August 26, 2023 • 11 mins
Jordan and Kit discuss spectral types and the vital contributions of Annie Jump Cannon to this area of research.
Episode transcripts: https://www.starrytimepodcast.com/episode-transcripts Website: https://www.starrytimepodcast.com/ Social: https://universeodon.com/@starrytimepod Timestamps 00:00 Intro 00:52 Spectral Types 04:55 Annie Jump Cannon 08:17 Extended Spectral Types 11:01 Outro
Keywords/Topics Covered: Spectral Types, Annie Jump Cannon, Harvard Classification Scheme, Star Luminosity, Apparent Magnitude, Star Cataloging, OBAFGKM Classification, Red And Brown Dwarfs, Carbon Stars, Wolf-Rayet Stars, White Dwarfs, Astronomy History, Stellar Temperature, Wellesley College, Edward C. Pickering, Henry Draper, Women In Astronomy, Star Color, Stellar Classification
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Transcript
Episode Transcript
Available transcripts are automatically generated. Complete accuracy is not guaranteed.
>> Jordan (00:23):
Hi, I'm Jordan.
>> Kit (00:24):
And I'm Kit
>> Jordan (00:25):
Welcome to Starry Time
>> Kit (00:27):
Asterisms Edition,
>> Jordan (00:29):
where stars plus lines equals
stories
>> Kit (00:33):
with an asterisk.
>> Jordan (00:35):
In these episodes, we'll explore ideas, concepts,
or people that didn't make it into the show or that we
just want to talk about a little bit more. In today's episode,
we're going to focus on spectral types and
our mom's quote "college roommate,"
Annie Jump Cannon.
Alright, Kit. Why don't we just start off just
(00:55):
describing really broadly what's a spectral type
and how is this concept used in astronomy?
>> Kit (01:01):
Excellent. So there are a lot of ways astronomers
describe stars. One way is by
describing the luminosity, which is how much light is
emitted from the surface of the star. And that's measured
by total electromagnetic energy emmitted
per unit of time by a particular object or
star.
>> Jordan (01:19):
We discussed luminosity in more detail in our
episode eight on Leo.
And I remember for that episode that the Sun's
luminosity is
3.78 times 10 to
the 26th joules per second.
>> Kit (01:35):
An amazing memory.
>> Jordan (01:37):
I just recite the numbers to myself every day
when I wake up. And not like I would have cheated and
looked it up at all. No, no, no, nothing like that.
>> Kit (01:45):
No. Of course not just really,
um, stayed with you.
>> Jordan (01:50):
Committed.
>> Kit (01:50):
So we have luminosity. Next, there's apparent
magnitude, which is how bright something appears from
Earth. This is, of course, related to
luminosity, because how far away something is
determines how bright it seems to us. So something
that's dim but really close will seem really
bright. And something that's far away has to be
really, really bright for us to see it at all.
>> Jordan (02:11):
Exactly. And for some reason, this
scale is a reverse logarithmic
scale. So the lower the magnitude
again, the brighter the star is.
>> Kit (02:23):
And the reason for this really does just appear to
be tradition. Tradition.
>> Jordan (02:28):
Tradition.
>> Kit (02:31):
It seems like
originally magnitude was ranked
as the first is the brightest and the second brightest, and
so on. And then once we actually were able
to measure it more
quantitatively, they wanted to make
sure that the quantified number sort of
matched this 123 system. And so
(02:52):
it kind of ended up with this reverse logarithmic
scale allowed them to do that. But it's kind of
confusing.
>> Jordan (02:59):
Confusing? I don't find anything confusing about it at
all. But if you want to know more about apparent
magnitude versus absolute magnitude, you can
check out our episode seven on Cancer the
Crab.
>> Kit (03:12):
So, now, at long last, we've gotten to
today's topic, which is Spectral Types.
So luminosity tells us what kind of
wattage a star or other space object is
putting out. Apparent magnitude tells us how bright
it seems to us. And spectral types tell us about
the surface temperature and then relatedly what the color
of the star is. But how does it do
(03:34):
that? Well, it does that by
analyzing the electromagnetic radiation from a star
and how the light is absorbed in various ways, which is
determined by the chemical composition of the star.
>> Jordan (03:46):
So this idea of a spectral type, it
summarizes actually a lot of information about a
star beyond just how bright it is.
