The role of telescopes in expanding our knowledge of space
4 March 2023
Telescopes in space are more expensive than observatories on Earth. They are also getting better quickly. In nine years, the European Extremely Large Telescope will be able to take images that are 16 times sharper than those taken by the Hubble space telescope. However, the groundbreaking discoveries made by Hubble have shown us how valuable space telescopes are, despite the fact that it may appear difficult to justify investing in them.
From aurora flashes on planets and moons in our solar system to the evolution of galaxies billions of light years away, Hubble, the world’s first space-based optical observatory, has made amazing discoveries in all areas of astronomy.
In a Nobel Prize-winning study, Hubble observations contributed to determining the universe’s rate of expansion. Supernovae and star births in nurseries like the Eagle Nebula have been observed. A powerful jet emerging from a black hole at the center of another galaxy has also been captured by Hubble.
The cost of these discoveries is high. When the Hubble mission was first launched in 1990, it cost $1.5 billion, and maintenance costs have also been extremely high. Hubble’s eagerly anticipated initial images were disappointingly blurry. The telescope’s 2.4-meter-diameter mirror had a small flaw, preventing the light from properly focusing. The objective of the initial Hubble servicing mission, which was carried out in 1993 by astronauts aboard the space shuttle over five days of spacewalks, was to install an optics system to fix this issue. From 1997 to 2009, there were four additional servicing missions to upgrade and replace scientific instruments, power, and guidance systems. Each mission came with risks and costs. There hasn’t been a way to do any more maintenance on the Space Shuttle since the program ended.
Space telescopes are still prohibitively expensive. The James Webb telescope, which will replace Hubble, has been plagued by numerous delays and rising costs. It will have cost approximately $8 billion to build, launch, and commission as it gets ready for launch in 2018.
Earth versus space Building on the ground allows for much larger telescopes than can be carried into space, which is a significant advantage. Amazing discoveries have also been made by telescopes on our own planet, like the Gemini telescope’s observation of Jupiter’s two enormous red spots passing each other in the southern hemisphere. A planet orbiting another star’s atmosphere has been found to contain water vapor, according to the Keck Observatory. To learn more about how stars form and interact with the black hole at the center of our galaxy, the telescopes at the European Southern Observatory followed the stars as they travelled around it.
Ground-based telescopes, on the other hand, aren’t cheap either. The European Extremely Large Telescope, which is situated in the Atacama Desert in Chile, has already begun construction. It is expected to cost more than €1 billion and has annual operating costs of €50 million. However, this is still less than James Webb and Hubble.
The most up-to-date atmospheric distortion correction will enable E-ELT to produce images 16 times sharper than Hubble’s when it begins observations in 2024. Future space-based telescopes may appear to be difficult to justify given these technological advancements.
But the simple fact is that if we only look at things from the ground, we will miss a lot of astronomical phenomena and potential discoveries. Gamma ray bursts, for example, are among these, as are some of the most energetic events in the universe.
This is primarily due to the fact that space telescopes are not hindered by our planet’s atmosphere. The atmosphere reflects visible light, which is what our eyes are sensitive to, but it also reflects some other wavelengths of light, so we can’t see it from the ground. Additionally, the light that travels through the atmosphere is blurred by turbulent motion, resulting in the twinkling and fuzzy appearance of objects. Ground-based telescopes are subject to local weather conditions, and high clouds can prevent them from making any useful observations. This is another issue with ground-based telescopes.
Hubble is able to avoid these effects and produce high-resolution images across a wide spectrum from its elevated position above the atmosphere. The fact that scientists applied for Hubble observation time last year were five times oversubscribed demonstrates the scientific value of these observations. Additionally, it has been a significant source of scientific papers. The European Southern Observatory conducted a survey last year and found that since 2005, Hubble has produced between 650 and 850 papers annually, significantly more than any of ESO’s ground-based telescopes.
Complementary contributions The investment in astronomical telescopes—whether in space or on the ground—needs to be justified by the scientific return. When choosing new facilities, the decision is fundamentally driven by science. I think science ultimately needs both, having worked with telescopes both on Earth and in space. But we can’t have it all in a world with limited resources. So, whether it’s putting a new telescope in another country or providing an instrument for a space mission led by another agency, international cooperation is the key.
The scientific understanding of the near and far universe as well as the inspiration that these images and discoveries provide are two ways that the observations made by ground- and space-based telescopes are valuable.