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Thirty years of the Hubble Space Telescope
By
Bryan Dyne
May 2, 2020
The Hubble Space Telescope recently celebrated its thirtieth year of scientific observations and remains the oldest astronomical space observatory. This will be its last decade of operation before it burns into Earth’s atmosphere, unless immediate plans are made to propel it to a higher orbit, a maneuver previously performed during service missions by the shuttle program. space now discontinued.
Astronomers took 1.4 million observations with the telescope and produced more than 17,000 peer-reviewed scientific publications. The data it has produced will fuel more research for many years after the telescope itself has stopped working.
We are republishing the article initially released for Hubble’s 25th anniversary. The text does not change while some of the images have been updated to reflect the ongoing science of the mission.
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Start the slide show
For the past 25 years, the Hubble Space Telescope has been one of the most fruitful and versatile astronomical platforms ever launched into space. For more than 9,000 days, the telescope has provided outstanding scientific data in the ultraviolet, visible, and near-infrared regions of the electromagnetic spectrum in nebulae, globular clusters, galaxies, supernovae, exoplanets, black holes, and our own solar system. For a generation, Hubble has inspired and spearheaded a new era of cosmos research.
Hubble launched on April 24, 1990 aboard the space shuttle Discovery. It was the first of NASA’s Great Observatories to launch, a constellation of four space telescopes that also includes the Gamma Compton Ray Observatory (exorbitant in 2000), the Chandra X-Ray Observatory, and the Spitzer Space Telescope. Each was designed to observe different wavelengths, complementing the others and combining their views into a larger whole. The series has been one of NASA’s most successful science programs. Every launched telescope (with the exception of Compton) remains in operation at least partially.
Six instruments are used to collect the light focused by the Hubble mirrors: Wide Field Camera 3 (WFC3), Cosmic Origins Spectrograph (COS), Advanced Camera for Surveys (ACS), the near-infrared camera, and the multi-object spectrometer ( NICMOS), the Space Telescope Imaging Spectrograph (STIS) and the Fine Guide Sensor (FGS). The data is transmitted to Earth for processing, distribution, and study.
Significantly, none of the instruments in the telescope is part of its original equipment. One of the main reasons for the launch of Hubble by the space shuttle was that instruments on board could be replaced as newer ones became available. In fact, almost everything on Hubble (scientific instruments, batteries, gyros, solar panels, computers) has been updated. Only the original mirrors and the substructure itself remain from the original launch. The last scheduled service mission was in 2009.
While a public relations boost for NASA, Hubble’s true importance lies in its continued and vast contributions to astronomy. One of his initial goals was to observe a specific class of stars known as Cepheid variables, the brightness of which can be determined, and then not measure their distance from Earth. This vastly increased the precision in measuring the rate of expansion of the universe, reducing the margin of error from fifty percent to ten percent.
A follow-up study, this time looking at supernovae in distant galaxies, found that the expansion rate of the universe is increasing, rather than decreasing as expected. Earth observations confirmed the existence of the little-known force driving the expansion, called “dark energy.” His discovery was awarded the 2011 Nobel Prize in Physics.
Hubble’s high resolution also made the first direct studies of supermassive black holes possible. These objects were first identified as radio sources in distant galaxies, but the source was unclear. Something extraordinarily powerful would have to be generating a great deal of energy to be seen billions of light-years away. After decades of work, it became clear in the 1960s that the only explanation for what astronomers were seeing was the energy emitted by a black hole accumulation disk, millions and even billions of times the mass of our Sun .
Here, the Chandra Observatory has played a key role in understanding these objects, working together with Hubble to delve deeper into the underlying physics that drives these events. It was Chandra who first discovered that the nearby Andromeda galaxy probably has two supermassive black holes instead of one. Combined efforts using Hubble, Chandra, and other telescopes have shown that supermassive black holes are common features of galactic nuclei.