>> Kit (03:53):
Mhm.
>> Jordan (03:53):
Spectral types are usually classified with the
letters O, B, A, F,
G, K and M.
>> Kit (04:01):
The traditional mnemonic for memorization is
oh, be a fine girl or guy, kiss
me and I don't care for it.
>> Jordan (04:09):
Yeah, no, I prefer if we just said it
like it's written OBAFGKM
. So we'll workshop on it
maybe?
>> Kit (04:18):
Yeah, we can put it on the Retcon list.
>> Jordan (04:20):
These spectral types are associated with temperature,
where O types are hot blue, violet stars
and M, are very cool and red or orange
in color. And within each letter they rank
from 0 to 9, with those closer to
0 as hotter and those closer to 9 as cooler.
So our sun has a temperature of about
(04:40):
5,800 Kelvin. It
is yellow in color, and so it's classified
as a G2 star.
>> Kit (04:48):
In general, astronomers think type F, G
and K stars are the most likely to have habitable
planets around them.
So let's keep rolling. Now we have the big picture. Do
you want to tell us about the Harvard classification
scheme and Annie Jump Cannon, Jordan?
Of course, Annie Jump Cannon lived from
1863 to 1941, and
(05:09):
she was born in Delaware.
You don't hear people born in Delaware very often.
It's very small state.
>> Jordan (05:16):
And Annie Jump Cannon attended Wellesley
College in Massachusetts, where she studied physics,
astronomy, and graduated, of course, top
of her class.
>> Kit (05:25):
Mhm. At Wellesley College, she worked with Sarah Frances
Whiting, who was Wellesley's first professor of
physics, and, uh,
mentored and taught some other notable women
astronomers.
>> Jordan (05:37):
You love to see it. Wellesley long legacy
here. So what does Annie Jump Cannon have to do with spectral
types?
>> Kit (05:44):
Right to the heart of the matter. There is a lot
of great biographical information about Annie Jump Cannon out
there. And she actually had quite a long career in
astronomy. She's probably best known,
however, for working with Edward C. Pickering to work
on a star catalog funded by Henry Draper.
She was hired as a quote, computer along with other women. And in
(06:04):
this capacity, she manually cataloged over
350,000 stars.
>> Jordan (06:09):
That's an incredible amount of stars.
350,000. But all right, what does
cataloging involve though?
>> Kit (06:16):
So this is a good question. And my understanding is that during this
time period, men operated telescopes and took
pictures of stars. Which sounds fun.
And then these women computers,
including Annie Jump Cannon would look at the data,
do the astronomical calculations and
analyze the spectral patterns and then organize the data.
>> Jordan (06:36):
Less fun.
>> Kit (06:37):
No, not as much fun.
>> Jordan (06:40):
But she did this for
350,000
stars.
>> Kit (06:46):
Yeah. Incredible. She was really good at it.
And her biggest contribution as she was doing this
was the creation of this seven letter system that we
discussed earlier.
>> Jordan (06:56):
Which we all remember is O, B, A, F, G,
K, M. Before that system though, the
classification system was even more chaotic.
>> Kit (07:04):
Mhm.
>> Jordan (07:05):
Basically one of the earliest use of spectra to
organize star classifications was created
by Angelo Secchi, which
created five classes of stars. And
then it was followed by the original Draper system created
by Williamina Fleming, who was a colleague of
Annie's, which created a letter system of A through
Q relating to hydrogen lines in the
(07:26):
spectra. There was some alignment there that
overlaped with Secchi's work. But for example, stars
classified A or D were all type 1.
Another colleague of Annie's working at the same time,
Antonia Maury or Antonia Maury,
proposed yet another type of system. But
ultimately it was Annie Jump Cannon who
(07:47):
refined both of these into the simpler
system which became the Harvard classification
that is mostly the same as it is today.
>> Kit (07:55):
Yeah, and so some of the reason for this strange
ordering of letters is because of this collapsing and
refining of these other existent systems at the same
time.
>> Jordan (08:05):
Yeah, that makes sense.
>> Kit (08:06):
Since the development of the system, it's been
modified and extended in various ways, even though
this Harvard classification scheme, as you mentioned, is
pretty well intact. Um,
so to wrap up this little asterism, I just want to read out some of the
names, uh, and a little bit of information about these
extended spectral types and you can tell me which one you think
sounds best. What do you think?
