The Boomerang Nebula, the chilliest object ever discovered, is the coldest location in the cosmos. It may be found in the constellation Centaurus, around 5,000 light-years from Earth.
A young planetary nebula with a fading red giant star at its heart, the Boomerang Nebula is a reflecting cloud of dust and ionised gases. It was once a star similar to our sun, and in its final phases of life, it has been shedding its outer layers as predicted. However, it has been discovered that it is shedding mass at a rate 100 times that of other fading stars.
Furthermore, it is doing it at a staggering 100 billion times the speed of the sun. According to NASA, this has resulted in the core star losing approximately one-and-a-half times the mass of our sun during the last 1,500 years. And, since the gases are being ejected so quickly — at a speed of 101 miles per second (164 kilometres per second) — a lot of heat energy is being ejected as well.
The result is a tremendously frigid area of space, which is best conveyed by reiterating the thermodynamic temperature scale’s lowest limit: absolute zero. This is –273.15 degrees Celsius and –459.67 degrees Fahrenheit on the Celsius scale. How does the Boomerang Nebula fare in comparison?
The deep inner temperature of the Boomerang Nebula is a jaw-dropping –458 degrees Fahrenheit or –272 degrees Celsius, which means the Boomerang Nebula is only a degree Celsius above absolute zero. According to a website, this is nearly three times colder than the temperature recorded over Dome Fuji, Antarctica in 2010, which was a bone-chilling -199.8 degrees Fahrenheit (-93.2 degrees Celsius).
The temperature of the Boomerang Nebula is even lower than that of the cosmic microwave background (CMB), which remains after the Big Bang (-454.7 degrees Fahrenheit, -270.4 degrees Celsius). The Boomerang Nebula does, in fact, absorb the CMB’s radiation, which was rapidly noticed when the nebula was initially identified in 1980.
When astronomers Keith Taylor and Mike Scarrott started studying the nebula in 1980 with the Anglo-Australian ground-based telescope at the Siding Spring Observatory, they had no idea it would become the coldest location in the cosmos, but its boomerang-shaped form meant it had a fitting name.
At least, that’s how it seemed until the Hubble Space Telescope photographed it in better detail in 1998, revealing a closer resemblance to a bow tie or hourglass. However, astronomer Raghvendra Sahai was already hard at work in 1990, when he predicted the presence of cold areas in a study published in the Astrophysical Journal.
According to Sahai, the star’s wind might expand fast as it flowed outward, causing the temperature to drop drastically, thereby turning the star into a cosmic refrigerator. As a result, in 1995, a team led by Sahai used the Swedish-ESO Submillimetre Telescope in Chile (decommissioned in 2003) to test the idea on the Boomerang Nebula, leading to the discovery of the temperature.
Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile verified the temperature in 2013, but it was Sahai’s work published in the Astrophysical Journal in 2017 that offered more insight on what may have occurred.
Sahai’s research discovered that the low temperature was caused by rapid gas acceleration, but he also wanted to know why the expulsion was happening so quickly, thinking for the first time that it was a dying red giant.
A minor companion star might have collided with the red giant, according to Sahai, who works at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California.
“The only way to eject so much mass and at such extreme speeds is from the gravitational energy of two interacting stars which would explain the puzzles properties of the ultra cold outflow,” he said in a statement by the National Radio Astronomy Observatory.
Because air expands and cools more quickly through a small aperture, the fact that it ejects its outer layer from two small locations is equally crucial. The scientists’ next step is to look for additional such events that are even colder.
The central star in the Boomerang Nebula will ultimately become a white dwarf.