The Seyfert galaxy NGC 1275 is actually two galaxies that are colliding. Images of \(\mathrm{NGC} 1275\) show a number of globular clusters with a distinctive blue color. Explain how this color shows that these clusters formed relatively recently, perhaps as a result of the collision.

Stars within a cluster can collectively tell a story about their origin and journey in time. This story often begins with the color of the cluster, which acts as a cosmic clue to their age. A cluster that appears blue indicates the presence of particularly hot and massive stars. Such stars, known for burning brighter and faster than their cooler counterparts, are short-lived on the astronomical timescale, with life spans of only a few million years.

When astronomers observe blue star clusters, they're witnessing the celestial equivalent of a 'young adult' phase in cosmic terms. This is because, shortly after star clusters form, they contain a multitude of these massive, bright, and blue stars. As time progresses, the largest stars exhaust their nuclear fuel rapidly and explode as supernovae, leaving behind stars that are cooler and emit less blue light. Consequently, older star clusters often have a redder hue, because they are populated by these cooler stars that have lived longer and burned through their fuel at a slower pace. Thus, the striking blue color observed in the star clusters of NGC 1275 signals that we are looking at a relatively juvenile star group.

As galaxies cruise through the cosmos, sometimes their paths cross. This event, far from a gentle encounter, is a cataclysmic collision that can trigger a spectacular birth of stars, known as a starburst. When galaxies like NGC 1275 interact, their gaseous components intermingle, compress, and collapse under gravity, forming new stars at a frenzied pace.

The compressed gas clouds in colliding galaxies are incredibly dense, making them fertile grounds for star creation. The force of the collision can cause gas to funnel into the galactic center or into regions where star formation was previously less active. This sudden rush of activity spawns massive stars that shine brightly, contributing to the bluish tints we see in the young cluster populations. These galactic encounters are pivotal chapters in the galaxies' histories, and their scars are worn openly in the form of new stars, altering the galaxies' structure, dynamics, and stellar census.

In the grand tapestry of the cosmos, stars are not all alike; they come in many colors, from the deep reds of cooler stars to the brilliant blues of the hottest ones. This spectrum of starlight is intimately tied to temperature, governed by the principles of black body radiation.

The surface temperature of a star determines the color of light it emits most intensely. Hotter stars, with temperatures ranging from 10,000K to 50,000K, emit more light in the blue and ultraviolet part of the electromagnetic spectrum. Conversely, cooler stars, having temperatures around 3,000K to 5,000K, shine with a redder or orangish glow. This relationship is a fundamental concept in astrophysics, known as Wien's Displacement Law, which shows that the peak emission of a star shifts towards shorter wavelengths (blue) as temperature increases and towards longer wavelengths (red) as it decreases. Thus, by deducing the color of a star cluster, astronomers can infer the approximate temperature range of its stars, offering a glimpse into the cluster’s constituents without probing each star individually.