Hubble Reveals A 'Red Dot Surprise' From The Distant Universe

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Hubble Reveals A 'Red Dot Surprise' From The Distant Universe

 

The incredibly rich galaxy cluster is an enormous source of mass in the nearby Universe. But there are a series of red dots surrounding the central mass: a distant galaxy from

 

less than 2 billion years after the Big Bang

 

NASA's Hubble Space Telescope, currently celebrating its 30th anniversary, still churns out novel discoveries.

 

 

The Hubble eXtreme Deep Field (XDF) may have observed a region of sky just 1/32,000,000th of the total, but was able to uncover a whopping 5,500 galaxies within it: an

 

estimated 10% of the total number of galaxies actually contained in this pencil-beam-style slice. The remaining 90% of galaxies are either too faint or too red or too obscured for

 

Hubble to revea

 

By peering into the distant Universe, Hubble reveals galaxies from across cosmic time.

 

 

This tiny slice of the eXtreme Deep Field illustrates an important concept: if we count the number of galaxies in this image and extrapolate how many such similar images we'd

 

need to cover the entire sky, we can get an estimate for how many galaxies would be revealed over the entire sky to Hubble's eyes. The actual number of galaxies is significantly

 

larger

 

However, even with phenomenally deep views, most galaxies still remain undiscovered.

 

 

Galaxies identified in the eXtreme Deep Field image can be broken up into nearby, distant, and ultra-distant components, with Hubble only revealing the galaxies it's capable of

 

seeing in its wavelength ranges and at its optical limits. It's important to remember that the light we see is only the light arriving right now, after journeying through the vast

 

expanse of space

 

Light spreads out as distance increases, rendering the earliest galaxies too faint for most observatories.

 

 

The brightness distance relationship, and how the flux from a light source falls off as one over the distance squared. A galaxy that's twice as far away from Earth as another will

 

appear only one quarter as bright

 

Additionally, the Universe's expansion stretches the light's wavelength, shifting it out of the visible range.

 

 

This simplified animation shows how light redshifts and how distances between unbound objects change over time in the expanding Universe. Note that the objects start off

 

closer than the amount of time it takes light to travel between them, the light redshifts due to the expansion of space, and the two galaxies wind up much farther apart than the

 

light-travel path taken by the photon exchanged between them.

 

However, Einstein's idea — of mass curving space — frequently lends a helping hand.

 

An illustration of gravitational lensing showcases how background galaxies — or any light path — 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 foreground mass itself. When multiple background objects are aligned with the same foreground lens, multiple sets of

multiple images can be seen by a properly-aligned observer

 

Intervening concentrations of matter between ourselves and a distant object can stretch, distort, and magnify its light.

 

The distant lensed galaxy, nicknamed the Sunburst Arc, has its light arriving now from when the Universe was just 3 billion years old. The lens magnifies and brightens the

background galaxy to up to 30 times its normal apparent luminosity, revealing features as small as 520 light-years across

 

This phenomenon — strong gravitational lensing — reveals objects otherwise too faint and distant to be seen.

 

The galaxy cluster MACS 0416 from the Hubble Frontier Fields, with the mass shown in cyan and the magnification from lensing shown in magenta. That magenta-colored area is

where the lensing magnification will be maximized, as there is an area located a specific distance away from any given mass distribution, including galaxies and galaxy clusters,

where the brightness enhancements will be maximized.

 

A decade ago, the Herschel (infrared) and Planck (microwave) observatories combined to identify lensed galaxy candidates.

 

The below image, of one of the galaxy clusters identified by Planck and Herschel, showcases a 2016 follow-up with ALMA at very long wavelengths. The identified marks of A, B,

and C all correspond to the same background galaxy, lensed multiple times by the foreground cluster

 

Follow-up observations, performed with Hubble, at last revealed their details.

Six of the galaxy clusters identified by Planck and Herschel were imaged here by Hubble, showcasing the ultra-distant starburst galaxy PLCK G045.1+61.1 in the lower-left panel

 

Seen here in incredible detail, thanks to the NASA/ESA Hubble Space Telescope, is 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 gravitationally lensed by a cluster of closer galaxies that are also visible.

 

It's a single star-forming galaxy, appearing only 1.9 billion years after the Big Bang.

 

The same image, with the three images of the ultra-distant background galaxy highlighted here. These multiple images have different length light-paths to Earth; if a supernova

goes off in this galaxy, we'll observe its light arriving at three different times

 

Galaxies comparable to the present-day Milky Way are numerous, but younger galaxies that are Milky Way-like are inherently smaller, bluer, more chaotic, and richer in gas in

general than the galaxies we see today. Galaxies from 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 expanding Universe.

 

Using similar techniques, NASA's upcoming James Webb Space Telescope will shatter our earliest galaxy records.

 

As we're exploring more and more of the Universe, we're able to look farther away in space, which equates to farther back in time. The James Webb Space Telescope will take us

to depths, directly, that our present-day observing facilities cannot match, with Webb's infrared eyes revealing the ultra-distant starlight that Hubble cannot hope to see

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