The Milky Way as a Garden

by Paul Gilster on November 14, 2007

By Larry Klaes

Tau Zero journalist Larry Klaes looks at Jon Lomberg’s stunning Galaxy Garden in Hawaii. Lomberg told Larry that working on the garden had made him appreciate on a primal level just how many objects there are in even a ‘small’ section of the Milky Way. So there’s one answer to the Fermi Paradox: If extraterrestrial civilizations are out there, maybe they’re simply too busy exploring to have gotten around to us!

There is a galaxy on Hawaii. Not an actual galaxy, of course, as a typical island of stars contains many billions of suns and spans hundreds of thousands of light years. The galaxy residing on the largest of that particular chain of Pacific islands is a 100-foot wide living representation of the vast stellar realm our planet and humanity dwells in, the Milky Way.

Called the Galaxy Garden, the idea for this unique project began about eight years ago in the mind of artist Jon Lomberg, who worked with Cornell University astronomer Carl Sagan on his Cosmos PBS television series and created the artwork placed on the golden Voyager Interstellar Record.

“The galaxy has always fascinated me,” says Lomberg. “One of the biggest misconceptions the public has is what a galaxy is. People can’t grasp the scale. They often confuse galaxy with solar system. I wanted to have a way to help people see and understand the Milky Way on a scale they can relate to.”

Lomberg cites two reasons for his using a garden to showcase our galaxy. One involves having a structure that people can actually walk through to be physically present in it. The other comes from seeing parallels between plant life and celestial objects, going back to his earlier artwork which combined biological and astronomical motifs, including the dandelion seed shape of the Spaceship of the Imagination that Sagan used to travel about the Universe in the Cosmos series.

Galaxy Garden in perspective

Image: The centerpiece of the Paleaku Astronomy Center is the 100 ft. diameter model of the Milky Way. The scale is 1000 light years per foot, which is about 83 light years per inch. The Galaxy Garden is set on 1/4 acre of lawn, whose gentle swell suggests the observed warp of the actual galactic disk. Credit: Jon Lomberg.

“Star forming regions like the Orion Nebula always looked like flowers to me,” explains Lomberg “This is the basis for the idea of using plants to make a large model of the Milky Way galaxy.”

After searching for a place to literally and figuratively plant his idea, Lomberg was offered a plot by Barbara DeFranco, Director of the Paleaku Peace Garden Sanctuary. Paleaku Gardens is a nine acre botanical garden in Kona, Hawaii, on the western side of the island that facilitates educational, spiritual, and cultural programs. The garden declares its mission “is to offer a sanctuary for the advancement of individuals toward peace and harmony.”

“Without [DeFranco] there wouldn’t have been a Galaxy Garden,” said Lomberg. “She offered the land for free because she thought it would enhance her gardens. Barbara is a partner in this endeavor; she knows as much about gardening as I do about astronomy.”

Major funding for the heavy equipment to build the garden, the accompanying visitor’s center, and the one thousand plants required to represent the Milky Way came from the Change Happens Foundation. The man who endows that organization is a big fan of Carl Sagan and his Cosmos series. Seed money came from the New Moon Foundation.
Making and keeping the Galaxy Garden accurate fell to UC Berkeley astronomer Leo Blitz, who co-discovered the large “bar” of stars stretching across the galactic center. Blitz spent over two years mapping out the true structure of the galaxy for the garden.

“[Blitz] is the guy who kept me honest,” declares Lomberg. “He gave me a basis to start from. Even professional astronomers who think they understand the Milky Way will find their conceptions of it deepened by the Galaxy Garden.”

To give a sense of scale to this special project, each foot of the garden equals one thousand lights years, the distance light travels in one year moving at 186,000 miles each second – about six trillion miles. Each inch equals 83 light years.

Lomberg originally thought he could represent some of the 400 billion stars of the Milky Way with some kind of small flower, but he soon realized that even they would be too large at the garden’s scale, nor could he have enough.

In their place, Lomberg turned to using the gold dust croton plant, whose yellow speckled green leaves stand in for various fields of stars. One leaf holds our Solar System and most of our neighboring suns. The croton plant was also chosen for its longevity, slow growth, lack of thorns, and high tolerance to sunlight.

