APOD: From the Pleiades to the Eridanus Loop (2020 Mar 23)

Comments and questions about the APOD on the main view screen.
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APOD: From the Pleiades to the Eridanus Loop (2020 Mar 23)

Post by APOD Robot » Mon Mar 23, 2020 4:05 am

Image From the Pleiades to the Eridanus Loop

Explanation: If you stare at an interesting patch of sky long enough, will it look different? In the case of Pleiades and Hyades star clusters -- and surrounding regions -- the answer is: yes, pretty different. Long duration camera exposures reveal an intricate network of interwoven interstellar dust and gas that was previously invisible not only to the eye but to lower exposure images. In the featured wide and deep mosaic, the dust stands out spectacularly, with the familiar Pleaides star cluster visible as the blue patch near the top of the image. Blue is the color of the Pleiades' most massive stars, whose distinctive light reflects from nearby fine dust. On the upper left is the Hyades star cluster surrounding the bright, orange, foreground-star Aldebaran. Red glowing emission nebula highlight the bottom of the image, including the curving vertical red ribbon known as the Eridanus Loop. The pervasive dust clouds appear typically in light brown and are dotted with unrelated stars.

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Absolutecolor

Re: APOD: From the Pleiades to the Eridanus Loop (2020 Mar 23)

Post by Absolutecolor » Mon Mar 23, 2020 5:34 am

Hi,
very beautiful picture

I have a question: what is the pinkish line that crosses the image almost orizontally at around 2/9 of the height?

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Joe Stieber
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Re: APOD: From the Pleiades to the Eridanus Loop (2020 Mar 23)

Post by Joe Stieber » Mon Mar 23, 2020 6:03 am

Absolutecolor wrote:
Mon Mar 23, 2020 5:34 am
I have a question: what is the pinkish line that crosses the image almost horizontally at around 2/9 of the height?
Since it was taken from Shizuoka Prefecture, Japan, which is nominally 35°N latitude, and the line passes just below the star 17 Eri, which has a declination of 5°S, it's probably a geostationary satellite(s). The geostationary satellites are above the earth's equator, but parallax from a viewpoint at mid-northern latitudes makes them appear a bit south of the celestial equator. The camera was tracking the diurnal motion of the stars, so stationary satellites leave trails.

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Ann
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Re: APOD: From the Pleiades to the Eridanus Loop (2020 Mar 23)

Post by Ann » Mon Mar 23, 2020 6:13 am

Fascinating! I have heard of the Eridanus Loop, but I have never really known what it is or why it is there. The APOD, while fascinating, does not really explain "why" the Eridanus Loop is there. No signs of really massive and windy stars can be seen inside the Eridanus Loop, and the Loop doesn't really look like a supernova remnant.

So let's look at some pictures! :D
















So it would seem that the Eridanus Loop is a by-product of the fertile molecular clouds and the formation of massive stars and supernovas in the Orion region.

And maybe there was a supernova somewhere inside the Eridanus Loop some time in the past after all.

Ann
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Ann
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Re: APOD: From the Pleiades to the Eridanus Loop (2020 Mar 23)

Post by Ann » Mon Mar 23, 2020 7:13 am

Got to show you a cool thing, or a cool star, in today's APOD.

Beid Keid and Nu Eri.png
Nu Eridani (blue star at upper left) and
40 Eridani (yellow-white star at lower right).






















Start by looking at the bright blue star at upper left. That is Nu Eridani, probably the most massive star in today's APOD. Nu Eridani is classified as spectral class B2III SB, and Jim Kaler's estimate is that the mass of Nu Eri is 8.5 solar masses.

Yes, but the really interesting star in the picture is the brightest yellow-white star at lower right. It is a K1V star, a main sequence star fainter and cooler than the Sun, and it is one of the few stars intrinsically fainter than the Sun that you might see with the naked eye. It is a nearby star, obviously, only 16 light-years away.
The star is 40 Eridani, also known as Keid, meaning egg shells. The bluish star to the upper right of it is called Beid, the eggs. :ssmile:

Anyway, the Keid system is a multiple one, containing a white dwarf and a tiny red dwarf. The white dwarf is a remnant of a star massive enough to have run through not only its main sequence but also its giant stage life and stopped producing energy by fusion, leaving only a hot but cooling stellar core behind. My own guess is that 40 Eridani B might have been perhaps a late type A or an F-type star when it was on the main sequence.

By the way, the white dwarf of the 40 Eridani system has been shown to be more massive than 0.5 M⊕. According to this Astrobite, the mass of 40 Eridani B might be closer to 0.6 M⊕.

Ann
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Re: APOD: From the Pleiades to the Eridanus Loop (2020 Mar 23)

Post by orin stepanek » Mon Mar 23, 2020 11:07 am

Gotta love the Pleiades! 8-)
Orin

Smile today; tomorrow's another day!

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Re: APOD: From the Pleiades to the Eridanus Loop (2020 Mar 23)

Post by starsurfer » Mon Mar 23, 2020 3:09 pm

This is one of the greatest things I have ever seen! :shock:

The Eridanus Loop is also catalogued as Sh2-245.

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Re: APOD: From the Pleiades to the Eridanus Loop (2020 Mar 23)

Post by De58te » Mon Mar 23, 2020 5:34 pm

Ann's talk of 40 Eridani got me to think why does that name sound so familiar. Some science fiction writers may have used that in their story. Then the thought hit me. Mr. Spock's of Star Trek planet Vulcan is found there in the 40 Eridani system.