APOD: NICER at Night (2019 Jun 01)

Comments and questions about the APOD on the main view screen.
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APOD: NICER at Night (2019 Jun 01)

Post by APOD Robot » Sat Jun 01, 2019 4:06 am

Image NICER at Night

Explanation: A payload on board the International Space Station, the Neutron star Interior Composition Explorer (NICER) twists and turns to track cosmic sources of X-rays as the station orbits planet Earth every 93 minutes. During orbit nighttime, its X-ray detectors remain on. So as NICER slews from target to target bright arcs and loops are traced across this all-sky map made from 22 months of NICER data. The arcs tend to converge on prominent bright spots, pulsars in the X-ray sky that NICER regularly targets and monitors. The pulsars are spinning neutron stars that emit clock-like pulses of X-rays. Their timing is so precise it can be used for navigation, determining spacecraft speed and position. This NICER X-ray, all-sky, map is composed in coordinates with the celestial equator horizontally across the center.

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Re: APOD: NICER at Night (2019 Jun 01)

Post by shaileshs » Sat Jun 01, 2019 4:38 am

I wonder - How long does it take for ISS to orbit (complete 1 pass) across earth ? I thought it'd be 90min, today's APOD says 93min, but many other websites (including wikipedia, cool cosmos etc.) say it's 92min. In the day and age of precision in measuring time (x ray clock pulses from pulsars helping us) and sync'ing time across instruments/devices/sites on earth, I can't imagine such discrepancy or rounding/truncating type scenario. I'd imagine either everyone will say 92min or 93min unless there really are times when it varies for specific reason. Where am I thinking wrong ? I appreciate (in advance) everyone's help with answers and clarifications.

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Re: APOD: NICER at Night (2019 Jun 01)

Post by BDanielMayfield » Sat Jun 01, 2019 5:24 am

shaileshs wrote:
Sat Jun 01, 2019 4:38 am
I wonder - How long does it take for ISS to orbit (complete 1 pass) across earth ? I thought it'd be 90min, today's APOD says 93min, but many other websites (including wikipedia, cool cosmos etc.) say it's 92min. In the day and age of precision in measuring time (x ray clock pulses from pulsars helping us) and sync'ing time across instruments/devices/sites on earth, I can't imagine such discrepancy or rounding/truncating type scenario. I'd imagine either everyone will say 92min or 93min unless there really are times when it varies for specific reason. Where am I thinking wrong ? I appreciate (in advance) everyone's help with answers and clarifications.
The ISS is in a low Earth orbit, and the lower the orbit, the larger the gravitational pull from Earth and so the faster it must move to maintain itself in a stable orbit. But all objects in low Earth orbit experience slight drag from encountering particles in Earth's tenuous outer atmosphere. This causes them to gradually lose altitude. A lower height means both a faster speed and a shorter orbital path around the Earth. Thus the period of this craft is not of an exactly fixed duration.
The ISS maintains an orbit with an average altitude of 400 kilometres (250 mi) by means of reboost manoeuvres using the engines of the Zvezda module or visiting spacecraft.[17] It circles the Earth in roughly 92 minutes and completes 15.5 orbits per day.
P.S. 24 hrs x 60 min/hr = 1440 min/day. 1440 min / 15.5 orbits = 92.9 min / orbit, or approx 93 minutes.
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Re: APOD: NICER at Night (2019 Jun 01)

Post by Ann » Sat Jun 01, 2019 6:59 am

Interesting. The bright sources in this picture look like magnets in the sky, surrounded by funny-looking field lines. Well, I guess that many of them are magnets, so to speak, such as highly magnetized pulsars or maybe magnetars.

Some of the "field lines" are funny-looking indeed. Several of them are short, and some are jiggly. Some of them must be caused by energetic cosmic rays, right?

I'll give you a dose of pareidolia for free. There is a white blob at about 10 o'clock, which is not surrounded by "field lines". A short "quarter circle line" seems to point straight at this blob. And look, the blob seems to have eyes and a mouth. Not only that, but the blob seems to be puking, spitting out some orange goo! He is ever so slightly reminiscent of this guy.

