ALMA returns to boomerang nebula: Companion star provides chilling power of 'coldest object in the universe'

June 5, 2017
This is a 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 Credit: ALMA (ESO/NAOJ/NRAO); NASA/ESA Hubble; NRAO/AUI/NSF

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.

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.

"These new data show us that most of the stellar envelope from the massive has been blasted out into space at speeds far beyond the capabilities of a single, red giant star, " said Raghvendra Sahai, an astronomer at NASA's Jet Propulsion Laboratory in Pasadena, California, and lead author on a paper appearing in the Astrophysical Journal. "The only way to eject so much mass and at such extreme speeds is from the gravitational energy of two interacting , which would explain the puzzling properties of the ultra-cold outflow." Such close companions may be responsible for the early and violent demise of most stars in the universe, Sahai noted.

"The extreme properties of the Boomerang challenge the conventional ideas about such interactions and provide us with one of the best opportunities to test the physics of binary systems that contain a giant star," adds Wouter Vlemmings, an astronomer at Chalmers University of Technology in Sweden and co-author on the study.

The Boomerang Nebula, a pre-planetary nebula produced by a dying star. ALMA observations show 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. Credit: ALMA (ESO/NAOJ/NRAO), R. Sahai

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.

When the Boomerang Nebula was first observed in 1995, astronomers noted that it was absorbing the light of the Cosmic Microwave Background, which is the leftover radiation from the Big Bang. This radiation provides the natural background temperature of space—only 2.725 degrees above absolute zero. For the Boomerang Nebula to absorb that radiation, it had to be even colder than this lingering, dim energy that has been continually cooling for more than 13 billion years.

The new ALMA observations also produced an evocative image of this pre-planetary , showing an hourglass-shaped outflow 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 snowplow.

The ultra-cold outflow is more than 10 times bigger. Traveling more than 150 kilometers per second, it took material at its outer edges approximately 3,500 years to reach these extreme distances after it was first ejected from the dying star.

These conditions, however, will not last long. Even now, the Boomerang Nebula is slowly warming.

"We see this remarkable object at a very special, very short-lived period of its life," noted Lars-Åke Nyman, an astronomer at the Joint ALMA Observatory in Santiago, Chile, and co-author on the paper. "It's possible these super cosmic freezers are quite common in the universe, but they can only maintain such extreme temperatures for a relatively short time."

Explore further: ALMA reveals ghostly shape of 'coldest place in the universe'

More information: R. Sahai et al. The Coldest Place in the Universe: Probing the Ultra-cold Outflow and Dusty Disk in the Boomerang Nebula, The Astrophysical Journal (2017). DOI: 10.3847/1538-4357/aa6d86

Related Stories

Hubble captures brilliant star death in 'rotten egg' nebula

February 3, 2017

The Calabash Nebula, pictured here—which has the technical name OH 231.8+04.2—is a spectacular example of the death of a low-mass star like the sun. This image taken by the NASA/ESA Hubble Space Telescope shows the star ...

Hubble Catches Scattered Light From The Boomerang Nebula

September 15, 2005

The Hubble Space Telescope has "caught" the Boomerang Nebula in these new images taken with the Advanced Camera for Surveys. This reflecting cloud of dust and gas has two nearly symmetric lobes (or cones) of matter that ...

New Hubble mosaic of the Orion Nebula

March 17, 2017

In the search for rogue planets and failed stars astronomers using the NASA/ESA Hubble Space Telescope have created a new mosaic image of the Orion Nebula. During their survey of the famous star formation region, they found ...

Hubble watches the icy blue wings of Hen 2-437

February 15, 2016

In this cosmic snapshot, the spectacularly symmetrical wings of Hen 2-437 show up in a magnificent icy blue hue. Hen 2-437 is a planetary nebula, one of around 3,000 such objects known to reside within the Milky Way.

Recommended for you

NASA telescope studies quirky comet 45P

November 22, 2017

When comet 45P zipped past Earth early in 2017, researchers observing from NASA's Infrared Telescope Facility, or IRTF, in Hawai'i gave the long-time trekker a thorough astronomical checkup. The results help fill in crucial ...

Cassini image mosaic: A farewell to Saturn

November 21, 2017

In a fitting farewell to the planet that had been its home for over 13 years, the Cassini spacecraft took one last, lingering look at Saturn and its splendid rings during the final leg of its journey and snapped a series ...

Uncovering the origins of galaxies' halos

November 21, 2017

Using the Subaru Telescope atop Maunakea, researchers have identified 11 dwarf galaxies and two star-containing halos in the outer region of a large spiral galaxy 25 million light-years away from Earth. The findings, published ...

4 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

cantdrive85
2.1 / 5 (7) Jun 05, 2017
"We have to learn again that science without contact with experiments is an enterprise which is likely to go completely astray into imaginary conjecture." Hannes Alfvén

There certainly is no shortage of imaginary conjecture produced by the plasma ignoramuses in the above.
krzychu01230
1 / 5 (2) Jun 08, 2017
Hourglass-shape is clear evidence of Peratt instability and driver of such phenomenon is electric/electromagnetic force within plasma; this is why bipolar configuration is so common in cosmos in various distance scales. Gravity and fluvial mechanics is unable to obtain such geometry, matter expulsion and structure coherence; gravi/fluvial hypothesis is untestable by lab experiments which should be main indicators of hypothesis correctness.
idjyit
5 / 5 (1) Jun 08, 2017
Awesome image
Da Schneib
not rated yet Jun 08, 2017
And a nice demonstration of some pretty interesting thermodynamics, too.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.