Astronomy Picture of the Day (APOD)

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NGC 2170: Angel Nebula Still Life



"Explanation: Is this a painting or a photograph? In this classic celestial still life composed with a cosmic brush, dusty nebula NGC 2170, also known as the Angel Nebula, shines near the image center. Reflecting the light of nearby hot stars, NGC 2170 is joined by other bluish reflection nebulae, a red emission region, many dark absorption nebulae, and a backdrop of colorful stars. Like the common household items that still life painters often choose for their subjects, the clouds of gas, dust, and hot stars featured here are also commonly found in this setting -- a massive, star-forming molecular cloud in the constellation of the Unicorn (Monoceros). The giant molecular cloud, Mon R2, is impressively close, estimated to be only 2,400 light-years or so away. At that distance, this canvas would be over 60 light-years across."

Source: APOD 2019 August 26

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M31: The Andromeda Galaxy



"Explanation: How far can you see? The most distant object easily visible to the unaided eye is M31, the great Andromeda Galaxy, over two million light-years away. Without a telescope, even this immense spiral galaxy appears as an unremarkable, faint, nebulous cloud in the constellation Andromeda. But a bright yellow nucleus, dark winding dust lanes, luminous blue spiral arms, and bright red emission nebulas are recorded in this stunning six-hour telescopic digital mosaic of our closest major galactic neighbor. While even casual skygazers are now inspired by the knowledge that there are many distant galaxies like M31, astronomers seriously debated this fundamental concept only 100 years ago. Were these "spiral nebulae" simply outlying gas clouds in our own Milky Way Galaxy or were they "island universes" -- distant galaxies of stars comparable to the Milky Way itself? This question was central to the famous Shapley-Curtis debate of 1920, which was later resolved by observations favoring Andromeda being just like our Milky Way Galaxy -- a conclusion making the rest of the universe much more vast than many had ever imagined."

Source: APOD 2019 September 9

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IC 1805: The Heart Nebula



"Explanation: What energizes the Heart Nebula? First, the large emission nebula dubbed IC 1805 looks, in whole, like a human heart. The nebula glows brightly in red light emitted by its most prominent element: hydrogen. The red glow and the larger shape are all powered by a small group of stars near the nebula's center. In the center of the Heart Nebula are young stars from the open star cluster Melotte 15 that are eroding away several picturesque dust pillars with their energetic light and winds. The open cluster of stars contains a few bright stars nearly 50 times the mass of our Sun, many dim stars only a fraction of the mass of our Sun, and an absent microquasar that was expelled millions of years ago. The Heart Nebula is located about 7,500 light years away toward the constellation of Cassiopeia. Coincidentally, a small meteor was captured in the foreground during imaging and is visible above the dust pillars. At the top right is the companion Fishhead Nebula."

Source: APOD 2019 September 11

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The Tulip in the Swan



"Explanation: Framing a bright emission region, this telescopic view looks out across a pretty field of stars along the plane of our Milky Way Galaxy, toward the nebula rich constellation Cygnus the Swan. Popularly called the Tulip Nebula, the reddish glowing cloud of interstellar gas and dust is also found in the 1959 catalog by astronomer Stewart Sharpless as Sh2-101. About 8,000 light-years distant and 70 light-years across the complex and beautiful nebula blossoms near the center of this composite image. Ultraviolet radiation from young energetic O stars at the edge of the Cygnus OB3 association, ionizes the atoms and powers the emission from the Tulip Nebula."

Source: APOD 2019 September 21

[Stranger]

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The Hydrogen Clouds of M33



"Explanation: Gorgeous spiral galaxy M33 seems to have more than its fair share of glowing hydrogen gas. A prominent member of the local group of galaxies, M33 is also known as the Triangulum Galaxy and lies a mere 3 million light-years away. The galaxy's inner 30,000 light-years or so are shown in this magnificent 25 panel telescopic mosaic. Based on image data from space and ground-based telescopes, the portrait of M33 shows off the galaxy's reddish ionized hydrogen clouds or HII regions. Sprawling along loose spiral arms that wind toward the core, M33's giant HII regions are some of the largest known stellar nurseries, sites of the formation of short-lived but very massive stars. Intense ultraviolet radiation from the luminous, massive stars ionizes the surrounding hydrogen gas and ultimately produces the characteristic red glow. To enhance this image, broadband data was used to produce a color view of the galaxy and combined with narrowband data recorded through a hydrogen-alpha filter. That filter transmits the light of the strongest visible hydrogen emission line."

