In the southern sky, approximately 95 million light-years from Earth, lies a remarkably unique spiral galaxy—NGC 7098. Featuring two distinct ring structures and a bright central region housing two sets of stellar bars (one large, one small), it is frequently highlighted as a textbook example of a double-barred spiral galaxy. For astronomy enthusiasts beginning to learn about galaxy classification, NGC 7098 serves as an ideal target to understand barred spiral galaxies, galactic rings, spiral arms, and star-forming regions. Although it cannot be observed directly from most of North America and Europe, high-resolution imagery captured by the European Southern Observatory's (ESO) Very Large Telescope allows us to clearly examine the intricate and orderly internal structures of this distant galaxy.

What Type of Galaxy Is NGC 7098?

NGC 7098 is a spiral galaxy located in the direction of the constellation Octans, approximately 95 million light-years from Earth.

As seen from Earth, it has an apparent magnitude of around 11, placing it well beyond the limit of naked-eye human vision. However, what draws attention to NGC 7098 is not its brightness, but its unique geometry.

Ordinary spiral galaxies typically feature a central bulge with spiral arms extending outward, while barred spiral galaxies show a bar-like structure made of dense concentrations of stars passing through their central region. NGC 7098 possesses not only a bar, but a far more complex system featuring both double bars and double rings.

In images captured by the ESO Very Large Telescope, a clear ring structure is visible surrounding the bright core, encircled further out by a second, larger outer ring. Looking closer toward the center, two distinct bar-like structures of different scales can be resolved.

This intricate architecture gives NGC 7098 a striking visual appearance—unusually symmetrical and almost engineered in its precision.

What Is a Barred Spiral Galaxy?

To understand NGC 7098, it helps to first understand barred spiral galaxies.

The primary visual feature that sets a barred spiral galaxy apart from an ordinary spiral galaxy is the presence of a distinct bar-shaped stellar structure across its center. Rather than extending directly from a round core, the spiral arms usually trail outward from near opposite ends of this central bar.

This configuration is quite common across the cosmos.

Our own Milky Way is a barred spiral galaxy. The central region of the Milky Way harbors a central bar composed of billions of stars, though because we reside inside the galaxy, we cannot view its complete architecture from the outside as we do with distant galaxies.

A central bar is more than just a visual feature; it influences the orbital motion of stars and interstellar gas within the galaxy and can actively drive gas inward toward the core. Studying stellar bars is therefore essential for understanding how galaxies evolve over cosmic time.

What Is a "Double-Barred Galaxy"?

What makes NGC 7098 particularly special is that it harbors more than just a single bar structure.

Nested inside its larger primary bar lies a smaller, secondary inner bar. Galaxies featuring these inner and outer bar systems are known as double-barred galaxies.

The inner and outer bars do not necessarily align along the same axis, and they can differ in scale and dynamical behavior.

From an astronomical research perspective, this structure is exceptionally valuable. Galaxies are not static stellar disks; they are dynamic systems where hundreds of millions—or even billions—of stars, alongside gas and dust, orbit under mutual gravitational influence.

Double-barred structures serve as natural laboratories for studying mass transport, secular evolution, and stellar orbital dynamics within the central regions of galaxies.

Why Does NGC 7098 Have Two Rings?

In addition to its double bars, NGC 7098's most striking feature is its double-ring structure.

ESO imagery reveals two prominent ring-like regions—one inner, one outer. However, these structures should not be pictured as solid, isolated features floating around the galaxy like the rings of Saturn.

Instead, they are tightly linked to NGC 7098's intrinsic spiral architecture.

The galaxy's spiral arms are wound so tightly around the central region that, from our line of sight, they give the strong visual impression of closed rings. An inner ring encircles the central bar region, while the outermost structures trace a significantly larger outer ring.

Consequently, NGC 7098 serves as a clear, textbook case of a ringed barred spiral galaxy: the bar, spiral arms, and rings are not unrelated features, but distinct components that emerged from the dynamical evolution of a single, massive gravitational system.

Why Do Young Stars Appear in the Ring Regions?

When examining high-resolution imagery of NGC 7098, a clear distinction between its ring structures and its central region becomes apparent.

Galactic rings and spiral arm regions typically harbor rich concentrations of star-forming interstellar gas. As gas becomes compressed under favorable conditions, dense clouds collapse to spawn clusters of new stars.

Consequently, key signatures of active star formation are prominently mapped throughout the ring structures of NGC 7098.