Hubble also contributed substantially to our understanding of the mechanics by which giant clouds of gas and dust collapse to form new stars. His stunning portrait of the Eagle Nebula in 1995 became a popular poster and wallpaper for millions of people around the world. This image captured dense gas pillars containing even denser nuclei that became new stars, being simultaneously evaporated by the already formed bright young stars. A recent image captures movements in the past 14 years, measuring a 200-kilometer-per-second growth from an airplane associated with a young star.
Infrared images of the Eagle Nebula were taken by the Spitzer telescope in 2007 to see inside the clouds, complementing Hubble’s observations. The most striking feature revealed is the abundance of hot dust, most likely heated by a nearby supernova 8,000 to 9,000 years ago. If so, the blast wave from the explosion would have knocked down all three pillars 6,000 years ago. Since it takes 7,000 years for light to travel from the Eagle Nebula to Earth, we will see if this prediction is true within a millennium.
Perhaps the most extraordinary science performed by the observatory is deep field imaging, the first of which was the Hubble Deep Field (HDF) taken in 1995. Focusing on an area of the sky less than 100 times the size of the Moon seen From Earth, where only a handful of stars in the Milky Way can be seen, Hubble collected light for eleven days.
In that tiny region of space, Hubble revealed to astronomers and the public alike how large space is. About 3,000 different galaxies were observed in the images, each with tens of billions of stars, with spiral, irregular and elliptical galaxies all present. The study provided the first in-depth look at the early universe, seeing galaxies at a distance of up to 12 billion light-years, and therefore, since light takes time to travel through space, galaxies as they were 12 billion years. Astronomers were amazed at the number and variety of young galaxies that Hubble revealed.
These images prompted a succession of subsequent “deep field” scans, created with new generations of improved cameras aboard Hubble. In 2003-2004, the Hubble Ultra Deep Field (HUDF) was taken, focusing on 11 square arc minutes in the Fornax constellation and looking back 13 billion years to see 10,000 galaxies forming less than a billion years after the Big Bang. Hubble eXtreme Deep Field (XDF) was taken in 2012 focusing on a HUDF region. The exposure was taken over twenty-three days, collecting data on galaxies that are ten billion times weaker than the human eye can see. Some of the 5,500 newly discovered galaxies are 13.2 billion years old, the oldest ever observed in visible light. Due in part to this work, astronomers estimate that the observable universe contains 200 billion galaxies.
The first proposal to use a rocket to place a telescope in space was published by the German physicist Hermann Oberth in 1923. In his work. Die Rakete zu den Planetenräumen (“The Rocket into Planetary Space”), which was previously a doctoral thesis rejected as “utopian,” suggests that rockets could eventually lift telescopes to Earth’s orbit. His work, along with that of Robert Goddard, Konstantin Tsiolkovsky, and Oberth Wernher von Braun’s assistant, founded modern rockets and paved the way for every space telescope that has flown.
Hubble’s origins date back to 1946, when astronomer Lyman Spitzer published the document “Astronomical Advantages of an Alien Observatory”, which first presented the scientific justifications for placing an observatory above the atmosphere. Spitzer argued that if the best telescopes of the day could have been placed where there is no air, the lack of turbulence would increase the angular resolution of each at least ten times. Furthermore, they could also observe infrared and ultraviolet light, which are largely blocked by Earth’s atmosphere.
After a series of small-scale instruments designed to show that infrared and ultraviolet astronomy could be successfully done in space, NASA approved plans for a space-based 3-meter reflecting telescope in 1968. It was provisionally known as the Great Space Telescope (LST) and scheduled for launch in 1979.
Although the astronomical community fully endorsed the creation of the instrument, NASA faced obstacles to funding a recalcitrant Congress and cuts in public spending instigated by President Gerald Ford. Now that the geopolitical impetus for space exploration had disappeared, after the United States beat the Soviet Union to the moon, there was little interest in providing money for space flights, especially for missions that had no military purpose, only scientific knowledge. . Funding for the project was phased out in 1974. It was only after a Herculean effort by astronomers campaigning for the LST that funding was reinstated, and even four years later it was only half the original budget. As a result, the construction of the primary mirror and other instruments began the year the telescope was originally scheduled for launch.