Nearby stars depicted

Image: A small yellow crystal earring shows the position of our Earth and Sun, though our solar system is actually 1,000 times smaller than the jewel. Nearby bright stars are also shown with different colored jewels. Credit: Jon Lomberg.

The nebulae, clouds of dust and gas from which stars are born, are depicted by the colorful flowers of the hibiscus plant. Smaller planetary nebulae, the signs of a sun on its way out of existence, are shown with smaller red and white flowers such as periwinkles and vincas.

Globular clusters, spherical collections of hundreds of thousands of stars, are represented by dracaena trees. These plants were chosen to show some of the clusters which dwell “above” the plane of the Milky Way’s spiral disk, though Lomberg notes it will take several years for the thin-trunked trees to attain the proper height.

Traveling in towards the center of our galaxy, visitors will find the aforementioned galactic bar represented by an oval of small gray boulders. Inside that formation, at the very core our stellar island, is a water fountain representing the supermassive black hole residing there. Four million times more massive than our yellow dwarf sun, the galaxy’s black hole sits at the center of the Milky Way, constantly ingesting interstellar dust and gas and the occasional star.

“I was very mindful of how important it was for Carl Sagan to have people understand our place in the Cosmos,” said Lomberg. “The Galaxy Garden is an artist’s culmination of my whole career of doing galaxies. One of the first paintings Carl ever bought from me was one depicting where we were in the galaxy. We never talked about the Galaxy Garden concept, but Carl; always liked the metaphorical approach to explaining the Universe. In my heart, this garden is dedicated to Carl Sagan. It carries on the tradition of public elevation that he cared about so much.”

The Galaxy Garden, which opened to the public on October 21, can also be viewed online.

Edg Duveyoung November 14, 2007 at 10:13

This article inspires one with the vastness of creation. In your mind, gentle reader, when you “mentally entertain” the concepts of this article, surely a sense of awe must arise. This is the awe that drives science — awe that every concept can inspire — every — the least aspect of reality can be found enthralling at least a geek or two who then make it their careers to flesh out the bones of dry formulas, nuances, and core dynamics.

This is awe inspired by hard cold data.

I now present you with a dataset that might be a bit “soft” comparatively, but it is a far more vital and immediate in that in your “lab,” your own mind, you can conduct a conceptual experiment with a psychological dynamic — “sense of self” — that every human being has. In short, “identification” is this sense of self, and the below takes this “knowledge” you have and “runs with it.” Try the below and see if your sense of awe is not stirred as this article has done.

Edg

You will be experiencing a series of “jumps.” Do not rush this
experiment. Take one jump at a time. The more you take your time,
the more powerful will your results be. If possible, get someone to
read this experiment’s instructions to you as you sit with eyes closed
and follow them. Have them read in a quiet voice, and have the reader
pause after every step, and have a hand signal that you must give for
the reader to start the next step. If you have no one to help like
this, then read the step, and then close your eyes and follow that
step’s instructions until you feel you’re ready to try the next step.

Close your eyes and feel the various parts of your body. Try to
distinguish the sensations of the more inner parts from the sensations
coming from the parts of your body that are reporting contact with
your clothing, the chair you are sitting on, the floor being sensed
beneath your feet, etc. Try to feel the inside of your head, between
your eyes, inside the nasal passages, the deeper parts of your mouth
cavity. Try to feel your eardrums actually capturing sounds. Feel —
don’t listen — feel your eardrums being moved by the sound waves
crashing into them. Feel the inside of your throat and neck.
Practice “scooting around the body” to “visit” these various sensations.

Jump One. After a few minutes of this practice, now, in your mind’s
eye, with eyes still closed, imagine that you can sense yourself
ranging throughout your immediate environment as if it were also your
body. Pretend you are getting “reports” or “sensations” or “some sort
of information” from the nearby objects in the room. To whatever
extent you can, sense the presence of the objects of the room — even
though your eyes are closed. This sense may simply be a conviction on
your part that you “know” that the desk is “there.” Pretend you can
“somehow” feel the desk, the chair, the floor, the other furniture in
the room, and finally feel the presence of the walls of the room like
“another skin” around you. Scoot around the room like this for a few
minutes with your imagination. Feel that the room is completely
filled with your aliveness, your consciousness. Sense that every
speck of space in the room has you within it.

