Explanation: As far as the eye could see, it was a dark night at Las Campanas Observatory in the southern Atacama desert of Chile. But near local midnight on April 11, this mosaic of 3 minute long exposures revealed a green, unusually intense, atmospheric airglow stretching over thin clouds. Unlike aurorae powered by collisions with energetic charged particles and seen at high latitudes, the airglow is due to chemiluminescence, the production of light in a chemical reaction, and found around the globe. The chemical energy is provided by the Sun's extreme ultraviolet radiation. Like aurorae, the greenish hue of this airglow does originate at altitudes of 100 kilometers or so dominated by emission from excited oxygen atoms. The gegenschein, sunlight reflected by dust along the solar system's ecliptic plane was still visible on that night, a faint bluish cloud just right of picture center. At the far right, the Milky Way seems to rise from the mountain top perch of the Magellan telescopes. Left are the OGLE project and du Pont telescope domes.
Re: APOD: Airglow, Gegenschein, and Milky Way (2013 Apr 20)
Posted: Sat Apr 20, 2013 5:55 am
by Ann
Really fascinating. The sky looks almost like a Turner painting. As beautiful as it is, I find it mildly worrying, as if chemicals in the atmosphere are taking over the atmosphere, making it green above those orange clouds. If that green chemiluminescence is getting stronger and stronger, then perhaps the Earth will really begin to look green from space?
The clouds look strange too, as if the sky was on fire.
A faint wisp of a blue smudge - the Gegenschein? - can be seen near picture center around an intrinsically blue star, which I think is Spica.
A surprisingly bright white star(?) can be seen just to the left of the luminous band of the Milky Way. I think that "star" is Omega Centauri. And there is a fine cluster at far left. Is it the Beehive Cluster?
This skyscape is like a glorious painting and almost otherworldly. It's beautiful and strange.
Ann
Re: APOD: Airglow, Gegenschein, and Milky Way (2013 Apr 20)
Posted: Sat Apr 20, 2013 8:00 am
by geckzilla
Hopefully chemicals like oxygen which are responsible for this particular chemiluminescence stay in our atmosphere.
Re: APOD: Airglow, Gegenschein, and Milky Way (2013 Apr 20)
Posted: Sat Apr 20, 2013 10:31 am
by fausto.lubatti
It is a very inspiring picture!
Re: APOD: Airglow, Gegenschein, and Milky Way (2013 Apr 20)
Ogle, v. t. [From a Dutch word corresponding to G. äugeln to ogle, fr. auge eye; cf. D. ooglonken to ogle, OD. oogen to cast sheep's eyes upon, ooge eye.] To view or look at with side glances, as in fondness, or with a design to attract notice.
"And ogling all their audience, ere they speak." - Dryden.
<<The Optical Gravitational Lensing Experiment or OGLE is a Polish astronomical project based at the University of Warsaw that is chiefly concerned with discovering dark matter using the microlensing technique. Since the project began in 1992, it has discovered several extrasolar planets as a side benefit. The project is led by Professor Andrzej Udalski.
The main targets of the experiment are the Magellanic Clouds and the Galactic Bulge, because of the large number of intervening stars that can be used for microlensing during a stellar transit. Most of the observations have been made at the Las Campanas Observatory in Chile. Cooperating institutions include Princeton University and the Carnegie Institution.
The project is now in its fourth phase. The first phase, OGLE-I (1992–1995), was the project pilot phase; for OGLE-II (1996–2000), a telescope was specially constructed, placed in Las Campanas Observatory and dedicated to the project. The 8-chip mosaic CCD camera was built in Poland and shipped to Chile. OGLE-III (2001–2009) was primarily devoted to detecting gravitational microlensing events and transiting planets in four fields: the Galactic Bulge, the constellation Carina, and toward both Magellanic Clouds. As a byproduct of the constant monitoring of hundreds of millions of stars, the largest catalogs of variable stars were constructed, and the first exoplanets discovered using the microlensing technique were detected. In 2010, following engineering work in 2009, the fourth and current phase, OGLE-IV, was started using a 32-chip mosaic CCD camera. The main goal for this phase is to increase the number of planetary detections using microlensing, enabled by the new camera.
Seventeen planets have so far been discovered by the OGLE project. Eight of the planets were discovered by the transit method and six by the gravitational microlensing method.>>
William Makepeace Thackeray. (1811–1863). Vanity Fair. XXIV. The Old Piano
There are some splendid tailors’ shops in the High Street of Southampton, in the fine plate-glass windows of which hang gorgeous waistcoats of all sorts, of silk and velvet, and gold and crimson, and pictures of the last new fashions in which those wonderful gentlemen with quizzing glasses, and holding on to little boys with the exceeding large eyes and curly hair, ogle ladies in riding habits prancing by the Statue of Achilles at Apsley House.
