The View from an Intergalactic Straggler

by Paul Gilster on September 21, 2007

Speaking of absorbing views from a planetary surface, as we’ve been doing recently when discussing the Magellanic Clouds and what an observer there might see of the Milky Way, consider a much darker scenario. A galaxy called ESO 137-001 is in headlong flight toward the center of the galactic cluster Abell 3627. It is leaving in its wake a trail of gas that extends for more than 200,000 light years and is forming stars.

Bear in mind that the Milky Way itself is 100,000 light years across and you’ll get an idea of the magnitude of this tail, which Michigan State’s Ming Sun calls one of the longest of its kind his team has ever seen. Millions of stars have now come to life in the tail, apparently forming within the last ten million years. Adding to optical studies are Chandra X-ray data that show additional regions thought to be star-bearing.

Give these stars a few billion years to produce planets bearing intelligent life and you have a civilization coming into its own with skies that would be, by our standards, remarkably dark. The day will come when the gas that has produced the orphan stars is completely stripped from its parent galaxy, stopping further star formation, and the stragglers will be left out on a very long limb indeed.

A long galactic tail forming stars

Image: The comet-like tail behind the galaxy ESO 137-001 is clearly shown in this Chandra X-ray Observatory image. The 70,000 light year long tail was created as gas was stripped from ESO 137-001 while it plunges toward the center of Abell 3627, a giant cluster of galaxies. Cool gas from the galaxy – only seen in optical images – is mixed in with hot gas from the cluster as seen in X-rays. Credit: X-ray: NASA/CXC/MSU/M. Sun et al.; Optical: SOAR (MSU/NOAO/UNC/CNPq-Brazil)/M.Sun et al.

Thus we look at the inverse of the famous Isaac Asimov story ‘Nightfall.’ The good doctor postulated a planet in a system with six suns, keeping the surface always illuminated save for one day every 2049 years. Astounding‘s John Campbell proposed the story to Asimov by citing a Ralph Waldo Emerson quote: “If the stars should appear one night in a thousand years, how would men believe and adore and preserve for many generations the remembrance of the city of God!” Asimov took the idea and ran, producing one of science fiction’s classic works.

I’m not aware of a fictional equivalent to the situation postulated by the straggler stars of ESO 137-001, but there may be more orphans than we think. If, as some believe, galactic tails were not uncommon billions of years ago in an era of richer star-forming materials, then there may be hosts of planets experiencing the deep darkness of intergalactic space. We’ll know more about that idea when the paper on this work appears in The Astrophysical Journal, an event slated for December.

andy September 21, 2007 at 14:01

I guess an approximate fictional equivalent might be Against a Dark Background by Iain M Banks, set in a solar system in the middle of intergalacticc space.

Egghead September 21, 2007 at 14:20

The planet Kricket from the Hitchhiker’s Guide to the Galaxy trilogy had skies that were completely dark (albeit for different reasons – all other stars were hidden from view by a dust cloud). The inhabitants were psychologically incapable of even imagining an “out there.” So, when a spacecraft crashed on their planet, proving that they weren’t alone, they engaged on a genocidal crusade to destroy the rest of the universe. But other than that, they were quite lovely people.

Administrator September 21, 2007 at 15:17

I’m somewhat familiar with Iain Banks’ work though not with Against a Dark Background, nor did I know about Kricket. Thanks to you both! I loved the old BBC radio version of Hitchhiker’s Guide.

Ron S September 21, 2007 at 15:22

These intergalactic systems might even be suitable to advanced life since they may be less bothered by some extinction events, like nearby supernovae and GRBs. That is, once they escape the initial violence that caused the gas cloud to be ejected from a galaxy, and if the cloud is already metal rich.

Their poets however would have to find something to expound upon other than the sky and stars. Just like Adams describes for the Krikkit folks.

