ESO Key Astronomical Discoveries

ESOcast 75: ESO’s Top 10 Discoveries. Download and more info

Observations with ESO telescopes have led to many breakthroughs in astronomy, and, over the years, have been responsible for some truly remarkable findings. Here is our list of ESO´s Top 10 astronomical discoveries so far.

  1. Stars orbiting the Milky Way black hole

    Several of ESO's flagship telescopes were used in a close to 30-year-long study to obtain the most detailed view ever of the surroundings of the monster lurking at the heart of our galaxy — a supermassive black hole. The observations made with the VLT have for the first time revealed the effects predicted by Einstein's general relativity on the motion of a star passing through the extreme gravitational field near the supermassive black hole in the centre of the Milky Way. The 2020 Nobel Prize in Physics was awarded "for the discovery of a supermassive compact object at the centre of our galaxy".
    Science papers:
    Schödel et al. 2003 (Telbib),
    Gillessen et al. 2009 (Telbib)
    Read more in the ESO Press Release eso0226eso0846eso1151eso1332, eso1512, eso1825 and eso2006.

  2. Accelerating Universe

    Two independent research teams, based on observations of exploding stars, including those from ESO's telescopes at La Silla and Paranal, have shown that the expansion of the Universe is accelerating. The 2011 Nobel Prize in Physics was awarded for this result.
    Science papers:
    Perlmutter et al., 1999ApJ...517..565P (Telbib),
    Riess,A., 1998, AJ116 1009 (Telbib),
    Schmidt, B., 1998, ApJ 507 46 (Telbib),
    Perlmutter, S. et al, 1998, Nature, vol. 391, 51 (Telbib),
    Tonry, J.L. et al, 2003, ApJ (Telbib),
    Knop, R.A. et al, 2003, ApJ (Telbib),
    Riess, A. et al, 2004, ApJ (Telbib),
    Astier, P. et al, 2006, A&A (Telbib)
    Read more in the ESO Press Release eso9861

  3. Planet Found in Habitable Zone Around Nearest Star, Proxima Centauri

    The long-sought world, designated Proxima b, orbits its cool red parent star every 11 days and has a temperature suitable for liquid water to exist on its surface. This rocky world is a little more massive than the Earth and is the closest exoplanet to us — and it may also be the closest possible abode for life outside the Solar System.
    Science paper:
    Anglada-Escudé et al. (Telbib)
    Read more in the ESO Press Release eso1629

  4. Astronomers Capture First Image of a Black Hole

    ESO, ALMA, and APEX contribute to paradigm-shifting observations of the gargantuan black hole at the heart of the galaxy Messier 87 The Event Horizon Telescope (EHT) — a planet-scale array of eight ground-based radio telescopes forged through international collaboration — was designed to capture images of a black hole. EHT researchers have succeeded producing the first direct visual evidence of a supermassive black hole and its shadow. The image reveals the black hole at the centre of Messier 87, a massive galaxy in the nearby Virgo galaxy cluster.
    Science papers
    Paper I:The Shadow of the Supermassive Black Hole
    Paper II:Array and Instrumentation
    Paper III:Data processing and Calibration
    Paper IV:Imaging the Central Supermassive Black Hole
    Paper V:Physical Origin of the Asymmetric Ring
    Paper VI:The Shadow and Mass of the Central Black Hole
    Read more
    On the EHT page: and in ESO Press Release eso1907

  5. Revolutionary ALMA image reveals planetary genesis

    In 2014, ALMA, the Atacama Large Millimeter/submillimeter Array, revealed remarkable details of a solar system that is forming. The images of HL Tauri were the sharpest ever made at submillimetre wavelengths. They show how forming planets are vacuuming up dust and gas in a protoplanetary disc.
    Science paper: 2015ApJ...808L...3A
    Read more
    in the ESO press release eso1436

  6. First image of an exoplanet

    The VLT has obtained the first-ever image of a planet outside our Solar System. The 5-Jupiter-mass planet orbits a failed star — a brown dwarf — at a distance of 55 times the mean Earth-Sun distance.
    Science paper:
    Chauvin et al. 2004 (Telbib)
    Read more in the ESO Press Release eso0428

  7. First light from gravitational wave source

    ESO’s fleet of telescopes in Chile have detected the first visible counterpart to a gravitational wave source. These historic observations suggest that this unique object is the result of the merger of two neutron stars. The cataclysmic aftermaths of this kind of merger — long-predicted events called kilonovae — disperse heavy elements such as gold and platinum throughout the Universe.
    Science papers:
    E. Pian et al, 2017, Nature
    N. R. Tanvir et al, 2017, Astrophysical Journal Letters
    S. J. Smartt et al, 2017, Nature
    S. Covino et al, 2017, Nature Astronomy
    J. Hjorth et al, 2017, Astrophysical Journal Letters
    A. J. Levan et al, 2017, Astrophysical Journal Letters
    Read more in the ESO Press Release eso1733

  8. Direct measurements of the spectra of exoplanets and their atmospheres

    The atmosphere around a super-Earth exoplanet has been analysed for the first time using the VLT. The planet, which is known as GJ 1214b, was studied as it passed in front of its parent star and some of the starlight passed through the planet’s atmosphere. The atmosphere is either mostly water in the form of steam or is dominated by thick clouds or hazes. This follows from the earlier first direct spectrum of an exoplanet.
    Science papers:
    Bean, J. et al, 2010, Nature
    Janson, M. et al, 2010, ApJ

    Read more in the ESO Press Release eso1047 and in the ESO Press Release eso1002

  9. Cosmic temperature independently measured

    The VLT has detected carbon monoxide molecules in a galaxy located almost 11 billion light-years away for the first time, a feat that had remained elusive for 25 years. This has allowed astronomers to obtain the most precise measurement of the cosmic temperature at such a remote epoch.
    Science paper:
    Srianand, R. et al, 2008, A&A (Telbib)
    Noterdaeme et al., A&A (Telbib)
    Read more in the ESO Press Release eso0813

  10. Record-breaking planetary system

    Astronomers have found a system of seven Earth-sized planets just 40 light-years away. Using ground and space telescopes, including ESO’s Very Large Telescope, the planets were all detected as they passed in front of their parent star, the ultracool dwarf star known as TRAPPIST-1. Three of the planets lie in the habitable zone and could harbour oceans of water on their surfaces, increasing the possibility that the star system could play host to life. This system has both the largest number of Earth-sized planets yet found and the largest number of worlds that could support liquid water on their surfaces.
    Science paper:
    Gillon et al. (2017) (Telbib)
    Read more in the ESO Press Release eso1706