Starship Asterisk*

neufer wrote: And what was your experience with SN 1987A

Nitpicker wrote:
Yeah, almost all deep sky objects look comparatively dull to me now, even through the eyepiece of my small 6" telescope. Once I started attaching a camera to my scope, I found I hardly ever used my eyepieces anymore, except perhaps occasionally, to show other people the view of the Moon and the bright planets. And even the Moon and the bright planets look more detailed in photographic images (after processing) than they do at the eyepiece. But still, on a clear night (even under my suburban skies) it is nice to spot the LMC and SMC unaided, and to realise that they are not just fluffy little atmospheric clouds passing a few thousand feet overhead.

Chris Peterson wrote:

Nitpicker wrote: Another other side, is that the LMC is about the size of one's outstretched fist. If you find yourself at a sufficiently southern latitude, give the LMC a power salute on a clear night and you'll see what I mean.

(To see the whole LMC reasonably well, such that the lowest part culminates above an elevation of 20 degrees, one needs to be in the southern hemisphere, most ideally at a time around the December Solstice. Book your Xmas holiday now!)

I've seen it well. It's rather boring (although the experience is improved if you have a good sense of what you're actually looking at). It just looks like a clump of the Milky Way- a faint gray patch. Our eyes simply didn't evolve to recover much information from astronomical objects. Thank goodness for cameras and other instruments!

Nitpicker wrote:

Chris Peterson wrote:

Ironwood wrote:I didn't realize the large magellanic cloud was so freaking big in the sky. I was trying to research what the farthest northern latitude it was visible from and read that it covers an area of sky that is 9 x 11 degrees. I had no idea it was that huge. I'd always pictured it as smaller than a full moon.

The other side of that observation is that most people don't realize just how tiny the full Moon is.

Another other side, is that the LMC is about the size of one's outstretched fist. If you find yourself at a sufficiently southern latitude, give the LMC a power salute on a clear night and you'll see what I mean.

(To see the whole LMC reasonably well, such that the lowest part culminates above an elevation of 20 degrees, one needs to be in the southern hemisphere, most ideally at a time around the December Solstice. Book your Xmas holiday now!)

Chris Peterson wrote:

Ironwood wrote:I didn't realize the large magellanic cloud was so freaking big in the sky. I was trying to research what the farthest northern latitude it was visible from and read that it covers an area of sky that is 9 x 11 degrees. I had no idea it was that huge. I'd always pictured it as smaller than a full moon.

The other side of that observation is that most people don't realize just how tiny the full Moon is.

Ironwood wrote:I didn't realize the large magellanic cloud was so freaking big in the sky. I was trying to research what the farthest northern latitude it was visible from and read that it covers an area of sky that is 9 x 11 degrees. I had no idea it was that huge. I'd always pictured it as smaller than a full moon.

BillT wrote:
Actually Gaia can resolve some stars in the LMC.

Gaia has just completed its' first year of normal operation and one of the things mentioned in the ESA's blog post is this:

"Gaia has delivered detailed light curves for dozens of RR Lyrae type variable stars in the LMC, and the fine details revealed in them testify to the very high quality of the data."

They also posted their first HR diagram of just 2 million stars. They are saying that they will have the first major data release after the second year of operation is completed next year. The link is http://sci.esa.int/gaia/56387-gaia-s-fi ... ervations/

BillT wrote:Actually Gaia can resolve some stars in the LMC.

neufer wrote:

Chris Peterson wrote:I'm not sure of your point. We still aren't detecting any change in the galaxy as a function of time. And the resolution of the Gaia telescopes is far too low to resolve stars in the LMC, and most are too dim. Gaia will be able to provide very little information about anything going on in the LMC.

Hubble has already measured the ~10 AU/yr relative proper motion of bright LMC stars to determine that the LMC has a rotation period of 250 million years (comparable to the rotation period of the Earth around the Milky Way). Gaia should be able to improve upon this as well as search for non rotational proper motion. (I'm assuming these are the sort of changes ta152h0 was asking about.)

Chris Peterson wrote:

neufer wrote:

https://en.wikipedia.org/wiki/Gaia_%28spacecraft%29 wrote:
<<[Gaia should be able to determine] the position, distance, and annual proper motion of 1 billion stars
with an accuracy of about 20 microarcseconds (µas) at 15 [apparent] mag, and 200 µas at 20 [apparent] mag.>>

• Hence: Gaia should be able to determine the position, distance, and annual
  proper motion of LMC stars [50,000 parsecs away] with an accuracy of about:
  [1 AU] at -3.5 absolute magnitude, & [10 AU] at 1.5 absolute magnitude.

I'm not sure of your point. We still aren't detecting any change in the galaxy as a function of time. And the resolution of the Gaia telescopes is far too low to resolve stars in the LMC, and most are too dim. Gaia will be able to provide very little information about anything going on in the LMC.

neufer wrote:

Chris Peterson wrote:

ta152h0 wrote:
any images takes at the turn of the last century of the LMC that can be compared to this image and detect changes ? Like how Mr Tombaugh found Pluto ?

100 years simply isn't long enough to detect any changes in objects of this size.

