The incredibly rich galaxy cluster is a huge source of mass in the nearby Universe. But there is… [+] There are a series of red dots surrounding the central mass: a distant galaxy less than 2 billion years after the Big Bang.
ESA / Hubble and NASA, B. Frye
NASA’s Hubble Space Telescope, which is currently celebrating its 30th anniversary, still produces new discoveries.
The Hubble eXtreme Deep Field (XDF) may have observed a region of the sky only 1 / 32,000,000th of the… [+] Total, but was able to discover a whopping 5,500 galaxies within it – an estimated 10% of the total number of galaxies actually contained in this pencil beam style cut. The remaining 90% of galaxies are too faint or too red or too dark for Hubble to reveal.
HUDF09 and HXDF12 / E. Siegel equipment (processing)
By observing the distant Universe, Hubble reveals galaxies from all cosmic time.
This small portion of the eXtreme deep field illustrates an important concept: if we count the number… [+] of galaxies in this image and extrapolating how many similar images we would need to cover the entire sky, we can get an estimate of how many galaxies would be revealed in the entire sky in the eyes of Hubble. The actual number of galaxies is significantly higher.
NASA, ESA, H. Teplitz and M. Rafelski (IPAC / Caltech), A. Koekemoer (STScI), R. Windhorst (Arizona State University) and Z. Levay (STScI)
However, even with phenomenally deep views, most galaxies still remain undiscovered.
The galaxies identified in the eXtreme Deep Field image can be divided into nearby, distant and… [+] ultra distant components, with Hubble only revealing the galaxies it is capable of seeing in its wavelength ranges and in its optical limits. It is important to remember that the light we see is only the light that arrives at this time, after traveling through the vast expanse of space.
NASA, ESA and Z. Levay, F. Summers (STScI)
The light spreads as the distance increases, making the first galaxies too faint for most observatories.
The brightness distance ratio and how the flux of a light source falls as one on the… [+] squared distance. A galaxy that is twice as far from Earth as another will be only a quarter of a brightness bright.
E. Siegel / Beyond the Galaxy
Furthermore, the expansion of the Universe stretches the wavelength of light, displacing it out of the visible range.
This simplified animation shows how the redshifts and how the distances between unjoined objects change.… [+] over time in the expanding Universe. Note that objects start closer to the amount of time it takes for light to travel between them, light shifts red due to the expansion of space, and the two galaxies end up much farther apart than the light taken by the photon exchanged between them.
Rob knop
However, Einstein’s idea of massive curvature space often helps.
An illustration of gravitational lenses shows how background galaxies, or any path of light, is… [+] distorted by the presence of an intervening mass, but it also shows how space itself is bent and distorted by the presence of the mass in the foreground. When multiple background objects are aligned with the same close-up lens, a properly aligned observer can see multiple sets of multiple images.
NASA / ESA
The intermediate concentrations of matter between us and a distant object can stretch, distort and magnify its light.
The distant lensed galaxy, nicknamed the Arc of the Sunburst, has its light coming now since when… [+] The universe was only 3 billion years old. The lens enlarges and illuminates the background galaxy up to 30 times its normal apparent luminosity, revealing features as small as 520 light-years across.
NASA, ESA and E. Rivera-Thorsen (Institute of Theoretical Astrophysics in Oslo, Norway)
This phenomenon – strong gravitational lenses – reveals objects that would otherwise be too faint and distant to be seen.
The Hubble Border Fields MACS 0416 galaxy cluster, with the mass shown in cyan and… [+] magnification of the lens shown in magenta. That magenta-colored area is where the lens magnification will be maximized, as there is an area located at a specific distance from any given mass distribution, including galaxies and galaxy clusters, where brightness enhancements will be maximized.
STScI / NASA / CATS / R. Livermore Team (UT Austin)
A decade ago, the Herschel (infrared) and Planck (microwave) observatories combined to identify candidates for galaxies with lenses.
The image below, from one of the galaxy clusters identified by Planck and Herschel, shows a 2016… [+] ALMA monitoring at very long wavelengths. The identified marks of A, B and C all correspond to the same background galaxy, with multiple lenses in the foreground.
N. Nesvadba et al. (2016), arXiv: 1610.01169
Follow-up observations, made with Hubble, finally revealed its details.
Six of the galaxy clusters identified by Planck and Herschel were photographed here by Hubble, showing… [+] the ultra distant galaxy starburst PLCK G045.1 + 61.1 in the lower left panel.
Brenda L. Frye et al. (2019) ApJ, 871 51
Here, a background galaxy (PLCK G045.1 + 61.1) appears as multiple red dots, with lenses in a massive foreground group.
Seen here in incredible detail, thanks to the NASA / ESA Hubble Space Telescope, it’s the starburst… [+] galaxy formally known as PLCK G045.1 + 61.1. The galaxy appears as multiple reddish dots near the center of the image and is being gravitated by a group of closer galaxies that are also visible.
ESA / Hubble and NASA, B. Frye
It is a star-forming galaxy, appearing just 1.9 billion years after the Big Bang.
The same image, with all three images of the ultra distant background galaxy highlighted here. These… [+] multiple images have different light paths to Earth; If a supernova is triggered in this galaxy, we will observe that its light arrives at three different times.
ESA / Hubble and NASA, B. Frye
The stars within are intrinsically blue; The red color arises from the cosmic expansion.
Galaxies comparable to the current Milky Way are numerous, but the youngest galaxies that are Milky… [+] The shapes are inherently smaller, bluer, more chaotic, and more gas-rich overall than the galaxies we see today. Galaxies just 2 billion years after the Big Bang are dominated by stars with much bluer colors than our Milky Way, but appear red (or infrared) due to the expansion of the Universe.
NASA and ESA
Using similar techniques, NASA’s upcoming James Webb Space Telescope will tear apart our first records of galaxies.
As we explore more and more of the Universe, we can look further into space, which… [+] equals further back in time. The James Webb Space Telescope will take us to depths, directly, that our current observation facilities cannot match, with Webb’s infrared eyes revealing ultra-distant starlight that Hubble cannot expect to see.
NASA / JWST and HST teams
Mostly Mute Monday tells an astronomical story in pictures, images and no more than 200 words. Talk less; smile more.
