APOD: NGC 2392: Double-Shelled Planetary... (2020 Feb 16)

[APOD Robot]

NGC 2392: Double-Shelled Planetary Nebula

Explanation: To some, this huge nebula resembles a person's head surrounded by a parka hood. In 1787, astronomer William Herschel discovered this unusual planetary nebula: NGC 2392. More recently, the Hubble Space Telescope imaged the nebula in visible light, while the nebula was also imaged in X-rays by the Chandra X-ray Observatory. The featured combined visible-X ray image, shows X-rays emitted by central hot gas in pink. The nebula displays gas clouds so complex they are not fully understood. NGC 2392 is a double-shelled planetary nebula, with the more distant gas having composed the outer layers of a Sun-like star only 10,000 years ago. The outer shell contains unusual light-year long orange filaments. The inner filaments visible are being ejected by strong wind of particles from the central star. The NGC 2392 Nebula spans about 1/3 of a light year and lies in our Milky Way Galaxy, about 3,000 light years distant, toward the constellation of the Twins (Gemini).

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[Ann]

NGC 2362. Placid for now. Photo: Sergio Eguivar.

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Ah, NGC 2392, I thought when I saw the NGC designation of today's 24 hours' of APOD fame, that is one of my absolutely favorite clusters...yes?

No! The cluster I was thinking of is NGC 2362, a magnificent cluster in Canis Major with a fantastic central star, Tau Canis Majoris!

Jim Kaler wrote about Tau Canis Majoris (Tau CMa):
Almost fifth magnitude (4.40), and needing reasonably dark conditions to see, it is one of the sky's rare very hot and blue class O (O9) supergiants, its modest apparent brightness the result of its huge distance of 4800 light years, the light you see having left the star around 2800 BC!

It is so far away that we would not have a good handle on its distance at all except for the fact that Tau is the premier member (or so most believe) of a star cluster called NGC (for New General Catalogue) 2362. Since we can easily compare the brightnesses of stars within such a cluster with those of clusters whose distances we do know, we can find NGC 2362's distance quite accurately.

More important, Tau CMa is a massive multiple star, having at least five components...

The brilliance of these stars reveals their huge masses, the inner four together shining with the light of half a million Suns, which suggests average masses around 20 times solar...

We speculate that the stars were not born in this configuration, but that the bright quartet was formed when two doubles within the cluster passed too close together and merged to create this remarkable system.

Such a complex high-mass multiple star reminds me of the Trapezium Cluster in the Orion Nebula and also the star Iota Orionis:

Trapezium Cluster in M42. Image: NASA; K.L. Luhman (Harvard-Smithsonian Center for Astrophysics, Cambridge, Mass.); and G. Schneider, E. Young, G. Rieke, A. Cotera, H. Chen, M. Rieke, R. Thompson (Steward Observatory, University of Arizona, Tucson, Ariz.)

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Deept-sky objects in Orion, including the Orion Nebula with the Trapezium cluster (overexposed here) and the star Iota Orionis. Photo: Bob King.

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Jim Kaler wrote about Iota Orionis (Na'ir al Saif) and the Trapzieum cluster:

Na'ir al Saif and its close companion help reveal the power of gravity and stellar dynamics. Twenty-six degrees to the south lies fourth magnitude Mu Columbae (in Columba, the Dove); 40 degrees to the north in Auriga lies the variable star AE Aurigae. The two, with spectral classes nearly identical to that of Na'ir al Saif, are hurtling away from each other in opposite directions at 200 kilometers per second. Called "runaway stars," they appear to have been shot out of Orion. Na'ir al Saif still lingers near the Orion Nebula, marking the place of the violent event.

Recent calculations of the movements of the stars explain the two runaways and Na'ir al Saif as well, showing that they were all kicked out of the Trapezium Cluster. Some 2.5 million years ago, the Trapezium region held a pair of tightly-knit double stars. In a very close encounter between the two binaries, two of the four stars were ejected, while the remaining two, instead of being evicted, stayed more or less behind in highly eccentric embrace.

AE Aurigae, plowing through and ionizing the Flaming Star Nebula after having been kicked out of the Trapezium region. Image Credit & Copyright: Martin Pugh.

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[starsurfer]

It's so good to see a planetary nebula on APOD! I wish there was a planetary nebula on APOD every single month.

[orin stepanek]

Wasn't this nebula referred to as the eskimo a while back? Or do I have it mixed up with some other nebula?

[orin stepanek]

NGC2392_HubbleSchmidt_960.jpg

Wasn't this nebula referred to as the eskimo a while back? Or do I have it mixed up with some other nebula?

Nevermind NGC 2392.

[Tszabeau]

Beautiful and interesting composition. It reminds me more of a Portuguese man-of-war than fur hooded head. I do have to wonder how they stuffed light year long filaments into a one-third light year wide nebula, though.

[neufer]

Beautiful and interesting composition. It reminds me more of a Portuguese man-of-war than fur hooded head. I do have to wonder how they stuffed light year long filaments into a one-third light year wide nebula, though.

