Galaxies
esiegel | January 6, 2015“With an eye made quiet by the power of harmony, and the deep power of joy, we see into the life of things.” -William Wordsworth
You've seen the amazing photos of spiral galaxies, with the vast, sweeping arms, the massive, central bulges and the great underdense regions in between the arms. As you move farther and farther towards the outskirts, the stellar density drops away to practically nothing.
Image credit: Vicent Peris (OAUV), José Luis Lamadrid (CEFCA), Jack Harvey (SSRO), Steve Mazlin (SSRO), Ivette Rodríguez (PTeam), Oriol Lehmkuhl (PTeam), Juan Conejero (PixInsight), via http://…
esiegel | December 29, 2014“The larger the island of knowledge, the longer the shoreline of wonder.” -Ralph W. Sockman
After millennia looking up at the Milky Way overhead, it's only recently that we discovered our galaxy had a spiral-like structure, and that the other spirals and ellipticals in the night sky are galaxies much like our own. But how did they come to be? Why do they appear the way they are? And what will come of them in the future?
Find out the answers to all these questions and more on the third episode of Genesis, where we focus on the galaxy and where it comes from!
(And if you missed either of the…
esiegel | November 14, 2014“Sometimes, I sit alone under the stars
and think of the galaxies inside my
heart, and truly wonder if anyone will
ever want to make sense of all that
I am.” -Testy McTesterson
The largest galaxies in the Universe all have a few things in common: they all contain many trillions of stars, they all contain many times their stellar mass in the form of dark matter, and they're all found towards the centers of great galactic clusters.
Image credit: ESO and Digitized Sky Survey 2. Acknowledgment: Davide De Martin. Via http://www.eso.org/public/images/eso0949m/.
Oh, and one more thing: none of…
esiegel | September 10, 2014“I was confided to your loyalty and accepted by your treason; you offer my death to those to whom you had promised my life. Do you know who it is you are destroying here? It is yourself.” -Victor Hugo
So those of you who've been paying attention may have just heard that we've mapped out our supercluster of galaxies -- Laniakea -- to unprecedented accuracy, identifying a region 500 million light-years in diameter that's responsible for our local group's motion through space.
Image credit: R. Brent Tully (U. Hawaii) et al., SDvision, DP, CEA/Saclay, of Laniakea, our local “supercluster” of…
esiegel | August 26, 2014When you look out at the Universe, it comes as no surprise that it's full of galaxies, each one with a dense, central collection of brilliant stars and an intricate structure all their own. They come in all sorts of structural varieties, with some in isolation, others in small groups, and still others in huge, massive clusters.
An SDSS image of elliptical galaxy NGC474 (center) and spiral galaxy NGC470 (right).
The bright galaxies we see are huge collections of billions of stars, with large intrinsic surface brightnesses. But surely there are components to these entities -- less dense…
esiegel | August 13, 2014“To be loyal to myself is to allow myself to grow and change, and challenge who I am and what I think. The only thing I am for sure is unsure, and this means I’m growing, and not stagnant or shrinking.” ‐Jarod Kintz
But for the Universe, although it's constantly changing, growing in a gravitational sense is a thing of its past. Sure, we continue to form new stars, galaxies continue to merge, and the structure we see on the largest scales continues to evolve.
Image credit: Bob Franke, via http://bf-astro.com/.
But there once was a time when there were no stars, no galaxies, and no groups or…
esiegel | May 26, 2014“Man must rise above the Earth, to the top of the atmosphere and beyond, for only thus will he fully understand the world in which he lives.” -Socrates
It's hard to believe that it's been nearly two years since we started our Messier Monday series, and so with only 110 objects to go through, we're actually starting to run out of objects! The most numerous type of object in the Messier Catalogue are the galaxies, but only a handful of those remain.
Image credit: The Messier Objects by Alistair Symon, from 2005-2009, via http://www.woodlandsobservatory.com/messier_map.htm.
Still, the richest…
esiegel | May 19, 2014“Ali always said I would be nothing without him. But what would he have been without me?” -Joe Frazier
We don't normally think of deep-sky objects -- seemingly fixed structures in the sky -- as fighting for their lives, but when you're a spiral galaxy caught in a gravitational storm, that's exactly what you're up against!
Image credit: Blackwater Skies 2013-14, via http://www.blackwaterskies.co.uk/2013/09/widefield-in-virgo-cluster-of-….
With some 2,000 other galaxies, densely clustered towards the center, what are you to do if you're a very large spiral headed through that region at…
esiegel | April 30, 2014“What you do is, you have your drawing board and a pencil in hand at the telescope. You look in and you make some markings on the paper and you look in again.” -Clyde Tombaugh, discoverer of Pluto
We often make a big distinction between professional and amateur today, and very rarely expect to find amateurs whose contributions to a major scientific enterprise will change the field forever. Yet back in the 19th Century, even astronomy and physics -- arguably the most developed of the sciences at the time -- had room for pioneers from all walks of life.
Image credit: Copperplate engraving…
esiegel | April 28, 2014“Fantasy is a necessary ingredient in living, it’s a way of looking at life through the wrong end of a telescope. Which is what I do, and that enables you to laugh at life’s realities.” -Dr. Seuss
With 110 objects in the Messier catalogue, and 40 galaxies (more than any other class of object), you might take a "if you've seen one, you've seen them all" attitude. But if you did, you'd be missing out on some truly amazing facts and phenomena happening right here in our own backyard!
