The Boomerang Nebula
Nebulae have always been sources of mystique to astronomers and scientists. A nebula is an interstellar cloud of ionized gases and dust, which can span to over hundreds of light years in diameter. Some of the notable nebulae include the Pillars of Creation in the Eagle Nebula, which was taken by the Hubble Telescope; this intriguing cloud is an astronomical celebrity due to its eerie resemblance with ghostly castles, looming specters… the list is endless. However, there is none as mysterious and fascinating as the Boomerang Nebula.
One of the coldest inhabited places on Earth is Oymyakon, Russia, where temperatures can drop to below -47 degrees Celsius. In 1983, the coldest air temperature dropped to -89.2 degrees Celsius at Russia’s Vostok Station in Antarctica. An unprepared human exposed to these temperatures would catch hypothermia within seconds! But that’s just on the Earth- the moon, the silvery orb we see hanging leisurely in the sky, can go to much lower temperatures. The bottom of shadowed craters on the south pole of our very own natural satellite can reach temperatures that can, incredibly, dip below Pluto’s, to about minus 240 degrees Celsius. But the Boomerang Nebula surpasses them all.
The average temperature of deep space, away from any burning star or mass, is about a glacial 270 degrees C; the reason most of deep space even has those few degrees of heat is attributed to the lingering presence of cosmic microwave background, which are the primordial remnants of heat and energy left over from the Big Bang. However, over 5000 light years from the Earth and approximately only 1 Kelvin in temperature, the Boomerang Nebula, also known as the Bow Tie Nebula, is known to be the coldest region in the natural universe. It is located in the extensive constellation Centaurus, which is a shining arrangement of stars in the southern sky containing the star closest to the Solar System- the Alpha Centauri. The Boomerang Nebula is said to be a pre-planetary nebula, which consists of layers of diffused gas that are expelled when a star reaches the last few stages of its life. At its center exists a white dwarf- an extremely compact source of luminosity- whose ultraviolet radiation and starlight reflect off and heat the dust grains, and serves as the cause behind the eerie, vibrant hues characteristic of the nebula. This frigid, mystifying mass derives its name from its double lobe shape, and can be compared to an ethereal, disarmingly symmetric hourglass. However, this configuration is actually an illusion, seeing that the cloud encircling the dying star is roughly spherical. The center appears so narrow because of an extremely dense lane of minuscule grains of dust that conceal certain portions of its equator. And despite its massive distance from our manmade satellites and telescopes, the Boomerang Nebula can be viewed due to the rays of light emitted by the star that are reflected off the hovering particles of dust.
The Boomerang Nebula was closely observed by an international group of scientists, who used the Atacama Large Millimeter-submillimeter Array in Chile to do so. They discovered that the Boomerang Nebula is so overwhelmingly cold since it’s actually reducing its own temperature as it grows outwards; the expansion motion of the ejected gas- traveling at an intense 164 kilometers per second- by the central star exerts a cooling effect on the entire system, thereby making it only a mere degree over the absolute zero. The prodigious rate at which the gas of the Boomerang Nebula is ousted is almost ten times faster than the speed of gas being discharged from similar stars. The nebula is cooled since huge amounts of energy are required to expand the gas, thus weakening the intensity of the shining star; in addition, gas cools at it expands (a principle that can be observed in air conditioners and refrigerators). And courtesy of the huge amounts of gaseous clouds suspended in the Boomerang Nebula, negligible amounts of the microwave cosmic radiation can penetrate and raise the overall temperature of the mass. Zero Kelvin is a temperature that can never be achieved, although scientists are attempting to recreate this scenario on the International Space Station in the Cold Atom Lab, but the celestial forces of nature have almost reached it.
In spite of the sheer distance of the Boomerang Nebula from the earth, this gargantuan, distinctive cloud can actually prove to be extremely useful in unraveling a variety of astral mysteries, such as those pertaining to the short transition of a red giant to a nebula. However, the Boomerang Nebula still remains an astronomical enigma. Astronomers and scientists are still trying to discern how a star as weak as that in the Boomerang Nebula can eject the gas at such powerful speeds, but have found no definite answer as yet.
The universe is a huge source of interest to everyone, due to the vast number of secrets that remain unexplored, just waiting to be untangled and clarified. And it is phenomena like the Boomerang Nebula, the coldest region in the universe known to mankind, that only add and intensify this distinguishing aura of mystery emanating from the wondrous heavens.
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