50
votes
Is there any planet bigger than a star?
The answer depends on whether you mean is any planet bigger than any star, or whether the planet and star have to be in the same system and have been discovered/measured, rather than just that they ...
- 146k
26
votes
Accepted
Relatable comparison of VY Canis Majoris to the Sun?
After some playing around with wolfram alpha and google my best comparison has been
The sun compared to VY Canis Majoris is like a donut compared to the London Eye.
The London Eye is about 120m in ...
- 499
22
votes
Relatable comparison of VY Canis Majoris to the Sun?
On the banana scale, it's an ore freighter.
Every physicist worth their salt knows that the most important scale in the galaxy is the banana. Now, your average banana is between 7-8 inches in length.
...
- 413
19
votes
Accepted
Is the Sun really a medium size star?
It is true that a surprisingly large number of stars are smaller (and thus less massive) than the Sun. However, the stars that are bigger than the Sun are often much bigger.
Look at this chart:
...
- 36k
15
votes
Accepted
Which is the largest planet ever observed?
Yes, there is a limit. Anything with a mass larger than about 13 times that of Jupiter would be called a brown dwarf (a failed star), though whether such an object would consist entirely of gas, or ...
- 146k
14
votes
Is there a theoretical maximum size limit for a star?
A decent part of this answer is based on the introduction to Kroupa & Weidner (2005), though I’ve obviously gone into a lot more depth on all of the references.
Our story starts, as do many ...
- 36k
14
votes
Accepted
Size and mass of comet ATLAS (C/2019 Y4)
The confusion comes from the difference between the nucleus and the coma.
The nucleus is a small icy body, only a few km across.
The coma is the cloud of gas and dust released from the nucleus as it ...
- 116k
13
votes
Accepted
What is the apparent size of Earth from the Sun?
The calculation of the apparent size of Earth as seen from the Sun is pretty straight forward. Just consider the triangle: from your observation point the distance to the center of the object, to the ...
- 17.7k
12
votes
Logically, how can the universe be infinite in size?
Something infinite can expand.
Consider an infinite length of elastic. There are (infinitely) beads attached to it at 1m gaps. You might label one of the beads "0", then the next one is &...
- 116k
10
votes
Accepted
Size of Saturn's ring material
The vast majority of the particles in Saturn's rings are small, on the order of $\sim10^{-1}$ m or lower. The columnar number density, according to data from Voyager 1 and Earth-based observations, ...
- 36k
10
votes
Accepted
How big is one arcsecond at various distances?
How big is one arcsecond at various distances?
An arcsecond is a small angle, 1/3600 of a degree or about 5 millionths of a radian ($4.85\times10^{-6}$). To estimate the size of something that ...
- 116k
10
votes
Is there any planet bigger than a star?
If by "bigger" you are referring to mass, disregarding radius, then the answer is strictly no for a regular "star"
A star is a body that has reached a stable state in which ...
- 116k
9
votes
Relatable comparison of VY Canis Majoris to the Sun?
An airplane flying along the surface of the sun would take about 6.6 months to circle it once.
The same airplane would take 787 years to complete one trip around VY Canis Majoris.
Aircraft's speed: ...
- 359
8
votes
Regarding the age / size of the Universe
The expansion rate of space is not itself the reason that the radius $R_\mathrm{Uni}$ of the observable Universe is larger than 14 billion lightyears (Gly). Just the fact that space expands is the ...
- 37.1k
8
votes
Accepted
Existence of planets larger than their host star?
The answer to the question depends on the exact definition of planet that is used.
A possible example is the L dwarf 2M 0746+20 (2MASS J07464256+2000321) and its planet 2M 0746+20 b.
The radius of ...
- 734
8
votes
Accepted
Can a habitable planet be smaller than 0.58 Earth radii?
Short Answer:
In part Two of the long answer below, it is stated that a planetary mass object needs to have a mass of at least 0.1, 0.12, 0.23, or 0.25 Earth mass to be habitable. Worlds with those ...
- 7,439
8
votes
Size of the Unobservable Universe
The article Applications of Bayesian model averaging to the curvature and size of the Universe cited in the question is from 2011. It is now 2023 and we have much better data, in particular from the ...
- 1,720
7
votes
Accepted
Do more massive stars become larger or smaller white dwarfs?
More massive stars have a more massive core and produce more massive white dwarfs. The relationship between the initial mass of the main sequence star and the final mass of the white dwarf is ...
- 146k
7
votes
Accepted
What is the maximum size for a solid celestial body such that it still can be tunneled down to the core?
Such tunnels might be possible for objects up to a few hundred kilometres in size. Larger objects could be tunnelled if the tunnels are lined with high strength materials.
Assuming the centre of the ...
- 751
7
votes
What is the apparent size of Earth from the Sun?
According to space.com 109 earths could be lined up across the face of the sun. Therefore, if you were at the sun, the earth would look 109 times smaller than the sun does from the earth. This answer ...
- 71
6
votes
Accepted
If the Milky Way galaxy is as big as planet earth, how big is Earth?
Well, they are different shapes, but we can get a rough answer by doing a ratio calculation based on their radii.
Let $g$ be the radius of the galaxy, about $5\times 10^{20}\ \mathrm m$.
Let $e$ be ...
- 13.3k
5
votes
Relatable comparison of VY Canis Majoris to the Sun?
Depends a bit on whether you want to compare diameters or volume (3D).
For radius, consider that it's approximately 6.6 A.U., so if you dropped it into the Solar System it'd extend out to well past ...
- 3,763
5
votes
Accepted
Why haven't more captured small moons been found?
Encounters between small planetesimals and the larger core of planets (especially Jupiter) transfer momentum between the two. But momentum is conserved. Momentum is:
$p = m v$, where $p$ is momentum
...
- 96
5
votes
Accepted
When was the diameter of Titan first measured?
Discovery of Titan, 1655: Unknown diameter.
Dollfus, 1970: 4,850$\pm$300km (1). Measured by Filar micrometer (2) and diskmeter / double-image micrometer (3). (Apparently a summary of earlier ...
- 621
5
votes
Accepted
What if you 'placed' the Chicxulub asteroid onto the Earth?
An asteroid resting on Earth would be a mountain. Or, for smaller asteroids, a pile of gravel.
Mountains are limited in altitude by the strength of stone to resist compression: a too tall mountain ...
- 14.4k
5
votes
Logically, how can the universe be infinite in size?
Being infinite doesn't keep something from expanding. The expansion of space can be thought of as similar to the stretching of a coordinate plane by multiplying every coordinate by a constant, which ...
- 1,718
5
votes
Size of the Unobservable Universe
Yes, you are right. It refers to the Hubble volume rather than the Hubble radius, specifically it is 251 times the Hubble volume, but based on the volume, we can calculate the radius of the whole ...
- 1,208
4
votes
How big is one arcsecond at various distances?
James K's answer is right on, and probably what you're after. I just wanted to mention an effect which comes into play if you look really, really far away:
Because light moves at a finite speed, we ...
- 37.1k
4
votes
Finding the radius of a star in arcsec
Using basic circular maths: where $d$ is the distance of the star from the observer in AU, and $r$ is the star's radius in AU, and $a$ is the angle encompassed by the radius of the star in degrees:
$
...
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