Tag: astronomy

Viewing Comet Tsuchinshan-ATLAS

9:02 am

While the newly discovered Comet Tsuchinshan-ATLAS in the past week reached naked eye visibility in the dawn sky, in the next few weeks it will shift into the evening sky on October 11, 2024 while brightening to peak levels.

Although Comet Tsuchinshan-ATLAS will be visible in both hemispheres, the northern one is favored because the comet tracks north. Also, sunsets are getting earlier and twilights shorter, while the opposite is happening in southern latitudes.

Observers should be aware that the Moon will interfere for several nights, from about Oct. 15-20 (full Moon is on Oct. 17th), around the same time the comet climbs out of twilight.

As it begins to fade, the comet will be visible at an increasing height above the horizon each night through the end of October. At its brightest it is expected to be one of the brightest objects in the sky.

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Astronomers detect exoplanet half as massive as the Earth around second closest star system

11:28 am

Using the Very Large Telescope (VLT) in Chile, astronomers have detected evidence of an exoplanet about half as massive as the Earth orbiting Barnard’s Star, only six light years away and the second closest star system.

Barnard’s Star is a prime target in the search for exoplanets due to its proximity and its status as a red dwarf, a common type of star where low-mass planets are often found. Despite a promising signal detected in 2018, no planet had been definitively confirmed around it until now. The ESPRESSO spectrograph [on VLT] … enabled the astronomers to detect Barnard b, a subterrestrial planet that orbits the star in 3.15 days. The team also identified signals indicating the possible presence of three other candidate exoplanets, which have yet to be confirmed.

Back in the 1960s using the less precise instruments of the time, astronomers thought they had detected an exoplanet orbiting Barnard’s Star. That detection however proved false. The detection is real, however, and adds weight to the growing evidence that planets can form around red dwarf stars, the most common stars in the universe with the longest lifespan, predicted to be many tens of billions of years. Having planets around such stars significantly increases the chances of habitable planets, even if those planets do not harbor life of its own.

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Data from two different studies suggest Betelgeuse has a Sun-sized companion star

9:46 am

Betelqeuse
An optical image of Betelgeuse taken in 2017 by a ground-based
telescope, showing its not unusual aspherical shape.
Click for original image.

Two different independent studies have uncovered evidence that the red giant star Betalgeuse likely has an unseen companion star about the mass of the Sun and orbiting it every six years.

MacLeod and colleagues linked a six-year cycle of Betelgeuse brightening and dimming to a companion star tweaking its orbit, in a paper submitted to arXiv.org September 17. MacLeod examined global, historical measurements dating back to 1896.

Separately, Jared Goldberg of the Flatiron Institute in New York and colleagues used the last 20-odd years of measurements of Betelgeuse’s motion on the sky, which have the highest precision. That team also found evidence of a companion nudging the bigger star, submitted to arXiv.org August 17.

Previous observers noticed Betelgeuse’s light varying on a roughly six-year cycle. In 1908, English astronomer Henry Cozier Plummer suggested the cycle could be from the gravity of a companion star tugging Betelgeuse back and forth.

You can download the two papers here and here. This quote from the first paper’s abstract not only explains why the star has not been detected previously, but suggests its doomed future:

The companion star would be nearly twenty times less massive and a million times fainter than Betelgeuse, with similar effective temperature, effectively hiding it in plain sight near one of the best-studied stars in the night sky. The astrometric data favor an edge-on binary with orbital plane aligned with Betelgeuse’s measured spin axis. Tidal spin-orbit interaction drains angular momentum from the orbit and spins up Betelgeuse, explaining the spin–orbit alignment and Betelgeuse’s anomalously rapid spin. In the future, the orbit will decay until the companion is swallowed by Betelgeuse in the next 10,000 years. [emphasis mine]

The presence and future capture of this small companion star will help astronomers better calculate future fluctuations of Betelgesue itself. That capture is also going to occur relatively soon, on astronomical time scales.

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The jet 3,000 light years long that causes nearby stars to explode

10:48 am

The jet from M87
Click for original image.

