Category Archives: Galaxies

Spitzer’s Whirlpool Warhol

I like the Warhol reference, don’t be fooled though, the colors are very meaningful.

Spitzer et al.: Unlike Andy Warhol’s famous silkscreen grids of repeating images rendered in different colors, the varying hues of this galaxy represent how its appearance changes in different wavelengths of light — from visible light to the infrared light seen by NASA’s Spitzer Space Telescope.

The Whirlpool galaxy, also known as Messier 51 and NGC 5194/5195, is actually a pair of galaxies that are tugging and distorting each other through their mutual gravitational attraction. Located approximately 23 million light-years away, it resides in the constellation Canes Venatici.

The leftmost panel (a) shows the Whirlpool in visible light, much as our eye might see it through a powerful telescope. In fact, this image comes from the Kitt Peak National Observatory 2.1-meter (6.8-foot) telescope. The spiraling arms are laced with dark threads of dust that radiate little visible light and obscure stars positioned within or behind them.

The second panel from the left (b) includes two visible-light wavelengths (in blue and green) from Kitt Peak but adds Spitzer’s infrared data in red. This emphasizes how the dark dust veins that block our view in visible light begin to light up at these longer, infrared wavelengths.

Spitzer’s full infrared view can be seen in the right two panels, which cover slightly different ranges of infrared light.

In the middle-right panel (c), we see three wavelengths of infrared light: 3.6 microns (shown in blue), 4.5 microns (green) and 8 microns (red). The blended light from the billions of stars in the Whirlpool is brightest at the shorter infrared wavelengths and is seen here as a blue haze. The individual blue dots across the image are mostly nearby stars and a few distant galaxies. Red features show us dust composed mostly of carbon that is lit up by the stars in the galaxy.

This glowing dust helps astronomers see where the densest areas of gas pile up in the spaces between the stars. Dense gas clouds are difficult to see in visible or infrared light, but they will always be present where there is dust.

The far-right panel (d) expands our infrared view to include light at a wavelength of 24 microns (in red), which is particularly good for highlighting areas where the dust is especially hot. The bright reddish-white spots trace regions where new stars are forming and, in the process, heating their surroundings.

The infrared views of the Whirlpool galaxy also show how dramatically different its two component parts are: The smaller companion galaxy at the top of the image has been stripped nearly clean of dust features that stand out so brilliantly in the lower spiral galaxy. The faint bluish haze seen around the upper galaxy is likely the blended light from stars thrown out of the galaxies as these two objects pull at each other during their close approach.

The Kitt Peak visible-light image (a) shows light at 0.4 and 0.7 microns (blue and red). The rightmost two images (c and d) are from Spitzer with red, green and blue corresponding to wavelengths of 3.6, 4.5 and 8.0 microns (middle right) and 3.6, 8.0 and 24 microns (far right). The middle-left (b) image blends visible wavelengths (blue/green) and infrared (yellow/red). All of the data shown here were released as part of the Spitzer Infrared Nearby Galaxies Survey (SINGS) project, captured during Spitzer’s cryogenic and warm missions.

The Jet Propulsion Laboratory in Pasadena, California, manages the Spitzer Space Telescope mission for NASA’s Science Mission Directorate in Washington. Science operations are conducted at the Spitzer Science Center at Caltech in Pasadena. Space operations are based at Lockheed Martin Space Systems in Littleton, Colorado. Data are archived at the Infrared Science Archive housed at IPAC at Caltech. Caltech manages JPL for NASA.

Credits: NASA/JPL-Caltech

Irregular Galaxy IC 10

ESA: This image shows an irregular galaxy named IC 10, a member of the Local Group — a collection/grouping of over 50 galaxies in/within our cosmic neighbourhood that includes the Milky Way.IC 10 is a remarkable object. It is the closest-known starburst galaxy to us, meaning that it is undergoing a furious bout of star formation fueled by ample supplies of cool hydrogen gas. This gas condenses and congeals into vast molecular clouds, which then form and condense into dense knots where pressures and temperatures reach a point sufficient to ignite nuclear fusion, thus giving rise to new generations of stars.  As an irregular galaxy, IC 10 lacks the majestic shape of spiral galaxies such as the Milky Way, or the rounded, ethereal appearance of elliptical galaxies. It is a faint object, despite its relative proximity to us — just 2.2 million light-years. In fact, IC 10 only became known to humankind in 1887, when American astronomer Lewis Swift spotted it during an observing campaign. The small galaxy remains difficult to study even today, because it is located along a line -of -sight which is chock-full of cosmic dust and stars.A version of this image was entered into the Hubble’s Hidden Treasures image processing competition by contestant Nikolaus Sulzenauer, and went on to win tenth prize.

