Hubble Space Telescope

The Hubble Space Telescope is a space-based telescope designed to observe different regions of the universe from orbit outside Earth’s atmosphere. It has made significant contributions to observations in the fields of astronomy and astrophysics.

Hubble Space Telescope, February 1997 (NASA)

History

The concept of the Hubble Space Telescope dates back to the early 20th century. In 1923, German scientist Hermann Oberth proposed the idea of placing a telescope in space. However, this idea was deferred until the 1970s when it was seriously considered by NASA and the European Space Agency (ESA). The telescope is named after American astronomer Edwin Hubble, who provided key evidence for the expansion of the universe by discovering that galaxies are moving away from each other.

By being positioned outside Earth’s atmosphere, the telescope gains many advantages over ground-based telescopes. It produces images free from atmospheric distortions such as blurring and noise, and it is the only way to observe ultraviolet light blocked by the ozone layer.

Since its launch in 1990, it has become one of the most important instruments in the history of astronomy. It has greatly aided astronomers in solving fundamental problems in astrophysics. The image known as the Hubble Ultra Deep Field is the most detailed view ever captured in visible light from the farthest distances observed to date.

Hubble Ultra Deep Field (ESA)

Completing 15 orbits per day, the telescope circles Earth approximately every 95 minutes. The observatory moves at a speed of about five miles per second (8 km/s), fast enough to traverse USA in roughly 10 minutes. While in orbit, its primary mirror collects light from nearby and distant objects. Its primary mirror, approximately eight feet (2.4 meters) in diameter, is smaller than those of many professional ground-based observatories. What makes Hubble so powerful is its position above Earth’s atmosphere, which provides an unobstructed view of the universe and allows it to detect wavelengths blocked or partially filtered by the atmosphere. Hubble can resolve objects 1,000 times better than the human eye. This is roughly equivalent to seeing two fireflies separated by about 10 feet (3 meters) from a distance of 7,000 miles (11,000 kilometers) between New York City and Tokyo.

Design

The Hubble Space Telescope was the first space-based observatory specifically designed to be serviced while in orbit. Its sensitive optical design enables it to detect objects a billion times fainter than what the human eye can see — capable of distinguishing two fireflies separated by 10 feet from a distance of 7,000 miles. Its gyroscopes are so precise that they could hold a laser steady on the head of a president 200 miles away for 24 hours. Its fine guidance sensors are so accurate that while the telescope orbits Earth at over 17,000 miles per hour (27,000 kph), it can keep a laser locked onto a single human hair one mile away for up to 24 hours.

The Hubble Space Telescope is positioned in low Earth orbit at an altitude of approximately 547 kilometers above Earth’s surface. This altitude allows it to capture sharp images without atmospheric distortion. Key features of the telescope include:

• Mirror Diameter: 2.4 meters
• Weight: 11,110 kilograms
• Power Source: Solar panels
• Imaging Instruments: Various instruments including the Wide Field Camera 3 (WFC3), the Near Infrared Camera and Multi-Object Spectrometer (NICMOS), and the Cosmic Origins Spectrograph (COS).

Hubble is capable of observing in the ultraviolet, visible, and near-infrared regions of the electromagnetic spectrum. This capability allows scientists to study the universe across multiple wavelengths.

Hubble’s decade-long imaging of outer solar system planets (NASA)

Applications

• Galaxies and the Expansion of the Universe: Hubble has measured the rate of the universe’s expansion by observing the motion of distant galaxies. These studies provided evidence for the existence of dark energy.
• Black Holes: Hubble confirmed the presence of supermassive black holes at the centers of galaxies and studied their surrounding effects.
• Star Formation Regions: The telescope has captured detailed images of nebulae where stars are born. The iconic image of the “Pillars of Creation” in the Eagle Nebula is among Hubble’s most famous photographs.
• Planets and Exoplanets: Hubble has analyzed the atmospheres of planets in the Sun System and contributed to the discovery of exoplanets.
• Cosmic Distance Measurements: Hubble used Cepheid variable stars to measure distances between galaxies and estimated the age of the universe.

Contributions to Science

The Hubble Space Telescope has been a turning point in the history of astronomy. The data it has collected have served as the basis for more than 18,000 scientific papers. The telescope calculated the age of the universe to be approximately 13.8 billion years and has led research into mysterious concepts such as dark energy. Additionally, Hubble’s stunning images have increased public interest in astronomy and sparked widespread curiosity about science.

^{Evolution of Saturn’s rings as observed by the Hubble Space Telescope between 2018 and 2024} (NASA)