Jump Two. After a few minutes, “break out” of the room. Pretend that
you now can range freely around the entire structure of the building
you are in. Do NOT imagine yourself traveling around the building
like a ghost; instead, actually feel that you are being in every part
of the building simultaneously — JUST LIKE YOU NOW FEEL YOU ARE IN
EVERY PART OF YOUR BODY. Fill the building with “you,” with your
living presence. Take a minute or two to gain a bit of comfort doing
this, or rather, BEING this.

Jump Three. Now take a breath, let it out, and as you breathe out,
fill up your neighborhood with consciousness. Pretend you are the
life breath, the soul, of the entire area in which you live. All the
buildings, all the people, all the animals, the wind, EVERYTHING is
filled with your spirit. Scoot around in your imagination for a few
minutes. Everywhere you go, there you are already. Like your hands
or feet have always been filled with you, feel the various “parts of
you” in the neighborhood being similarly filled. But, understand that
everything is instantly available to you by merely putting your
attention on it. There’s no “waiting” for more distant “parts of you”
to “report in.” No part of you is farther from you in terms of time.

Jump Four. After a little comfort is gained, take another deep breath
and fill up all the land around you with awareness as you exhale.
Blossom yourself to huge proportion. Pretend that the seacoasts are
like your toe and finger tips. Feel the immense dynamism of the
detailed world that is full with your loving grace and support. Feel
like the one soul that pervades everything. See that everything is
IMMEDIATELY available to you — just a glancing or listening and
instantly that part of you reports in with some data. Imagine
smelling the sea air on one coast, instantly seeing a silent bird
gliding up a mountain slope and then immediately hearing the waves of
the other coast.

Jump Five. Now, take another deep breath, and fill the Earth with
your spirit. Say “hello” to the universe as you “try on” your
Earth-body. Open your spiritual eyes to scan the vast reaches around
you. Feel the majesty of your new self, a magnificent planet with
billions upon billions of lives complexly intertwined. Feel the
serenity of space as you bask in the pleasure of being so vibrantly
alive with awareness.

Jump Six. Fill up the universe. Do not waste time with filling only
our galaxy, fill the whole of space and time. Fill it all. Pretend
that the billions of galaxies are like cells of your body. Delight in
the fullness of your almost infinite resources. Countless lives
experiencing an endless parade of feelings, emotions, thoughts, birth
and death. Feel the intimate ownership of everything. Instantly
across billions of light years of distance you find yourself “already
there” wherever you gaze. Feel how far beyond ordinary concerns you
are. Millions of your units are dying and millions are being born.
Incredible changes are happening by the instant, but you are unchanged
by any of it. You are filling up everything. You support all. Glory
surrounds you like a cloud of light.

Jump Seven. See that the magnificence of all this is merely an object
that is within your attention. The immensity that you are, with your
myriad bodies and the wisdom of millions of cultures, is but a small
blip, just something to perceive, a THING, a very tiny precious jewel
in a vast infinite consciousness that is completely unbounded by any
limitations. Feel yourself to be, as you have always been, an all
pervading awareness that is everywhere, every time simultaneously.
You contain all of it, and it is exceedingly small compared to the
vastness of your presence. Know yourself to be pure, absolute and
beyond everything.

Jump Eight. Give up all conceptualizations, feelings, sensations,
memories, values, qualities, and physicality. You are that that is
beyond all these things including the consciousness that is aware of
them for you. Understand that consciousness loves the universe and
loves creating thoughts about it and presenting them to YOU. See that
the infinite resourcefulness of consciousness is there for you to
witness as it conveys the universe to you. See that these thoughts
about consciousness and its infinity are being created by
consciousness, not you. You are the witness of it all, the soul of
consciousness, the source of consciousness itself. You cannot be
described, but yet you are. Beyond all concept, you are. Completely
beyond.

