Galaxies
esiegel | May 26, 2012"This seems to be the law of progress in everything we do; it moves along a spiral rather than a perpendicular; we seem to be actually going out of the way, and yet it turns out that we were really moving upward all the time." -Frances Willard
As spring gives way to summer here in the Northern Hemisphere, one of the most beloved sights of the night sky becomes ever more prominent: the Big Dipper.
(Image credit: NASA, ESA, Z. Levay (STScI) and A. Fujii.)
These seven bright stars shine high above the horizon after sunset, and will continue to do so over the rest of the Spring and all Summer…
esiegel | April 19, 2012"Science progresses best when observations force us to alter our preconceptions." -Vera Rubin
I want you to think about the Universe. The whole thing; about everything that physically exists, both visible and invisible, about the laws of nature that they obey, and about your place in it.
It's a daunting, terrifying, and simultaneously beautiful and wondrous thing, isn't it?
Image credit: NASA, ESA, S. Beckwith (STScI) and the HUDF Team.
After all, we spend our entire lives on one rocky world, that's just one of many planets orbiting our Sun, which is just one star among hundreds of billions…
esiegel | April 13, 2012"If we knew what it was we were doing, it would not be called research, would it?" -Albert Einstein
Our galaxy is but one among hundreds of billions in the cosmos, nearly all of which contain supermassive black holes at the center. Ours happens to be "only" a few million times as massive as our Sun, as well as quiet.
Image credit: ESO, R. Genzel et al. at MPI fur Extraterrestrische Physik.
In other words, our galaxy's supermassive black hole is behaving right now, by not viciously shooting off high-energy jets of particles and light at some poor, innocent passers-by.
But other galaxies are…
esiegel | April 11, 2012"We were left with a picture of part of the sky with no stars or galaxies, but it still had this infrared glow with giant blobs that we think could be the glow from the very first stars." -John Mather
When you look out at the night sky, you're limited by the light pollution from your surroundings, the imperfections of our atmosphere, the light-blocking gas and dust throughout the interstellar and intergalactic medium, and the capabilities of your eyes. Still, what one can see is truly a sight to behold.
Image credit: IronRodArt - Royce Blair of NightScapePhotos.com.
What if you didn't have…
esiegel | March 29, 2012"[The black hole] teaches us that space can be crumpled like a piece of paper into an infinitesimal dot, that time can be extinguished like a blown-out flame, and that the laws of physics that we regard as 'sacred,' as immutable, are anything but."
-John A. Wheeler
To an astronomer on any other world, the most important object in our Solar System wouldn't be the Earth, but rather our Sun. Just one example of the hundreds of billions of stars in our galaxy, our Sun is a G-type star, burning at around 6,000 Kelvin and with a lifetime of around 10 billion years.
But stars come in a great variety…
esiegel | March 27, 2012"Think binary. When matter meets antimatter, both vanish, into pure energy. But both existed; I mean, there was a condition we'll call 'existence.' Think of one and minus one. Together they add up to zero, nothing, nada, niente, right? Picture them together, then picture them separating--peeling apart. ... Now you have something, you have two somethings, where once you had nothing." -John Updike
Looking out at our Universe, at the myriad of stars, galaxies, and, well, "stuff" in our Universe, it's hard not to ask yourself where it all came from.
Image credit: Rogelio Bernal Andreo, retrieved…
esiegel | March 21, 2012"Deep into that darkness peering,
long I stood there, wondering, fearing,
doubting, dreaming dreams no mortal
ever dared to dream before." -Edgar Allen Poe
When you look out into the darkness of a moonless, unpolluted night sky, you'll of course notice that it's full of stars, planets, and the occasional extended object.
Image credit: Bob King at AstroBob.
But you'll also notice that there are plenty of regions that -- other than a few stars -- don't really have very much going on. One such region, visible in the southern skies pretty much year-round, is the constellation of Sextans.…
esiegel | March 20, 2012"When I had satisfied myself that no star of that kind had ever shone before, I was led into such perplexity by the unbelievability of the thing that I began to doubt the faith of my own eyes." -Tycho Brahe
When stars reach the end of their lives, there are many possible fates that they can have. Among the most spectacular, however, are stars that end their lives by going supernova, where a single star can outshine even an entire galaxy for a brief moment in time.
Image credit: SN 2006gy, X-ray by NASA / CXC, Nathan Smith, Weidong Li et al., IR by PAIRITEL / Lick / U.C. Berkeley / J.Bloom,…
esiegel | March 5, 2012"I soon became convinced... that all the theorizing would be empty brain exercise and therefore a waste of time unless one first ascertained what the population of the Universe really consists of." -Fritz Zwicky
You very likely know that there are four fundamental forces in the Universe: gravity, electromagnetism, and the weak and strong nuclear forces. While only some particles experience the nuclear and electromagnetic forces, anything with mass or energy -- which is everything we know of -- is subject to gravity.
Image credit: CountInfinity by Ananth.
The strong nuclear force binds all…
esiegel | February 29, 2012"The Earth reminded us of a Christmas tree ornament hanging in the blackness of space. As we got farther and farther away it diminished in size. Finally it shrank to the size of a marble, the most beautiful marble you can imagine." -James Irwin
With everything that goes on in this world, from our daily lives to concerns around the globe, it's easy to forget just how vast the Universe is, and how small we all really are. You had so much fun playing with the Interactive Scale of the Universe tool a couple of weeks ago that I had to just give you a few things to ponder. We think of the Earth,…
esiegel | February 28, 2012"One mustn't look at the abyss, because there is at the bottom an inexpressible charm which attracts us." -Gustave Flaubert
The deepest depths of space, out beyond our atmosphere, our Solar System, and even our galaxy, hold the richness of the great Universe beyond. Stretching for billions of light years in every direction, there are structures large and small, dense and sparse, everywhere we've ever dared to look.
