Starship Asterisk*

triastro wrote: ↑Sat Mar 28, 2020 10:18 pm I particularly liked this image because in 12 years of teaching astronomy, one thing I tried to get across to my students was that the universe was not so big as many tried to paint it, and that it was comprehensible. One way I tried to do this was to show them an image of the Andromeda galaxy. Then, I would explain that it was approximately 10X the angular size of the setting sun -- something they have all seen and can relate to. Then I tried to get them to imagine replacing the setting sun with the Andromeda galaxy. By doing so, clearly they could imagine the Andromeda galaxy 10X larger than the setting sun and then realize it was actually quite a nearby large galaxy. Then, finally, I explained that the edge of the observable universe was only 5000X farther away than the Andromeda galaxy -- which is actually not that far away in cosmic terms.

Thanks for a very nice image!

Cousin Ricky wrote: ↑Fri Mar 27, 2020 1:50 pm The collision between the Milky Way and M31 will have no consequences for any hypothetical civilization in our solar system—other than prettier night skies.

CuriousChimp wrote: ↑Thu Mar 26, 2020 2:06 pm Are we sure that our big bully of a neighbour is coming here?

CuriousChimp wrote: ↑Thu Mar 26, 2020 2:06 pm Are we certain she's part of the Milky Way Local Group, even? Might it not be that The Lady is the core galaxy of her own local group and that they are just passing by?

There are many, many fine examples, and APoD shows lots of the prettier ones, of pairs and multiples of huge star clouds whizzing by each other without being related. Might lovely Andromeda and us be one of those?

CuriousChimp wrote: ↑Thu Mar 26, 2020 2:06 pm If not, why am I so sceptical?

CuriousChimp wrote: ↑Thu Mar 26, 2020 2:06 pm Another weird thought ... five milliards of years is a strangely specific number. By an interesting coincidence it is also roughly the expected lifespan of Sol, that shiny, bright thing that keeps us all cosy and warm. With a possible galactic-sized catastrophe and the end of our Sun coming it is almost as though the cosmos is waving a sign at us; telling us to get the hades out of here before it smooshes us.

I wonder whether Man is clever enough to see the signs and to heed them?

neufer wrote: ↑Thu Mar 26, 2020 4:34 pm

johnnydeep wrote: ↑Thu Mar 26, 2020 3:12 pm

neufer wrote: ↑Thu Mar 26, 2020 12:06 pm
"I see millions of stars, Holmes," says Watson.

"And what do you conclude from that, Watson?"

Watson thinks for a moment. "Well," he says, "astronomically, it tells me that there are millions of galaxies and potentially billions of planets.

The entire quote is pretty darn funny, but the nerd in me has a problem with deducing that there are millions of galaxies from seeing millions of stars in the sky. It just doesn't follow.

• If Watson has good enough eyesight to "see millions of stars" then
  I wouldn't dare question his insight to deduce "that there are millions of galaxies."

https://www.etymonline.com/search?q=galaxy wrote:
<<galaxy (n.) late 14c., from French galaxie or directly from Late Latin galaxias "the Milky Way" as a feature in the night sky (in classical Latin via lactea or circulus lacteus), from Greek galaxias (adj.), in galaxias kyklos, literally "milky circle," from gala (genitive galaktos) "milk."

The technical astronomical sense in reference to the discrete stellar aggregate including the sun and all visible stars emerged by 1848. Figurative sense of "brilliant assembly of persons" is from 1580s. Milky Way is a translation of Latin via lactea.

Originally ours was the only one known. Astronomers began to speculate by mid-19c. that some of the spiral nebulae they could see in telescopes were actually immense and immensely distant structures the size and shape of the Milky Way.>>

neufer wrote: ↑Thu Mar 26, 2020 12:06 pm

https://www.goodreads.com/quotes/tag/sherlock-holmes wrote:

---

“Holmes and Watson are on a camping trip. In the middle of the night Holmes wakes up and gives Dr. Watson a nudge. "Watson" he says, "look up in the sky and tell me what you see."

"I see millions of stars, Holmes," says Watson.

"And what do you conclude from that, Watson?"

Watson thinks for a moment. "Well," he says, "astronomically, it tells me that there are millions of galaxies and potentially billions of planets. Astrologically, I observe that Saturn is in Leo. Horologically, I deduce that the time is approximately a quarter past three. Meterologically, I suspect that we will have a beautiful day tomorrow. Theologically, I see that God is all-powerful, and we are small and insignficant. Uh, what does it tell you, Holmes?"

"Watson, you idiot! Someone has stolen our tent!”

