Speaker A
This is an image of a lensing galaxy cluster called MACS 1149. And this particular galaxy cluster is very interesting because it is a lens for a gravitationally lensed supernova.
NASA Hubble explains how galaxy cluster MACS 1149 gravitationally lenses supernova Refsdal, producing multiple images used to measure cosmic expansion.
Key Takeaways
- Gravitationally lensed supernovae offer unique views of both dark matter and cosmic expansion.
- Multiple images of the same supernova arise from light traveling different paths around a galaxy cluster.
- Predicted timing of later supernova images was confirmed by Hubble observations, validating lensing models.
- Time delays between lensed images can be used to measure how fast the universe is expanding.
What the video covers
- The video shows Hubble imagery of galaxy cluster MACS 1149, which acts as a gravitational lens.
- The lensed background galaxy shows multiple images, and within it a supernova appears several times, nicknamed Supernova Refsdal.
- Four supernova images appear in an arrangement called an Einstein Cross, with the brightest cluster galaxy near the center where mass is greatest.
- Gravitational lensing occurs because massive objects warp space, bending light much like a glass lens.
- A diagram illustrates how light from the supernova travels along different paths around the lens before reaching Hubble.
- Differences in light travel time along these paths allow astronomers to constrain the distance to the supernova.
- This constraint provides information on how quickly the universe is expanding, an open question in astronomy.
- The lensing also offers insight into dark matter within the lensing cluster.
- Astronomers predicted that another image of the supernova would appear about a year after the first was discovered, and Hubble confirmed it.
- The video presents this prediction success as strong validation of lensing models and a rare opportunity to study the universe.
Chapters
- 00:00Introduction to galaxy cluster MACS 1149
- 00:27Multiple images of a background galaxy
- 01:05Einstein Cross and cluster mass distribution
- 01:35How gravitational lensing works
- 01:50Hubble's view and light paths through the lens
- 02:33Measuring cosmic expansion with time delays
- 03:09Predicting and confirming the supernova's reappearance
- 04:27Significance and closing remarks
Full Transcript — Download SRT & Markdown
Speaker A
This supernova was nicknamed Supernova Refsdal. So you can actually see this cool spiral galaxy that looks kind of like it's melting.
Speaker A
It almost looks a little bit like a Salvador Dalí painting of a galaxy.
Speaker A
This is actually a gravitationally lensed background galaxy that you're seeing multiple images of. And you can see some of these little dots here are a supernova that has gone off in this background galaxy and then been gravitationally lensed.
Speaker A
So we can see multiple images of it. So we can actually see the same supernova going off multiple times in this image, which makes it particularly cool to see.
Speaker A
These four dots are appearing in a pattern called an Einstein Cross. Closer to the center of this massive galaxy, this brightest fuzzy yellow object here would be the very center of the galaxy cluster.
Speaker A
This is where most of the mass is going to be. This is why you get the strongest distortions from gravitational lensing here.
Speaker A
You can sort of see this third image of the galaxy that's really stretched out.
Speaker A
You can sort of barely see it behind this brightest cluster galaxy. Gravitational lensing works where the galaxy cluster, or any other massive object, bends the space around it. With a massive object like this galaxy cluster in outer space,
Speaker A
it deforms the space around it. And then as light travels through that deformed, warped space, the light bends, just like looking through a glass lens.
Speaker A
This is another view of this lensing galaxy cluster, along with a zoom-in of the lensed supernova.
Speaker A
You can see here, this is the image that we were looking at previously, along with a few extra details added.
Speaker A
So this is our cute little Hubble Space Telescope down here, not perfectly to scale. And then you have an image of what the background galaxy would look like back here.
Speaker A
And these white lines are kind of tracing where the light from this background galaxy would travel through the galaxy cluster.
Speaker A
It acts as a lens. It actually bends the light rays back towards each other and back towards our telescope here.
Speaker A
Then if we look at this zoomed-in version down here, you have these four yellow points of light, which are all images of the same gravitationally lensed Supernova Refsdal.
Speaker A
So this supernova would have originated somewhere in this galaxy, and then the light from it would travel along these different paths around this lens, eventually meeting back up at our Hubble Space Telescope.
Speaker A
And what's really awesome about this is that by measuring the different time that it takes for the light to travel from its source to our telescope through these different paths around the gravitational lens, we can get a really strong constraint on exactly how far away the supernova is
Speaker A
and therefore a really strong constraint on how quickly the universe is expanding. This is an incredibly exciting image.
Speaker A
A gravitationally lensed supernova, like the one we're seeing in this image, is sort of a one-of-a-kind object.
Speaker A
It really gives us a very unique look at how these supernovae can interact with a gravitational lens, which gives us a ton of additional information on both the dark matter within the gravitational lens itself and a good amount of information on how the universe is expanding.
Speaker A
So this is kind of an open question that we're still grappling with as astronomers: exactly how quickly the universe is expanding.
Speaker A
One of the cool things about these gravitationally lensed supernovae is that once you see one, an image of it, you can predict when the other images are going to show that same supernova.
Speaker A
This Einstein Cross here was the first image of the supernova that was observed. But we were able to predict that another image of the galaxy, one of them, would have shown up about 20 years prior.
Speaker A
And then they were able to predict that actually this image over here, the lensed supernova, was going to appear in this image about a year after this first one was discovered.
Speaker A
So astronomers were then able to go back with the Hubble Space Telescope and observe it around when they predicted the second image would show up, and they were actually able to find it a year later, which was a really cool confirmation of the predictions.
Speaker A
They were able to actually predict where it was going to be, and then it showed up.
Speaker A
So it very clearly shows that our models are working very well. This is a unique way of measuring that expansion using these gravitationally lensed supernovae.
Speaker A
And this particular example is one of the best that we have. So this is a really incredible opportunity to study a whole lot of different components of the universe.
Topics:gravitational lensingHubble Space Telescopesupernova RefsdalMACS 1149galaxy clusterEinstein Crossdark mattercosmic expansionastronomyNASA