Jump Nine. From out of this infinity, watch as consciousness seeks to
please you — even though you do not need any THING. Watch as
consciousness brings to you the vision of one of your bodies sitting
in a room with eyes closed with its small individual spark of
consciousness. Watch as consciousness introduces this individual to
the unlimited potentiality of itself. Feel the surge of pure love
that consciousness has for this small spark. Watch the blessing of
pure compassion flood this individual as the entirety of creation is
found securely and comfortably residing within. Feel the circle being
completed.

dad2059 November 14, 2007 at 10:57

Beautiful Larry. Nature is an artist on Gaia as well as Galactica.

Cindy M November 14, 2007 at 15:59

I think you guys need to quit smoking weed! Lol. Seriously, though…very cool.

george scaglione November 15, 2007 at 10:19

cindy i was not a part of this discussion but i did notice how funny and cool your above answer was.just had to tell you so! lol,great! your friend george scaglione ps if you wanted to it would’nt be hard to notice the on going conversation between myself and my buddies forrest and jim…if you like feel free to say something! all the best g

philw1776 November 15, 2007 at 20:23

Too busy?
Seems like folks have forgotten timescales. No matter how busy a civ is given billions of years total saturation is viable. A civilization could explore the entire galaxy in less than 100 M Yr.

ljk November 16, 2007 at 14:56

You assume that all species want to colonize like humans do,
or that their descendants will all have the same goals over
a 100 million year period.

We can barely keep civilizations intact over a few centuries.

philw1776 November 16, 2007 at 19:07

No, I assume that only one species needs to be expansionist. It only takes one over the multi-billion year history of the galaxy. One species that isn’t ‘busy’.

ljk November 16, 2007 at 19:26

But if such a species did this one billion years ago,
would anything remain of them to be recognizable
as artificial? Plus you assume they visited all 400
billion star systems and left visible marks.

ljk November 20, 2007 at 12:35

The MW is an exceptionnally quiet galaxy: implications for spiral formation

Authors: M. Puech, F. Hammer, L. Chemin, H. Flores, M. Lehnert

(Submitted on 19 Nov 2007)

Abstract: We compare both the Milky Way and M31 to local external disk galaxies within the same mass range, using their relative locations in the planes formed by Vflat vs. MK (the Tully-Fisher relation), j_disk (specific angular momentum) and the average Fe abundance of stars in the galaxy outskirts. We find, for all relationships, that the MW is systematically offset by 1 sigma or more, showing a significant deficiency in stellar mass, angular momentum, disk radius and [Fe/H] in the stars in its outskirts at a given Vflat.

Our Galaxy appears to have escaped any significant merger over the last 10-11 Gyr which may explain its peculiar properties. As with M31, most local spirals show evidence for a history shaped mainly by relatively recent merging.

Comments: 2, pages, 1 figure, proceeding of the poster presented at the Vatican Conf. “Formation and evolution of galaxy disks” held in Rome, 1-5 Oct. 2007

Subjects: Astrophysics (astro-ph)

Cite as: arXiv:0711.2881v1 [astro-ph]

Submission history

From: Mathieu Puech [view email]

[v1] Mon, 19 Nov 2007 09:57:15 GMT (157kb)

http://arxiv.org/abs/0711.2881

David Langlois November 21, 2007 at 13:21

I think a song lyric might be relevant here:
“Starlight – flowering – endlessly through the Universal Garden, Garden above.” – Yes, “Universal Garden” _Open Your Eyes_

What musicians can so eloquently say & I can barely get out edgewise is this concept of the Milky Way (& indeed the known universe) as a fertile garden of life – as opposed to the current barren wilderness it presents itself as to our telescopes. While the majority of it may not be life as we know it there will nevertheless be numerous gardens above – enough to fill the entire sky. Or so goes the idea, which I’m coming around to, that between the number of red dwarfs & brown dwarfs & gas giant moons there must be an infinity of unseen ecosystems.

ljk November 24, 2007 at 0:39

Influence of AGN Outbursts on the Surrounding Galaxies

Authors: Yutaka Fujita (Osaka U.)

(Submitted on 21 Nov 2007)

Abstract: We study the influence of a strong AGN outburst on the surrounding galaxies. The AGN is assumed to reside in a group of galaxies, and an outburst excites a shock wave in the hot gas in the group. We calculate the impact of the shock wave on the galaxies.

