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48 votes

How did the Milky Way quasar not disrupt life on Earth?

An active galactic nucleus doesn't emit energy equally in all directions. It may form "jets", and if you are looking into the AGN at the right angle, and then nucleus is active enough, then ...
James K's user avatar
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29 votes
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Is the center of our galaxy, the Sagittarius A* black hole a former star?

We don't know. It's a supermassive black hole and there are several theories about their formation: The origin of supermassive black holes remains an open field of research. Astrophysicists agree ...
Glorfindel's user avatar
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17 votes

Is the center of our galaxy, the Sagittarius A* black hole a former star?

No. There is a maximum possible mass of a star - any larger and the star would blow itself apart because its radiation is stronger than its gravity. This is known as the Eddington limit. The ...
Allure's user avatar
  • 4,544
16 votes

How did the Milky Way quasar not disrupt life on Earth?

How much dangerous a quasar at Sag A* could be? A Fermi-inspired estimation: Assume it is 1000x the luminosity of the Milky way. This is rather at the high end (as per Wiki) and rounding out its ...
fraxinus's user avatar
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13 votes

Where is the barycenter of the Milky Way Galaxy?

Probably not, but only because the black hole is so small, compared to the galaxy. It is a bit hard to define the exact boundaries of the galaxy. Unlike the solar system, which is composed of a small ...
James K's user avatar
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13 votes

How did the Milky Way quasar not disrupt life on Earth?

I think the source of confusion here is that the two sources you mention implicitly have different definitions of what quasar is. Firstly, to our current understanding, quasars are not a well-defined ...
vvotan's user avatar
  • 290
9 votes

How did the Milky Way quasar not disrupt life on Earth?

A lot of answers here talking about jets, but that only applies to perhaps the very high energy (gamma ray) emission. Most of the luminous quasars we see are not seen via their jets but are extremely ...
ProfRob's user avatar
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7 votes

Are there any (rough) estimates of stars' orbits around the galaxy?

The "orbits" of stars around the galaxy are not closed Keplerian orbits (e.g. they are not confined to a plane), so they are not characterised in that fashion. What you can do is get the ...
ProfRob's user avatar
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7 votes
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How did the Milky Way quasar not disrupt life on Earth?

Quasars emit their energy along a pair of antipodal jets. Those jets have an angular width of no more than about 2.5 milliarcseconds, which is about $5.5\times 10^{-7}$ degrees, or $10^{-8}$ radians, ...
zibadawa timmy's user avatar
7 votes

Do we know at which angle the Event Horizon Telescope will look at the accretion disk of Sagittarius A*?

We don't know the answer to this (or if someone does, I'd really like to hear that answer). Our galaxy's Super-Massive Black Hole (SMBH) is an unusually quiet one, with little to no accretion disk. If ...
zephyr's user avatar
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7 votes
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What percentage of a spiral galaxy is the center/bulge?

The term you're looking for is called the bulge-to-disk (size) ratio. Sort of by definition, the answer depends on the morphology of the galaxy, i.e. how "late-type" spiral it is. "Sa" spirals are the ...
pela's user avatar
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6 votes

Why don't they make an image of the black hole in the M33 galaxy?

M87 was actually the easiest black hole for the Event Horizon Telescope (EHT) to attempt, and was thus sensibly its first target. For the EHT to work you need 1) an active BH accreting matter such ...
Tod R. Lauer's user avatar
6 votes

What percentage of a spiral galaxy is the center/bulge?

To answer the title question, what you want to know is the bulge-to-total ($B/T$) ratio, which is the fraction of a spiral galaxy's light (and thus, approximately, its stars) which in the bulge; this ...
Peter Erwin's user avatar
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6 votes

How did the Milky Way quasar not disrupt life on Earth?

You misinterpreted the article. the Milky Way recently (by cosmic standards) went through a quasar stage in its evolution. That does seem to indicate that the Milky Way turned into a quasar, but in ...
RonJohn's user avatar
  • 409
4 votes
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Drawing stars in a 3D space

You can't without knowing the distance to the star, $d$. Once you have that then, depending on exactly how the $x, y, z$ axes are defined: $$ \begin{align} x &= d \cos(b)\cos(l) \\ y &= d \cos(...
ProfRob's user avatar
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4 votes
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How much greater is the star density in our galactic bar?

In other barred galaxies which are vaguely similar to the Milky Way, the contrast in (projected) stellar surface density between the bar and the inter-bar region at the same radius (e.g., along the ...
Peter Erwin's user avatar
  • 16.7k
4 votes

What's the Right Ascension & Declination of Galactic Left & Galactic Right?

I think it makes sense to first think of the directions not in terms of equatorial coordinates (right ascension and declination) but in galactic coordinates (galactic latitude and galactic longitude, ...
HDE 226868's user avatar
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3 votes
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What coordinate system is at rest relative to the center of the galaxy?

Galactic coordinates are sun centred with a zero longitude chosen to align with the centre of the galaxy when the measurements were made in 1958. As defined, the galactic coordinates don't rotate, and ...
James K's user avatar
  • 122k
3 votes

How much greater is the star density in our galactic bar?

In the Milky Way, the density in the bar seems to roughly 5 times larger than "next to the bar". The most recent model of the Galactic bar I could find is Portail et al. (2017), whose model is ...
pela's user avatar
  • 38.3k
2 votes

Are there any (rough) estimates of stars' orbits around the galaxy?

For example, what are the orbital paramters (𝑎,𝑒,𝑖,Ω,𝜔,𝑀,𝑓) of Alpha Centauri? These are Keplerian orbital elements which characterize Keplerian orbits which are orbits in a strict $\mathbf{r}/...
uhoh's user avatar
  • 30.8k
2 votes

How do two supermassive black holes reach "the last parsec" in the case of merging galaxies?

There's a paper that gives exactly the formulae you are looking for by Sobolenko et al. (2021). They describe the merger of supermassive black holes as a three-phase process. These phases may overlap ...
ProfRob's user avatar
  • 152k
1 vote

How do I find stars within milky way using galactic latitude and longitude

Stars beyond our own galaxy and its immediate neighbors are indistinct without a large telescope, so I assume the question is about the band across the sky, rich with faint stars. The Milky Way's ...
Mike G's user avatar
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1 vote
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Do we know at which angle the Event Horizon Telescope will look at the accretion disk of Sagittarius A*?

After some research, I think this answers my question: The orientation of the disk seems not to be known with certainty, however, Meyer et al. (2007) gives estimates with $3\sigma$ confidence that "...
user3095304's user avatar
1 vote

What resolution is needed to see a quasar through the galactic center?

Whilst awaiting clarification, I'm going to assume that your question is asking about calibrating the reference frame within which the motions of stars at the Galactic centre are measured. The ...
ProfRob's user avatar
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