Meet the Itsy-Bitsy, Teeny-Weeny Galaxy

A massive swirl of stars like the Milky Way is not the only kind of galaxy out there — as a new pipsqueak member of the galactic community shows

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NASA / National Geographic / Getty Images

A bright blue newborn stars blast a hole through a nearby dwarf galaxy.

The late Carl Sagan got lots of praise for his brilliance in explaining science to the masses, especially on his PBS TV series Cosmos back in the 1980s. But he also got teased unmercifully for the super-geeky way he said “billions” — and given the subject matter, he said it a lot. The universe is billions of years old, and billions of light-years across, and contains a hundred billion galaxies, each containing a hundred billion stars…and Sagan got his teeth into every “billion” he could find.

Which is why he would be at something of a loss talking about a new report in The Astrophysical Journal describing the least massive galaxy every found. Known as Segue 2, it contains just 1,000 or so stars, and while this puny object, like most galaxies, is somewhat bulked up with invisible dark matter, that only adds another 100,000 stars’ worth. There’s not a billion to be found, unless you start weighing the stars and dark matter in pounds. “Finding a galaxy as tiny as Segue 2,” says co-author James Bullock, of the University of California, Irvine, “is like discovering an elephant smaller than a mouse.”

But it’s also very different. A mouse-sized elephant is the last thing you’d ever go looking for; a galaxy this tiny, by contrast, is something astronomers have long sought. The reason: it’s firmly established by now that most of the mass in the universe comes in the form of dark matter, not stars. The leading candidate for what makes up the dark matter is some sort of still-undiscovered subatomic particle. And computer models suggest that while these particles should coalesce into gigantic blobs or haloes that surround normal galaxies, they should  also form into thousands of much smaller clumps, buzzing around galactic fringes.

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Those smaller clumps would have their own tiny retinue of stars as well — and in 2006, astronomers finally found an example. Called Segue 1 (it was discovered by the Sloan Extension for Galactic Understanding and Exploration, or SEGUE, an offshoot of the Sloan Digital Sky Survey) it had a mere 300 or so stars, but its dark matter component was equivalent to about 600,000 stars — small, but not as small as what astronomers were hoping to find.

Then, in 2009, the SEGUE survey snagged a true pipsqueak: Segue 2 has three times the star count as its brother, but only one-sixth the dark matter — right in the ballpark of what theory says should be there. “It’s quite encouraging,” says Kirby.

Maybe, but it’s reasonable to wonder why you’d give a tiny thing like this a grandiose name such as “galaxy.” Why not just call it a star cluster? The answer, says lead author Evan Kirby, also at Irvine: a galaxy is defined as a system of stars that can enrich its own chemical composition. What that means is that the earliest stars were made almost entirely of hydrogen and helium. Those atoms were forged into heavier elements in the stars’ cores, and eventually blown out into space at high velocity in supernova explosions. The heavier elements, known as “metals,” then became incorporated into the next generation of stars (in astronomy jargon, iron and aluminum are metals, but so are oxygen and carbon).

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In a star cluster like the Pleiades, there isn’t enough gravity to keep those metals from flying away; in a galaxy, there is — and that gravity can come from either stars or dark matter, doesn’t matter which. Kirby and his team used the powerful Keck II telescope, in Hawaii, to measure the metal content of the stars in Segue 2, and found that they vary a lot. That’s evidence that some stars are younger, some older, and that the metals have stayed put. Puny or not, Segue 2 is  a galaxy. It’s also likely not to be the only one of its kind. “We think there are lots more,” says Kirby.

Unfortunately, those junior members of the galactic corps might not be easy to find. Spotting very dim collections of stars on the fringe of the Milky Way isn’t incredibly hard, but probing their light for evidence of metal composition, and measuring their orbital speeds as an indirect method of weighing their dark matter, is. The Keck II armed with an instrument called the DEIMOS spectrograph — among the world’s most powerful systems for doing this kind of work — can just manage it.

At this point, says Bullock, there’s no set of instruments, either in existence or on the drawing board, that could do a lot better. “Right now,” he says, “we’re thinking of what it would take.” Once the astronomers come up with something though, they’re betting that the little galaxies will be out there waiting.

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55 comments
a.gentleman49
a.gentleman49

We've got Harvard PhD's in my family and in my opinion, Carl Sagan was an idiot.