With modern high resolution imaging we might just be able to detect the proper motion of a few stars over decadal measurement scales, but that's about it.

https://en.wikipedia.org/wiki/Gaia_%28spacecraft%29 wrote:
<<[Gaia should be able to determine] the position, distance, and annual proper motion of 1 billion stars
with an accuracy of about 20 microarcseconds (µas) at 15 [apparent] mag, and 200 µas at 20 [apparent] mag.>>

• Hence: Gaia should be able to determine the position, distance, and annual
  proper motion of LMC stars [50,000 parsecs away] with an accuracy of about:
  [1 AU] at -3.5 absolute magnitude, & [10 AU] at 1.5 absolute magnitude.

Chris Peterson wrote:

ta152h0 wrote:
any images takes at the turn of the last century of the LMC that can be compared to this image and detect changes ? Like how Mr Tombaugh found Pluto ?

100 years simply isn't long enough to detect any changes in objects of this size.

With modern high resolution imaging we might just be able to detect the proper motion of a few stars over decadal measurement scales, but that's about it.

https://en.wikipedia.org/wiki/Gaia_%28spacecraft%29 wrote:
<<[Gaia should be able to determine] the position, distance, and annual proper motion of 1 billion stars
with an accuracy of about 20 microarcseconds (µas) at 15 [apparent] mag, and 200 µas at 20 [apparent] mag.>>

• Hence: Gaia should be able to determine the position, distance, and annual
  proper motion of LMC stars [50,000 parsecs away] with an accuracy of about:
  [1 AU] at -3.5 absolute magnitude, & [10 AU] at 1.5 absolute magnitude.

https://en.wikipedia.org/wiki/SN_1987A wrote:

[b][color=#0000FF]A time sequence of Hubble Space Telescope images, taken in the 15 years from 1994 to 2009, showing the collision of the expanding supernova remnant with a ring of dense material ejected by the progenitor star 20,000 years before the supernova.[/color][/b]

---

SN 1987A was a supernova in the outskirts of the Tarantula Nebula in the Large Magellanic Cloud (a nearby dwarf galaxy).

The three bright rings around SN 1987A are material from the stellar wind of the progenitor. These rings were ionized by the ultraviolet flash from the supernova explosion, and consequently began emitting in various emission lines. These rings did not "turn on" until several months after the supernova; the turn-on process can be very accurately studied through spectroscopy. The rings are large enough that their angular size can be measured accurately: the inner ring is 0.808 arcseconds in radius. Using the distance light must have traveled to light up the inner ring as the base of a right angle triangle and the angular size as seen from the Earth for the local angle, one can use basic trigonometry to calculate the distance to SN1987A, which is about 168,000 light-years. The material from the explosion is catching up with the material expelled during both its red and blue supergiant phases and heating it, so we observe ring structures about the star.

Around 2001, the expanding (>7000 km/s) supernova ejecta collided with the inner ring. This caused its heating and the generation of x-rays — the x-ray flux from the ring increased by a factor of three between 2001 and 2009. A part of the x-ray radiation, which is absorbed by the dense ejecta close to the center, is responsible for a comparable increase in the optical flux from the supernova remnant in 2001–2009. This increase of the brightness of the remnant reversed the trend observed before 2001, when the optical flux was decreasing due to the decaying of ⁴⁴Ti isotope.

A study reported in June 2015, using images from the Hubble Space Telescope and the Very Large Telescope taken between 1994 and 2014, shows that the emissions from the clumps of matter making up the rings are fading as the clumps are destroyed by the shock wave. It is predicted the ring will fade away between 2020 and 2030. As the shock wave passes the circumstellar ring it will trace the history of mass loss of the supernova's progenitor and provide useful information for discriminating among various models for the progenitor of SN 1987A.>>

GaryJ wrote:In this gorgeous image, I assume there are a lot of "foreground" stars from the Milky Way. Is there a good way to digitally "remove" them, so we can see what the LMC looks like from outside of our galaxy?

apodviewer wrote:Please tell me how we know that there was a supernovae in "modern" times in the LMC. It is 160,000 light years away. Light must have taken that long to get here from there. Hence we could not know about anything going on there more recently that 160,000 years. Do you define this as" modern" times? I really want to know the answer.

ta152h0 wrote:any images takes at the turn of the last century of the LMC that can be compared to this image and detect changes ? Like how Mr Tombaugh found Pluto ?

ta152h0 wrote:
any images takes at the turn of the last century of the LMC that can be compared to this image and detect changes ?

Ron-Astro Pharmacist wrote:

Asterhole wrote:What would our Galaxy would look like from there...? I imagine it would nearly fill the nighttime sky if view from the outskirts of the LMC.

The Milky Way is around 100,000 light-years in diameter and the Large Magellanic Cloud is 14,000 light-years across so I suspect our galaxy would look around 7 times the angular size of the LMC. I would imagine many astronomers would love to see that view. It might clear up some conjecture.

apodviewer wrote:Please tell me how we know that there was a supernovae in "modern" times in the LMC. It is 160,000 light years away. Light must have taken that long to get here from there. Hence we could not know about anything going on there more recently that 160,000 years. Do you define this as" modern" times? I really want to know the answer.

Ann wrote:That's a great picture. I love seeing the entire LMC, including the large complex seen at 10 o'clock in today's APOD, NGC 1760.

Ann

apodviewer wrote:Please tell me how we know that there was a supernovae in "modern" times in the LMC. It is 160,000 light years away. Light must have taken that long to get here from there. Hence we could not know about anything going on there more recently that 160,000 years. Do you define this as" modern" times? I really want to know the answer.