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NGC 7635: The Bubble Nebula

Explanation: It's the bubble versus the cloud. NGC 7635, the Bubble Nebula, is being pushed out by the stellar wind of massive central star BD+602522. Next door, though, lives a giant molecular cloud, visible to the right. At this place in space, an irresistible force meets an immovable object in an interesting way. The cloud is able to contain the expansion of the bubble gas, but gets blasted by the hot radiation from the bubble's central star. The radiation heats up dense regions of the molecular cloud causing it to glow. The Bubble Nebula, pictured above in scientifically mapped colors to bring up contrast, is about 10 light-years across and part of a much larger complex of stars and shells. The Bubble Nebula can be seen with a small telescope towards the constellation of the Queen of Aethiopia (Cassiopeia).

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Congratulations Larry! great work on the bubble!

I like space bubbles. They're so...so... BIG! And the immovable object tastes good, too. It's also so...so... BIG!!

I wouldn't pretend to understand all the science of the forces making this phenomenon, but on a purely aesthetic level, this is a totally beautiful image. Quite gorgeous how the light catches and highlights the molecular cloud. The blues and ambers could have been painted by an artist. It's like a beautiful sunrise piercing a stormy sky - and, in a way, that is exactly what it is!

starstruck, what a lovely description!

And what a lovely APOD! And immovable object! And other cool links!

Very nice.

This is an example of an astronomical image where the mapped color works extremely well. Today's APOD succeeds admirably at bringing out the blue-hot fury of the central star, the delicate shape of the surrounding bubble which hasn't burst in spite of the violent stellar wind blasting it, and the murky dusty orangish nebula surrounding NGC 7635, which has been partly lit up by the ultraviolet onslaught of the O-type star.

My personal favorite link of today's APOD was the one about the central star itself. Here we could read that the central star is of spectral class O6.5IIIf, but we could also read that the star appeared to be considerably cooler (by some 6,000 degrees Kelvin) than exptected for its spectral class. Specifically, the link pointed out that the literature expected this star to be hotter than it actually seemed to be when its temperature was carefully measured.

Because I'm such an O-star fan, I have read several papers about O stars in recent years, and they almost all seem to agree that O stars are usually a bit fainter than "the literature" expected them to be. My personal gut feeling is that the O stars have been somewhat overestimated.

Is there a reason why the O stars may have been overestimated? I think so. Back when astronomers really started classifying stars and describing their properties, the O stars, which are all quite far away, hadn't had their distances well measured. On the other hand, astrophotography was a powerful tool of early astronomy, and blue and ultraviolet stars stood out all out of proportion of their "visual" brightness due to the properties of the old photographic plates which were used by astrophotography back in those days - these photographic plates reacted almost exclusively to blue and ultraviolet light! In one of my books on astronomy there is a photo of Orion taken with one of those photographic plates. All the blue stars of Orion look really bright, but Betelgeuse, the red star, has almost disappeared!

This is a photo of the Andromeda galaxy, taken with one of those old blue-sensitive photographic plates. You can see that the mighty yellow bulge of M31 looks smaller and fainter than expected. The photographic plate has only recorded the blue light emitted by the red and yellow stars of Andromeda's bulge.

A picture of the Andromeda Galaxy taken by film that isn't very blue-sensitive is more likely to look something like this. And here is a sketch of what Andromeda looks like visually in the telescope.

But to return to today's APOD, it is a very beautiful and inspiring image! Let me end by sort-of-quoting (from memory, that is) something that was said by great astrophotographer David Malin. "Cosmic bubbles" are relatively common in small starforming galaxies, he said, but they are unusual in the Milky Way. The reason is that the gas and dust, from which the new stars form, is both "more turbulent and more constrained" in a large galaxy like the Milky Way than in much smaller galaxies.

But, said David Malin, we do have one great bubble nebula...the Bubble Nebula!

And today's APOD is a great image of that great bubble nebula!

Ann

Ah the irresistible force met the immovable object!

Today's APOD truly was magnificent! Colorfully the coolest bubble picture displayed! I also liked the immovable object link. Can you imagine the pie you could make out of this pumpkin. You could see how Peter could keep his wife in this one.

Great photo of a fascinating object!!

Some great fundamental shapes in today's APOD. The cloud, not quite a shape, but an anti-shape, prevalent now in computing. And the bubble, my favorite, whose occurrence is all pervasive, macro and micro. The universe: a bubble, galactic cores: bubbles, gas giants: bubbles (crunchy on the inside) cells: bubbles, atoms: bubbles. There was even a real estate bubble (which popped, R.I.P.) Hey, who needs string theory? Bubble logic rocks!