ElizabethMcBride-Lilleg
ElizabethMcBride-Lilleg

Cosmos is one of my favorite TV series of all time.  It was on when I was in early elementary school, and I absorbed every bit of it.  In first grade I was reading the book with my Dad before bedtime.  To this day, my view of the universe and my tiny place in it is strongly based on Carl Sagan's influence.  The wonders that the religious see as the gifts of God, I see as examples of the limitless possibilities and probabilities of the natural universe.

OccamsRazor1349
OccamsRazor1349

I love this stuff. Reminds me of how very insignificant we are in the grand scheme of things.

stefano3029
stefano3029

that's really cool that they're always discoveries new stuff out in space but the truth is everything that they are doing exploring space thus finding galaxies like segue 2 is amazing so small yet rich with beauty which is one of the reasons why astronomy is so interesting to do because in the process you learn amazing new things about the universe in which we live in so phenomenal

cheme911
cheme911

Guys,

I found the 95% dark/vacuum energy a year ago, where have you been? We call it our weather when actualy it is the decay of our quantum gravity field of energetic particles and strings from the sun in our atmosphere. It triggers vacuum condensing and vacuum evaporation and electromagnetic disturbances above our heads we call lightning. It is orbiting through our 5%.

darkmattersalot.com

DaveHinckley
DaveHinckley

I think Carl said "billions of billions", not "billions and billions".

RodVenger
RodVenger

They keep talking about 'dark matter' as if it's a fact and they come dangerously close to creating a pseudo-religion around it when they compose entire theories about how things work based on something they can't prove exists. Like as not, the 'missing matter' is bound up in black holes, whose actual mass they cannot determine, especially if much of that mass essentially exists outside of the Universe. My guess...the mass is in transit between holes, going in one, out the other, aka wormholes associated with the black holes.

texasghost01
texasghost01

He never said billions and billions...but he did say...billions a lot.

cpc65
cpc65

I've been watching episodes of Cosmos on Hulu lately. It was a great show. Some of the information is a bit dated as we learn more about the universe, but it's still great today.

Fun facts: Carl emphasized the B in billions to make sure it sounded distinct enough from millions so folks wouldn't get them mixed up. Also, just as nobody in Star Trek (tos) ever said, "Beam me up, Scotty!", Carl never said "Billions and billions" on Cosmos. That would be from Mr. Johnny Carson's great impersonations or Mr. Sagan on The Tonight Show. 

YoungbloodK
YoungbloodK

Wow, it touches my spirit to fathom the universe and how small we are as humans in the equation of life's vast cosmos.  I am always at awe with these types of pictures/articles to realize how insignificant and shabby we can behave as humans and miss understanding the majestic nature of the universe.  It seems we miss the point and squalor with trivial comments.  Humankind, humph!

MichaelJ.Arvizu
MichaelJ.Arvizu

It seems as if TIME has it in for Carl Sagan, based on just the first few sentences of this article.

CrystalShepard
CrystalShepard

Dr. Sagan didn't say "billions" in a super-geeky way.  The man had an accent.  I don't know whether the "super-geeky" comment shows ignorance of Dr. Sagan, a disdain for scientists, or a subtle form of racism.  Whatever it is, it's sad.

solex675
solex675

Seven comments in three hours. Quite a statement about our interest in science.

RuiPereira
RuiPereira

There is NO correlation between the theory of dark matter and the mass of this galaxy. Dark Matter is nothing more than a theory - with NO proof of any kind and ripe with conjuncture. The media is being taken in by theories that fill in the holes with made up concepts.

rrenegade
rrenegade

Typo:  least massive galaxy EVER found.  Not every found.

ScienceIsGood
ScienceIsGood

Why label a brilliant man such as Carl Sagan, one of the most brilliant men in human history, with the negatively connoted jibe "geeky"?

It does a disservice to people who take science and facts seriously. If you're going to write about science and scientists, don't apologize for being intellectual. If people are too stupid to pay attention or to get an education, that is THEIR fault.

DamonMontano
DamonMontano

@DaveHinckley He actually said "...billions upon billions..., but his final book was titled "Billions and Billions".

