Why couldn’t early astronomers tell the difference between single stars and entire galaxies?

Why couldn’t early astronomers tell the difference between single stars and entire galaxies?

When ancient scholars gazed at the bright band of the Milky Way crossing the pitch-dark ancient sky, they had no idea what they were looking at. Without telescopes, they couldn’t distinguish individual stars in what we know today is the galaxy’s disc viewed from within.

Why the first stars and galaxies are difficult to observe?

Making things even more difficult, the fog of neutral hydrogen gas that filled the universe when the very first stars were forming would have absorbed their ultraviolet light. Until the ultraviolet radiation ionized enough atoms to allow light to pass through, our view of the first stars would be blocked.

Why is it so difficult to study the center of our galaxy?

Yet, whatever has happened in the center of our own galaxy is hard to study, despite its relative proximity to Earth, because, as Wang explains, it is obscured by a dense fog of gas and dust. Researchers simply can’t see the center, even with an instrument as powerful as the famous Hubble Space Telescope.

Why did the galaxy stop making stars?

The cold gas that coalesces to form stars might escape from galaxies by several means, blown away by black holes or supernovae. And there’s an even simpler possibility, that galaxies simply quiet down when they’ve used up all the raw materials for creating stars.

Why would it have been hard for the first generation of stars to have planets?

The first generation of stars, known as Population III stars, fails on this account. We need for stars to at least contain some metals (heavy elements beyond helium), or they won’t live long enough for a planet to become hospitable to life, which already puts us some 250 million years after the Big Bang.

How did astronomers discover that there are other galaxies beyond the Milky Way?

Hubble used the P-L relation to find the distance to the Cepheid he was studying in M31, and proved that it was located outside of our own Galaxy. This finally ended the debate on the nature of the spiral nebulae – they were indeed distant galaxies like our Milky Way.

Why is it difficult to observe stars forming?

Observing star formation is difficult, because the dust is not transparent to visible light. It is, however, possible to observe these dark stellar nurseries using radio waves, because radio waves travel freely down to us and our radio telescopes. Stars, like our own Sun, have not always been around.

Why it is so difficult to determine the shape of our galaxy?

Astronomers can only infer its presence from the motions of stars in the galaxy, which makes it difficult to determine a precise shape.

Why would it be difficult to detect galaxies far away?

As it expands, light propagating through space ‘stretches’ more to the red end of the visible spectrum. For distant galaxies this effectively means that the visible light from them has shifted far enough to be infrared and invisible by the time it gets here.

Why is it difficult for astronomers to see the Centre of the Milky Way galaxy?

At the very centre of the Galaxy lies a remarkable object—a massive black hole surrounded by an accretion disk of high-temperature gas. Neither the central object nor any of the material immediately around it can be observed at optical wavelengths because of the thick screen of intervening dust in the Milky Way.

Why is our galaxy the Milky Way in some ways harder to study than many other galaxies?

We’re stuck deep within the Milky Way, so it’s impossible to get a view of the galaxy from the outside. All we can do is peer out, and look at other galaxies to give us an idea of how our own works.

Why were astronomers having a tough time seeing the center of our Milky Way galaxy?

Unfortunately, it has been very difficult for astronomers to study the center of the Milky Way because of how bright and densely packed the region is, which makes it difficult to discern individual stars and clusters.

Can you have a galaxy without stars?

Astronomers have found six possible “dark galaxies” – galaxies that instead of being filled with an abundance of stars, don’t seem to have many, if any, at all.

Can a star create a galaxy?

After the Big Bang, space was made up almost entirely of hydrogen and helium. Some astronomers think that gravity pulled dust and gas together to form individual stars, and those stars drew closer together into collections that ultimately became galaxies.

Is there a galaxy without a star?

Dark galaxies, as they are fittingly called, are still in the realm of hypothesis, but observational evidence is increasingly weaving them into reality. Composed of only hydrogen gas, dust, and dark matter, and without visible stars, they are nearly impossible to detect.

How did early astronomers distinguish between stars and planets?

Early astronomers were able to tell the difference between planets and stars because planets in our Solar System appear to move in complicated paths across the sky, but stars don’t. That is, if you observe the sky night after night, the stars will all appear in fixed positions with respect to each other.

How do you tell the difference between a star and a galaxy?

To distinguish galaxies from stars, you can use the spectrum. Roughly, stars have a black-body like spectrum with features depending on the absorption and emission on the line of sight and in the chromosphere of the star. Galaxies on the other hand of a spectrum that is the composite of tons of stars.

Why was the early universe impossible to see?

About 300,000 years after the big bang, the universe was like a smoke-filled chamber from which light could not escape. By the time the universe was a billion years old, the smoke—actually a gas of light-trapping hydrogen—had cleared almost entirely, allowing stars and galaxies to become visible.

Are there single stars between galaxies?

Although stars cannot form in the voids between galaxies (since the density of matter is far too low), there are in fact large numbers of ‘intergalactic stars’. It has been estimated, for example, that 10 per cent of the mass of the Virgo galaxy cluster is in the form of these stellar interlopers.