What is a Nova? How Does It Compare to a Supernova?

We’ve talked about supernovae plenty of times, but what about just regular, plain old novae? What are they, and how are they different from the star destroying explosions we know and love?

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Jason Harmer - @jasoncharmer

Created by: Fraser Cain and Jason Harmer
Edited by: Chad Weber
Music: Left Spine Down - “X-Ray”

There are times when I really wish astronomers could take their advanced modern knowledge of the cosmos and then go back and rewrite all the terminology so that they make more sense. For example, dark matter and dark energy seem like they’re linked, and maybe they are, but really, they’re just mysteries.

Is dark matter actually matter, or just a different way that gravity works over long distances? Is dark energy really energy, or is it part of the expansion of space itself.

Black holes are neither black, nor holes, but that doesn’t stop people from imagining them as dark tunnels to another Universe.

Or the Big Bang, which makes you think of an explosion.

Another category that could really use a re-organizing is the term nova, and all the related objects that share that term: nova, supernova, hypernova, meganova, ultranova. Okay, I made those last couple up.

I guess if you go back to the basics, a nova is a star that momentarily brightens up. And a supernova is a star that momentarily brightens up... to death. But the underlying scenario is totally different.

As we’ve mentioned in many videos already, a supernova commonly occurs when a massive star runs out of fuel in its core, implodes, and then detonates with an enormous explosion.

There’s another kind of supernova, but we’ll get to that later.

A plain old regular nova, on the other hand, happens when a white dwarf - the dead remnant of a Sun-like star - absorbs a little too much material from a binary companion. This borrowed hydrogen undergoes fusion, which causes it to brighten up significantly, pumping up to 100,000 times more energy off into space.

Imagine a situation where you’ve got two main sequence stars like our Sun orbiting one another in a tight binary system. Over the course of billions of years, one of the stars runs out of fuel in its core, expands as a red giant, and then contracts back down into a white dwarf. It’s dead.

Some time later, the second star dies, and it expands as a red giant. So now you’ve got a red dwarf and a white dwarf in this binary system, orbiting around and around each other, and material is streaming off the red giant and onto the smaller white dwarf.

This material piles up on the surface of the white dwarf forming a cosy blanket of stolen hydrogen. When the surface temperature reaches 20 million kelvin, the hydrogen begins to fuse, as if it was the core of a star. Metaphorically speaking, its skin catches fire. No, wait, even better. Its skin catches fire and then blasts off into space.

Over the course of a few months, the star brightens significantly in the sky. Sometimes a star that required a telescope before suddenly becomes visible with the unaided eye. And then it slowly fades again, back to its original brightness.

Some stars do this on a regular basis, brightening a few times a century. Others must clearly be on a longer cycle, we’ve only seen them do it once.

Astronomers think there are about 40 novae a year across the Milky Way, and we often see them in other galaxies.

The term “nova” was first coined by the Danish astronomer Tycho Brahe in 1572, when he observed a supernova with his telescope. He called it the “nova stella”, or new star, and the name stuck. Other astronomers used the term to describe any star that brightened up in the sky, before they even really understood the causes.

During a nova event, only about 5% of the material gathered on the white dwarf is actually consumed in the flash of fusion. Some is blasted off into space, and some of the byproducts of fusion pile up on its surface.

Over millions of years, the white dwarf can collect enough material that carbon fusion can occur. At 1.4 times the mass of the Sun, a runaway fusion reaction overtakes the entire white dwarf star, releasing enough energy to detonate it in a matter of seconds.

If a regular nova is a quick flare-up of fusion on the surface of a white dwarf star, then this event is a super nova, where the entire star explodes from a runaway fusion reaction.

[Amariachan]

we need a coffee nova where suddenly everyones cup is filled with delicious coffee

[corrinflakes]

All these years later I finally find what a base nova is. It’s so weird how hard this used to be to find. I’d get supernovas, hypernovas even, nothing about simple “nova” to give context to what those prefixes connect to.

[charshii]

Hey Fraser I have a cool thought experiment, and I was hoping maybe you could possibly make video about, tell me what you think.

So since the earth round, if you had a perfectly straight platform or something like that. Theoretically if it was long enough and you placed it on the surface of the earth wouldn't it eventually go out into space? Like image taking a pencil and placing it on top of a tennis ball, the pencil would be resting on a small part of the ball while the rest of it wouldn't be touching the surface and would be going of into 'space'

So what I'm wondering is how long would a so called platform like that have to be until it started to go of into space. And would we even be able to build something like that?

Tell me what you think, I really hope maybe you could make a video on it, I think it would lead to some cool discussions!

[DirtyPhlegm]

Thanks for your videos. They are really relaxing, love the background choices, and you speak with great clarity and interest. I'm studying for my final on astronomy :)

[Unther]

I think a Magnetar would be an interesting subject. And maybe how one could extract energy from its super-strong magnetic field.

[vonderbeard]

Momentarily brightens up to death. I love it, you should put that on a shirt!

[stilnessspeaks]

I could listen to you talking about space all day and all night. Does that make me weird?

[ronintennispro]

Bossa Nova is The Greatest Nova... one can even go as far as to say... "Fraser Cain and his Youtube Channel is Surfs up DUDE! :)

[herculesrockefeller]

I had a Chevy Nova, that thing used to detonate into spectacular flames too

[Tyler-syjo]

Space madness? I don't have space madness! You just want my ice cream bar! *tears up* I've had it since I was a CHILD!

[lorenzo.bernacchioni]

Hi Fraser, topic suggestion: inflation at the early stage of the Universe. Do we have direct observations that support it or so far it is still an -ad-hoc- answer to solve the puzzle of cosmology? Thanks for your videos.

[cauchyhorizon]

Personally, I think the Big Bang should be renamed 'the Horrendous Space Kablooie'.

[Strideo]

Sharknova. When a nova is full of sharks.

Coming to the SyFy channel soon!

[truvc]

Fraser Cain I wanna know: Could we land on the sun in the winter when it’s colder?

[markuskohlmann]

Could it be possible that this time T CrB ends up in a supernova type 1a instead of a nova?

[comrad]

This man is one of a few here on youtube who seems to actually know what he's talking about , i've never seen any channel that understand what type 1a supernovae are except this channel

[userwl]

well winters almost here and I see orion still has betelguise . hope to see it light up.this year.. any....year now....🤔💣💥

[iffatzarif]

Do an episode on cataclysmic variable stars

[jaredpatterson]

I saw a video about the idea of blasting nuclear waste into the sun but it said hitting the sun is hard since we orbit around it at 30 m/s..
So what if we picked a different target, like Jupiter? Surely the immense pressure would get rid of any toxic waste right? Didn't they already crash a probe into its upper gas clouds before it dissolved?

[cgaccount]

Could a white dwarf slowly turn back into a regular star if it happened to drift through a gas cloud over a long period of time?