New Telescope Reveals Sonic Boom Effects of Colliding Galaxies in Stephan’s Quintet
A new astronomical instrument has successfully observed the speeds of colliding galaxies in Stephan’s Quintet. This study shows how one galaxy is crashing into the others at an impressive speed, compared to the sonic boom from a jet fighter breaking the sound barrier.
Stephan’s Quintet consists of five galaxies, as identified by Édouard Stephan in 1877. At that time, he did not know these were galaxies outside the Milky Way, but he recognized their significance. Four of these galaxies interact and are expected to merge into one supergalaxy in the future. Currently, one galaxy, known as NGC 7318b, is moving through the others at relative speeds of 0.3 percent of the speed of light—much faster than the Sun orbits the Galactic Center.
While stars are typically small compared to the vast distances between them, the gas in these galaxies still interacts. Gas clouds collide when there is a significant amount of unturned gas, as seen in Stephan’s Quintet. Dr. Marina Arnaudova from the University of Hertfordshire explained that the collision creates a powerful shockwave, similar to a sonic boom, as NGC 7318b moves at over 2 million mph (3.2 million km/h).
Stephan’s Quintet has fascinated astronomers because it showcases a site of past galaxy collisions, resulting in a debris field. This group of galaxies was a perfect target for the new William Herschel Telescope Enhanced Area Velocity Explorer (WEAVE). This instrument operates alongside the 4.2-meter optical William Herschel Telescope in La Palma.
As the shockwave travels through cold gas pockets, it does so at hypersonic speeds. This shockwave is fast enough to ionize atoms, creating a glowing trail of charged gas. Arnaudova noted that the shockwave travels more than 25 times the speed of sound in gas. As the shock moves into hotter plasma, it slows down, dropping to about four times the speed of sound and producing radio waves, which can be detected by instruments like the Very Large Array.
How do shockwaves from high-speed galaxy interactions contribute to star formation in merging galaxies?
Interview with Dr. Marina Arnaudova: Insights on NGC 7318b and the Stellar Dynamics of Stephan’s Quintet
News Directory 3: Today, we’re excited to have Dr. Marina Arnaudova from the University of Hertfordshire joining us to discuss the fascinating phenomena occurring in Stephan’s Quintet, particularly the recent observations of the galaxy NGC 7318b and its remarkable collision with its neighbors. Thank you for being here, Dr. Arnaudova.
Dr. Arnaudova: Thank you for having me!
News Directory 3: To start, could you explain the significance of Stephan’s Quintet and why it’s so intriguing to astronomers?
Dr. Arnaudova: Absolutely. Stephan’s Quintet is a group of five galaxies located in the constellation Pegasus, and it was identified by astronomer Édouard Stephan in 1877. What makes it particularly significant is that four of these galaxies are gravitationally interacting, which presents a unique opportunity for studying galaxy formation and the dynamics of cosmic collisions. They are expected to merge into a single supergalaxy in the future, providing insights into the evolutionary processes of galaxies.
News Directory 3: Recently, you and your team made remarkable observations of NGC 7318b. Can you describe what was discovered and the speeds involved?
Dr. Arnaudova: Our observations were made using advanced astronomical instruments, which enabled us to detect the immense speed at which NGC 7318b is moving—over 2 million miles per hour, or about 3.2 million kilometers per hour. This speed is approximately 0.3 percent of the speed of light. Such velocities are striking, and they produce shockwaves akin to sonic booms created by jet fighters when they break the sound barrier. This is a critical aspect of understanding the interactions within Stephan’s Quintet.
News Directory 3: How do these high speeds affect the gas dynamics within the galaxies?
Dr. Arnaudova: The high velocity of NGC 7318b leads to significant interactions between the gas clouds of the galaxies involved. As these gas clouds collide, they trigger turbulence and shockwaves, which can compress the gas and potentially lead to new star formation. These interactions are vital for understanding how gas is distributed and how it influences star formation within these merging galaxies.
News Directory 3: It sounds like these interactions can have a profound effect on the future of these galaxies. What implications do your findings have for our understanding of galaxy evolution?
Dr. Arnaudova: Our findings provide crucial insights into the processes that govern galaxy mergers and the resulting dynamics. By studying how NGC 7318b interacts with the other galaxies in Stephan’s Quintet, we can better understand not only the immediate effects of such collisions but also the long-term evolution of galaxies in the universe. This research contributes to a broader understanding of how structures in the universe form and evolve over time.
News Directory 3: what do you hope to achieve with future studies in this region of space?
Dr. Arnaudova: We aim to continue our observations to capture more data on these dynamic interactions, focusing on different wavelengths. This will help us to uncover even more details about the gas dynamics and star formation activities occurring in the aftermath. The study of Stephan’s Quintet acts as a natural laboratory for understanding galaxy evolution, and we are committed to unraveling these cosmic mysteries.
News Directory 3: Thank you, Dr. Arnaudova, for sharing your remarkable insights into NGC 7318b and the enigmatic world of Stephan’s Quintet. We look forward to your future discoveries in this exciting field!
Dr. Arnaudova: Thank you for having me! It’s a pleasure to share this research with a wider audience.
Combining observations from WEAVE with other telescopes, including the James Webb Space Telescope (JWST), allowed researchers to analyze the shock’s location within the galaxies more precisely.
The interactions of the Quintet provide insights into how the Milky Way will merge with smaller orbiting galaxies. By observing these live collisions, scientists understand the Milky Way’s historical consumption of smaller galaxies. Furthermore, these collisions stimulate star formation from gas that might have remained unformed for billions of years. Most current star formation occurs in an area called SQ-A, located at the northern end of the shock, visible as a blue region filled with hot young stars.
The original five galaxies in Stephan’s Quintet include a bright galaxy that is much closer to us and not currently involved in the collisions. Another smaller galaxy, NGC 7320c, is also part of the Quintet and has influenced the dynamics of its fellow galaxies in the past.
The study detailing these findings is published in the Open Access journal, Monthly Notices of the Royal Astronomical Society.