Re: APOD: Airglow, Gegenschein, and Milky Way (2013 Apr 20)
Posted: Sat Apr 20, 2013 11:39 am
by Beyond
Gives a whole new meaning to Googleing.
Re: APOD: Airglow, Gegenschein, and Milky Way (2013 Apr 20)
Posted: Sat Apr 20, 2013 11:56 am
by neufer
Click to play embedded YouTube video.
Beyond wrote:
Gives a whole new meaning to Googleing.
Re: APOD: Airglow, Gegenschein, and Milky Way (2013 Apr 20)
Posted: Sat Apr 20, 2013 12:22 pm
by Spoonbender
Ann wrote:Really fascinating. The sky looks almost like a Turner painting. As beautiful as it is, I find it mildly worrying, as if chemicals in the atmosphere are taking over the atmosphere, making it green above those orange clouds. If that green chemiluminescence is getting stronger and stronger, then perhaps the Earth will really begin to look green from space?
The clouds look strange too, as if the sky was on fire.
A faint wisp of a blue smudge - the Gegenschein? - can be seen near picture center around an intrinsically blue star, which I think is Spica.
A surprisingly bright white star(?) can be seen just to the left of the luminous band of the Milky Way. I think that "star" is Omega Centauri. And there is a fine cluster at far left. Is it the Beehive Cluster?
This skyscape is like a glorious painting and almost otherworldly. It's beautiful and strange.
Ann
Is that a city in the distance on the lower left/mid of the picture?
Re: APOD: Airglow, Gegenschein, and Milky Way (2013 Apr 20)
Posted: Sat Apr 20, 2013 12:36 pm
by Boomer12k
The Southern Sky is always a bit confusing to me. Everything is, kind of Upside Down...But it is still an interesting picture of interesting phenomena, and the Milky Way.
What Chemicals are we talking here????
:---[===] *
Re: APOD: Airglow, Gegenschein, and Milky Way (2013 Apr 20)
Posted: Sat Apr 20, 2013 4:34 pm
by LocalColor
Beautiful, thank you Yuri Beletsky.
Re: APOD: Airglow, Gegenschein, and Milky Way (2013 Apr 20)
Posted: Sat Apr 20, 2013 7:12 pm
by Ann
Spoonbender wrote:
Is that a city in the distance on the lower left/mid of the picture?
I don't know, but I don't think so. The picture was taken in the Atacama desert of Chile. That's a very good place for large telescopes, but not for cities. And if there had been a city moderately nearby, I doubt that any large telescopes would have been built there.
To me, that bright yellow light looks almost like reflections on a clear calm lake or the ocean, but again I don't think so. I would guess that we are seeing a cloud bank of some sort, which might reflect the light of the (hidden) Moon.
Ann
Re: APOD: Airglow, Gegenschein, and Milky Way (2013 Apr 20)
Posted: Sat Apr 20, 2013 10:09 pm
by luigi
I like this panoramic view of the southern skies!
Can anyone help me with the position of the Gegenshein please? I previously thought it would be produced towards the North in the South hemisphere, here it is to the west... how do you calculate the position of the Gegenschein in the sky?
Ann: The white big star is Omega Centauri, you are right.
Reference: In this previous APOD from the same photographer and from the South Hemisphere it is towards North (see Andromeda low) http://apod.nasa.gov/apod/ap080507.html
Re: APOD: Airglow, Gegenschein, and Milky Way (2013 Apr 20)
Posted: Sat Apr 20, 2013 11:08 pm
by neufer
luigi wrote:
Can anyone help me with the position of the Gegenshein please? I previously thought it would be produced towards the North in the South hemisphere, here it is to the west... how do you calculate the position of the Gegenschein in the sky?
"Gegenschein is a faint brightening of the night sky in the region of the antisolar point."
Re: APOD: Airglow, Gegenschein, and Milky Way (2013 Apr 20)
Posted: Sun Apr 21, 2013 1:13 am
by luigi
neufer wrote:
luigi wrote:
Can anyone help me with the position of the Gegenshein please? I previously thought it would be produced towards the North in the South hemisphere, here it is to the west... how do you calculate the position of the Gegenschein in the sky?
"Gegenschein is a faint brightening of the night sky in the region of the antisolar point."
Thanks, then when do you find it North and when West? In this APOD it is on the west and in the other APOD I linked it's in the North.
Re: APOD: Airglow, Gegenschein, and Milky Way (2013 Apr 20)
Posted: Sun Apr 21, 2013 3:47 am
by alter-ego
Ann wrote:
Spoonbender wrote:
Is that a city in the distance on the lower left/mid of the picture?
I don't know, but I don't think so. The picture was taken in the Atacama desert of Chile. That's a very good place for large telescopes, but not for cities. And if there had been a city moderately nearby, I doubt that any large telescopes would have been built there.
