# Relatable comparison of VY Canis Majoris to the Sun?

I was trying to describe how vast the largest known star is to someone and felt I wasn't quite able to relate the scale difference. I know it's roughly 1500 times larger than the sun. Anyone know of a good analogy?

• apologies if this is a bit off topic, I couldn't think of a more appropriate stack to ask it. Commented Feb 7, 2017 at 13:58
• These are perhaps slightly dramatic simulations I'd come across a while ago. However, on a personal level, they never fail to leave me breathless...! (1) youtube.com/watch?v=GoW8Tf7hTGA and (2) youtube.com/watch?v=Bcz4vGvoxQA Commented Feb 8, 2017 at 0:58
• Just point to the sun and indicate how much of the sky would be filled by VY Canis Majoris at the same distance. If that doesn't get the point across, it's pretty much a lost cause. And you might mention how far out the far side would be. Commented Feb 8, 2017 at 4:56
• @user2338816 The notion of how much of the sky would be filled by the star doesn't make much sense when you're inside the star. Commented Feb 8, 2017 at 12:37
• Note: VY Canis Majoris is no longer the largest known star. According to Wikipedia and its sources, there 6 more known stars that have been estimated to be larger: KY Cygni, V354 Cephei, Westerlund 1-26, RW Cephei, WOH G64, UY Scuti. These stars have a ratio of 1500-1900 times larger than the sun. Commented Feb 8, 2017 at 15:21

## 7 Answers

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 diameter, this divided by 1500 is about 8cm which is roughly the diameter of a ring donut.

## 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.

Approximately the same shape are the ore freighters that go on the Great Lakes. They're called 1000 footers because, go figure, they're roughly 1000 feet long. The banana is to the freighter as the sun is to YV Canis Major.

Here's a picture of one of those freighters. Now imagine one of the workers is having lunch, eating a banana.

• You meant to post this to BoingBoing, right? :-) Commented Feb 8, 2017 at 12:52
• Why don't they call them kilofooters? Oh, wait, feet aren't SI. Commented Feb 8, 2017 at 17:19
• @JanDvorak you joke, but kft is pretty well known in aviation / aeronautical engineering... Commented Feb 8, 2017 at 19:18

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: 900 km / h

Sun's radius: 696,000 km

One circle around the sun: 4,373,096.97 km

Time for aircraft to complete this circle: 4858 hours ≈ 6.6 months

VY Canis Majoris radius: 988,320,000 km

One circle around VY Canis Majoris: 6,209,797,703 km

Time for aircraft to complete this circle: 6899775.225 hours ≈ 787.645 years!

PS: Looks like the math done in one of the videos shared in the comments above is incorrect :)

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 Jupiter's orbit.

Or it's the ratio of a standard tenpin bowling ball to the point of a sewing needle

The volumetric ratio is 1420^2 or about 2 million to one. That's roughly one person out of the entire population of Houston, TX. Or the ratio of 100 liters of water to a single drop from an eyedropper.

• I think comparing it to the orbit of Jupiter is going to be pretty difficult for most people to conceptualise (its how i originally described it to the person i was talking to in fact) I like the bowling ball and sewing needle idea Commented Feb 7, 2017 at 14:32
• This is like saying IC 1101 to Segue 2, not so obvious to people without specialized knowledge. Of course there are people who have not seen the London Eye or a Donut, or both.
– uhoh
Commented Feb 7, 2017 at 14:47

You should look at Mark Rober's video, he uses a size comparaison known by everybodyevery American: a football field!

Assuming the Sun is a normal soccer ball...

• Earth is a pinhead at 26 yards (23m) away from the Sun/ball.
• Jupiter is a grape at 135 yards (123m) away from the Sun/ball, almost the size of the field.
• Saturn is a smaller grape at "2,5 football fields away from the Sun/ball", which is almost 300 yards (274m)
• At 6:02 of the video, "the largest star known" would be the size of the Empire State Building: 381m (416 yards)

I think both the ore freighter / banana and donut / London Eye comparisons have scales that are relatable but lack "universality" in the sense that people may not know the size of the London Eye or an ore freighter. I'd suggest thumbnail vs bus, as both exist all over the world.

• There are quite a lot of different types of thumbnails. Did you mean the literal one, on an average human hand? Commented Feb 8, 2017 at 17:22
• @JanDvorak Literal, yes. I don't think it needs to be exact enough that it's necessary to specify what size hand. Commented Feb 9, 2017 at 7:03

Well, taking the scale of the solar system as an example, you can say that VY Canis Majoris is around 70% the size of Saturn's orbit.

Reference numbers:
Saturn's average distance from the Sun = 1,433,449,370 km.
VY Canis Majoris radius = 988,300,000 km.