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  • Comets and their journeys around the Sun

    Comets are small Solar System bodies containing mixtures of ice, dust, and rocky material. When a comet approaches the Sun, some of its frozen material can become gas and carry dust away from the central body. This activity creates the extended appearance associated with a bright comet. Far from the Sun, the same object may be much less conspicuous and difficult to distinguish against the background of space.

    The solid central part of a comet is called its nucleus. Around an active nucleus, released gas and dust can form a diffuse region known as a coma. Material extending away from this region may produce tails. These visible structures are much larger than the nucleus itself. A photograph showing a long tail therefore does not indicate that the solid body has the same enormous dimensions.

    A comet’s tail is influenced by sunlight and the flow of particles from the Sun. It does not simply trail behind the comet in the way smoke might follow a moving vehicle. Gas-related and dust-related structures can respond differently and may point in slightly different directions. The appearance also depends on the geometry between the comet, the Sun, and the observer, so changes in a photograph can have more than one cause.

    Comets follow orbits with a wide range of shapes and timescales. Some return to the inner Solar System repeatedly on comparatively short schedules, while others make much longer journeys. A comet’s activity can change between visits as its surface and accessible material evolve. Astronomers therefore combine observations made at different times rather than assuming that every return will produce the same brightness or shape.

    The study of comets connects visible events in the sky with material preserved in small, cold bodies. Telescopes reveal motion and changing activity, while closer investigations can examine the nucleus and the particles it releases. Even a comet that looks like a simple bright streak is a complex object interacting with its environment. Following its changing appearance provides information about both the body itself and the conditions along its journey.

  • Whales: Giants of the Ocean

    Whales: Giants of the Ocean

    Whales are among the largest and most remarkable animals on Earth. These marine mammals live in oceans around the world, from warm tropical waters to the cold seas surrounding the poles.

    Life Beneath the Surface

    Although whales spend their lives in water, they breathe air through blowholes located on top of their heads. They must regularly return to the surface to breathe before diving again in search of food or traveling through the ocean.

    Whales are warm-blooded, give birth to live young, and nurse their calves with milk. A thick layer of fat called blubber helps protect them from cold water and stores energy during long migrations.

    Two Main Groups

    Whales are generally divided into baleen whales and toothed whales. Baleen whales filter small animals from the water using flexible plates inside their mouths. This group includes blue whales, humpback whales, and gray whales.

    Toothed whales use teeth to catch fish, squid, and other prey. Many of them also use echolocation, producing sounds and listening for returning echoes to understand their surroundings. Sperm whales, belugas, and orcas belong to this group.

    The Blue Whale

    The blue whale is the largest known animal to have ever lived. An adult can grow longer than a city bus and weigh well over one hundred tonnes. Despite its enormous size, it feeds mainly on tiny crustaceans called krill.

    Communication and Migration

    Whales communicate using clicks, whistles, pulses, and complex songs. Some sounds can travel across great distances underwater. Humpback whales are especially famous for their long, patterned songs.

    Many species migrate thousands of kilometres each year. They often feed in cold, nutrient-rich waters before traveling to warmer regions where they mate and give birth.

    Protecting Whales

    Commercial hunting once caused severe declines in many whale populations. Today, whales also face threats from fishing gear, ship collisions, underwater noise, pollution, and changes to ocean ecosystems.

    Conservation programs, safer fishing practices, protected habitats, and international cooperation can help whale populations recover. Protecting whales also supports healthier oceans because these animals play an important role in marine food webs and nutrient cycles.