Starship Asterisk*

Ann wrote: ↑Wed Sep 28, 2022 3:20 pm

beryllium732 wrote: ↑Wed Sep 28, 2022 10:16 am

Ann wrote: ↑Wed Sep 28, 2022 5:46 am Wow, that's a stunning image!

However, me being me, I do have one nitpick. To show you, I have added some extra annotation to the already richly annotated APOD, to bring out the Pipe Nebula. And near the Pipe Nebula is one of my favorite stars, Theta Ophiuchi, whose lovely azure light is not given full justice in the APOD. Wait, I'll show you!

Click to view full size image

A furious sky over Mount Shasta. Image: Ralf Rohner.

The Pipe Nebula and blue star Theta Ophiuchi. Credit and copyright: Jose Mtanos.

---

Can you see the Pipe Nebula at left in the APOD, which I have marked in light brown? And can you see θ Oph, Theta Ophiuchi, very close to it? It hardly looks blue at all in the APOD.

But Theta Ophiuchi really is a lovely blue star, as you can see in Jose Mtanos' image. Few stars in the sky have a bluer B-V index. The B-V index measures the proportion of blue light to the proportion of yellow-green light emitted by a star (or a galaxy), and the lower the B-V index is, the bluer is the star (or the galaxy).

The fact that Theta Ophiuchi has an unusually blue B-V index is certainly not to say that Theta Ophiuchi is the intrinsically bluest and hottest star in the heavens, even though it is hot. Simbad Astronomical database calls it an OB star of the Beta Cephei type, which probably means it is of early spectral class B. But it is less affected by dust reddening than most O and early B stars in the sky and thus looks bluer than most stars to our eyes.

The only star in Ralf Rohner's superb image that has a bluer B-V index than Theta Ophiuchi is Shaula, Lambda Scorpii, which can be seen in the lower left corner in Rohner's image. Interestingly, Shaula is a Beta Cephei star, too.


So what about the original Beta Cephei star, Beta Cephei itself? Sure, it is a hot and blue star and it stands out - not strikingly so, but it does - in its own constellation.


Beta Cep and constellation Cepheus Will Gater.png


And of course, the Cepheus constellation also contains one of the redder stars in the sky that is visible to the naked eye, Mu Cephei, also known as the Garnet Star. It is an extremely swollen, cool and luminous star. Antares, you are so out-reddened and out-sized by Mu Cephei!

But I can feel that I'm veering off the topic of today's APOD, so I'm leaving here!

Ann

The dust on the left in the first picture is it part of one of the spiral arms and which one?

I think you are asking if the Pipe Nebula is part of one of our galaxy's major spiral arms. I'd say no.


APOD 28 September 2022 extra annotated cropped.png


Take a look at the Pipe Nebula at left in this cropped and extra annotated version of the APOD. Note that the Pipe Nebula seems to be connected to long streamers of gas and dust that reach all the way into the colorful Antares and Rho Ophiuchi region. The stars of the Antares/Rho Ophiuchi region are located at a distance of some ~500 light-years, and I'd say that the dark dusty streamers, as well as the Pipe Nebula, are at a similar distance.

But take a look at the long dark dust lane to the left of the Pipe Nebula that is interspersed with red emission nebulas and peppered with small white stars. I think - think, mind you - that the dust lane here is part of the Sagittarius Arm, which is one of our galaxy's major spiral arms. The distance to the Sagittarius Arm is some ~4000 light-years.

Ann

bystander wrote: ↑Wed Sep 28, 2022 10:26 pm

johnnydeep wrote: ↑Wed Sep 28, 2022 9:39 pm Alright, with a lot of pain, I managed to find a link to the annotated image from my browser (by viewing the html source for the page):

https://apod.nasa.gov/apod/image/2209/S ... otated.jpg

In contrast, the original unannotated image is:

https://apod.nasa.gov/apod/image/2209/S ... r_1640.jpg

So it's not a matter of simply appending "_annotated" before the .jpg.

Everyone else seems to have had a much easier time finding it. I swear I figured out the trick long ago, but must have forgotten.

Actually, the image you first see at https://apod.nasa.gov/apod/ap220928.html is:

https://apod.nasa.gov/apod/image/2209/S ... er_960.jpg

So it is just a matter of simply appending "_annotated" before the .jpg.

johnnydeep wrote: ↑Wed Sep 28, 2022 9:39 pm Alright, with a lot of pain, I managed to find a link to the annotated image from my browser (by viewing the html source for the page):

https://apod.nasa.gov/apod/image/2209/S ... otated.jpg

In contrast, the original unannotated image is:

https://apod.nasa.gov/apod/image/2209/S ... r_1640.jpg

So it's not a matter of simply appending "_annotated" before the .jpg.

