Chile is known worldwide for the quality of its dark skies, which, being located over the Atacama Desert, the most arid non-polar place on the planet, remain clear and stable. For this reason, it is currently an astronomical power due to the fact that nearly 40% of the infrastructure created to study the Universe is in its territory. By 2030, according to the Chilean Astronomical Society, SOCHIAS, this number will increase to 55%, in the optical-infrared range.
Carnegie astronomers arrived in the country in the 1960s, looking for an observing station in the Southern Hemisphere that would give them access to the Magellanic Clouds and the center of the Milky Way. In 1968, the then director of the Carnegie Observatories, Horace Babcock, met with Eduardo Frei, President of Chile at the time. That meeting allowed the Carnegie Las Campanas Observatory, LCO, to be established in 1969 on an excellent site high in the desert mountains at 2400 meters above sea level. The first lights of its Swope and du Pont telescopes, 1 and 2.5 meter reflectors, were in 1971 and 1977, respectively. The most recent additions were the twin Magellan, Baade and Clay telescopes, 6.5-meter reflectors - a collaborative effort of the Carnegie Institution, the University of Arizona, Harvard University, the University of Michigan and the Massachusetts Institute of Technology (MIT) - and leading members of what was the last generation of giant telescopes.
Magellan Telescopes (Credit: Yuri Beletsky)
"I came to LCO in 2002, as a 'visiting scientist' on a two-year invitation. From then on, my 'visit' was extended until I finally joined the staff as a resident astronomer. I always thought it would be wonderful to work at a modern observatory. The La Plata Observatory, where I studied and worked most of my life, has very beautiful instruments, but of historical value, and the city's sky is not suitable for astronomical observation. Carnegie Las Campanas Observatory is a great place for someone who enjoys observational astronomy," says Argentine scientist Nidia Morrell. "LCO is my home, I feel more at home there than anywhere else. I love the telescopes with all their instruments, the silence, the wildlife, everything," she adds.
About 100 people work at LCO. Most of them are engineers, technicians, astronomers and support staff. According to Leopoldo Infante, Director of LCO, the observatory is a large community that has a single goal: to develop world-class science.
"We are an observatory that provides operation of several telescopes, in partnership with other institutions, and is also concerned with the development of astronomy at the Carnegie Institution and in the world. There are regular observations 364 nights a year, based on observing projects approved by a committee. Those projects are assigned telescope time on some night of the year, 2 or 3 nights on average per project. When the date arrives, that telescope is made available to the astronomer in charge of the research. That night, the observatory's technical and scientific staff is at the disposal of that program, which is executed just as the astronomer needs it to be done," explains Infante, a Chilean astronomer and Director of LCO since 2017.
As well as other observatories in Chile, LCO makes 10% of the observing time available to the Chilean astronomical community, in all telescopes and instruments. This is part of an agreement with the Chilean Government, as a retribution for settling in that territory.
In addition to the Swope, du Pont and Magallanes telescopes, LCO hosts several associated projects that are led by external institutions. These projects take advantage of the excellent conditions offered by the site to carry out cutting-edge science. One of them is the Giant Magellan Telescope, GMTO, an extremely large telescope, part of the next generation of telescopes and currently under construction at Cerro Las Campanas. It will consist of 7 mirror segments, with a total optical area of 24.5 meters in diameter. The project is being developed by an international consortium of universities and research institutions.
What role will LCO play in the context of large telescopes?
"There are a series of observations that cannot be made with them, but can be made with medium-sized telescopes, as the Magellan telescopes will be considered at that time, for example. This is related to the follow-up of astrophysical phenomena or objects, as well as the follow-up of the great discoveries that will be made with the large telescopes. In addition, LCO is in a privileged place to do astronomy, so there is a lot of interest in setting up instruments at the site, which will then follow up on the science that is being done", Infante points out.
What distinguishes LCO from other observatories in Chile? According to Infante, it is basically the quality of the site and some technical aspects of the telescopes and instruments built for them. By design, unlike others, the area that the telescopes observe in the sky is larger. Another aspect that distinguishes the Magellan telescopes from others in the world is that they have several instruments available to astronomers during the night. "The astronomer can use two or three instruments during the night, simply switching from one to another, since they are calibrated, ready to be used. In most of the equivalent telescopes in the world, only one instrument can be used, available during that night to make certain observations," adds Leopoldo Infante.
