New Horizons spacecraft answers the question: How dark is space?

Discuss Astrophysics.
Post Reply
User avatar
notFritzArgelander
Universal Ambassador
Articles: 0
Posts: 9087
Joined: Fri May 10, 2019 4:13 pm
1
Location: Idaho US

TSS Awards Badges

New Horizons spacecraft answers the question: How dark is space?

#1

Post by notFritzArgelander »

Scopes: Refs: Orion ST80, SV 80EDA f7, TS 102ED f11 Newts: Z12 f5; Cats: VMC110L, Intes MK66,VMC200L f9.75 EPs: KK Fujiyama Orthoscopics, 2x Vixen NPLs (40-6mm) and BCOs, Baader Mark IV zooms, TV Panoptics, Delos, Plossl 32-8mm. Mixed brand Masuyama/Astroplans Binoculars: Nikon Aculon 10x50, Celestron 15x70, Baader Maxbright. Mounts: Star Seeker III, Vixen Porta II, Celestron CG5, Orion Sirius EQG
User avatar
AntennaGuy
Milky Way Ambassador
Articles: 0
Posts: 1040
Joined: Sun May 19, 2019 1:20 am
1
Location: Tyler, TX USA

Re: New Horizons spacecraft answers the question: How dark is space?

#2

Post by AntennaGuy »

"Their result sets an upper limit to the abundance of faint, unresolved galaxies, showing that they only number in the hundreds of billions, not 2 trillion galaxies as previously believed." Heh. Reminds me of: “There are 10^11 stars in the galaxy. That used to be a huge number. But it's only a hundred billion. It's less than the national deficit! We used to call them astronomical numbers. Now we should call them economical numbers.” -- Richard Feynman
* Meade 323 refractor on a manual equatorial mount.
* Celestron C6 SCT on a Twilight 1 Alt-Az mount
* Losmandy GM8G mount.
* Vixen VMC260L on order.
User avatar
seigell
Mars Ambassador
Articles: 0
Posts: 114
Joined: Mon May 13, 2019 4:59 pm
1
Location: Florida, USA

Re: New Horizons spacecraft answers the question: How dark is space?

#3

Post by seigell »

It is always interesting to hear what is being sought and measured at the limits of Observable Space and Time.

It is also rather interesting to see what conclusions are made from such measurements, which themselves are pushed to the extremities of their Error Bars.

And, while quite likely just choices of emphasis for the Article's author and editor: The choices of what elements to emphasize - rogue intergalactic stars as a source of "extra light"; and what to not reference as being considered - such as the unknown differences in formation or life-stage of these almost undetectable prehistoric galaxies.

I'm left to wonder if these measurements and conclusions are significantly impacted by the "unknowns":
Did the abundance and proximity of so much primordial hydrogen result in tremendously larger - and therefore more luminous - stars than are known in "modern" galaxies??
Did the abundance of so many outlandishly large - and energetic - prehistoric stars cause the expulsion of significant amounts of molecular hydrogen from these nascent galaxies into intergalactic space, where the existence of any fraction of such mass would itself filter/block the light of the galaxies being measured??

It always seems rather "dangerous" to make strong conclusions from such measurements on the very edge of perception (and knowledge)...
ES AR152 / ES 80ED Apo / Orion 8in F/3.9 / C9.25-SCT / C6-SCT / C10-NGT / AT6RC / ST-80 / AstroView 90 / Meade 6000 APO 115mm
CGEM (w HyperTune and ADM bling) / 2x CG5-AGT / Forest of Tripod legs / Star Adventurer / Orion EQ-G
550D (Modded-G.Honis) / 60D / 400D / NexImage / NexGuide / Mini 50 SSAG / ST-8300C / ASI120MM-S / ASI1600MM-Cool
Dark Skies in SW CO when I can get there, and badly light polluted backyard when I can't... (Currently Self-Exiled to Muggy Central Florida...)
User avatar
notFritzArgelander
Universal Ambassador
Articles: 0
Posts: 9087
Joined: Fri May 10, 2019 4:13 pm
1
Location: Idaho US

TSS Awards Badges

Re: New Horizons spacecraft answers the question: How dark is space?

