APOD: Bright Planetary Nebula NGC 7027... (2020 Jun 30)

[APOD Robot]

Bright Planetary Nebula NGC 7027 from Hubble

Explanation: What created this unusual planetary nebula? NGC 7027 is one of the smallest, brightest, and most unusually shaped planetary nebulas known. Given its expansion rate, NGC 7027 first started expanding, as visible from Earth, about 600 years ago. For much of its history, the planetary nebula has been expelling shells, as seen in blue in the featured image. In modern times, though, for reasons unknown, it began ejecting gas and dust (seen in red) in specific directions that created a new pattern that seems to have four corners. These shells and patterns have been mapped in impressive detail by recent images from the Wide Field Camera 3 onboard the Hubble Space Telescope. What lies at the nebula's center is unknown, with one hypothesis holding it to be a close binary star system where one star sheds gas onto an erratic disk orbiting the other star. NGC 7027, about 3,000 light years away, was first discovered in 1878 and can be seen with a standard backyard telescope toward the constellation of the Swan (Cygnus).

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[orin stepanek]

It is unique, but I like it!

[Case]

Perhaps not a very popular nebula, but it has been featured here before:
https://apod.nasa.gov/apod/ap180109.html
https://apod.nasa.gov/apod/ap130826.html
https://apod.nasa.gov/apod/ap980325.html
https://apod.nasa.gov/apod/ap960117.html

[BDanielMayfield]

It's worth discussing due to it's uniqueness as the youngest(?) PN as yet discovered. Note what the wikipedia article on NGC 7027 has to say:

NGC 7027 is one of the visually brightest planetary nebulae.[6] It is about 600 years old.[7]

It is unusually small, measuring only 0.2 by 0.1 light-years, whereas the typical size for a planetary nebula is 1 light-year.[4] It has a very complex shape, consisting of an elliptical region of ionized gas[8] within a massive neutral cloud.[9] The inner structure is surrounded by a translucent shroud of gas and dust.[10] The nebula is shaped like a prolate ellipsoidal shell and contains a photodissociation region shaped like a "clover leaf".[8] NGC 7027 is expanding at 17 kilometers per second (11 mi/s).[9] The central regions of NGC 7027 have been found to emit X-rays, indicating very high temperatures.[8] Surrounding the ellipsoidal nebula are a series of faint, blue concentric shells.[11]

It is possible that the central white dwarf of NGC 7027 has an accretion disk that acts as a source of high temperatures.[12] The white dwarf is believed to have a mass approximately 0.7 times the mass of the Sun and is radiating at 7,700 times the Sun's luminosity.[6] NGC 7027 is currently in a short phase of planetary nebula evolution in which molecules in its envelope are being dissociated into their component atoms, and the atoms are being ionized.[13]

The expanding halo of NGC 7027 has a mass of about three times the mass of the Sun, and is about 100 times more massive than the ionized central region. This mass loss in NGC 7027 provided important evidence that stars a few times more massive than the Sun can avoid being destroyed in supernova explosions.[4]

NGC 7027 has a rich and highly ionized spectrum caused by its hot central star.[5] The nebula is rich in carbon, and is a very interesting object for the study of carbon chemistry in dense molecular material exposed to strong ultraviolet radiation.[14] The spectrum of NGC 7027 contains fewer spectral lines from neutral molecules than is usual for planetary nebulae. This is due to the destruction of neutral molecules by intense UV radiation.[15] The nebula contains ions of extremely high ionization potential.[16] The helium hydride ion, thought to be the earliest molecule to have been formed in the Universe (about 100,000 years after the Big Bang), was detected in 2019 for the first time in space in NGC 7027.[17][18] There is also evidence for the presence of nanodiamond in NGC 7027.[19]

It has been photographed multiple times by the Hubble Space Telescope since its launch in 1990.[20][21] Prior to these observations, NGC 7027 was thought to be a proto-planetary nebula with the central star too cool to ionize any of the gas, but it is now known to be a planetary nebula in the earliest stage of its development.[4] The progenitor star is believed to have been about 3 to 4 times the mass of the Sun before the nebula was formed.[5]

I am impressed by the efficiency of such stars in how much of their mass is returned to interstellar space. NGC 7027's progenitor went from about 3.5 suns down to about 0.7 in forming this baby nebula.

