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In BAN #1072 I wrote about a thermal infrared image of Earth and the moon taken by NASA’s ESCAPADE spacecraft. I noted that the press release said the temperatures seen ran from about -23 to 7°C, and I wrote, “that seems off to me”, since the equator should run warmer than that even at night. BAN reader Claude-Alain Roulet (who has a Physics PhD) pointed out to me that our atmosphere is opaque to thermal IR, so the emission we’re seeing is not from the ground, but from the atmosphere high above it, where temperatures are lower. That makes sense to me (and honestly I should’ve figured that out) so I retract my statement.

The annual Perseid meteor shower comes to a peak on the evening/morning of August 12/13 this year, and it’s always a good show. Depending on viewing conditions, up to 60 – 100 meteors per hour can be seen! For most folks it’ll be less, unless you can find a really dark site.

But it’ll be worth it; this year the moon is not up at all to interfere with its bright light — because on the 12^th there’s a total solar eclipse, which by definition means the moon is near the sun in the sky, so it sets at sunset and won’t be up until sunrise.

Your best bet is, again, find a dark site, but also one with wide open space so that nothing interferes with the horizon. The shower is best after local midnight (literally halfway between sunset and sunrise, so around 01:00 or so for the US), because that’s when the part of Earth you’re on is facing into the incoming meteoroids.

For more, you can read what I wrote in Scientific American for the 2023 shower, or Time and Date’s page, or for background info my Crash Astronomy episode on meteors.

There’s also this cool interactive animation from MeteorShowers.org of what the orbits of the meteoroids look like:

Good seeing and clear skies to you!

Dagnabbit, I wish astronomers could make up their minds.

Actually, that’s not true. Scientific arguments are fun, and show how we’re sometimes right at the edge of understanding.

In this case, the topic is a bit of a morbid one: When the sun dies, will Earth get eaten or not?

In about seven billion years, the sun will run out of hydrogen in its core that it can use to fuse into helium. This process releases vast amounts of energy, and is what powers the sun. The details are complicated, but when it runs out of hydrogen the outer layers of the sun will swell up and cool, turning it into a red giant. As time goes on it will shrink and expand several times, in fact.

When it’s a red giant the solar wind becomes much denser, and in a few hundred million years the sun will lose about half its mass. The strength of its gravity depends on its mass, so as the sun blows this wind the planets will be less strongly bound to it, which means they’ll slowly spiral away from the sun. For Mercury and Venus that won’t make much difference; the sun will expand enough to engulf them anyway.

But Earth is far enough away that it’s right on the edge. When the sun expands, Earth might be inside the sun…or it might not. It depends on a lot of factors, and whenever astronomers include a new one it seems the conclusions flips. At first it looked like we’re solar food, but then the next paper said nope, we’d be outside the sun, but then another bit of research says we escape that fate. It flip-flops a lot, and the last I heard we get et.

But a new paper just came out, and guess what it concludes? Guess! 

Yup. Maybe we’re safe. This time, they looked at tides [link to journal paper].

Our fate in six billion years: cooked by the swollen red giant sun. Credit: fsgregs on wikipedia 

I wrote a lengthy description of tides back on the old Bad Astronomy site, and also for Scientific American. Oversimplifying a bit, when the sun becomes a red giant, Earth’s gravity will pull a bulge up in the sun’s material toward Earth. The sun will rotate very slowly by then, and Earth orbits around it much more rapidly. So in essence Earth will drag that bulge around with it, which steals energy from its orbital motion. That in turn will drop Earth closer to the sun. If it drops enough, poof! We get engulfed.

But does it? Will this effect counteract Earth moving away from the sun as our star loses mass and its gravity weakens?

What the astronomers found is that our fate depends on the details models of how the sun loses mass, and how the tidal evolution occurs. Using updated models (including mass loss rates from the star L2 Puppis, which used to be very much like the sun but is now a red giant), they find we just squeak by, and manage to stay outside the sun.

Nice! But not really! 

Why not? Because either way, we’ll be surfing through space just outside an enormous red-hot star. The swollen sun will be around a temperature of 4,000+°C, and will be so huge it’ll occupy half the sky! So even if we’re technically outside it, we’ll still be good and truly cooked. 

Of course, we’re talking about something that won’t happen for another six billion years or more, so it’s not exactly a pressing concern. On the other hand, studies like this really help us examine the details of how stars behave when they become red giants, and could help us better understand the behavior of other stars that are red giants and also have planets. We know that dying sun-like stars produce gorgeous and intricate planetary nebulae when they die, and the shapes of these objects can depend on whether the star consumed a planet (or if it has another star as a binary companion), so there’s a direct tie-in to this work. Also, it’s just a normal thing, I think, to wonder what our solar system might look like eons hence. 

We still don’t know, exactly, but we’re learning. Maybe, hopefully, one day we’ll find out what side of the sun we fall on.

You can email me at thebadastronomer@gmail.com (though replies can take a while), and all my social media outlets are gathered together at about.me. Also, if you don’t already, please subscribe to this newsletter! And feel free to tell a friend or nine, too. Thanks!

Subscribers make visible impact flashes in my life

As I wrote in BAN Issue #1042, the upper stage of a Falcon 9 rocket is going to hit the moon next week, on August 5, 2026. The impact time is predicted to be 06:34:33 UTC (02:34:33 Eastern US time). The upper stage will impact near the crater Einstein in the northwest portion of the moon, which, unfortunately, will be lit by the sun at the time. That will make seeing any impact flash difficult.

