#extragalactic astronomy

[sklogw]

Two Hubble images of interacting galaxy pair IC1623. The first one is a composition of optical and infrared images. The second one combines observations from eight different filters with wavelengths ranging from infrared to ultraviolet.

At this stage of their collision, the two galaxies are still relatively separate, but eventually they'll merge into a single object. The merging process will also trigger intense star formation, causing the resulting galaxy to be classified as a starburst.

The final stage of a merger of two large galaxies of similar size such as this pair is believed to be a giant elliptical galaxy.

[skycrorg]

The article examines the transition from M100 to NGC 7331, highlighting their structural similarities and significance in the study of spiral galaxies. It emphasizes how both systems illustrate key stages in galactic morphological evolution. Additionally, they serve as natural laboratories for understanding stellar dynamics and the development of spiral arms.

From M100 to NGC 7331: A multiband study and physical parameters in nearby galaxies

[sharmaheena850]

Milky Way still in thrall of a 900 million-year-old cosmic collision

The Milky Way galaxy is still enduring the effects of a near collision that took place sometime in the past 300-900 million years and set millions of stars moving like ripples on a pond, scientists say.

The European Space Agency (ESA)'s star mapping mission, Gaia, discovered the pattern of movement in stars in the Milky Way disc -- one of the major components of our galaxy.

The pattern was revealed because Gaia not only accurately measures the positions of more than a billion stars but also precisely measures their velocities on the plane of the sky.

For a subset of a few million stars, Gaia provided an estimate of the full three-dimensional velocities, allowing a study of stellar motion using the combination of position and velocity, which is known as 'phase space'. Read Complete Article

Article Source >> Business Standard

[theaggiephysicist-blog-blog]

PhysOrg.com

NGC 5907 is a spiral galaxy lying in the Dragon constellation, showing extraordinary large loops and currents of stars in its surrounding halo. According to researchers, it could have been formed through a gigantic collision of galaxies, 8 to 9 billion years ago. Six scientists of the Observatoire de Paris, CNRS, Chinese Academy of Sciences, National Astronomical Observatories of China and Aix-Marseille Universite propose this scenario on the basis of simulations with 200 000 to 6 million particles. These up-to-date calculations, that include gas hydrodynamics, are able to reproduce in a film the formation of NGC5907 and its surrounding gigantic loops of matter. Results appeared on the cover of the online edition of Astronomy and Astrophysics, the 13 February 2012. They provide an important test for cosmological scenarios.

The pre-print paper of this article is titled:  "Loops formed by tidal tails as fossil records of a major merger"