BenHigginbotham
BenHigginbotham

@RodVenger I'm sorry, that's not how it works.  Dark matter refers to the matter necessary to produce the gravitational effects recorded in the known 'verse.  It's name comes from the fact that it is not visible nor detectable via normal instrumentation.  Dark matter is just a theory, as is gravity, but it's a theory with a hypothesis supported by observation and mathematical calculation.  Also, it is possible to determine the mass of a black hole, based on its effects on its surroundings.

JenniferBonin
JenniferBonin

@CrystalShepard Actually, if you read his books, the reason he said it that way wasn't because of any accent.  It was because he wanted to be very clear that he wasn't saying "millions".

And as an aerospace engineer, I didn't get particularly offended by the comment in the article.  It WAS odd and sort of amusing.  But (as this article also implies) it didn't make him or his program any less brilliant.  I'll save my irritation for the times someone is actually being intentionally insulting, thank you.  It happens enough to engineers/scientists that I don't need to get too worked up about something this trivial.

humtake
humtake

@RuiPereira The problem is you think that scientists have proven dark matter.  No, all it is is a placeholder.  I explain it to people this way...dark matter is the part of our understanding that we don't yet understand.  It is an undefined constant.  As science gets better, more of the equation will be plucked out of the dark matter placeholder until eventually the dark matter placeholder is known by other calculations.

 Dark matter is not meant to be a proven concept.  It is meant to be a place holder that makes the laws of physics work while studying galaxies.  One day if we find out the laws of physics are not true, or understand they work differently, or they work differently in different circumstances (which we already know by quantum mechanics), then the dark matter constant is going to be changed also.  Until we can define dark matter by human logical expression, it is a placeholder that contains more than we can understand at this moment in time.

avidmag
avidmag

@RuiPereira Pretty sure physicists and cosmologists came up with the theory not the media. 

southmost
southmost

@RuiPereira I think you misunderstand the scientific meaning of "theory" (i.e. a conceptual model from which one can make testable predictions).  So yes, dark matter is a theory.  So is gravity.  We have a lot of confidence in our theory of gravity, so much so that just this morning I left my house without worrying that I would catapult into the sky.  But it's still just a theory.

When astronomers started measuring gravity on Galactic scales, they found that there wasn't enough visible matter to account for the motion of stars.  This led to two competing theories: either the theory of gravity needed to be modified, or there needed to be unseen matter present.  If we assume that the theory of gravity is correct, then it predicts that the unseen matter would also have other effects: it would bend light, producing distorted and multiple images of distant galaxies.  Astronomers started doing deep-field imaging to see if these effects were actually present, and lo and behold, they are!

This is how science works: make observations, come up with theories (often several competing theories) to explain those observations, make predictions based on those theories, test those predictions with more observations.  Rinse and repeat.  The connection between galactic motion and gravitational lensing, as explained by dark matter, is actually one of the finest recent tests and validations of our current theory of gravity.

Another_Travis
Another_Travis

What about gravitational lensing?  Or the fact that the laws of gravity (which we understand quite well) say galaxies would not be able to stay together with the amount of mass we see?  There's something out there that we don't see that definitely has mass.  That's dark matter.  Just because we don't really understand it doesn't mean we can't logically conclude that it exists.

JenniferBonin
JenniferBonin

@ScienceIsGood Actually, most scientists and engineers I know are PROUD to be called "geeky".  Partly because of people like Carl Sagan, who demonstrated the value and beauty in science and engineering, and that brainpower doesn't have to be considered "elitist" or stupid-looking.

What's wrong with being a "geek"?  I'm proud of my "geeky" sense of humor, my scientific mindset, and my interest in the universe.  If some humanities major wants to mock me for it, the joke's really on him.  Just because he can't see the beauty in a well-worked math problem doesn't make it any less elegant.  Just because he doesn't understand the science behind my fruit-fly-eyecolor joke doesn't make it any less amusing, either.  It just makes him ignorant and short-sighted, that's all.  And since there's nothing much I can do to change that, I choose to take his "insult" as the compliment it really is.

BillMarvel
BillMarvel


@ScienceIsGoodWith all due respect for Carl Sagan, whose books i avidly read as a kid, he was an important planetary astronomer who put the search for extra-terrestrial life on a firm footing. He was also a very talented popularizer of astronomy, 

But he was by no possible stretch of the imagination "one of the most brilliant men in human history." The competition for that title is simply too vast, counting only astronomers. If you expand the field to physics and the other sciences, he wouldn't even be in the running.

