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11 votes

Why are type 1b and type 1c supernovae called type 1 rather than type 2; if they result from large exploding stars, rather than accreting dwarfs?

It is fundamentally a question of spectral lines. Type I supernovae have no hydrogen lines, and type II have strong hydrogen lines. Type 1b have strong helium lines and no hydrogen lines, and type 1c ...
Justin T's user avatar
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11 votes
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Are spectral subtypes a logarithmic scale, or a linear one?

Strictly speaking, neither. The types and sub-types are qualitatively defined in terms of spectral features (the presence or absence of various lines) and the relationship to photosphere temperature ...
James K's user avatar
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9 votes

Up to 384 minor planets (including Pluto) qualify as planets?

That actual IAU Resolution B5 adopted at the IAU General Assembly in 2006 states: (1) A planet is a celestial body that: (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity ...
astrosnapper's user avatar
  • 8,357
8 votes

Sun's Stellar Class at Birth?

Spectral type is determined by (and is an indicator of) photospheric temperature and surface gravity. The classification of G2V applies to a star with a photospheric temperature of about 5800K and a ...
ProfRob's user avatar
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6 votes

Is the point of this paper to say that Pluto's status as a planet should have been handled scientifically, rather than by a vote?

Part of the problem here is semantics. The meaning of "planet" was really poorly defined prior to 2006 (and some argue that it still is). In the early 2000's, this started to become an issue. You ...
J.M. Haynes's user avatar
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5 votes
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Currently proposed ways to distinguish between a really big planet and a really small star

The dividing line between star and brown dwarf is the mass at which hydrogen fusion via the pp-chain occurs at its core. A brown dwarf below this mass limit will never reach a sustainable equilibrium ...
ProfRob's user avatar
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4 votes
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Classification and discovery of stars

Cepheid variable stars and exoplanets transiting stars have very different light curves (the relation between brightness and time). Exoplanet light curve from NASA: Cepheid variable light curve from ...
FJC's user avatar
  • 1,324
4 votes

Is the point of this paper to say that Pluto's status as a planet should have been handled scientifically, rather than by a vote?

To respond to the question as is: yes the paper is trying to point out that the concensus was not scientific. However, this claim is not true at all. In order to understand how classifications within ...
H.Aziz Kayıhan's user avatar
4 votes
Accepted

Musk's Roadster is now Russell's Teapot?

Small objects in space are hard to detect and characterise. Compare the tesla with another small solar system body: 2015TC25, It is currently about 0.3AU (3/10 of the distance from Earth to the sun) ...
James K's user avatar
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4 votes
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What abbreviations, letters, or symbols do we use to denote highly degenerate stars?

Neutron stars and black holes do not have assigned spectral types since they do not have a measurable optical/IR spectrum - which is the basis for assigning a spectral type. There are many ...
ProfRob's user avatar
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4 votes
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Where did the grand design spiral galaxy designation come from?

The term can be traced back to the theoretical work of C.C.Lin in explaining the spirals as due to density waves in galactic discs. A paper from 1970 discusses the "Existence of 'Grand Design'". Note ...
James K's user avatar
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4 votes
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Is the transition between ice giants and Jupiter-like gas giants somewhat fluid?

The distinction between gas giants and ice giants is a distinction that works nicely in our solar system. (And don't forget the distinction between the giant planets and the terrestrial planets, which ...
David Hammen's user avatar
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4 votes
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How many Kuiper Belt objects have moons? How do we know this?

"Moons" is a misnomer here, the majority of Kuiper Belt Objects (KBOs) with companions are binaries. Now there are several populations in the Kuiper Belt, characterized by their ...
AtmosphericPrisonEscape's user avatar
4 votes
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What does Sa and Sab mean for spiral galaxies?

Capitalization is critical here. (As is knowing which classification system is being used.) The traditional spiral stages (going back to Hubble) are Sa - Sb - Sc; this was a sequence from more ...
Peter Erwin's user avatar
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3 votes

Are there ways to determine a star's spectral type without the spectrum itself?

