Explanation: In this Hubble Space Telescope image the bright, spiky stars lie in the foreground toward the heroic northern constellation Perseus and well within our own Milky Way galaxy. In sharp focus beyond is UGC 2885, a giant spiral galaxy about 232 million light-years distant. Some 800,000 light-years across compared to the Milky Way's diameter of 100,000 light-years or so, it has around 1 trillion stars. That's about 10 times as many stars as the Milky Way. Part of a current investigation to understand how galaxies can grow to such enormous sizes, UGC 2885 was also part of astronomer Vera Rubin's pioneering study of the rotation of spiral galaxies. Her work was the first to convincingly demonstrate the dominating presence of dark matter in our universe.
Wikipedia disagrees on the size of UGC 2885 being 800kly. It also claims that the largest known spiral galaxy is 'only' 650kly.
Re: APOD: Rubin's Galaxy (2020 Jan 25)
Posted: Sat Jan 25, 2020 10:17 am
by Ann
Apart from noting that UGC 2885 is a stunningly elegant galaxy, I highly recommend this page from NASA/ESA/Hubble Space Telescope.
Space Telescope wrote about UGC 2885:
Despite its gargantuan size, researchers are calling it a “gentle giant” because it looks as if it has been sitting quietly over billions of years, possibly sipping hydrogen from the filamentary structure of intergalactic space. This is fuelling modest ongoing star birth at a rate half that of our Milky Way. In fact, its supermassive central black hole is also a sleeping giant; because the galaxy does not appear to be feeding on much smaller satellite galaxies, it is starved of infalling gas.
Fascinating, isn't it? UGC 2885 is a "gentle giant" sipping hydrogen from filamentary structure of intergalactic space like a nice lady sipping tea.
The galaxy even has a black hole in its midst that is basically not doing anything because it is deprived of gas.
Spacetelescope wrote:
Researchers are still seeking to understand what led to the galaxy’s monstrous size. “It’s as big as you can make a disk galaxy without hitting anything else in space,” added Holwerda.
One clue is that the galaxy is fairly isolated in space and doesn’t have any nearby galaxies to crash into and disrupt the shape of its disc.
Meditating Astronaut Space Yoga. Digital artwork by Jonathan Golding.
Wow. UGC 2885 is isolated in space and has grown and grown and grown in size without hitting anything. I wanted to find a picture of a huge fat Buddha floating all alone in space, but all I could find was this meditating astronaut, just sitting there in space. You will have to imagine that he is capable of growing and growing and growing until he hits something out there.
And I have to wonder: Is this peaceful galaxy a haven for extraterrestrial life?
Ann
Re: APOD: Rubin's Galaxy (2020 Jan 25)
Posted: Sat Jan 25, 2020 12:08 pm
by orin stepanek
RubinsGalaxy_hst1024.jpg (22.5 KiB) Viewed 11204 times
Wow! You can marvel at the size of this galaxy;
but I also marvel at its pure beauty!
I'll have to get on my desktop... this window won't stay enlarged.FUN!
Rubins Galaxy
Posted: Sat Jan 25, 2020 2:42 pm
by BaldEagle
Today's APOD is Rubins Galaxy. At the center, it appears to whirlpool down toward its singularity. If seen from the underside would it appear to whirlpool down as well?
Re: APOD: Rubin's Galaxy (2020 Jan 25)
Posted: Sat Jan 25, 2020 2:48 pm
by neufer
rj rl wrote: ↑Sat Jan 25, 2020 9:59 am
Wikipedia disagrees on the size of UGC 2885 being 800kly. It also claims that the largest known spiral galaxy is 'only' 650kly.