― Thomas Cathcart, Daniel Klein

Also, M82 & M81 have probably already had a closer encounter

Ann wrote: ↑Thu Mar 26, 2020 3:20 pm
As Chris said, practically all galaxies that are of similar resolution and moderately similar size, and are close together on the sky, show signs of interaction. A fine example is the M81/ M82/ NGC 3077 trio.

There is no doubting the interaction between these three galaxies. We have every reason to believe that there are already signs of interaction between Andromeda and the Milky Way, even though the signs are probably still subtle.

https://en.wikipedia.org/wiki/Messier_82 wrote:
<<M82 is being physically affected by its larger neighbor, the spiral M81. Ignoring any difference in their respective distances from the Earth, the centers of M81 and M82 are visually separated by about 130,000 light-years. The actual separation is 300 kly. Tidal forces caused by gravity have deformed M82, a process that started about 100 million years ago. This interaction has caused star formation to increase tenfold compared to "normal" galaxies.

M82 has undergone at least one tidal encounter with M81 resulting in a large amount of gas being funneled into the galaxy's core over the last 200 Myr. The most recent such encounter is thought to have happened around 2–5×10⁸ years ago and resulted in a concentrated starburst together with a corresponding marked peak in the cluster age distribution. This starburst ran for up to ~50 Myr at a rate of ~10 M⊙ per year. Two subsequent starbursts followed, the last (~4–6 Myr ago) of which may have formed the core clusters, both super star clusters (SSCs) and their lighter counterparts.

Stars in M82's disk seem to have been formed in a burst 500 million years ago, leaving its disk littered with hundreds of clusters with properties similar to globular clusters (but younger), and stopped 100 million years ago with no star formation taking place in this galaxy outside the central starburst and, at low levels since 1 billion years ago, on its halo. A suggestion to explain those features is that M82 was previously a low surface brightness galaxy where star formation was triggered due to interactions with its giant neighbor.>>

johnnydeep wrote: ↑Thu Mar 26, 2020 3:12 pm

neufer wrote: ↑Thu Mar 26, 2020 12:06 pm
"I see millions of stars, Holmes," says Watson.

"And what do you conclude from that, Watson?"

Watson thinks for a moment. "Well," he says, "astronomically, it tells me that there are millions of galaxies and potentially billions of planets.

The entire quote is pretty darn funny, but the nerd in me has a problem with deducing that there are millions of galaxies from seeing millions of stars in the sky. It just doesn't follow.

• If Watson has good enough eyesight to "see millions of stars" then
  I wouldn't dare question his insight to deduce "that there are millions of galaxies."

https://www.etymonline.com/search?q=galaxy wrote:

---

<<galaxy (n.) late 14c., from French galaxie or directly from Late Latin galaxias "the Milky Way" as a feature in the night sky (in classical Latin via lactea or circulus lacteus), from Greek galaxias (adj.), in galaxias kyklos, literally "milky circle," from gala (genitive galaktos) "milk."

The technical astronomical sense in reference to the discrete stellar aggregate including the sun and all visible stars emerged by 1848. Figurative sense of "brilliant assembly of persons" is from 1580s. Milky Way is a translation of Latin via lactea.

Chaucer in _House of Fame_ wrote:

• See yonder, lo, the Galaxyë
  Which men clepeth the Milky Wey,
  For hit is whyt.

Originally ours was the only one known. Astronomers began to speculate by mid-19c. that some of the spiral nebulae they could see in telescopes were actually immense and immensely distant structures the size and shape of the Milky Way.>>

CuriousChimp wrote: ↑Thu Mar 26, 2020 2:06 pm

APOD Robot wrote: ↑Thu Mar 26, 2020 4:05 am
... Don't worry, though. Just wait 5 billion years and the Andromeda Galaxy will come to you. ...

I keep seeing this assertion but I don't like it. I don't know why but I'm very dubious about it.

Are we sure that our big bully of a neighbour is coming here? Are we certain she's part of the Milky Way Local Group, even? Might it not be that The Lady is the core galaxy of her own local group and that they are just passing by?

There are many, many fine examples, and APoD shows lots of the prettier ones, of pairs and multiples of huge star clouds whizzing by each other without being related. Might lovely Andromeda and us be one of those?

If not, why am I so sceptical?

Another weird thought ... five milliards of years is a strangely specific number. By an interesting coincidence it is also roughly the expected lifespan of Sol, that shiny, bright thing that keeps us all cosy and warm. With a possible galactic-sized catastrophe and the end of our Sun coming it is almost as though the cosmos is waving a sign at us; telling us to get the hades out of here before it smooshes us.

I wonder whether Man is clever enough to see the signs and to heed them?

neufer wrote: ↑Thu Mar 26, 2020 12:06 pm
"I see millions of stars, Holmes," says Watson.

"And what do you conclude from that, Watson?"