[neufer]

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Scutiphora pedicellata, a jewel bug from Australia

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<<Scutelleridae are commonly known as jewel bugs or metallic shield bugs due to their often brilliant coloration. These insects feed on plant juices from a variety of different species, including some commercial crops. During feeding, jewel bugs inject proteolytic enzymes in their saliva into plants, digesting plant matter into a liquid form which they then suck up.

Jewel bugs are small to medium-sized oval-shaped bugs with a body length averaging at 5 to 20 mm. Male jewel bugs of the genus Hotea possess an unusually large, spiky, and heavily sclerotized genitalia. They are used in a mating practice known as traumatic insemination, a result of evolutionary sexual conflict. Male Hotea bugs tear through the female reproductive ducts to deposit sperm, inflicting substantial damage to the female in the process.

Iridescence (or goniochromism) are caused by the interference, diffraction, or scattering of light by numerous tiny structures. In Poecilocoris lewisi, multiple tiny conical protuberances around 900 nm in height and averaging at a diameter of 360 nm are scattered on the epicuticle. These structures affect light passing through them, producing their oily-looking blue sheen (known as the Tyndall effect or Mie scattering). In other species like the African shield bug (Calidea panaethiopica), the dorsal cuticle is dotted with tiny regularly spaced hemispherical cavities. The depressions act like Bragg mirrors. When light hits the pitted surface, it gives off multiple reflections resulting in the distinctive two tone yellow-blue iridescence.

Like all hemipterans, jewel bugs undergo incomplete metamorphosis (hemimetaboly) and do not possess larval and pupal stages. Instead the adults develop from several stages (instars) of nymphs (usually five) through successive moltings (ecdysis). Nymphs resemble the adults except for size and the absence of wings. They can be of different coloration or patterns from adults.

Like stink bugs, a vast majority of jewel bugs, both adults and nymphs, are also capable of releasing pungent defensive chemicals from glands located on the sides of the thorax. Typical compounds exuded by jewel bugs include alcohols, aldehydes, and esters. Nymphs and adults often exhibit clustering behavior, being found in large numbers close to each other. This behavior is thought to have an evolutionary advantage. The more individuals present in an area, the stronger the odor of the chemicals released when the bugs are threatened. If this fails, stink bugs will react to threat by flying away or dropping to the ground.>>

[TheZuke!]

It seems perfect for the name, "Road Kill Nebula".

[Ann]

Perhaps not a very popular nebula, but it has been featured here before:
https://apod.nasa.gov/apod/ap180109.html
https://apod.nasa.gov/apod/ap130826.html
https://apod.nasa.gov/apod/ap980325.html
https://apod.nasa.gov/apod/ap960117.html

Goodness, Case, it is the most popular nebula ever here at APOD, unless I'm very much mistaken. I got quite fed up with the page after page after page of name suggestions for NGC 7027. It kept on and on and on until it hit 49 pages!

Ann

[Ann]

I am impressed by the efficiency of such stars in how much of their mass is returned to interstellar space. NGC 7027's progenitor went from about 3.5 suns down to about 0.7 in forming this baby nebula.

Puny 0.123 M⊙︎ red dwarf Proxima Centauri, which is not likely to give back appreciable amounts of its mass for the duration of the lifetime of the Universe. Photo: Marco Lorenzi.

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Regulus, a 3.8 M⊙︎ blue main sequence star. It will give back most of its mass to the Universe in a few hundred million years. In the same field of view as Regulus is dwarf galaxy UGC 5470. Photo: Chris Cook.

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Yes, high mass stars are "da shit"!

Not only do they burn bright and blue during their main sequence life times, but they also give back most of their mass to the Universe when they die, so that their mass can be recycled.

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Stingy little red dwarfs glow wanly in the Universe and guard their mass supply more miserly than Uncle Scrooge guards his gold. No wonder that the Universe is running out of free gas, when all those little red stars have gobbled most of it up and refuse to give it back!

