The Venerable Hubble Space Telescope Keeps Delivering

The Hubble Space Telescope is amazing! It's still going strong more than 34 years after it was launched. This Hubble image showcases a nearly edge-on view of the lenticular galaxy NGC 4753. ESA/Hubble & NASA, L. Kelsey

The world was much different in 1990 when NASA astronauts removed the Hubble Space Telescope from Space Shuttle Discovery’s cargo bay and placed it into orbit. The Cold War was ending, there were only 5.3 billion humans, and the World Wide Web had just come online.

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Feast Your Eyes on 19 Face-On Spiral Galaxies Seen by Webb

These Webb images are part of a large, long-standing project, the Physics at High Angular resolution in Nearby GalaxieS (PHANGS) program, which is supported by more than 150 astronomers worldwide. Before Webb took these images, PHANGS was already brimming with data from NASA’s Hubble Space Telescope, the Very Large Telescope’s Multi-Unit Spectroscopic Explorer, and the Atacama Large Millimeter/submillimeter Array, including observations in ultraviolet, visible, and radio light. Webb’s near- and mid-infrared contributions have provided several new puzzle pieces. Image Credit: NASA/ESA/CSA

If you’re fascinated by Nature, these images of spiral galaxies won’t help you escape your fascination.

These images show incredible detail in 19 spirals, imaged face-on by the JWST. The galactic arms with their multitudes of stars are lit up in infrared light, as are the dense galactic cores, where supermassive black holes reside.

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There Aren’t Many Galaxies Like The Milky Way Nearby. Now We Know Why

Antennas of the Very Large Array against the Milky Way. Credit: NRAO/AUI/NSF/Jeff Hellerman

The Milky Way is a barred spiral galaxy, maybe even a grand design spiral galaxy. We can’t be sure from our vantage point. But one thing is certain: there aren’t many disk galaxies like it in our part of the Universe called the supergalactic plane.

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What Does the Milky Way Look Like?

Artist's impression of the Milky Way Galaxy. Credit: ESO

Beginning in 1610, when famed Renaissance polymath Galileo Galilei observed the night sky using a telescope of his own manufacture, astronomers gradually realized that our Solar System is part of a vast collection of stars known today as the Milky Way Galaxy. By the 20th century, astronomers had a good idea of its size and structure, which consisted of a central “bulge” surrounded by an extended disk with spiral arms. Despite all we’ve learned, determining the true morphology of the Milky Way has remained a challenge for astronomers.

Since we, the observers, are embedded in the Milky Way’s disk, we cannot see through the center and observe what’s on the other side. Using various methods, though, astronomers are getting closer to recreating what a “birds-eye” view of the galaxy would look like. For instance, a team of researchers from the Chinese Academy of Sciences (CAS) used the precise locations of very young objects in our galaxy (for the first time) to measure the morphology of the Milky Way. This revealed a multiple-arm morphology consisting of two symmetrical arms in the inner region and many irregular ones in the outer region.

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Gaze Into the Heart of a Grand Spiral Galaxy

Image Credit: NASA, ESA, A. Filippenko (University of California - Berkeley), and D. Sand (University of Arizona); Image Processing: G. Kober (NASA Goddard/Catholic University of America)

Here’s Hubble doing what Hubble does best.

Some of the Hubble Space Telescope’s most famous and stunning images are of distant galaxies, and this one is drop-dead gorgeous too.

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Galaxies Like the Milky Way are the Best for Life

The core of the Milky Way. Credit: NASA/JPL-Caltech/S. Stolovy (SSC/Caltech)

Scientists have speculated that given the sheer number of galaxies in our Universe – modern estimates are as high as 2 trillion – that there must be infinite opportunities for life to emerge. It has also been theorized that galaxies (like stars) have habitable zones, where star systems located too close to the core or too far out in the spiral arms will be exposed to too much radiation for life to emerge.

But are certain types of galaxies more likely to produce intelligent life? Not that long ago, scientists believed that giant elliptical galaxies – which are substantially larger than spiral galaxies (like the Milky Way) – are a far more likely place to find advanced civilizations. But according to new research from the University of Arkansas, these galaxies may not be the cradles of civilization they were previously thought to be.

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You’re Looking at Spiral Galaxies, Already Forming When the Universe was Just a Baby

Credit: Michele Ginolfi (ALPINE collaboration); ALMA(ESO/NAOJ/NRAO); NASA/JPL-Caltech/R. Hurt (IPAC)

One of the most exciting developments in astronomy today is the way that advanced arrays and techniques are letting astronomers see farther back in time to the earliest periods of the Universe. In so doing, astronomers hope to get a closer at the earliest galaxies to learn more about how and when they first emerged – which can tell us a great deal more about their subsequent evolution.

This was the purpose of the ALMA Large Program to INvestigate C+ at Early times (ALPINE), a multiwavelength survey that examined galaxies that were around when the Universe was less than 1.5 billion years old. With funding provided by NASA and the European Southern Observatory (ESO), the ALPINE collaboration analyzed this data and learned some interesting things about the early evolution of galaxies.

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Perfect Example of a Barred Spiral Galaxy, Seen Face On. This is What Our Milky Way Might Look Like

This striking image was taken by the NASA/ESA Hubble Space Telescope’s Wide Field Camera 3, a powerful instrument installed on the telescope in 2009. WFC3 is responsible for many of Hubble’s most breathtaking and iconic photographs, including Pictures of the Week. Shown here, NGC 7773 is a beautiful example of a barred spiral galaxy. A luminous bar-shaped structure cuts prominently through the galaxy's bright core, extending to the inner boundary of NGC 7773's sweeping, pinwheel-like spiral arms. Astronomers think that these bar structures emerge later in the lifetime of a galaxy, as star-forming material makes its way towards the galactic centre — younger spirals do not feature barred structures as often as older spirals do, suggesting that bars are a sign of galactic maturity. They are also thought to act as stellar nurseries, as they gleam brightly with copious numbers of youthful stars. Our galaxy, the Milky Way, is thought to be a barred spiral like NGC 7773. By studying galactic specimens such as NGC 7773 throughout the Universe, researchers hope to learn more about the processes that have shaped — and continue to shape — our cosmic home.

