discovery of the most distant star and galaxy from Earth – Liberation

The glimpse of ‘Earendel’ and ‘HD1’ marks two milestones in the field of astronomy, allowing us to better distinguish the earliest remnants of the universe that go back billions of years.

Astronomy is a formidable time machine: the more modern the tools, the more advanced the technologies, and the better we are able to uncover the first remnants of the universe, closer and closer to the beginning of everything: the Big Bang. Within a week, two discoveries were announced: the most distant star and galaxy known to date.

A star magnified by space-time distortion

The star was discovered by Hubble. You have to know a little about the laws of physics to recognize it, because it does not look like a shimmering white or yellow dot at all. It is a dark red, irregularly dotted bow, like a trace of jam. This is because its image is distorted by a huge cluster of galaxies lying between the star and Earth. From our point of view, the star is hidden behind this crowd. It should not be seen if the light traveled in a straight line. But the galaxy cluster produces such gravity that it distorts space-time around it, and the rays of light find themselves in bypassing it and then continuing their path to our eyes. This is called the gravitational lensing effect. It allows us to see dimly lit and hidden stars, miraculously deformed and amplified as through a magnifying glass.

Light from the star WHL0137-LS, which has been christened Earendel (an Old English word for “morning star”), took 12.9 billion years to reach Earth. The image of her taken with the Hubble Telescope therefore dates from the primitive era, when the universe was only 900 million years old (7% of its current age). According to astrophysicists, it must have been 50 times the mass of our sun and millions of times brighter. But today it no longer exists. “Based on her mass, she certainly has not survived until today,” explains astrophysicist Brian Welch, lead author of the study. “The more massive stars burn their fuel faster and then explode or collapse into black holes. The oldest known stars were formed around the same time, but they are less massive and continue to shine to this day.

The previous record for the most distant star was set in 2018, with a star dating back to when the universe was 4 billion years old.

A galaxy full of energy

The record for the most distant known galaxy dates back to 2016: GN-z11 was discovered, as it was 13.4 billion years ago. It has just been dethroned by HD1, whose light would have traveled for 13.5 billion years. It looks particularly bright in ultraviolet wavelengths, indicating high energy activity. Where’s she from ?

Astronomers have two tracks: either it houses a supermassive black hole (100 million times more massive than our sun) at its center, which would make it the oldest black hole we know of. Either it is a nursery for some of the very first stars in the universe that we have not yet been able to observe.

The first lights in the universe will be studied by the new James Webb Space Telescope, launched by NASA this Christmas. After months of adjustment, the telescope is expected to begin observing the ancient times of the universe this summer.

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