The James-Webb Telescope observed spiral galaxies like never before

Nineteen images released on January 29 show spiral galaxies in a unique way, like our own, the Milky Way.

Hypnotic and intriguing, they will make your head spin. Nineteen images of the spiral galaxy were released on Monday 29 January by the European (ESA) and American (NASA) space agencies. They were carried out using the instruments of the James Webb Telescope (JWST), the most powerful design to date. Spiral shapes are quite common for galaxies: according to estimates, this is the case for about 60% of them. Our galaxy, the Milky Way, is a representative.

In these images, the stars glow blue and the orange and red dust corresponds to dust around and between stars. Franceinfo interviewed several scientists to better understand what was observed and photographed.

Ghost Galaxy (NGC 628)

Located about 32 million light-years away in the constellation Pisces, this galaxy (also called NGC 628 or M74) has already been observed by James-Webb, leading to the release of an image in August 2022. The Hubble (in visible light) and Spitzer (in infrared) telescopes have already scanned many galaxies, including this one, but the JWST instruments provide incredible detail.

These are the scenes “Surprising even to researchers who have studied these galaxies for decades”Janice Lee, a scientist at the Space Telescope Science Institute in Baltimore (United States), commented. What Anne Hughes, member The Fangs Project (Physics at High Angular Resolution in Nearby Galaxies) that monitors 90 large galaxies where stars are forming and has a front-row seat to study these new photos: “We know these things, we know the power of James-Webb, it’s been working for decades. But when the images came, we still said, ‘Wow!'”

The James-Webb telescope operates in a register that allows us to specifically observe the first stages of star formation. These moments of youth are usually obscured as they arise in huge clouds of gas and dust. But the JWST instruments allow us to penetrate what normally escapes our gaze. “When we look in the visible, the dust absorbs the light. Then we see the dark bands. But this dust emits in the infrared and along the James-Webb. (specialized in infrared), “We can actually see these dust and gas structures.”Astrophysicist Eric Laugadek comments.

“We see filaments with gas and dust. We also see holes: that’s where stars have exploded.”

Eric Laugadek, astrophysicist

at franceinfo

Generally speaking, there are two main types of spiral galaxies, explained astronomer François Combes at the Collège de France in 2017: “Great Design”which represent regular shapes, with “Spiral arms that go from center to edge”And “stochastic”, Who will present? “small pieces of spiral arms”But without a coherent structure.

The Phantom Galaxy, distinguished by its great regularity and strong symmetry, is part of the first family. The “Pattern” The galaxy NGC 628, which can stimulate “lace” According to Anne Hughes, this is linked to the way young stars behave and form their environment, particularly the surrounding gases.

Among the 19 galaxy images published, NGC 4254 (also called M99), located 50 million light-years from Earth in the constellation Berenice Hare, is characterized by great regularity.

The (very) bright galaxy NGC 1087

The pattern of the galaxy NGC 1087, 80 million light-years away in the constellation Whale, is less regular than that of the Ghost Galaxy. But Anne Hughes points out that our eye is invariably drawn to the brightness of her heart.

This brightness, according to him, is linked to the activity caused by the supermassive black hole at the center of this galaxy. The glow can be caused by two things: either there is too much material, or it got too hot during the transfer of material from the galaxy’s core to its black hole.

The spiral pattern is easy to recognize in the following images (video), taken as part of the Fangs project, but made with instruments from the European Southern Observatory’s (ESO) Very Large Telescope, located in the Atacama Desert, Chile.

Barred spiral galaxies (such as NGC 3351 and NGC 1512)

Located in the constellation Leo, 33 million light-years from Earth, the galaxy NGC 3351, also called M95, is a spiral galaxy. And more precisely a barred spiral galaxy. A subfamily of which the Milky Way is a part. The spiral arms do not start directly from the center of the galaxy, but from a bar passing through its center.

In the image above, this bar is blue, highlighting the presence of a cluster of stars centered around the galactic center. These stars are all of the same age and have different characteristics than those present elsewhere in the galaxy, notes Annie Hughes.

Outside the central halo, spiral arm filaments are dotted with holes, as seen in other cases such as phantom galaxies. Overall, the pattern is in a similar vein to that for NGC 1512 (below). This other barred spiral galaxy is in the clock constellation, about 30 million light-years away.

If it specializes in the observation of very distant objects, the new facilities brought by the James-Webb Telescope to this section on spiral galaxies will allow us to better understand the formation of stars.