April 13, 2024

New star system discovered orbiting our galaxy, the Milky Way • Earth.com

A team of astronomers from Yale and the University of Victoria has made a surprising discovery – UMa3/U1 – the faintest star system ever observed orbiting our galaxy, the Milky Way.

Nicknamed Ursa Major III / UNIONS 1 (UMa3/U1), it is an incredibly dim and ancient group of stars located 30,000 light-years away in the constellation Ursa Major (which contains Ursa Major).

UMa3/U1 hiding in plain sight

UMa3/U1 was invisible for a long time because it is incredibly weak and small. We’re talking about just 60 stars spanning about 10 light years across.

For comparison, a single light year is almost 6 trillion miles. Even with powerful telescopes, it would be like trying to spot a handful of dust particles floating under a spotlight.

Despite its small size, this little cosmic neighbor is quite close, just 30,000 light years from Earth. It resides in the constellation Ursa Major (which contains the Big Dipper).

Is UMa3/U1 a galaxy or a star cluster?

The main question astronomers have is this: is UMa3/U1 a true dwarf galaxy or is it a star cluster? The answer may come down to a mysterious and invisible substance – dark matter.

Galaxies are thought to be held together by the gravitational pull of dark matter – a type of matter we can’t see directly, but which scientists know exists due to its gravitational effects.

On the other hand, gravity alone usually binds stars together into star clusters, often without the help of dark matter.

However, the surprising spread of UMa3/U1 stars did not lead to their disintegration by the gravitational forces of the Milky Way. Could dark matter be the invisible glue that holds this cosmic relic together?

“The object is so insignificant that its long-term survival is very surprising,” explains Will Cerny, a Yale University graduate student involved in the study. “We might expect that the strong tidal forces of the Milky Way’s disk would have already destroyed the system, leaving no observable trace.”

UMa3/U1 as a galaxy

First, UMa3/U1 may be a true dwarf galaxy, an entity with an incredibly low amount of visible matter compared to what we typically observe in these galaxies.

This feature makes it an intriguing topic of study, as it suggests that UMa3/U1 may be predominantly composed of dark matter.

If UMa3/U1 is indeed a dwarf galaxy rich in dark matter, it could provide valuable information about the role of dark matter in the formation and evolution of galaxies.

It could support the theory that many of these dark matter-dominated galaxies exist but remain hidden from our view, potentially revolutionizing our understanding of the structure of the Universe.

star cluster

Alternatively, UMa3/U1 could be a star cluster on the verge of disintegration. This perspective portrays UMa3/U1 as a cosmic anomaly, a cluster of stars that has remained together for billions of years and is now possibly in its final stages of disintegration due to the gravitational forces of the Milky Way.

Observing such disintegration in real time would offer a unique opportunity to study the life cycle of star clusters and the dynamic processes involved in their evolution and dissolution.

If scenario one turns out to be true, it would be exciting evidence supporting our current leading theory of how the universe works – the Lambda Cold Dark Matter (LCDM) model.

This model suggests that when our galaxy formed, it attracted hundreds of smaller satellite systems that would still orbit it today.

UMa3/U1 Cosmic Ghost Hunt

“Whether future observations confirm or reject that this system contains a large amount of dark matter, we are very excited about the possibility that this object could be the tip of the iceberg – that it could be the first example of a new class of extremely complex objects. faint stellars that have escaped detection until now,” says Cerny.

The team used powerful telescopes in Hawaii, such as the WM Keck Observatory and the Canada-France-Hawaii Telescope (CFHT), to focus on this celestial mystery.

Now, more observations are needed to reveal the true nature of UMa3/U1.

More about our galaxy, the Milky Way

Our home, the Milky Way, is a majestic spiral galaxy more than 100,000 light years across. It contains around 200 to 400 billion stars, including our own Sun.

Structure and composition

The Milky Way has a distinct structure, with spiral arms extending from a central bulge. These arms, called Perseus, Sagittarius, Centauri and Cygnus, contain a mix of young, hot stars and older, cooler stars. The galaxy’s disk is also home to vast clouds of gas and dust, serving as a cradle for new stars.

At the heart of the Milky Way lies a supermassive black hole called Sagittarius A*. This cosmic giant, with a mass of more than 4 million suns, exerts a powerful gravitational influence on stars and the surrounding gas.

Astronomers are intensively studying this region to better understand the nature of black holes and their role in the evolution of galaxies.

The neighborhood of our solar system

The Sun resides in a relatively quiet corner of the Milky Way, about 27,000 light-years from the galactic center. The solar system is part of a local stellar neighborhood called the Local Bubble, a region of space characterized by a lower density of gas and dust compared to other parts of the galaxy.

The Milky Way contains a diverse set of stars, from old, metal-poor stars in the halo to younger, metal-rich stars in the disk. Astronomers classify these stars into different populations based on their age, chemical composition and location in the galaxy. Studying these populations helps us understand the formation and evolution of the galaxy.

The Milky Way is not alone in the cosmic void. It is part of the Local Group, a group of more than 50 galaxies held together by gravity.

The Andromeda galaxy, our largest galactic neighbor, is on a collision course with the Milky Way. In about 4.5 billion years, these two galaxies will merge, reshaping the cosmic landscape.

Fascination with the unknown

“This discovery could challenge our understanding of galaxy formation and perhaps even the definition of a ‘galaxy,’” explains Simon Smith, a graduate student in astronomy at the University of Victoria and the study’s principal investigator.

Whether a dwarf galaxy or a star cluster, UMa3/U1 reminds us of the vast secrets hidden in the cosmic darkness. And the thrill of discovery? Well, it shines brighter than ever.

The study is published in The Astrophysical Journal and ArXiv.org.


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