Thanks for sharing knowledge.

To say that “it is a nonsense question” is, to me, a nonsense response. I’ve heard it from so many people that I’m beginning to doubt my sanity. From what I gather, the professional physicist’s answer is based on the assumption that:

SPACE AND TIME EXIST ONLY IN THE UNIVERSE

This is said with such axiomatic certainty that you assume it must be a hard fact… until the physicist cheerfully admits that she doesn’t even know how many universes there are (there goes the definite article in the axiom) and whether or not the universe is finite or infinite (there goes the whole darn axiom, because you can’t have a definition that excludes nothing).

In other words, the question, “what is the universe expanding into” is being labelled nonsensical based on an axiom that is at best doughnut-shaped, and at worst, nonsensical.

The extent of physicists’ ignorance of the universe is most startlingly revealed when Pamela Gay says that she isn’t quite sure whether the doughnut shape is just a mathematical model or something that we could take literally! Jeez, isn’t that precisely the kind of question that’s at issue here? The right spatial model for the universe? Schrodinger should have asked, if there was an elephant in the room, what was the probability that a professional physicist could spot it?

Let’s just admit that there’s a cognitive aporia involved in trying to comprehend the extent of the universe. Let’s please not insult people’s intelligence by calling this a nonsense question.

Basically, the question doesn’t make sense.

I recommend you go check out the Astronomy Cast episode #28 “What is the universe expanding into?”

To quote Pamela Gay from the podcast, “So when we start thinking ‘what are we expanding into?’ We’re expanding into something beyond our ability to perceive because everything we perceive is trapped on this surface. “

“No, but an ant-eater has a field day snacking on them! ”

Please allow me to introduce my mom’s sister, Aunt Eeter.

Anyway, as others have mentioned, it’s all relative. Perhaps someone is the center of the universe from a strictly mathematical point of view. As observers, we’re all the center of our own universes because the vantage point comes from us.

A river of soldier ants can march where they will with impugnity. No one argues with them.

No, but an ant-eater has a field day snacking on them!

God hang those big stars there to test our faith in his creation!
I got it, I got it: Our planet is small, our sun is small therefore we aren’t the center of the Universe

The thing that mystifies me the most is how the universe is supposed to contain everything, and therefore – by definition – cannot have an “outside” – and yet, our brains can never actually conceptualize an entity that has no outside.

I mean, if the universe is constantly expanding (as the physicists say), what is it expanding into?

We are insignificant, at extremes of scale. The atoms and the galaxies are undoutbedly indifferent to our doings. However, it’s simplistic to write us off wholesale as irrelevant. Within a range of scales we can be, and are, key players. A river of soldier ants can march where they will with impugnity. No one argues with them.

See : http://blogs.discovermagazine.com/badastronomy/2009/02/18/wonder-twins-telescope-sees-stars-dying-gasps/

In a nutshell then; compared with the giants the supergiants & even larger hypergiants :

1) Fuse elements in their cores that go way beyond what the less massive giants can fuse – not just Helium into Carbon & Oxygen but also carbon & oxygen into silicon, sulphur, neon, magnesium, nitrogen, etc .. up until they start to fuse elements into iron ..

2) …At which point they can go supernova leaving behind neutron star and black holes unlike the giants which can only ever end as white dwarfs. Some less massive supergiants may still end up as white dwarfs – especially if they lose a lot of mass along the way as sometimes happens. Also note the time-scale is much shorter for supergiants evolving and dying than it is for ordinary stars and giants.

3) Are much more dramatic and extreme than the giants by almost any measure you care to name esp. mass, diameter and brightness. (Except for temperature, that’s the “exception that proves the rule!” )

4) Originate from rare high mass O and B main-sequence or dwarf stars rather than less massive A, F, & G, stars. (Stars from spectral classes G8 down live so long that they have not had time to evolve into giants.) (Kaler, 2002.)

5) Are very much rarer and younger than giants but, because they shine more brightly, can be seen from a lot vaster distances away too.

***

Now here’s a comparison of fifteen giants and supergiants :

If they replaced our Sun these giants would extend to where? :

1. Pollux – an orange giant, extends only an eighth of the way out to Mercury with just 10 times our Suns diameter. (Small giant & the nearest to us plus an exoplanet.)

2. Naos (Zeta Puppis) – a blue (type O) supergiant has a radius of 11 times solar and thus extends only a fraction more than an eighth of the way to Mercury.

3. Arcturus – an orange giant extends only a quarter of Mercury’s orbit diameter with 25 solar diameters.

4. Aldebaran – orange giant would extend halfway to Mercury’s orbit.

5. Canopus – yellow supergiant or bright giant (class F) with 65 times the Solar diameter would extends 75 % of the way to Mercury. (Second brightest star in our sky despite being 313 light years away – the nearest supergiant to us.)