Cool image time! The picture to the left, cropped, reduced, and sharpened to post here, was taken by the Hubble Space Telescope of the giant eliptical galaxy M87, known for more than a century by astronomers for the jet of gas that points outward from its center. Astronomers now know that this jet is produced by a supermassive black hole in the center of M87, weighing 6.5 billion times the mass of our Sun.

The blowtorch-like jet seems to cause stars to erupt along its trajectory. These novae are not caught inside the jet, but are apparently in a dangerous neighbourhood nearby. During a recent 9-month survey, astronomers using Hubble found twice as many of these novae going off near the jet as elsewhere in the galaxy. The galaxy is the home of several trillion stars and thousands of star-like globular star clusters.

M87 is considered an old galaxy, but its entire formation process remains uncertain.

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Webb takes an infrared look at a galaxy looked at by Hubble

12:21 pm

Comparing Hubble with Webb
For original images go here and here.

Cool image time! The bottom picture on the right, cropped to post here, is a just released false color infrared image of the galaxy Arp 107, taken by the Webb Space Telescope. The picture at the top is a previously released optical image taken by the Hubble Space Telescope and featured as a cool image back in September 2023. The Hubble image was taken as part of a survey project to photograph the entire Arp catalog of 338 “peculiar galaxies,” put together by astronomer Halton Arp in 1966. In this case Arp 107 is peculiar because it is actually two galaxies in the process of merging. It is also peculiar because the galaxy on the left has an active galactic nuclei (AGN), where a supermassive black hole is sucking up material and thus emitting a lot of energy.

The Webb infrared image was taken to supplement that optical image. The blue spiral arms indicate dust and star-forming regions. The bright orange object in the center of the galaxy is that AGN, clearly defined by Webb’s infrared camera.

When I posted the Hubble image in 2023, I noted that “if you ignore the blue whorls of the left galaxy, the two bright cores of these merging galaxies are about the same size.” In the Webb image the two cores still appear about the same size, but in the infrared they produce emissions in decidedly different wavelengths, as shown by the different false colors of orange and blue. The core of the galaxy on the right is dust filled and forming stars, while the core of the left galaxy appears to have less dust with all of its emissions resulting from the energy produced by the material being pulled into the supermassive black hole.

The universe is very active and changing, but to understand that process we humans have to look at everything across the entire electromagnetic spectrum, not just in the optical wavelengths our eyes see.

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Newly discovered potentially dangerous asteroid found to be a contact binary

11:38 am

Radar images of asteroid 2024ON
Click for original image.

Radar images taken during the close fly of a newly discovered potentially dangerous asteroid has revealed that it is a contact binary, formed by two objects stuck together to produce a single asteroid with a peanutlike shape.

Discovered by the NASA-funded Asteroid Terrestrial-impact Last Alert System (ATLAS) on Mauna Loa in Hawaii on July 27, the near-Earth asteroid’s shape resembles that of a peanut. Like the asteroid 2024 JV33 that made close approach with Earth a month earlier, 2024 ON is likely a contact binary, with two rounded lobes separated by a pronounced neck, one lobe about 50% larger than the other. The radar images determined that it is about 755 feet (350 meters) long. Features larger than 12.3 feet (3.75 meters) across can be seen on the surface. Bright radar spots on the asteroid’s surface likely indicate large boulders. The images show about 90% of one rotation over the course of about six hours.

The radar images were taken one day before that close approach of 620,000 miles on September 17, 2024, and once again show that a large number of near-Earth asteroids, as much as 14%, are contact binaries. The data also helped better refine 2024ON’s orbit around the Sun, which show that though the asteroid has the potential to hit the Earth, its path will not do so for the foreseeable future.

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What the Milky Way would look like if it was presently a star forming powerhouse

9:15 am

A galaxy as seen by Hubble and Webb
For the original images go here and here.

Cool image time! The two pictures to the right, taken respectively by the Hubble and Webb space telescopes of the same galaxy, shows us many different features of a barred galaxy, located about 35 million light years away. From the caption for the Hubble image:

This picture is composed of a whopping ten different images taken by the Hubble Space Telescope, each filtered to collect light from a specific wavelength or range of wavelengths. It spans Hubble’s sensitivity to light, from ultraviolet around 275 nanometres through blue, green and red to near-infrared at 1600 nanometres. This allows information about many different astrophysical processes in the galaxy to be recorded: a notable example is the red 656-nanometre filter used here. Hydrogen atoms which get ionised can emit light at this particular wavelength, called H-alpha emission. New stars forming in a molecular cloud, made mostly of hydrogen gas, emit copious amounts of ultraviolet light which is absorbed by the cloud, but which ionises it and causes it to glow with this H-alpha light.