Ann

[neufer]

<<Like stink bugs, a vast majority of jewel bugs, both adults and nymphs, are also capable of releasing pungent defensive chemicals from glands located on the sides of the thorax. Typical compounds exuded by jewel bugs include alcohols, aldehydes, and esters. Nymphs and adults often exhibit clustering behavior, being found in large numbers close to each other. This behavior is thought to have an evolutionary advantage. The more individuals present in an area, the stronger the odor of the chemicals released when the bugs are threatened. If this fails, stink bugs will react to threat by flying away or dropping to the ground.>>

Spacefill model of the helium hydride ion

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<<Noted as the strongest known acid, the helium hydride ion (or hydridohelium(1+) ion or helonium) is a cation with chemical formula HeH⁺. It consists of a helium atom bonded to a hydrogen atom, with one electron removed. Since HeH⁺ cannot be stored in any usable form, its chemistry must be studied by forming it in situ. HeH⁺ has long been conjectured since the 1970s to exist in the interstellar medium. In 1956, M. Cantwell predicted theoretically that the spectrum of vibrations of that ion should be observable in the infrared. Its first detection, in the nebula NGC 7027, (using the airborne SOFIA telescope) was reported in an article published in the journal Nature in April 2019.

HeH⁺ is of fundamental importance in understanding the chemistry of the early universe. This is because hydrogen and helium were almost the only types of atoms formed in Big Bang nucleosynthesis. Stars formed from the primordial material should contain HeH⁺, which could influence their formation and subsequent evolution. In particular, its strong dipole moment makes it relevant to the opacity of zero-metallicity stars. HeH⁺ is also thought to be an important constituent of the atmospheres of helium-rich white dwarfs, where it increases the opacity of the gas and causes the star to cool more slowly. Several locations had been suggested as possible places HeH⁺ might be detected. These included cool helium stars, H II regions, and dense planetary nebulae. HeH⁺ could be formed in the cooling gas behind dissociative shocks in dense interstellar clouds, such as the shocks caused by stellar winds, supernovae and outflowing material from young stars. If the speed of the shock is greater than about 90 kilometres per second, quantities large enough to detect might be formed. If detected, the emissions from HeH⁺ would then be useful tracers of the shock.

The helium hydride ion is formed during the decay of tritium in the molecule HT or tritium molecule (T₂ = ³H₂). Although excited by the recoil from the beta decay, the molecule remains bound together. The ion was first produced in a laboratory in 1925. It is stable in isolation, but extremely reactive, and cannot be prepared in bulk, because it would react with any other molecule with which it came into contact. Unlike the dihydrogen ion H₂⁺, the helium hydride ion has a permanent dipole moment, which makes its spectroscopic characterization easier. The electron density in the ion is higher around the helium nucleus than the hydrogen. 80% of the electron charge is closer to the helium nucleus than to the hydrogen nucleus. Spectroscopic detection is hampered, because one of its most prominent spectral lines, at 149.14 μm, coincides with a doublet of spectral lines belonging to the methylidyne radical ⫶CH. Unlike the helium hydride ion, the neutral helium hydride molecule HeH is not stable in the ground state. However, it does exist in an excited state as an excimer (HeH^*), and its spectrum was first observed in the mid 1980s.>>

[BDanielMayfield]

As if space travel wasn't hard enough, now there's the real possibility of running into a cloud of helonium (HeH⁺) gas, an acid so strong it will react with all other molecules Yikes No material vessel can possibly contain it!

Another thing you learned in school that ain't true: Noble gases (like Helium) don't or can't form molecules. Turns out HeH was one of the first molecules ever to form (after H₂).

Bruce

[BDanielMayfield]

Perhaps not a very popular nebula, but it has been featured here before:
https://apod.nasa.gov/apod/ap180109.html
https://apod.nasa.gov/apod/ap130826.html
https://apod.nasa.gov/apod/ap980325.html
https://apod.nasa.gov/apod/ap960117.html

Goodness, Case, it is the most popular nebula ever here at APOD, unless I'm very much mistaken. I got quite fed up with the page after page after page of name suggestions for NGC 7027. It kept on and on and on until it hit 49 pages!