We find that if the energy of the outburst is extremely large (E_AGN ~6×10^61 erg) as the one recently observed in clusters, the impact is strong enough to strip the cold interstellar medium in the disc of the galaxies in the inner region of the group. Moreover, even in the outer region of the group, the warm gas in the halo of the galaxies would be stripped, even if the energy of the outburst is ~6×10^60 erg. These would decrease star formation activity of the galaxies. If these galaxies fall into the group centre through dynamical friction and their interstellar medium is the fuel of the supermassive black hole in the AGN, the outburst would serve as feedback. While this mechanism works only when E_AGN is extremely large, such outbursts have not been observed in groups at low redshift; it would work at high redshift rather than at low redshift.

Comments: Accepted for publication in MNRAS Letters

Subjects: Astrophysics (astro-ph)

Report number: OU-TAP 285

Cite as: arXiv:0711.3209v1 [astro-ph]

Submission history

From: Yutaka Fujita [view email]

[v1] Wed, 21 Nov 2007 00:00:06 GMT (61kb)

http://arxiv.org/abs/0711.3209

ljk January 24, 2008 at 10:13

A story on the Galaxy Garden can be seen on the Big Island
Television web site at this URL:

http://bigislandtv.com

Click on “Big Island Videos” then go to “Features” where the story is.

ljk February 6, 2008 at 22:44

Galactic Dynamics

Second Edition

James Binney & Scott Tremaine

To read the entire book description or a sample chapter, please visit:

http://press.princeton.edu/titles/8697.html

Since it was first published in 1987, Galactic Dynamics has become the most widely used advanced textbook on the structure and dynamics of galaxies and one of the most cited references in astrophysics. Now, in this extensively revised and updated edition, James Binney and Scott Tremaine describe the dramatic recent advances in this subject, making Galactic Dynamics the most authoritative introduction to galactic astrophysics available to advanced undergraduate students, graduate students, and researchers.

“All astronomers and dynamicists should acquire and read this impressive book. It is both readable and rigorous: destined to become a classic landmark in the subject. “–Times Higher Education Supplement

Paper | $60.00 / £35.00 | ISBN: 978-0-691-13027-9

Cloth | $110.00 / £65.00 | ISBN: 978-0-691-13026-2

ljk February 21, 2008 at 21:53

http://www.usyd.edu.au/news/84.html?newsstoryid=2163

The Milky Way is twice the size we thought it was

20 February 2008

We were tossing around ideas about the size of the Galaxy, and thought we had better check the standard numbers that everyone uses,” Professor Gaensler said. Image credit: NASA, ESA, and The Hubble Heritage Team (STScI/AURA)

It took just a couple of hours using data available on the internet for University of Sydney scientists to discover that the Milky Way is twice as wide as previously thought.

Astrophysicist Professor Bryan Gaensler led a team that has found that our galaxy – a flattened spiral about 100,000 light years across – is 12,000 light years thick, not the 6,000 light years that had been previously thought.

Proving not all science requires big, expensive apparatus, Professor Gaensler and colleagues, Dr Greg Madsen, Dr Shami Chatterjee and PhD student Ann Mao, downloaded data from the internet and analysed it in a spreadsheet.

“We were tossing around ideas about the size of the Galaxy, and thought we had better check the standard numbers that everyone uses. It took us just a few hours to calculate this for ourselves. We thought we had to be wrong, so we checked and rechecked and couldn’t find any mistakes.”

The University of Sydney team’s analysis differs from previous calculations because they were more discerning with their data selection. “We used data from pulsars: stars that flash with a regular pulse,” Professor Gaensler explains. “As light from these pulsars travels to us, it interacts with electrons scattered between the stars (the Warm Ionised Medium, or WIM), which slows the light down.

“In particular, the longer (redder) wavelengths of the pulse slow down more than the shorter (bluer) wavelengths, so by seeing how far the red lags behind the blue we can calculate how much WIM the pulse has travelled through.

“If you know the distance to the pulsar accurately, then you can work out how dense the WIM is and where it stops – in other words where the Galaxy’s edge is.

“Of the thousands of pulsars known in and around our Galaxy, only about 60 have really well known distances. But to measure the thickness of the Milky Way we need to focus only on those that are sitting above or below the main part of the Galaxy; it turns out that pulsars embedded in the main disk of the Milky Way don’t give us useful information.”

