Astronomy C

[syo_astro]

I've been looking for information about Henize 2-248, which is on the official list. However, all I found was information about Henize 2-428. Are these DSOs equivalent?

Huh, didn't notice that...I'd recommend making a clarif on the soinc website. It's weird because in my draft I see it as Hen 2-428. If there is a problem the only way to get a proper answer if there was/wasn't a typo in the rules I think. But you sure you weren't misreading?

[Unome]

I've been looking for information about Henize 2-248, which is on the official list. However, all I found was information about Henize 2-428. Are these DSOs equivalent?

Huh, didn't notice that...I'd recommend making a clarif on the soinc website. It's weird because in my draft I see it as Hen 2-428. If there is a problem the only way to get a proper answer if there was/wasn't a typo in the rules I think. But you sure you weren't misreading?

I'm pretty sure that's actually what it says, since Karp made a note about it on the DSOs wiki a few days ago.

[jbauer999]

Sort of a noob here, but is there any places to find help to interpret light curves. some of them just don't seem to give enough information. Like if an exoplanet is transiting its host star. how do I go about calculating distance, magnitude. Is it mostly guess and check, or are there specific things to use? If needed to elaborate, I won't mind. Thank you in advance

[antoine_ego]

Sort of a noob here, but is there any places to find help to interpret light curves. some of them just don't seem to give enough information. Like if an exoplanet is transiting its host star. how do I go about calculating distance, magnitude. Is it mostly guess and check, or are there specific things to use? If needed to elaborate, I won't mind. Thank you in advance

In general, you would be using other information given in conjunction with the light curve. That being said, it really depends on the curve. Some curves give you a good amount of information, others, not so much. In my opinion, it isn't guess and check, it's more of looking at the information, and thinking "Oh I have the formula to calculate temperature, and I have the stuff I need to do that from the curve!" It's more just plug and chug. Occasionally there'll be a problem that requires a stroke of genius, but that isn't typically the case. Note: This year has nothing to do with exoplanets, the topic is Type 1a Supernovae and the ever-present Stellar Evolution.

[bearasauras]

I've been looking for information about Henize 2-248, which is on the official list. However, all I found was information about Henize 2-428. Are these DSOs equivalent?

It's probably a typo, especially since 2-428 is related to this year's topic. I'm pretty sure there isn't even a 2-248.

Thanks for catching that! A correction has been posted at https://www.soinc.org/official_rules_clarif.

[Unome]

Here's my question:



(a) What do the colored lines represent?
(b) Rank A, B, C, and D in terms of mass
(c) What is the x-coordinate of the point labeled 2015, in Kelvin?

Going to move my question to this thread: what is this?

Also, two unrelated questions:

1) How do I convert between luminosity and magnitude?
2) How do I use spectroscopic parallax?

[Magikarpmaster629]

Update on Henize 2-428: soinc.org added a clarification that it is indeed 2-428 and not 2-248 as it says in the rules.

1) How do I convert between luminosity and magnitude?
2) How do I use spectroscopic parallax?

1)
where L is luminosity in solar luminosities and M is absolute magnitude.
2) Spectroscopic parallax is basically an application of the distance modulus. More technically, it's where you use tables to find the luminosity of a star you know the spectral type of; then by finding the apparent magnitude you can use the distance modulus and find its distance. I haven't ever seen it used, but it could happen.

Now for my own question: is there a clean conversion between Julian and Gregorian date, or do I need a program for that?

[Unome]

Update on Henize 2-428: soinc.org added a clarification that it is indeed 2-428 and not 2-248 as it says in the rules.

1) How do I convert between luminosity and magnitude?
2) How do I use spectroscopic parallax?

1)
where L is luminosity in solar luminosities and M is absolute magnitude.
2) Spectroscopic parallax is basically an application of the distance modulus. More technically, it's where you use tables to find the luminosity of a star you know the spectral type of; then by finding the apparent magnitude you can use the distance modulus and find its distance. I haven't ever seen it used, but it could happen.

Now for my own question: is there a clean conversion between Julian and Gregorian date, or do I need a program for that?

Thanks.

For your question: I usually just count the number of centuries over and subtract the 400 multiples, then add (or subtract) this from the other one.

[Adi1008]

Here's my question:



(a) What do the colored lines represent?
(b) Rank A, B, C, and D in terms of mass
(c) What is the x-coordinate of the point labeled 2015, in Kelvin?

Going to move my question to this thread: what is this?
(...)

This is a plot of surface gravity (on the y axis) vs. temperature (on the x axis) of post AGB stars on their way to becoming the central star of a planetary nebula. The lines show different evolutionary tracks over time for post AGB stars of different masses.

More massive stars are (in general) hotter, which is why the more massive stars are on the left, and vice versa

By knowing the surface gravity, it also gives us properties like the radius (size) and luminosity.

You might be wondering what the g/(cm/s^2) stuff is. Initially, it may look like grams/(cm/s^2), but the argument of a logarithm should be dimensionless - that is, the units should cancel out in order for the logarithm to make sense. When it says "g", they don't mean g for "gram", they mean "g" for surface gravity, like g = -9.8 m/s^2 for Earth. It's hard to know that they're talking about that type of "g" though, but you can still figure it out. Since the argument of the logarithm has to be dimensionless, you know that whatever "g" is must have the same dimensions as "cm/s^2", which is just acceleration. Personally, when I see "g" and the units for acceleration, it's clear as to what it's trying to say. Additionally, log(g) is a common term in astronomy (I think, at least; Wikipedia says surface gravity is often expressed as log(g): https://www.wikiwand.com/en/Surface_gravity). You'l notice that's why plots have things like log(T_effective/K); the K is to get rid of the unit on the temperature.

Magikarpmaster asked about this in the question marathon thread too; I'll post some more stuff there too

[bhavjain]

Do Type II Cepheids have a longer period than Type I?