Omega Centauri unlikely to harbor life

August 9, 2018 by Sarah Nightingale, University of California, Riverside
There are colorful stars galore, but likely no habitable planets, inside the globular star cluster Omega Centauri. Credit: NASA, ESA, and the Hubble SM4 ERO Team

Searching for life in the vast universe is an overwhelming task, but scientists can cross one place off their list.

Omega Centauri—a densely packed cluster of stars in our galactic backyard—is unlikely to be home to , according to a study by scientists at the University of California, Riverside, and San Francisco State University.

Forthcoming in The Astrophysical Journal, the study was led by Stephen Kane, an associate professor of planetary astrophysics in UCR's Department of Earth Sciences and a pioneer in the search for habitable planets outside our solar system, known as exoplanets. Sarah Deveny, a graduate student at San Francisco State who is working with Kane, co-authored the paper.

In the hunt for habitable exoplanets, Omega Centauri, the largest globular cluster in the Milky Way, seemed like a good place to look. Comprising an estimated 10 million stars, the cluster is nearly 16,000 light years from Earth, making it visible to the naked eye and a relatively close target for observations by the Hubble Space Telescope.

"Despite the large number of stars concentrated in Omega Centauri's core, the prevalence of exoplanets remains somewhat unknown," Kane said. "However, since this type of compact star cluster exists across the universe, it is an intriguing place to look for habitability."

Starting with a rainbow-colored assortment of 470,000 stars in Omega Centauri's core, the researchers homed in on 350,000 stars whose color—a gauge of their temperature and age—means they could potentially harbor life-bearing planets.

For each star, they then calculated the habitable zone—the orbital region around each star in which a rocky planet could have liquid water, which is a key ingredient for life as we know it. Since most of the stars in Omega Centauri's core are red dwarfs, their are much closer than the one surrounding our own larger sun.

"The core of Omega Centauri could potentially be populated with a plethora of compact planetary systems that harbor habitable-zone planets close to a host star," Kane said. "An example of such a system is TRAPPIST-1, a miniature version of our own solar system that is 40 light years away and is currently viewed as one of the most promising places to look for alien life."

Ultimately, though, the cozy nature of stars in Omega Centauri forced the researchers to conclude that such planetary systems, however compact, cannot exist in the 's core. While our own sun is a comfortable 4.22 light years from its nearest neighbor, the average distance between stars in Omega Centauri's core is 0.16 light years, meaning they would encounter neighboring stars about once every 1 million years.

"The rate at which gravitationally interact with each other would be too high to harbor stable habitable planets," Deveny said. "Looking at clusters with similar or higher encounter rates to Omega Centauri's could lead to the same conclusion. So, studying globular clusters with lower encounter rates might lead to a higher probability of finding stable habitable ."

The title of the paper is "Habitability in the Omega Centauri Cluster."

Explore further: Chandra scouts nearest star system for possible hazards

More information: Habitability in the Omega Centauri Cluster, arXiv:1808.00053 [astro-ph.EP] arxiv.org/abs/1808.00053

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granville583762
3.9 / 5 (7) Aug 09, 2018
Want to be made to look foolish in the future - Rule out life in the Omega Centaury cluster

At 16,000Lys the Omega Centaury cluster where its stars are 0.16Lys equidistant rules out some animal life forms
Where oceans exist in on planets due to their proximity to the warmth of the variety of stars in the Omega Centaury cluster certainly does not rule out sea life
Whereas on land and sea cellular life exist even to the extent of minute insect and crustacean live with a wide variety lichens and variety of microbial and plant life
We're not talking tyrannosaurus life forms but practically invisible life forms!
Parsec
3.4 / 5 (5) Aug 09, 2018
@granville - I do not believe that you understand the core of the argument. The point is that gravitational disruption will ensure that all of the stars in the core will have their planets stripped and cast into interstellar space very quickly after formation because of close gravitational interactions with their neighbors.

One may postulate all kinds of places fro life. I suspect however planets without accompanying stars would very quickly become so frigid that life would be impossible. Energy is required to overcome the entropy barriers to life. That is an absolute thermodynamic and physical obstacle, irrelevant to any supposed biology, no matter how exotic.
granville583762
5 / 5 (4) Aug 09, 2018
Two Stars in Orbit a Trillion miles apart have their Planets in Orbit around them
Parsec> @granville I do not believe that you understand the core of the argument The point is that gravitational disruption will ensure that all of the stars in the core will have their planets stripped and cast into interstellar space very quickly after formation because of close gravitational interactions with their neighbor

I'm taking into account with my second sentence - at 16,000Lys the Omega Centaury cluster where its stars are 0.16Lys equidistant the first life on earth stated at 4.5billion years ago which for cellular and microscope microbial life needs to form
At 0.16Lys equidistant the stars are in orbital motion ejecting their outer shells at each other so they still form orbital disks as they are in orbit about their stars, planets still form as they orbit their stars just as earth is in solar orbit as the moon is in earth orbit
Parsec
3 / 5 (4) Aug 09, 2018
@granville - The odds that any planets remain attached to their birth stars is infinitesimal over a billion year time fram when swtripping events happen on the average every 1 million years. That means that on average neighboring stars will penetrate and strip planets about 4500 times every 4.5 billion years. I suspect that it really doesn't matter how many times new systems form.

