ALMA | NRAO | ESO | NAOJ | 2017 Jun 05
Companion Star Provides Chilling Power of ‘Coldest Object in the Universe’
[img3="Composite image of the Boomerang Nebula, a pre-planetary nebula produced by a dying star. ALMA observations (orange) showing the hourglass-shaped outflow, which is embedded inside a roughly round ultra-cold outflow. The hourglass outflow stretches more than three trillion kilometers from end to end (about 21,000 times the distance from the Sun to the Earth), and is the result of a jet that is being fired by the central star, sweeping up the inner regions of the ultra-cold outflow like a snow-plow. The ultra-cold outflow is about 10 times bigger. The ALMA data are shown on top of an image from the Hubble Space Telescope (blue).An ancient, red giant star in the throes of a frigid death has produced the coldest known object in the cosmos — the Boomerang Nebula. How this star was able to create an environment strikingly colder than the natural background temperature of deep space has been a compelling mystery for more than two decades.
Credit: ALMA (ESO/NAOJ/NRAO); NASA/ESA Hubble; NRAO/AUI/NSF"]https://public.nrao.edu/wp-content/uplo ... 4x1024.jpg[/img3][hr][/hr]
The answer, according to astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA), may be that a small companion star has plunged into the heart of the red giant, ejecting most the matter of the larger star as an ultra-cold outflow of gas and dust.
This outflow is expanding so rapidly — about 10 times faster than a single star could produce on its own — that its temperature has fallen to less than half a degree Kelvin (minus 458.5 degrees Fahrenheit). Zero degrees Kelvin is known as absolute zero, the point at which all thermodynamic motion stops.
The ALMA observations enabled the researchers to unravel this mystery by providing the first precise calculations of the nebula’s extent, age, mass, and kinetic energy. ...
The Boomerang Nebula is located about 5,000 light-years from Earth in the constellation Centaurus. The red giant star at its center is expected to shrink and get hotter, ultimately ionizing the gas around it to produce a planetary nebula. Planetary nebulae are dazzling objects created when stars like our sun (or a few times bigger) shed their outer layers as an expanding shell near the end of their nuclear-fusion-powered life. The Boomerang Nebula represents the very early stages of this process, a so-called pre-planetary nebula. ...
The Coldest Place in the Universe: Probing the Ultra-cold Outflow and Dusty Disk in the Boomerang Nebula - R. Sahai et al
- Astrophysical Journal 841(2):110 (2017 Jun 01) DOI: 10.3847/1538-4357/aa6d86
arXiv.org > astro-ph > arXiv:1703.06929 > 20 Mar 2017 (v1), 26 May 2017 (v2)
- Astrophysical Journal 777(2):92 (2013 Nov 10) DOI: 10.1088/0004-637X/777/2/92
arXiv.org > astro-ph > arXiv:1308.4360 > 20 Aug 2013