Hubble captures images of two spiral galaxies: one flawless and one unusual.

      The spiral galaxy NGC 3596 is featured in this NASA/ESA Hubble Space Telescope Picture of the Week, which showcases images captured in six different wavelengths of light.

      You may be aware that galaxies are categorized into various types, based on their shapes. Elliptical galaxies are smooth and featureless, resembling large blobs of light. Then there are irregular galaxies, often warped into unusual shapes due to gravitational interactions when they collide or come close to other galaxies. Finally, there are the well-known spiral galaxies, such as the Milky Way, characterized by their long, arm-like structures extending from their centers.

      Not all spiral galaxies are alike, as evidenced by two recent images from the Hubble Space Telescope. The image above displays galaxy NGC 3596, which is a well-structured spiral galaxy. In contrast, the image below showcases galaxy Arp 184 (also known as NGC 1961), categorized as a peculiar spiral galaxy.

      This NASA/ESA Hubble Space Telescope image features the peculiar spiral galaxy Arp 184 or NGC 1961.

      A noticeable difference between the two images is their perspective from Earth: NGC 3596 is viewed head-on, giving it a particularly regular appearance. Meanwhile, we observe galaxy Arp 184 from an angle, resulting in a different appearance. Furthermore, Arp 184 is distorted, making it less than perfectly spiral in shape. Nevertheless, it is not a bland elliptical galaxy, which is why it was classified as a peculiar galaxy in the whimsically titled Atlas of Peculiar Galaxies, created by Halton Arp in 1966.

      In the image of Arp 184, the spiral arm that is nearest to us is broad and prominent, while there is no similarly large arm on the opposite side. The galaxy's asymmetry is what distinguishes it as unusual.

      In contrast, galaxy NGC 3596 has symmetrical arms of comparable size, which glow pink in this image to highlight regions of active star formation. What accounts for some galaxies exhibiting spiral arms while others do not, and why these arms display such various shapes and sizes? This remains an area of research for astronomers, but it is related to the density of stars in particular regions of the galaxy.

      “Researchers propose that spiral arms represent regions of high and low density instead of a tangible structure,” Hubble scientists describe. “As stars, gas, and dust orbit within a galaxy’s disk, they move in and out of the spiral arms. Similar to cars navigating a traffic jam, these materials slow down and clump together as they enter a spiral arm, then continue their journey through the galaxy.”

      For the last decade, Hubble has also been capturing images of our own solar system’s planets, particularly focusing on the outer planets under a project known as OPAL (Outer Planet Atmospheres Legacy). This initiative involves taking regular images of Jupiter, Saturn, Uranus, and Neptune, enabling scientists to monitor their changes over time.

      These gas giants and ice giants differ significantly from rocky Earth, yet they share phenomena like fluctuating weather, including massive storms that can be seen from space. A prime example is Jupiter's Great Red Spot, a colossal storm larger than Earth that has persisted for centuries.

      With all the enthusiasm surrounding the newly launched James Webb Space Telescope, it's easy to overlook the venerable Hubble. While Webb enhances certain aspects of astronomical observation with updated technology and increased detail, it is not a substitute for Hubble. A pair of new images illustrate this point: Both telescopes have captured the same galaxy, revealing different details and highlighting the value of utilizing both telescopes for scientific research.

      The galaxy NGC 2090 was imaged by Webb, which showcased the galaxy’s arms glowing red due to the swirling gas and dust rich in compounds called polycyclic aromatic hydrocarbons visible in the infrared spectrum. The blue hue in the galaxy's center indicates a region filled with young stars that shine intensely.

      In a recent Halloween-themed image combining data from the Hubble and Webb telescopes, a pair of galaxies, IC 2163 on the left and NGC 2207 on the right, appear to be drawing near and interacting, resembling an eerie face. Although the two galaxies are not colliding directly—one is merely passing in front of the other—the proximity has caused noticeable distortions. If you examine the galaxy on the left closely, you'll see how its spiral arms have elongated, likely due to the gravitational influence of the other galaxy. The bright red lines around the “eyes” reflect shock fronts formed by the collision of materials from each galaxy.