For the smallest red dwarfs, their lifetimes on the main sequence is estimated on the order of 100's of billions of years. And these are the main types of stars found in the inner regions of cluster cores. The few large stars are often the consequence of actual star mergers, fantastically rare except where stars cluster so thick.
granville583762
5 / 5 (3) Aug 10, 2018
0.16Lys equates to 1.5136x10+12km where as Saturn is 778.5x10+6km and little old Earth is 149.5x10+6km
Taking the furthest planet Neptune at 4.495x10+9km is only 1/336 to the nearest star, as the stars are orbiting each other the Omega Centaury cluster has been forming these stars for 15billion years is proof they are in orbit and not bumping into each other in the night
Parsec> For the smallest red dwarfs, their lifetimes on the main sequence is estimated on the order of 100's of billions of years. And these are the main types of stars found in the inner regions of cluster cores. The few large stars are often the consequence of actual star mergers, fantastically rare except where stars cluster so thick

these stars are not in contact with each, as firstly they would not have formed in the numbers they have in the first place and secondly the collisions if they were colliding which contradicts their formation would give us a daily spectacular ring side view
granville583762
5 / 5 (3) Aug 10, 2018
Interestingly the Omega Centaury Cluster stars live 100's of billions of years in a Universe that is 13.8billion years

A point concerning the life time of the omega centaury cluster stars "For the smallest red dwarfs, their lifetimes on the main sequence is the order of 100's of billions of years"

Taking the extremely rare stellar interaction, I'm intrigued that these stars were in and forming in the Omega Centaury cluster long before the universe was even thought of never mind conceived, as nature in its wisdom has no evolutionary purpose for stars to live 100s of billions of years if it has not a universe already conceived ready and waiting for its stellar occupants
granville583762
5 / 5 (3) Aug 10, 2018
OUR SUN HAS A GREATER STRIPPING FORCE ON EARTH than stars in the Omega Centaury Cluster!

What is the gravitational force of one star on the surface by another at 1.5136x10+12km as you mention their masses, as being some are red dwarfs?

In comparison to the Suns gravitational force on the earth's surface at 149.5x10+6km
My intuition Parsec, tells me that taking two equal mass stars to our Sun has a (1.5trillion)*/(150million)* greater stripping force in our Solar Sytem on planet EARTH than the Omega Centaury Cluster stars have on their planets

In Fact Our Sun Has 10,000 Times Greater Stripping Power than stars in the Omega Centaury Cluster!
granville583762
5 / 5 (3) Aug 10, 2018
Our Suns greater gravitational stripping power
It appears Parsec, my original statement "Want to be made to look foolish in the future - Rule out life in the Omega Centaury cluster" still holds water and some microbial life!
Anonym438132
not rated yet Aug 11, 2018
0.16 anos luz a cada 1 milhão de anos é = 1.51 trilhões de KM de distancia até a outra estrela isso é = 336,3 vezes a distancia de Netuno ao sol, sendo a maior parte dessas estrelas anãs vermelhas com massas geralmente em maioria abaixo de 0,25 massas solares / TRAPPIST-1= 0,089 massas solares vida estimada em 12,7 trilhões de anos, seu planeta mais distante conhecido está em TRAPPIST-1h há 9,3 milhões de KM de distancia da estrela mãe, levando essa escala para Omega Centauri e mesmo com uma distancia média de cruzamento a cada 1 milhão de anos de uma estrela para outra anãs vermelhas de 0,16 de 1 ano luz, logo Omega Centauri pode sim ser lotado de planetas habitáveis e com inteligencia, a distancia está ainda muito grande para abalar a habilitabilidade entre um sistema e outro, se tivessemos ao menos uma estrela a outra há uma distancia entre Saturno de 1,5 bilhões de KM dai sim essa pesquisa seria aceitável.
Anonym438132
not rated yet Aug 11, 2018
Essa distancia para esse tipo de estrela não tem força o suficiente para ejetar planetas de um sistema para o outro, mesmo porque a maioria desses sistemas com massas abaixo de 0,25 massas solares orbitando um ao outro tem planetas provavelmente até uma distancia máxima de 5 bilhões de KM da estrela mãe, e claro a força gravitacional de uma estrela desse porte é centenas de vezes mais baixo do que a de uma estrela igual a nossa com muitas delas milhares de vezes mais fracas que o sol. Omega Centauri é inabitável? É melhor rever os seus conceitos. Eu apostaria milhões de planetas rochosos nesse aglomerado de estrelas, e muitos deles habitáveis. Estrelas de 0,5 vezes a massa do sol são cotadas para passarem raspando no nosso sistema solar pelo menos algumas vezes a uma distancia semelhante e o maximo que fazem é bagunçar a orbita de alguns cometas, asteroides e planetoides na Nuveem Oort acima de 10 mil UA, isso não é capaz de nem de fazer cocegas em Netuno.

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