But not impossible! A paper has come out detailing the event, and the plans to observe it. It’s not likely to be visible by amateur telescopes, but hey, “amateurs” have pretty sophisticated equipment these days, so I would encourage anyone with a good setup and some experience give it a try. You’ll need to take video — the flash will be very brief, so capturing it during a short image exposure of the sunlit moon is extremely unlikely. The paper also talks about how to share data if you get any. 

A drawing of the moon with the impact point noted. Credit: Fernando et al., 2026, modified from B. Grey 2026

If you need more details, Bill Grey’s amazing Project Pluto site has what you need, including prediction times, maps, and more.

The Falcon 9 rocket launched on January 15, 2025, taking two landers to the moon. The upper stage used up all its fuel boosting the missions, which left it on an elliptical orbit around Earth that took it past the moon. On this elliptical orbit, it moves most rapidly when it drops down to Earth, and more slowly when it’s at its apex (called apogee). This makes it hard to observe, since that means it spends most of its time far from telescopes. Still, enough observations were made to calculate a decent orbit for it, and predict when it will impact.

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Why will it make a flash? Kinetic energy! That’s the energy of motion. Think of it this way: when you throw a baseball, the more energy you give it the faster it moves. When you catch a ball, that energy is transferred to your hand, making a loud noise and rocking your hand back.

An object in space tends to be moving much more rapidly, and when it impacts something that energy released is much higher. This creates a lot of heat, and the resulting fireball makes visible (and infrared) light. The faster the object, or the higher its mass, the brighter the flash. 

It gets complicated though. As the scientists point out in their paper, the rocket booster is moving at only about 2.4 km/sec, which is actually slow compared to most natural impacts, like asteroids, which can hit at over a dozen km/sec. At such low speeds the flash is much fainter due to the physics of how the energy is transferred to the surface, so even though the booster, with a mass of 4 metric tons, is much more massive than most natural lunar impactors (which we’ve seen!) the lower speed makes the brightness very difficult to predict.

I personally won’t be hauling my butt out of bed for this, but hopefully many other astronomers will. These sorts of impacts are extremely useful in understanding the moon’s geology; since we know the mass and velocity of the object, that narrows down a lot of uncertainties in the impact, making the event generated is easier to analyze and interpret. These rocket impacts have happened before and will happen again — the linked paper has an excellent history of such things — and being able to predict and study them is a boon to lunar studies. 

It also helps understanding of space debris, which is getting to be a bigger and bigger problem (not to put too fine a point on it, but a lot of that is also thanks to SpaceX). So the more eyes on this the better.

Tip o’ the Whipple Shield to my friend and astronomer Jonathan McDowell on Bluesky for pointing out the paper.

• JWST observations of the interstellar comet 3I/ATLAS show that it is very old indeed [link to journal paper]. It has a very high ratio of heavy water (where the hydrogen atoms have an extra neutron, making them deuterium), about 20 times what’s normal for solar system comet. For ices, deuterium forms in very cold environments where there’s a lot of radiation around. That indicates it formed very far out from its parent star in a region with high star formation rates. Also, a low ratio of heavy elements in it indicate the comet formed when the universe was much younger, likely 10 – 12 billion years ago.
  

• The Hadean era on Earth covers the period from its formation to about 4 billion years ago. It’s hard to study because there are no extant rocks found that date back to that era. Why not? Until recently this was blamed on tectonics, but a team of scientists suspected impacts may also be to blame, so they modeled how impacts at that time affected the crust [link to journal paper]. What they found is that impacts were so common and so severe they actually added more heat to the crust than the internal heat of Earth itself! This kept the crust thick and partially molten, erasing any geologic surface records from that time.

You can email me at thebadastronomer@gmail.com (though replies can take a while), and all my social media outlets are gathered together at about.me. Also, if you don’t already, please subscribe to this newsletter! And feel free to tell a friend or nine, too. Thanks!

Welcome to Issue #1068 of the Bad Astronomy Newsletter! Now, for normal people, that number doesn’t necessarily have a special meaning. But for astronomy dorks it does: NGC 1068 is one of the most studied galaxies in science. By coincidence, astronomers released a totally amazing image of the galaxy taken by JWST just a few months ago. I almost wrote about it right away, but then realized I could save it for today’s issue because why not. Yes, I’m a math dork too. I contain multitudes. So here you go.

If you’ve ever wondered why astronomers always want more telescopes that cover different parts of the electromagnetic spectrum, then you really need to see the JWST image of the nearby spiral galaxy M77.

OK, even if you haven’t asked yourself that you still really need to see the JWST image of the nearby spiral galaxy M77.

M77 by JWST. Credit: ESA/Webb, NASA & CSA, A. Leroy

yeGADS

M77, aka NGC 1068, is pretty close to us as spiral galaxies go, about 45 million light-years away (so, closer than galaxies in the Virgo Cluster, for example). That means we can see it in great detail, especially with big ‘scopes like JWST.

You can see the galaxy itself in blue — though it’s not really blue; it’s actually infrared light at a wavelength of 7.7 microns, ten times longer than the reddest wavelength your eye can see, but just colored blue here so you can see it. And what you’re really seeing is dust, long chains of carbon-based molecules that are nothing if not soot. Dust is created in dying massive stars (think Betelgeuse) and blown out into space to create huge clouds. These massive stars are born in spiral arms, and die in them as well, so we see the dust clouds strung out along the spirals of galaxies like this one.

