Gravitational Lens Reveals Galaxy 800 Million Years After Big Bang
▼ Summary
– Using the James Webb Space Telescope, astronomers observed LAP1-B, an ultra-faint galaxy as it existed 800 million years after the Big Bang, making it the most chemically primitive galaxy ever seen.
– LAP1-B was detected thanks to gravitational lensing from the MACS J046 galaxy cluster, which magnified its light by roughly 100-fold.
– Even with this magnification, LAP1-B was too dim for JWST or Hubble to detect its stars’ steady background light.
– By calculating from the galaxy’s distance and telescope sensitivity, scientists determined LAP1-B’s stellar mass has an upper limit of 3,300 Suns, a tiny fraction of the Milky Way’s 100 billion solar masses.
– The observation marks a breakthrough in seeking the faint, small galaxies that were building blocks of the early Universe, which previous telescopes like Hubble could not spot.
For years, astronomers using instruments like the Hubble Space Telescope have searched for signs of the Universe’s earliest stars. These faint, fledgling galaxies,the foundational building blocks of modern cosmic structures,remained frustratingly out of reach, too dim for even the most advanced observatories. That search has now taken a decisive turn, thanks to a combination of the James Webb Space Telescope and a fortunate cosmic alignment.
A team led by Kimihiko Nakajima, an astronomer at Kanazawa University in Japan, recently published findings in Nature describing their observation of an ultra-faint galaxy known as LAP1-B. This galaxy existed just 800 million years after the Big Bang, making it the most chemically primitive galaxy ever detected.
To glimpse an object so distant and faint,LAP1-B lies 13 billion light-years away,the Webb telescope needed help. Even its massive, gold-coated beryllium mirrors weren’t enough on their own. The key was a phenomenon called gravitational lensing, created by a massive galaxy cluster named MACS J046. This cluster warps the fabric of spacetime between Earth and LAP1-B, acting like a natural magnifying glass.
“The galaxy was strongly magnified through the gravitational lensing effect,” Nakajima explained. This effect boosted the light traveling from LAP1-B toward Earth by roughly 100 times.
Yet even with that hundredfold increase in brightness, LAP1-B remained so faint that neither Webb nor Hubble could detect its stellar continuum,the steady background glow emitted by its stars. For Nakajima and his team, that absence itself became a clue. By calculating the distance to LAP1-B and factoring in telescope sensitivity, they determined that the galaxy’s total stellar mass cannot exceed 3,300 Suns. That is an astonishingly small figure compared to the Milky Way, which holds roughly 100 billion solar masses.
(Source: Ars Technica)