<<To kickstart the 30th anniversary year of the NASA/ESA Hubble Space Telescope, Hubble has imaged a majestic spiral galaxy. Galaxy UGC 2885 may be the largest known in the local universe. It is 2.5 times wider than our Milky Way and contains 10 times as many stars. The galaxy is also called “Rubin’s galaxy”, after astronomer Vera Rubin (1928–2016), by Benne Holwerda of the University of Louisville, Kentucky, who observed the galaxy with the Hubble Space Telescope. “My research was in large part inspired by Vera Rubin’s work in 1980 on the size of this galaxy,” said Holwerda>>
<<The Reuben sandwich is an American grilled sandwich composed of corned beef, Swiss cheese, sauerkraut, and Russian dressing, grilled between slices of rye bread. It is associated with kosher-style delicatessens, but it is not kosher, because it contains both meat and cheese. One origin story holds that Reuben Kulakofsky (his first name sometimes spelled Reubin; his last name sometimes shortened to Kay), a Jewish Lithuanian-born grocer residing in Omaha, Nebraska, was the inventor, perhaps as part of a group effort by members of Kulakofsky's weekly poker game held in the Blackstone Hotel from around 1920 through 1935. The participants, who nicknamed themselves "the committee", included the hotel's owner, Charles Schimmel. The sandwich first gained local fame when Schimmel put it on the Blackstone's lunch menu, and its fame spread when a former employee of the hotel won a national contest with the recipe. Mention is made of this sandwich in a scene within the movie Quiz Show (film), where Richard N. Goodwin (known as Dick) orders and eats one in a restaurant with Charles van Doren, and they discuss the sandwich's origins.>>
Re: APOD: Rubin's Galaxy (2020 Jan 25)
Posted: Sat Jan 25, 2020 2:56 pm
by Chris Peterson
rj rl wrote: ↑Sat Jan 25, 2020 9:59 am
Wikipedia disagrees on the size of UGC 2885 being 800kly. It also claims that the largest known spiral galaxy is 'only' 650kly.
I think that things got confused across a chain of press releases. With an apparent size of 3.9 arcminutes and a distance of 232 million ly, the diameter works out to 286,000 ly, and I found a couple of direct references to the original report that suggest the size is around 250,000 ly, and also references to it being about 2.5 times the size of the Milky Way. I suspect the "eight times larger" got introduced when somebody confused the mass with the diameter.
Re: Rubins Galaxy
Posted: Sat Jan 25, 2020 3:09 pm
by Chris Peterson
BaldEagle wrote: ↑Sat Jan 25, 2020 2:42 pm
Today's APOD is Rubins Galaxy. At the center, it appears to whirlpool down toward its singularity. If seen from the underside would it appear to whirlpool down as well?
The whirlpool effect is an illusion. Nothing is moving inwards- everything is in fairly stable, near circular orbits, regardless of distance from the center. The appearance of thin and thick bands, or high and low bands, is also an illusion. This is a flat disc with a bulging center. The galaxy would look pretty much the same viewed from the other side, except for the direction the arms point.
BaldEagle wrote: ↑Sat Jan 25, 2020 2:42 pm
Today's APOD is Rubins Galaxy. At the center, it appears to whirlpool down toward its singularity. If seen from the underside would it appear to whirlpool down as well?
The whirlpool effect is an illusion. Nothing is moving inwards- everything is in fairly stable, near circular orbits, regardless of distance from the center. The appearance of thin and thick bands, or high and low bands, is also an illusion. This is a flat disc with a bulging center. The galaxy would look pretty much the same viewed from the other side, except for the direction the arms point.
https://en.wikipedia.org/wiki/Freeze-dried_ice_cream wrote:
<<Freeze-dried ice cream was developed by Whirlpool Corporation under contract to NASA for the Apollo missions so that foods could be sent on long-duration spaceflights, as to the Moon, and to reduce the weight of the water and oxygen normally found in food. Despite the common use of images of space walking astronauts in shuttle era space suits on packaging, freeze dried ice cream was not included on any Apollo, Skylab, Space Shuttle, or International Space Station missions. According to one NASA food scientist, although freeze-dried ice cream was developed on request, "it wasn't that popular." During the 1970s, astronauts ate regular ice cream on the Skylab space station and regular ice cream has also been eaten on the International Space Station.>>
Re: APOD: Rubin's Galaxy (2020 Jan 25)
Posted: Sat Jan 25, 2020 4:29 pm
by Fred the Cat
Ramifications from Vera Rubin's work has baffled scientists for some time and has now set them into free fall.
I very much enjoyed reading about Vera Rubin.Thanks for the link.It's just not fair that we just cannot flit right over and pay this extraordinary galaxy a visit....
Slightly becroggled at seeing UGC 2885 so tiny in that California Nebula image... and in the APOD there are just as tiny galaxies in the far distance. Douglas Adams was right — space is big. Really big.
Re: APOD: Rubin's Galaxy (2020 Jan 25)
Posted: Sun Jan 26, 2020 3:25 am
by ta152h0
Holly Cow! Makes me an insignificant creature, doesn't it?
Re: APOD: Rubin's Galaxy (2020 Jan 25)
Posted: Sun Jan 26, 2020 4:24 am
by Ann
sillyworm 2 wrote: ↑Sat Jan 25, 2020 6:17 pm
Thanks starsurfer! In the top pic..what is the name of the galaxy at 8 o'clock?
