Viikon kuva

22. toukokuuta 2023: Yli kahdessa vuosikymmenessä voi muuttua paljon, mikä näkyy näissä ESO:n VLT-teleskoopilta (Very Large Telescope) otetuissa kuvissa! Vasemmalla on VLT:n sen ollessa vielä rakenteilla Cerro Paranalin huipulla Chilessä, kun taas oikealla näemme sen kaikessa loistossaan sellaisena kuin se on tänä päivänä. Ennen teleskooppien rakentamista vuorta piti madaltaa 28 metriä teleskooppitasanteen rakentamiseksi, mikä tarkoitti noin 350000 kuutiometrin suuruista kallion poistamista. Vihdoin vuonna 1998 Unit Telescope UT1 (Antu), eli kuvassa vasemmanpuoleisin teleskooppi ja varhaisessa kuvassa pisimmälle rakennettu, otti ensimmäisen kuvansa maailmankaikkeudesta 25 vuotta sitten tällä viikolla. Nykyään VLT koostuu neljästä yksikköteleskoopista, joiden pääpeilit ovat halkaisijaltaan 8,2 metriä ja mukaan kuuluu neljä liikuteltavaa 1,8 metrin läpimittaista aputeleskooppia. Neljännesvuosisadan aikana tehtyjen havaintojen jälkeen VLT on edelleen yksi maailman kehittyneimmistä optisista/infrapuna-teleskoopeista ja se tekee jatkuvasti merkittäviä uusia löytöjä. Sitä ollaan parhaillaan päivittämässä, jotta se voisi jatkaa tehtäväänsä maailmankaikkeuden salaisuuksien paljastamiseksi. Nämä päivitykset varmistavat, että VLT säilyttää asemansa tieteen ja tekniikan eturintamassa vielä vuosien ajan. Paljon onnea ...

15. toukokuuta 2023: Have you ever seen a sunset so red? Probably not, since the cause of this reddened twilight sky is something quite dramatic: a volcanic eruption. This Picture of the Week was captured at ESO’s Paranal Observatory in Chile; under the Milky Way, on the top of the dark silhouette of Cerro Paranal, ESO’s Very Large Telescope looks upwards to the sky. On 15 January 2022, the submarine volcano Hunga Tonga–Hunga Ha‘apai erupted in the southern Pacific Ocean. This eruption created shock waves that rippled through the atmosphere, reaching places far from the volcano itself. At ESO’s Paranal and La Silla observatories in Chile, more than 10 000 kilometres away, weather stations detected these atmospheric disturbances. The eruption also launched an ash plume 57 kilometres tall, releasing massive quantities of particles into the atmosphere, including water vapour and dust. Sunlight is scattered and reddened by these tiny dust particles, and this ...

8. toukokuuta 2023: The telescope peeking out from its dome is the 1.52-metre telescope at La Silla Observatory. Being over 55 years old, the 1.52-metre is one of the oldest telescopes at ESO and it has participated in laying the foundation for many areas of astronomical research. Being a special telescope in many ways, it also has a twin, the 1.52-metre telescope at the Observatoire de Haute Provence in France. Both telescopes were specifically designed to do stellar spectroscopy and astrophotography, and the 1.52-m in La Silla involved no less than five instruments, including the B&C spectrograph. This instrument captured the spectrum of the Hale-Bopp comet as it passed by in 1995, one of the first recorded spectrums of a comet. After over 30 years of service, the 1.52-m at La Silla was decommissioned in 2002. Still sitting in its dome, it peers out over the vast Atacama Desert, and we get to ...

1. toukokuuta 2023: In this colorful Picture of the Week we see a portion of the Gum 10 nebula through the eyes of ESO’s Very Large Telescope in Chile. Gum 10 was discovered by the Australian astronomer Colin Stanley Gum, who in 1955 published a catalogue with more than 80 similar diffuse nebulae. The energetic ultraviolet radiation from the hot blue stars in Gum 10 ionise the gas in the nebula, stripping electrons away from their atoms. When these electrons combine again with the atoms, they emit light at very specific colours or wavelengths. The red shade in this image comes from hydrogen, the most abundant element in the Universe. The dark areas are dense clouds of dust that partially block our view of the objects behind them. This image, taken with the FORS2 instrument, was created as part of the ESO Cosmic Gems programme, an outreach initiative to produce images of interesting, ...

24. huhtikuuta 2023: This Picture of the Week shows a newly-formed planet with a mass similar to Jupiter’s orbiting the star HD 169142. The star has a disc around it, and as the protoplanet moves it carves a circular gap in the disc, as seen in the first image. But how was this planet found? Astronomers observed the system over several years with the SPHERE instrument at ESO’s Very Large Telescope in Chile. A new re-analysis of this data, led by Iain Hammond from Monash University in Australia, confirmed the presence of this protoplanet, which moves around the star at a distance somewhat larger than that between Neptune and the Sun. They also identified a spiral wake that the protoplanet leaves behind as it rearranges part of the material in the disc, much like a boat can create a wake as it moves through water. A protoplanet forms during the early stages of ...

