The Universe At Large 002 - T Tauri Stars (Part 2 of 2)
07 Nov 2015Undomyr
The Universe At Large 002 - T Tauri Stars Part 2Hello and welcome (back) to The Universe At Large. As promised this part of the T Tauri Stars logs concerns a little more of the physics and nitty gritty space science that apply to T Tauri stars.
The image you see below this text are of the system where the first T Tauri star was discovered, simply named T Tauri. It is positioned about 420 lightyears behind the constellation Taurus. Yes, the star type is simply named for the system it was first found in. No one said scientists had to be original in their naming of things.
I’ve been to the T Tauri system to have a look around and get a picture of the star in question T Tauri B.
The nebula in the background is a reflective nebula, it is colourless itself but depending on the angle of T Tauri A and B the colours shift and dance.
Now for the science of T Tauri’s. As I mentioned in part 1 T Tauri’s are in the pubescent phase of their existence. But they are far from adults yet and there is a very good chance that they will not become adult stars at all, due to the conditions surrounding them.
A T Tauri receives the energy needed to make its hydrogen glow and burn from a much more mundane source. Rather than fusion in the core it simply rotates, the centrifugal force resulting from this being enough to slowly heat up and compress the T Tauri.
At first T Tauri’s are larger and more luminous (they glow more brightly) than the adult stars they might become someday. As they rotate and compress they become less and less luminous.
How fast they rotate is the deciding factor that determines their future.
If they rotate too slowly they will have burned away too much of their mass to ever be able to sustain fusion in the core. There is simply not enough pressure to force two hydrogen atoms close enough to each other. The temperature hasn’t risen enough as well, as with the lost mass the rotation slows down and the energy put into the star diminishes.
This is a T Tauri that will slowly fade away. It has not made it and will stop glowing eventually.
So what happens if they do rotate fast enough? Then the real magic happens deep under the surface. A star consists of more than just hydrogen at first; there are deposits of many other elements inside, of varying weight and thus at varying depth beneath the surface.
The rotation moves the heavier elements deeper into the star, making the core heavier and heavier. The crucial element is lithium. It takes about 100 million years to move lithium to the inner core of a T Tauri, and this is how long astral-puberty takes. When the lithium reaches the core, the temperature there is around 2 million kelvin. This is too much for the lithium atoms to bear. They shatter into their base components; electrons, neutrons and electrons. Their mass is converted to energy according to E = MC^2. This is comparable to several hundred thousand Hiroshima nuclear bombs going off in less than a nanosecond, in a space no larger than a football.
It is this eruption of energy that forces the first two hydrogen atoms together and fuses them into helium. The energy from this fusion starts the chain reaction and faster than would be measurable the T Tauri shrinks, dims and is now an adult star ready for billions of years of fusion.
If you would be next to this awesome event, you would one moment be next to a T Tauri, not scooping a single whiff of hydrogen, the next the star would be further away and fuel would be scooped.
So next time you come across one and curse it for not giving you its hydrogen; check if there is another star in the system that helps spin it around. If there is, don’t be mad, it’s going to be a star one day and it’ll gladly give you all the hydrogen you need. But for now it needs it to grow up.
If there isn’t another star, don’t be mad, but sad. This is a T Tauri that will die alone and cold in space. Be nice to the T Tauri; they are the future of the light in the universe and they deserve our gratitude.
Please leave a message if you have a suggestion, comment or have spotted an error in any of this.
Undomyr, signing off.