>> Jordan (08:27):
Sounds awesome. Let's go. Hit me with the names.
>> Kit (08:30):
All right, let me uh, get my
document open here. I don't have them memorized,
so apologies to everyone.
>> Jordan (08:37):
So that's quite disappointing because I repeat
3.78 times 10 to the 26 joules
per second daily. Due to my
dedication to the pod, and you can't even remember a
few extended spectral types?
>> Kit (08:50):
So.
>> Jordan (08:51):
Says a lot about your commitment.
>> Kit (08:53):
So we now know about these cool red and
brown dwarfs, um, and these
have been added to the list of
spectral types so now we have class L, class
T and class Y stars. And these
are all um, cool red and brown dwarf
classes. We've got
(09:13):
peculiar brown dwarfs.
We have added class C which are
carbon stars, red giants that
are towards the end of their lives.
We've got S stars which are sort
of like between a carbon star and
an M star. We've got
also ah, class W
(09:37):
stars which are Wolf Rayet stars,
um, which are sort of hot and blue
stars. They used to be O stars and now they're
W stars. We've got but slash
stars which are O, slash
W or WN stars. We've got
magnetic, we've got a lot of them. Do you like
(09:58):
any of them? Did you see other ones that you really liked?
>> Jordan (10:01):
You haven't even mentioned my favorite which is the
white dwarf classification or the class D
which stands for degenerate star
which is the modern classification used for white dwarfs
which are low mass stars that are no longer undergoing
nuclear fusion and have shrunk to planetary
size slowly cooling down. So yeah,
(10:22):
there's a lot of great options here. Class S
the slash stars, the peculiar brown
dwarfs, but no the class D
degenerate white dwarfs.
>> Kit (10:32):
Yeah I also those one that's a great choice.
I liked all of the really like class L,
T and Y these sort of really
subtellar objects that are kind of interesting
and sort of hidden. We've talked about them before on the
pod with Teegarden's Star and those kinds of things.
So yeah there's, we're just sort of using the rest of the
alphabet and maybe one day we'll run out of alphabet.
(10:55):
Yeah, so definitely Let us know, take a look at the
extended spectral types and let us know what your favorites are.
>> Jordan (11:01):
Thank you for joining us today for this asterism
on spectral types and Annie Jump
Cannon.
>> Kit (11:08):
This has been Kit
>> Jordan (11:10):
and Jordan
>> Kit (11:12):
Sisters. Lovers of stars and stories.
>> Jordan (11:15):
And we'll see you next time
>> Kit (11:17):
on Starry Time.
Hi, I'm Jordan.
>> Kit (00:24):
And I'm Kit
>> Jordan (00:25):
Welcome to Starry Time
>> Kit (00:27):
Asterisms Edition,
>> Jordan (00:29):
where stars plus lines equals
stories
>> Kit (00:33):
with an asterisk.
>> Jordan (00:35):
In these episodes, we'll explore ideas, concepts,
or people that didn't make it into the show or that we
just want to talk about a little bit more. In today's episode,
we're going to focus on spectral types and
our mom's quote "college roommate,"
Annie Jump Cannon.
Alright, Kit. Why don't we just start off just
(00:55):
describing really broadly what's a spectral type
and how is this concept used in astronomy?
>> Kit (01:01):
Excellent. So there are a lot of ways astronomers
describe stars. One way is by
describing the luminosity, which is how much light is
emitted from the surface of the star. And that's measured
by total electromagnetic energy emmitted
per unit of time by a particular object or
star.
>> Jordan (01:19):
We discussed luminosity in more detail in our
episode eight on Leo.
And I remember for that episode that the Sun's
luminosity is
3.78 times 10 to
the 26th joules per second.
>> Kit (01:35):
An amazing memory.
>> Jordan (01:37):
I just recite the numbers to myself every day
when I wake up. And not like I would have cheated and
looked it up at all. No, no, no, nothing like that.
>> Kit (01:45):
No. Of course not just really,
um, stayed with you.
>> Jordan (01:50):
Committed.