Choosing only the pulsars well above or below us cuts the number of measurements by a factor of three, but it is precisely this rejection of data points that makes The University of Sydney’s analysis different from previous work.

“Some colleagues have come up to me and have said ‘That wrecks everything!'” says Professor Gaensler. “And others have said ‘Ah! Now everything fits together!'”

The team’s results were presented in January this year at the 211th meeting of the American Astronomical Society in Austin, Texas.

About Professor Bryan Gaensler:

Professor Gaensler is a graduate of the University of Sydney and a former Young Australian of the Year. After working at the Department of Astronomy at Harvard University he was lured back to Australia on prestigious Federation Fellowship. One of the world’s leading astronomers, his research interests include studying the essential role that magnetic fields play in the generation of turbulence and large-scale structures, the production of high-energy cosmic ray particles, and the formation of the first stars and galaxies.

ljk March 26, 2008 at 16:19

The direction of various objects in the galaxy as seen from Earth:

http://planetary.org/image/MilkyWay_blog.gif

ljk June 3, 2008 at 14:32

Two of the Milky Way’s Spiral Arms Go Missing

http://www.jpl.nasa.gov/news/news.cfm?release=2008-094

ljk December 19, 2008 at 0:29

arXiv:0812.3491

Date: Thu, 18 Dec 2008 09:43:45 GMT (4206kb)

Title: The Milky Way Spiral Arm Pattern

Authors: Peter Englmaier, Martin Pohl, Nicolai Bissantz

Categories: astro-ph

Comments: 6 pages, 4 figures.

To appear in “Tumbling, Twisting, and Winding Galaxies: Pattern Speeds along the Hubble Sequence”, E. M. Corsini and V. P.Debattista (eds.), Memorie della Societa Astronomica Italiana

A complete map of the 3D distribution of molecular (CO) gas was constructed using a realistic dynamical model of the gas flow in the barred potential of the Milky Way.

The map shows two prominent spiral arms starting at the bar ends connecting smoothly to the 4-armed spiral pattern observed in the atomic hydrogen gas in the outer Galaxy.

Unlike previous attempts, our new map uncovers the gas distribution in the bar region of the Galaxy and the far side of the disk. For the first time, we can follow spiral arms in gas as they pass behind the galactic centre.

http://arxiv.org/abs/0812.3491 , 4206kb

ljk March 10, 2009 at 9:53

The Milky Way galaxy may have the mass of 3 TRILLION suns:

http://www.sciencenews.org/view/generic/id/39709/title/This_just_in_Milky_Way_as_massive_as_3_trillion_suns

If this is the case, in addition to upping the odds for there being
more worlds and therefore more chances of life in this galaxy,
it also means that our Milky Way and the Andromeda galaxy may
collide several billion years sooner than previously predicted.

ljk September 1, 2009 at 21:35

A Color All-Sky Panorama Image of the Milky Way

Authors: Axel Mellinger

(Submitted on 29 Aug 2009)

Abstract: This article describes the assembly of an optical (RGB) all-sky mosaic image with an image scale of 36 arcsec/pixel, a limiting magnitude of approx. 14 mag and an 18 bit dynamic range. Using a portable low-cost system, 70 fields (each covering 40 deg x 27 deg) were imaged over a time span of 21 months from dark-sky locations in South Africa, Texas and Michigan.

The fields were photometrically calibrated against standard catalog stars. Using sky background data from the Pioneer 10 and 11 space probes, gradients resulting from artificial light pollution, airglow and zodiacal light were eliminated, while the large-scale galactic and extragalactic background resulting from unresolved sources was preserved.

The 648 Megapixel image is a valuable educational tool, being able to fully utilize the resolution and dynamic range of modern full-dome planetarium projection systems.

Comments: 7 figures, submitted to PASP

Subjects: Galaxy Astrophysics (astro-ph.GA)

Cite as: arXiv:0908.4360v1 [astro-ph.GA]

Submission history

From: Axel Mellinger [view email]

[v1] Sat, 29 Aug 2009 20:53:58 GMT (971kb,D)

http://arxiv.org/abs/0908.4360

ljk December 1, 2009 at 22:10

http://www.technologyreview.com/blog/arxiv/24452/?a=f

Tuesday, November 24, 2009

New 3-D Map of the Galaxy Unveiled

A new three-dimensional map of the Milky Way should give astronomers a unique insight into the formation and evolution of our galaxy.

