APOD: Celestial Fireworks: Into Star 2... (2017 Jul 04)

APOD Robot · Post by **APOD Robot** » Tue Jul 04, 2017 4:05 am

[img]https://apod.nasa.gov/apod/calendar/S_170704.jpg[/img] Celestial Fireworks: Into Star Cluster Westerlund 2

Explanation: What if you could go right into a cluster where stars are forming? A one-minute, time-lapse, video visualization of just this has been made with 3D computer modeling of the region surrounding the star cluster Westerlund 2, based on images from the Hubble Space Telescope in visible and infrared light. Westerlund 2 spans about 10 light years across and lies about 20,000 light years distant toward the constellation of the Ship's Keel (Carina). As the illustrative animation begins, the greater Gum 29 nebula fills the screen, with the young cluster of bright stars visible in the center. Stars zip past you as you approach the cluster. Soon your imaginary ship pivots and you pass over light-year long pillars of interstellar gas and dust. Strong winds and radiation from massive young stars destroy all but the densest nearby dust clumps, leaving these pillars in their shadows -- many pointing back toward the cluster center. Last, you pass into the top of the star cluster and survey hundreds of the most massive stars known.

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LMMT · Post by **LMMT** » Tue Jul 04, 2017 6:12 am

First time in my life I travel at warp 6 speed!! Congratulations for the video!

Ann · Post by **Ann** » Tue Jul 04, 2017 7:01 am

Westerlund 2 is an amazing cluster, and I'm glad to see it as an APOD. And it's a fun video!

: Click to view full size image

Westerlund 2 inside nebula RCW 49.
Photo: Spitzer Space Telescope.

But I doubt that the video is of much scientific value. I think we would have to know the relative distances to the individual objects quite well in order to make a video like this one realistic. According to this arXiv paper, the distance to Westerlund 2 is 2.85±0.43 kpc, suggesting that the uncertainty of the distance to the cluster itself is on the order of at least 430 light-years. That is more than the size of the surrounding nebula RCW 49, which is about 350 light-years across. Think how hard it would be to know the distances to the individual stars or parts of the nebula!

But the video is fine if we just think of it as a fun romp!

Ann

ta152h0 · Post by **ta152h0** » Tue Jul 04, 2017 8:03 am

find a dark place, lower the tailgate and have an ice cold one courtesy of the scientists at APOD. We live near an indian reservation and someone just blew a big kaboom at altitude.Native americans sure know how to celebrate correctly.

Devil Particle · Post by **Devil Particle** » Tue Jul 04, 2017 10:29 am

So in this video, we are whizzing by stars which are most likely lightyears apart. This means we're traveling at super relativistic speeds. As such, wouldn't the field of view be a little different than the artist's interpretation?

orin stepanek · Post by **orin stepanek** » Tue Jul 04, 2017 11:22 am

For today's APOD

heehaw · Post by **heehaw** » Tue Jul 04, 2017 11:29 am

I wonder how hard it would be to get rid of the four spikes on each star?

DanielP · Post by **DanielP** » Tue Jul 04, 2017 12:14 pm

I find the rendering the best I have already seen for that kind of simulation. However the star spikes disturb the rendering and could be removed easily. I don't mind about travelling faster than light and neglecting relativistic effects, as the purpose of this simulation is more to show the 3D structure of the cluster and surrounding gas than showing an interstellar trip

RedFishBlueFish · Post by **RedFishBlueFish** » Tue Jul 04, 2017 12:41 pm

Gives a sense of flying through the flat photographs one has so often seen. Nice.

Was wondering what the equivalent lightspeed would be, but Ann explains why it cannot even be estimated and thus that it is best to simply enjoy this imaginative production.

neufer · Post by **neufer** » Tue Jul 04, 2017 2:40 pm

DanielP wrote:
I find the rendering the best I have already seen for that kind of simulation. However the star spikes disturb the rendering and could be removed easily. I don't mind about traveling faster than light and neglecting relativistic effects, as the purpose of this simulation is more to show the 3D structure of the cluster and surrounding gas than showing an interstellar trip

We are neglecting the strong relativistic optical effects
but we are not traveling faster than light.