And, yes, he was geeky. Interesting, lovable, but geeky. 


WilliamClukey
WilliamClukey

@avidmag@YoungbloodK We're like a dot on a quark of a proton in an atom which is part of a speck on a mite on a dust particle resting on a tick on a dog. No, no: we are smaller still; yet, like the violence of quantum particles, we fight still.

RuiPereira
RuiPereira

@humtake @RuiPereira Dark matter is not proposed as a mathematical concept/constant - it is proposed as a real object. Gravity is not well understood - so the assumption that a 'placeholder' is required to fill in the missing mass needed to keep a galaxy spinning like a disk - with stars in a fixed position referenced to the centre - has been co-opted by the imagined dark matter. The problem is that our mathematical reference tools like time and space have taken on a life of their own - projecting them into the universe. Where abstraction leaves its purpose in the methodology of science and suddenly becomes part of the universe - the same way as a scale plan is not the physical building.

Like red shift - dark matter is slowly becoming a given - to the point that these theories/concepts/guesses are now prevalent in the media as fact. While red-shift has significant observational data - dark matter has a complete absence of detection. Dark matter is proposed as significant amounts of mass - on a galactic scale - unlike trying to detect gravity waves from binary stars dark matter should be everywhere. But it is not...so is it a concept or an object? You cannot have it both ways.

RuiPereira
RuiPereira

@southmost @RuiPereira No - gravity has demonstrable effects - walk off a cliff and you fall. However, as a force it is very poorly understood - dark matter on the other hand is just a guess - not even a theory - simply because it cannot be qualified or quantified. Consensus does not define the scientific method - and even the defenders of dark matter can deliver no direct proof of its existence. Dark matter is a fantastical response to a lack of understanding of gravity.

RuiPereira
RuiPereira

@Another_TravisGravitational lensing has nothing to do with dark matter. Gravity is not well understood and logic does not define proof. If dark matter was a universal form - it would exist everywhere - so where is it? As for the mass of galaxies (galaxies take many forms and are not all the same) - more BS that attempts to explain through fantasy their structure. 

Drumbum2112
Drumbum2112

Dark matter is just a made up concept to make the math work/. Gravitational lenseing is unrelated but also a flawed theory. The phenomenon observed is a result of temperal differential but Physics today have yet to figure that out. They think they can discount time in their theories and just tack it on in the end.

As light passed near an object of large mass, time is moving at a different rate than the rest of space. When light is seen through one of these regions where time is moving at a different rate, it only appears to move because the light waves are traveling at a different speed. Just like looking into a pond and seeing a fish that is a few inches from where it actually is. When the light hits the water it travles slower and also appears to shift. The Gravitational lensing theory works because the math is the same either way. The larger the mass, the larger the effect but it is not because gravity is pulling the light, it is because time is shifting the view. The two are directly proportional so the math works, but the theory is wrong. And yes, I am saying Einstein was wrong.

southmost
southmost

@RuiPereira @southmost The facts: Dark matter is so named because it refers to an entity that (a) produces gravitational effects, (b) has inertia (i.e. mass), (c) moves substantially slower than light, and (d) does not produce or obscure light (or have any other observed electromagnetic interactions).  There is specific empirical evidence establishing each of these properties.  But if you simply dislike the term "dark matter" and would prefer, say, "Massive sub-relativistic non-electromagnetic-interacting field", it's all the same to me.

Whether science can "prove" anything is, I think, a quibble over terminology.  Science accumulates empirical evidence favoring some models over others, sometimes to an overwhelming degree; but there are always -- always! -- alternative explanations.  Nonetheless, we don't discard a hard-earned theory simply because there is an alternative, or give every alternative equal weight: the scientist asks, What is the evidence that would favor those alternatives?  So, if not dark matter, then what other testable theory gives better results?  (This is not an entirely rhetorical question: there are alternative theories to dark matter that receive serious scrutiny, but the evidence we now have does not favor them.)

RuiPereira
RuiPereira

@southmost @RuiPereira Just the facts - just the facts. And the fact is that Dark Matter is called 'matter' for a reason. The assumption is that there is not enough of the 'regular' matter to account for the structure and behaviour of galaxies - galaxies clusters - in fact the whole universe. So the unproven theory of dark matter - new fantastical add on to the mysteries of gravity popped up. The problem is that this dark matter cannot be detected - only its apparent effects on the universe - this of course is nonsense - simply because there are limitations on the understanding of gravity does not mean that a new exotic matter exists.