The color index of the star can give you that information. I can look it up for you if I know which exoplanet you're interested in, or you can find it in the NASA Exoplanet Database here.
AstroShannon's user avatar
3 votes

Can Jupiter's nightside be classified as spectral type Y?

According to this article: (https://iopscience.iop.org/article/10.3847/1538-4365/ac886a#:~:text=The%20visual%20and%20near%2Dinfrared,and%20ammonia%20(NH3).) "The visual and near-infrared (below 3....
Astrovis's user avatar
  • 695
3 votes

Is there a strict chronological order that determines the shape of galaxies?

Galaxies evolve from spiral to elliptical. The spirals are formed by patterns of new star formation in the disk surrounding the bulge, which contains mostly old stars. As galaxies run out of ...
James K's user avatar
  • 123k
3 votes

Currently proposed ways to distinguish between a really big planet and a really small star

Like in each of the other cases you mention, when dividing really big planets from really small stars you're drawing a bright line across a continuous range of objects. Whenever you do that, you're ...
Mark Olson's user avatar
  • 7,640
3 votes

Is the point of this paper to say that Pluto's status as a planet should have been handled scientifically, rather than by a vote?

If they wanted to make this paper about Pluto, why would they not just discuss Pluto? You may be right that the comment about voting could be linked to the Pluto debate, but I don't see any reason ...
FJC's user avatar
  • 1,324
3 votes

What is a dM1e red dwarf star? What do the '1' and 'e', specifically, stand for?

The 9 main spectral types (the classical OBAFGKM ones plus the more recent L and T ones for brown dwarfs) indicate the general features seen in the spectra and are in descending of temperature (O is ...
astrosnapper's user avatar
  • 8,357
2 votes

How accurate and complete is the Hubble sequence diagram?

The only way the Hubble sequence is truly incomplete is that it assumes such a classification applied to all stages of the universe. We now have telescopes that can see much further in space—and ...
HDE 226868's user avatar
  • 36.6k
2 votes

Is the point of this paper to say that Pluto's status as a planet should have been handled scientifically, rather than by a vote?

We suggest attempts to build consensus around planetary taxonomy not rely on the non-scientific process of voting, but rather through precedent set in scientific literature and discourse ... Good ...
David Hammen's user avatar
  • 34.1k
2 votes

Grammar of stellar classification

Normally, you would write G2V (with no spaces), as separating each part of the classification would cause some ambiguity. Basically, any star's classification would be written as 'Temperature class'+'...
WarpPrime's user avatar
  • 6,673
2 votes

Sun's Stellar Class at Birth?

It is true that on the main sequence, where most stars spend most of their lifetimes, mass is the main determining factor of all stellar parameters, with metallicity and angular momentum distant ...
AtmosphericPrisonEscape's user avatar
2 votes
Accepted

Dataset for machine learning MK stellar classification

That I know there is the XHIP catalog via VizieR and you can enter a range in UMag (or B- and V-band) for example of -20 .. 20. Check the box SpType and Tc to get ...
Michele Bianco's user avatar
2 votes

Elliptical galaxy classification

An E0 galaxy appears circular. That could be because it is spherical or it could be because it is an ellipsoid seen at an inclination angle where it appears circular. An E7 galaxy appears highly ...
ProfRob's user avatar
  • 153k
1 vote

Does "spectral type" and "stellar classification" refer to the same thing?

"Spectral Class" System of classification, including O, B, A, F, G, K, M. Stellar classification includes the Harvard system, and also other methods of classification including the Yerkes ...
Astrovis's user avatar
  • 695
1 vote
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Where do stellar classes names come from?

It seems like these letters are inherited from Draper classification system, which used letters to subdivide classes defined by Secchi. Secchi classification uses numbers I to V, while Draper did use ...
tuomas's user avatar
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