>> Kit (01:50):
So we have luminosity. Next, there's apparent
magnitude, which is how bright something appears from
Earth. This is, of course, related to
luminosity, because how far away something is
determines how bright it seems to us. So something
that's dim but really close will seem really
bright. And something that's far away has to be
really, really bright for us to see it at all.
>> Jordan (02:11):
Exactly. And for some reason, this
scale is a reverse logarithmic
scale. So the lower the magnitude
again, the brighter the star is.
>> Kit (02:23):
And the reason for this really does just appear to
be tradition. Tradition.
>> Jordan (02:28):
Tradition.
>> Kit (02:31):
It seems like
originally magnitude was ranked
as the first is the brightest and the second brightest, and
so on. And then once we actually were able
to measure it more
quantitatively, they wanted to make
sure that the quantified number sort of
matched this 123 system. And so
(02:52):
it kind of ended up with this reverse logarithmic
scale allowed them to do that. But it's kind of
confusing.
>> Jordan (02:59):
Confusing? I don't find anything confusing about it at
all. But if you want to know more about apparent
magnitude versus absolute magnitude, you can
check out our episode seven on Cancer the
Crab.
>> Kit (03:12):
So, now, at long last, we've gotten to
today's topic, which is Spectral Types.
So luminosity tells us what kind of
wattage a star or other space object is
putting out. Apparent magnitude tells us how bright
it seems to us. And spectral types tell us about
the surface temperature and then relatedly what the color
of the star is. But how does it do
(03:34):
that? Well, it does that by
analyzing the electromagnetic radiation from a star
and how the light is absorbed in various ways, which is
determined by the chemical composition of the star.
>> Jordan (03:46):
So this idea of a spectral type, it
summarizes actually a lot of information about a
star beyond just how bright it is.
>> Kit (03:53):
Mhm.
>> Jordan (03:53):
Spectral types are usually classified with the
letters O, B, A, F,
G, K and M.
>> Kit (04:01):
The traditional mnemonic for memorization is
oh, be a fine girl or guy, kiss
me and I don't care for it.
>> Jordan (04:09):
Yeah, no, I prefer if we just said it
like it's written OBAFGKM
. So we'll workshop on it
maybe?
>> Kit (04:18):
Yeah, we can put it on the Retcon list.
>> Jordan (04:20):
These spectral types are associated with temperature,
where O types are hot blue, violet stars
and M, are very cool and red or orange
in color. And within each letter they rank
from 0 to 9, with those closer to
0 as hotter and those closer to 9 as cooler.
So our sun has a temperature of about
(04:40):
5,800 Kelvin. It
is yellow in color, and so it's classified
as a G2 star.
>> Kit (04:48):
In general, astronomers think type F, G
and K stars are the most likely to have habitable
planets around them.
So let's keep rolling. Now we have the big picture. Do
you want to tell us about the Harvard classification
scheme and Annie Jump Cannon, Jordan?
Of course, Annie Jump Cannon lived from
1863 to 1941, and
(05:09):
she was born in Delaware.
You don't hear people born in Delaware very often.
It's very small state.
>> Jordan (05:16):
And Annie Jump Cannon attended Wellesley
College in Massachusetts, where she studied physics,
astronomy, and graduated, of course, top
of her class.
>> Kit (05:25):
Mhm. At Wellesley College, she worked with Sarah Frances
Whiting, who was Wellesley's first professor of
physics, and, uh,
mentored and taught some other notable women
astronomers.
>> Jordan (05:37):
You love to see it. Wellesley long legacy
here. So what does Annie Jump Cannon have to do with spectral
types?
>> Kit (05:44):
Right to the heart of the matter. There is a lot
of great biographical information about Annie Jump Cannon out
there. And she actually had quite a long career in
astronomy. She's probably best known,
however, for working with Edward C. Pickering to work
on a star catalog funded by Henry Draper.
She was hired as a quote, computer along with other women. And in
(06:04):
this capacity, she manually cataloged over
350,000 stars.
>> Jordan (06:09):
That's an incredible amount of stars.
350,000. But all right, what does
cataloging involve though?
>> Kit (06:16):
So this is a good question. And my understanding is that during this
time period, men operated telescopes and took
pictures of stars. Which sounds fun.
And then these women computers,
including Annie Jump Cannon would look at the data,
do the astronomical calculations and
analyze the spectral patterns and then organize the data.
