APOD: NGC 289: Swirl in the Southern Sky (2021 Oct 15)

[APOD Robot]

NGC 289: Swirl in the Southern Sky

Explanation: About 70 million light-years distant, gorgeous spiral galaxy NGC 289 is larger than our own Milky Way. Seen nearly face-on, its bright core and colorful central disk give way to remarkably faint, bluish spiral arms. The extensive arms sweep well over 100 thousand light-years from the galaxy's center. At the lower right in this sharp, telescopic galaxy portrait the main spiral arm seems to encounter a small, fuzzy elliptical companion galaxy interacting with enormous NGC 289. Of course spiky stars are in the foreground of the scene. They lie within the Milky Way toward the southern constellation Sculptor.

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[Ann]

Nice APOD! Let's compare Mike Selby's portrait of NGC 289 with Adam Block's:

NGC289Selby1024[1].jpg

NGC 289: Swirl in the Southern Sky. Image Credit & Copyright: Mike Selby

NGC 289: Swirl in the Southern Sky. Image Credit & Copyright: Adam Block, ChileScope

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As you can see, the color balance of the two images is different, with Mike Selby's a little redder and Adam Block's a little bluer. Personally, I think it's a little easier to see the nature of the star formation in the inner spiral arms in Adam Block's image, but maybe that's just me.

In my comment on Adam Block's image (which was also an APOD) I gushed over Adam's picture, and then I said:

It is interesting that NGC 289 is interacting with a small companion. Other notable spiral galaxies are also interacting with dwarf satellites, such as NGC 1512 (seen in the link in a photo from NASA/JPL-Caltech) and NGC 6872 (in a photo from NASA/ESA Hubble Space Telescope’s Wide Field Planetary Camera 2 (WFPC2)).

I think that a companion galaxy can help "wind up" the spiral structure of a spiral galaxy. The Whirlpool galaxy is the classic example.

As it happened, I talked about NGC 1512 but showed a link to NGC 1097 instead! Ooops!

Well, let's look at the galaxies instead:

NGC 1097 in infrared light. Red means cool dust and cyan means warmer stars. NGC 1097 contains dust and star formation, but its small companion (at left) is 'all blue' and non-starforming. Credit: NASA/JPL-Caltech/The SINGS Team (SSC/Caltech)

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NGC 1512 and its small companion NGC 1510 in an ultraviolet photo by NASA's Galaxy Evolution Explorer. The two galaxies are currently separated by a mere 68,000 light-years, leading many astronomers to suspect that a close encounter is currently in progress. NGC 1512's outer spiral arm is being distorted by strong gravitational interactions with NGC 1510. Credit: NASA/JPL-Caltech

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The classic example of a spiral galaxy being "wound up" by a companion is of course M51, the Whirlpool galaxy. But NGC 6872 may instead have been "unwound" and "stretched out" by its interactions with a companion, since the outstretched arms of this galaxy makes it (according to Wikipedia) 522,000 light-years long! Wowzers!

M51 being wound up by its companion. Credits: NASA, ESA, S. Beckwith (STScI) and the Hubble Heritage Team (STScI/AURA)

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NGC 6872 being unwound by its companion. Photo: ESO/VLT, Judy Schmidt (Geckzilla)

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Ann

[orin stepanek]

NGC289Selby1024.jpg

I like it; I'd call it the Cinnamon Roll Galaxy; cuz that is what it
reminds me of!

[neufer]

Hubble Space Telescope image of NGC 289

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<<NGC 289 is a spiral galaxy in the southern constellation of Sculptor, located at a distance of 76 megalight-years from the Milky Way. It was discovered on September 27, 1834 by John Herschel. The compiler of the New General Catalogue, John Louis Emil Dreyer noted that NGC 289 was "pretty bright, large, extended, between 2 considerably bright stars". The plane of the galaxy is inclined by an angle of 45° to the line of sight from the Earth.

This is a Type II Seyfert galaxy with an active galactic nucleus. A dust lane is seen crossing the nucleus, and there are indications of recent starburst activity nearby. NGC 289 is a giant, gas-rich, low surface brightness galaxy with a small bulge at the nucleus, a small central bar, and two inner spiral arms. These arms split into multiple parts as they extend into the outer disk. The galaxy has a dark matter halo that has an estimated 3.5 times the mass of the gaseous and stellar components. There is a dwarf elliptical companion to the north of the galaxy, designated Arp 1981, that may be having a perturbing influence.>>

Olivine basalt from the Moon, collected in 1971 by the crew of Apollo 15

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<<289 Nenetta is a typical A-type asteroid. It was discovered by Auguste Charlois on 10 March 1890 in Nice, France. The spectrum of 289 Nenetta reveals the strong presence of the mineral Olivine, a relative rarity in the asteroid belt. The mineral olivine is a magnesium iron silicate with the chemical formula (Mg²⁺, Fe²⁺)₂SiO₄. The primary component of the Earth's upper mantle, it is a common mineral in Earth's subsurface, but weathers quickly on the surface. For this reason, olivine has been proposed as a good candidate for accelerated weathering to sequester carbon dioxide from the Earth's oceans and atmosphere, as part of climate change mitigation.

Mg-rich olivine has also been discovered in meteorites, on the Moon and Mars, falling into infant stars, as well as on asteroid 25143 Itokawa. Such meteorites include chondrites, collections of debris from the early Solar System; and pallasites, mixes of iron-nickel and olivine. The rare A-type asteroids are suspected to have a surface dominated by olivine. The spectral signature of olivine has been seen in the dust disks around young stars. The tails of comets (which formed from the dust disk around the young Sun) often have the spectral signature of olivine, and the presence of olivine was verified in samples of a comet from the Stardust spacecraft in 2006. Comet-like (magnesium-rich) olivine has also been detected in the planetesimal belt around the star Beta Pictoris.>>