Image and description: NASA, ESA and F. Bauer; CC BY 4.0

Galactic Hit-and-Run


Hubble et al.: The irregular galaxy NGC 4485 shows all the signs of having been involved in a hit-and-run accident with a bypassing galaxy. Rather than destroying the galaxy, the chance encounter is spawning a new generation of stars, and presumably planets.

The right side of the galaxy is ablaze with star formation, shown in the plethora of young blue stars and star-incubating pinkish nebulas. The left side, however, looks intact. It contains hints of the galaxy’s previous spiral structure, which, at one time, was undergoing normal galactic evolution.

The larger culprit galaxy, NGC 4490, is off the bottom of the frame. The two galaxies sideswiped each other millions of years ago and are now 24,000 light-years apart. The gravitational tug-of-war between them created rippling patches of higher-density gas and dust within both galaxies. This activity triggered a flurry of star formation.

This galaxy is a nearby example of the kind of cosmic bumper-car activity that was more common billions of years ago when the universe was smaller and galaxies were closer together.

NGC 4485 lies 25 million light-years away in the northern constellation Canes Venatici (the Hunting Dogs).

This new image, captured by Hubble’s Wide Field Camera 3 (WFC3), provides further insight into the complexities of galaxy evolution.

The Hubble Space Telescope is a project of international cooperation between NASA and ESA (European Space Agency). NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy in Washington, D.C.

Text credit: Space Telescope Science Institute
Image credit: NASA, ESA; acknowledgment: T. Roberts (Durham University, UK), D. Calzetti (University of Massachusetts) and the LEGUS Team, R. Tully (University of Hawaii) and R. Chandar (University of Toledo)

Hubble Looks at NGC 2903

NGC 2903 was discovered by William Hershel in 1784. Although this spiral galaxy was certainly bright enough to be seen by Charles Messier he never added it to his famous catalog. There is an entry for it in the SEDS site.

As for this lovely image from Hubble ESA writes:

Few of the Universe’s residents are as iconic as the spiral galaxy. These limelight-hogging celestial objects combine whirling, pinwheeling arms with scatterings of sparkling stars, glowing bursts of gas, and dark, weaving lanes of cosmic dust, creating truly awesome scenes — especially when viewed through a telescope such as the NASA/ESA Hubble Space Telescope. In fact, this image from Hubble frames a perfect spiral specimen: the stunning NGC 2903.

NGC 2903 is located about 30 million light-years away in the constellation of Leo (The Lion), and was studied as part of a Hubble survey of the central regions of roughly 145 nearby disc galaxies. This study aimed to help astronomers better understand the relationship between the black holes that lurk at the cores of galaxies like these, and the rugby-ball-shaped bulge of stars, gas, and dust at the galaxy’s centre — such as that seen in this image.

Image: ESA/Hubble & NASA, L. Ho et al.; CC BY 4.0

Merging Galaxies

Can you image being on a planet in either one of these colliding galaxies? One day in the very far future this might be a good analogy of our merging with the Andromeda galaxy. What would the sky look like, even in the daytime?

ESA: Located in the constellation of Hercules, about 230 million light-years away, NGC 6052 is a pair of colliding galaxies. They were first discovered in 1784 by William Herschel and were originally classified as a single irregular galaxy because of their odd shape. However, we now know that NGC 6052 actually consists of two galaxies that are in the process of colliding. This particular image of NGC 6052 was taken using the Wide Field Camera 3 on the NASA/ESA Hubble Space Telescope.

A long time ago gravity drew the two galaxies together into the chaotic state we now observe. Stars from within both of the original galaxies now follow new trajectories caused by the new gravitational effects. However, actual collisions between stars themselves are very rare as stars are very small relative to the distances between them (most of a galaxy is empty space). Eventually things will settle down and one day the two galaxies will have fully merged to form a single, stable galaxy.

Our own galaxy, the Milky Way, will undergo a similar collision in the future with our nearest galactic neighbour, the Andromeda Galaxy. Although this is not expected to happen for around 4 billion years so there is nothing to worry about just yet.

This object was previously observed by Hubble with its old WFPC2 camera. That image was released in 2015.

Image: ESA/Hubble & NASA, A. Adamo et al.; CC BY 4.0

Our (distant) Future

NASA: An image of the galaxy Arp299B, which is undergoing a merging process with Arp299A (the galaxy to the left), captured by NASA’s Hubble space telescope. The inset features an artist’s illustration of a tidal disruption event (TDE), which occurs when a star passes fatally close to a supermassive black hole. A TDE was recently observed near the center of Arp299B.

Is this our future? Yes it or something approximating this will, it seems, will happen. The Milky Way and the Andromeda Galaxy will one day merge. Not to worry, it will be many millions of years in the future. Most galaxies are red-shifted, moving away from us; most but not all. Andromeda is blue-shifted meaning it is moving towards us.

