An Amateur Astronomer Discovered One-of-a-Kind Supernova Remnant

PA 30 imaged in O III on Sept 6, 2013 by KPNO from Ritter et al (2021) (left) and in S II from Fesen et al (2023) (right).

In 2013, amateur astronomer Dana Patchick was looking through images from the Wide-field Infrared Survey Explorer archive and discovered a diffuse, circular object near the constellation of Cassiopeia. He found this apparent nebula was interesting because it was bright in the infrared portion of the spectrum, but virtually invisible in the colors of light visible to our eyes. Dana added this item to the database of the Deep Sky Hunters amateur astronomers group, believing it was a planetary nebula – the quiet remnant of stars in mass similar to the sun. He named it PA 30.

However, professional astronomers who picked it up from there realized that this object is far more than it first seemed. It is, they now believe, the remnant of a lost supernova observed in 1181. And an extremely rare type at that.

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The Milky Way’s Stolen Globular Clusters

Modern astronomy holds that all major galaxies (with the Milky Way as no exception) are the accumulation of numerous small mergers. Thus, it should be expected that some of the globular clusters that are now part of our galaxy are likely inherited from other galaxies which have been cannibalized by the Milky Way, or even stolen from intact companion galaxies such as the Magellanic Clouds.

Associations between these clusters and the various progenitors began in the 1990’s, but recent research is beginning to paint a more comprehensive picture on exactly what percentage of our globular clusters were stolen, and precisely which ones.

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Quenched Galaxies in the Early Universe

Color composite JWST NIRCam image of distant galaxy JADES-GS-z13-0

Recently, much attention has been given to massive, active galaxies discovered by the JWST in the early universe. But in contrast to these active galaxies, some galaxies that the JWST has discovered have been unusually quiet with little to no active star formation.

This is surprising because the early universe had a greater density of galaxies, leading to more interactions, and thus, more star formation. So finding galaxies in which star formation has been shut down so early has astronomers puzzling over the question how to kill a galaxy?

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A Medieval Manuscript Likely Hides a Record of an Impending Recurrent Nova

Approximately every 80 years, a faint 10th magnitude star in the constellation of Corona Borealis dramatically increases its brightness. This star, T CrB, is known as a recurrent nova and last flared in 1946, peaking at magnitude 2.0, temporarily making it one of the 50 brightest stars in the night sky.

Aside from the 1946 eruption, the only other confirmed observation of this star’s outburst was in 1866. But new research by Dr. Bradley Schaefer suggests that a medieval monk may have spied T CrB brightening in 1217.

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Did a Comet Airburst Destroy a Native American Community?

Artist impression of the Tunguska event.

In 1908, when an object entered the Earth’s atmosphere above the Podkamennaya Tunguska River, it flattened 80 million trees over nearly 2,200 square kilometers, and sent atmospheric shock waves reverberating around the world. Fortunately, this event was in a remote region and very few people were believed to be killed.

But research published in Nature’s Scientific Reports in 2022 by Tankersly et al. suggested that a similar, but even more powerful comet airburst in the Ohio River Valley may have been the death knell for the Hopewell civilization, some 1,600-1,700 years ago just outside modern day Cincinnati. However, other scientists rejected the arguments.

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The Historic Discussion of Ptolemy’s Star Catalog

A page from the star catalog in a 1515 printing of Ptolemy's Almagest.
A page from the star catalog in a 1515 printing of Ptolemy's Almagest.

From the time of its writing in the 2nd century CE, Claudius Ptolemy’s Almagest stood at the forefront of mathematical astronomy for nearly 1,500 years. This work included a catalog of 1,025 stars, listing their coordinates (in ecliptic longitude and latitude) and brightnesses. While astronomers within a few centuries realized that the models for the sun, moon, and planets all had issues (which we today recognize as being a result of them being incorrect, geocentric models relying on circles and epicycles instead of a heliocentric model with elliptical orbits), the catalog of stars was generally believed to be correct.

That was, until the end of the 16th century, when the renowned observation astronomer Tycho Brahe realized that there was a fundamental flaw with the catalog: the ecliptic longitudes were low by an average of 1 degree.

What’s more, Brahe proposed an explanation for why. He suggested that Ptolemy had stolen the data from the astronomer Hipparchus some 250 years earlier, and then incorrectly updated the coordinates.

The question of whether this was a cosmic coincidence or the oldest case of scientific plagiarism is a question that historians of astronomy have argued for over 400 years.