Adam September 21, 2007 at 19:41

Hi Ron

If the Cosmic Ray theory of mass extinction cycles is correct then intergalactic space is even nastier than intragalactic space.

devicerandom September 22, 2007 at 9:04

Also, World Without Stars of Poul Anderson described a world being in orbit to a star lonely placed almost outside of our own Galaxy. The description of a sky featuring only the few planets of the system and the immense spiral of the Milky Way rising and taking half the sky was awesome.

Christopher L. Bennett September 22, 2007 at 9:25

The night sky wouldn’t be completely dark for them, because they’d have the other planets, moons, and comets of their own system to look at, as well as a sky full of galaxies. We can see at least some nearby galaxies with the naked eye, so they could too — and they’d have less dust and interstellar medium in the way to block their view. So rather than a totally empty night sky, they’d just have a simpler night sky, one where it was easier to keep track of everything the naked eye could register.

Administrator September 22, 2007 at 9:38

That’s it — I knew I was missing an Anderson story. Thanks for jogging my memory re World Without Stars!

andy September 22, 2007 at 10:42

Of course, our solar system may enjoy such views as a result of the merger of our galaxy and M31, so the red giant Sun may shine in an empty sky.

No romantic starlit nights on the beaches of thawed Europa then.

ljk November 12, 2007 at 0:58

Searching for the Precursors of Life in External Galaxies

Authors: B. Lawton (1), C. W. Churchill (1), B. A. York (2), S. L. Ellison (2), T. P. Snow (3), R. A. Johnson (4), S. G. Ryan (5), C. R. Benn (6) ((1) New Mexico State University, Las Cruces, USA, (2) University of Victoria, Victoria, Canada, (3) University of Colorado, Boulder, USA, (4) Oxford Astrophysics, Oxford, UK, (5) University of Hertfordshire, Hatfield, UK, (6) Isaac Newton Group, Santa Cruz de La Palma, Spain)

(Submitted on 8 Nov 2007)

Abstract: Are the organic molecules crucial for life on Earth abundant in early-epoch galaxies? To address this, we searched for organic molecules in extragalactic sources via their absorption features, known as diffuse interstellar bands (DIBs). There is strong evidence that DIBs are associated with polycyclic aromatic hydrocarbons (PAHs) and carbon chains. Galaxies with a preponderance of DIBs may be the most likely places in which to expect life.

We use the method of quasar absorption lines to probe intervening early-epoch galaxies for the DIBs. We present the equivalent width measurements of DIBs in one neutral hydrogen (HI) abundant galaxy and limits for five DIB bands in six other HI-rich galaxies (damped Lyman-alpha systems–DLAs). Our results reveal that HI-rich galaxies are dust poor and have significantly lower reddening than known DIB-rich Milky Way environments. We find that DIBs in HI-rich galaxies do not show the same correlation with hydrogen abundance as observed in the Milky Way; the extragalactic DIBs are underabundant by as much as 10 times. The lower limit gas-to-dust ratios of four of the HI-rich early epoch galaxies are much higher than the gas-to-dust ratios found in the Milky Way. Our results suggest that the organic molecules responsible for the DIBs are underabundant in HI-rich early epoch galaxies relative to the Milky Way.

Comments: 6 pages, 2 figures

Subjects: Astrophysics (astro-ph)

Cite as: arXiv:0711.1372v1 [astro-ph]

Submission history

From: Brandon Lawton [view email]

[v1] Thu, 8 Nov 2007 22:46:26 GMT (115kb)

http://arxiv.org/abs/0711.1372

ljk November 13, 2007 at 12:34

New evidence for extragalactic life-forming matter

NewScientist.com news service Nov. 13, 2007

*************************

A team led by Sara Ellison of the
University of Victoria, Canada, has
found another galaxy about 2 billion
light years away with telltale
diffuse interstellar bands, possibly
indicative of polycyclic aromatic
hydrocarbons–organic compounds….

http://www.kurzweilai.net/email/newsRedirect.html?newsID=7476&m=25748

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