#4

Post by notFritzArgelander »

You raise thoughtful and interesting points. The professional press obsesses over uncertainties. This concern is not reflected in popular articles by science journalists though.
seigell wrote: Wed Jan 13, 2021 6:38 pm It is always interesting to hear what is being sought and measured at the limits of Observable Space and Time.

It is also rather interesting to see what conclusions are made from such measurements, which themselves are pushed to the extremities of their Error Bars.

And, while quite likely just choices of emphasis for the Article's author and editor: The choices of what elements to emphasize - rogue intergalactic stars as a source of "extra light"; and what to not reference as being considered - such as the unknown differences in formation or life-stage of these almost undetectable prehistoric galaxies.

I'm left to wonder if these measurements and conclusions are significantly impacted by the "unknowns":
Did the abundance and proximity of so much primordial hydrogen result in tremendously larger - and therefore more luminous - stars than are known in "modern" galaxies??
This is certainly true. Stellar masses are limited by opacity which is higher for gasses enriched by heavy elements. Higher opacities means lower limits on the masses of stars.
Did the abundance of so many outlandishly large - and energetic - prehistoric stars cause the expulsion of significant amounts of molecular hydrogen from these nascent galaxies into intergalactic space, where the existence of any fraction of such mass would itself filter/block the light of the galaxies being measured??
IIRC molecular hydrogen is not very opaque.
It always seems rather "dangerous" to make strong conclusions from such measurements on the very edge of perception (and knowledge)...
The error treatment in the paper carefully notes the presence of large systematic errors that they take into account. Systematic errors are larger than random errors in the uncertainties.

https://arxiv.org/abs/2011.03052
We used existing data from the New Horizons LORRI camera to measure the optical-band (0.4≲λ≲0.9μm) sky brightness within seven high galactic latitude fields. The average raw level measured while New Horizons was 42 to 45 AU from the Sun is 33.2±0.5 nW m−2 sr−1. This is ∼10× darker than the darkest sky accessible to the {\it Hubble Space Telescope}, highlighting the utility of New Horizons for detecting the cosmic optical background (COB). Isolating the COB contribution to the raw total requires subtracting scattered light from bright stars and galaxies, faint stars below the photometric detection-limit within the fields, and diffuse Milky Way light scattered by infrared cirrus. We remove newly identified residual zodiacal light from the IRIS 100μm all sky maps to generate two different estimates for the diffuse galactic light (DGL). Using these yields a highly significant detection of the COB in the range 15.9±4.2 (1.8 stat.,3.7 sys.) nW m−2 sr−1 to 18.7±3.8 (1.8 stat.,3.3 sys.) nW m−2 sr−1 at the LORRI pivot wavelength of 0.608 μm. Subtraction of the integrated light of galaxies (IGL) fainter than the photometric detection-limit from the total COB level leaves a diffuse flux component of unknown origin in the range 8.8±4.9 (1.8 stat.,4.5 sys.) nW m−2 sr−1 to 11.9±4.6 (1.8 stat.,4.2 sys.) nW m−2 sr−1. Explaining it with undetected galaxies requires the galaxy-count faint-end slope to steepen markedly at V>24 or that existing surveys are missing half the galaxies with V<30.
The modestly stated possibility that there is a steepening of the slope of the galaxy distribution curve at the faint end is a matter of great interest, though. It has the potential for profound consequences for ideas about galaxy formation.
Scopes: Refs: Orion ST80, SV 80EDA f7, TS 102ED f11 Newts: Z12 f5; Cats: VMC110L, Intes MK66,VMC200L f9.75 EPs: KK Fujiyama Orthoscopics, 2x Vixen NPLs (40-6mm) and BCOs, Baader Mark IV zooms, TV Panoptics, Delos, Plossl 32-8mm. Mixed brand Masuyama/Astroplans Binoculars: Nikon Aculon 10x50, Celestron 15x70, Baader Maxbright. Mounts: Star Seeker III, Vixen Porta II, Celestron CG5, Orion Sirius EQG
Post Reply

Return to “Astrophysics”