Thanks Larry.

So, are all those stars in front of it? or behind it? Is that cloud totally blanking out the background, or are we seeing through it, and some of those stars are behind it? I have often wondered. Great Pic. I don't get that great a shot of it from my drive way. But then I don't do a very long exposure either.

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WOW ! just imagine inserting the solar system in that image ! probably not even a pixel at about 1000 light minutes across.( rough guessing on that number )

Boomer12k wrote:So, are all those stars in front of it? or behind it? Is that cloud totally blanking out the background, or are we seeing through it, and some of those stars are behind it? I have often wondered. Great Pic. I don't get that great a shot of it from my drive way. But then I don't do a very long exposure either.

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Most stars in the picture are likely in front of the Bubble Nebula, at least the bright-looking stars.

According to Wikipedia, the distance to NGC 7635 (the Bubble Nebula) is between 7,100 to 11,000 light-years. That's fairly far away. By contrast, the bright bluish star at about 7 o'clock in today's APOD, HD 220057, is an uncertain 1660 light-years away. That's far away too, but clearly not as far away as the Bubble Nebula. The pinkish star at 11 o'clock, SAO 20581, is fainter and hasn't had its distance well measured. It could, however, also be far away, but likely not as far away as the Bubble Nebula. How do we know? There are a couple of clues. Note that neither bluish HD 220057 nor pinkish SAO 20581 appear to light up the dusty nebula. If these stars were involved with the nebulosity, they'd undoubtedly light it up. Another clue is that these two stars aren't strikingly reddened. If they had been at the distance of the nebula, there would likely have been quite a lot of dust between us and these stars, and they would have appeared significantly reddened. That doesn't appear to be the case, judging form the stars' spectral classes and color indexes.

By comparison, the star that is the casue of all the action here, BD+602522, is a star of spectral class O6.5IIIf, and its intrinsic color index may be close to -0.3. The color index that we measure for this star is 0.334, so it has lost 0.6 magnitudes more of its blue light than of its yellow-green light. This means that the star is relatively reddened. HD 220057 is classified as a B2 star, though some sources classify it as B5. Its intrinsic color index is likely somewhere between 0.28 and 0.15, whereas its measured color index is 0.033. It has lost between 0.2 and 0.3 magnitudes more of its blue light than of its yellow-green light.

There are, however, some very red stars here, and a few of them look as if they just might be lighting up some dust. They could be at the same distance as the nebula.

You may compare today's APOD with this RGB image of NGC 7635. Since it is an RGB image, it will show off reflection nebulosity quite well, so that we can see quite clearly if any of the brighter stars is lighting up the nebula. It doesn't look that way to me.

Ann

Hi i am new to this
i don't mind if 100 people answer
I am 79 years old, had to stop and think on that one

i know nothing about stars or planets.
tell me where and how to start
but for now answer my BIG question.
i keep seeing planets in color
are the planets in color?
and will i always see them in that color?
or is that just an artist's depiction?
thanks
Don barnes118@centurytel.net

donaldbarnes wrote:
i keep seeing planets in color
are the planets in color?
and will i always see them in that color?
or is that just an artist's depiction?
thanks
Don barnes118@centurytel.net

Hi Don,

The planets do have color but (except in the case of wet Earth & rusty Mars)
the natural colors are sometimes quite subdued:

https://planetariumweb.madison.k12.wi.u ... s-true.htm

Here are some natural color planetary examples at APOD:

http://apod.nasa.gov/apod/ap071023.html
http://apod.nasa.gov/apod/ap060322.html
http://apod.nasa.gov/apod/ap040723.html
http://apod.nasa.gov/apod/ap051114.html

neufer wrote:

donaldbarnes wrote:
i keep seeing planets in color
are the planets in color?
and will i always see them in that color?
or is that just an artist's depiction?
thanks
Don barnes118@centurytel.net

Hi Don,

The planets do have color but (except in the case of wet Earth & rusty Mars)
the natural colors are sometimes quite subdued:

https://planetariumweb.madison.k12.wi.u ... s-true.htm

Art, I question that first link of yours, which shows Uranus and Neptune as all but perfectly identical in color. This is the first time ever that I have been shown color pictures of these two planets where their color can't be told apart by a casual observer.