Image credit: courtesy of Sloan Digital Sky Survey/WIKISKY, via http://www2011.mpe.mpg.de/highlights.html.…
esiegel | April 21, 2014“The line that describes the beautiful is elliptical. It has simplicity and constant change. It cannot be described by a compass, and it changes direction at every one of its points.” -Rudolf Arnheim
It's not every day that a nearby, well-studied galaxy turns your understanding of an entire class of common objects -- in this case, elliptical galaxies -- on its head. But Messier 105 is not your typical elliptical galaxy!
Image credit: Rick Beno of Conferring With The Sky Observatory, via http://www.conferringwiththesky.org/displayimage.php?pid=500.
At 32 million light-years distant, it's…
esiegel | April 14, 2014“All is well, provided the light returns and the eclipse does not become endless night. Dawn and resurrection are synonymous. The reappearance of the light is the same as the survival of the soul.” -Victor Hugo
During all other full Moons, I wouldn't dare show you a galaxy for Messier Monday. But when you get a total lunar eclipse on the occasion, not only do the nebulous deep-sky objects become visible, but Mars will be a more worrisome source of light pollution than the totally eclipsed Moon!
Image credit: Bethany and Amanda VanStavern at NOAO, via https://www.noao.edu/outreach/aop/…
esiegel | April 7, 2014“When we are sure that we are on the right road there is no need to plan our journey too far ahead. No need to burden ourselves with doubts and fears as to the obstacles that may bar our progress. We cannot take more than one step at a time.” -Orison Swett Marden
Every Messier Monday, we've taken a look at one of the 110 remarkable and unique deep-sky objects that make up the Messier catalogue. Of all these objects, the galaxies are the largest, most distant and also the most numerous. But only one of these galaxies can be the farthest of them all!
Image credit: Steve Mandel / Adam Block /…
esiegel | March 31, 2014“I recognize my limits, but when I look around I realise I am not living, exactly, in a world of giants.” -Giulio Andreotti
There are a huge number of deep-sky objects visible from Earth, and every Monday -- with the Messier Monday series -- I've made it my goal to tell you about one of them in spectacular fashion.
Image credit: Tenho Tuomi of Tuomi Observatory, via http://www.lex.sk.ca/astro/messier/index.html.
But only one can be the largest of them all. For today's Messier Monday, meet our supercluster's largest, most gigantic galaxy: Messier 87!
Image credit: John C. Smith of Hidden…
esiegel | March 24, 2014“We’ll ride the spiral to the end and may just go where no one’s been.” -Tool
A beautifully undisturbed, large spiral can be found right at the heart of the Virgo Cluster. Sure, looking at the heart of the Virgo Cluster on its own, you might totally overlook today's Messier object.
Image credit: Rogelio Bernal Andreo of Deep Sky Colors.
But you sure would be missing out if you did! Larger than the Milky Way, with a supermassive black hole more than 20 times the size of our own, a super hot, ionized central region, and speeding through the intergalactic medium at 1,000 km/s -- stripping its…
esiegel | March 10, 2014“[L]ife is a luminous halo, a semi-transparent envelope surrounding us from the beginning of consciousness to the end.” -Virginia Woolf
One of the only members of the Virgo Cluster… that isn’t located in Virgo!
When it comes to wonders of the night sky, you might think that if you've seen one galaxy, you've seen them all. But much like our own Milky Way, each one has its own history, its own present, and its own future. To each of its hundred billion stars and all their planets, it's the most important galaxy in the Universe.
Image credit: © 2006 — 2012 by Siegfried Kohlert, via http://www.…
esiegel | March 3, 2014“We find that we live on an insignificant planet of a humdrum star lost in a galaxy tucked away in some forgotten corner of a universe in which there are far more galaxies than people.” -Carl Sagan
A galaxy very different from our own may hold the key to seeing what our far future looks like.
If you've ever had the opportunity to see the Virgo cluster of galaxies, you probably think of a wonderland of galaxies littering the sky. Something like this, perhaps.
Image credit: © 2014 Scott Rosen’s Astrophotography, via http://www.astronomersdoitinthedark.com/index.php?c=113&p=512.
But did…
esiegel | February 24, 2014“Some day I hope to meet you. When that happens you’ll need a new nose, a lot of beefsteak for black eyes, and perhaps a supporter below!” -Harry Truman, to a music critic who panned his daughter’s singing
When you think about the Messier objects in the night sky, you hope for skies like the ones coming up over the next few days. The Virgo cluster and a slew of deep-sky objects rise in the east in the early part of the night, a waning Moon that won't rise until after midnight holds the potential for excellent deep-sky seeing, and the 40 galaxies that make up the 110 objects of the Messier…
esiegel | February 7, 2014"That which you create in beauty and goodness and truth lives on for all time to come." -Denis Waitley
It's been another spectacular week here in the Universe, and I'm pleased to take on another one of your wonderful questions in yet another Ask Ethan column! (Keep sending in your questions and suggestions if you have them.) This week's question comes from Robert Scott, and it's one of the simplest yet also the most puzzling:
I love looking at the beautiful long-exposure pictures of the Milky Way on the internet. I also love pictures of galaxies. One of my favorites is of Andromeda. I've…
esiegel | January 10, 2014“The fact that we live at the bottom of a deep gravity well, on the surface of a gas covered planet going around a nuclear fireball 90 million miles away and think this to be normal is obviously some indication of how skewed our perspective tends to be.” -Douglas Adams
Even though our main blog has moved, I'm so glad that the questions and suggestions have still been pouring in, because it's time for another entry in our Ask Ethan series! Today's question comes from professional physicist Marty Olsson, who asks:
I have been bothered for a long time why the Milky Way looks curved, sort of like…