Comet Nishimura, named after Hideo Nishimura, the Japanese photographer who first spotted it, is a newly discovered comet which is a green in color, half-mile in diameter ball of ice – will reach its closest point to Earth tomorrow morning. Look LOW on the horizon after 5:30am / before the sun rises.
Mr. Nishimura captured the comet on Aug. 12 while imaging the sky before sunrise with a digital camera — the third comet he has discovered. He reported the sighting to the Central Bureau for Astronomical Telegrams, which alerted astronomers around the world.
Don’t blink because if you don’t see it over the next couple days, it will be too late! Moving at a pace of nearly a quarter million miles per hour, it will not be back in our skies for another 400 years.
Comets, often described as “dirty snowballs” or “icy dirtballs,” are celestial bodies that orbit the Sun. Composed primarily of water ice, dust, and other volatile compounds, these space wanderers provide a unique glimpse into the conditions present in the early solar system. Unlike planets, which are visible for long periods and can be studied in detail, comets often appear unexpectedly and may only be discovered at the last minute. This article explores the nature of comets and delves into the reasons why these mysterious objects can sneak up on us so suddenly.
What are Comets?
A comet is a small Solar System body that, when in proximity to the Sun, heats up and begins to outgas, displaying a visible coma or atmosphere and sometimes a tail. These phenomena are a result of the Sun’s radiation causing the comet’s volatile compounds to vaporize and form a cloud of particles that are swept back by the solar wind.
Anatomy of a Comet
A comet’s core, known as the nucleus, is a solid center made up of a mixture of water ice, frozen gases, and rocky material. When a comet gets close to the Sun, the heat causes the ices to sublimate, transforming directly from a solid to a gas. This gas forms a glowing coma around the nucleus. Sunlight and solar wind can push this material into a tail that points away from the Sun, creating the iconic “shooting star” appearance.
Types of Comets
Comets are generally categorized based on the lengths of their orbits. Short-period comets, like Halley’s Comet, take less than 200 years to complete an orbit around the Sun. Long-period comets, on the other hand, take more than 200 years and can even have orbital periods that span thousands of years. Some comets are only seen once and then escape the gravitational pull of the Sun, becoming what are known as “hyperbolic comets.”
Why Are Some Comets Discovered Late?
Unpredictable Orbits
Long-period comets, and particularly those coming from the Oort Cloud—a spherical shell of icy objects located about 50,000 to 200,000 astronomical units from the Sun—have highly unpredictable orbits. Their paths can be influenced by gravitational interactions with other celestial bodies, making their appearances difficult to anticipate.
Dim Visibility
Comets are notoriously difficult to spot when they are far from the Sun because they do not emit light and are often too dim to be seen against the backdrop of space. They only become visible when they get close enough to the Sun for their volatile materials to vaporize, creating a coma and possibly a tail.
Limited Sky Surveys
While technology for sky surveys has improved, our telescopic coverage of the sky is not comprehensive. Budget constraints and the vastness of the sky make it challenging to detect all comets in a timely manner.
Surprise Encounters
Some comets are discovered only when they are already quite close to Earth. For instance, Comet Hyakutake was discovered just two months before its closest approach to Earth in 1996. Comet Siding Spring was discovered in January 2013 and had a close encounter with Mars in October 2014, providing very little lead time for detailed study or preparation for potential impacts.
Comets are fascinating celestial bodies that offer a wealth of information about our solar system’s history and composition. However, their unpredictable orbits, dim visibility, and the limitations of our observational capabilities mean that they can often go unnoticed until the last minute. While this makes studying them a challenge, it also adds to the mystique and excitement that these cosmic visitors bring with them as they journey through our solar system.