Red-shifted? Blue-shifted? Ahh, the Doppler Effect.


Lop-sided Galaxy NGC 4625

This galaxy is called NGC 4625 and it is a dwarf galaxy located 30-million light-years away in the constellation Canes Venatici.

It is indeed quite lop-sided. I would imagine the rotation of the galaxy would reflect the absence of mass by the center of gravity being just a little off and producing a distinct wobble.

From ESA/NASA/Hubble: This new picture of the week, taken by the NASA/ESA Hubble Space Telescope, shows the dwarf galaxy NGC 4625, located about 30 million light-years away in the constellation of Canes Venatici (The Hunting Dogs). The image, acquired with the Advanced Camera for Surveys (ACS), reveals the single major spiral arm of the galaxy, which gives it an asymmetric appearance. But why is there only one such spiral arm, when spiral galaxies normally have at least two?

Astronomers looked at NGC 4625 in different wavelengths in the hope of solving this cosmic mystery. Observations in the ultraviolet provided the first hint: in ultraviolet light the disk of the galaxy appears four times larger than on the image depicted here. An indication that there are a large number of very young and hot — hence mainly visible in the ultraviolet — stars forming in the outer regions of the galaxy. These young stars are only around one billion years old, about 10 times younger than the stars seen in the optical center. At first astronomers assumed that this high star formation rate was being triggered by the interaction with another, nearby dwarf galaxy called NGC 4618.

They speculated that NGC 4618 may be the culprit “harassing” NGC 4625, causing it to lose all but one spiral arm. In 2004 astronomers found proof for this claim. The gas in the outermost regions of the dwarf galaxy NGC 4618 has been strongly affected by NGC 4625.

Credit: ESA/Hubble & NASA
Text credit: European Space Agency

Hubble Parallel Field

HUBBLE: While one instrument of the NASA/ESA Hubble Space Telescope observed a pair of spiral galaxies for its 27th anniversary last month, another simultaneously observed a nearby patch of the sky to obtain this wide-field view.

These ‘parallel field’ observations increase the telescope’s productivity.

This parallel field shows an area of the sky awash largely with spiral galaxies like our Milky Way. Most of the prominent galaxies look different only because they are tilted at various orientations to our viewpoint – from edge-on to face-on. A few others are interacting or merging.

The image also shows a number of foreground stars in our own galaxy.

Credit: NASA, ESA & M. Mutchler (STScI)

Expelling A Black Hole

Think gravity waves are weak? Think again, wow almost hard to believe.

Credit: Hubblesite

from STSci:

Astronomers have uncovered a supermassive black hole that has been propelled out of the center of a distant galaxy by what could be the awesome power of gravitational waves.

Though there have been several other suspected, similarly booted black holes elsewhere, none has been confirmed so far. Astronomers think this object, detected by NASA’s Hubble Space Telescope, is a very strong case. Weighing more than 1 billion suns, the rogue black hole is the most massive black hole ever detected to have been kicked out of its central home.

Researchers estimate that it took the equivalent energy of 100 million supernovas exploding simultaneously to jettison the black hole. The most plausible explanation for this propulsive energy is that the monster object was given a kick by gravitational waves unleashed by the merger of two hefty black holes at the center of the host galaxy.
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NuStar Looks at Was 49

This is pretty amazing.  For scale the distance mentioned in the press release below of 26,000 light years  approximates the distance from out solar system to the center of our Milky Way.  See here.

A long way for solar system sure, but a galaxy?  Even a small one?  Amazing.

The press release:

A supermassive black hole inside a tiny galaxy is challenging scientists’ ideas about what happens when two galaxies become one.

Was 49 is the name of a system consisting of a large disk galaxy, referred to as Was 49a, merging with a much smaller “dwarf” galaxy called Was 49b. The dwarf galaxy rotates within the larger galaxy’s disk, about 26,000 light-years from its center. Thanks to NASA’s Nuclear Spectroscopic Telescope Array (NuSTAR) mission, scientists have discovered that the dwarf galaxy is so luminous in high-energy X-rays, it must host a supermassive black hole much larger and more powerful than expected.

“This is a completely unique system and runs contrary to what we understand of galaxy mergers,” said Nathan Secrest, lead author of the study and postdoctoral fellow at the U.S. Naval Research Laboratory in Washington.

Data from NuSTAR and the Sloan Digital Sky Survey suggest that the mass of the dwarf galaxy’s black hole is huge, compared to similarly sized galaxies, at more than 2 percent of the galaxy’s own mass.

“We didn’t think that dwarf galaxies hosted supermassive black holes this big,” Secrest said. “This black hole could be hundreds of times more massive than what we would expect for a galaxy of this size, depending on how the galaxy evolved in relation to other galaxies.”

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