Betelgeuse To Blow Up Soon — Or Not 312
rubycodez writes "A wave of 2012-related hoopla has hit the internet about the star that makes the 'right shoulder' of Orion the hunter: Betelgeuse. Astronomer Phil Plait once again puts rumors to rest. The star will indeed explode as a type II supernova, and when it does it will be brighter than Venus when viewed from Earth, though not as bright as the full moon. It will be visible in the night sky for weeks, and could be visible in the day sky for a short time. But that event could happen today or 100,000 years from now, or as much as a million years from now. Since Betelgeuse is over 600 light-years away, its violent death will not harm Earth in any way, but will definitely provide a huge bonanza of scientific information about supernovae. As geeks, we can only hope the core of Betelgeuse undergoes catastrophic failure in our lifetime."
Re:Soon? (Score:4, Interesting)
How do we actually know that the wave/particle/whatever I see when I glance up at Betelguese is about 600 years old. It seems to me that we would need to know a few things first, before we could calculate that:
How fast is the Earth moving through space? Not toward or away from Betelguese as in red and blue shifts of that particular star but just how fast are we moving through space in general. Can we look at one part of the sky and see everything red shifted and another part of the sky and see blue shifted and extrapolate the total speed from that (obviously we would need a series of measurements)? Do we know how fast the galaxy is moving, or even the speed that the sun moves around the center of the galaxy? For instance if I'm driving a car east at 60 mph, can we take all those factors, add them together and determine the total speed of me and my car.
Does that combined speed cause a time dialation effect (even a tiny one) on Earth? I know time and mass becomes distorted as you approach the speed of light, but I've never heard how steep that gradient is or if there is a lower limit. Would a hypothetical stationary cup of water cooled to absolute zero experience time differently then a similar cup boiling at 100 degrees (obviously the difference would be very tiny, but would it be there or is there a cut off)?
If the universe is expanding in the sense that there is more space between all particles (this was how it was explained to me: that with each passing moment the distance between all particles increases as the fabric of space-time slowly expands) wouldn't the speed of light be slowly increasing (or decreasing) as well. Would a lightyear 600 years ago be the same as it is now?
I know that the margins of error in determining astrological distance are way larger then any of these factors, and wouldn't effect the "about 600 lightyears away" distance of Betelgeuse. I'm asking more hypothetically. "Are these even factors?" is what I'm asking. What do we know and what don't we?
It's kinda hard to find the answers short of getting an astrophysics degree, so I'm hoping someone here with one could help me out.
Re:Soon? (Score:2, Interesting)
The questions you raise are valid. We don't know how long it takes a photon to get here from Betelgeuse down to the nearest second. For stars which are fairly close astronomers can use parallax to get a precise distance. They do that by measuring the position of the star in the sky six months apart with the orbit of the Earth around the run providing a baseline. I don't know if they can do that for Betelgeuse. It might be a bit too far away. Beyond that they rely on measuring the brightness and spectrum of a star to estimate distance.
So its not going to be 600.00000000000000 light years away but by one POV that really isn't important. Relativity says that the photon coming from Betelgeuse experiences no time when it travels those 600 light years. So the travel time is zero. If we see the star explode in 2020 then it would have exploded in 2020.
Re:Soon? (Score:5, Interesting)
After the Big Bang occurred the matter was very very hot. So it looked basically like fire. But since entire universe was "on fire" and light has a finite propagation speed we can still see light just reaching us now from very far away places in the universe - Cosmic Microwave Background.
It has many interesting properties. First, as you point out you can measure our speed relative to it. Secondly, it has a very long wavelength which is due to expansion of the universe - the places farther away are moving away from us.
The expansion of the universe is actually very very small even on the scales of a solar system or galaxy and starts to matter on the intergalactic scales. It is characterized by Hubble constant [wikipedia.org]= 70 (km/s)/Mpc - for each million parsecs the speed goes up by 70 km/s. For comparison, Earth's orbital speed is 30 km/s and the size of the entire Milky Way (our galaxy) is only 30 thousand parsecs.
Yes, there is a time dilation effect.
Btw, speaking of time dilation effect, the scientists at NIST has recently built an atomic clock based on a single Aluminum atom [nist.gov] that is so accurate that they can see time dilation from Earth gravitational field. They measured the rate of their clock, than raised the setup and measured a faster rate - clocks slow down in stronger gravitational field and Earth field decreases by a small amount as you get further away from Earth.