Why can we see the Pillars of Creation, but not Proxima B?

Question

I was wondering how is it that we can see the Pillars of Creation (I know they're no longer there too) which are labeled as 6,500 light years away from earth and yet Proxima B is labeled at just 4.2 light years away and yet we cannot see it clearly and it was very difficult to find?

I understand that the Pillars of Creation are giant gas bubbles with different molecules that make it so visible and Proxima B is a relatively tiny planet that doesn't emit light but I cannot fathom how much greater the distance is from Proxima B and yet it is clearly much more visible. Shouldn't our current technology be able to view 'close up' images of Proxima B?

What am I missing here?

Answer 1

Simply put, the Eagle Nebula (from which the Pillars of Creation originate) shines quite brightly, much more than Proxima Centauri (which is a red dwarf). First, we'll take a look at their absolute magnitudes (how bright an object actually is) and their apparent magnitudes (the brightness an object appears to have, based on its distance from us). Both are logarithmic, with lower numbers being brighter and higher numbers being dimmer.

The Eagle Nebula's absolute magnitude is a whopping -8.21. Meanwhile, Proxima has an absolute magnitude of 15.60. The formula relating absolute magnitudes and apparent magnitudes is: $$M = m - 5 (\log_{10}{d}-1)$$

Where $M$ is the absolute magnitude, $m$ is the apparent magnitude, and $d$ is the distance, in parsecs. Plug in those numbers, and we find that the Eagle Nebula has an apparent magnitude of 6. Meanwhile, Proxima Centauri has an apparent magnitude of 11.13.

If we wanted to compare Proxima Centauri with the Eagle Nebula, we could use the formula:

$$v_b = 10^{0.4 x} = 10^{0.4×(11.13-6)} \approx 113$$

So the Eagle Nebula shines approximately 113 times brighter than Proxima Centauri. It's no wonder why Proxima Centauri b isn't visible to the naked eye — even its host star is too dim to see from the naked eye. Sure, the Alpha Centauri star system has other stars in it, but those are about 15,000 AU from Proxima, so they should have a minimal effect on the planet's brightness.

Answer 2

First, let's talk about size. The Pillars of Creation aren't just "giant gas bubbles"; they're clouds of gas and dust four light-years long. That's enormous, about 36,000,000,000,000 kilometers. Proxima Centauri b, on the other hand, has a diameter of 0.8-1.4 Earth diameters; one Earth diameter is approximately 12,700 kilometers. That's miniscule, in comparison.

Let's look at the angular diameters of the objects. The general formula is $$\delta=2\arctan\left(\frac{\text{diameter}}{2\cdot\text{distance}}\right)$$ where the angular diameter is in radians. The Pillars of Creation are 6,500 light-years away, conservatively, giving just them an angular length of $3.52\times10^{-2}$ degrees. Proxima Centauri b is 4 light-years away, with an angular diameter of about $2.02\times10^{-8}$ degrees. 6 orders of magnitude is nothing to sneeze at.

Additionally, the Pillars of Creation are located in an emission nebula. Light from the young stars that have just been born ionizes gas in the Eagles Nebula, which in turn emits the light. The dark gas and dust in the Pillars of Creation stands out quite sharply in all of this, making it easy to see.