Are You Guys Aware Of Chimney Swifts??

Meet NGC 2841

Location: In the constellation Ursa Major

Type: Flocculent spiral galaxy

Discovered by: William Herschel

NGC 2841 is a beautiful example of a flocculent spiral galaxy – a type with discontinuous, featherlike, and patchy arms. A bright cusp of starlight distinguishes the galaxy's center from the dust lanes that outline the group of almost white middle-aged stars. The far younger blue stars trace the spiral arms.

Find out more information about NGC 2841 here.

Right now, the Hubble Space Telescope is exploring #GalaxiesGalore! Find more galaxy content and spectacular new images by following along on Hubble’s Twitter, Facebook, and Instagram.

Credit: NASA, ESA, and the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration; Acknowledgment: M. Crockett and S. Kaviraj (Oxford University, UK), R. O'Connell (University of Virginia), B. Whitmore (STScI), and the WFC3 Scientific Oversight Committee

Daily Butterfly facts

Butterflies can’t fly if they’re cold

Figured out how to post the actual videos!

I wasn’t happy with the painting explanation I threw together the other day and I keep thinking of steps/important notes I should have included, so I made this more detailed version today! This is more or less how I paint, and the main things I keep in mind when I paint. Originally I was just going to “add a few more details” to the original tutorial, but I kept thinking of stuff and went a little bit nuts trying to phrase everything in a way that makes sense.

there are many incredible tutorials about digital (and traditional) painting, color theory, light and shadow, etc out there– I want to urge anyone interested in learning more about this stuff to go seek out professional advice! Painting is really, really complicated, and I’m absolutely still learning how it works and how to do it good. This is just m’thoughts and some images to go with them.

Deltoid animated study, this muscle helps raising the arm!

Symmetry Magazine

How JWST will test models of cold dark matter

By Madeleine O’Keefe

Two projects in JWST’s first observation cycle will probe the nature of dark matter.

On Christmas morning of 2021, an Ariane 5 CEA rocket blasted off from Kourou, French Guinea. It carried with it the largest and most sophisticated space telescope ever built: the James Webb Space Telescope.

Since then, JWST has reached its orbit about 1 million miles from Earth, unfurled its tennis-court-sized sunshield, and aligned its 18 hexagonal mirror segments. The telescope’s first images are expected by summer.

Over the next decade, JWST will make cutting-edge observations to help scientists answer myriad outstanding questions in astronomy—including questions about the nature of dark matter.

Hot, warm or cold Dark matter is an enigmatic substance that scientists believe accounts for 85% of matter in the universe. But so far it has not been observed directly; scientists can infer dark matter’s presence only by observing its gravitational effects on normal matter.

Different theories posit different types of dark-matter particles. Dark-matter candidates considered “hot” or “warm” are particles that would have moved so quickly in the early universe that gravity would not have been able to confine them. On the other hand, dark-matter candidates considered “cold” are thought to have moved so slowly that gravity would have formed them into small dark-matter structures that eventually would have coalesced into larger, “clumpy” ones.

“Decades’ worth of computer simulations have tested how structure forms and grows under the hypothesis of cold dark matter,” says Matthew Walker, an associate professor of physics at Carnegie Mellon University.

Cold dark-matter simulations show dark matter clumping into small blobs, which encounter other blobs and merge together, continually snowballing until large structures like the Milky Way are formed. These gravitationally bound blobs of dark matter are known as halos.

JWST can see your halo Anna Nierenberg, assistant professor of physics at University of California, Merced, was awarded 39 hours of observing time during JWST’s Cycle 1 to look for small dark-matter halos.

Many models, including the baseline dark-matter model, predict the existence of small (107 solar mass) halos that do not actually contain galaxies. Such a halo would “just be a blob of dark matter” with no stars inside it, Nierenberg says.

If there are no stars within these blobs of invisible material, how can we even try to detect them? Nierenberg and her team of nearly 20 scientists in the US, Canada, the United Kingdom, Switzerland, Spain, Belgium and Chile are using a phenomenon called gravitational lensing.

Born of Albert Einstein’s theory of general relativity, gravitational lensing says that matter bends spacetime and, subsequently, any light that encounters it. If light from a distant source travels through the universe toward Earth and passes by a massive object—such as a blob of dark matter—the light will be warped around it. If the in-between object is massive enough, the light is deflected in such a way that we’ll see up to four images of the light source appearing around the mass.

Nierenberg’s group will measure the number of small dark-matter halos by observing a sample of quasars (supermassive black holes at cosmological distances surrounded by dusty accretion disks) that have been gravitationally lensed. Detecting small halos would be a triumph for the cold dark-matter theory; conversely, not detecting small halos would imply that cold dark matter does not exist.