6. Rigel – a blue supergiant (B class) also has about 65 times the Solar diameter also extending over two thirds the way to Mercury – but has much more mass 25 times the Suns mass versus Canopus with just 8 or 9 solar mass.

7. Menkar (Alpha Ceti) a red giant has a radius 77 times solar, about the size of Mercury’s orbit.

8. Zubenhakrabi (Sigma Librae a.k.a. Gamma Scorpii) – red giant has a radius 110 times that of the Sun (0.52 astronomical units), which would take the star about halfway between the orbits of Mercury and Venus.

9. Beta Pegasi or Scheat – a red giant with 95 solar radii would be filling 70 % of Venus’ orbit.

10. Gamma Crucis – a red giant with 113 times our solar diameter extends over halfway to Earth. (At 88 ly away, this is the closest red – M class – giant to us.)

11. Deneb – a white supergiant would extend out to about Earth’s orbit.

12. Enif – an orange supergiant has a diameter 150 times our Sun’s and would extend to around Earth’s orbit.

13. Mira (Omicron Ceti) – Red giant variable :

“..ranges from about 2 Astronomical Units (500 solar radii) at visual wavelengths to double that in the infrared, or from 20 percent bigger than the orbit of Mars to nearly half the size of the orbit of Jupiter.

14. Betelgeux – a red supergiant would extend into the middle of the asteroid belt between Mars and Jupiter with a radius of nearly 4 AU.

15. VV Cephei – a red hypergiant would extend out to 8 AU or 85% of the orbit of Saturn. (One of the largest of all stars.)

Sources :
Kaler, James B., ‘The 100 Greatest Stars’, Copernicus Books, 2002.
Kaler, James B., “Kaler’s Stars” website :
http://www.astro.uiuc.edu/~jkaler/sow/sowlist.html, accessed March & June (& constantly!) 2009.

& thanks to ‘SLC’ for asking the original question that turned into an article for me! Hope you actually got see my answer for you!

“Oh, so it’s “Ouranus” now, is it?

Actually its Ouranos but yes.

The proper Greek spelling of the only planet named after a Greek rather than Roman equivalent god. Yes, I’m sick of all the unfunny jokes.

@ # 78 Stone Age Scientist :

How massive are these [supermassive Galactic Black Holes] things? Do they dwarf VY Canis Majoris at all?

In mass, yes – they have many millions of stellar masses – but this mass is immensely compacted and crushed down until they fit well within the size of our solar system. I’m not sure exactly how they measure up to VY Canis Majoris diameter~wise. This may depend on the individual Galactic Supermasive Black Hole as these vary in size. For example : they tend, I understand, to be smaller for spiral and barred spiral galaxies like ours and larger in the giant elliptical galaxies such as Centaurus A and M87.

@ 3. Eric Kolb Says:

This video brings back into focus the apparent lack of standardized nomenclature when it comes to celestial bodies. The video moves from Rigel (a blue supergiant), to the much larger Pistol Star (a blue hypergiant), to the even larger Antares A (a red… supergiant). So, super < hyper < super. The lack of precision in the terminology used in what we call these things is frustrating…

No, the terminology is very precise – and the blue and red kinds of giant, supergiant and hypergiant are different from the red varieties – as pointed out by # 56 Promii :

@ # 56. Promii :

@3 The Pistol Star is way more massive than any other star in the video even if it is smaller in diameter, hence the terminology. Those red hypergiants with a diameter the size of Saturn’s orbit are fluffy fluff and not very dense at all.

Exactly. The red supergiants (& I suppose hypergiants too) are often described as being “red hot vacuum” at least in their outer layers.

Blue giants, blue supergiants and, yes, even blue hypergiants such as the Pistol Star are much smaller, much denser – and much hotter hence their colour – than their red equivalents. It makes sense if you understand the physical nature of these stars.

I gather that the most massive of all stars actually skip the whole ‘red’ stage – failing to become red hypergiants because of the Humphreys-Davidson (spelling?) limit. This is to do with mass loss through major stellar eruptions and winds and the fact that these stars have enormous radiation pressures which literally tear their outer layers away. They become Luminous Blue Variables like Eta Carinae instead before possibly evolving into Wolf-Rayet stars then going supernova or just going supernova directly like SN 1987 A.

Oh & congrats to those who spotted the backwards rotation of the planets – I totally missed that.

Galactic supermassive black holes range in diameter from a low of about 370,000 miles to roughly 37,000,000,000 miles.