In a long presentation this Tuesday morning (12), the world had access to the first scientific observations of the James Webb Space Telescope. Going from the depths of the cosmos to an exoplanet a thousand light-years away, they effectively demonstrate the potential of the new satellite.
The presentation began with the ends of the Universe, resuming the image shown the day before at an event at the White House. Called Webb’s First Deep Field, it targeted the galaxy cluster SMAC 0723. The powerful gravity of this cluster of galaxies about 5 billion light-years away creates a lensing effect that amplifies the image of even more distant stars — at least one of them, highlighted by the agency in the presentation, is seen in the image as it was 13.1 billion years ago.
One of Webb’s central goals is precisely to see beyond what Hubble was able to, eventually detecting the first galaxies to form in the Universe. The Big Bang happened 13.8 billion years ago, and the new space telescope expects to see objects as they were until 13.5 billion years ago.
The trick to seeing the baby Universe is possible thanks to the fact that the speed of light, although very large, is limited. The further away an object is, the longer the light has had to travel to reach us, which means we have an older image of it.
This applies even to the closest astronomical objects: when we look at the Sun in the sky, we are seeing it as it was 8.3 minutes ago, since that is the time it takes for the light emitted there to get here, crossing the distance of 150 million km (or 8.3 light-minutes). When we look at objects several billion light-years away, we see them as they were billions of years ago. And Webb will do that better than any other telescope, not only because of its 6.5-meter mirror (the largest ever launched into space), but because it works with infrared light (the only one available for observing extremely bright objects). distant, representative of what the Universe was like when it was only 300 million years old).
The second revelation wasn’t exactly an image, but a spectrum — the light signature of the atmosphere of a gas giant exoplanet called Wasp-96b, located about 1,150 light-years from here in the constellation Phoenix. Completing a revolution around its star every 3.4 days, it is a superhot planet, about the size of Jupiter but half as massive. The spectrum collected by the Niriss instrument, an infrared imager and spectrograph, was obtained over 6.4 hours of observation.
It was an immediate record: it already had the most detailed near-infrared spectrum obtained from the atmosphere of an exoplanet and made it possible to identify the presence of water vapor in the air of this seething gaseous world. Over the next few months, Webb is expected to observe rocky exoplanets with the same technique, perhaps confirming the habitability of one of them.
The third image brought the Southern Ring nebula (cataloged as NGC 3132), the result of the death of a binary star within our Milky Way, about 2,500 light-years away. In fact, there were two images of this so-called planetary nebula, taken with two of the four telescope instruments. NIRCam, which “sees” in the near-infrared range, and Miri, which detects mid-infrared. The contrast between the two views helps to understand the dynamics taking place inside the nebula, with ionized gas being blown by the hot stars inside, and outer shells of gas and dust, created by the expulsion of the outer layers of the central stars, generating the contours of the nebula. nebula.
The fourth image portrayed a spectacle of five galaxies, Stephan’s Quintet. It is a group of galaxies located about 290 million light-years from here, in the constellation Pegasus. It was the first compact group of galaxies discovered, in 1877 by French astronomer Édouard Stephan, and features four of five galaxies locked in a cosmic dance of frequent close encounters. The farm just seems to be close, but it’s actually much closer to us. In the Webb image, it is possible to see individual stars in the nearest galaxy, as well as a number of background galaxies.
To close the show, NASA brought an incredible image of the Carina nebula, one of the largest and brightest in the sky, located about 7,600 light-years from Earth. It is a large stellar nursery, home to many high-mass stars, much larger than the Sun, which had already enchanted the world in images from the Hubble Space Telescope. Now, with Webb, the vision brings a new level of definition, revealing structures that astronomers can’t even explain exactly what they are.
In addition to presenting these first images, the event was a great celebration of the success of Webb, a project led in partnership by NASA, ESA and CSA (respectively American, European and Canadian space agencies) that consumed two decades and more than US$ 10 billion. Launched on the European Ariane 5 rocket in December 2021, it has spent the last six months in the commissioning phase in space, preparing its systems for full operation. From now on, the scientific program begins, and the images revealed with pomp by the American space agency are just the beginning. Many discoveries are yet to come. The telescope is estimated to have at least 20 years of fuel to remain in operation.
