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Journey into a black hole 
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Joined: Wed Mar 18, 2009 3:10 pm
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I thought this was pretty interesting.

http://jilawww.colorado.edu/~ajsh/insidebh/schw.html


Tue Mar 31, 2009 1:22 pm
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I've seen a rendering of that kind of thing before, but this one looks nicer, and I hadn't heard about the appearance of approaching a flat plane as you reach the singularity.

The author also linked to the Hubble image gallery site a lot. I hadn't seen that site before, lots of cool images! Forgive me while I spam:

http://hubblesite.org/gallery/album/gal ... large_web/
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http://hubblesite.org/gallery/album/gal ... large_web/
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http://hubblesite.org/gallery/album/gal ... large_web/
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http://hubblesite.org/gallery/album/neb ... large_web/
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http://hubblesite.org/gallery/album/neb ... large_web/
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These next two are of the same star, a red giant, two years apart--the echo from a light flash it emitted in 2002 is going through the gas around it (the second is my own edit so that they're the same scale):

http://hubblesite.org/gallery/album/neb ... large_web/
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http://hubblesite.org/gallery/album/neb ... large_web/
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http://hubblesite.org/gallery/album/neb ... large_web/
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http://hubblesite.org/gallery/album/neb ... large_web/
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http://hubblesite.org/gallery/album/neb ... large_web/
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http://hubblesite.org/gallery/album/neb ... large_web/
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http://hubblesite.org/gallery/album/neb ... large_web/
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=D


Tue Mar 31, 2009 5:05 pm
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NASA has started releasing images taken with Hubble's new camera:

http://internal.hubblesite.org/newscent ... large_web/

Wikipedia says:
Quote:
The latest servicing should allow the telescope to function until at least 2014, when its successor, the James Webb Space Telescope (JWST), is due to be launched. The JWST will be far superior to Hubble for many astronomical research programs, but will only observe in infrared, so it will complement (not replace) Hubble's ability to observe in the visible and ultraviolet parts of the spectrum.

Dang. Where's our Hubble II?? :|

EDIT: One possibility is the Advanced Technology Large-Aperture Space Telescope ("ATLAST"), but even if approved, that wouldn't get into space until 2025-2035.


Sat Sep 12, 2009 5:31 pm
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The galactic center on Wikisky

Pretty cool composite interactive view of the night sky combining various survey and observatory sources, could use slightly faster servers. :p

There's also Google Sky, but their image is quite bland. Here's the one from Wikisky:

Image
(image from Sloan Digital Sky Survey)


Mon Sep 21, 2009 9:41 pm
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The Eta Carinae Nebula:

Image
(image from NASA/ESA)

This is a shrunk and -90-degree rotated version of the 90 MB JPG version (29,566 × 14,321 pixels) you can get from the image's page on Wikipedia. The image is false color: red is sulfur, green is hydrogen, blue is oxygen. The image above is about 50 light years tall.

Hubblesite has an interactive version (pan and zoom).

The binary star or cluster Eta Carinae, visible at the lower center of my rotated version as a large white egg shape with dotted lens flares radiating in the cardinal directions, has a mass estimated at 100-150 of our Suns, and is 4 million times brighter (although 99% of its luminosity is in the infrared).

(It is not the most massive or brightest star known, however; that would be the Pistol Star, which is near 200 solar masses, and close to the Galactic Center, where it is blocked from our optical view by dust clouds.)

EDIT: The Pistol Star has been downgraded in mass estimates to 80-150 solar masses. There's another candidate for most massive star, the Peony Star, currently rated at 175 solar masses, but not clearly seen and I betcha it'll be downgraded to sub 150 solar masses when they get a better look at it, because above 150, stars quickly break down due to the extreme energy of the gamma rays they're generating by fusion.


Tue Sep 22, 2009 12:45 am
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Eta Carinae, 7500-8000 light years from Earth, had a "supernova imposter" event observed in 1843: it became nearly as bright as a supernova, and was the second-brightest star in the sky after Sirius (which is a mere 8.6 light years away from us), but remained intact. It might have lost about 0.1% of its mass in that nova-like explosion. The small Homunculus Nebula around it is the result of that explosion:

Image
(image from NASA/ESA)