Source: APOD 2019 October 3

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Dark Seahorse in Cepheus



"Explanation: Light-years across, this suggestive shape known as the Seahorse Nebula appears in silhouette against a rich, luminous background of stars. Seen toward the royal northern constellation of Cepheus, the dusty, obscuring clouds are part of a Milky Way molecular cloud some 1,200 light-years distant. It is also listed as Barnard 150 (B150), one of 182 dark markings of the sky cataloged in the early 20th century by astronomer E. E. Barnard. Packs of low mass stars are forming within from collapsing cores only visible at long infrared wavelengths. Still, colorful stars in Cepheus add to the pretty, galactic skyscape."

Source: APOD 2019 October 24

[isis]

Gravity's Grin
https://apod.nasa.gov/apod/ap191026.html
Explanation: Albert Einstein's general theory of relativity, published over 100 years ago, predicted the phenomenon of gravitational lensing. And that's what gives these distant galaxies such a whimsical appearance, seen through the looking glass of X-ray and optical image data from the Chandra and Hubble space telescopes. Nicknamed the Cheshire Cat galaxy group, the group's two large elliptical galaxies are suggestively framed by arcs. The arcs are optical images of distant background galaxies lensed by the foreground group's total distribution of gravitational mass. Of course, that gravitational mass is dominated by dark matter. The two large elliptical "eye" galaxies represent the brightest members of their own galaxy groups which are merging. Their relative collisional speed of nearly 1,350 kilometers/second heats gas to millions of degrees producing the X-ray glow shown in purple hues. Curiouser about galaxy group mergers? The Cheshire Cat group grins in the constellation Ursa Major, some 4.6 billion light-years away.

[isis]

Cheshire Cat galaxy group: Gravity's Grin

Source: APOD, 2017 August 05

:o

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The Star Streams of NGC 5907



"Explanation: Grand tidal streams of stars seem to surround galaxy NGC 5907. The arcing structures form tenuous loops extending more than 150,000 light-years from the narrow, edge-on spiral, also known as the Splinter or Knife Edge Galaxy. Recorded only in very deep exposures, the streams likely represent the ghostly trail of a dwarf galaxy - debris left along the orbit of a smaller satellite galaxy that was gradually torn apart and merged with NGC 5907 over four billion years ago. Ultimately this remarkable discovery image, from a small robotic observatory in New Mexico, supports the cosmological scenario in which large spiral galaxies, including our own Milky Way, were formed by the accretion of smaller ones. NGC 5907 lies about 40 million light-years distant in the northern constellation Draco."

Source: APOD 2019 November 16

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Andromeda in a Single Shot



"Explanation: How far can you see? The Andromeda Galaxy, 2.5 million light years away, is the most distant object easily seen by the unaided eye. Other denizens of the night sky, like stars, clusters, and nebulae, are typically hundreds to thousands of light-years distant. That's far beyond the Solar System but well within our own Milky Way Galaxy. Also known as M31, the external galaxy poses directly above a chimney in this well-planned deep night skyscape from an old mine in southern Portugal. The image was captured in a single exposure tracking the sky, so the foreground is slightly blurred by the camera's motion while Andromeda itself looms large. The galaxy's brighter central region, normally all that's visible to the naked-eye, can be seen extending to spiral arms with fainter outer reaches spanning over 4 full moons across the sky. Of course in only 5 billion years or so, the stars of Andromeda could span the entire night sky as the Andromeda Galaxy merges with the Milky Way."

Source: APOD 2021 June 25

[Brandon Gwinn]

I love space pictures. They really call you home.

[Ming the Merciful]

http://apod.nasa.gov/apod/archivepix.html

this is a pretty amazing website, with archives going all the way back to 1995!

the wonders of the cosmos truly!

I have always had a theory at the back of my mind, that when we are looking into the depths, (of the deepest space), and at the point where the Universe disappears into the Void. Are we not looking at ourselves? It is a ridicules theory and is not logical, (yet), it is logical, (in an illogical sense). Do you see where I am going? At the point where the Galaxies are created from the "Nothingness", that is where we reside also. Perhaps it is also where the Universal Consciousness begins.