Everyone else seems to have had a much easier time finding it. I swear I figured out the trick long ago, but must have forgotten.

beryllium732 wrote: ↑Wed Sep 28, 2022 10:16 am

Ann wrote: ↑Wed Sep 28, 2022 5:46 am Wow, that's a stunning image!

However, me being me, I do have one nitpick. To show you, I have added some extra annotation to the already richly annotated APOD, to bring out the Pipe Nebula. And near the Pipe Nebula is one of my favorite stars, Theta Ophiuchi, whose lovely azure light is not given full justice in the APOD. Wait, I'll show you!

Click to view full size image

A furious sky over Mount Shasta. Image: Ralf Rohner.

The Pipe Nebula and blue star Theta Ophiuchi. Credit and copyright: Jose Mtanos.

---

Can you see the Pipe Nebula at left in the APOD, which I have marked in light brown? And can you see θ Oph, Theta Ophiuchi, very close to it? It hardly looks blue at all in the APOD.

But Theta Ophiuchi really is a lovely blue star, as you can see in Jose Mtanos' image. Few stars in the sky have a bluer B-V index. The B-V index measures the proportion of blue light to the proportion of yellow-green light emitted by a star (or a galaxy), and the lower the B-V index is, the bluer is the star (or the galaxy).

The fact that Theta Ophiuchi has an unusually blue B-V index is certainly not to say that Theta Ophiuchi is the intrinsically bluest and hottest star in the heavens, even though it is hot. Simbad Astronomical database calls it an OB star of the Beta Cephei type, which probably means it is of early spectral class B. But it is less affected by dust reddening than most O and early B stars in the sky and thus looks bluer than most stars to our eyes.

The only star in Ralf Rohner's superb image that has a bluer B-V index than Theta Ophiuchi is Shaula, Lambda Scorpii, which can be seen in the lower left corner in Rohner's image. Interestingly, Shaula is a Beta Cephei star, too.


So what about the original Beta Cephei star, Beta Cephei itself? Sure, it is a hot and blue star and it stands out - not strikingly so, but it does - in its own constellation.


Beta Cep and constellation Cepheus Will Gater.png


And of course, the Cepheus constellation also contains one of the redder stars in the sky that is visible to the naked eye, Mu Cephei, also known as the Garnet Star. It is an extremely swollen, cool and luminous star. Antares, you are so out-reddened and out-sized by Mu Cephei!

But I can feel that I'm veering off the topic of today's APOD, so I'm leaving here!

Ann

The dust on the left in the first picture is it part of one of the spiral arms and which one?

Ann wrote: ↑Wed Sep 28, 2022 5:46 am Wow, that's a stunning image!

However, me being me, I do have one nitpick. To show you, I have added some extra annotation to the already richly annotated APOD, to bring out the Pipe Nebula. And near the Pipe Nebula is one of my favorite stars, Theta Ophiuchi, whose lovely azure light is not given full justice in the APOD. Wait, I'll show you!

APOD 28 September 2022 extra annotated.png

A furious sky over Mount Shasta. Image: Ralf Rohner.

The Pipe Nebula and blue star Theta Ophiuchi. Credit and copyright: Jose Mtanos.

---

Can you see the Pipe Nebula at left in the APOD, which I have marked in light brown? And can you see θ Oph, Theta Ophiuchi, very close to it? It hardly looks blue at all in the APOD.

But Theta Ophiuchi really is a lovely blue star, as you can see in Jose Mtanos' image. Few stars in the sky have a bluer B-V index. The B-V index measures the proportion of blue light to the proportion of yellow-green light emitted by a star (or a galaxy), and the lower the B-V index is, the bluer is the star (or the galaxy).

The fact that Theta Ophiuchi has an unusually blue B-V index is certainly not to say that Theta Ophiuchi is the intrinsically bluest and hottest star in the heavens, even though it is hot. Simbad Astronomical database calls it an OB star of the Beta Cephei type, which probably means it is of early spectral class B. But it is less affected by dust reddening than most O and early B stars in the sky and thus looks bluer than most stars to our eyes.

The only star in Ralf Rohner's superb image that has a bluer B-V index than Theta Ophiuchi is Shaula, Lambda Scorpii, which can be seen in the lower left corner in Rohner's image. Interestingly, Shaula is a Beta Cephei star, too.


So what about the original Beta Cephei star, Beta Cephei itself? Sure, it is a hot and blue star and it stands out - not strikingly so, but it does - in its own constellation.


Beta Cep and constellation Cepheus Will Gater.png


And of course, the Cepheus constellation also contains one of the redder stars in the sky that is visible to the naked eye, Mu Cephei, also known as the Garnet Star. It is an extremely swollen, cool and luminous star. Antares, you are so out-reddened and out-sized by Mu Cephei!

But I can feel that I'm veering off the topic of today's APOD, so I'm leaving here!

Ann