A lopsided spiral galaxy
Click for full image.
For a change, today’s cool image is not from Mars, but instead goes deep into space. The photo to the right, reduced to post here, was taken by the Hubble Space Telescope of the relatively nearby spiral galaxy NGC 2276, located about 120 million light years away. As the caption explains:
The magnificent spiral galaxy NGC 2276 looks a bit lopsided in this Hubble Space Telescope snapshot. A bright hub of older yellowish stars normally lies directly in the center of most spiral galaxies. But the bulge in NGC 2276 looks offset to the upper left.
In reality, a neighboring galaxy to the right of NGC 2276 (NGC 2300, not seen here) is gravitationally tugging on its disk of blue stars, pulling the stars on one side of the galaxy outward to distort the galaxy’s normal fried-egg appearance. This sort of “tug-of-war” between galaxies that pass close enough to feel each other’s gravitational pull is not uncommon in the universe. But, like snowflakes, no two close encounters look exactly alike.
The scientists also note that the bright edge along the galaxy’s north and west perimeter mark regions of intense star-formation. In those same regions astronomers six years ago identified the first medium-sized black hole ever found.
On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.
The print edition can be purchased at Amazon or from any other book seller. If you want an autographed copy the price is $60 for the hardback and $45 for the paperback, plus $8 shipping for each. Go here for purchasing details. The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.
The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News
Click for full image.
For a change, today’s cool image is not from Mars, but instead goes deep into space. The photo to the right, reduced to post here, was taken by the Hubble Space Telescope of the relatively nearby spiral galaxy NGC 2276, located about 120 million light years away. As the caption explains:
The magnificent spiral galaxy NGC 2276 looks a bit lopsided in this Hubble Space Telescope snapshot. A bright hub of older yellowish stars normally lies directly in the center of most spiral galaxies. But the bulge in NGC 2276 looks offset to the upper left.
In reality, a neighboring galaxy to the right of NGC 2276 (NGC 2300, not seen here) is gravitationally tugging on its disk of blue stars, pulling the stars on one side of the galaxy outward to distort the galaxy’s normal fried-egg appearance. This sort of “tug-of-war” between galaxies that pass close enough to feel each other’s gravitational pull is not uncommon in the universe. But, like snowflakes, no two close encounters look exactly alike.
The scientists also note that the bright edge along the galaxy’s north and west perimeter mark regions of intense star-formation. In those same regions astronomers six years ago identified the first medium-sized black hole ever found.
On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.
The print edition can be purchased at Amazon or from any other book seller. If you want an autographed copy the price is $60 for the hardback and $45 for the paperback, plus $8 shipping for each. Go here for purchasing details. The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.
The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News
Great Pic!!! $ir !
….
…. and the Heavens proclaim …
Wondering how Kepler’s Third Law would affect stars and their systems. I would think that as the galaxy’s major axis expanded, stars would whip around the core fast enough that the night sky would have noticeable changes in a lifetime.
Kepler’s Third Law;
“Kepler discovered that the size of a planet’s orbit (the semi-major axis of the ellipse) is simply related to sidereal period of the orbit”
For instance, the days between winter solstice and summer solstice are equal. Spring equinox to fall equinox is seven days longer than the opposite do to earths elliptical orbit.
Gravity is weak, you must be near a large mass to feel its affect. Which gets weaker quickly the further you get from that mass.
bkivey said;
“Wondering how Kepler’s Third Law would affect stars and their systems. I would think that as the galaxy’s major axis expanded, stars would whip around the core fast enough that the night sky would have noticeable changes in a lifetime.”
The far side of the galaxy appears to be pulled towards the center mass accelerating. So that’s probably true…
For the most part, the stars at the inner core move slower than those in the middle or towards the edge of the galaxy. It’s not Newtonian physics so they came up with dark matter to explain it. (Which only confused things without resolving the issue)
Because most galaxies turn like a record player, all about the same rate, the speed increasing the further you get from the center, there must be something else at work. This picture is a good example of the influence of a gravity of a Galaxy nearby. It pulls everything out of whack, a obvious response to its presence indicating that it’s the combined “mass of the galaxy” which holds everything in check with each other.
Other words, A slow moving star will drop towards the strongest gravitational attraction, the center, where all the slow stars go.
A fast moving star will find itself on the edge of the galaxy trying to escape but being held in place by the combining of the weak gravity of all the billions of stars in the galaxy.
A great example of this is the “irregular galaxy” which is the most common and looks like a fuzzy snowball. Every star has its own elliptical path through the center of it’s galaxy accelerating until it comes out the other side and is pulled back in for another pass.
Untill another Galaxy’s gravity comes near and gives a little tug. Something Andromeda will do to our galaxy someday.
Kepler’s Third Law applies to elliptical orbits in a two body system. One could think of the second galaxy, as it relates to a star in the first galaxy, as a third body, which makes Kepler’s Third Law inappropriate. Even within the first galaxy, Kepler’s Third Law does not apply, because it is also not a two body system.
Gravity drops off with increasing distance from a mass by the inverse square law. This is why orbits are elliptical in the first place. However, once inside a sphere of uniform density, gravity drops off linearly with decreasing distance to the center. Thus, maximum gravity is felt on the surface of the sphere. This would be a similar phenomenon for a disk of uniform density, which is almost a reasonable model for a spiral galaxy (the center of which is typically more dense than the rest of the disk, which isn’t really uniformly dense, either). I’m not sure what shape a non-circular orbit would take, inside a galaxy, but the mass distribution means that usual (two body) laws of orbital mechanics don’t apply.
The universe is a weird place.