>> Jordan (06:36):
Less fun.
>> Kit (06:37):
No, not as much fun.
>> Jordan (06:40):
But she did this for
350,000
stars.
>> Kit (06:46):
Yeah. Incredible. She was really good at it.
And her biggest contribution as she was doing this
was the creation of this seven letter system that we
discussed earlier.
>> Jordan (06:56):
Which we all remember is O, B, A, F, G,
K, M. Before that system though, the
classification system was even more chaotic.
>> Kit (07:04):
Mhm.
>> Jordan (07:05):
Basically one of the earliest use of spectra to
organize star classifications was created
by Angelo Secchi, which
created five classes of stars. And
then it was followed by the original Draper system created
by Williamina Fleming, who was a colleague of
Annie's, which created a letter system of A through
Q relating to hydrogen lines in the
(07:26):
spectra. There was some alignment there that
overlaped with Secchi's work. But for example, stars
classified A or D were all type 1.
Another colleague of Annie's working at the same time,
Antonia Maury or Antonia Maury,
proposed yet another type of system. But
ultimately it was Annie Jump Cannon who
(07:47):
refined both of these into the simpler
system which became the Harvard classification
that is mostly the same as it is today.
>> Kit (07:55):
Yeah, and so some of the reason for this strange
ordering of letters is because of this collapsing and
refining of these other existent systems at the same
time.
>> Jordan (08:05):
Yeah, that makes sense.
>> Kit (08:06):
Since the development of the system, it's been
modified and extended in various ways, even though
this Harvard classification scheme, as you mentioned, is
pretty well intact. Um,
so to wrap up this little asterism, I just want to read out some of the
names, uh, and a little bit of information about these
extended spectral types and you can tell me which one you think
sounds best. What do you think?
>> Jordan (08:27):
Sounds awesome. Let's go. Hit me with the names.
>> Kit (08:30):
All right, let me uh, get my
document open here. I don't have them memorized,
so apologies to everyone.
>> Jordan (08:37):
So that's quite disappointing because I repeat
3.78 times 10 to the 26 joules
per second daily. Due to my
dedication to the pod, and you can't even remember a
few extended spectral types?
>> Kit (08:50):
So.
>> Jordan (08:51):
Says a lot about your commitment.
>> Kit (08:53):
So we now know about these cool red and
brown dwarfs, um, and these
have been added to the list of
spectral types so now we have class L, class
T and class Y stars. And these
are all um, cool red and brown dwarf
classes. We've got
(09:13):
peculiar brown dwarfs.
We have added class C which are
carbon stars, red giants that
are towards the end of their lives.
We've got S stars which are sort
of like between a carbon star and
an M star. We've got
also ah, class W
(09:37):
stars which are Wolf Rayet stars,
um, which are sort of hot and blue
stars. They used to be O stars and now they're
W stars. We've got but slash
stars which are O, slash
W or WN stars. We've got
magnetic, we've got a lot of them. Do you like
(09:58):
any of them? Did you see other ones that you really liked?
>> Jordan (10:01):
You haven't even mentioned my favorite which is the
white dwarf classification or the class D
which stands for degenerate star
which is the modern classification used for white dwarfs
which are low mass stars that are no longer undergoing
nuclear fusion and have shrunk to planetary
size slowly cooling down. So yeah,
(10:22):
there's a lot of great options here. Class S
the slash stars, the peculiar brown
dwarfs, but no the class D
degenerate white dwarfs.
>> Kit (10:32):
Yeah I also those one that's a great choice.
I liked all of the really like class L,
T and Y these sort of really
subtellar objects that are kind of interesting
and sort of hidden. We've talked about them before on the
pod with Teegarden's Star and those kinds of things.
So yeah there's, we're just sort of using the rest of the
alphabet and maybe one day we'll run out of alphabet.
(10:55):
Yeah, so definitely Let us know, take a look at the
extended spectral types and let us know what your favorites are.
>> Jordan (11:01):
Thank you for joining us today for this asterism
on spectral types and Annie Jump
Cannon.
>> Kit (11:08):
This has been Kit
>> Jordan (11:10):
and Jordan
>> Kit (11:12):
Sisters. Lovers of stars and stories.
>> Jordan (11:15):
And we'll see you next time
>> Kit (11:17):
on Starry Time.
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