APOD: The Pale Blue Dot (2020 Feb 14)

[APOD Robot]

The Pale Blue Dot

Explanation: On Valentine's Day in 1990, cruising four billion miles from the Sun, the Voyager 1 spacecraft looked back one last time to make the first ever Solar System family portrait. The portrait consists of the Sun and six planets in a 60 frame mosaic made from a vantage point 32 degrees above the ecliptic plane. Planet Earth was captured within a single pixel in this single frame. It's the pale blue dot within the sunbeam just right of center in this reprocessed version of the now famous view from Voyager. Astronomer Carl Sagan originated the idea of using Voyager's camera to look back toward home from a distant perspective. Thirty years later, on this Valentine's day, look again at the pale blue dot.

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[Ann]

Four of the six Hubble Frontier Fields. The regions imaged parallel to these clusters were used to search for a new type of galaxy, termed “little blue dots”. NASA

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Sky & Telescope wrote:
As telescope capabilities improve and we develop increasingly deeper large-scale surveys of our universe, we continue to learn more about small, faraway galaxies. In recent years, increasing sensitivity first enabled the detection of “green peas” — luminous, compact, low-mass (<10 billion solar masses; compare this to the Milky Way’s ~1 trillion solar masses!) galaxies with high rates of star formation.

Not long thereafter, we discovered galaxies that form stars similarly rapidly, but are even smaller — only ~3–30 million solar masses, spanning less than ~3,000 light-years in size. These tiny powerhouses were termed “blueberries” for their distinctive color.

Now, scientists Debra and Bruce Elmegreen (of Vassar College and IBM Research Division, respectively) report the discovery of galaxies that have even higher star formation rates and even lower masses: “little blue dots”.

Top: a few examples of the little blue dots recently identified in two Hubble Frontier Field Parallels. Bottom: stacked images for three different groups of little blue dots. Elmegreen & Elmegreen 2017

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Exploring these little blue dots, the Elmegreens find that the galaxies’ sizes tend to be just a few hundred light-years across. They are gas-dominated; gas currently outweighs stars in these galaxies by perhaps a factor of five. Impressively, based on the incredibly high specific star formation rates observed in these little blue dots, they appear to have formed all of their stars in the last 1% of the age of the universe for them.

Elliptical Globular Cluster, M22, is a photograph by N.A. Sharp/REU Program/NOAO/AURA/NSF

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Intriguingly, this rapid star formation might be the key to answering a long-standing question: where do globular clusters come from? The Elmegreens propose that little blue dots might actually be an explanation for the origin of these orbiting, spherical, low-metallicity clusters of stars.

The authors demonstrate that, if the current star formation rates observed in little blue dots were to persist for another ~50 Myr before feedback or gas exhaustion halted star production, the little blue dots could form enough stars to create clusters of roughly a million solar masses — which is large enough to explain the globular clusters we observe today.

Ann

[Boomer12k]

From a long way off....

:---[===] *

[JohnD]

The Pale Blue Dot is a remarkable picture, no doubt about it, as powerful as Earthrise in changing people's views of the cosmos.
But commentators always go on about it being "within one pixel", when on the evidence of this pic, it ain't!

Click on the pic to open in in a new window, click again to magnify it, and you will see that the Dot is bigger than many of the individual pixels of the background, seen as differing tone.
John

[canopia]

This newly processed image looks good. Now there are some background stars visible, is it possible to identify which stars these are?

By the way, it is always nice to see a Valentine's Day APOD with something other than Rosette Nebula or Heart Nebula.

Tunç Tezel

[saturno2]

The Pale Blue Dot is very beautiful
We
We in the infinite
Blue and life

[orin stepanek]

It's good to fave that pale Blue Dot
It is so dear to me

[songwriterz]

Amazing, isn't it? For all we know that pale blue dot represents the sum total of intelligent life in the universe. Why can't we get along? Even if we aren't all there is, aren't we enough? I mean, that's it; that's the sum totality of the human race. Why can't we get along? I'm no greenie or environmentalist or liberal peacenik, but it does seem that all of us could take some reasonable steps to take care of this planet and one another. Why can't different races and religions and doctrines just decide to live and let live and just...get along? If we're all there is, we should do better. Be better.

That's one helluva picture.

[BDanielMayfield]

Amazing, isn't it? For all we know that pale blue dot represents the sum total of intelligent life in the universe. Why can't we get along? Even if we aren't all there is, aren't we enough? I mean, that's it; that's the sum totality of the human race. Why can't we get along? I'm no greenie or environmentalist or liberal peacenik, but it does seem that all of us could take some reasonable steps to take care of this planet and one another. Why can't different races and religions and doctrines just decide to live and let live and just...get along? If we're all there is, we should do better. Be better.

Wonderful sentiment. Individuals can choose do these things, but sadly society as a whole cannot. We are too divided.