By contrast, the galaxy's central region appears much smoother, showing significantly reduced ongoing star-forming activity compared to the surrounding rings.

It is important to note that a lack of visible dust lanes does not simply equate to an absence of star formation. The star-forming process relies on multiple factors, including the supply, density, and dynamical environment of cold molecular gas. While dust lanes help astronomers map out the internal interstellar medium of a galaxy, they are not the sole factor determining where new stars can form.

How Big Is NGC 7098?

NGC 7098 has an estimated diameter on the order of 150,000 light-years.

For scale, the Milky Way's stellar disk is typically estimated to span over 100,000 light-years across, making NGC 7098 a galaxy of considerable size.

However, because it lies approximately 95 million light-years from Earth, it appears in our sky as a small deep-sky target.

A distance of 95 million light-years also means that the image of NGC 7098 we see today captures the galaxy as it was roughly 95 million years ago.

When that light left the galaxy, life on Earth was vastly different from today. After nearly 100 million years of traveling through cosmic space, those photons finally reached Earth to be captured by modern ground-based giant telescopes.

This is one of the most compelling aspects of observing distant galaxies: telescopes allow us not only to peer deeper into space, but to look back into cosmic time.

Can You See NGC 7098 from North America?

For beginner astronomy enthusiasts in North America, this is a critical detail to keep in mind.

NGC 7098 is located in the constellation Octans at a declination of approximately −75°, placing it extremely close to the South Celestial Pole. Consequently, it never rises above the horizon from the vast majority of the United States and Canada.

Even if you possess a large amateur telescope, you cannot overcome the horizon limit imposed by the curvature of the Earth.

This is not a matter of whether the object is bright enough, but a simple function of celestial coordinates and observer latitude.

Only observers situated at suitable latitudes in the Southern Hemisphere—such as Australia, South Africa, or southern South America—will find NGC 7098 reaching favorable altitudes for observation.

Therefore, for beginners in North America, the most practical way to explore NGC 7098 is not through visual stargazing, but by studying high-resolution data captured by professional observatories.

How Did ESO Capture NGC 7098?

The iconic imagery of NGC 7098 comes from the European Southern Observatory's (ESO) Very Large Telescope (VLT).

Located at the Paranal Observatory in Chile, the VLT obtained the raw data used to construct ESO's published portrait of NGC 7098 using its FORS instrument (FOcal Reducer and low dispersion Spectrograph).

In these high-definition captures, beyond the double rings and central double bars, specialized features known as ansae (from the Latin for "handles") become clearly visible.

Appearing as small, bright structural handles at opposite ends of the central region, ansae represent local concentrations of higher stellar density. Details like these underscore how real-world galactic architectures are far more intricate than the simplified "core plus spiral arms" diagrams found in introductory textbooks.

Why NGC 7098 Is Worth Studying for Beginners

While NGC 7098 may not be a practical deep-sky target for North American beginners to seek out with a backyard telescope, it serves as an exceptional case study for learning galaxy morphology.

Through this single object, one can grasp fundamental concepts including spiral galaxies, barred spiral galaxies, double-bar structures, galactic rings, spiral arms, star-forming regions, and galactic dynamics.

More importantly, it helps novice observers build a essential worldview: galaxies are not static collections of stars.

Under the influence of gravity, stars, gas, and dust engage in continuous, long-term motion—giving rise to central bars, spiral arms, and ring systems as products of this complex dynamical evolution. The NGC 7098 we observe today is merely a single snapshot in the long, ongoing evolution of a massive cosmic system.

Understanding Double-Barred Spiral Galaxies Through NGC 7098

NGC 7098 is a unique spiral galaxy located approximately 95 million light-years from Earth in the southern constellation Octans. Its most striking features are the double-ring structure surrounding its bright core and the nested double-bar system at its center.

For those newly entering the study of astronomy, NGC 7098 provides a exceptionally clear real-world case study to understand barred spiral galaxies, double-barred configurations, the mechanics behind galactic rings, and active star formation along spiral arms.

Although direct visual observation of NGC 7098 is impossible from most of North America, high-resolution data from the ESO Very Large Telescope allows us to analyze the complex structure of this distant system in detail. The next time you examine a photograph of a spiral galaxy, take a moment to inspect its center for a bar, check if its spiral arms wind into closed rings, and note where its star-forming regions are concentrated—a foundational step in learning to identify distinct galaxy morphologies and classifications.