Webb Mission Updates
James Webb Space Telescope 26 December, 2021 Update – First Mid-Course Correction Burn Completed, NASA
“At 7:50 pm EST, December 25, 2021, Webb’s first mid-course correction burn began. It lasted 65 minutes and is now complete. This burn is one of two milestones that are time critical — the first was the solar array deployment, which happened shortly after launch.”
NASA’s James Webb Space Telescope launches in French Guiana, Washington Post
“Tens of thousands of people have committed over 20 years or more on a single project,” Matt Mountain, an astronomer who is part of the team that designed the telescope, said at the telescope institute just minutes before launch Saturday. “And why? Why have they committed this time? We solve incredibly hard problems. It’s part of the human spirit. We’re curious. We explore.”
Go Webb Go!
“light from the early universe” I dunno but some reason I can’t wrap my head around this. Logically I understand but at those distances and such long time ago, I have nothing in my neighborhood to compare that with. CVS drug store is only 5 or 10 minutes away from my home depending on how many redlights I encounter.
The universe is expanding and carrying all the galaxies away from each other at what appears to be speeds that exceed light speed. The galaxies themselves are moving within the fabric of space-time at a very slow speed but space-time itself is carrying the galaxies with the fabric (another round of Romulan ale, Scotty and Spock).
Think about raisins in an expanding batch of rising dough. The ones that start out farther from each other move away from each other more than those that start closer to each other.
In the universe, the red shift due to the apparent speed move into the IR range.
I think, if the universe is expanding faster than the speed of light, we wouldn’t see any stars, as the stars light would never reach us, as we are expanding away from the light source faster than its light. So I think right now, the Universe has not reached that speed of expansion. We should know it – if earth still exists – when it happens.
The thing about light velocity is that it neither adds to or subtracts from the velocity of the source. It is not like throwing a ball forward from a moving train where vf = vt + vb. That’s what makes this all so counter intuitive.
The universe is expanding uniformly, so nearer portions aren’t receding as fast, and it has existed and has been expanding for 13-ish billion years, so we can see parts of the universe that are now receding faster than light, we just can’t see them as they are now.
The furthest thing we see is also the oldest thing we see: the universe cooling to the point where it becomes transparent to light, red-shifted by expansion so we see it as a microwave background. Those parts of the universe have since formed stars and galaxies, but that light hasn’t reached us yet. All the stars and galaxies we do see are from nearer parts of the universe, close enough for us to see more recent events, the CMB radiation from such regions having passed us long ago.
What thruster type is used on Webb? I can’t believe hypergolics are used.
The thrusters use nitrogen tetroxide and hydrazine. That’s a hypergolic propellent. Why is that hard to believe?
I expected, clearly incorrectly, that hypergolic combustion products might contaminate the optics systems.
I suspect they worried about that. Probably quite a bit. But the thrusters are on the opposite side of the sunshield from the optics, fire in the other direction, and are far enough from the edges of the sunshield that the exhaust would probably be collisionless by the time it got near the edges. Under those circumstances, I think they could show contamination wouldn’t be a problem. But the location and pointing of the thrusters did make its trajectory a little odd. It can only accelerate away from the Sun, and that dictated some of the details of the trajectory to L2.
Thanks for the explanation. Helpful, and educational.