To me, that bright yellow light looks almost like reflections on a clear calm lake or the ocean, but again I don't think so. I would guess that we are seeing a cloud bank of some sort, which might reflect the light of the (hidden) Moon.
Hi Ann,
I think Spoonbender is right. The yellow brightening on the horizon is at the same heading as Vallenar (population ~47000) which is ~50 kilometers distant. Although visible, the impact on viewing quality is negligible to nothing over the vast majority of the sky. Near-horizon viewing is typically avoided anyway. This is the nearest (an only sizeable) city that likely could be visible from the observatory.
Ann wrote:
... A faint wisp of a blue smudge - the Gegenschein? - can be seen near picture center around an intrinsically blue star, which I think is Spica.
A surprisingly bright white star(?) can be seen just to the left of the luminous band of the Milky Way. I think that "star" is Omega Centauri. And there is a fine cluster at far left. Is it the Beehive Cluster?
As luigi pointed out, you are right about Omega Cen. Yes, the star immersed in the Gegenschein is Spica, and as a bonus, the picture also shows Saturn to the lower right of Spica. It is the first whitish dot you encounter. Oh, and yes, you are correct about the Beehive.
Re: APOD: Airglow, Gegenschein, and Milky Way (2013 Apr 20)
Posted: Sun Apr 21, 2013 4:11 am
by alter-ego
neufer wrote:
luigi wrote:
Can anyone help me with the position of the Gegenshein please? I previously thought it would be produced towards the North in the South hemisphere, here it is to the west... how do you calculate the position of the Gegenschein in the sky?
"Gegenschein is a faint brightening of the night sky in the region of the antisolar point."
luigi-
In todays APOD, the Gegenschein is towards the northeast, not west. As Art pointed out it tracks the antisolar point. Just as the sun sweeps across the sky during the day, the antisolar point sweeps across the sky at night (in the same direction, but at the negative solar declination). With star charts, you can play around with this basic RA / Dec Gegenschein position calculator to see where the Gegenschein is in the sky.
Re: APOD: Airglow, Gegenschein, and Milky Way (2013 Apr 20)
Posted: Sun Apr 21, 2013 6:27 am
by luigi
alter-ego wrote:
neufer wrote:
luigi wrote:
Can anyone help me with the position of the Gegenshein please? I previously thought it would be produced towards the North in the South hemisphere, here it is to the west... how do you calculate the position of the Gegenschein in the sky?
"Gegenschein is a faint brightening of the night sky in the region of the antisolar point."
luigi-
In todays APOD, the Gegenschein is towards the northeast, not west. As Art pointed out it tracks the antisolar point. Just as the sun sweeps across the sky during the day, the antisolar point sweeps across the sky at night (in the same direction, but at the negative solar declination). With star charts, you can play around with this basic RA / Dec Gegenschein position calculator to see where the Gegenschein is in the sky.
Thank you very much for the calculator, that's what I needed. Now I know where to aim for the Gegenschein.
Re: APOD: Airglow, Gegenschein, and Milky Way (2013 Apr 20)
Posted: Sun Apr 21, 2013 8:56 am
by Ann
alter-ego wrote:
I think Spoonbender is right. The yellow brightening on the horizon is at the same heading as Vallenar (population ~47000) which is ~50 kilometers distant. Although visible, the impact on viewing quality is negligible to nothing over the vast majority of the sky. Near-horizon viewing is typically avoided anyway. This is the nearest (an only sizeable) city that likely could be visible from the observatory.
Yes, the star immersed in the Gegenschein is Spica, and as a bonus, the picture also shows Saturn to the lower right of Spica.
Thanks for explaining this, alter-ego!
Ann
Re: APOD: Airglow, Gegenschein, and Milky Way (2013 Apr 20)
Posted: Sun Apr 21, 2013 4:26 pm
by Peggy
Has anyone noticed that if you enlarge and zoom in on the upper left hand corner of the image, that there are at least 4 'cloned' sections of the image?
It looks like it has been Photoshopped.
Re: APOD: Airglow, Gegenschein, and Milky Way (2013 Apr 20)
Posted: Mon Apr 22, 2013 10:36 pm
by Anthony Barreiro
Ann wrote:Really fascinating. ... A faint wisp of a blue smudge - the Gegenschein? - can be seen near picture center around an intrinsically blue star, which I think is Spica.
A surprisingly bright white star(?) can be seen just to the left of the luminous band of the Milky Way. I think that "star" is Omega Centauri. And there is a fine cluster at far left. Is it the Beehive Cluster?
This skyscape is like a glorious painting and almost otherworldly. It's beautiful and strange.
Ann
Aha, so there is Leo, lying on his back hoping someone will rub his belly.
Airglow, Gegenschein, and Milky Way
