Glittering Frisbee Galaxy: This image from Hubble’s shows a section of a spiral galaxy located about 50 million light-years from Earth. We tend to think of spiral galaxies as massive and roughly circular celestial bodies, so this glittering oval does not immediately appear to fit the visual bill. What’s going on? Imagine a spiral galaxy as a circular frisbee spinning gently in space. When we see it face on, our observations reveal a spectacular amount of detail and structure. However, the galaxy frisbee is very nearly edge-on with respect to Earth, giving it an appearance that is more oval than circular. The spiral arms, which curve out from the galaxy’s dense core, can just about be seen.

Although spiral galaxies might appear static with their picturesque shapes frozen in space, this is very far from the truth. The stars in these dramatic spiral configurations are constantly moving as they orbit around the galaxy’s core, with those on the inside making the orbit faster than those sitting further out. This makes the formation and continued existence of a spiral galaxy’s arms something of a cosmic puzzle, because the arms wrapped around the spinning core should become wound tighter and tighter as time goes on - but this is not what we see. This is known as the winding problem.

Image credit: ESA/Hubble & NASA

For more information on this image, visit: https://go.nasa.gov/2niODGL


Faintest Galaxies Ever Seen Explain The ‘Missing Link’ In The Universe

“By warping space, the light from background objects gets magnified, revealing extraordinarily faint galaxies. The only problem? The cluster itself is closer and overwhelmingly luminous, making it impossible to tease out the distant signals. Until now. Thanks to a superior new technique devised by Rachael Livermore, light from the foreground cluster galaxies can be modeled and subtracted, revealing faint, distant galaxies never seen before.”

One of the biggest puzzles in science is exactly how the Universe became transparent to visible light. Neutral atoms – cosmic dust – blocks visible light, and yet before there were stars, that’s all we had. According to theory, it should be large numbers of small, faint, ultra-distant galaxies that made it transparent, but they’ve never been seen. However, thanks to the combined power of the Hubble Space Telescope, gravitational lensing and a new foreground light-removal technique, galaxies 100 times fainter thank the ones visible in the Hubble eXtreme Deep Field – the longest-exposure image ever – have now been revealed. These galaxies, seen in two Frontier Fields’ clusters so far, are the ‘missing link’ needed to explain reionization.

Come get the full, stunning story in visuals and no more than 200 words on today’s Mostly Mute Monday!


Ask Ethan: Why Was The Universe Dark For So Long?

“One thing I wonder though is why did the dark ages last hundreds of millions of years? I would have expected an order of magnitude smaller, or more.”

There’s a troubling puzzle when it comes to the Universe: the so-called ‘dark ages’ don’t come to an end until 550 million years after the Big Bang. But this is a big problem when you consider that we’ve already imaged a galaxy from when the Universe was only 400 million years old, and that we fully anticipate the first stars to form when the Universe is only 50-100 million years old. So what’s with all the darkness, then? And how do we expect the James Webb Space Telescope to see back to the very first galaxies? The answer lies in two parts. First, even though you have stars, the Universe is still filled with neutral atoms, which block visible and ultraviolet light. We need to ionize those atoms in order to have a transparent Universe, and that takes lots of time. But the second key is that the Universe, even with neutral atoms, is quite transparent to other wavelengths of light, like infrared light. And that’s where an observatory like James Webb is going to be looking!

The Universe was dark for so long because it doesn’t just need light, it needs for all the light-blocking material to disappear. But we’re going to overcome that obstacle in less than two years anyway, and that’s something we should all be excited about!