The (1 minute => 20,000 years) time dilation (Lorentz) factor of ~10¹⁰
requires a speed of (1.0 - 0.5x10^-20) times the speed of light.

(Alternatively, the travel distance has been reduced to just 1 light minute thanks to Fitzgerald contraction.)

https://en.wikipedia.org/wiki/Oh-My-God_particle wrote:
<<The Oh-My-God particle was an ultra-high-energy cosmic ray detected on the evening of 15 October 1991 over Dugway Proving Ground, Utah, by the University of Utah's Fly's Eye Cosmic Ray Detector. Its observation was a shock to astrophysicists (hence the name), who estimated its energy to be approximately 3×10²⁰ eV or 3×10⁸ TeV. This is 20,000,000 times more energetic than the highest energy measured in electromagnetic radiation emitted by an extragalactic object and 10²⁰ times the photon energy of visible light. Therefore, the particle was an atomic nucleus with a kinetic energy of 48 joules, equivalent to a 142 g (5 oz) baseball travelling at about 26 m/s (58 mph). This particle had so much kinetic energy it was travelling at ~ 99.999999999999999999999510% of the speed of light. As a result, its Lorentz factor was ~ 3.2×10¹¹.

Since the first observation, at least fifteen similar events have been recorded, confirming the phenomenon. These ultra-high-energy cosmic ray particles are very rare; the energy of most cosmic ray particles is between 10 MeV and 10 GeV. More recent studies using the Telescope Array have suggested a source for the particles within a 20-degree "warm spot" in the direction of the constellation Ursa Major.>>

Tszabeau · Post by **Tszabeau** » Tue Jul 04, 2017 2:48 pm

I love this animation and find it very enjoyable however, in reality, would not the nebula get ever fainter the nearer to it an observer got?

Chris Peterson · Post by **Chris Peterson** » Tue Jul 04, 2017 3:08 pm

Tszabeau wrote:I love this animation and find it very enjoyable however, in reality, would not the nebula get ever fainter the nearer to it an observer got?

No, it would stay the same. As it gets closer, each point increases in intensity according to the inverse square law, and each region decreases in intensity by the same amount as it's spread out over a larger area. The net result is that the surface brightness is unchanged.

Cousin Ricky · Post by **Cousin Ricky** » Tue Jul 04, 2017 6:53 pm

Ann wrote:But I doubt that the video is of much scientific value. I think we would have to know the relative distances to the individual objects quite well in order to make a video like this one realistic. According to this arXiv paper, the distance to Westerlund 2 is 2.85±0.43 kpc, suggesting that the uncertainty of the distance to the cluster itself is on the order of at least 430 light-years. That is more than the size of the surrounding nebula RCW 49, which is about 350 light-years across. Think how hard it would be to know the distances to the individual stars or parts of the nebula!

I was thinking exactly the same thing. I haven't found the method to the madness among the links. My thought is that it may be possible to plug the cluster stars' radial velocities into a gravitational simulation, and estimate the relative distances that way.

±0.43 kpc works out to about ±1400 light years, quite a bit of uncertainty indeed!

Ann wrote:But the video is fine if we just think of it as a fun romp!

Indeed!

Boomer12k · Post by **Boomer12k** » Tue Jul 04, 2017 11:30 pm

Happy Fourth of July from Earth, Universe!!!!

:---[===] *

rwj · Post by **rwj** » Wed Jul 05, 2017 1:13 am

Would the speed of this observer indeed be six times the speed of light?

neufer · Post by **neufer** » Wed Jul 05, 2017 2:29 am

rwj wrote:
Would the speed of this observer indeed be six times the speed of light?

http://asterisk.apod.com/viewtopic.php?f=9&t=37355

Starship Asterisk*

APOD: Celestial Fireworks: Into Star 2... (2017 Jul 04)

APOD: Celestial Fireworks: Into Star 2... (2017 Jul 04)

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