Tag: astronomy

A pair of spiral galaxies

2:02 pm

IC 4271, or AP 40, a pair of active galaxies
Click for full image.

Another cool image to herald in the weekend! The photo to the right, cropped and reduced to post here, was taken by the Hubble Space Telescope and shows a pair of spiral galaxies about 800 million light years away.

The smaller galaxy is superimposed on the larger one, which is a type of active galaxy called a Seyfert galaxy.

Seyfert galaxies are named for astronomer Carl K. Seyfert who, in 1943, published a paper about spiral galaxies with very bright emission lines. Today we know that about 10% of all galaxies may be Seyfert galaxies. They belong to the class of “active galaxies” – galaxies that have supermassive black holes at their centers accreting material, which releases vast amounts of radiation. The active cores of Seyfert galaxies are at their brightest when observed in light outside the visible spectrum. The larger galaxy in this pair is a Type II Seyfert galaxy, which means it is a very bright source of infrared and visible light.

In other words, both of these galaxies emit a lot of radiation in the infrared, radio, and X-rays due to activity taking place at the supermassive black holes believed to be at their cores.

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A giant elliptical galaxy

3:14 pm

A giant elliptical galaxy
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Cool image time! The image to the right, reduced to post here, was taken by the Hubble Space Telescope of the giant elliptical galaxy NGC 474.

Located some 100 million light-years from Earth, NGC 474 spans about 250,000 light-years across – that’s 2.5 times larger than our own Milky Way galaxy! Along with its enormous size, NGC 474 has a series of complex layered shells that surround its spherical-shaped core. The cause of these shells is unknown, but astronomers theorize that they may be the aftereffects of the giant galaxy absorbing one or more smaller galaxies. In the same way a pebble creates ripples on a pond when dropped into the water, the absorbed galaxy creates waves that form the shells.

About 10% of elliptical galaxies have shell structures, but unlike the majority of elliptical galaxies, which are associated with galaxy clusters, shelled ellipticals usually lie in relatively empty space. It may be that they’ve cannibalized their neighbors.

NGC 474 is no exception, also located in a relatively empty region of space.

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First radio image of event horizon of Milky Way’s central black hole

9:31 am

Sagittarius A*
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Using an array of eight radio telescopes worldwide, dubbed the Event Horizon Telescope because its purpose is to study black holes, scientists have obtained the first radio image of the event horizon of Sagittarius A* (pronounced “A-star”), the supermassive black hole at the center of the Milky Way.

The image to the right, reduced to post here, is that photo.

The image is a long-anticipated look at the massive object that sits at the very centre of our galaxy. Scientists had previously seen stars orbiting around something invisible, compact, and very massive at the centre of the Milky Way. This strongly suggested that this object — known as Sagittarius A* (Sgr A*, pronounced “sadge-ay-star”) — is a black hole, and today’s image provides the first direct visual evidence of it.

Although we cannot see the black hole itself, because it is completely dark, glowing gas around it reveals a telltale signature: a dark central region (called a “shadow”) surrounded by a bright ring-like structure. The new view captures light bent by the powerful gravity of the black hole, which is four million times more massive than our Sun.

This is the second supermassive black hole that the Event Horizon array has imaged. In 2019 it captured the central black hole of the galaxy M87, 55 million light years away. Like that first image, much of what we see here is created by computer, since the data from the eight radio telescopes needs to be massaged to create something as smooth and as complete as this.

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NASA decides to end airborne SOFIA telescope operations

10:03 am

According to a joint announcement yesterday from NASA and the German space agency DLR, all operations of the airborne astronomy telescope SOFIA will end as of September ’22.

NASA has been trying to cancel this project for several years, because its capabilities have not justified its expense, about $85 million per year. Congress has repeatedly refused to go along, reinserting funding after NASA tried to delete it. That the astronomy community itself suggested in November that the project be canceled, however, probably means this Congress will likely go along with this most recent announcement.

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Colliding galaxies

1:11 pm

Merging galaxies

The string of amazing galaxy images coming from the Hubble Space Telescope continues. The photo to the right, cropped and reduced to post here, was released today and shows an object dubbed VV-689 that is believed to be two galaxies in the process of colliding and merging.

The angelic image comes from a set of Hubble observations that took a closer look at “Zoo Gems,” interesting galaxies from the Galaxy Zoo citizen science project. This crowdsourced program relies on hundreds of thousands of volunteers to classify galaxies and help astronomers wade through a deluge of data from robotic telescopes. In the process, volunteers discovered a gallery of weird and wonderful galaxy types, some not previously studied.

