#light year

This beautiful Hubble Space Telescope image is the supernova remnant: the Veil Nebula. It is the remnant of a star that is roughly 20 times as massive as the Sun and it exploded about 10,000 years ago. The Veil Nebula is situated about 2,400 light-years away in the constellation Cygnus.

Hubble images of this nebula were first taken in 1994 and 1997, and again in 2015. This view combines images taken in three different filters, highlighting emission from hydrogen, sulfur, and oxygen atoms. The image shows just a small fraction of the Veil Nebula; if you could see the entire nebula without the aid of a telescope, it would be as wide as six full Moons placed side-by-side.

Although this image captures the Veil Nebula at a single point in time, it helps researchers understand how the supernova remnant evolves over decades. Combining this snapshot with previous Hubble observations, reveals the motion of individual knots and filaments of gas over that span of time, enhancing our understanding of this stunning nebula.

Feynman: When we were talking about the atoms, one of the troubles that people have with the atoms is that they're so tiny, and it's so hard to imagine the scale.

The size of the atoms are in size - compared to an apple, it's the same scale as an apple is to the size of the Earth. And that's a kind of a hard thing to take, and you have to go through all these things all the time, and people find these numbers inconceivable. And I do too.

The only thing you do is you just change your scale. I mean, you're just thinking of small balls, but you don't try to think of exactly how small they are too often! Or you'd get kind of a bit nutty, alright?

But in astronomy, you have the same thing in reverse because the distances to these stars is so enormous, you see. You know that light goes so fast that it only takes a few seconds to go to the moon and back, or it goes around the Earth seven-and-a-half times in a second. And goes for a year, two years, three years before it gets to the nearest other star that there is to us.

But all of our stars are... the stars that are nearby in a great galaxy, a big mass of stars, which is called a galaxy, a group, well this, our galaxy is... what is it? Something like a hundred thousand light years, a hundred thousand years.

And then there's another patch of stars. It takes a million years for the light to get here, going at this enormous rate.

And you just go crazy trying to make too "real" that distance, you have to do everything in proportion. It's easy - you say the galaxies are little patches of stars and they're ten times as far apart as they are big.

So that's an easy picture, you know - he gets it. But you just go to a different scale, that's easier. You know, once in a while you try to come back to... Earth scale to discuss the galaxies but it's kind of hard.

The number of stars that we see at night is about - only about 5,000. But the number of stars in our galaxy, the telescopes have shown when you improve the instrument... Oh! We look at a galaxy. We look at the stars. All the light that we see, the little tiny and influent spreads from the star over this enormous distance of what? Three light years, for the nearest star. On, on, on! This light from the stars spreading, the wavefronts are getting wider and wider, weaker and weaker, weaker and weaker out into all of space, and finally the tiny fraction of it comes in one square, eighth of an inch, tiny little black hole and does something to me, so I know it's there.

Well, to know a little bit more about it, I'd rather gather a little more of this little, this tiny fraction of this front of light, and so I make a big telescope, which is a kind of funnel that the light that comes over this big area - 200 inches across - is very carefully organised, so it's all concentrated back so it can go through a... pupil. Actually, it's better to photograph it, or nowadays they use photo cells, they're a better instrument.

But anyway, the idea of the telescope is to focus the light from a bigger area into a smaller area so that we can see things that are weaker, less light, and in that way we find there's a very large number of stars in the galaxy.

There's so many that if you tried to name them, one a second, naming all the stars in our galaxy, I don't mean all the stars in the universe, just this galaxy here, it takes 3,000 years.

And yet, that's not a very big number. Because if those stars were to drop one dollar bill on the Earth during a year, each star dropping one dollar bill, they might take care of the deficit which is suggested for the budget of the United States.

So you see what kind of numbers we have to deal with!

WASHINGTON, Jan 29 (Reuters) — A batch of newly released images captured by the James Webb Space Telescope show in remarkable detail 19 spiral galaxies residing relatively near our Milky Way, offering new clues on star formation as well as galactic structure and evolution.

The images were made public on Monday by a team of scientists involved in a project called Physics at High Angular resolution in Nearby GalaxieS (PHANGS) that operates across several major astronomical observatories.

The closest of the 19 galaxies is called NGC5068, about 15 million light years from Earth, and the most distant of them is NGC1365, about 60 million light years from Earth.

A light year is the distance light travels in a year, 5.9 trillion miles (9.5 trillion km).

The James Webb Space Telescope (JWST) was launched in 2021 and began collecting data in 2022, reshaping the understanding of the early universe while taking wondrous pictures of the cosmos.

The orbiting observatory looks at the universe mainly in the infrared.

The Hubble Space Telescope, launched in 1990 and still operational, has examined it primarily at optical and ultraviolet wavelengths.

Spiral galaxies, resembling enormous pinwheels, are a common galaxy type. Our Milky Way is one.

The new observations came from Webb's Near-Infrared Camera (NIRCam) and Mid-Infrared Instrument (MIRI).

They show roughly 100,000 star clusters and millions or perhaps billions of individual stars.

"These data are important as they give us a new view on the earliest phase of star formation," said University of Oxford astronomer Thomas Williams, who led the team's data processing on the images.

"Stars are born deep within dusty clouds that completely block out the light at visible wavelengths - what the Hubble Space Telescope is sensitive to - but these clouds light up at the JWST wavelengths.

We don't know a lot about this phase, not even really how long it lasts, and so these data will be vital for understanding how stars in galaxies start their lives," Williams added.

About half of spiral galaxies have a straight structure, called a bar, coming out from the galactic center to which the spiral arms are attached.

"The commonly held thought is that galaxies form from the inside-out, and so get bigger and bigger over their lifetimes.

The spiral arms act to sweep up the gas that will form into stars, and the bars act to funnel that same gas in towards the central black hole of the galaxy," Williams said.

The images let scientists for the first time resolve the structure of the clouds of dust and gas from which stars and planets form at a high level of detail in galaxies beyond the Large Magellanic Cloud and Small Magellanic Cloud, two galaxies considered galactic satellites of the sprawling Milky Way.

"The images are not only aesthetically stunning, they also tell a story about the cycle of star formation and feedback, which is the energy and momentum released by young stars into the space between stars," said astronomer Janice Lee of the Space Telescope Science Institute in Baltimore, principal investigator for the new data.

"It actually looks like there was explosive activity and clearing of the dust and gas on both cluster and kiloparsec (roughly 3,000 light years) scales.

The dynamic process of the overall star formation cycle becomes obvious and qualitatively accessible, even for the public, which makes the images compelling on many different levels," Lee added.

Webb's observations build on Hubble's.

"Using Hubble, we would see the starlight from galaxies, but some of the light was blocked by the dust of galaxies," University of Alberta astronomer Erik Rosolowsky said.

"This limitation made it hard to understand parts of how a galaxy operates as a system. With Webb's view in the infrared, we can see through this dust to see stars behind and within the enshrouding dust."

Light is fast, but space distances are vast.