An international team of astronomers, including researchers at the Center
for Astrophysics | Harvard & Smithsonian, has spotted the most distant
astronomical object ever: a galaxy.
Named HD1, the galaxy candidate is some 13.5 billion light-years away and is
described Thursday in the Astrophysical Journal. In an accompanying paper
published in the Monthly Notices of the Royal Astronomical Society Letters,
scientists have begun to speculate exactly what the galaxy is.
The team proposes two ideas: HD1 may be forming stars at an astounding rate
and is possibly even home to Population III stars, the universe's very first
stars—which, until now, have never been observed. Alternatively, HD1 may
contain a supermassive black hole about 100 million times the mass of our
Sun.
"Answering questions about the nature of a source so far away can be
challenging," says Fabio Pacucci, lead author of the MNRAS study, co-author
in the discovery paper on ApJ, and an astronomer at the Center for
Astrophysics. "It's like guessing the nationality of a ship from the flag it
flies, while being faraway ashore, with the vessel in the middle of a gale
and dense fog. One can maybe see some colors and shapes of the flag, but not
in their entirety. It's ultimately a long game of analysis and exclusion of
implausible scenarios."
HD1 is extremely bright in ultraviolet light. To explain this, "some
energetic processes are occurring there or, better yet, did occur some
billions of years ago," Pacucci says.
At first, the researchers assumed HD1 was a standard starburst galaxy, a
galaxy that is creating stars at a high rate. But after calculating how many
stars HD1 was producing, they obtained "an incredible rate—HD1 would be
forming more than 100 stars every single year. This is at least 10 times
higher than what we expect for these galaxies."
That's when the team began suspecting that HD1 might not be forming normal,
everyday stars.
"The very first population of stars that formed in the universe were more
massive, more luminous and hotter than modern stars," Pacucci says. "If we
assume the stars produced in HD1 are these first, or Population III, stars,
then its properties could be explained more easily. In fact, Population III
stars are capable of producing more UV light than normal stars, which could
clarify the extreme ultraviolet luminosity of HD1."
A supermassive black hole, however, could also explain the extreme
luminosity of HD1. As it gobbles down enormous amounts of gas, high energy
photons may be emitted by the region around the black hole.
If that's the case, it would be by far the earliest supermassive black hole
known to humankind, observed much closer in time to the Big Bang compared to
the current record-holder.
"HD1 would represent a giant baby in the delivery room of the early
universe," says Avi Loeb an astronomer at the Center for Astrophysics and
co-author on the MNRAS study. "It breaks the highest quasar redshift on
record by almost a factor of two, a remarkable feat."
HD1 was discovered after more than 1,200 hours of observing time with the
Subaru Telescope, VISTA Telescope, UK Infrared Telescope and Spitzer Space
Telescope.
"It was very hard work to find HD1 out of more than 700,000 objects," says
Yuichi Harikane, an astronomer at the University of Tokyo who discovered the
galaxy. "HD1's red color matched the expected characteristics of a galaxy
13.5 billion light-years away surprisingly well, giving me a little bit of
goosebumps when I found it."
The team then conducted follow-up observations using the Atacama Large
Millimeter/submillimeter Array (ALMA) to confirm the distance, which is 100
million light years further than GN-z11, the current record-holder for the
furthest galaxy.
Using the James Webb Space Telescope, the research team will soon once again
observe HD1 to verify its distance from Earth. If current calculations prove
correct, HD1 will be the most distant—and oldest—galaxy ever recorded.
The same observations will allow the team to dig deeper into HD1's identity
and confirm if one of their theories is correct.
"Forming a few hundred million years after the Big Bang, a black hole in HD1
must have grown out of a massive seed at an unprecedented rate," Loeb says.
"Once again, nature appears to be more imaginative than we are."
Reference:
A Search for H-Dropout Lyman Break Galaxies at z~12-16, arXiv:2112.09141
[astro-ph.GA]
arxiv.org/abs/2112.09141 ,
Accepted for publication in MNRAS Letters.
Are the newly-discovered z∼13 drop-out sources starburst galaxies or
quasars?, arXiv:2201.00823 [astro-ph.GA]
arxiv.org/abs/2201.00823 ,
Accepted for publication in ApJ.
Tags:
Space & Astrophysics
In case you need a new alternative for the Big Bang theory: https://zenodo.org/record/5635636#.Yk7le8hBx_A
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