This image will lay the groundwork for more detailed research. Right now it appears no one has even estimated its distance.

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Astronomers discover new type of stellar explosion

11:31 am

Using data from the orbiting TESS observatory and the ground-based Very Large Telescope (VLT) in Chile, astronomers have detected evidence of a new type of stellar explosion they have dubbed a “micronova.”

The micronova appears to be a smaller version of a nova, which brightens the entire star for a month or so.

A white dwarf in a two-star system can steal material, mostly hydrogen, from its companion star if they are close enough together. As this gas falls onto the very hot surface of the white dwarf star, it triggers the hydrogen atoms to fuse into helium explosively. In novae, these thermonuclear explosions occur over the entire stellar surface. “Such detonations make the entire surface of the white dwarf burn and shine brightly for several weeks,” explains co-author Nathalie Degenaar, an astronomer at the University of Amsterdam, the Netherlands.

Micronovae are similar explosions that are smaller in scale and faster, lasting just several hours. They occur on some white dwarfs with strong magnetic fields, which funnel material towards the star’s magnetic poles. “For the first time, we have now seen that hydrogen fusion can also happen in a localised way. The hydrogen fuel can be contained at the base of the magnetic poles of some white dwarfs, so that fusion only happens at these magnetic poles,” says Paul Groot, an astronomer at Radboud University in the Netherlands and co-author of the study.

What this discover really reveals is that as our astronomical observing technology improves, we can observe a greater variety of stellar phenomenon. Expect astronomers in future years to detect an even wider variety of stellar explosions, most of which have not be detectable up until now because we simply couldn’t see them.

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Hubble looks at a tight cluster of five galaxies

1:33 pm

Hickson Compact Group 40
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Cool image time! The photo to the right, cropped and reduced to post here, was taken by the Hubble Space Telescope to celebrate the telescope’s 32nd year in orbit. This cluster of five galaxies is dubbed Hickson Compact Group 40.

This menagerie includes three spiral-shaped galaxies, an elliptical galaxy, and a lenticular (lens-like) galaxy. Somehow, these different galaxies crossed paths in their evolution to create an exceptionally crowded and eclectic galaxy sampler.

Caught in a leisurely gravitational dance, the whole group is so crowded that it could fit within a region of space that is less than twice the diameter of our Milky Way’s stellar disk.

Though such cozy galaxy groupings can be found in the heart of huge galaxy clusters, these galaxies are notably isolated in their own small patch of the universe, in the direction of the constellation Hydra.

The red streaks in three galaxies is thought to be dust, suggesting that stars are still forming in these galaxies. The vertical galaxy on the right is seen edge on. Note too the tilted ring that appears to surround the galaxy on the left.

As for Hubble’s anniversary, the press release notes that since launch in 1990 the space telescope has made 1.5 million observations covering 50,000 heavenly objects, an archive of data available to anyone to access.

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The spiral galaxy M91

3:38 pm

spiral galaxy M91
Click for full release image.

Cool image time! The image to the right, reduced to post here, was released today by the Space Telescope Science Institute as part of a regular program using the Hubble Space Telescope to photograph galaxies.

This observation is part of an effort to build a treasure trove of astronomical data exploring the connections between young stars and the clouds of cold gas in which they form. To do this, astronomers used Hubble to obtain ultraviolet and visible observations of galaxies already seen at radio wavelengths by the ground-based Atacama Large Millimeter/submillimeter Array.

The galaxy is estimated to be about 55 million light years away, and is thought to have a supermassive black hole at its center with a mass somewhere between 9 and 38 million times the mass of the Sun.

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Webb’s coldest instrument reaches operating temperature

1:32 pm

The engineering team announced today that the mid-infrared instrument on the James Webb Space Telescope has now cooled to its operating temperature of -447 degrees Fahrenheit, less than 7 kelvin degrees above absolute zero.

On April 7, Webb’s Mid-Infrared Instrument (MIRI) – a joint development by NASA and ESA (European Space Agency) – reached its final operating temperature below 7 kelvins (minus 447 degrees Fahrenheit, or minus 266 degrees Celsius).

