Watch the incredible capture of starlight by the Webb telescope 0:50
(CNN) --
The James Webb Space Telescope has the sharpest view of the universe's invisible light.
The long-awaited first scientific images from the world's main space observatory are not expected before this summer.
But recent test images captured by the telescope during the final phase of its commissioning give a glimpse of things to come.
"These are the sharpest infrared images ever taken by a space telescope," said Michael McElwain, project scientist for the Webb Observatory at NASA's Goddard Space Flight Center in Greenbelt, Maryland, at a news conference Monday.
Webb will be able to peer into the atmospheres of exoplanets and observe some of the first galaxies created at the beginning of the universe by viewing them in infrared light, which is invisible to the human eye.
The images were captured after the successful alignment of the telescope's huge golden mirror segments.
The tests show the sharp, well-focused images that the observatory's four instruments are capable of capturing.
James Webb telescope captures starlight
But the most surprising result came from a comparison of images of the same group of objects taken by Webb's mid-infrared instrument with the Spitzer Space Telescope's now-retired infrared array camera.
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Spitzer, once one of the space telescopes belonging to NASA's Great Observatories program, was the first to capture high-resolution images of the universe in near- and medium-infrared light.
Webb's giant mirror and sensitive detectors can pick up even more detail and enable more discoveries than Spitzer.
Scientists studying the two images of the Large Magellanic Cloud, a small neighboring galaxy of the larger Milky Way, noted that Webb's image reveals unprecedented detail of the interstellar gas between the stars.
Compare the sharpness and level of detail captured by the Spitzer Space Telescope (left) and the James Webb Space Telescope (right).
"You can see that the Webb images are going to be better because we have 18 segments, each of which is larger than the single segment, so to speak, that made up the Spitzer telescope's mirror," said Marcia Rieke, principal investigator. Webb Near Infrared Camera and Regents Professor of Astronomy at the University of Arizona, during the press conference.
“But it's not until you really see the kind of image that it offers that you really internalize it and say, 'Wow, just think about what we're going to learn.'
Spitzer taught us a lot.
This is like a whole new world."
Approaching the starting line
Webb is now in the final phase of preparation before he is ready to begin conducting science observations.
"I would call this the home stretch," McElwain said.
"We planned about 1,000 activities for the launch, and there are only about 200 left to complete."
This is how the Webb telescope's fine orientation sensor works, the most accurate ever built
Webb's instruments are undergoing their final checks and calibrations, while the telescope team on the ground evaluates the performance of each to ensure they are ready to collect data successfully.
Each instrument has four or five science modes, each of which must meet specific criteria.
One special Webb mode includes moving target tracking, which is especially useful for scientists who want to study objects in the icy reaches of our solar system as they orbit the sun.
"When this phase is complete, we will be ready to release scientific instruments into the universe," McElwain said.
The first images
The first images of the universe from Webb, called early delivery observations, or EROs, are expected to come out in mid-July, Klaus Pontoppidan, Webb project scientist at the Space Telescope Science Institute in Baltimore, said during the news conference. .
A more precise date will be shared later, he said.
These first "spectacular color images" will show that Webb is fully operational and will be the "start of many years of science" to celebrate, Pontoppidan said.
The exact targets Webb will be aiming at for these first images were not revealed because the telescope team doesn't want to spoil the surprise.
And those goals could change as the team gets closer to capturing images.
The first images will resemble what we're used to seeing from the Hubble Space Telescope in terms of aesthetic quality, Pontoppidan said.
"Astronomy will never be the same once we see what (Webb) can do with these first observations," said Christopher Evans, Webb project scientist at the European Space Agency, during the news conference.
astronomy Webb Telescope