The Hubble Space Telescope has given us a beautiful image of the barred spiral galaxy NGC 7773. This is a classic galaxy of this type, and highlights the bright bar of concentrated stars that anchors the galaxy’s stately spiral arms. It was captured with the Hubble’s workhorse Wide Field Camera 3 (WFC3.)

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Why Do Galaxies Have Arms?

Why Do Galaxies Have Arms?

Spiral galaxies get their name because of their beautiful spiral shape and iconic arms. But why do galaxies have these spiral shapes, and what causes the arms?

Galaxies are some of the most beautiful and inspiring structures in the Universe. As you know, they aren’t solid disks, they’re a gigantic spill of individual stars webbed together by gravity. There are a few rough fundamental shapes that a galaxy can have, and the bulk of these are some variation of a spiral. Each one with twisting arms of stars reaching tens of thousands of light years in every direction along a plane, out from a galactic core.

So what gives them this characteristic spiral shape? Earliest galaxies didn’t have clearly defined spiral arms. They were either two-armed or, had thick irregular chaotic woolly arms with star forming clumps. After 3.6 billion years, however, the chaos had settled down into the shapes we see today. But it took until the Universe was 8 billion years old for these modern multi-armed spirals, like the Milky Way or Andromeda to appear.

So where did they come from? These arms are in fact density waves passing through the galaxy, with stars moving in and out of the waves. The arms themselves aren’t permanent structures made of the same clumps of stars.

Imagine driving down a highway and people are slowing down to gape slack-jawed a crashed alien saucer. Cars will slow down as they reach the saucer and form a clump, and then the car in the lead of the clump will accelerate and proceed down the highway as other cars progress through the clump to take their place.

This is a great analogy for movement in a galaxy. As a density wave approaches, stars accelerate towards it. Then they slow down as they move away from it. Just like a comet falling into the gravity well of the Sun. And when the density wave moves through an area, it kicks off an era of star formation. So the material of the galaxy is being constantly stirred and new stars are born as a density wave makes its way through the galaxy.

Six spectacular spiral galaxies are seen in a clear new light in images from ESO’s Very Large Telescope (VLT) at the Paranal Observatory in Chile. Credit: ESO
Six spectacular spiral galaxies are seen in a clear new light in images from ESO’s Very Large Telescope (VLT) at the Paranal Observatory in Chile. Credit: ESO

When you picture this, keep in mind that stars closer to the core of the galaxy orbit faster than the spiral arm, and the stars further out go more slowly. Our galaxy, the Milky Way takes about 240 million years to complete a full rotation. But we pass through a major spiral arm every 100 million years or so, remaining in the higher density region for about 10 million years. Astronomers have only recently figured out why these arms exist in the first place.

Originally, they suspected it might be like a garden sprinkler, with material fountaining out from the center of the galaxy, or channeled by magnetic fields. They also thought that the arms might be transient features. Appearing and disappearing over time. But new evidence and simulations show they’re long lasting, they believe the arms themselves form as a result of giant molecular clouds of hydrogen. These clouds initiate the arms and keep the shape sustained over billions of years.

What do you think? What’s your favorite spiral galaxy? Tell us in the comments below.

‘Green Valley’ Of Galaxies Shows Off Gas And Star Formation

M33, the Triangulum Spiral Galaxy, seen here in a 4.3 hour exposure image. Astronomers used JWST to examine a section of its south spiral arm to search out and find nearly 800 newly forming stars. Credit and copyright: John Chumack.
M33, the Triangulum Spiral Galaxy, seen here in a 4.3 hour exposure image. Astronomers used JWST to examine a section of its south spiral arm to search out and find nearly 800 newly forming stars. Credit and copyright: John Chumack.

We keep saying this: the universe is more complex than it appears. Conventional thinking in galaxy research postulates that spiral galaxies have star-forming areas, while ellipticals do not due to a lack of gas. While this thinking has been debunked, there’s now emerging research showing a “green valley” of galaxies somewhat in between these two types.

Basically, the research (which includes participation from citizen scientists in the Galaxy Zoo project) is showing that there are two different populations of “green” galaxies, between ellipticals and spirals. Further, what happens to star formation based upon gas in the area.

“In this paper, we take a look at the most crucial event in the life of a galaxy: the end of star formation. We often call this process ‘quenching’ and many astrophysicists have slightly different definitions of quenching. Galaxies are the place where cosmic gas condenses and, if it gets cold and dense enough, turns into stars. The resulting stars are what we really see as traditional optical astronomers,” wrote Kevin Schawinski, a Ph.D. student at the University of Oxford who is on the Galaxy Zoo team, in a blog post.

“Not all stars shine the same way though: stars much more massive than our sun are very bright and shine in a blue light as they are very hot. They’re also very short-lived. Lower mass stars take a more leisurely pace and don’t shine as bright (they’re not as hot). This is why star-forming galaxies are blue, and quiescent galaxies (or ‘quenched’ galaxies) are red: once star formation stops, the bluest stars die first and aren’t replaced with new ones, so they leave behind only the longer-lived red stars for us to observe as the galaxy passively evolves.”

You can read more information in the blog post. The study, which has been accepted for publication in the Monthly Notices of the Royal Astronomical Society, is available on preprint site Arxiv.