Along with Webb’s three other instruments, MIRI initially cooled off in the shade of Webb’s tennis-court-size sunshield, dropping to about 90 kelvins (minus 298 F, or minus 183 C). But dropping to less than 7 kelvins required an electrically powered cryocooler. Last week, the team passed a particularly challenging milestone called the “pinch point,” when the instrument goes from 15 kelvins (minus 433 F, or minus 258 C) to 6.4 kelvins (minus 448 F, or minus 267 C).

Before science operations can begin the instruments still need further calibration and testing. Expect the first infrared images sometime in the next month or so.

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Astronomers confirm comet with largest nucleus ever found

9:29 am

Using the Hubble Space Telescope astronomers determined that the nucleus of Comet Bernardinelli-Bernstein (C/2014 UN271) is about 80 miles wide, making it the largest comet on record.

The estimated diameter is approximately 80 miles across, making it larger than the state of Rhode Island. The nucleus is about 50 times larger than found at the heart of most known comets. Its mass is estimated to be a staggering 500 trillion tons, a hundred thousand times greater than the mass of a typical comet found much closer to the Sun.

The behemoth comet, C/2014 UN271 (Bernardinelli-Bernstein) is barreling this way at 22,000 miles per hour from the edge of the solar system. But not to worry. It will never get closer than 1 billion miles away from the Sun, which is slightly farther than the distance of the planet Saturn. And that won’t be until the year 2031.

The previous record holder is comet C/2002 VQ94, with a nucleus estimated to be 60 miles across. It was discovered in 2002 by the Lincoln Near-Earth Asteroid Research (LINEAR) project.

This measurement does have a great deal of uncertainty, as Hubble cannot yet resolve the nucleus, and thus its diameter was determined by computer models based on the size of the comet’s coma, or surrounding atmosphere.

The comet itself has an orbit 3 million years long, which means it has zipped into the inner solar system many many times. The reason its nucleus remains so large is because its orbit never gets that close to the Sun, so its material does not get burned off so much with each perihelion. That it exists suggests there could be many such large comets which never dip close to the Sun.

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Interstellar meteor impacted Earth in 2014

10:28 am

According to classified military data just released, it appears that an asteroid from interstellar space impacted the Earth in 2014, with some of its pieces possibly hitting the ocean in the south Pacific.

The meteor ignited in a fireball in the skies near Papua New Guinea, the memo states, and scientists believe it possibly sprinkled interstellar debris into the South Pacific Ocean. The confirmation backs up the breakthrough discovery of the first interstellar meteor—and, retroactively, the first known interstellar object of any kind to reach our solar system—which was initially flagged by a pair of Harvard University researchers in a study posted on the preprint server arXiv in 2019.

Amir Siraj, a student pursuing astrophysics at Harvard who led the research, said the study has been awaiting peer review and publication for years, but has been hamstrung by the odd circumstances that arose from the sheer novelty of the find and roadblocks put up by the involvement of information classified by the U.S. government.

The speed and angle in which the object hit the atmosphere are why the scientists believe it comes from outside the solar system.

Siraj is actually hoping to mount a mission to recover parts of this asteroid, something that is extremely unlikely. First, the meteor itself was small, so it likely all burned up in re-entry. Second, even if pieces survived, finding them on the bottom of the Pacific is likely impossible.

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Neptune’s cooling when it should be warming

9:45 am

Neptune since 2006

The uncertainty of science: Observations of Neptune during the past seventeen years using the Very Large Telescope have shown the planet mostly cooling during this time period, even though Neptune was moving into its summer season.

Astronomers looked at nearly 100 thermal-infrared images of Neptune, captured over a 17-year period, to piece together overall trends in the planet’s temperature in greater detail than ever before. These data showed that, despite the onset of southern summer, most of the planet had gradually cooled over the last two decades. The globally averaged temperature of Neptune dropped by 8 °C between 2003 and 2018.

The astronomers were then surprised to discover a dramatic warming of Neptune’s south pole during the last two years of their observations, when temperatures rapidly rose 11 °C between 2018 and 2020. Although Neptune’s warm polar vortex has been known for many years, such rapid polar warming has never been previously observed on the planet. “Our data cover less than half of a Neptune season, so no one was expecting to see large and rapid changes,” says co-author Glenn Orton, senior research scientist at Caltech’s Jet Propulsion Laboratory (JPL) in the US.

The sequence of photos above show that change over time. Lower latitudes generally get darker, or cooler, while the south pole suddenly brightens, getting hotter, in 2020.

The scientists have no idea why this has happened, though they have theories, ranging from simple random weather patterns to the influence of the Sun’s sunspot cycle.