Here, NASA confronted the US Army. The company in charge of building the mirror, Perkin-Elmer, was well known to the US government. USA For its development of the optics used in the Keyhole-9 HEXAGON spy satellites. Shortly after it was announced that Perkin-Elmer would produce the mirrors for LST, the US Air Force. USA He demanded that the experience, techniques, and personnel involved in manufacturing the KH-9 satellites not be used in the development of the LST because those resources were classified. As a result, Perkin-Elmer was forced to develop the equipment and facilities to design the mirror from scratch, causing the 1983 scheduled release date to drop to 1986.
Other delays were caused by the Challenger disaster in 1986, which grounded the ferry fleet. The recently renamed Hubble Space Telescope, designed to be transported into space by a shuttle, was forced to wait in a clean, nitrogen-purged room until its launch could be rescheduled. The cost of the wait was approximately $ 6 million a month, but it allowed engineers to make improvements, such as replacing a possibly fault-prone battery. It also allowed computer experts to further develop the software necessary to control Hubble, which was not ready in 1986 and was only completed when Hubble was finally launched in 1990.
Almost immediately, a potentially fatal flaw in Hubble’s scientific utility was discovered. The first light images from the telescope were of a drastically lower quality than expected. An investigation into the problem indicated that Perkin-Elmer had accurately ground the mirror, but without deforming 0.002 millimeters. This error had been detected during mirror development by one of the test procedures. However, a second test did not show spherical aberration and that measure was adopted as the most valid as a cost reduction management decision.
However, Hubble was designed to be repaired and replace instruments during subsequent shuttle missions. A plan was drawn up to bring a corrective mirror to the telescope during Service Mission 1 scheduled for December 1993. During five spacewalks, recording at 35 hours and 28 minutes, the astronauts took out the High Speed Photometer and installed the COSTAR device. , a 5,300-piece assembly robot that deployed six adjustable corrective mirrors in the optical pathways of the other scientific instruments.
Astronauts also used the mission to replace wobbly solar arrays and faulty gyros, as well as to install the second-generation wide-field planetary camera. On February 21, 1994, the newly repaired Hubble released the most detailed image to date of Pluto and its moon, Charon, beginning a career for which he has become internationally famous.
Despite Hubble’s colossal success, NASA has made plans to end the mission. As the shuttle program was nearing completion, the telescope’s service mission in 2009 included the installation of a ring on the outside of Hubble, allowing future missions, manned or robotic, to more easily capture the telescope. The intention is not, not surprisingly, to unite a rocket that would increase its orbit in an effort to combat the slow orbital decay caused by atmospheric drag. Instead, in what can only be described as an act of unscientific vandalism and a deliberate knockout, NASA plans to place a rocket to guide Hubble toward Earth, burning the telescope on re-entry.
The rationale for this is that the next generation of the James Webb Space Telescope (JWST) will be the successor to Hubble. In any scientific sense, this is not true. The JWST complement the Hubble Space Telescope, which looks more into infrared than ultraviolet light. This will allow more focus on more distant and cooler objects than what Hubble is optimized to study. It is expected to be able to detect stars in the early universe 280 million years older than Hubble.
However, the launch of the JWST has been delayed from an initial date sometime in 2011 to October 2018. The primary responsibility for this lies with the constant threats from Republicans in Congress, particularly those on the House Appropriations Committee. , to finish the project. In fact, in 2011, they completely canceled the project, although funding was later reinstated after an international scientific appeal. For its part, the Obama administration ensures that funding levels are kept as low as possible.
As such, there is no replacement for Hubble. At a cost of $ 10 billion (a pittance compared to what the United States spends on overseas wars or surveillance at home), after two and a half decades of groundbreaking scientific discovery and a generation of fuel for excitement of the scientific discovery, Hubble is expected to be forcibly exorbitant in 2024 as its orbital decay closes its scientific observations. JWST, which is not in orbit service, is expected to live only another four years. There are no credible plans for a successor mission. One that started seriously right now, developed at the same pace as JWST, would start observations in 2037.
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