Therefore, filtering to detect only this light provides a reliable means to detect areas of star formation (called H II regions), shown in this image by the bright red and pink colours of the blossoming patches filling NGC 1559’s spiral arms.

The Z-shaped blue indicates the stars and its most distinct spiral arms. Astronomers presently believe that the Milky Way is also a barred spiral like this, though its star-forming regions are thought to be far less extensive and distinct.

The Webb infrared image matches the Hubble data, with the false color blue indicating the near-infrared and the false color red the mid-infrared. As with the Hubble picture, the red indicates the galaxy’s extensive star forming regions.

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Mars loses hydrogen at very different rates, depending on the planet’s distance from the Sun

11:37 am

Hubble uv images of Mars atmosphere
Click for original image.

Scientists using data from both the MAVEN Mars Orbiter and the Hubble Space Telescope have determined that the rate in which Mars loses hydrogen and deuterium varies considerably during the Martian year, with the rate going up rapidly when the red planet reaches its closest point to the Sun. The picture to the right, reduced to post here, shows the data from Hubble.

These are far-ultraviolet Hubble images of Mars near its farthest point from the Sun, called aphelion, on December 31, 2017 (top), and near its closest approach to the Sun, called perihelion, on December 19, 2016 (bottom). The atmosphere is clearly brighter and more extended when Mars is close to the Sun.

Reflected sunlight from Mars at these wavelengths shows scattering by atmospheric molecules and haze, while the polar ice caps and some surface features are also visible. Hubble and NASA’s MAVEN showed that Martian atmospheric conditions change very quickly. When Mars is close to the Sun, water molecules rise very rapidly through the atmosphere, breaking apart and releasing atoms at high altitudes.

From this data scientists will be better able to map out the overall loss rate of water on Mars over many billions of years.

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Two-lobed asteroid imaged by radar

10:04 am

Two-lobed asteroid
Click for original image.

During the August 18, 2024 first close fly-by of a potentially-dangerous asteroid only discovered back in May, astronomers used the Goldstone dish in California to produce the high resolution radar images shown in the picture to the right, reduced and sharpened to post here.

The images were captured when the asteroid was at a distance of 2.8 million miles (4.6 million kilometers), about 12 times the distance between the Moon and Earth.

Discovered by the NASA-funded Catalina Sky Survey in Tucson, Arizona, on May 4, the near-Earth asteroid’s shape resembles that of a peanut – with two rounded lobes, one lobe larger than the other. Scientists used the radar images to determine that it is about 980 feet (300 meters) long and that its length is about double its width. Asteroid 2024 JV33 rotates once every seven hours.

Asteroids formed as contact binaries, once considered the stuff of science fiction, have now been found to be relatively common, comprising about 14% of the near Earth asteroids larger than 700 feet across that have been radar-imaged. The refined orbital data suggests this asteroid might be a dead comet, though that conclusion is unconfirmed. That orbital data also tells us that though this object has the potential of hitting the Earth, it will not do so “for the foreseeable future.”

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Scientists find oldest known reference to a solar eclipse dated approximately 6,000 years ago

9:36 am

In studying an ancient Hindu text called the Rig Veda that was compiled around 1,500 BC, scientists have found what they think is the oldest known reference to a solar eclipse, dated approximately 6,000 years ago.

You can read the peer-reviewed paper here [pdf]. From the paper’s conclusion:

We propose that the eclipse recorded in the Rig Veda refers to observations made of an eclipse around 4000 BC. By analyzing the description, we propose that the eclipse was the one that occurred in 4202 BC or else in 3811 BC. We propose that it was observed in Central Asia. To our knowledge, this is one of the oldest known references to a specific total solar eclipse mentioned in the historical literature.