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Astronomers discover a solar twin whose sunspot cycle changed into a grand minimum

9:19 am

Astronomers studying the sunspot cycle of several dozen stars that are twins of our Sun have identified for the first time a star whose 17-year cycle suddenly ceased, going into an extended grand minimum.

Comparing these stars to the Sun enables astronomers to better determine how typical – or not – the Sun is as a star. The Sun’s magnetic activity is defined by its 11-year sunspot cycle. Of the 59 stars that Baum’s team surveyed, 29 appeared to also have starspot cycles, and the period of those cycles could be measured for 14 of them.

“Of these 14 stars, the average length of their cycle is just under 10 years, which is similar to the Sun’s 11-year cycle,” Baum tells Physics World. However, not all the stars adhered to this time frame. One star that was surveyed has a cycle lasting less than four years, while another star, HD 166620, had a cycle 17 years long.

Note the past tense. Sometime between 1995 and 2004, HD 166620’s starspot cycle simply stopped.

When or if the star’s sunspot activity resume is unknown. The Sun’s last grand minimum, dubbed the Maunder Minimum, lasted 70 years during the 1600s.

No one yet understands why stars do this. This discovery however now shows that the Sun is not unique in this behavior.

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Astronomers directly image the orbital motion of Jupiter protoplanet 531 light years away

1:41 pm

AB Aurigae B's motion over thirteen years
Click for original image.

Astronomers, using a number of ground- and space-based telescopes, have now directly photographed the orbital motion of a Jupiter protoplanet orbiting a star 531 light years away over a thirteen year time span.

The image to the right, cropped to post here, shows images produced by two Hubble instruments. The caption:

Researchers were able to directly image newly forming exoplanet AB Aurigae b over a 13-year span using Hubble’s Space Telescope Imaging Spectrograph (STIS) and its Near Infrared Camera and Multi-Object Spectrograph (NICMOS). In the top right, Hubble’s NICMOS image captured in 2007 shows AB Aurigae b in a due south position compared to its host star, which is covered by the instrument’s coronagraph. The image captured in 2021 by STIS shows the protoplanet has moved in a counterclockwise motion over time.

From the paper’s abstract:

Using the Subaru Telescope and the Hubble Space Telescope, we find evidence for a Jovian protoplanet around AB Aurigae orbiting at a wide projected separation (~93 au), probably responsible for multiple planet-induced features in the disk. Its emission is reproducible as reprocessed radiation from an embedded protoplanet.

The accretion disk around AB Aurigae happens to lie face on to our line of sight, which facilitates these observations. The data also shows two additional potential proto-planets farther from the star.

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Astronomers think they have detected the most distant star ever

9:24 am

The most distant star ever detected?
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The uncertainty of science: Using the Hubble Space Telescope astronomers now think they have detected the most distant single star ever located, the light of which is estimated to have come from a time only less than a billion years after the Big Bang itself.

The star, nicknamed Earendel by astronomers, emitted its light within the universe’s first billion years. It’s a significant leap beyond Hubble’s previous distance record, in 2018, when it detected a star at around 4 billion years after the big bang. Hubble got a boost by looking through space warped by the mass of the huge galaxy cluster WHL0137-08, an effect called gravitational lensing. Earendel was aligned on or very near a ripple in the fabric of space created by the cluster’s mass, which magnified its light enough to be detected by Hubble.

The arrow in the image, cropped and reduced to post here, points to the theorized star. Note the arc that tiny dot lies along. This arc is the result of the gravitational lensing, and illustrates quite bluntly the large uncertainties of this discovery. We are not seeing the star itself, but the distorted light after it passed through the strong gravitational field of the cluster of galaxies. The scientists conclusion that this dot is thus a single star, must be view with great skepticism.

Nonetheless, the data is intriguing, and will certainly be one of the early targets of the James Webb Space Telescope, which could confirm or disprove this hypothesis.

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Sharpest radio image ever taken of newly discovered space object

9:11 am

The first known Odd Radio Circle (ORC)
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The uncertainty of science: Astronomers, using the MeerKat radio telescope in South Africa, have taken the best radio image yet of a newly discovered type of astronomical object, dubbed whimsically as an odd radio circle (ORC).

The photo to the right is that image. While it is reminiscent of the many planetary nebulae seen in visible light that astronomers have been studying since the 1800s, this weird shape is only seen in radio frequencies, and it is much much larger.