17. huhtikuuta 2023: This Picture of the Week shows the young stellar object 244-440 in the Orion Nebula observed with ESO’s Very Large Telescope (VLT) –– the sharpest image ever taken of this object. That wiggly magenta structure is a jet of matter launched close to the star, but why does it have that shape? Very young stars are often surrounded by discs of material falling towards the star. Some of this material can be expelled into powerful jets perpendicularly to the disc. The S-shaped jet of 244-440 suggests that what lurks at the center of this object isn’t one but two stars orbiting each other. This orbital motion periodically changes the orientation of the jet, similar to a water sprinkler. Another possibility is that the strong radiation from the other stars in the Orion cloud could be altering the shape of the jet. These observations, presented in a new paper led by ...

10. huhtikuuta 2023: Don’t worry, no planets were harmed in the making of this Picture of the Week! The powerful laser beams seen here are installed in one of the four 8.2-m telescopes of ESO’s Very Large Telescope (VLT) in Chile. They allow astronomers to obtain very sharp images of the cosmos by correcting the blur caused by turbulence in the atmosphere, but how? The lasers are tuned to a very specific colour that excites sodium atoms floating 90 km above the ground, making them glow. This creates artificial “stars” high up in the sky, whose rapid twinkling is monitored in real time by special sensors. Then, instructions are sent to the telescope’s deformable secondary mirror, which quickly reshapes itself to counteract the atmospheric distortion. And all of this happens at millisecond speeds! This technique, known as adaptive optics, can also use real stars as a reference to measure the turbulence. But there ...

3. huhtikuuta 2023: From the long eastward shadows of the telescopes in this Picture of the Week we can see that it’s almost the beginning of a long night shift of stargazing for the telescopes at ESO’s La Silla Observatory. In the foreground of this picture is the BlackGEM array, designed to hunt for the visible light of gravitational wave sources. If you then follow the road up to the summit of La Silla you will pass several ESO telescopes including the 1-metre Schmidt telescope and the New Technology Telescope, until you finally reach the 3.6-metre telescope at the top, home to the HARPS planet hunter. La Silla mountain is ideally situated for an observatory as its isolated location means there is very little light pollution. It is also in Chile’s extremely dry Atacama desert at an altitude of 2400 metres, meaning there’s hardly ever a cloud in the sky and almost every ...

29. maaliskuuta 2023: The circled spot in this Picture of the Week has almost disappeared. What happened? This sequence of images, taken in optical light with ESO’s Very Large Telescope, shows the gamma-ray burst GRB 221009A fading away. Gamma-ray bursts are the most luminous phenomena that we know of in the universe, and GRB 221009A is the brightest one yet as seen from Earth. The burst was detected in October 2022 by several gamma-ray space telescopes, such as NASA's Swift and Fermi and ESA’s INTEGRAL. Then, a few hours after the initial detection, ESO’s X-shooter instrument at the VLT took a spectrum, which provided the first distance measurement to the explosion of approximately 2400 million light years. Thanks to this distance measurement, a team of astronomers led by Daniele Bjørn Malesani (Radboud University, the Netherlands; DAWN/Niels Bohr Institute, Denmark) ruled out an origin in the Milky Way, although the burst is still much ...

20. maaliskuuta 2023: This Picture of the Week shows a beautiful meeting between the Swedish–ESO Submillimetre Telescope (SEST) and the Milky Way, apparently almost touching each other. This shot was taken at ESO’s La Silla Observatory, located on the outskirts of the Chilean Atacama Desert, at an altitude of 2400 metres. Light and darkness shape the Milky Way as it stretches across the night sky. The dark patches are dust clouds blocking the light behind them, coming from millions of stars in the central region of our galaxy. SEST was built on behalf of the Swedish Natural Science Research Council (NFR) and ESO in 1987. It is a 15-m radio telescope, and it was the only large sub-millimetre telescope in the southern hemisphere at the time of first light. In 2003, the telescope was decommissioned as it was superseded by the Atacama Pathfinder EXperiment telescope (APEX) and the Atacama Large Millimeter/submillimeter Array (ALMA) ...