Ann

I got fed up with that Name This Nebula thread too Ann. Kill the thread! It's not a fluffy pillow or a tasty marshmallow kids, it's full of superheated helonium acid

[neufer]

Click to play embedded YouTube video.

As if space travel wasn't hard enough, now there's the real possibility of running into a cloud of helonium (HeH⁺) gas, an acid so strong it will react with all other molecules Yikes No material vessel can possibly contain it!

Another thing you learned in school that ain't true: Nob[le] gases (like Helium) don't or can't form molecules. Turns out HeH was one of the first molecules ever to form (after H₂).

https://en.wikipedia.org/wiki/Noble_gas_compound

[neufer]

Full of superheated helonium acid?

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https://apod.nasa.gov/apod/ap180109.html
https://apod.nasa.gov/apod/ap130826.html
https://apod.nasa.gov/apod/ap980325.html
https://apod.nasa.gov/apod/ap960117.html

[NGC 7027]'s not a fluffy pillow or a tasty marshmallow kids,

it's full of superheated helonium acid

[BDanielMayfield]

Click to play embedded YouTube video.

Nice one Art.

As if space travel wasn't hard enough, now there's the real possibility of running into a cloud of helonium (HeH⁺) gas, an acid so strong it will react with all other molecules Yikes No material vessel can possibly contain it!

Another thing you learned in school that ain't true: Nob[le] gases (like Helium) don't or can't form molecules. Turns out HeH was one of the first molecules ever to form (after H₂).

The last shock smily was Art's, not mine. What, you weren't told in high school that Noble gases were inert??? I'm shocked.

[BDanielMayfield]

Full of superheated helonium acid?

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https://apod.nasa.gov/apod/ap180109.html
https://apod.nasa.gov/apod/ap130826.html
https://apod.nasa.gov/apod/ap980325.html
https://apod.nasa.gov/apod/ap960117.html

[NGC 7027]'s not a fluffy pillow or a tasty marshmallow kids,

it's full of superheated helonium acid

Very funny

[neufer]

The last shock smily was Art's, not mine.

What, you weren't told in high school that Nobel gases were inert??? I'm shocked.

My shock was that No one at my high school told me about "Nobel" gases.

<<Nobelium is a synthetic chemical element with the symbol No and atomic number 102. It is named in honor of Alfred Nobel, the inventor of dynamite and benefactor of science. A radioactive metal, it is the penultimate member of the actinide series. A total of twelve nobelium isotopes are known to exist; the most stable is ²⁵⁹No with a half-life of 58 minutes, but the shorter-lived ²⁵⁵No (half-life 3.1 minutes) is most commonly used in chemistry because it can be produced on a larger scale.

Chemistry experiments have confirmed that nobelium behaves as a heavier homolog to ytterbium in the periodic table. The long No–H distances in the NoH₂ molecule and the significant charge transfer lead to extreme ionicity with a dipole moment of 5.94 D. In this molecule, nobelium is expected to exhibit main-group-like behavior, specifically acting like an alkaline earth metal. In 1967, experiments were conducted to compare nobelium's chemical behavior to that of terbium, californium, and fermium. All four elements were reacted with chlorine and the resulting chlorides were deposited along a tube, along which they were carried by a gas. It was found that the nobelium chloride produced was strongly adsorbed on solid surfaces, proving that it was not very volatile, like the chlorides of the other three investigated elements. However, both NoCl₂ and NoCl₃ were expected to exhibit nonvolatile behavior and hence this experiment was inconclusive as to what the preferred oxidation state of nobelium was.>>

[BDanielMayfield]

No one should be shocked at my misspellings, given my edjurfikation, but I have the noble goal of increased knowledge none the less.

[MarkBour]

As if space travel wasn't hard enough, now there's the real possibility of running into a cloud of helonium (HeH⁺) gas, an acid so strong it will react with all other molecules Yikes No material vessel can possibly contain it!

Another thing you learned in school that ain't true: Noble gases (like Helium) don't or can't form molecules. Turns out HeH was one of the first molecules ever to form (after H₂).

Bruce

As awful as it sounds, I would guess that the helonium acid is not any worse than ionized hydrogen is already.