In red, though, we see something else entirely (the huge spikes going through the center are not real, but are called diffraction spikes, caused by the optics inside the telescope; they can be irritating for astronomers since they interfere with the object but dang, they’re cool looking). This is light at the much longer wavelength of 21 microns, and that’s important, because the longer the wavelength of light, the easier it is to get through dust clouds. In visible light, for example, a bright star behind a dust cloud might be completely invisible, but at 21 microns the light passes right through so we can see it. 

What you’re seeing here is dust heated in the center of the galaxy, and I do mean the very center. Because sitting there at the exact center of M77 is a supermassive black hole that weighs in at many millions of times the sun’s mass. There’s one called Sgr A* at the center of the Milky Way as well, but M77’s is twice as hefty, and also unlike ours is very enthusiastically gobbling down matter around it.

As this material falls into the black hole it forms a huge disk called an accretion disk, and friction causes the matter in it to get infernally hot. Between the temperature and size of the disk, this makes the center of the galaxy blast out light across the EM spectrum, easily outshining all the light from all the other stars combined.

But — and this, like Peewee’s friends, is a big but — surrounding that disk at a distance of a few light-years is a massive torus (donut-shape) of thick dust. Dust like this is opaque to visible light, so it swallows up even the immense brilliance of the accretion disk’s emission. In visible light we see nothing at all! But in the far-infrared the dust, heated by the accretion disk, glows brilliantly (note too that we don’t even really see it well at 7.7 microns, or else there would be a lot of blue mixed in with the red).

If you don’t believe me — and I wouldn’t, since that sucker is obviously booming out light in the JWST image — here’s a Hubble Space Telescope image (rotated to the same orientation) taken in ultraviolet, visible, and near-infrared light (just barely outside what he human eye can perceive, so nowhere near as long a wavelength as the JWST image):

M77 by Hubble. Credit: ESA/Hubble & NASA, L. C. Ho, D. Thilker

See what I mean? That image is spectacular, but there’s no hint of the ridiculously powerful lighthouse in the core. All that light is blocked by the thick dust. It looks like a rather typical, if gorgeous, spiral galaxy.

Thanks to a Bluesky post by the Space Telescope Science Institute, I found out about a ridiculously gorgeous JWST image of a nearby star that’s busily forming planets around it. Behold, IRAS 04302+2247! [link to journal paper]

IRAS 04302+2247, a protostar with a thick disk of material around it. Credit: ESA/Webb, NASA & CSA, M. Villenave et al.

I know, right? Click here to get a much larger 3,400 x 2,000 pixel version.

This spectacular object is a little over 500 light-years from Earth, and is part of a much larger complex of gas and dust in the constellation of Taurus, where lots of stars are forming. What you’re seeing—well, what you’re not seeing, to be truthful—is a very young star, called a protostar, probably less than a million years old. The protostar is surrounded by the material from which it formed, and we see that as the gorgeous wispy material to the left and right.

Closer in, the material gets brighter, and right at the center is that vertical dark line — that’s a dense disk of matter swirling around the protostar. It’s so thick, in fact, that it completely blocks all the light from the star forming in the middle, which is why I said you’re not seeing it. By happenstance we see this disk almost exactly edge-on, so it looks like a thick line.

This is a JWST image, which means what you’re seeing is infrared light. That kind of light is usually pretty good at making its way out of dust and gas (it’s why firefighters sometimes use IR goggles to see people in smoke-filled rooms), but in this case the disk is so dense not even infrared gets out, so it appears black.

That disk is what planets form from! So this protostar is not only still forming itself, but it’s making its family at the same time. Awwww.

Butterfly-shaped nebulae (nebula is Latin for “fog”) are common in these sorts of objects. The star can blow a thin wind of material in all directions, but in the equatorial plane it hits that disk and stops, so it can only flow away above and below the disk, creating the wings. For IRAS 04302+2247, the wings aren’t symmetric, which is interesting. The one on the left is fainter than the one on the right — note that the wings are not glowing on their own; they’re reflecting light from the protostar. There are a lot of reasons this asymmetry can happen. For example sometimes there is material near the star that can block the light, creating a shadow, so one wing appears dimmer than the other; however it’s not clear what’s happening here.

Detailed measurements of the disk itself and the material immediately around it indicate they aren’t symmetric either. The astronomers who took this image think this could be due to an odd structure in the disk. Instead of being completely flat, the very innermost part of it closest to the protostar might be tipped, which causes the lighting to change a little bit. The slanted inner part could be due to the disk not being lined up with the star’s powerful magnetic field; or the protostar might actually be a binary, two stars orbiting, and the orbital plane is tipped to the disk, torqueing it; or it could be due to a still-forming giant planet near the star that isn’t orbiting in the plane of the disk (maybe it got too close to another giant planet and got thrown off into an inclined orbit). At the moment the observations don’t distinguish between these or other possible causes.

Just remember, the sun and our solar system may have looked a lot like this some 4.6 billion years ago. When we study these objects, we are peering into a version of our past, and from it we learn about how we literally came to be.