• It helps a little to be a TWO-thirds light year wide nebula:

Radius = distance × sin(angular size / 2) = ≥2900 ly * sin(48″ / 2) = ≥0.34 ly

Portuguese man o' war in Tayrona National Natural Park, Colombia

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<<The Portuguese man o' war (Physalia physalis) is a marine hydrozoan found in the Atlantic, Indian and Pacific Oceans. It is one of two species in the genus Physalia, along with the Pacific man o' war (or Australian blue bottle), Physalia utriculus. Its long tentacles deliver a painful sting, which is venomous and powerful enough to kill fish and even humans. Despite its appearance, the Portuguese man o' war is not a true jellyfish but a siphonophore, which is not an individual multicellular organism (true jellyfishes are single organisms), but a colonial organism made up of many specialized animals of the same species, called zooids or polyps. These polyps are attached to one another and physiologically integrated, to the extent that they cannot survive independently, creating a symbiotic relationship, requiring each polyp to work together and function like an individual animal.>>

[Bird_Man]

Beautiful and interesting composition. It reminds me more of a Portuguese man-of-war than fur hooded head. I do have to wonder how they stuffed light year long filaments into a one-third light year wide nebula, though.

It looks like the orange filaments extend beyond the outer shell. They show up best between 1:30 and 3:00 in the image.

[SpaceCadet]

Kind of looks like a mantids head rather than a parka covered person.
But beautiful.

[redodson]

Am I missing something? If I read correctly, you say that the string-like filaments in the outer shell are about one light year long. But then you state that NGC 2392 is approximately 1/3 light year in diameter. Surely both estimates can't be correct. Maybe NGC 2392 is about 3 light years in diameter?

[redodson]

Maybe there's an even larger outer layer we can't see in the photograph that contain the light year long filaments?

[ta152h0]

Would the Solar System be just a speck in this picture?

[redodson]

As another reader pointed out, some of the filaments (from about 1 to 2 o'clock in the photo) do appear to extend well beyond the outer shell boundary. Are these the strands that are about 1 light year long? That poses another question: Why do most of the filaments seem to terminate abruptly at the outer shell boundary, while a few of them seen to extend well beyond it? I suppose that is why planetary nebulae are so fascinating - they raise so many questions - and, of course, most of them are extraordinarily beautiful.

[MarkBour]

Would the Solar System be just a speck in this picture?

The diameter of our solar system can be characterized in very different ways. If you use Neptune's orbit as a very conservative measure, it's within about 9 x 10^9 km. So, 1/3 light year, at about (1/3) * 9 * 10^12 km, is around 330 times as large.

Our solar system out to Neptune would be pretty small in this image, about 1/330th of the diameter of the outer shell shown.

[neufer]

The distance from the Oort cloud to the interior of the Solar System, and two of the nearest stars, is measured in astronomical units. The scale is logarithmic. The red arrow indicates the location of the space probe Voyager 1, which will reach the Oort cloud in about 300 years.

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Would the Solar System be just a speck in this picture?

The diameter of our solar system can be characterized in very different ways. If you use Neptune's orbit as a very conservative measure, it's within about 9 x 10^9 km. So, 1/3 light year, at about (1/3) * 9 * 10^12 km, is around 330 times as large.

Our solar system out to Neptune would be pretty small in this image, about 1/330th of the diameter of the outer shell shown.

However, the diameter of the outer shell shown is 2/3 of a light year.

Oort Neuendorffer

[Cynic]

We are all Kosh

[MarkBour]

[The distance from the Oort cloud to the interior of the Solar System, and two of the nearest stars, is measured in astronomical units. The scale is logarithmic. The red arrow indicates the location of the space probe Voyager 1, which will reach the Oort cloud in about 300 years.]

Would the Solar System be just a speck in this picture?

The diameter of our solar system can be characterized in very different ways. If you use Neptune's orbit as a very conservative measure, it's within about 9 x 10^9 km. So, 1/3 light year, at about (1/3) * 9 * 10^12 km, is around 330 times as large.

Our solar system out to Neptune would be pretty small in this image, about 1/330th of the diameter of the outer shell shown.

However, the diameter of the outer shell shown is 2/3 of a light year.

Oort Neuendorffer

Art: That's a very nice Voyager & Solar System diagram! And thanks for the correction. I took the APOD caption:
"The NGC 2392 Nebula spans about 1/3 of a light year" to mean diameter, but Wikipedia agrees with you that 1/3 ly is the radius for the Eskimo nebula.

[neufer]

I took the APOD caption:

"The NGC 2392 Nebula spans about 1/3 of a light year" to mean diameter,

but Wikipedia agrees with you that 1/3 ly is the radius for the Eskimo nebula.

When the ship hits the span

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span (n.1) "distance between two objects," from Old English span "distance between the thumb and little finger of an extended hand" (as a measure of length, roughly nine inches), probably related to Middle Dutch spannen "to join, fasten." The Germanic word was borrowed into Medieval Latin as spannus, hence Italian spanna, Old French espan "hand's width, span as a unit of measure," French empan. As a measure of volume (early 14c.), "what can be held in two cupped hands." Meaning "length of time" first attested 1590s; that of "space between abutments of an arch, etc." is from 1725.>>

[MarkBour]

When the ship hits the span

Priceless. And a good example of what happens when one uses the wrong measurement?

[RJN]

I misinterpreted how Judy Schmidt composed the image, thinking that she included X-ray emission mapped by Chandra. I now understand that the featured image does not include X-ray emission. Therefore, the explanation has now been updated on the main NASA APOD site to not mention X-rays. I apologize for the oversight. - RJN