I understand that this is an all-sky map. That must mean that most of the sources in the picture are located beyond the Milky Way. But there is one bright source at far right, which might be located in the Milky Way, if the band of the Milky Way cuts this picture horizontally. Could this source by any chance be the Vela Pulsar, the Crab pulsar, or Geminga?

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Re: APOD: NICER at Night (2019 Jun 01)

Post by AVAO » Sat Jun 01, 2019 8:52 am

Ann wrote:
Sat Jun 01, 2019 6:59 am
Interesting. The bright sources in this picture look like magnets in the sky, surrounded by funny-looking field lines. Well, I guess that many of them are magnets, so to speak, such as highly magnetized pulsars or maybe magnetars.

Some of the "field lines" are funny-looking indeed. Several of them are short, and some are jiggly. Some of them must be caused by energetic cosmic rays, right?

I'll give you a dose of pareidolia for free. There is a white blob at about 10 o'clock, which is not surrounded by "field lines". A short "quarter circle line" seems to point straight at this blob. And look, the blob seems to have eyes and a mouth. Not only that, but the blob seems to be puking, spitting out some orange goo! He is ever so slightly reminiscent of this guy.

I understand that this is an all-sky map. That must mean that most of the sources in the picture are located beyond the Milky Way. But there is one bright source at far right, which might be located in the Milky Way, if the band of the Milky Way cuts this picture horizontally. Could this source by any chance be the Vela Pulsar, the Crab pulsar, or Geminga?

Ann
If you go to www.nasa.gov/feature/goddard/2019/nicer ... -x-ray-sky there is an annotated map.
The blob is the cygnus loop :D
..and I think the bright source at far right is called millisecond pulsar PSR J0030+0451.

«PSR J0030+0451 was independently discovered by the Arecibo Drift Scan Search (Somer 2000) and the Bologna sub-millisecond pulsar survey (D'Amico 2000). It was the first millisecond pulsar (MSP) discovered with the Northern Cross radiotelescope... Follow-up observations performed at Parkes with the 21 cm multibeam receiver confirmed the pulse period P ca. 4:865 ms ... and showed the pulsar is not in a binary system.» L. Nicastro et. al. (2001)

But whether this is part of our Milky Way galaxy I'm not sure.

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Re: APOD: NICER at Night (2019 Jun 01)

Post by Ann » Sat Jun 01, 2019 9:10 am

Thanks!!! I'll be asking for your help again!

Oh! That sure was alternative view of the Cygnus Loop, whose visual appearance I'm really tired of. Who knew that it would look so good and personable in X-rays?

Well, the Vela pulsar is there in the APOD and looking pretty spry and bright, I must say. But it is not in the spot where I thought it would be. And the Crab Nebula is barely visible.

Thanks again!

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Re: APOD: NICER at Night (2019 Jun 01)

Post by bystander » Sat Jun 01, 2019 1:00 pm

Know the quiet place within your heart and touch the rainbow of possibility; be
alive to the gentle breeze of communication, and please stop being such a jerk.
— Garrison Keillor

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Re: APOD: NICER at Night (2019 Jun 01)

Post by orin stepanek » Sat Jun 01, 2019 3:11 pm

Natural navigation assistance? :shock:
Orin

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Re: APOD: NICER at Night (2019 Jun 01)

Post by Ann » Sat Jun 01, 2019 7:31 pm

The Cygnus Loop (The Veil Nebula) in optical light.
Photo: Scott Rosen.
The Veil Nebula in various wavelengths, among them X-rays.
Source: http://inspirehep.net/record/1486332/plots




















See how different the Veil Nebula looks in X-rays!

But do note the profile of a man with a toothy grin in the left part of the Veil Nebula in the optical picture. You can just barely make up this grinning man in the left part of the multi-wavelength picture at right.

