(CN) — Scientists have discovered what is likely a recently formed galaxy, one with the lowest oxygen abundance on record, thanks to data obtained by Japan’s Subaru Telescope and innovative machine learning processes.
Most observed galaxies are mature and young ones are few and far between. So this newly discovered galaxy, designated HSC J1631+4426, may provide useful data that could guide astronomers’ understanding of how galaxies form and evolve over time.
“To find the very faint, rare galaxies, deep, wide-field data taken with the Subaru Telescope was indispensable,” said Takashi Kojima, a University of Tokyo physicist and lead author of a study published Friday in The Astrophysical Journal. In all, 21 scientists contributed to the findings.
The Subaru Telescope, named for the open star cluster that English speakers call the Pleiades, is the National Astronomical Observatory of Japan’s flagship instrument. Perched near the summit of Hawaii’s dormant Maunakea volcano, the telescope is situated above the cloud layer to collect optical and infrared data unhindered through its massive 26.9-foot aperture, among the largest in the world.
This large optic collects images at a resolution more than 1,000 times that collected by the human eye, which means data collected by the telescope can include as many as 40 million objects at a time.
To sift through this immense amount of information, Kojima and his team used machine learning methods to identify early-stage galaxies in the data. By showing their computer program the galaxy colors predicted by theoretical models, the machine could present the researchers with only the galaxies early in their formation. It presented 27 candidates.
The researchers chose four of these galaxy candidates and sought to determine their elemental abundance ratios. An abundance ratio describes the ratio of elements in a celestial body relative to the elements’ ratio in the Sun, expressed as a logarithm. This gives scientists a way of comparing the relative abundance of elements across the universe.
They found that the young galaxy, which is located in the Hercules constellation and lies 430 million light years away from us, has an oxygen abundance of only 1.6% of the Sun’s. That is the lowest oxygen value ever reported for a galaxy.
“What is surprising is that the stellar mass of the HSC J1631+4426 galaxy is very small, 0.8 million solar masses,” said Masami Ouchi, a University of Tokyo cosmologist and professor at the National Astronomical Observatory of Japan. “This stellar mass is only about 1/100,000 of our Milky Way galaxy, and comparable to the mass of a star cluster in our Milky Way.”
All this points to the youth of the galaxy, which is very likely in an early stage of its evolution. That’s something of a surprise given the age of the universe, which has had at least 11 billion years to birth galaxies.
As the universe’s expansion continues to accelerate, gravity may not be capable of birthing new galaxies. In a press release, the researchers wondered whether HSC J1631+4426 may be among the last galaxies to form in the history of the cosmos.