Explosions, the dust from them, and the still-somewhat-mysterious dynamics of the multiple star system, have caused its brightness to vary radically over its observed 350-year history:
Quote:
This star was first cataloged by Edmond Halley in 1677, as a star of fourth magnitude. Since, its brightness has varied in a most remarkable way: In 1730, its brightness reached mag 2, and again fell to mag 4 in about 1782. It brightened again about 1801 and faded back to 4th magnitude in 1811. In 1820, Eta began to brighten steadily, reaching 2nd magnitude in 1822 and 1st mag in 1827. After this first preliminary maximum, the star faded back to mag 2 for about 5 years, then rose again to about mag 0. After a further slight decline, Eta's brightness incresed once more and reached its maximal brilliance of nearly -1.0 in April 1843, when it outshone all stars in the sky but Sirius. After this brilliant show, the star slowly faded continuously, and became invisible in 1868. Interrupted by two minor outbursts around 1870 and 1889, Eta Carinae faded to about 8th magnitude around 1900, where it remained until 1941. At that time, the star began to brighten again, and reached 7th magnitude about 1953. Slowly and steadily, Eta Carinae became brighter until about 6th magnitude in the early 1990s - the star reached naked-eye visibility again at that time. Then in 1998-99, the star suddenly brightened by about a factor two. This behavior is not fully understood at this time (early 2000), and it seems hard to predict how this remarcable variable will develop in the future. [source]

Dust and gas from the last explosion are moving outward at about 1.5 million miles per hour (0.2% light speed); that's much slower than remnants from actual supernova explosions, which for instance in the case of the Crab Nebula (fifth image down in my first post in this thread) are expanding at 3.4 million miles per hour (0.5% light speed), and have been measured as fast as 1% light speed elsewhere.


Tue Sep 22, 2009 12:45 am
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The Spitzer Space Telescope's gallery is here:

http://gallery.spitzer.caltech.edu/Imag ... cal_Images

Spitzer is an infrared telescope, so most of the images are false-color.

~~~~~~~~~~~~~~~

This is the "Helix Nebula" in false color:

Image
(image from NASA; larger here)

The Helix is what's called a "planetary" nebula: the result of outer layers of gas being blown off a star whose core has collapsed to a white dwarf. The dwarf here is just visible as the white dot in the middle; the red disc around it is a dust circle, possibly from comets or planets that survived the wave of gas that blew outwards from the star.

The Helix Nebula is "only" 700 light years from Earth!


Wed Nov 04, 2009 4:49 am
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Our nearest spiral galaxy neighbor, the 2.5 million-light-years-distant Andromeda Galaxy, in Spitzer infrared:

Image
(image from NASA; larger here)


Wed Nov 04, 2009 4:51 am
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Visualizing scales:

The Milky Way is about 100,000 light years across. Andromeda, the closest spiral galaxy, is 2.5 million light years away; that means it's about 25 Milky Ways away, which is pretty easy to visualize, and surprisingly close when you think about it that way.

This image on Wikipedia illustrates that, and the scale of the larger structure of our local group.

That image also shows something closer: the Sagittarius Dwarf Ellipitical Galaxy, a tiny galaxy only about 50,000 light years from the center of the Milky Way, which actually puts it INSIDE the radius of the Milky Way, although far above the galactic plane.

Messier 54 is a pretty globular cluster inside the dwarf galaxy (the first extra-galactic cluster found, kind of cheating since the Dwarf is so close, though!):

Image
(image from NASA; larger here)

Just this summer, an intermediate-mass black hole was discovered at the center of M54! That's the first discovery (or report, if you want to be pessimistic) of such a black hole at the center of a globular cluster. I guess it won't be surprising if they eventually find that most clusters have black holes at their center, just like galaxies do (only smaller holes in the clusters).

The dwarf galaxy is being torn apart/absorbed by the much larger Milky Way; Palomar 12 is a cluster that's thought to have been pulled off into our own galaxy:

Image
(image from NASA; larger here)

But that dwarf isn't the only--or even the closest--little galaxy being swept up by the Milky Way. That first scale map I linked above doesn't show it, but even closer is the Canis Major Dwarf Galaxy, at just 42,000 light years from the center of the Milky Way--and at 25,000 light years from Earth, that means this tiny galaxy is currently about 5,000 light years closer to us than we are to the center of our own galaxy! It's thought to have about as many stars as the Sagittarius Dwarf galaxy, which is about 10,000 light years in diameter.

Canis Major wasn't discovered until 2003 because it's on the far side of the plane of the Milky Way, obscured by gas and dust. It was found by astronomers following the path of a string of stars, noticed in a large sky survey, that appears to wrap around the Milky Way three times: the Monoceros Ring: following this ring of stars, they found Canis Major at the end of it! The stars forming the ring are being pulled off of Canis Major as it revolves around (and through) the Milky Way.

There are a lot of galaxies out there. :D


Thu Nov 05, 2009 7:16 am
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Galaxy ESO 510-G13, currently warped from a collision with another galaxy:
Image
(image from NASA; larger here)

The Mice Galaxies, two colliding galaxies leaving behind long "tails" of torn-off stars:
Image
(image from NASA; larger here)

The two fuzzy yellow cores of the colliding Antennae Galaxies, further along in their collision and merging than the Mice, are getting very close together; the increased density of gas and dust in their tearing and merging discs is brightening the galaxies up with high rates of star formation:
Image
(image from NASA; larger here)


Thu Nov 05, 2009 9:24 am
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