As I’ve written about a zillion times, different atoms emit different kinds of light when they’re excited. Zap them with, say, ultraviolet light, and an electron jumps up the energy levels. When it drops back down, it emits photons at very specific wavelengths, depending on the atomic number of the element and the energy levels it jumps from and to. In astronomy, we use this to identify what different objects are made of, and the abundances of the elements in them.

Tom Fields, an amateur astronomer who writes spectroscopy software for amateurs, has created a pretty cool poster that shows this. It’s set up like the Periodic Table of Elements you see in every chemistry classroom, but instead of info on the element it shows the actual emission spectrum for that element. It would look great on a science classroom wall or any nerd’s office. The linked page above has details.

The Periodic Table of Spectra lines poster. Credit: Tom Fields

Disclaimer: I don’t make any money or anything like that from this; I just think it’s cool.

I have more info on this kind of spectrum in Crash Course Astronomy, and this is a reminder to myself that I should probably do a more detailed write up explaining how this works. I talk about spectra a lot — it’s the key to all astrophysics, really — and having a basic explainer would be handy (especially for hydrogen and oxygen, the most common ones I talk about). Sigh. I’ll put it on my to-do list, which is expanding so rapidly the end is redshifted. Which I could measure with emission line spectra like these.

You can email me at thebadastronomer@gmail.com (though replies can take a while), and all my social media outlets are gathered together at about.me. Also, if you don’t already, please subscribe to this newsletter! And feel free to tell a friend or nine, too. Thanks!

Subscribers move my barycenter

Omega Centauri is the largest of the Milky Way Galaxy’s globular clusters, huge collections of hundreds of thousands or even millions of stars packed together into a roughly spherical ball generally a hundred light years across or so. Omega Cen (as its friends call it) is close to twice that size, and so massive it may not actually be a globular cluster at all; instead it’s likely the core of a small galaxy that was stripped of its stars by the Milky Way long ago.

Either way, it’s so big and relatively close by as these things go (about 17,000 light-years) that it’s been an object of intense scrutiny for decades. In fact, it’s that long baseline of observations that has finally revealed a treasure long sought-after: a stellar mass black hole amongst the stellar crowd.

Black holes like this form when a massive star explodes, and its core collapses. Globular clusters probably had lots of these stars when they first formed billions of years ago, but stars like that are short-lived and all exploded long ago. This means there should be thousands of black holes in clusters like Omega Cen, but until now none has been found (with the exception of an intermediate mass black hole in its very center, but that’s a different species of black hole and not what we’re talking about here).

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It’s possible the black holes all got flung away. Due to a process called mass segregation, heavy objects like black holes fall to the center of the cluster as they interact gravitationally with all the stars around them, and lighter stars propagate outward. If two black holes happen to get too close together during the process they could give each other a gravity assist (the so-called “slingshot”) and throw each other out of the cluster. Others might get close enough to a binary star that one of the two stars gets ejected and the black hole winds up in orbit around the other. It’s complex, and there are lots of possibilities.

Hubble image of Omega Cen, with the star in question highlighted. Credit: ESA/Hubble & NASA, M. Häberle (MPIA)

Finding any potential black holes isn’t easy. If they’re gobbling down matter, say ripping it away from a nearby star, then they’ll emit X-rays. While observations of Omega Cen show lots of point-source X-ray emitters, they’re all neutron stars (also the remnants of collapsed cores of massive stars, but have an upper mass limit of around 2.8 times the mass of the sun). But there’s another way to find them…

If a black hole and a star are in a binary system, then they orbit their mutual center of mass, called the barycenter. Normally this motion is too small to see, but we do have some pretty good eyes.

That includes Hubble and JWST. Hubble has been observing Omega Cen for over 20 years! JWST also has keen vision and has observed it in 2025, adding to the baseline. By very carefully measuring the positions of stars in the cluster, a team of astronomers found one moving on a curved path, indicating it was orbiting a companion object. By measuring the shape of the curve, the astronomers determined the object has a mass of about 4.46 times that of the sun (± about 1 solar mass). A star that mass would be very bright (and also long dead in the ancient cluster), so, since nothing is seen, the object must be a black hole! [link to journal paper]

The normal star in the system is about 0.8 times the sun’s mass, and the pair has a decently elliptical orbit around each other with a roughly 95-year period. Along its long axis the orbit is about 9 billion kilometers across, around the same size as Neptune’s orbit around the sun.

A graph showing the visible star’s position on the sky over time (the colors represent when the observations were made), with a dashed line showing the best mathematical fits to the observations. Credit: Whitaker et al. (2026)

The figure above shows the measurements made of the position of the visible star, with its actual motion through space subtracted away to show the orbit better. The dashed line is a best mathematical fit of the orbit. Note that while it looks elliptical in the figure, we’re looking down the long axis of the ellipse, so it’s distorted heavily by perspective! The long axis is actually from about the 8 o’clock to 2 o’clock positions, nearly horizontal.

I’ll note that these measurements are phenomenally precise. The axes scales are in milliarcseconds. An arcsecond is a tiny measurement on the sky; the moon is 1,800 arcsec across. A milliarcsec is a thousandth of that! That’s much less than the size of a pixel on the Hubble and JWST cameras, and getting measurements on that scale is difficult, painstaking work.

To be clear: what they’re seeing is the physical motion of that star as it moves around the black hole! Luckily, the observations were made when the two were closest together in their mutual orbit (called periastron), so the motion was rapid enough to measure over two decades.