13. maaliskuuta 2023: This picture of the week shows the Sun’s path on the sky as seen from ESO’s Paranal Observatory in Chile. The picture was taken with a pinhole camera with an exposure of 8 months, from 17 April to 11 December 2018. The tall structure in the foreground is the “seeing monitor”, which measures the blur/twinkling of the stars due to the atmospheric turbulence. In the background we can see several domes; the ones to the centre-left are part of the Very Large Telescope, and the rightmost one is the VLT Survey Telescope. But what are those bright coloured lines behind them? They are created by the Sun as it moves in the sky throughout the day, leaving an imprint on the sheet of photographic paper placed inside the pinhole camera. The camera was facing west, so here we see hundreds of sunsets. But as the Earth moves around the Sun, ...

6. maaliskuuta 2023: In this Picture of the Week, we take a deep plunge into the ocean of stars in the IC4701 nebula. This nebula is located in the Sagittarius constellation, and it is twice as wide as the full Moon in the sky. The energetic light from newly-born stars ionizes the hydrogen gas in the nebula, causing it to emit the intense reddish hue seen in this picture. The dark clouds in this image contain large amounts of interstellar dust, too dense for the light of the background stars to pierce through it. The IC4701 nebula is part of a rich and vast complex of dust and gas within which new stars spring to life. When stars are born, most of them are cooler, redder, and less massive than our own Sun. Hotter, more massive stars are much rarer, and they quickly burn through all their fuel and die. This makes these ...

27. helmikuuta 2023: Tässä viikon kuvassa Venus loistaa kirkkaasti Chilen ESO:n La Sillan observatorion yllä. Kuva on otettu juuri ennen aamun koittoa kohti itää, ja siinä näkyy myös utuinen eläinratavalo, joka on aurinkokunnan pölyhiukkasten sirottamaa auringonvaloa. Vasemmalla olevat kolme BlackGEM-teleskooppia tien vasemmalla puolella ovat Radboud Universityn, Netherlands Research School for Astronomyn (NOVA), ja KU Leuvenin rakentamat. BlackGEM etsii maailmankaikkeuden dramaattisimpia tapahtumia, kuten mustien aukkojen ja neutronitähtien törmäyksiä. LIGO ja Virgo-observatoriot voivat havaita näiden rajujen tapahtumien aiheuttamia ajan ja avaruuden värähtelyitä. Suuren näkökenttänsä ansiosta BlackGEM-teleskoopit pystyvät paikantamaan näiden tapahtumien jälkihehkun ja siten paikantamaan, missä törmäys tapahtui. Näin tähtitieteilijät voivat tutkia tarkemmin, mitä tapahtuu, kun mustat aukot ja neutronitähdet yhdistyvät. Linkit Selityksin varustettu versio kuvasta.

20. helmikuuta 2023: No, you’re not seeing double: this Picture of the Week shows two images of a Jupiter-like planet that orbits the star AF Leporis. The planet has been imaged by two independent groups of astronomers using the SPHERE instrument on ESO’s Very Large Telescope (VLT) in Chile. But why did they target this particular star? The two groups, led by Dino Mesa (INAF, Italy) and Robert De Rosa (ESO, Chile), studied star catalogues from the European Space Agency’s Hipparcos and Gaia satellites. Over the years, these two space missions have accurately pinpointed the position and motion of stars in our galaxy using astrometry. Planets exert a gravitational tug on their host stars, perturbing their trajectory on the sky. The two teams found that the star AF Leporis exhibited such a disturbed trajectory, a telltale sign that a planet could be hiding there. As the two groups took a closer look at ...

13. helmikuuta 2023: The Atacama Desert of Chile is one of the driest places on Earth, with extremely reliable weather, making it an excellent site to explore the Universe. So it’s not strange that this is the place ESO has chosen to place the flagship facilities for European ground-based astronomy. At 2635 meters above sea level in the Atacama Desert, we find ESO’s Paranal Observatory, seen on the far mountain top in this image. It hosts several world-class telescopes like the Very Large Telescope (VLT), and the Visible and Infrared Survey Telescope for Astronomy (VISTA), the latter located on its own peak, seen here to the right of the main one. But the desert is good for other astronomy related sciences as well: Mars explorations! The red and rocky environment around Paranal has a strong resemblance to Mars, making it a perfect site for the European Space Agency (ESA) to test their Mars ...

6. helmikuuta 2023: Fall deeper into the entrancing NGC 4303, a spiral galaxy located approximately 55 million light-years from Earth in the constellation Virgo. This image combines data taken at radio and visible wavelengths, and is helping astronomers understand how stars form in galaxies. The hypnotising golden glow drawing you into the image corresponds to clouds of molecular gas, the raw material out of which stars form. The data was taken with the Atacama Large Millimeter/submillimeter Array (ALMA), co-operated by ESO in the Chilean Andes. The blueish regions in the background, on the other hand, were imaged with the Multi-Unit Spectroscopic Explorer (MUSE) instrument on ESO’s Very Large Telescope (VLT), also in Chile, and they reveal already formed stars. By comparing the distribution of gas and stars astronomers are able to study what triggers, enhances or hampers the birth of new stars. This image is part of the Physics at High Angular resolution ...

