First calculate the exact amount of oxygen in a distant galaxy

The amount of oxygen in the galaxy is the key to understanding problems since the galaxy was formed throughout its history.

Astronomers at UCLA have just made the first accurate measurement of oxygen in a distant galaxy.Oxygen , the third richest chemical element in the universe, is made up of stars and emitted into gas in an interstellar environment when stars die.

"This is one of the most distant galaxies we can measure the exact amount of oxygen. This galaxy was formed 12 billion years ago. Observations were made at WM Keck Observatory, Mauna Kea, Hawaii Islands , " said astronomer Professor Alice Shapley of UCLA.

"This galaxy is called COSMOS-1908 . Once we know the galaxy's oxygen level, we have taken an important step towards other measurements to better understand the star density of galaxies. distant is formed when the universe is only a few billion years old, " added Shapley.

COSMOS-1908 contains about 1 billion stars, while our Milky Way has about 100 billion stars; some other galaxies in the universe contain more stars than that. In addition, COSMOS-1908 contains only about 20% oxygen compared to the amount of oxygen observed from the Sun.

Typically, astronomers rely on indirect and inaccurate techniques to assess the oxygen abundance of distant galaxies. But in this study, astronomers at UCLA use a direct measurement.

The COSMOS-1908 galaxy is in the middle of the picture (white arrow) along with other galaxies near the Earth.(Photo: Hubble Space Telescope).

Closed galaxies are usually much brighter and we have a good way to determine the amount of oxygen there. Although the difficulty will increase when studying distant galaxies, COSMOS-1908 is a perfect exception to the method.

Comparing the amount of oxygen known to a galaxy with the model of the galaxy to be built, will tell us how that galaxy was formed and the history of forming stars within them.

The amount of oxygen in a galaxy is determined primarily by three factors: the amount of oxygen from the massive stars that end their lives with supernova explosions - a phenomenon that is common in the early universe. when the rate of new stars is significantly higher than today; the amount of oxygen released from the galaxy by "super wind", these winds push oxygen and other gases from the interstellar environment out of the galaxy at a rate of thousands of miles per hour; The amount of pristine gas penetrates into the galaxy from the intergalactic medium, which does not contain much oxygen.

If we can measure the amount of oxygen in the galaxy, it will tell us in detail the galactic formation and development processes, why each galaxy has a different structure, or galaxies handed over. How do things change between intergalactic environments?

Mr. Shapley expects oxygen calculations to confirm whether the "super wind" is really important in developing the galaxy. Because these intergalactic winds are ejected from large galaxies and into other galaxies.

The researchers used an extremely advanced and sophisticated device called Infrared Multi-Object Probe Spectrophotometer (MOSFIRE) placed on the Keck telescope at Keck Observatory. This 5-ton tool is designed to look at the most distant and faint galaxies.

MOSFIRE collects visible photons from celestial bodies that are billions of light years away with a wavelength that is stretched or called a red shift through infrared light. Due to the finite speed of light, MOSFIRE is actually looking at the past billions of years ago, studying the incident that happened in the past, when the first light rays surpassed billions of years away and touched the lane Earth.

MOSFIRE is another type of spectrophotometer, which distinguishes light from celestial bodies into a spectral range with separate wavelengths (colors), indicating the specific energy level emitted at each wavelength. The spectral range allows astronomers to determine the chemical composition of the galaxy, in particular the various chemical elements such as oxygen, carbon, iron or hydrogen that give different wavelengths.

To analyze the chemical composition of COSMOS-1908, astronomers analyzed a special wavelength from this galaxy that is very sensitive to oxygen. MOSFIRE is really a great device.