Watson thinks for a moment. "Well," he says, "astronomically, it tells me that there are millions of galaxies and potentially billions of planets.

bystander wrote: ↑Thu Mar 26, 2020 2:36 pm

Ann wrote: ↑Thu Mar 26, 2020 5:14 am

jks wrote: ↑Thu Mar 26, 2020 4:39 am I apologize for my recent postings of apparent problems but I have another one (I think).

I usually click on the image in order to either zoom in, or to sometimes see a wider view, but for today's APOD I get the dreaded:

"Not Found

The requested URL /apod/image/2003/AndromedaStation.jpg was not found on this server."

I tried my phone (Wi-Fi off) and I get the same thing. Clicking on the image for yesterday's APOD works just fine.

I, too, got the "Not Found" message when I clicked on the APOD to enlarge it. So the problem is with the APOD itself. Or let's put it like this: There is no larger version of today's APOD currently available.

Ann

Try Andromeda%20Station.jpg

neufer wrote: ↑Thu Mar 26, 2020 2:57 pm

Chris Peterson wrote: ↑Thu Mar 26, 2020 2:30 pm

CuriousChimp wrote: ↑Thu Mar 26, 2020 2:06 pm

I keep seeing this assertion but I don't like it. I don't know why but I'm very dubious about it.

Are we sure that our big bully of a neighbour is coming here? Are we certain she's part of the Milky Way Local Group, even? Might it not be that The Lady is the core galaxy of her own local group and that they are just passing by?

Yes, we are sure that the two galaxies are on a collision course, and we're sure that both Andromeda and the Milky Way are part of the same cluster. We can measure the mass of Andromeda with reasonable accuracy, and we can measure its velocity with reasonable accuracy. Enough to determine that our galaxies are gravitationally bound in mutual closed orbits. In all such cases, the end result is merger.

https://en.wikipedia.org/wiki/Andromeda%E2%80%93Milky_Way_collision#Certainty wrote:
<<The Andromeda Galaxy is approaching the Milky Way at about 110 kilometres per second as indicated by blueshift. However, the lateral speed (measured as proper motion) is very difficult to measure with a precision to draw reasonable conclusions: a lateral speed of only 7.7 km/s would mean that the Andromeda Galaxy is moving toward a point 177,800 light-years to the side of the Milky Way ((7.7 km/s) / (110 km/s) × (2,540,000 ly)), and such a speed over an eight-year timeframe amounts to only 1/3,000th of a Hubble Space Telescope pixel (Hubble's resolution≈0.05 arcsec: (7.7 km/s)/(300,000 km/s)×(8 y)/(2,540,000 ly)×180°/π×3600 = 0.000017 arcsec). Until 2012, it was not known whether the possible collision was definitely going to happen or not. In 2012, researchers concluded that the collision is sure using Hubble to track the motion of stars in Andromeda between 2002 and 2010 with sub-pixel accuracy. Andromeda's tangential or sideways velocity with respect to the Milky Way was found to be much smaller than the speed of approach and therefore it is expected that it will directly collide with the Milky Way in around four and a half billion years.

The studies also suggest that M33, the Triangulum Galaxy—the third-largest and third-brightest galaxy of the Local Group—will participate in the collision event, too. Its most likely fate is to end up orbiting the merger remnant of the Milky Way and Andromeda galaxies and finally to merge with it in an even more distant future. However, a collision with the Milky Way, before it collides with the Andromeda Galaxy, or an ejection from the Local Group cannot be ruled out.>>

Chris Peterson wrote: ↑Thu Mar 26, 2020 2:30 pm

CuriousChimp wrote: ↑Thu Mar 26, 2020 2:06 pm

APOD Robot wrote: ↑Thu Mar 26, 2020 4:05 am
... Don't worry, though. Just wait 5 billion years and the Andromeda Galaxy will come to you. ...

I keep seeing this assertion but I don't like it. I don't know why but I'm very dubious about it.

Are we sure that our big bully of a neighbour is coming here? Are we certain she's part of the Milky Way Local Group, even? Might it not be that The Lady is the core galaxy of her own local group and that they are just passing by?