30. tammikuuta 2023: This Picture of the Week shows the grand skies of the Chajnantor plateau in the Chilean Atacama desert. The rare sight of clouds in this typically dry and arid region creates a dramatic display of reds and blues, as well as a sun pillar –– an optical phenomenon caused by ice crystals in the atmosphere –– that emanates from the Sun in line with a telescope. This large antenna is a part of the Atacama Large Millimeter/submillimeter Array (ALMA), which is co-owned by ESO. ALMA is one of the most powerful observatories in the world for radio astronomy. Its collection of 66 antennae — like the one pictured above — has been responsible for many incredible ground-breaking discoveries, including contributing to the creation of the first image of a black hole.

23. tammikuuta 2023: In this Picture of the Week, a three hour long photographic sequence shows the path of a lunar eclipse over ESO’s Very Large Telescope (VLT) at Paranal, Chile. This eclipse, which took place on 20-21 January 2019, was visible from the Americas. As the Moon moves into the Earth’s shadow, it becomes darker and acquires a red hue. This reddening, which is due to sunlight being scattered by Earth’s atmosphere before reaching the Moon, can be seen in the middle of the trail. This trail, and those of the stars in the background, are due to the Earth’s rotation and are a ubiquitous feature in long exposure photographs of the night sky. The stars above ESO’s telescopes can be seen clearly because of the high altitude at the Paranal mountain and the lack of light pollution from human settlements. But the bright lunar light can still disturb astronomical observations done ...

16. tammikuuta 2023: Vuodesta 1979 lähtien ESOs La Sillan observatorion 1.54-metrinen Danish telescope kaukoputki on tutkinut kotigalasimme yksityiskohtia. Tässä kuvassa kaukoputken yllä näkyy Linnunrata ja sen galaktinen sydän, mikä loistaa Chilen autiomaan yötaivaan yllä. Tanskalaista 1,54-metrin kaukoputkea käytettiin 15 vuotta kestäneessä taivaankartoituksessa, joka julkaistiin vuonna 2004 ja jossa tutkittiin 14000 galaksimme tähteä. Kartoitus antoi ensimmäiset vihjeet Linnunradan myrskyisästä ja hurjasta menneisyydestä. Siinä mitattiin tähtien liikkeitä ja etäisyyksiä sekä niiden ikää ja kemiallista koostumusta. Tämän avulla saatiin tehtyä Linnunradan historiallinen kartta, joka paljasti galaksin paljon monimutkaisemman historian kuin aiemmin oletettiin. Linnunrata kulkee Chilen yötaivaan poikki ja näyttäytyy kuvassa rauhalliselta, mutta taivaankartoituksessa löytyi jälkiä aiempaa paljon dynaamisemmista vaiheista. Erityisesti törmäykset muiden pienempien galaksien kanssa toivat mukanaan jättimäisiä kaasupilviä, jotka saivat Linnunradan heräämään henkiin ja johti tähtien muodostumiseen ja supernovaräjähdyksiin. Tämä kaikki tekee Linnunradasta upean paikan, jota kutsumme kodiksemme.

10. tammikuuta 2023: Tämän viikon kuvassa tutustumme lähemmin galaksiin UGC4211, josta tähtitieteilijät ovat löytäneet kaksi sulautumassa olevaa supermassiivista mustaa aukkoa, joiden välinen etäisyys on vain 750 valovuotta. Musta aukko pari on lähin tähän mennessä löydetyistä ja etäisyys on alle puolet edellisestä ennätyksestä. Havainnoissa on käytetty useita eri aallonpituuksia. Tässä on käytetty ESO:n Very Large Telescope, eli VLT-kaukoputkea ja Atacama Large Millimeter/submillimeter, eli ALMA-verkostoa, jonka kumppani ESO on. Havainnoissa on lisäksi käytetty muita teleskooppeja, joilla on havaittu mustien aukkojen niellessä materiaa vapautuvaa voimakasta säteilyä. Molemmissa kuvissa on käytetty Chilen ESO:n VLT:n MUSE-instrumentin havaintoja. Vasen kuva näyttää perinteisen näkymän tähän galaksiin, jossa pölyjuovat peittävät tähtien valoa alleen. Oikean puoleisessa kuvassa hapen, typen ja vedyn emissio näkyy sinisenä, vihreänä ja punaisena valona. Punainen paljastaa tähtien muodostusalueet, ja kirkas valkoinen keskialue paljastaa kahden supermassiivisen mustan aukon alueen, jolta ne keräävät materiaa. Michael Kossin johtama tiimi Eureka Scientificistä Yhdysvalloista identifioi nämä kaksi mustaa aukkoa ja tutki niitä yksityiskohtaisesti ...