APOD: A Triple Star is Born (2016 Dec 02)

[APOD Robot]

A Triple Star is Born

Explanation: A triple star system is forming, enshrouded within this dusty natal disk some 750 light-years away in the Perseus molecular cloud. Imaged at millimeter wavelengths by the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, the extreme close-up shows two protostars separated by a mere 61 AU (1 AU is the Earth-Sun distance) with a third 183 AU from the central protostar. The ALMA image also reveals a clear spiral structure indicating instability and fragmentation led to the multiple protostellar objects within the disk. Astronomers estimate that the system, cataloged as L1448 IRS3B, is less than 150,000 years old. Captured at an early phase, the starforming scenario is likely not at all uncommon, since almost half of all sun-like stars have at least one companion.

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[neufer]

Click to play embedded YouTube video.

[bystander]

http://asterisk.apod.com/viewtopic.php?t=36510

[Chris Peterson]

...the extreme close-up shows two protostars separated by a mere 61 AU (1 AU is the Earth-Sun distance) with a a third some 183 AU from the central protostar.

To give a better indication of resolution:

scaled.png (53.5 KiB) Viewed 7650 times

[geckzilla]

[re: the figure Chris posted]
Presumably the little circle in the corner is to give us an indication of the point spread function. The resolution is just astonishing.

Edit:
From the paper:

The resolution of each image is shown with an ellipse(s) drawn in the lower right corner[...]

Hrm, well, I am not sure if I am right or wrong with my initial suspicion.

[Guest]

Is the apparent luminosity an indicator of size? And if so, is the larger of the three 'consuming' the other two or will at least one be ejected from the 'system'?

[Boomer12k]

Welcome to the Galaxy.... hope it goes well...

:---[===] *

[mister T]

Are these protostars at the fusion producing stage yet, Or is their brightness the result of the energy released thru the accretion process?

[sym666]

Wonderful image. The proto-stars seem to be quite near one another, is it known what class of stars are they going to be? Is it possible that they will migrate at different distances?
Thanks

[Alex_577]

The Adaptive Optics behind the instrument must be out of this world.

[ManInFla]

Small mistake here:

with a a third some

In 100 years, perhaps we can get a time-lapse version of this...

[geckzilla]

Is the apparent luminosity an indicator of size?

I've thought about this a bit, and I want to say that it is somewhat an idicator, but I also think that gaseous structures can also form structures which may look bigger and brighter at this resolution, but they might not necessarily be so. The brighter one could be fluffier or currently have a stream of gas that is broader and looks brighter.

[Chris Peterson]

The Adaptive Optics behind the instrument must be out of this world.

Although there are elements of the system that might be considered "adaptive", there is no adaptive optics system in the usual sense of the word. The ALMA system consists of an array of antennas that can be separated by kilometers, meaning that the resolution (0.01 arcsec) is essentially a function of nothing more than a very large aperture- just basic optical principles.

[Ann]

Wonderful image. The proto-stars seem to be quite near one another, is it known what class of stars are they going to be? Is it possible that they will migrate at different distances?
Thanks

I would love to know what spectral classes they are going to be.

I choose an orange-brown color to highlight the question from sym666, because I suspect that they are going to be quite small and cool stars that emit orange light. I believe they are going to be small simply because most stars that are already fully formed in the galaxy are small and cool, and also low-mass star formation is so much more common in the Milky Way than high-mass star formation. Also, when high-mass star formation occurs, it appears that many small stars form for every big and massive one.

Click to view full size image

The Sun adn 61 Cygni. Illustration: RJHall.

But at least it looks as if one of the stars is going to be bigger than the others, and two of the stars - those that are very close together - look like they are going to be considerably smaller. Perhaps the biggest star will be spectral class K, and the two others will be M-class dwarfs?

The picture at left by RJHall shows a size and color comparison between the Sun and the K-class components of 61 Cygni. I must point out that K-class stars are most definitely not as red as the picture suggests - they are in fact not red at all, but yellow-orange - and not even M-class stars are that red. Only carbon stars can be that red, and not even all carbon stars, either.

But I like the image. I think the triple star in today's APOD may grow into adulthood to become something like that.

Ann

[MarkBour]

Is the apparent luminosity an indicator of size?

I've thought about this a bit, and I want to say that it is somewhat an idicator, but I also think that gaseous structures can also form structures which may look bigger and brighter at this resolution, but they might not necessarily be so. The brighter one could be fluffier or currently have a stream of gas that is broader and looks brighter.

One piece of evidence, the overall shape of the spiral structure, would tend to indicate that the greater mass is in its center. One reference in the caption estimates a mass of the two closer protostars totalling about the mass of our Sol, and the mass of the farther "3rd triplet" to be the least of the 3. Why it would appear brightest in this image, though, ... you got me. The signals are radio wavelength, rather than optical.