Yes - things can be proven to exist...scientifically anyway - philosophically perhaps not. 

As for the notion of the holographic universe...that's another story.

southmost
southmost

@RuiPereira @southmost Dark matter has demonstrable effects, as I've described: both in motion of stars and galaxies, and bending of light.  These are solid, repeatable, and objectively verifiable observations just as much as falling off a cliff.  And dark matter certainly can be quantified; that's exactly what these observations do!  We can observe the motion of stars and say that, for instance, the Milky Way contains about a billion Solar masses worth of dark matter, the same way we can drop a ball off a cliff and infer that the Earth has a mass of six billion trillion tons.

Furthermore, nothing can be "proven" to exist: even that computer in front of you might just be an elaborate hallucination.  But if it behaves in a rational and predictable way, then you might as well operate under the assumption that it *does* exist, until presented with evidence that challenges this assumption.

Consensus does not define the scientific method, and I never claimed it does.  Neither does incontrovertible proof or complete understanding.  The scientific method is defined by repeatable observations and testable predictions, and dark matter satisfies these.

BillMarvel
BillMarvel

@RuiPereira Not a troll. But it matters a great deal to me. 

When it comes to matters that require enormous technical expertise and experience, I like to know who the information is coming from and what are his or her credentials.

I'm not disputing you. But the trouble is, all sorts of crackpots make assertions here, especially when the subject is science, without bothering to back them up with evidence and coherent argument. It shouldn't be too difficult for you to lay out your credentials for all to see. Are you an astronomer, or a physicist? A cosmologist?  I'd be especially interested in exploring your contention that dark matter would have nothing o do with gravitational lensing, since that would seem to defy common sense, and the mathematics has already been worked out.

RuiPereira
RuiPereira

@WilburFinklebaum @RuiPereira @Another_Travis the universe is thought to be homogenous - from observational mapping - so effectively both matter and dark matter could be everywhere. It is not a question of uniformity like painting a wall - but rather the distribution of structures - stars - galaxies - matter throughout the universe.

WilburFinklebaum
WilburFinklebaum

@RuiPereira @Another_Travis Matter does not "exist everywhere" either. Nor is it even uniformly placed throughout the universe. So why would dark matter "exist everywhere"? 

Science is about theory based on the evidence, there are no facts.

I honestly believe, based on the incoherent subjects of your posts and your misuse of terminology, that you are cutting and pasting various statements from other sources on teh subject together in an effort to sound informed. the reality of this is that you don't seem to grasp the basic concepts of the topic at all.

hellifuknow
hellifuknow

@RuiPereiraOk then, please quantify gravity, which is also "just" a theory. And while you're at it, please explain how you know that there is no dark matter here on earth or next to the sun or everywhere else in the universe.

RuiPereira
RuiPereira

@Drumbum2112 Nonsense - has nothing to do with me. Where is dark matter - quantify it. Completely ridiculous notion - considering that dark matter defies the concept of universality and the homogeneous nature of the universe - inherent concepts within the theory of dark matter. So why is it not here on earth or hanging out next to the sun - or for that matter in any detectable form.

Drumbum2112
Drumbum2112

You better get started re writing general relitivity and then call the people at the Collider and tell them the HIggs feild they just found does not exist either. LOL

Drumbum2112
Drumbum2112

Your lack of undertanding does not mean it does not exist.

Drumbum2112
Drumbum2112

True, mostly. Time and gravity are connected at a fundamental level. Gravity increases with mass indicating it should be part of the standard model but it is not because we know little about it. You can't just tack it on the end and say and then there is gravity and time. these things matter at an atomic level.

RuiPereira
RuiPereira

@Another_Travis time has nothing to do with any of this - especially since time does not exist and is only a concept used to define numerically - how long something takes to happen. The same way as space does not exist and is only the distance - in three dimensions between objects. The fact that matter and quantum processes seem to slow down and speed up is not a definer of time - but rather the localized behaviour of matter relative to other objects in the universe.

Another_Travis
Another_Travis

We have observed the gravitational lensing effect throughout the universe.  Whether the light is being bent by a gravitational distortion (gravitational lensing) or by going through a space in which time is moving at a different rate, there's still something there that we don't see.