Well, there is a galaxy at about 8 o'clock in the ESA/Digitized Sky Survey 2/Davide De Martin picture. The galaxy is very tiny and faint. I could find something through my software at about that position, and if I'm right, the galaxy is called UGC 2920. According to my software, it is a 15th magnitude object, so it is faint indeed.
The only picture I could find of it, apart from its tiny mark on the ESA/Digitized Sky Survey 2/Davide De Martin picture, is this one.
Thanks starsurfer! In the top pic..what is the name of the galaxy at 8 o'clock?
Well, there is a galaxy at about 8 o'clock in the ESA/Digitized Sky Survey 2/Davide De Martin picture. The galaxy is very tiny and faint. I could find something through my software at about that position, and if I'm right, the galaxy is called UGC 2920. According to my software, it is a 15th magnitude object, so it is faint indeed. The only picture I could find of it, apart from its tiny mark on the ESA/ Digitized Sky Survey 2/Davide De Martin picture, is this one.
"A couple of hours ago (~8 o'clock) a galaxy far, far away...."
Thanks starsurfer! In the top pic..what is the name of the galaxy at 8 o'clock?
Well, there is a galaxy at about 8 o'clock in the ESA/Digitized Sky Survey 2/Davide De Martin picture. The galaxy is very tiny and faint. I could find something through my software at about that position, and if I'm right, the galaxy is called UGC 2920. According to my software, it is a 15th magnitude object, so it is faint indeed. The only picture I could find of it, apart from its tiny mark on the ESA/ Digitized Sky Survey 2/Davide De Martin picture, is this one.
"A couple of hours ago (~8 o'clock) a galaxy far, far away...."
Ann
Re: APOD: Rubin's Galaxy (2020 Jan 25)
Posted: Tue Jan 28, 2020 12:27 am
by hollandinseattle
Has anybody done the math on this? If the the galaxy is 800,000 light years across, its circumference would be a staggering 502 TRILLION light years. Is this right or am I not carrying the one?
Re: APOD: Rubin's Galaxy (2020 Jan 25)
Posted: Tue Jan 28, 2020 12:28 am
by Guest
hollandinseattle wrote: ↑Tue Jan 28, 2020 12:27 am
Has anybody done the math on this? If the the galaxy is 800,000 light years across, its circumference would be a staggering 502 TRILLION light years. Is this right or am I not carrying the one?
hollandinseattle wrote: ↑Tue Jan 28, 2020 12:27 am
Has anybody done the math on this? If the the galaxy is 800,000 light years across, its circumference would be a staggering 502 TRILLION light years. Is this right or am I not carrying the one?
C = r(squared) x pi
C = πD. If it is 800,000 ly across (which I'm doubtful is accurate) its circumference is about 2.4 million ly. The formula you give is for area (although the meaning of area is a bit ambiguous for something which is shaped like a combination of a spheroid and a disc).
And that area would be 502 billion square ly, not trillion. (1 billion = 109.)
hollandinseattle wrote: ↑Tue Jan 28, 2020 12:27 am
Has anybody done the math on this? If the the galaxy is 800,000 light years across, its circumference would be a staggering 502 TRILLION light years. Is this right or am I not carrying the one?
C = r(squared) x pi
C = πD. If it is 800,000 ly across (which I'm doubtful is accurate) its circumference is about 2.4 million ly. The formula you give is for area (although the meaning of area is a bit ambiguous for something which is shaped like a combination of a spheroid and a disc).
And that area would be 502 billion square ly, not trillion. (1 billion = 109.)
Visible disk (220,000 ly) of Andromeda Galaxy, vs halo (2 million ly).
Credits: NASA/STScI. Full size here.
As Chris said, it seems improbable that the radius of UGC 2885 is 800,000 light-years across. But its true radius does not appear to be well known. NASA/ESA claimed that it is 2.5 times wider than the Milky Way (which would make it perhaps some 250,000 light-years across), whereas Wikipedia wrote that it is 463,000 light-years across.
But UGC 2885 might actually be at least 800,000 light-years across, if we take its halo into account. Being an isolated galaxy in space, it is sure to have a halo. Our neighbour Andromeda, which is not isolated in space, has a huge halo. See the picture.
On a different note, different sources disagree on how wide the visible disk of Andromeda is. According to Wikipedia, its diameter is 220,000 light-years, but according to NASA.gov, its halo is just 6 times wider than its visible disk, even though the illustration at right suggests that the halo is 2 million light-years across.
In any case, if we include the halo of UGC 2885 its diameter might well be 800,000 light-years.
Rubin's Galaxy
