and took another long exposure over a period of about four months. This time, they observed 10,000 galaxies. Half of these galaxies have since been analyzed more clearly in what’s known as the eXtreme Deep Field image, or XDF.
By combining over ten years of photographs, the XDF shows galaxies so distant that they’re only one ten-billionth the brightness that the human eye can perceive.
So, what can we learn about the universe from the Deep Field images? In a study of the universe, space and time are inextricably linked due to the finite speed of light. Therefore, the Deep Field images are like time machines to the ancient universe. They reach so far into space and time that we can observe galaxies that existed over 13 billion years ago.
This means we’re looking at the universe as it was less than a billion years after the Big Bang, and it allows scientists to research galaxies in their infancy. The Deep Field images have also shown that the universe is homogeneous. That is, images taken at different spots in the sky look similar. That’s incredible when we think about how vast the universe is. Why would we expect it to be the same across such huge distances?
On the scale of a galaxy, let alone the universe, we’re smaller than we can readily comprehend, but we do have the capacity to wonder, to question, to explore, to investigate, and to imagine. So the next time you stand gazing up at the night sky, take a moment to think about the enormity of what is beyond your vision, out in the dark spaces between the stars.
Using everyday objects, create a scale model to represent the sizes and distances of various celestial bodies mentioned in the article. For example, use a small ball to represent Earth and a larger ball for the Sun. Measure out the distances between them to scale. This activity will help you visualize the vastness of space and the relative sizes of objects within it.
Look at the Hubble Deep Field and eXtreme Deep Field images online. Choose a small section of the image and count the number of galaxies you can see. Discuss what each galaxy represents and how many stars might be in each one. This will give you an appreciation for the density and diversity of the universe.
Write a short story or create a comic strip about traveling back in time by observing light from distant galaxies. Include what you might see and learn about the early universe. This activity will help you understand how looking at distant objects in space is like looking back in time.
Using lenses and cardboard tubes, build a simple telescope. Use it to observe the night sky and try to identify constellations or planets. This hands-on activity will help you understand how telescopes work and why they are important tools for astronomers.
Conduct a research project on the history, missions, and discoveries of the Hubble Telescope. Create a presentation or a poster to share your findings with the class. This will deepen your understanding of the Hubble Telescope’s contributions to our knowledge of the universe.
hubble – referring to the Hubble Space Telescope, a space-based observatory that provides images of celestial objects – The Hubble captured stunning images of distant galaxies.
telescope – an optical instrument used to view distant objects in space by collecting and focusing light – The astronomer observed a rare comet through her telescope.
risky – involving the possibility of danger, harm, or loss – Climbing Mount Everest without proper training is a risky endeavor.
endeavor – a serious and determined effort to achieve a goal – The scientists embarked on an endeavor to find a cure for cancer.
image – a visual representation or likeness of something – The photographer captured a stunning image of a sunset over the ocean.
galaxies – large systems of stars, gas, and dust held together by gravity – The Andromeda Galaxy is one of the closest spiral galaxies to the Milky Way.
universe – all existing matter, space, and energy, including planets, stars, galaxies, and everything in between – Scientists are still unraveling the mysteries of the universe.
scale – the relative size or extent of something compared to a standard – The model of the solar system accurately depicted the planets’ sizes to scale.
deep field – an area of the sky observed for an extended period, capturing faint and distant objects – The Hubble Deep Field image revealed thousands of galaxies in a tiny patch of sky.
xdf – short for “eXtreme Deep Field,” an image created by combining Hubble observations over a long period to capture the most distant and faint objects – The Hubble XDF revealed galaxies that formed shortly after the Big Bang.
