- 3284 - EINSTEIN RING - distance to far away galaxies? The circle surrounding a constellation of stars is called an “Einstein ring” after the famous physicist who predicted its existence.
--------------- 3284 - EINSTEIN RING - distance to far away galaxies?
- The Einstein ring is actually a light smear created by a lensing effect that occurs when a foreground object with strong gravity magnifies the light of a more distant galaxy behind it.
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- The galaxy inside the ring is as it was 9 billion years old, when the universe was only about one-third its present age of 13.8 billion years.
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- The detection of molecular gas, of which new stars are born, allowed astronomers to calculate the precise redshift and thus the galaxy distance
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- 13.8 billion years ago was a time when the universe was going through a 'baby boom,' forming thousands of stars at a prolific rate.
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- In the brightest and very dusty early galaxies saw stars being born at a rate a thousand times faster than occurs within our own galaxy.
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- Astronomers are learning even more by observing quasars in the early Universe. They have found a relationship between X-ray and UV luminosities. This relation does not evolve with redshift and therefore astronomers can use the same relation just using fluxes to compute the distance of the objects.
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- Whatever quasars are, they’re an exotic feature of the early Universe that we don’t see in the nearby cosmos today. The first quasar discovered was “3C 273” in 1963. With a high redshift (z = 0.158). Astronomers knew they were looking at something extremely distant and therefore intrinsically luminous.
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- To give you some idea just how bright 3C 273 actually is, it has an absolute magnitude value of -27. If you placed it at a distance of 10 parsecs away, 32.6 lightyears away , it would compete with the Sun in the sky.
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- The first ‘rung’ on the cosmic distance ladder is “parallax“, using observations from two different points in space and basic trigonometry to gauge distance. Using the Earth’s orbit as a baseline is also the basis for the parsec which is a measure of distance, 3.26 light-years long.
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- But parallax calculations will only get you so far. The triangle becomes nearly a straight line. The next yardstick out was discovered by astronomer Henrietta Swan Levitt while examining variable stars in the Small Magellanic cloud in 1912. She noticed that a particular type of star known as a Cepheid variable pulses in a fashion that’s directly related to its luminosity.
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- For larger distances, brighter standard candles are needed. Astronomers use Type IA supernovae, as they flare and fade in a predictable fashion. Over the immense distances of hundreds of millions of light-years, cosmic expansion and spectroscopic redshift (noted as z) comes into play.
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- Hubble’s Law correlates velocity as being proportional to distance due to the expansion of the Universe: the higher the redshift, the more distant the object.
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- Type IA supernovae allow calculations back to about three billion years after the Big Bang. Quasars as standard candles would be good to just 700 million years after the Big Bang.
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- Quasars have another advantage, as hundreds of thousands of them have been discovered in recent years. As a standard candle, they provide not only a good overlap with more distant Type 1A supernovae, but are also a good backup check for distance, as they are separately distinct cosmological processes.
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- You can observe “quasar 3C 273” from your driveway with a good-sized telescope. At magnitude +12.9 it won’t look like much more than a nondescript faint star. It is amazing to think that you’re seeing photons that left their source 2.4 billion years ago.
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- Just 50 years since discovery, quasars have gone from mysterious objects to key standard candles for probing the early Universe. A new measurement is coming from gamma ray bursts.
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- Gamma-ray bursts (GRBs) are the brightest, most energetic blasts of light in the universe. Released by an immense cosmic explosion, a single GRB is capable of shining about a million trillion times brighter than Earth's sun.
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- GRBs are usually billions of light-years from Earth. Sometimes, a GRB's home galaxy is so far-flung that the burst's light appears to come from nowhere at all, briefly blipping out of the black, empty sky and vanishing seconds later.
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- These "empty-sky" gamma-ray bursts have presented an ongoing cosmic mystery for more than 60 years. But a new study, published September 15, 2021, offers a compelling mathematical explanation for the powerful bursts' origins
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- Studying the interactions between gamma rays and cosmic rays found that all those nebulous empty-sky bursts could be the results of massive stellar explosions in the disks of distant galaxies.
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- It is these star-forming galaxies that produce these gamma-ray radiation outbursts. One explanation for these outbursts is that the rays occur when gas falls into the supermassive blackholes that sit at the centers of all galaxies in the universe.
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- As gas particles get sucked into the blackhole, a small fraction escape and instead radiate in large, near-light-speed jets of matter. These powerful jets could be responsible for gamma-ray bursts.
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- Another explanation points to stellar explosions called supernovas. When large stars run out of fuel and erupt in these violent supernovas, they can send nearby particles blasting away at near-light speed. These highly energetic particles, i.e. cosmic rays, may then collide with other particles sprinkled through the gassy hinterland between stars, producing gamma-rays.
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- The astronomer’s calculations fit with the observations that supernovas in star-forming galaxies could explain most, if not all, empty-sky GRBs.
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- Blackholes are probably still responsible for some of the gamma-rays that our satellites pick up. But when it comes to the mysterious empty-sky GRBs, the blackholes are simply not necessary; exploding stars in faraway corners of the universe are sufficient to explain the phenomenon.
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- September 25 , 2021 EINSTEIN RING - distance to far away galaxies? 3284
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