Mapping the galaxy is tricky business because of the inherent difficulties in measuring distances to stars. The problem boils down to determining the inherent brightness of a star, a property called its absolute magnitude. Then the difference between this and its observed magnitude on Earth gives you some idea of its distance.

But how to determine absolute magnitude? One way is to use the famous Hertzprung-Russel diagram (also known as the colour magnitude diagram), which plots the relationship between a star’s colour and its absolute magnitude. The process is relatively straightforward: measure a star’s colour and observed magnitude, then determine its absolute magnitude from the colour magnitude diagram. A straightforward calculation should give you its distance (provided there’s no dust obscuring your view).

The problem of course is that the colour magnitude diagram is complex and many-valued. So a star with a given colour could belong to one of several different stellar populations with different luminosities.

Until recently, all that had been more or less academic because nobody had measured the colours of most stars in the galaxy.

All that changed with the Sloan Digital Sky Survey, an effort now ten years old to scour the skies using a 2.5 metre telescope at Apache Point Observatory in New Mexico. One part of this project called the Sloan Extension for Galactic Understanding and Exploration or SEGUE which was completed earlier this year was to measure the colour of some 240,000 stars in the Milky Way.

Now Jelte De Jong at the Max-Planck-Institut fur Astronomie in Germany and a few pals have used this data to estimate the distance of each of these stars using the colour magnitude diagram. The result is a new 3-D map of the galaxy, part of which is shown above (each map is a slice through the galaxy, centred on the Sun).

That’s an important stepping stone towards a better understanding of our galaxy’s evolution. For example the map immediately shows how the metal content in stars varies in three dimensions across the galaxy

But there’s far more to be mined from this map. Astronomers believe that galaxies form and evolve through accretions and mergers with other smaller bodies. These events leave their mark on the structure of the galaxy and the movement of the stars within it.

De Jong and friends say they can see in their map various structures such as the Sagittarius stream which is the result of the Milky Way’s interaction with the Sagittarius dwarf galaxy.

However the origin of other features is far less well understood. In particular, the increased density of stars in the direction of Virgo and Monoceros are puzzling. The promise of the new map is that it might reveal the origin of these features. Exciting stuff.

Ref: http://arxiv.org/abs/0911.3900: Mapping The Stellar Structure of The Milky Way

ljk January 18, 2011 at 20:13

Kona Galaxy Garden

Credit & Copyright: Garden by Jon Lomberg; Kite Aerial Photography by Pierre and Heidy Lesage

Explanation: How does your galaxy grow? Quite contrary to a typical galaxy, this one needs water to flourish. Pictured above as it appears at the Paleaku Peace Gardens Sanctuary in Kona, Hawaii, USA, a meticulously planned garden spanning about 30 meters provides a relatively accurate map of our Milky Way Galaxy. Different plants depict stars, globular clusters, and even nebulas. Many bright stars visible in Earth’s night sky are depicted on leaves surrounding the marked location of the Sun.

Plant rows were placed to represent arms of our Galaxy, including the Sun’s Orion Arm, the impressive Sagittarius Arm, and the little discussed Norma Arm. A small bar runs through our Galaxy’s center, while a fountain has been built to represent the central black hole. What a stellar use of space!

http://antwrp.gsfc.nasa.gov/apod/ap110118.html

ljk May 18, 2011 at 0:30

http://www.technologyreview.com/blog/arxiv/26763/

Milky Way Is Warped, Like a Beer Bottle Cap

The discovery of a new arm in the Milky Way suggests that our galaxy is warped, say astronomers

kfc 05/16/2011

In 1852, Stephen Alexander, an astronomer at the College of New Jersey, put forward the radical suggestion that the Milky Way galaxy is a spiral.

But while today’s astronomers agree on this general shape, they disagree over the precise structure of the spiral and in particular on the number of arms.