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Two “b”‘s in the Beehive

Praesepe (aka. the Beehive Cluster)

As astronomers near the 800 mark for confirmed extra solar planets, it seems that notable milestones are becoming fewer and further between. Multi-planet systems aren’t even worth mentioning. Planets less massive than Earth? Already heard about it. Detecting atmospheres? Old news.

But a recent paper manages to sneak in one new first: The first detection of hot Jupiters in an open cluster. This discovery is not simply notable due to the novelty, but clusters have special characteristics that can help astronomers determine more of the history of the system.

The discovery was made by astronomers at Georgia State University using the “wobble” method in which they looked for the spectroscopic wiggle of spectral lines as planets tugged their parent stars around in orbit. The Beehive Cluster was chosen because it is a nearby cluster with over 1,000 member stars, many of which are similar in mass to the Sun. Additionally, the cluster is known to have an above average metallicity which is known to be correlated with planetary systems.

Searches of other open clusters have largely come up empty. Only two stars in open clusters have so far been found to have planets and both of those are around giant stars and as such, the planets are in wide orbits. This paucity is odd since stars are expected to form in clusters, and as such, the frequency of planets in clusters should be nearly the same as isolated stars.

The team used the 1.5-m Tillinghast Reflector at the Fred L. Whipple Observatory on Mt. Hopkins, Arizona observing a total of 53 stars in the cluster. Their results uncovered two new hot Jupiter planets in tight orbits around the parent, main-sequence stars. The first has an estimated mass of 0.54 times that of Jupiter while the second weighs in at 1.8 Jupiter masses.

The discovery helps to place constraints on how planets form and migrate in fledgling systems. Since massive planets such as these would need to form further out in colder parts of the circumstellar cloud, such planets would have to move inwards. The time period in which this happens has been a difficult question for astronomers to pin down. But since the Beehive cluster is only 600 million years old and these new planets are already in tight orbits, this helps to demonstrate that such migration is possible on short timescales.

While these are the first of their kind discovered in open clusters, this discovery puts the number of hot Jupiters in open clusters in rough agreement with expectations based on the number of such systems of stars that are no longer bound in clusters. This finding bridges the gap between formation and isolated stars that previous searches of open clusters had left open.

Earth Threatened By Glowing Green Asteroid?

Killer asteroid coming for the Earth?
Killer asteroid coming for the Earth?


The Daily Mail is reporting that a youtube user has found a strange object while poking around in Google Sky. It looks suspiciously like a glowing green asteroid and he claims it’s heading right for us. But before we call in the experts, let’s do a little bit of critical analysis on our own.

First off, the image raises alarm bells because of the apparent size of the object. Without knowing how far away it may be, it’s hard to say how large it would actually be, but we can put some limits on it. I looked up the region on Aladin and the angular distance between the two stars just to the upper right of the object is 1 arc minute. The object seems to be about that size, so we can use that as a baseline.

Assuming that the object was somewhere in the vicinity of Pluto (roughly 6 billion km), doing a bit of quick geometry means the object would be somewhere around 580,000 km. To put that in context, that’s about 40% the diameter of the Sun. If that were the case, this wouldn’t be an asteroid, it would be a small star. The funny thing about stars is that they tend to be somewhat bright and a lot more round. So that rules out that extreme.

But what if it were very close? At the distance of the moon, that would mean the object would be about 300 km in diameter which would make this thing slightly smaller than the largest asteroid, Ceres. However, this raises another issue: With that much mass, the object should still be pretty round. Additionally, with such a size and distance, it would be very bright. And it’s not.

2011 MD on Monday, June 27, 2011 at 09:30 UTC with RGB filter. Credit: Ernesto Guido, Nick Howes and Giovanni Sostero at the Faulkes Telescope South.
Even closer we run into additional issues. Astronomical images aren’t taken as a single color image. Images like this are taken in 3 filters (RGB) and then combined to make a color image. If the object is nearby, it moves from image to image, showing up in the final image in 3 places, each as a different color. For example, here’s an image of 2011 MD illustrating the effect. Given the object in question doesn’t have this tri-color separation going on, it can’t be nearby.

So this has pretty much ruled out anything anywhere in our solar system. If it’s close, it should have color issues and be bright. If it’s far, it’s too massive to have been missed. Outside of our solar system and it wouldn’t have any apparent motion and should be visible in other images. And it’s not.

In fact, searching the various databases from which Google Sky draws its data (SDSS, DSS, HST, IRAS, and WMAP), the killer asteroid doesn’t appear at all. Thus, it would seem that this object is nothing more than a technical glitch introduced by Google’s stitching together of images. Sorry conspiracy theorists. No Planet X or Nibiru out there this time!