The scientists came to this conclusion based on information contained and not contained in the Hindu text. The text noted the event occurred three days before the autmnal equinox, and that it occurred when that equinox occurred in the constellation Orion, when today the equinox occurs in the constellation Pisces. This reduced the number of possible eclipses to a small number during the time period around 4,000 BC. The text also lacked any mention of various Hindo myths explaining eclipses that appeared more recently, thus confirming this ancient date and telling the researchers that the nomadic people who compiled the Rig Veda were likely living in central Asia at that time.

The only two eclipses that fit the bill occurred on either October 22, 4202 BC or October 9, 3811 BC. This makes it the earliest known reference to an eclipse, far earlier than the possible eclipses that occurred in around 3340 BC and around 1300 BC.

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A galaxy with a halo and a stupendous central black hole

9:22 am

A galaxy with a halo and a stupendous black hole
Click for original image.

Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken by the Hubble Space Telescope as part of a survey of galaxies that have what astronomers call active galactic nuclei (AGNs). This galaxy, dubbed IC 4709, is about 240 million light years away.

If IC 4709’s core were just filled with stars, it would not be nearly so bright. Instead it hosts a gargantuan black hole, 65 million times the mass of our Sun. A disc of gas spirals around and eventually into this black hole, with the gas crashing together and heating up as it spins. It reaches such high temperatures that it emits vast quantities of electromagnetic radiation, from infrared to visible to ultraviolet light and beyond — in this case including X-rays. The AGN in IC 4709 is obscured by a lane of dark dust, just visible at the centre of the galaxy in this image, which blocks any optical emission from the nucleus itself.

To get a very vague sense of scale, this supermassive black hole is more than sixteen times more massive than the relatively inactive supermassive black hole in the center of the Milky Way. This imagery and data from Hubble will help astronomers better understand the interaction between the black hole and its surrounding galaxy.

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Webb finds six exoplanets, all flying in interstellar space without a star

11:11 am

Astronomers using the Webb Space Telescope have discovered six different planets ranging in mass 5 to 10 times that of Jupiter, all unattached to any star or solar system.

The most intriguing of the starless objects is also the lightest, having an estimated mass of five Jupiters (about 1,600 Earths). The presence of a dusty disk means the object almost certainly formed like a star, as space dust generally spins around a central object in the early stages of star formation, said Langeveld, a postdoctoral researcher in Jayawardhana’s group.

All of these starless planets likely formed like this one, coalescing like a star does but unlike a star never having enough mass to ignite.

The astronomers are next going to attempt to detect the atmosphere’s of these rogue exoplanets, though it is not clear exactly how they will do this unless one of the exoplanets just happened to transit across a more distant star, something that simply does not happen very often.

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A real whirlpool in space

9:52 am

A real whirlpool in space
Click for original image.
Cool image time! The picture above, cropped to post here, was taken by the Hubble Space Telescope as part of a survey of nearby galaxies that have what astronomers call an Active Galactic Nuclei (AGN), because the supermassive black hole at the center is devouring nearby material at a great rate and thus producing high energy emissions as it does so.

Many active galaxies are known to astronomers at vast distances from Earth, thanks to the great brightness of their nuclei highlighting them next to other, dimmer galaxies. At 128 million light-years from Earth, UGC 3478 is positively neighbourly to us. The data used to make this image comes from a Hubble survey of nearby powerful AGNs found in relatively high-energy X-rays, like this one, which it is hoped can help astronomers to understand how the galaxies interact with the supermassive black holes at their hearts.

The bottom line is that this spiral galaxy literally is a whirlpool, the entire galaxy spiralling down into that massive black hole in its center. One cannot help wondering why such galaxies don’t end up eventually getting completely swallowed by that black hole.

Or maybe they do, and we don’t see such things because all that is left is a supermassive black hole that emits no light or energy at all, a dark silent ghost traveling between the galaxies unseen and undetectable.

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The North Star has spots!

9:38 am

The spoted surface of Polaris
Click for original image.

Astronomers using an array of six ground-based telescopes have obtained best new data of Polaris, the North Star, including the first rough image of its surface, and discovered sunspots on its surface.

You can read the paper here [pdf]. The image to the right, taken from figure 4 of the paper, shows the surface as seen by the telescopes over two nights in April 2021. Polaris is what astronomers call a Cepheid variable star, which changes brightness on a very precise schedule as its diameter grows and shrinks. In the case of Polaris, that variation is four days long. The star’s brightness itself varies only slightly, and over the decades has even at times appeared to cease its variations.