Yes, we are sure that the two galaxies are on a collision course, and we're sure that both Andromeda and the Milky Way are part of the same cluster. We can measure the mass of Andromeda with reasonable accuracy, and we can measure its velocity with reasonable accuracy. Enough to determine that our galaxies are gravitationally bound in mutual closed orbits. In all such cases, the end result is merger.

https://en.wikipedia.org/wiki/Andromeda%E2%80%93Milky_Way_collision#Certainty wrote:
<<The Andromeda Galaxy is approaching the Milky Way at about 110 kilometres per second as indicated by blueshift. However, the lateral speed (measured as proper motion) is very difficult to measure with a precision to draw reasonable conclusions: a lateral speed of only 7.7 km/s would mean that the Andromeda Galaxy is moving toward a point 177,800 light-years to the side of the Milky Way ((7.7 km/s) / (110 km/s) × (2,540,000 ly)), and such a speed over an eight-year timeframe amounts to only 1/3,000th of a Hubble Space Telescope pixel (Hubble's resolution≈0.05 arcsec: (7.7 km/s)/(300,000 km/s)×(8 y)/(2,540,000 ly)×180°/π×3600 = 0.000017 arcsec). Until 2012, it was not known whether the possible collision was definitely going to happen or not. In 2012, researchers concluded that the collision is sure using Hubble to track the motion of stars in Andromeda between 2002 and 2010 with sub-pixel accuracy. Andromeda's tangential or sideways velocity with respect to the Milky Way was found to be much smaller than the speed of approach and therefore it is expected that it will directly collide with the Milky Way in around four and a half billion years.

The studies also suggest that M33, the Triangulum Galaxy—the third-largest and third-brightest galaxy of the Local Group—will participate in the collision event, too. Its most likely fate is to end up orbiting the merger remnant of the Milky Way and Andromeda galaxies and finally to merge with it in an even more distant future. However, a collision with the Milky Way, before it collides with the Andromeda Galaxy, or an ejection from the Local Group cannot be ruled out.>>

Ann wrote: ↑Thu Mar 26, 2020 5:14 am

jks wrote: ↑Thu Mar 26, 2020 4:39 am I apologize for my recent postings of apparent problems but I have another one (I think).

I usually click on the image in order to either zoom in, or to sometimes see a wider view, but for today's APOD I get the dreaded:

"Not Found

The requested URL /apod/image/2003/AndromedaStation.jpg was not found on this server."

I tried my phone (Wi-Fi off) and I get the same thing. Clicking on the image for yesterday's APOD works just fine.

I, too, got the "Not Found" message when I clicked on the APOD to enlarge it. So the problem is with the APOD itself. Or let's put it like this: There is no larger version of today's APOD currently available.

Ann

CuriousChimp wrote: ↑Thu Mar 26, 2020 2:06 pm

APOD Robot wrote: ↑Thu Mar 26, 2020 4:05 am
... Don't worry, though. Just wait 5 billion years and the Andromeda Galaxy will come to you. ...

I keep seeing this assertion but I don't like it. I don't know why but I'm very dubious about it.

Are we sure that our big bully of a neighbour is coming here? Are we certain she's part of the Milky Way Local Group, even? Might it not be that The Lady is the core galaxy of her own local group and that they are just passing by?

There are many, many fine examples, and APoD shows lots of the prettier ones, of pairs and multiples of huge star clouds whizzing by each other without being related.

Bill Bruehl wrote: ↑Thu Mar 26, 2020 1:16 pmI have two questions when I look at Andromeda––as well as all galaxies–– what is the depth of the galaxy in light-years and does the energy created by the black hole in the center exit our cosmos?

Cousin Ricky wrote: ↑Thu Mar 26, 2020 1:33 pm

APOD Robot wrote: ↑Thu Mar 26, 2020 4:05 am But at 2.5 million light-years from Earth the big beautiful spiral galaxy really is a little out of reach as a destination. Don't worry, though. Just wait 5 billion years and the Andromeda Galaxy will come to you.

Nighttime Sky View of Future Galaxy Merger: 7 Billion Years

From which planet? Won’t the Sun have swallowed up the Earth by then?

APOD Robot wrote: ↑Thu Mar 26, 2020 4:05 am
... Don't worry, though. Just wait 5 billion years and the Andromeda Galaxy will come to you. ...

Ann wrote: ↑Thu Mar 26, 2020 5:14 am

jks wrote: ↑Thu Mar 26, 2020 4:39 am I apologize for my recent postings of apparent problems but I have another one (I think).

I usually click on the image in order to either zoom in, or to sometimes see a wider view, but for today's APOD I get the dreaded:

"Not Found

The requested URL /apod/image/2003/AndromedaStation.jpg was not found on this server."

I tried my phone (Wi-Fi off) and I get the same thing. Clicking on the image for yesterday's APOD works just fine.

I, too, got the "Not Found" message when I clicked on the APOD to enlarge it. So the problem is with the APOD itself. Or let's put it like this: There is no larger version of today's APOD currently available.

Ann

APOD Robot wrote: ↑Thu Mar 26, 2020 4:05 am But at 2.5 million light-years from Earth the big beautiful spiral galaxy really is a little out of reach as a destination. Don't worry, though. Just wait 5 billion years and the Andromeda Galaxy will come to you.