Announcing the Closest and Farthest Objects from Outside Our Cosmic Neighborhood in the Same Week
On April 6, 2022, the United States Space Command tweeted a formal letter that was sent a month earlier to the NASA Directorship under the leadership of Dr. Thomas Zurbuchen. The letter stated that the interstellar meteor discovered by my student Amir Siraj and me in 2019 is indeed of interstellar origin. This meteor detection, dating back to January 8, 2014, predated `Oumuamua by almost four years and should be recognized as the first interstellar object ever discovered, as described in my previous essay.
The original discovery paper was declined from publication because the error bars on the meteor data were classified. It took three years to get the government to confirm that this meteor is interstellar at the 99.999% confidence. We now know that this was the closest object ever detected from outside the Solar system.
But within a day, this important revelation was followed by a press release from my research group on the farthest object ever detected, a galaxy named HD1 discovered by the Subaru Telescope, VISTA Telescope, UK Infrared Telescope and Spitzer Space Telescope. This galaxy is inferred to have a redshift of 13, implying that it emitted its light only 300 million years after the Big Bang.
HD1 is the earliest massive galaxy ever detected. Its discovery is good news for the James Webb Space Telescope (JWST) which will likely find many more. Finding a mushroom in the periphery of the backyard often implies that there are many more out there.
It took light 13.5 billion years to reach us, but by now the source is even farther because of the cosmic expansion. What we see is the source when the light left it 13.5 billion years ago. By now it is farther away and older than it was when the light left it.
The light from HD1 could have been emitted by a burst of star formation, in which case the stars should have been mostly massive. This is expected for the first generation of stars, commonly labeled Population-III stars. But the light could have also been emitted by a black hole weighing a hundred million Suns.
As the earliest supermassive black hole, HD1 would represent a giant baby in the delivery room of the early universe. It would break the highest quasar redshift on record by almost a factor of two, a remarkable feat. In the short time available for its early growth after the Big Bang, it must have started from a massive seed and increased its mass by eating matter from its immediate environment at an unprecedented rate. This surprising result would demonstrate once again that nature is more imaginative than we are.
If HD1 is a black hole, we should observe X-ray emission from it. If we do not detect X-ray emission with the Chandra X-ray Observatory or if JWST would resolve the extended image of the emitting galaxy, then the emission must originate from massive stars.
We wish to know when the first stars and galaxies formed and what impact they had on the rest of the universe, in terms of enriching it with heavy elements and breaking the cosmic hydrogen atoms left over from the Big Bang, to their constituent electrons and protons.
The first galaxies formed about a hundred million years after the Big Bang. They were a millionth of the mass of the Milky Way and much denser. The can be regarded as the building blocks in the construction project of present-day galaxies, like our own Milky Way.
Since the first galaxies were small and we can see them only at large distances, most of them are very faint. With big enough future telescopes we hope to explore the very first stars and galaxies.
This is a quest for our cosmic roots, as life would not exist without the heavy elements produced by the first stars. Astronomers will seek to complete the scientific details of the story of genesis, “Let there be light.”
Altogether, I feel very fortunate to be involved in the discovery of the closest and farthest objects from outside our immediate cosmic neighborhood.
ABOUT THE AUTHOR
Avi Loeb is the head of the Galileo Project, founding director of Harvard University’s — Black Hole Initiative, director of the Institute for Theory and Computation at the Harvard-Smithsonian Center for Astrophysics, and the former chair of the astronomy department at Harvard University (2011–2020). He chairs the advisory board for the Breakthrough Starshot project, and is a former member of the President’s Council of Advisors on Science and Technology and a former chair of the Board on Physics and Astronomy of the National Academies. He is the bestselling author of “Extraterrestrial: The First Sign of Intelligent Life Beyond Earth” and a co-author of the textbook “Life in the Cosmos”, both published in 2021.