Who is the person making this claim about the color of Uranus and Neptune? What criteria has he used when arriving at his conclusion?

Ann

They are not identical in color on my screen, and both are Hubble images.

This is the original Hubble source of the images of Uranus and Neptune which, to me at least, look so extremely similar in color (although not identical).

However, http://en.wikipedia.org/wiki/Neptune does not agree that Uranus and Neptune are nearly identical in color:

At high altitudes, Neptune's atmosphere is 80% hydrogen and 19% helium.[17] A trace amount of methane is also present. Prominent absorption bands of methane occur at wavelengths above 600 nm, in the red and infrared portion of the spectrum. As with Uranus, this absorption of red light by the atmospheric methane is part of what gives Neptune its blue hue,[49] although Neptune's vivid azure differs from Uranus's milder cyan. Since Neptune's atmospheric methane content is similar to that of Uranus, some unknown atmospheric constituent is thought to contribute to Neptune's colour.

Ann

I'm reminded of the mobile of the solar system my son had in his room when he was very small; the colors of Neptune and Uranus were very close to how the Hubble images appear on my monitor.

It's a superb image.

I have just looked at this APOD and currently at least the "Cassiopeia" link is dead and the "pictured above" brings up the APOD of October 12 2011. I thought I would mention those in case the APOD editors were unaware.

Ann wrote:
This is the original Hubble source of the images of Uranus and Neptune which, to me at least, look so extremely similar in color (although not identical). However, http://en.wikipedia.org/wiki/Neptune does not agree that Uranus and Neptune are nearly identical in color:

At high altitudes, Neptune's atmosphere is 80% hydrogen and 19% helium.[17] A trace amount of methane is also present. Prominent absorption bands of methane occur at wavelengths above 600 nm, in the red and infrared portion of the spectrum. As with Uranus, this absorption of red light by the atmospheric methane is part of what gives Neptune its blue hue,[49] although Neptune's vivid azure differs from Uranus's milder cyan. Since Neptune's atmospheric methane content is similar to that of Uranus, some unknown atmospheric constituent is thought to contribute to Neptune's colour.

http://earthobservatory.nasa.gov/IOTD/view.php?id=76115 wrote:

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[b][color=#00BF20]Microcystis aeruginosa is a species of freshwater cyanobacteria[/color][/b]

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<<The brilliant streaks of blue and green that color the Great Lakes in this image are a contradiction. The blue in Lake Michigan and Lake Huron is sediment brought to the surface when strong winds churned the lakes. The green in Lake Erie and in Lake Huron’s Saginaw Bay is algae, which builds on the surface when winds are calm.

Sediment most often colors the Great Lakes in the spring and fall when transitioning weather patterns bring storms and strong winds. The winds stir the water, pulling quartz sand and silt from the lake bottom to the surface, says Richard Stumpf, an oceanographer with the National Oceanic and Atmospheric Administration. The white sand looks milky blue when viewed through the water from space. It is a good tracer, says Stumpf, illustrating how circulation in the lake moves material from the banks to the center.

The Moderate Resolution Imaging Spectroradiometer (MODIS) on the Aqua satellite took this image on October 9, 2011, a little more than a week after a persistent mid-latitude cyclone moved out of the region. The storm brought strong winds to the Great Lakes region, and the resulting sediment first became visible on October 1 as the storm clouds started to move away.

Some of the pale blue in Lake Erie may be sediment, but the green is an extremely large algal bloom. The algae may have initially spread across the western side of the lake because of windy weather, but calm weather and warm temperatures after the storm allowed green scum to build on the surface, says Colleen Mouw, a researcher at the University of Wisconsin-Madison. The bloom now covers much of the western half of the lake. “This is considered the worst bloom in decades,” says Stumpf. The green in Saginaw Bay is probably an algal bloom as well.

Though satellite imagery cannot tell us what type of algae is growing, direct measurements of the water show that the bloom in Lake Erie is mostly microcystis aeruginosa, a toxic algae. Stumpf, whose research group monitors blooms in Lake Erie, measured extremely high concentrations (1,000 micrograms per liter) of microcystin in Lake Erie during the summer. Microcystis aeruginosa produces microcystin, a liver toxin that harms fish and other animals.

The display of color isn’t limited to the lakes. Touched by autumn, the forests around the lakes have turned orange.>>

What an image!
I'm a novice, a new entry here, and in my opinion APOD is the best site on the WEB.
Plenty of links and fantastic images, I love it!