It is a spectacular image!

[Ann]

One piece of evidence, the overall shape of the spiral structure, would tend to indicate that the greater mass is in its center. One reference in the caption estimates a mass of the two closer protostars totalling about the mass of our Sol, and the mass of the farther "3rd triplet" to be the least of the 3. Why it would appear brightest in this image, though, ... you got me. The signals are radio wavelength, rather than optical.

It is a spectacular image!

Fascinating!

Click to view full size image

Bright-looking yellow binary star Alpha Centauri (G2V + K1V) at 4 light-years,
bright blue binary Beta Centauri (B1III) at 400 light-years,
and (inset) ultra-faint Proxima Centauri (M6V) at 4 light-years.
Photo: Marco Lorenzi.

The ArXiv paper about the triple system wrote:

The inferred mass of the central pair of protostellar objects is ∼1 Msun, while the disk surrounding the three protostars has a total mass of ∼0.30 M$_{\sun}$. The tertiary protostar itself has a minimum mass of ∼0.085 Msun.

This clearly suggests that the two central stars have masses corresponding to late K or early M spectral classes. Most likely, at least one of the central stars will belong to spectral class K, while the other may become a bright-for-its-class main sequence M star.

The third star, if its current mass is a minimum of ∼0.085 solar masses, may become another Proxima Centauri! Really!

Ann

[geckzilla]

Is the apparent luminosity an indicator of size?

I've thought about this a bit, and I want to say that it is somewhat an idicator, but I also think that gaseous structures can also form structures which may look bigger and brighter at this resolution, but they might not necessarily be so. The brighter one could be fluffier or currently have a stream of gas that is broader and looks brighter.

One piece of evidence, the overall shape of the spiral structure, would tend to indicate that the greater mass is in its center. One reference in the caption estimates a mass of the two closer protostars totalling about the mass of our Sol, and the mass of the farther "3rd triplet" to be the least of the 3. Why it would appear brightest in this image, though, ... you got me. The signals are radio wavelength, rather than optical.

I think the fluffy bits of gas in the accretion knot brighten the signal quite a bit compared with a star that is further along in the process that may have cleared more of the gas away from its area. At least, that's what it looks like in a simulation I was looking at:
https://www.youtube.com/watch?v=YbdwTwB8jtc

[alter-ego]

The Adaptive Optics behind the instrument must be out of this world.

Although there are elements of the system that might be considered "adaptive", there is no adaptive optics system in the usual sense of the word. The ALMA system consists of an array of antennas that can be separated by kilometers, meaning that the resolution (0.01 arcsec) is essentially a function of nothing more than a very large aperture- just basic optical principles.

Interestingly, the radio-telescope equivalent of "adaptive optics" are critical to achieve long-baseline, high-resolution performance.
In these arrays, "adaptive optic" technology is electronic-based signal phase correction as opposed to mechanical mirror surface-deflection. At ALMA wavelengths, water vapor variations between antennas can significantly degrade the "seeing" at larger antenna separations as turbulent air does for larger optical telescopes. To improve image quality, ALMA uses Water Vapor Radiometers in each of the 12-m antennas to measure sky brightness (and ultimately the amount of water) within the antenna's field of view. From this data, good estimates can be made for the path length changes between the antennas, resulting in correcting individual signal phases so that they add up with minimum timing/phase error. Despite ALMA's dry location, I was surprised how bad ALMA seeing can be:

The magnitude of the atmospheric fluctuations increases on longer baselines and, at millimetre and particularly submillimetre wavelengths, a baseline length is reached where the path variations are a large fraction of a wavelength and no useful astronomical signal can be reconstructed. This means that, without correction of the phase fluctuations, the angular resolution of the telescope will be limited by the effects of the atmosphere. The resolution achievable without correction is extremely variable, but a typical value is, coincidentally, similar to the optical seeing at good sites, i.e., around 0.5 arcseconds (see for example the analysis of ALMA site-testing data by Evans et al. 2003).

[geckzilla]

And here I am, getting all worked up over zodiacal glow.

[ygmarchi]

These images are a true landmark in astronomy.

[neufer]

The magnitude of the atmospheric fluctuations increases on longer baselines and, at millimetre and particularly submillimetre wavelengths, a baseline length is reached where the path variations are a large fraction of a wavelength and no useful astronomical signal can be reconstructed. This means that, without correction of the phase fluctuations, the angular resolution of the telescope will be limited by the effects of the atmosphere. The resolution achievable without correction is extremely variable, but a typical value is, coincidentally, similar to the optical seeing at good sites, i.e., around 0.5 arcseconds (see for example the analysis of ALMA site-testing data by Evans et al. 2003).

So a resolution of ~115 AU at 750 light-years then.

ALMA might as well have had her clothes stripped off by the atmospheric fluctuations of a passing water cloud.