Despite being much closer to us than the nebulae, Hubble is still unable to capture clear images of this planet.
Since its launch over 30 years ago, the Hubble Space Telescope has captured stunning scenes in the depths of the universe for humanity. Distant galaxies millions of light-years away and billions of light-years old can be clearly seen through the lens of Hubble.
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The Hubble Space Telescope, deployed into Earth’s orbit over 30 years ago by the Space Shuttle Discovery, has captured stunning and scientifically invaluable images, revealing the accelerating expansion of the universe due to a mysterious force known as dark energy.
However, it is quite strange that while the Hubble Space Telescope can photograph galaxies hundreds of millions of light-years away, it cannot capture clear images of distant exoplanets, or even Pluto within our own Solar System.
Many people might think that the reason behind this is very complex, involving issues at the fundamental laws of the universe. However, in reality, the answer is much simpler than you might think. Hubble can photograph distant galaxies but cannot capture images of Pluto because of the difference in angular diameter (apparent size) between the two.
You may not be familiar with the term angular diameter, but it is used in astronomy to describe the size of a target celestial object. For example, the angular diameter of the Moon in our field of view is about 0.5 degrees.
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One of these images is part of a project called the ‘Hubble Legacy Field,’ which constructs high-resolution panels by pointing the Hubble Space Telescope at a specific point and then stitching them together to create a larger composite image. These images will aid scientists in further understanding both space and time.
However, when the Moon is 380,000 kilometers away from Earth and has an angular diameter of 0.5 degrees, the Andromeda galaxy, which is 2.54 million light-years away from Earth, has an angular diameter of 3 degrees, six times larger than our natural satellite. It is very far away, but its diameter extends to 220,000 light-years, so the Hubble Space Telescope can easily capture its image much more easily than that of the Moon. It can even use hundreds of exposures to eventually synthesize a one-billion-pixel image of the Andromeda galaxy.
On the other hand, the angular diameter of Pluto, at a distance of 4.8 billion kilometers, is only 0.11 arc seconds (1 degree equals 3600 arc seconds). Therefore, Pluto appears extremely tiny in the observation field of Hubble.
As a result, it was not until the New Horizons spacecraft flew by Pluto in 2015 that humans were able to obtain high-resolution images of the dwarf planet.
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The Hubble Space Telescope resides in Earth’s orbit at an altitude of approximately 610 km, which is 220 km higher than the orbit of the International Space Station (ISS). With a velocity of around 7,500 m/s, Hubble completes one orbit around Earth in approximately 97 minutes, totaling 15 orbits per day.
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The NGC 6302 planetary nebula, also known as the “Butterfly Nebula,” with its hourglass shape, formed from gas clouds heated to a temperature of 20,000 degrees Celsius in the explosion of a star five times the size of the Sun. The gas clouds expand at speeds exceeding 965,000 km/h, dispersing into space. These gas clouds have been floating in space for approximately 2,200 years, and the wingspan of the “giant butterfly” extends about 2 light-years. NGC 6302 is located within the Milky Way, approximately 3,800 light-years away from the Scorpius constellation. The Hubble image was captured on July 27, 2009.
The image taken in April 2010 portrays the peak of a chaotic mixture of dust and cosmic gas clouds, towering to a height of 3 light-years. This image was selected to commemorate the 20th anniversary of the Hubble Space Telescope’s launch into Earth’s orbit. The dim light of these clouds is overshadowed by the brighter surrounding stars, while young stars forming within the clouds emit penetrating rays of light. These gas and dust clouds are known as the Carina Nebula and are located approximately 7,500 light-years to the south of the Carina constellation.
The Horsehead Nebula, also known as Barnard 33, was captured by the Hubble Space Telescope in April 2013. In fact, the image above was taken using infrared light, which has longer wavelengths than the light visible to the human eye. Infrared light can penetrate dense layers of cosmic dust, enabling Hubble to capture the image.
In May 2013, from a distance of approximately 2,000 light-years away from Earth, the Hubble telescope captured an image of a ring-shaped nebula aptly named the Ring Nebula. The white dots observed in the image are hot white dwarf stars. White dwarfs are one of the evolutionary stages of stars in the universe, including our Sun, which will evolve into a white dwarf in about 5 billion years. The ring-shaped nebula is visually stunning, with a central bluish region and a reddish outer halo.
April 21, 2016 marked the 26th anniversary of the Hubble Space Telescope. To commemorate this significant day, NASA released breathtaking images of the Bubble Nebula captured by Hubble. The Bubble Nebula is formed by a large, hot star that generates gas and dust, which is then blown into space by powerful winds.