Outstanding observations
In the 20th century, the expansion of the Universe, discovered by E. Hubble using Carnegie's Mount Wilson telescope, marked a before and after. In the 21st century, a team of four Carnegie astronomers obtained the first observation of a collision of two neutron stars, opening the door to a new era in astronomy. The Carnegie scientists were alerted to the event by the Laser Interferometry Gravitational-Wave Observatory (LIGO), which detects ripples in space-time caused by distant cosmic events. Thanks to a quick response, the observer on duty, Natalie Ulloa, from the Universidad de La Serena and currently part of the LCO staff, became the first human being to observe a neutron star merger, making Swope the first telescope to observe the optical counterpart of a gravitational wave source.
Undoubtedly, Carnegie and Las Campanas Observatory have been important players in the development of astronomy worldwide.
In 1984, Dr. Bradford A. Smith, from the University of Arizona, and Dr. Richard J. Terrile, from NASA's Jet Propulsion Laboratory (JPL), used the du Pont telescope together with a coronagraph and a CCD camera to take, for the first time, an image of a circumstellar disk. That is, the first observations of extrasolar planets were made from LCO.
In February 1987, astronomer Ian Shelton and LCO Instrument and Operations Specialist Oscar Duhalde discovered a bright supernova in the Large Magellanic Cloud while observing at LCO. This supernova, one of the most important discoveries in modern astronomy and named SN 1987A, was the closest such object seen since the invention of the telescope, and its great brightness made it possible to observe it with the naked eye.
The most distant supermassive black hole observed so far was detected in 2018 by a team led by Chilean astronomer Eduardo Bañados, a former Carnegie, and the confirmation and follow-up observations were made from the Baade telescope. "Why is this important? Because the theory has had to be accommodated to explain how a black hole formed so quickly in the Universe, when it was no more than 1.8 billion years old", explains Leopoldo Infante.
Nidia Morrell also highlights the Carnegie Supernova Project, (CSP, currently known as POISE, for Precision Observations of Infant Supernova Explosions) in which she participated together with Mark Phillips, former director of LCO and current Director Emeritus. This project provided photometry and spectrophotometry of a large sample of supernovae taken in well-understood and characterized telescope/filter/detector systems.
"Also important, I think, are the investigations of massive stars, especially in the Magellanic Clouds, which I do in collaboration with Phil Massey of Lowell, and among other interesting things led us to find a previously unknown class of Wolf-Rayet stars: the WN3/O3, which many researchers are still trying to understand. To name one more project for which I have a special affection, I mention the OWN (Follow-up of Galactic O and WN stars), also dedicated to massive stars, with the aim of studying their fundamental parameters and determining their multiplicity. That project was initiated in collaboration with Rodolfo Barbá, and since we unfortunately lost Rodolfo, it is led by Roberto Gamen. We observed many nights with the échelle de du Pont spectrograph, approximately between 2006 and 2020. In addition, the project includes observations from other 2-meter telescopes in Argentina and Chile", adds the scientist.
A few days ago, all the world's media reproduced the news that the Minor Planet Center of the International Astronomical Union recognized the discovery of a new moon of Uranus, as well as two new moons of Neptune. This finding involved Scott S. Sheppard of Carnegie Science, who used Magellan telescopes to find the brighter of the two newly discovered Neptunian moons.
What is the future of astronomy and what is LCO's contribution to it?
"That's hard to say, but I feel that I'm one of the last astronomers to go up into the mountains to observe. By the way, I recently read the book that Emily Levesque wrote on the subject: 'The last stargazers'. The future, I think, is more on the side of remote and queue-mode observations, with astronomers who without leaving their workplaces receive and analyze the information. And a lot of automatic processing (much of it already available) to be able to analyze large amounts of data with little human intervention. The possibility of remote observations already exists at Las Campanas, and I suppose it will be used more and more. The telescopes at Las Campanas play a very important role in modern astronomy, and with all the new instruments being developed for them, there is no doubt that this will be the case for many years to come," concludes Morrell.