Because the light from these quasars must travel a great distance in an ever-expanding universe, it is stretched along the way, pulling its wavelengths into the infrared range. The mid-infrared wavelengths they are observing are almost impossible to see with ground-based telescopes. “We’re going to be observing with absolute reddest bands that JWST can accommodate,” Nierenberg says.

These wavelengths cannot be observed by the Hubble Space Telescope, which studies gravitational lensing at visible wavelengths. And older space-based telescopes that can see in the mid-infrared don’t have the resolution to separate the different lenses. Making these observations in mid-IR requires the high spatial resolution that only the JWST can provide, Nierenberg says.

Daniel Gilman, a postdoc at the University of Toronto and one of Nierenberg’s co-investigators, says, “The kind of data that we can get with JWST is unique and much more powerful or constraining than the kind of data that we could get with Hubble or from the ground.”

Nierenberg says, “I really believe that this is going to be a huge scientific step forward.”

Looking far and wide Walker is leading another dark-matter project in JWST’s Cycle 1, but his group didn’t apply for observing time. Instead, they are using data that JWST is collecting for other programs.

Walker’s group’s “archival research” is looking inside dwarf galaxies to find wide binary stars, systems of two stars orbiting each other at relatively large distances (on the order of one parsec, slightly less than the distance between the sun and our closest neighbor, Proxima Centauri).

“Because [wide binary stars] are so far apart, they’re very fragile systems,” says Walker. “If, say, a little dark-matter halo were to fly past a wide binary-star system, it could exchange energy with either or both of the stars in that system. And it just takes a small fraction of a fraction of a percent increase in the energy of either star to rip the pair apart.”

If Walker’s team finds wide binary stars, “we can be reasonably confident that those sub-galactic cold dark matter halos don’t exist,” he says. “And that, then, would be a real problem for the cold dark-matter model in general.”

That’s what Katharine Lee, a junior physics major at Carnegie Mellon in Walker’s group, likes about the project. “I particularly think this research is really interesting because the current framework for what we think of as the structure of dark matter is the cold dark-matter model, and the research that Professor Walker’s doing could potentially invalidate that.”

If the group did not find wide binary stars, it could be a sign that they were destroyed by dark matter. But it would not prove that they were destroyed—they may just have never formed in these dwarf galaxies in the first place.

Walker says that JWST is an ideal tool for this search because of its “exquisite sensitivity to faint objects,” as well as the telescope’s abilities to take high-quality images and distinguish pairs of sources at very small separations. And thanks to its 21-foot-diameter primary mirror, JWST will see farther than any other telescope ever built.

“I think JWST is going to give us a new and really powerful angle,” says Jorge Peñarrubia, a professor at the University of Edinburgh and one of Walker’s co-investigators. “But even if that fails, we’ll find other ways.”

Indeed, there are many other techniques that scientists use to search for dark matter, including direct searches by physics experiments. And both Nierenberg and Walker are using gravitational lensing and wide binary-star methods on data from the Hubble Space Telescope while they wait for JWST to open its eyes.

Future JWST science programs might further explore the mysteries of dark matter, whether through gravitational lensing or perhaps by observing statistics of galaxy evolution that scientists can then compare to dark-matter theories.

“We don’t lack theories of what dark matter could be. There are a lot of them,” Gilman says. “What we lack are observations that wield a lot of constraining power over these theories. And that’s something that JWST is going to give us.”

Illustration by Sandbox Studio, Chicago with Olena Shmahalo

A friend of mine shared this fantastic resource over Discord, so did a few studies in-between working on homework!

some vaguely coherent notes on owl facial discs because they were the hardest part of the bird for me to figure out and if this helps at least one person then I consider that an epic win

Photos: Barn Owl, Long-eared Owl

While it is true that photons have no mass, it is also true that we see light bend around sources with high mass due to gravity. This is not because the mass pulls on the photons directly, but instead because the mass warps the space-time through which the photons travel. Imagine a bowling ball on a mattress. The ball is a massive object — say, the Sun — and the mattress represents space-time, in which it sits. (Of course, space-time is four-dimensional, but it’s a bit harder to imagine that!) When you place the bowling ball on the mattress, it deforms the surface. If a grid were drawn on the mattress, you would see the grid deform, so the straight lines of the boxes were no longer straight. The same is true for a star sitting in space-time — the star deforms space-time around it, causing it to curve toward the star. Now imagine a marble; this represents a photon. If you roll the marble in a straight line on the mattress and it comes too close to the bowling ball, the marble will curve because the mattress it’s traveling on dips and curves around the bowling ball. This is what happens to light traveling through space: When it comes too close to a massive object, it encounters warped space-time and curves not because it’s being pulled by gravity, but because the space-time it’s traveling through is curved, so its “straight” path becomes a curved, bent one.

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