Image credit: R. Jay GaBany, Cosmotography.com.
In addition to the visible, luminous matter we see in the image above, there's both non-luminous normal matter and dark matter.…
esiegel | February 8, 2012"It took less than an hour to make the atoms, a few hundred million years to make the stars and planets, but five billion years to make man!" -George Gamow
Let's pretend that, for all of our history on Earth, we had never once bothered to look up with any instruments beyond what our own eyes could offer. Imagine that all the technology we'd have would be the same -- telescopes, electronics, GPS, etc. -- as would our fundamental scientific knowledge -- Einstein's General Relativity, the Standard Model of Particle Physics, etc. -- but we had just never bothered to turn our attentions toward the…
esiegel | January 11, 2012"I soon became convinced... that all the theorizing would be empty brain exercise and therefore a waste of time unless one first ascertained what the population of the Universe really consists of." -Fritz Zwicky
Making the entire Universe isn't easy. Even with 13.7 billion years of time, general relativity and all the known particles in the Universe, we still can't reproduce all the observations we see today.
Image credit: Canada-France-Hawaii Telescope LenS team.
What does it take to get galaxies to form and cluster together the way they do in the Universe?
The large-scale structure in the…
esiegel | January 4, 2012"At the last dim horizon, we search among ghostly errors of observations for landmarks that are scarcely more substantial. The search will continue. The urge is older than history. It is not satisfied and it will not be oppressed." -Edwin Hubble
Given the relative peace of our night skies, combined with the vast distances from our Solar System to the nearest star, we don't often think about the cosmic catastrophes that took place in our past. But these catastrophes are the very things that gave rise to our Solar System in the first place!
Image credit: NASA, ESA and the Hubble Heritage (…
esiegel | December 30, 2011The size and age of the Cosmos are beyond ordinary human understanding. Lost somewhere between immensity and eternity is our tiny planetary home. -Carl Sagan
If the story of our entire Universe's history, from the last stages of inflation and the Big Bang up to the present day, were to be compressed into one calendar year, what would it look like?
As 2011 comes to an end, here's my final present of the year to you.
(As always, click for a more readable, higher-resolution version.)
Happy new year to all; may you all enjoy our shared story and journey while you celebrate. See you in 2012!
esiegel | December 22, 2011"A farmer travelling with his load
Picked up a horseshoe on the road,
And nailed if fast to his barn door,
That luck might down upon him pour;
That every blessing known in life
Might crown his homestead and his wife,
And never any kind of harm
Descend upon his growing farm." -James Thomas Fields
One of the greatest joys the Hubble Space Telescope has given us is the ability to peer deeper into the distant Universe than ever before. Not just at the giant, luminous galaxies visible with smaller, ground-based telescopes, but at the great sea of galaxies billions of light years away.
Image…
esiegel | December 14, 2011"I am undecided whether or not the Milky Way is but one of countless others all of which form an entire system. Perhaps the light from these infinitely distant galaxies is so faint that we cannot see them." -Johann Heinrich Lambert
One of the greatest discoveries of the 20th Century was that many of the great, faint, extended nebulae in the night sky were not merely objects within our own galaxy, like the stars. Rather, these objects were many millions of light-years distant, and were entire galaxies unto themselves.
Image credit: Boren-Simon 2.8-8 ED POWERNEWT Astrograph Image Gallery.…
esiegel | November 4, 2011"They credited us with the birth of that sort of heavy metal thing. Well, if that's the case, there should be an immediate abortion." -Ginger Baker
As hard as it may be to believe, take a look outside. I don't mean a glance, I mean to take a real look. At all the things there are to see -- the rocks, trees, mountains, skies, clouds, Sun, water, and everything alive -- all of it.
Image credit: Fir0002/Flagstaffotos, under the GFDL.
Now ask yourself, "what's it made of?"
At a fundamental level -- like everything else you know of -- everything on Earth is made of atoms. Oxygen, Hydrogen,…
esiegel | October 21, 2011"By now you must know that your father can never be turned from the Dark Side. So will it be with you." -Emperor Palpatine, Return of the Jedi
You've heard about dark matter. It's the notion that the Universe is somehow very much different than the small corner of it that we're most familiar with.
Photo credit: International Astronomical Union, retrieved from bbc.co.uk.
When we look at our Solar System, we can add up all the rocky planets, the gas giants, the asteroids, moons, and comets, as well as the entire Kuiper belt, and find out just how much of our neighborhood is dark.
And we can…
esiegel | October 17, 2011"The cave you fear to enter holds the treasure you seek." -Joseph Campbell
Space, as you know, is mostly empty, as the typical distance between galaxies far exceeds the size of the galaxies themselves.
But in a few select regions of the Universe, where the mass density is unusually above average, galaxies cluster together by the thousands. The closest huge cluster to us like this is the Coma Cluster, containing more galaxies than 95% of all known galaxy clusters.
Image credit: NASA / JPL-Caltech / L. Jenkins (GSFC).
One of the first thing you'll notice about these galaxies is, unlike our…