As the true brightness of Cepheids is very predictable based on their pulse rate, these stars are one of the main tools astronomers use to determine distances to other galaxies. Knowing more about them thus has great importance to cosmological research.

The orbital motion showed that Polaris has a mass five times larger than that of the Sun. The images of Polaris showed that it has a diameter 46 times the size of the Sun.

The biggest surprise was the appearance of Polaris in close-up images. The CHARA observations provided the first glimpse of what the surface of a Cepheid variable looks like. “The CHARA images revealed large bright and dark spots on the surface of Polaris that changed over time,” said Gail Schaefer, director of the CHARA Array. The presence of spots and the rotation of the star might be linked to a 120-day variation in measured velocity.

The researchers plan to take regular images again of Polaris to better track the changes to its surface.

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New data continues to refine the margin of error for the Hubble constant

9:45 am

The uncertainty of science: New data using the Webb Space Telescope’s spectroscopic capabilities has provided a more refined measure of the expansion rate of the universe, dubbed the Hubble constant.

According to previous research, that rate could be anywhere from 67.4 to 73.2 kilometers per second per megaparsecs, depending on whether you rely on data from the Planck orbiter or that of the Hubble Space Telescope. Though this difference appears reasonable considering the uncertainties and assumptions that go into research that determines both numbers, astronomers have been unhappy with the difference. The numbers should match and they don’t.

Now new data from Webb suggests this difference really is nothing more than the margin of error caused by the many uncertainties and assumptions involved. That new Webb data measured the Hubble constant using three different methods, all similar to that used by Hubble, and came up with 67.85, 67.96, and 72.04, all in the middle of the previous two numbers from Hubble and Planck.

In other words, all the data is beginning to fall within this margin of error.

Astronomers are without doubt still going to argue about this, but it does appear that the research is beginning to coalesce around an approximate number. More important, in terms of cosmology these results confirm the theory that the expansion of the universe is accelerating (dubbed “dark energy” simply because it needs a name), since they confirm the method used to measure that expansion rate in the very distant universe.

Keep your minds open however. There remain many questions and uncertainties with all these conclusions. Nothing is settled, nor will it be likely for decades if not centuries.

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Astronomers discover a nearby star moving so fast it could even escape the Milky Way

10:20 am

Astronomers, both professional and amateur, have discovered a nearby star only 400 light years away that is moving so fast, 1.3 million miles per hour (almost three times faster than the Sun), it might very well escape the Milky Way and fly into intergalactic space in the far future.

The star, named CWISE J124909+362116.0 (or “J1249+36” for short), was first spotted by some of the over 80,000 citizen science volunteers participating in the Backyard Worlds: Planet 9 project, who comb through enormous reams of data collected over the past 14 years by NASA’s Wide-field Infrared Survey Explorer (WISE) mission. This project capitalizes on the keen ability of humans, who are evolutionarily programmed to look for patterns and spot anomalies in a way that is unmatched by computer technology. Volunteers tag moving objects in data files and when enough volunteers tag the same object, astronomers investigate.

J1249+36 immediately stood out because it was moving at about .1 percent the speed of light.

The star itself is either a very low mass red dwarf, or possibly a brown dwarf that never quite had enough mass to ignite as a star.

You can read the research paper here [pdf]. The researchers posit two possible explanations for the star’s speed. Either it was once part of a binary and thrown out when its white dwarf companion exploded as a supernova, or was once located in a densely packed globular cluster, where the interaction with other stars or even black holes could have flung it away.

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A galaxy with a ring

9:34 am

A galaxy with a ring
Click for full image.

Cool image time! The photo to the right, cropped, reduced, and sharpened to post here, was taken by the Hubble Space Telescope, and appears part of a long term survey of nearby ringed galaxies. From the caption:

MCG+07-07-072 has quite an unusual shape, for a spiral galaxy, with thin arms emerging from the ends of its barred core to draw a near-circle around its disc. It is classified, using a common extension of the basic Hubble scheme, as an SBc(r) galaxy: the c denotes that its two spiral arms are loosely wound, each only performing a half-turn around the galaxy, and the (r) is for the ring-like structure they create. Rings in galaxies come in quite a few forms, from merely uncommon, to rare and astrophysically important!

