Hello Space Fans and welcome to another edition of Space Fan News.
This week, gravitational waves are detected and a small asteroid will pass close to Earth
on March 5th.
Heavy news everyone!
Scientists using the Advanced Laser Interferometer Gravitational Wave Observatory in both Hanford
Washington and Livingsgton Louisiana have detected the very faint signal of two merging
30 solar mass black holes 1.3 billion light years away.
And the signal was in the form of gravitational waves.
Now I want to be clear here since there seems to be some confusion regarding what was discovered,
especially - and not surprisingly - among YouTube commenters.
So let’s be clear: Scientists have found ripples in spacetime, not nipples in spacetime
as many people on YouTube seem to think.
Nipples is spacetime is a different phenomenon entirely, and occur only under a specific
set of environmental conditions, namely a superbowl halftime show.
Zing!
Man, it felt good to get that out, I’ve been holding onto that joke all week.
OK, back to the episode.
Predicted to exist by Einstein 100 years ago in his General Theory of Relativity, gravitational
waves result when there is a sudden distortion in spacetime from the interaction of very,
very massive things, like from two merging black holes, or spinning neutron stars, of
a neutron star collision, or from a supernova explosion, or heavy thing one merging into
heavy thing two, you get the idea.
They were also created when from the creation of the universe - the Big Bang - and their
remnants permeate all the cosmos.
Detecting gravitational waves is very difficult, but as I’ve pointed out in SFN 144 when
I told you about the launch of the LISA Pathfinder mission, scientists use extremely sensitive
interferometers to carefully measure tiny distortions of space time - and when I say
tiny, I mean TINY!
- LIGO can measure the movement of spacetime as small as 1/1000th of the diameter of a
proton!
Imagine shooting laser beams at mirrors to look for modulated displacements of less than
a millionth of a billionth of a centimeter — smaller than the diameter of an atomic
nucleus.
That’s the equivalent of measuring the width of a human hair at a distance to Proxima Centauri,
some 4 light years away.
These waves were so small that when Einstein first talked about them, he never thought
they’d be observed, that they would be too small to detect.
But we live in the future now and hard things are what we do, and this time scientists have
really hit the jackpot with this discovery rivalling any others in the last century.
So here’s what happened, on September 14th, 2015 after testing an upgraded and improved
detector system, both stations (washington and louisiana) recorded the merging of two,
approximately 30 solar mass black holes, coming together some 1.3 billion light years distant.
Each station recorded the signal 20 milliseconds apart but they were identical, there was no
question about it.
That’s the main reason they have two observatories in two different locations in the first place,
so they can check that they weren’t just measuring the local conditions around the
buildings and grounds and stuff.
If both observatories measured a signal, then the local spacetime conditions can be removed
and be left with only the signal.
What’s also very cool about what LIGO can do is that when they detect a signal like
the one they announced yesterday, the can get lots of other information about it.
The shape of the signal says a lot about what the event was, like a black hole merger or
a supernova, the amplitude says a lot about the power of the event and because they have
two observatories, they can also tell what direction it came from.
They can also see the black hole event horizon directly in gravitational waves.
So the event detected back in September was of two merging black holes as I’ve already
said, and according to LIGO co-founder Kip Thorne of Caltech, the power output of the
merger was fifty times greater than all of the stars in the universe combined.
They also roughly estimated the direction of the event as somewhere in the direction
of the Large Magellanic Cloud, and happened some 1.3 billion light years away.
Gravitational waves don’t interact with matter, they are ripples in the fabric of
spacetime so whatever is floating around in space may be jostled by them, but not really
affected.
They’re so weak though that for all intents and purposes they are invisible to us on scales
of normal matter.
So what does all this mean?
Well for one thing, it proves conclusively that black holes exist.
For sure.
I know that may sound weird but black holes have been mathematical constructs for a long
time and their existence has been inferred by lots of other things we can see, like activity
in the centers of galaxies.
But now we know for sure they exist, because if they didn’t, we wouldn’t have observed
this merging of two of them into a bigger one.
Directly.
It also means we can learn more about how the universe was formed.
The remnants of the big bang are thought be to embedding in the fabric of spacetime of
the entire universe, now we can begin looking for them.
Alright, now that this is out of the way, what kinds of things can we hope to see that
we couldn’t before?
Spinning Neutron stars, black holes eating neutron stars, neutron star collisions, merging
black holes, galaxy collisions and mergers, supernovae, and of course, the above-mentioned
early universe.
We have never observed the universe in gravitational waves before, so we can’t tell for sure
what we will see, but plausible estimates predict between one-half and several hundred
events per year.
Hopefully, the success of LIGO will invigorate interest in other ways of looking for gravitational
waves, including at very different wavelengths.
The discovery announced this week opens a new era - and a completely new kind - of astronomy.
Gravitational wave astronomy promises to open our understanding of and provide an entirely
new window into, our universe.
Thanks again Einstein, and thank you LIGO.
Congratulations and well done!
Next, a little closer to Earth, well way closer actually, a little too close to be sure, NASA
has announced that on March 5th a small asteroid could fly past Earth as far away as 9 million
miles (14 million kilometers) or it could get as close to us as 11,000 miles (17,000
kilometers).
This asteroid, known as 2013 TX68, has flown past Earth before.
Two years ago it flew by at a rather comfortable distance of about 1.3 million miles (2 million
kilometers).
This time it’s going to get a lot closer, but NASA says it won’t hit us.
Scientists at NASA's Center for NEO Studies (CNEOS) at the Jet Propulsion Laboratory,
say there is no possibility that this object could impact Earth during the flyby next month.
But they have identified an extremely remote chance that this small asteroid could impact
on Sep. 28, 2017, with odds of no more than 1-in-250-million.
It’s going to flyby again in 2046 and 2097, and those flybys have an even lower probability
of hitting us.
Asteroid 2013 TX68 is estimated to be about 100 feet (30 meters) in diameter.
By comparison, that asteroid that broke up in the atmosphere over Chelyabinsk, Russia,
three years ago was approximately 65 feet (20 meters) wide.
If an asteroid the size of 2013 TX68 were to enter Earth's atmosphere, it would likely
produce an air burst with about twice the energy of the Chelyabinsk event.
This asteroid's orbit is quite uncertain, and it will be hard to predict where to look
for it.
There is a chance that the asteroid will be picked up by our asteroid search telescopes
when it safely flies past us next month, providing us with data to more precisely define its
orbit around the sun
While this thing won’t hit us in March, or probably never, I bring this up because
I for one, am very happy this program exists and I wanted you guys to know about it too.
The Center for NEO Studies is charged with letting us know what’s out there that could
hit us as soon as possible, cataloguing all the tiny and not-so-tiny bits of rock floating
around our solar system leftover from when the planets were formed.
NASA keeps a list of the next five close approaches to Earth; it links to the CNEOS website with
a complete list of recent and upcoming close approaches, as well as all other data on the
orbits of known NEOs, so scientists and members of the media and public can track information
on known objects.
Well, that’s it for this week Space Fans, thanks to all Patreon Supporters for helping
make SFN better - we are almost at our first milestone and I’m working on getting a free
DeepAstronomy App ready for you to download - thank you all for watching and as always,
Keep Looking Up!