As I understand it, defraction spikes generally happen to objects that are next door, in interstellar terms. As JWST is going to be looking at things muuuuuuuuuuuuuch further away, they shouldn’t be an issue.
Remember, for the calibration images they’re just taking snapshots of nearby stars. They’re not trying to look at really distant objects yet and spoil the surprise.
To be clear, those diffraction spikes are a result of the stars being over-exposed (the image is trying to pick up the surrounding dust, which is much fainter, so a longer exposure time is used which over-saturates the stars).
Dang it!
I had a dream last night that new video was posted in this thread showing a close binary star system with planets orbiting around them both. I was so geeked, but was surprised there was no attribution to which telescope made the video (timelapse). I assumed it was Webb, but was waiting for verification. When I got here, for a brief moment I wondered if it had been real.
Something interesting I just learned about the event horizon telescope and that picture is just how small of details we are looking at in the image. It looks fuzzy, but it may be about the sharpest image ever taken in terms of the width of details in the sky due to the sheer resolution of radio interferometry using such a large collaboration. Apparently people are asking if JWST will be able to look at this and get a better picture, but it’s already far better resolution than JWST can manage for something this small at this distance.
I read that these are the only two black holes that we can resolve with the EHT. Our own galaxy’s black hole due to proximity, and M87 due to its immense mass and distance being just right.
Anything else would require a larger radio telescope, and since the EHT is already the size of Earth, it means a large array of radio space telescopes is needed. So, expect these two black hole photos to be it for probably our lifetimes.
While the EHT may not be able to observe the shadow of other Black Holes, it is being used to observe the disks and jets of several other ones. Centaurus A was named as another target. Its also going to be used to probe Blazars - which are very energetic, thought to be black hole related, and not well understood.
Because I’m too lazy to look it up: does “resolve” for a black hole mean resolve something on the scale of the BH’s Schwarzchild radius? Because as @dtolman said while I was figuring out how to spell Schwarzchild, there are lots of other things around a BH that are also worth looking at, but a lot larger.
Matt_W
5143
Sag A* is about 4 million solar masses, which gives a Schwarzchild radius of about 0.08 AU, or only about 16x bigger than the sun and 5x smaller than Mercury’s orbit. Black hole event horizons are indistinguishable from empty space from a distance except by gravity, so we couldn’t image it. That image is, if I understand correctly, a bright radio source in the vicinity of the Sag A* black hole caused by magnetic fields in the accretion disc.
FYI - it may be possible to image one other Black Hole in our lifetime - the one in the center of M31 is about 1/5 the size of M87’s angular diameter (as seen from Earth). So add a Radio Telescope on the moon to the array, and we’re in business (hand waving away the dust surrounding it, and that the debris cloud may not be at a favorable angle to see the shadow of the Black Hole)
Also - this might be interesting to some - a comparison of what a simulated black hole would really look like (top) vs what we can make out at this distance/resolution with the telescope (below)
Matt_W
5145
Derek does a pretty good job explaining both how these images are created and what you’re actually seeing.
tl;dr: The black spot in the middle is actually the entire spherical event horizon imaged in the plane of the viewer by light rays bent around it. The sphere is mapped onto a circular radius of 2.6x the Schwarzchild radius (for a non spinning black hole, which Sag A* is not.) The accretion disk is also imaged into a circular disk, regardless of observer orientation, with a bright side caused by relativistic Doppler shift of matter particles coming toward us.
Go outside and look up - Lunar Eclipse for next few hours. Moon is a lovely red-orange.
Without fail, the rainiest May in Seattle in years strikes. I can’t see shit.
Overcast here too, sadly. Thanks for the heads-up, though!
Yeah, we had heavy clouds with thunderstorms L(
I had some good photo opportunities but a bear of a time trying to focus on the eclipsed moon - some camera settings I need to adjust as trying to manual focus was basically impossible because I couldn’t see anything but a black object obscured by digital noise. I managed to take a bunch of images and some turned out ok but I don’t think they’re super sharp. Next time I’ll try to prefocus on the moon while I can still see it. Also need to get a better tripod head, a lot of drift from center once I let go.
When I was in Romania I had the opportunity to see a lunar eclipse against a full moon, late at night at some wedding do. It was the most emotionally moved I’ve been over a stellar event - I’ve seen a couple of solar eclipses, those were cool, and had use of an observatory* back when I studied Astrophysics and also saw some cool things there… but sitting there, clear sky, watching that shadow slowly drift across the surface of something so familiar and yet so far away… It was kinda otherworldly in a way the other stuff wasn’t?
Minus the need for specialised equipment (telescopic lenses, protective goggles) I just felt more ‘there’ - so I just sat back, sipping my cocktail and really just let the scale of the universe wash over me completely. Nobody else noticed - they were too busy dancing - but I pointed it out to my partner and we watched it together in silence away from the main party. Sure, emotionally there was probably a lot of other stuff going on too but I wouldn’t trade that moment for anything**.
* A small one. Plus it was England, most days there was nothing to look at but clouds.
** I will say my earthbound sky viewing isn’t complete - I haven’t seen the aurora in person, would very much like to at some point, maybe it’ll be better?
Dr Tyson is generally right - a lot of the time the moon just looks like a shadow is passing over it as it dims. Last night’s was very pretty - the moon was a noticeable orange-red like at sunset, even though it was high in the sky. We can probably thank the volcano that blew up in Tonga for that.
vyshka
5154
He is right, but it was funny.