The uncertainties in the measurements are still substantial, though the mass is determined well enough to be pretty certain it’s a black hole. More observations with JWST (already planned) should help nail that down, though.

That’s important. A binary system like this has a finite lifetime; as it passes by other stars the two components can be pulled apart by the gravity of those stars. The astronomers calculate the mean lifetime of this system is about 800 million years, which is in itself an interesting number: it means this system isn’t primordial; that is, these stars weren’t born together. If they had the system would be about 12 billion years old, and would long ago have been torn apart. So the black hole and the star must have become bound together relatively recently.

More observations getting better measurements of the system will allow astronomers to better understand how it formed, how it’s evolved, and what its eventual fate will be. It will also help them determine how many more systems are like it in the cluster. There are almost certainly many black holes that remain undetected. Maybe they’re in longer orbits that make it harder to see the visible star’s motion. Maybe they’ve all been ejected from the cluster entirely. That seems unlikely, but only much better observations will be able to say.

Hopefully, this is the first of many such black holes found, and, even more hopefully, over time more will be found in other clusters as well (a handful have already, but only a handful). There’s still much we don’t understand about globulars — or stripped dwarf galaxies, as the case may be — and observations like this will go a long way in helping.

You can email me at thebadastronomer@gmail.com (though replies can take a while), and all my social media outlets are gathered together at about.me. Also, if you don’t already, please subscribe to this newsletter! And feel free to tell a friend or nine, too. Thanks!

Beta Pictoris (or just Beta Pic to its friends) is a fascinating star. It’s about 63 light-years away, so rather close in galactic terms, and has long been known to be an oddball. Even in the 1980s it was seen to be producing way too much infrared light—it’s a young star (about 23 million years old), part of a small group of relatively newly formed stars moving through space together. The extra infrared was likely due to dust and debris circling it, leftover from planetary formation, and warmed by the star.

In 1984 that disk was first seen, and it was a huge deal; the first time evidence of planetary formation was directly seen in an image. It’s been observed many times since, too.

Planets form from such disks, so could Beta Pic have planets? Yes! An exoplanet, Beta Pic b, was first announced in 2008, seen as a small dot near the star in images taken by the European Southern Observatory’s Very Large Telescope. Turns out it was seen in images taken in 2003 as well, but missed because it was so faint and close to the star.

A second planet, Beta Pic c, was found in 2019. It wasn’t seen directly, but the effects of its gravity tugging on planet b were detected in data looking at planet b’s motion around the star. Planet c was seen in an image just a year later. 

And now a third planet has been found, and it’s a fun story: Two teams of astronomers independently discovered it nearly simultaneously!

Beta Pictoris d (arrowed) seen in the VLT images. Planet b is the brighter blob on the left. The star’s position is marked; it was subtracted from the image to make the fainter planets visible. Credit: ESO/B. Sutlieff, M. Bonse et al.

One team was looking at data taken using the Very Large Telescope in Chile, and spotted the planet in their images [link to journal paper]. To confirm it, they then looked at publicly available archived JWST observations, and spotted the planet there, too; in fact it was in VLT data from 2014! This means the planet was actually visible much earlier, but astronomers just missed it. It’s faint, only about 1% as bright as planet b, so it’s no surprise no one noticed it. The images are noisy, and it’s easy to mistake a planet for some random blob of light. 

The second team did the opposite, kinda: they were observing Beta Pic with JWST and saw the planet in their data. They then followed up with more observations to confirm it [link to journal paper]. Both teams acknowledge the other in their papers, which is nice. The work of the two teams complement each other in some ways.

Beta Pic d, like its siblings, is a gas giant, a big planet like Jupiter, though more massive — the first team find it’s about 2.4 times as massive, the second about 2 – 4, so that’s consistent.

It orbits the star at a distance of about four billion kilometers, which corresponds to between the orbits of Uranus and Neptune around the sun. Despite that, it’s hot, about 325°C (620°F). This is because it’s young. Planets form as material in the disk around the star clumps up, collecting together to grow. Eventually this protoplanet gets enough gravity to actively draw material in, and as its gravity strengthens the material impacts at higher velocity. Imagine a planet getting hit by a dinosaur-killer asteroid every five minutes for 10 million years and you can see why these young planets are hot.

Planet d takes roughly 90 years to orbit the star once, which is enough to detect that motion directly in the images, since the first were taken in 2014 and the most recent just last year in 2025.

Images of Beta Pic taken with VLT and JWST. Credit: ESO/B. Sutlieff, M. Bonse et al.

In the VLT images the bright star is subtracted during processing; in the JWST images it’s placed behind a small disk in the telescope to block its light. Those images are all to the same scale, and the planet is arrowed. The most recent image is at the upper left, and the oldest to the lower right. The motion is obvious enough (the bright blob in the top images above and to the left of the star is planet b).

Subscribers glow brightly in the infrared

I do so love brown dwarfs. These are a weird kind of astronomical object, with masses between that of a planet and a true star. They have characteristics of both but also of neither — they are more than a dozen times the mass of Jupiter, but aren’t really much bigger, so they’re very dense even though they have thick gaseous atmospheres. They don’t have sustained fusion in their cores like stars, but can temporarily fuse lighter elements like deuterium and lithium.

