How Small Are We In The Scale Of The Universe
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The Hubble Telescope’s Risky Endeavor
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.
Understanding the Scale 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.
The eXtreme Deep Field Image
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.
What We Learn from the Deep Field Images
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.
Discussion Questions
- What was the risk involved in directing the Hubble Telescope towards the dark area near the Big Dipper?
- How did the Hubble Telescope capture such a spectacular image of over 1,500 distinct galaxies?
- Can you imagine the scale of the universe by comparing the size of a ballpoint pen at arm’s length to the night sky?
- How does the number of galaxies captured in the Deep Field image compare to the size of the entire universe?
- What is the significance of the XDF image and how does it differ from the Deep Field image?
- What does the Deep Field image allow scientists to observe about the ancient universe?
- Why is it surprising that images taken at different spots in the sky look similar in the Deep Field images?
- How does contemplating the enormity of the universe make you feel and what thoughts does it provoke?
Lesson Vocabulary
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.
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- Categories: Earth & Space Science, TED Ed, Video Lessons
- Keywords: deep field, endeavor, galaxies, Hubble, image, risky, scale, telescope, universe, xdf