[neufer]

Amazing, isn't it? For all we know that pale blue dot represents the sum total of intelligent life in the universe. Why can't we get along? Even if we aren't all there is, aren't we enough? I mean, that's it; that's the sum totality of the human race. Why can't we get along? I'm no greenie or environmentalist or liberal peacenik, but it does seem that all of us could take some reasonable steps to take care of this planet and one another. Why can't different races and religions and doctrines just decide to live and let live and just...get along? If we're all there is, we should do better. Be better.

Clearly, this dot is big enough for the both of us, pardner.

[Chris Peterson]

The Pale Blue Dot is a remarkable picture, no doubt about it, as powerful as Earthrise in changing people's views of the cosmos.
But commentators always go on about it being "within one pixel", when on the evidence of this pic, it ain't!

Click on the pic to open in in a new window, click again to magnify it, and you will see that the Dot is bigger than many of the individual pixels of the background, seen as differing tone.

In fact, Earth is smaller than a single pixel in the data. The narrow angle camera used to capture the image has an image scale of 1.8 arcsec/pixel. At the distance of the spacecraft to the Earth, our planet subtended a mere 0.45 arcsec. You could fit more than 16 Earths in a single pixel!

Of course, if the image of Earth straddled pixels, you could end up with its light being collected on as many as four pixels. And diffraction makes unresolved point sources appear larger. Finally, we have whatever processing was done here to turn an image made from an 800x800 source into something more than 5000 pixels on a side, and then compressed with a lossy algorithm.

The assessment of Earth being within one pixel really is accurate.

[zendae1]

Earth as our Valentine. How sweet it all could be. As sweet as that photo that makes one want to hug our Earth and heal it of our errors.

[MarkBour]

Sky & Telescope wrote:
... Now, scientists Debra and Bruce Elmegreen (of Vassar College and IBM Research Division, respectively) report the discovery of galaxies that have even higher star formation rates and even lower masses: “little blue dots”.

The Elmegreens propose that little blue dots might actually be an explanation for the origin of ... the globular clusters we observe today.

Ann

Fascinating! Thanks for sharing this, Ann.

[ta152h0]

I want a giant poster of this to replace the window to my house! and also, pass me an ice cold one! (applause again!!)

[JohnD]

The assessment of Earth being within one pixel really is accurate.

Thanks, Chris! My scepticism squashed again!
John

[bystander]

'Pale Blue Dot' Revisited
NASA | JPL-Caltech | Voyager | 2020 Feb 12

Voyager 1's Pale Blue Dot
NASA Science | Solar System Exploration | 2019 Feb 05

https://photojournal.jpl.nasa.gov/catalog/PIA23645
https://photojournal.jpl.nasa.gov/catalog/PIA00452
https://photojournal.jpl.nasa.gov/catalog/PIA00451

Iconic 'Pale Blue Dot' Photo -- Carl Sagan's Idea -- Turns 30
Cornell University | 2020 Feb 14

[RickyM]

Wasn't this photo proven to be fake? they worked out that because the distance (6 billion Km) and exposure time (less than 2 seconds) and low resolution (800x800) of Voyager's narrow angle camera means the Earth would be 1/9 of a pixel in size and would never show up on any picture.

[JohnD]

See Chris' answer to my Q, above!

[Deathfleer]

Fantastic. The earth so large yet so small.

[Deathfleer]

Very enticing to a space traveller. Not found elsewhere yet.

[MarkBour]

I find the Voyager 1 "Solar system family portrait" mosaic of 60 images to be an accomplishment that profoundly inspires me.

Years ago in this forum I asked "What is the maximum number of planets anyone has ever imaged at one time?"

I was open to the accomplishment by a camera on a spacecraft, which I figured would eventually take the ultimate such image. I was willing to accept an image that included where a planet was known to be, even if it was too faint to show up. I was open to a mosaic, provided the frames were all taken in a short period of time, as if to capture a single view that some apparatus could have captured from one viewpoint.

At the time, I was unaware of Voyager 1's accomplishment. They skipped over Pluto because they knew they would not be able to see it. And most who describe the family portrait only credit it with seeing 6 of the 8 planets. But by my initial weak criteria, all 8 would be counted. Mercury and Mars were too faint or washed out by the Sun in their images, but their location in the view was captured.

So, it's just phenomenal.

===================

One other shot I hope we have someday. If one of our spacecraft ever got far enough away and still had the ability to take a shot, a single frame centered on the Sun that was far enough away that our entire set of planets would be in the frame, that would be really nice. I imagine that in such a shot, nary a planet would be visible, but you could plot them for reference and get a feel for the distance, and what our Sun and solar system looked like at that distance.

Although I would like having such a shot, which would be meaningful to me, I realize it would not be impressive to look at, and could be simulated today without the need of a spacecraft, so it's possible that nobody else will ever see fit to take such a shot. But if such a shot ever inspired another such as Carl Sagan to pen something half as fine as the pale blue dot image did, then it would surely be worth it.