And they’re so faint they’re hard to detect, even when they’re nearby. Luhman-16 is a binary brown dwarf system (two orbiting each other) that was discovered only in 2013 despite being the third closest system to the sun!

Three brown dwarfs found in the star cluster NGC 6397. Left: column: JWST infrared images. Right: Hubble visible light images; in infrared the objects are much brighter and easier to spot, though it ain’t like it’s easy. Credit: Gerasimov et al. 2024 

Another issue with finding them is that they generally don’t glow much in visible wavelengths of light (the kind we see). Because they can’t generate energy in their cores, they tend to form and then cool off over time. As they do their emitted light reddens, until eventually most of the light they give off is in the infrared.

We know of about 2,900 brown dwarfs right now, some discovered in infrared surveys, others in observations by, say, JWST. In those cases their colors (different emitted wavelengths of infrared light) are used to nail them down.

But there are other ways. Because the ones we find are so dim, they tend to be close to the sun (within a couple of hundred light-years) or else they’d be too faint to detect. Like everything else in the Milky Way, they orbit the center of the galaxy, which means they move in the sky relative to more distant, background stars. If we take images sufficiently separated in time (a few years, say) then that motion (called proper motion) can be detected. The two images can be blinked one after another, for example, and the nearby objects will appear to flicker back and forth. Or, one image can be subtracted from the other; stars will more or less disappear, but anything moving enough will be seen as a pair of objects close together, one positive (white) and one negative (black).

That’s a lot of work. How do you do it? 

You ask a huge team of dedicated and enthusiastic volunteers to join in! That’s the point of citizen science^* : get lots of people to do small tasks that can then be combined to create a much larger wealth of knowledge. This has been a huge boon in astronomy, with many projects set up to help train non-scientists on the task, test their ability, and then let them loose on the data. Studies have shown the results tend to be really accurate, which is amazing. 

One such effort is Backyard Worlds: Planet 9, part of the much larger Zooniverse project. It uses observations from the venerable Wide-field Infrared Survey Explorer (or WISE) mission to find objects that have appeared to move over time. There have been thousands — yes thousands — of volunteers who have looked at the data, and there have been over 100,000 individual submissions of candidates (many of which overlap; that is, many people seeing the same target). This generates a huge database of observations, which is then examined by professional astronomers to see if they qualify for the catalog.

The upshot: the project has found 3,006 “motion-confirmed” brown dwarfs. Three thousand! That literally more than doubles the known number of these objects, a huge score [link to journal paper].

A big part of understanding a new kind of object is simply finding as many of them as you can. As you do, trends start to show up; how bright they are versus mass, for example, or their distribution in ages or distance. All of these tell you something about the greater population, and the more you have the better the statistics get, so you can be more certain you’re seeing real trend and not weird outliers (which is exactly what happened when the first exoplanets were discovered; the ones found first were the ones easiest to find — bigger ones with short orbits — which may not be representative of the whole collection).

Two images of Gliese 229A (the incredibly bright star in both) and the brown dwarf Gliese 229B (the fainter companion), now known itself to be a binary. The left image is from a ground-based 1.5-meter telescope; the right using Hubble Space Telescope. Credit: T. Nakajima (Caltech), S. Durrance (JHU); S. Kulkarni (Caltech), D.Golimowski (JHU) and NASA

Mind you, the first legit brown dwarf found — Teide 1 — was discovered only in 1994 and announced in ‘95! Another, Gleise 229b, was discovered that same year, and is now known to be a binary system of two brown dwarfs orbiting a red dwarf. I spent some time studying that one, which is a big reason I love these objects so much.

I’m very impressed by this new work. The science is amazing, and the addition to our knowledge of brown dwarfs hugely valuable. But it also shows — once again — that these kinds of crowdsourcing work very well, and make valuable contributions to our understanding of the universe.

You can be a part of it, too! Just go to the Zooniverse site and see what projects are open. SciStarter is a GREAT site that has tons of such projects across lots of different fields of science, not just astronomy. I wrote about them back in Issue 329 when I was on a NASA panel about these projects, too.

Who knows? Join up, and you might make a real contribution to real science.

^* I’ve been told this term is falling out of favor, since the word “citizen” is rather loaded. Fair enough, but the one I see being used more now is crowdsourcing, which, sure, but is a bit generic. It fits, though, so if it catches on, fine with me.

You can email me at thebadastronomer@gmail.com (though replies can take a while), and all my social media outlets are gathered together at about.me. Also, if you don’t already, please subscribe to this newsletter! And feel free to tell a friend or nine, too. Thanks!

Hey! Don’t forget that annual subscriptions are only $45 (a 25% discount) until Friday at noon! You can upgrade from a free or monthly subscription, or give a gift to a nerdy friend. Sign up here, please!

This newsletter is issue #1060, which seems like an unremarkable number, until you realize it’s equal to the sum of all the prime numbers between 1 and 100!

2 + 3 + 5 + 7 + 11 + 13 + 17 + 19 + 23 + 29 + 31 + 37 + 41 + 43 + 47 + 53 + 59 + 61 + 67 + 71+ 73 + 79 + 83 + 89 + 97 = 1060

So tautologically it’s literally remarkable since I’m remarking on it, but also that’s just kinda fun. Math is cool.

Let’s hope I make it to issue 76,127, which is the sum of all primes from 1 to 1000! I may employ a medium to dictate the newsletters by then.