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Re: APOD: NICER at Night (2019 Jun 01)

Post by Chris Peterson » Sun Jun 02, 2019 1:28 pm

orin stepanek wrote:
Sat Jun 01, 2019 3:11 pm
Natural navigation assistance? :shock:
A common feature of a lot of good, "hard" science fiction involves the use of pulsars for space navigation. You emerge from some sort of FTL travel and look around for a few pulsars. Since each is uniquely defined by its timing, you can use them as references to place your position in 3D space. And since all of them are slowing down, with sufficiently accurate time measurement technology you should even be able to use them in the way GPS works, by working out distances based on different time-of-flight calculations.
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Re: APOD: NICER at Night (2019 Jun 01)

Post by orin stepanek » Mon Jun 03, 2019 11:32 am

Chris Peterson wrote:
Sun Jun 02, 2019 1:28 pm
orin stepanek wrote:
Sat Jun 01, 2019 3:11 pm
Natural navigation assistance? :shock:
A common feature of a lot of good, "hard" science fiction involves the use of pulsars for space navigation. You emerge from some sort of FTL travel and look around for a few pulsars. Since each is uniquely defined by its timing, you can use them as references to place your position in 3D space. And since all of them are slowing down, with sufficiently accurate time measurement technology you should even be able to use them in the way GPS works, by working out distances based on different time-of-flight calculations.
When I was a young-un ; we lived on the edge of a small town! Kind of like; after our back yard you were in the country! Any way; i would watch a lot of farming being done with a team of horses or a small ford tractor! Back then; space travel was Flash Gordon and Buck Rogers! Now! Well; we come a long way Baby! :wink:
Orin

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Re: APOD: NICER at Night (2019 Jun 01)

Post by BDanielMayfield » Mon Jun 03, 2019 12:07 pm

orin stepanek wrote:
Mon Jun 03, 2019 11:32 am
Chris Peterson wrote:
Sun Jun 02, 2019 1:28 pm
orin stepanek wrote:
Sat Jun 01, 2019 3:11 pm
Natural navigation assistance? :shock:
A common feature of a lot of good, "hard" science fiction involves the use of pulsars for space navigation. You emerge from some sort of FTL travel and look around for a few pulsars. Since each is uniquely defined by its timing, you can use them as references to place your position in 3D space. And since all of them are slowing down, with sufficiently accurate time measurement technology you should even be able to use them in the way GPS works, by working out distances based on different time-of-flight calculations.
When I was a young-un ; we lived on the edge of a small town! Kind of like; after our back yard you were in the country! Any way; i would watch a lot of farming being done with a team of horses or a small ford tractor! Back then; space travel was Flash Gordon and Buck Rogers! Now! Well; we come a long way Baby! :wink:
Well not so fast Orin. As far as interstellar travel is concerned, we don't even have the equivalent of a tamed horse yet!
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Re: APOD: NICER at Night (2019 Jun 01)

Post by orin stepanek » Mon Jun 03, 2019 3:21 pm

BDanielMayfield wrote:
Mon Jun 03, 2019 12:07 pm
orin stepanek wrote:
Mon Jun 03, 2019 11:32 am
Chris Peterson wrote:
Sun Jun 02, 2019 1:28 pm


A common feature of a lot of good, "hard" science fiction involves the use of pulsars for space navigation. You emerge from some sort of FTL travel and look around for a few pulsars. Since each is uniquely defined by its timing, you can use them as references to place your position in 3D space. And since all of them are slowing down, with sufficiently accurate time measurement technology you should even be able to use them in the way GPS works, by working out distances based on different time-of-flight calculations.
When I was a young-un ; we lived on the edge of a small town! Kind of like; after our back yard you were in the country! Any way; i would watch a lot of farming being done with a team of horses or a small ford tractor! Back then; space travel was Flash Gordon and Buck Rogers! Now! Well; we come a long way Baby! :wink:
Well not so fast Orin. As far as interstellar travel is concerned, we don't even have the equivalent of a tamed horse yet!
I didn't say that; I merely said we came a long way! Of coarse you're no old enough to remember the horse and buggy days! And we have came a long way! We were lucky to live in a town that had electricity! My dad had an old ''29 Buick that he drove well into the 50's! I'm not going so fast as you ass u me; just reflecting on how much more we have and what can become!
Orin

Smile today; tomorrow's another day!