Odd radio circles are so named because they’re large, circular objects which are bright around the edges at radio wavelengths, but which can’t be seen with optical, infrared or X-ray telescopes – and at this stage, astronomers don’t really know what they are.

And they’re massive – about a million light years across, making them sixteen times larger than our own galaxy. But despite their gargantuan size, the objects are difficult to spot, hiding in plain sight.

Planetary nebulae are generally the size of solar systems.

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Alignment of segments in Webb’s primary mirror completed

3:06 pm

Alignment image
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Astronomers and engineers have now successfully completed the alignment of the eighteen segments in the primary mirror of the James Webb Space Telescope.

On March 11, the Webb team completed the stage of alignment known as “fine phasing.” At this key stage in the commissioning of Webb’s Optical Telescope Element, every optical parameter that has been checked and tested is performing at, or above, expectations. The team also found no critical issues and no measurable contamination or blockages to Webb’s optical path. The observatory is able to successfully gather light from distant objects and deliver it to its instruments without issue.

The picture to the right shows that alignment, focused on a single star. As noted in the caption:

While the purpose of this image was to focus on the bright star at the center for alignment evaluation, Webb’s optics and NIRCam are so sensitive that the galaxies and stars seen in the background show up.

After many years delay and an ungodly budget overrun, thank goodness Webb appears to be working better than expected.

It will still be several months before actual science observations begin. Further more precise alignment adjustments need to be done for all its instruments and mirrors.

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Supernova discovered in Cartwheel galaxy

8:54 am

Cartwheel Galaxy, before and after supernova
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Cool image time! In reviewing a December 2021 image of the Cartwheel Galaxy taken by the New Technology Telescope in Chile, astronomers noticed something that was not there in earlier images, a new supernovae.

The photo above, reduced to post here, compares a 2014 image, taken by the Very Large Telescope, with the 2021 photo. In the lower left of the new image is a bright object not in the previous photo.

This event, called SN2021afdx, is a type II supernova, which occurs when a massive star reaches the end of its evolution. Supernovae can cause a star to shine brighter than its entire host galaxy and can be visible to observers for months, or even years — a blink of an eye on astronomical timescales. Supernovae are one of the reasons astronomers say we are all made of stardust: they sprinkle the surrounding space with heavy elements forged by the progenitor star, which may end up being part of later generations of stars, the planets around them and life that may exist in those planets.

Cartwheel is about 500 million light years away, and because of its bright outer ring is one one of the more unusual nearby galaxies.

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Chandra’s camera remains in safe mode

12:12 pm

Though engineers have improvised a work-around that has allowed most of instruments on the Chandra X-Ray observatory to resume science operations, the power supply problem in the telescope’s high resolution camera (HRC) that occurred on February 9th remains unresolved, leaving that camera in safe mode.

The Chandra science instrument and engineering teams continue to analyze the cause of the HRC power supply issue, as well as potential approaches to enable the HRC again. The spacecraft is otherwise healthy and operating normally.

Chandra has been flying now for more than two decades, well past its original mission. For it to begin to have these problems is not surprising, though it will be a great tragedy if it fails just as the James Webb Space Telescope is about to go operational. Ideally astronomers want data from both, as well as Hubble, to cover a wide swath of the electromagnetic spectrum, from the optical to the infrared to X-rays.

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Have astronomers found an exoplanet with raining metal and gems?

9:33 am

The uncertainty of science: Using data from the Hubble Space Telescope, astronomers think they have detected on a hot Jupiter exoplanet 880 light years away the formation of clouds and rain made up metals and gems.

The exoplanet is tidally locked so that one side always faces its star, which also means the temperature difference between the two hemispheres is gigantic, 5,400 degrees Fahrenheit on the dayside and about 2,600 degrees on the nightside.

Previous Hubble data showed signs of metals including iron, magnesium, chromium and vanadium existing as gasses on the planet’s dayside. But in this study, the researchers have found that on the planet’s nightside, it gets cold enough for these metals to condense into clouds.

And, just as the strong winds pull water vapor and atoms around the planet to break apart and recombine, metal clouds will blow to the planet’s dayside and evaporate, condense back on the nightside and so on.

But metal clouds aren’t the only strange phenomenon these researchers spotted on this hot Jupiter. They also found evidence of possible rain in the form of liquid gems.

While tantalizing and alien, these results have many uncertainties. What the data suggests might not be the reality. To find out more, the astronomers hope to use the James Webb Space Telescope to do more infrared observations, once it becomes operational.

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