It was a pretty good week for asteroids: the Japanese mission Hayabusa2 flew past Torifune, and the Chinese mission Tianwen-2 approached 2016 HO3, aka Kamo'oalewa, in preparation to take samples.

Torifune, seen by Hayabusa2. Credit: JAXA, The University of Tokyo, Chiba Institute of Technology, Tokyo University of Science, National Institute of Advanced Industrial Science and Technology, Paris Observatory, Canary Islands Institute for Astrophysics

Torifune is a near-Earth asteroid about 450 meters end-to-end, and Hayabusa2 passed it at a distance of just 800 meters, an incredible precision given it was moving 5 kilometers per second! This was done to test such precise targeting, in case we ever need to whack an asteroid that is headed toward an Earth impact.

Torifune is weird, isn’t it? Except it really isn’t. It’s a double-lobed rubble pile, which we’re learning is actually a not uncommon shape for small asteroids. Rubble piles are literally that; collections of rocks of all sizes held together by their own gravity. If you stood on one and started throwing rocks off it, eventually there would be nothing left. That’s all it is.

There are competing ideas for how they get that peanut shape. A likely one is that it may have been more round at some point, then either suffered a big impact or spun itself up so much it started flinging away rocks (I think the latter is now considered unlikely). The material coalesced into two lumps, which then fell toward each other slowly and stuck together like two snowballs. The comet 67P/Churyumov-Gerasimenko looks very much like this, as do other small asteroids. Whatever mechanism makes them this way happens often. 

Hayabusa2 flew past Torifune never to return. The plan is for the spacecraft to meet up with the tiny 10(ish)-meter-wide asteroid 1998 KY26 in 2031.

Kamo'oalewa seen from only 20 km away. Credit: China National Space Administration

Kamo'oalewa is also a near-Earth asteroid (meaning it can get closer than about 45 million km from our planet), but is much smaller, only 27 meters long. Unlike Torifune, it looks more solid, almost like a shard of rock chipped off something bigger. Tianwen-2 is approaching it slowly, and will study the wee rock for about nine months. The plan is to retrieve samples from the surface and return them to Earth in 2027. From there the spacecraft will get a gravity assist from Earth to flyby the comet 311P/PanSTARRS sometime in the mid-2030s.

Kamo'oalewa is an odd one. It’s a quasi-satellite of Earth, meaning it has an orbit around the sun very similar to Earth’s, so from our point of view we see it following us, sometimes getting a bit closer and sometimes farther away on its elliptical orbit. The orbit is unusual, and some astronomers think it may very well be a chunk of the moon blasted into space by a big impact (maybe the one that created the crater Giordano Bruno). That would explain its appearance, too. We don’t know, but with Tianwen-2 studying so intently (and sending us a sample!) we’ll almost certainly know for sure in the coming years. 

The shot of the asteroid above was taken from 20 km away — it’s the smallest asteroid ever visited and imaged up close — so it’s not terribly sharp. However, the spacecraft will get much closer, so stay tuned for better images soon.

Subscribers warp my spacetime

If everything feels like it’s all going downhill today, there may be an astronomical reason for that: Today, July 6, 2026 is when Earth reaches aphelion^* , the farthest point from the sun on our planet’s slightly elliptical orbit. This happens at 13:30 Eastern (US) time, or 17:30 UT. Astronomers tend to measure distances using the centers of objects (the math works out best that way), and at that time the centers of Earth and the sun will be 152,087,774.4 km apart.

I got this number from the wonderful Astronomical Almanac site maintained by the US Naval Observatory; you can give it a body and a time and it will tell you all sorts of cool info. The distance page is here. Note it gives the answer in AU, or astronomical units, which is the average distance of Earth from the sun, defined as 149,597,870.7 km. So Earth will be 1.016643978 AU from the sun at that time, which you can see from the number itself is about 1.7% more than average.

As an astronomer I don’t generally celebrate aphelion, but as a newsletter writer why not use it as an excuse to have a subscription sale? So I will!

Starting today and running through Friday at noon (Eastern US time), annual premium subscriptions to this newsletter are discounted 25%, so they’re just $45 per year. Premium subscribers get three issues per week (on Monday, Tuesday, and Thursday), no ads, and can also leave comments for any issue archived on the newsletter website.

This discount applies to all new subscriptions, or upgrades from free or monthly subscriptions (if you’re currently a monthly subscriber this’ll save you 27 bucks a year). Just go to the sign-up page, enter your email, and choose the annual option (if you’re giving this as a gift to someone, click the “gift” button just above that as well).

This discount will apply for one year, so when your subscription period is up it’ll revert back to the regular price.

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Thanks! And enjoy the rest of the orbit!

^* Pronounced ap-hee-lee-un, though I’ve sometimes seen it pronounced as aff-hee-lee-un, which I think is silly. The prefix is from apo meaning “away from” and the root word is helion for sun. So I think the keeping the hard p sound makes more sense, unless you’re some kind of meathead, pronounced mee-thed.

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TESS, the Transiting Exoplanet Survey Satellite, was designed to find exoplanets orbiting nearby, bright stars. If we see the planet’s orbit edge-on, then once per orbit it partially eclipses the star, causing it to dim and brighten in a specific way. As of late May, 2026, TESS has found nearly 900 confirmed planets, and has over 8,000 candidates still to be confirmed. Impressive.