Astronomers have named at least 6 arms and in the 1990s, evidence emerged that the galaxy had a central bar. The uncertainty is easy to understand. Our view of the galaxy shows the nearer stars superimposed on the ones that are further away. And much of the opposite side of the Milky Way galaxy is obscured entirely by the central mass of stars at the centre.

Recently, however, a clearer picture has begun to emerge. The growing consensus is that the Milky Way has a central bar with two main arms, called the Perseus Arm, which passes with a few kiloparsecs of the Sun, and the Scutum-Centaurus Arm. (The other arms are now thought to be minor structures made up largely of gas.)

Today, Thomas Dame and Patrick Thaddeus at the Harvard-Smithsonian Center for Astrophysics in Cambridge provide further evidence of this 2-arm structure but with a twist that explains why astronomers have previously been unable to see it clearly.

Astronomers traditionally study the Milky Way’s structure by measuring the movement of large clouds of hydrogen and carbon monoxide gas within it (the velocity of distant stars being too difficult to pin down).

The new evidence that Dame and Thaddeus have accumulated shows the existence of a new arm on the other side of the Milky Way, but further from the centre than we are. The new arm is 18 kpc long and so stretches some 50 degrees across the sky.

Dame and Thaddeus conclude that this arm is an extension of the Scutum-Centaurus Arm, the rest of which is obscured behind the galactic middle.

That makes sense. The Perseus arm, which we can see more clearly, wraps 300 degrees around the galactic centre. If Dame and Thaddeus are correct, the Scutum-Centaurus Arm must be exactly symmetrical with this. That makes the Milky Way similar to the Great Barred Spiral, a barred, twin spiral some 56 million light years from here.

But why has it taken astronomers so long to find the end of this arm? The reason, says Dame and Thaddeus, is that this arm is bent. Sot it’s not in the galactic plane but slightly above it.

Which means the Milky Way is warped, like the cap from a freshly-opened beer bottle.

Ref: http://arxiv.org/abs/1105.2523: A Molecular Spiral Arm in the Far Outer Galaxy

ljk May 21, 2011 at 21:44

Milky Way Galaxy Has Mirror-Like Symmetry

By Ron Cowen, Science News May 21, 2011 | 7:00 am | Categories: Space

A new study suggests the Milky Way doesn’t need a makeover: It’s already just about perfect.

Astronomers base that assertion on their discovery of a vast section of a spiral, star-forming arm at the Milky Way’s outskirts. The finding suggests that the galaxy is a rare beauty with an uncommon symmetry — one half of the Milky Way is essentially the mirror image of the other half.

Thomas Dame and Patrick Thaddeus of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., say the structure they’ve discovered is most likely the outer extension of the Scutum-Centaurus arm from the inner galaxy. The finding suggests that Scutum-Centaurus wraps all the way around the Milky Way, making it a symmetric counterpart to the galaxy’s other major star-forming arm, Perseus.

The two arms appear to extend from opposite ends of the galaxy’s central, bar-shaped cluster of stars, each winding around the galaxy, the researchers note in an upcoming issue of Astrophysical Journal Letters.

Full article here:

http://www.wired.com/wiredscience/2011/05/milky-way-symmetry/

ljk December 28, 2011 at 19:47

Mapping the Milky Way: William Herschel’s Star-Gages

Todd Timberlake

(Submitted on 15 Dec 2011)

In 1785 astronomer William Herschel mapped out the shape of the Milky Way star system using measurements he called “star-gages.” Herschel’s star-gage method is described in detail, with particular attention given to the assumptions on which the method is based.

A computer simulation that allows the user to apply the star-gage method to several virtual star systems is described. The simulation can also be used to explore what happens when Herschel’s assumptions are violated.

This investigation provides a modern interpretation for Herschel’s map of the Milky Way and why it failed to accurately represent the size and shape of our galaxy.

Comments:

9 pages, 6 figures

Subjects:

History and Philosophy of Physics (physics.hist-ph); Galaxy Astrophysics (astro-ph.GA)

Cite as:

arXiv:1112.3635v1 [physics.hist-ph]

Submission history

From: Todd K. Timberlake [view email]

[v1] Thu, 15 Dec 2011 20:17:37 GMT (679kb,B)

http://arxiv.org/abs/1112.3635

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