[flofrog]

Lol, Ming, I shall post this, sorry as I posted before but it rejoins your thought above,

https://micro.magnet.fsu.edu/primer/java...index.html

[Ming the Merciful]

Lol,  Ming, I shall post this, sorry as I posted before but it rejoins your thought above,

https://micro.magnet.fsu.edu/primer/java...index.html

Thank you flofrog. Does everything return to the "Fractal Theory". Or, "As Above, So Below". Then the ultimate answer always remains, what lies beyond the edge of the Universe, in the "Void". The Universe is slowly, (relatively), expanding into the Void, (but) is the Void an entity, (unto itself)? Beyond the Beyond. Multidimensional and non-dimensional simultaneously. Before there can be dimensions, there must be something creating them. As for my theory of looking at our past, the deeper we look in space. Could we also be watching the Milky Way going through its evolution, as we observe Galaxy by, (infinite), Galaxies? They are our reflection. Meanwhile, depending on your location within the Universe, it is the same scenario from another perspective. For somebody living in a Galaxy a million Light Years away, is also seeing the same evolution of their Galaxy, (only from their perspective). Both perspectives are different, (yet), the reflection is the same.

We are talking "Hardcore Astrophysics" here, possibly "Hardcore Metaphysics".

Anyone want to add to this discourse?

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M82: Starburst Galaxy with a Superwind



"Explanation: M82 is a starburst galaxy with a superwind. In fact, through ensuing supernova explosions and powerful winds from massive stars, the burst of star formation in M82 is driving a prodigious outflow. Evidence for the superwind from the galaxy's central regions is clear in sharp telescopic snapshot. The composite image highlights emission from long outflow filaments of atomic hydrogen gas in reddish hues. Some of the gas in the superwind, enriched in heavy elements forged in the massive stars, will eventually escape into intergalactic space. Triggered by a close encounter with nearby large galaxy M81, the furious burst of star formation in M82 should last about 100 million years or so. Also known as the Cigar Galaxy for its elongated visual appearance, M82 is about 30,000 light-years across. It lies 12 million light-years away near the northern boundary of Ursa Major."

Source: APOD 2021 July 9

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The Tulip and Cygnus X-1



"Explanation: This tall telescopic field of view looks out along the plane of our Milky Way Galaxy toward the nebula rich constellation Cygnus the Swan. Popularly called the Tulip Nebula, the brightest glowing cloud of interstellar gas and dust above center is also found in the 1959 catalog by astronomer Stewart Sharpless as Sh2-101. Nearly 70 light-years across the complex and beautiful Tulip Nebula blossoms about 8,000 light-years away, shown in a Hubble palette image that maps the glow of the nebula's sulfur, hydrogen, and oxygen ions into red, green, and blue colors. Ultraviolet radiation from young energetic stars at the edge of the Cygnus OB3 association, including O star HDE 227018, ionizes the atoms and powers the emission from the Tulip Nebula. Also in the field of view is microquasar Cygnus X-1, one of the strongest X-ray sources in planet Earth's sky. Driven by powerful jets from a black hole accretion disk, its fainter bluish curved shock front is only just visible though, directly above the cosmic Tulip's petals near the top of the frame."

Source: APOD 2021 July 29

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The Hubble Ultra Deep Field in Light and Sound

"Explanation: Have you heard about the Hubble Ultra-Deep Field? Either way, you've likely not heard about it like this -- please run your cursor over the featured image and listen! The Hubble Ultra-Deep Field (HUDF) was created in 2003-2004 with the Hubble Space Telescope staring for a long time toward near-empty space so that distant, faint galaxies would become visible. One of the most famous images in astronomy, the HUDF is featured here in a vibrant way -- with sonified distances. Pointing to a galaxy will play a note that indicates its approximate redshift. Because redshifts shift light toward the red end of the spectrum of light, they are depicted here by a shift of tone toward the low end of the spectrum of sound. The further the galaxy, the greater its cosmological redshift (even if it appears blue), and the lower the tone that will be played. The average galaxy in the HUDF is about 10.6 billion light years away and sounds like an F#. What's the most distant galaxy you can find?"

Source: APOD 2021 August 2

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For this one you will need to go to the website link, really cool!

[Quincunx]

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