A Planetary System That Never Was Teaches About Those That May Be

While Kepler and similar missions are turning up planets by the fist full, there’s long been many places that astronomers haven’t expected to find planetary systems. The main places include regions where gravitational forces conspire to make the region around potential host stars too unstable to form into planets. And there’s no place in the galaxy with a larger gravitational force than the galactic center where a black hole four and a half million times more massive than the Sun, lurks. But a new study shows evidence that a disk, potentially far enough along to begin forming planets, is in the process of being disrupted.

The new study investigates an ionized cloud of gas discovered earlier this year, plummeting in towards the black hole. The cloud has been formed into an elliptical ring with a maximum distance of 0.04 parsecs (1 parsec 3.24 light years) which is coincident with a ring of young stars that orbit the black hole. At such distances from us, astronomers have been unable to learn much about the population of stars that may exist since only the brightest, most massive stars are visible.

However, such massive stars are able to determine an age limit for the group, which has been set somewhere between 4-8 million years. This age is crucial since most low-mass stars retain gas disks and are held to form planets at an age around 3 million years young. But by an age of 5 million years, the stars have begun clearing out that disk system halting planetary formation and only one fifth of stars less than 1 solar mass retain their disks.

This entire process is even more precarious because the gravitational perturbations from the nearby black hole would begin eating away at the edge of a potential disk. Astronomers predict that this should limit the size to 12 AU in radius. For even less massive stars, this could be as small as 8 AU. Still, theory predicts that these truncated disks could form in the vicinity of the Milky Way’s black hole. But such small disks would be impossible to observe directly with present technology.

The new research suggests that one of these stars was knocked from its stable orbit in the ring in much the same way that comets in the Oort cloud are occasionally jostled into falling towards the inner solar system. There, the tidal forces from the black hole as well as heavily ionizing UV radiation created by the black hole’s accretion disk would strip the gas and dust from the parent star, which is too faint to see directly, leaving it in an elliptical orbit.

If this theory is correct, it would provide the first indirect evidence of the presence of planet forming disks near the galactic center. This comes on top of evidence from earlier this year suggesting stars may be able to form in situ near the galactic center making this region a far more dynamic place than previously expected.

Yet, even if planets do form, living near a supermassive black hole is still not a hospitable place for life. The extreme amounts of UV radiation emitted as the black hole devours gas and dust is likely to sterilize the region.

Searching for Exoplanet Oceans More Challenging Than First Thought

Earth Observation of sun-glinted ocean and clouds
Earth Observation of sun-glinted ocean and clouds. Credit: NASA


As astronomers continue to discover more exoplanets, the focus has slowly shifted from what sizes such planets are, to what they’re made of. First attempts have been made at determining atmospheric composition but one of the most desirable finds wouldn’t be the gasses in the atmosphere, but the detection of liquid water which is a key ingredient for the formation of life as we know it. While this is a monumental challenge, various methods have been proposed, but a new study suggests that these methods may be overly optimistic.

One of the most promising methods was proposed in 2008 and considered the reflective properties of water oceans. In particular when the angle between a light source (a parent star) and an observer is small, the light is not reflected well and ends up being scattered into the ocean. However, if the angle is large, the light is reflected. This effect can be easily seen during sunset over the ocean when the angle is nearly 180° and the ocean waves are tipped with bright reflections and is known as specular reflection. This effect is illustrated in orbit around our own planet above and such effects were used on Saturn’s moon Titan to reveal the presence of lakes.

Translating this to exoplanets, this would imply that planets with oceans should reflect more light during their crescent phases than their gibbous phase. Thus, they proposed, we might detect oceans on extrasolar planets by the “glint” on their oceans. Even better, light reflecting off a smoother surface like water tends to be more polarized than it might be otherwise.

The first criticisms of this hypothesis came in 2010 when other astronomers pointed out that similar effects may be produced on planets with a thick cloud layer could mimic this glinting effect. Thus, the method would likely be invalid unless astronomers were able to accurately model the atmosphere to take its contribution into consideration.

The new paper brings additional challenges by further considering the way material would likely be distributed. Specifically, it is quite likely that planets in the habitable zones without oceans may have polar ice caps (like Mars) which are more reflective all around. Since the polar regions make up a larger percentage of the illuminated body in the crescent phase than during the gibbous, this would naturally lead to a relative diminishing in overall reflectivity and could give false positives for a glint.

This would be especially true for planets that are more oblique (are “tilted”). In this case, the poles receive more sunlight which makes the reflections from any ice caps even more pronounced and mask the effect further. The authors of the new study conclude that this as well as the other difficulties “severely limits the utility of specular reflection for detecting oceans on exoplanets.”