Lenticular galaxies are a type that sit between elliptical and spiral galaxies. They feature a large disc, unlike an elliptical galaxy, but lack any spiral arms. Lenticular means lens-shaped, and these galaxies often feature ring-like shapes in their discs. Meanwhile, the classification of “ring galaxy” is reserved for peculiar galaxies with a round ring of gas and star formation, much like spiral arms look, but completely disconnected from the galactic nucleus – or even without any visible nucleus! They’re thought to be formed in galactic collisions.

This galaxy is about 320 million light years away, and is also known as Abell 426. Though astronomers think that these various shapes of galaxies, from barred to lenticular to ringed, are formed from a variety of galactic collusions and interactions with each galaxy’s nucleus, that remains nothing more than an educated guess. The complexity of galaxy evolution, involving billions of years and millions of stars, is barely in its infancy, and requires a lot of assumptions because our observations only involves a mere nanosecond in that grand history.

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WISE/NEOWISE space telescope mission ends after fourteen years

9:11 pm

Comet NEOWISE, photographed by the Hubble Space Telescope
Click for full image.

Launched in 2009, the Wide-field Infrared Survey Explorer (WISE) was shut down today after almost fourteen years of successful observations, with its first years dedicated to creating an infrared survey of the sky. In 2013, after two years of hibernation, it was reactivated and renamed NEOWISE (for reasons that I have always found absurd), with the goal over the next thirteen years of mapping the sky for near Earth objects.

By repeatedly observing the sky from low Earth orbit, NEOWISE created all-sky maps featuring 1.45 million infrared measurements of more than 44,000 solar system objects. Of the 3,000-plus near-Earth objects it detected, 215 were first spotted by NEOWISE. The mission also discovered 25 new comets, including the famed comet C/2020 F3 NEOWISE that streaked across the night sky in the summer of 2020.

A Hubble image of that comet is to the right.

The mission was ended because the telescope’s orbit is now too low to provide good data. It is expected to re-enter the atmosphere and burn up before the end of the year.

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Gaia space telescope identifies more than 350 asteroids with candidate moons

9:24 am

Using the Gaia space telescope, astronomers have identified 352 asteroids that the data suggests have smaller satellite asteroids in orbit around them.

In its data release 3, Gaia precisely pinpointed the positions and motions of 150 000+ asteroids — so precisely that scientists could dig deeper and hunt for asteroids displaying the characteristic ‘wobble’ caused by the tug of an orbiting companion (the same mechanism as displayed here for a binary star). Gaia also gathered data on asteroid chemistry, compiling the largest ever collection of asteroid ‘reflectance spectra’ (light curves that reveal an object’s colour and composition).

These results need to be confirmed by direct observation, as this method does involve some assumptions and uncertainties. If these numbers are confirmed however it will give planetary scientists a better census on the percentage of asteroids with moons, which in turn can be used to create better models of the formation of the solar system as well as the evolution of asteroids over time. At the moment scientists predict about one out of every six asteroids will have a moon. This data suggests that number might be high.

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A supernova overpowers a spiral galaxy

9:34 am

A supernova overwhelms a small galaxy

Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken in early 2023 by the Hubble Space Telescope because a ground-based automated sky survey had detected a new supernovae in late 2022 in this galaxy. The spiral galaxy is dubbed LEDA 857074, and is interesting because of its bright central bar and dim and broken spiral arms.

That supernova is the bright spot inside the galaxy’s central bar. It is so bright that it almost looks like someone accidently pasted a white dot there using a graphics program. From the caption:

Astronomers have catalogued millions of galaxies, so while today tens of thousands of supernovae are detected annually, the chance that one is spotted in any particular galaxy is slim. We also do not know how actively LEDA 857074 is forming stars, and therefore how often it might host a supernova. This galaxy is therefore an unlikely and lucky target of Hubble, thanks to this supernova shining a spotlight on it! It now joins the ranks of many more famous celestial objects, with its own Hubble image.

The galaxy itself had been studied by almost no one until this supernova was discovered in it.

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