[Ann]

Alfred Nobel, a case of indigestion?

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What, you weren't told in high school that Nobel gases were inert??? I'm shocked.

My shock was that No one at my high school told me about "Nobel" gases.

Sorry. Couldn't resist.

Ann

[BDanielMayfield]

As if space travel wasn't hard enough, now there's the real possibility of running into a cloud of helonium (HeH⁺) gas, an acid so strong it will react with all other molecules Yikes No material vessel can possibly contain it!

Another thing you learned in school that ain't true: Noble gases (like Helium) don't or can't form molecules. Turns out HeH was one of the first molecules ever to form (after H₂).

Bruce

As awful as it sounds, I would guess that the helonium acid is not any worse than ionized hydrogen is already.

Interesting point Mark. Is there a chemist in the house?

I was trying to make it sound as awful as I could, while still being factual. Also, there's the fact that since it reacts with everything, it can also be neutralized by everything.

Cancel Red Alert.

[TheOtherBruce]

What lies at the nebula's center is unknown, with one hypothesis holding it to be a close binary star system where one star sheds gas onto an erratic disk orbiting the other star.

I'm curious about this bit. If the star is a close binary, shouldn't that show up with doppler shift splitting of the lines in the spectrum? Is there an orbital geometry where the splitting can't be detected?

[TheZuke!]

I haven't seen the 49 pages of names that Ann mentioned,
but another possibility that occurred to me is "Flying Squirrel Nebula".

[BDanielMayfield]

What lies at the nebula's center is unknown, with one hypothesis holding it to be a close binary star system where one star sheds gas onto an erratic disk orbiting the other star.

I'm curious about this bit. If the star is a close binary, shouldn't that show up with doppler shift splitting of the lines in the spectrum? Is there an orbital geometry where the splitting can't be detected?

Since no one else has answered I'll suggest a possible explanation. Since this Planetary Nebula is so young the density of the outflowing material is too high to see the star(s) at the center of this system. Therefore no stellar spectroscopy is possible. A this point the binary status is just an inference based on the appearance of the PN.

[Ann]

I haven't seen the 49 pages of names that Ann mentioned,
but another possibility that occurred to me is "Flying Squirrel Nebula".

southern_flying_squirrel.jpg

Not quite the same thing, but

Ann

[MarkBour]

As if space travel wasn't hard enough, now there's the real possibility of running into a cloud of helonium (HeH⁺) gas, an acid so strong it will react with all other molecules Yikes No material vessel can possibly contain it!

Another thing you learned in school that ain't true: Noble gases (like Helium) don't or can't form molecules. Turns out HeH was one of the first molecules ever to form (after H₂).

Bruce

As awful as it sounds, I would guess that the helonium acid is not any worse than ionized hydrogen is already.

Interesting point Mark. Is there a chemist in the house?

I was trying to make it sound as awful as I could, while still being factual. Also, there's the fact that since it reacts with everything, it can also be neutralized by everything.

Cancel Red Alert.

He he. And now I feel bad for being a spoil-sport about it.
The red alert might be warranted, for all I know.

Here's one of the many examples of how space (even very near to home) messes with my intuition:

From Wikipedia's article on the Thermosphere https://en.wikipedia.org/wiki/Thermosphere

The highly attenuated gas in this layer can reach 2,500 °C (4,530 °F) during the day. Despite the high temperature, an observer or object will experience cold temperatures in the thermosphere, because the extremely low density of gas (practically a hard vacuum) is insufficient for the molecules to conduct heat. A normal thermometer will read significantly below 0 °C (32 °F), at least at night, because the energy lost by thermal radiation would exceed the energy acquired from the atmospheric gas by direct contact.

I find this odd: Don't go flying around up in the thermosphere without some protection. Why? Because you'll quickly freeze to death up in that 2,500 °C air. That was hard for me to reconcile.

Back to the subject of the nebula NGC 7027, I wouldn't want to mess with helonium acid. If a molecule of it hit our spaceship, it would give away its proton, and it would damage the ship. But it depends on how much of it is around, or how much of it we needed to fly through, I guess.