Skip to main content

How Does the Milky Way Compare to Other Galaxies?

The Milky Way is special because it is our home. No matter where we are on Earth we can see its arc of light overhead if the night is dark enough. But how similar is our galaxy to others? Is it an unusual spiral galaxy, or is it rather typical in the cosmos?

Before we had discovered exoplanets, astronomers generally thought our solar system was rather typical. Sure, there would be differences, but the general arrangement of rocky worlds close to the Sun and cold gas giants in the outer system made sense. However when we studied planetary systems we found ours was rather unusual. Most planets orbit red dwarfs, not sun-like stars, and large gas giants often orbit close to their star. Now that we have sky surveys of galaxies throughout the Universe, we can answer the same question of the Milky way, as a recent study shows.

The study is based on the Satellites Around Galactic Analogs (SAGA) Survey, which began collecting data in 2013. The goal of SAGA is to look at the small galaxies which orbit large galaxies. The team looked at 101 galaxies with masses similar to the Milky Way and found 378 satellite galaxies for them. Because of observational limits, this only covers satellites with a mass of about a million Suns or more. In this range our galaxy has four satellites. We know of many more, but most of them are below the mass cutoff.

This would seem to indicate that the Milky Way is rather typical. But then the team looked at those galaxies with a large companion, like the Large Magellanic Cloud we see in the southern hemisphere. For those galaxies the number of satellites is typically much larger than four. The Milky Way has an unusually low number of satellites. One reason for this may be that the Large Magellanic Cloud entered our sphere of influence rather recently on the cosmic timeline.

A second study based on the SAGA data looked at star formation in the satellite galaxies. It found that the closer a satellite is to the main galaxy the more likely it is to still be producing stars. This is similar to what we see among the Milky Way satellites. So it seems that while the Milky Way is a little unusual, it isn’t unique among galaxies of similar mass.

But it will always be our special spiral galaxy.

Reference: Mao, Yao-Yuan, et al. “The SAGA Survey. III. A Census of 101 Satellite Systems around Milky Way-mass Galaxies.” arXiv preprint arXiv:2404.14498 (2024).

Reference: Geha, Marla, et al. “The SAGA Survey. IV. The Star Formation Properties of 101 Satellite Systems around Milky Way-mass Galaxies.” arXiv preprint arXiv:2404.14499 (2024).

The post How Does the Milky Way Compare to Other Galaxies? appeared first on Universe Today.



from Universe Today https://ift.tt/iqD8EAv
via IFTTT
Labels:

Comments

Post a Comment

Popular posts from this blog

Researchers Match Up 12 Meteorites with the Near-Earth Asteroids They Came From

Every day meteoroids blast through our planet’s atmosphere to hit the ground as meteorites. A team of researchers in Italy traced twelve of them to progenitor asteroids that orbit in near-Earth space. Scientists treasure meteorites because they reveal information about their parent bodies. In an arXiv paper, two Italian researchers—Albino Carbognani and Marco Fenucci—analyze the characteristics of the parent bodies of 20 selected meteorites. They were able to track all but eight back to their parent asteroids. Based on their work, the pair says at least a quarter of meteorites come from collisions that happened in near-Earth space and not in the Main Belt. Meteorites from Near-Earth Asteroids: How They Got Here Many meteorites are chondritic, similar to asteroids in the Main Belt (or came from it). In their paper, the authors point out that progenitor meteoroids (including many that fall to Earth and become meteorites) formed millions of years ago following collisions between main-...
Post a Comment
Read more

JWST Takes a Detailed Look at Jupiter’s Moon Ganymede

Nature doesn’t conform to our ideas of neatly-contained categories. Many things in nature blur the lines we try to draw around them. That’s true of Jupiter’s moon Ganymede, the largest moon in the Solar System. The JWST took a closer look at Ganymede, the moon that’s kind of like a planet, to understand its surface better. Ganymede is basically a planet, except it doesn’t orbit the Sun. If it did orbit the Sun instead of Jupiter, it would be indistinguishable from a planet. It has a differentiated internal structure with a molten core that produces a magnetic field. It has a silicon mantle much like Earth’s, and has a complex icy crust with a deep ocean submerged beneath it. It has an atmosphere, though it’s thin. It’s also larger than Mercury, and almost as large as Mars. According to the authors of a new study, it’s an archetype of a water world. But even with all this knowledge of the huge moon, there are details yet to be revealed. This is especially true of its complex surface...
Post a Comment
Read more

What Blew Up the Local Bubble?

In our neighborhood of the Milky Way, we see a region surrounding the solar system that is far less dense than average. But that space, that cavity, is a very irregular, elongated shape. What little material is left inside of this cavity is insanely hot, as it has a temperature of around a million Kelvin. from Universe Today https://ift.tt/KvVDeiC via IFTTT
Post a Comment
Read more