But a new planet was recently confirmed using TESS, but not at all in the usual way. This time, it was found via gravitational lensing.

This is an effect predicted by Einstein’s Theory of Relativity and confirmed. I’ve written about it oh so many times before: a massive object (called the lens) has gravity, which bends space. A photon from some object (called the source) behind the first one traveling through that space will follow the bend, like a car following a dip in a road. This has many possible effects: it can create multiple images of the source, or distort its image (if it’s, say, a galaxy), or magnify the image. It also, crucially, makes the source appear brighter, since photons that might otherwise miss us are focused toward us. It’s like piping rain into a bucket; the bucket fills faster.

This works for stars and even planets! Say a star that hosts a planet (the lensing system) is some distance away from Earth. If this system passes directly in front of a more distant star (the source) as seen from Earth, then the source star will appear to brighten in a characteristic way. It will even brighten twice; once due to the star’s gravity and another time due to the planet’s.

Mind you, the planet is far, far too faint to detect otherwise. It only reveals itself through its gravity.

The star in question (both stars are so close together in the sky they appear as one), shown by the red arrow. Credit: CDS / Aladin Lite

Well! In April 2023 the ESA Gaia mission reported a star getting brighter (which was part of its mission, detecting the brightness of over a billion stars). Given the designation Gaia23bra, it doubled in brightness very rapidly, in about a day. Interested, some astronomers dug into the TESS data archives, and found the star had been seen by that spacecraft as well [link to journal paper]. TESS observed the star every two minutes, which is a rapid enough cadence to really nail down the light curve, how the star brightened over time. Feeding that data into a well-tested set of programs that model gravitational lenses, they found the clear signature of a planet and star as the lens.

The source star is smaller and cooler than the sun, with about 90% the sun’s mass. It’s about 42,000 light-years away, which is nearly halfway across the galaxy! 

The lensing star is smaller yet, about 80% the sun’s mass. The planet, called Gaia23bra b, is about 1.6 times the mass of Jupiter, so roughly the same size as our solar system’s biggest planet. It orbits its host star at a distance of about 740 million kilometers, which is similar to Jupiter’s distance from the sun, too.

A graph showing the star brightness over time (shown in Julian Days; the tick marks are 20 days apart). The two peaks correspond to the lensing by the star and the planet. The blue points are Gaia observations, and yellow is TESS. The dashed line is a mathematical fit to the curve. Credit: Harris et al., 2026

Unsurprisingly, the star is located in the plane of our Milky Way. For this geometry to work, two stars have to pass extremely close together in the sky, so the chances of that go way up where there are lots more stars. Looking into the disk of the galaxy means looking through billions of stars (the only place where stars are denser is in the galactic core, which is where most gravitationally lensing planets have been found).

Interestingly, one of the main goals of the soon-to-be-launched Nancy Grace Roman Space Telescope is to look for gravitational lenses like this (technically called microlensing, since the more general term is reserved for when big objects like galaxies do the lensing). It will scan every 12 minutes or so for such events, slower than TESS does, so it may miss details in the light curve, but will get much more accurate brightnesses for the stars involved. So, together, Roman and TESS could make a mighty team for this sort of thing. 

At the moment, by far the majority of exoplanets found have used the transit method (the mini-eclipse way). Only a handful has been found by lensing, but that number should go way up soon. Roman is predicted to find hundreds of planets this way looking toward the Milky Way’s center. That’s extremely cool! It is due to launch in the fall, so we may be on the verge of a new explosion in exoplanet discoveries. Stay Tuned!

You can email me at thebadastronomer@gmail.com (though replies can take a while), and all my social media outlets are gathered together at about.me. Also, if you don’t already, please subscribe to this newsletter! And feel free to tell a friend or nine, too. Thanks!

Note: This Thursday issue would normally be only for Premium subscribers, but it’s an important topic so I’m sending the bulk of it to free subbies as well, with most of the info “above the fold”. Enjoy!

The largest survey of the sky ever undertaken has now begun. The Vera C. Rubin Observatory’s monster 8.4-meter telescope has opened its eye and is now taking routine images of the night sky.

Does that not sound like that big a deal? What if I tell you the camera it’s using has 3.2 billion pixels — yes, billion — and takes an image of the sky every 40 seconds? And that the patch of sky it sees in every image is a rough circle 50 times the area of the full moon on the sky? And it will scan the entire southern sky in about three nights, then repeat the process for many years?

Yeah. This will be a game changer.

The idea is to look for transients, objects that change in brightness and/or position. That includes asteroids, comets, trans-Neptunian objects, flaring black holes, stars just orbiting the Milky Way’s center, and much, much more. And it will do this with very keen eyesight indeed, with a resolution (the ability to split two objects very close together) of just 0.3 arcseconds, which is a very tiny amount: the human eye has a resolution of about 60 arcseconds. Hubble has a resolution of 0.05 arcseconds, and it’s in space where there’s no atmosphere to muck up the images. So Rubin has excellent vision.

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Astronomers already released some test images last year, and they were spectacular, but the difference now is that the telescope is automatically surveying the sky, taking image after image. These can then be compared to look for anything that changed. This has to be done by computers, of course; no human could possibly go through that much data. That is how it was done back in the day; in the late 1920 and early 30s Clyde Tombaugh discovered Pluto by blinking back and forth between two photographs of the night sky, looking for anything that moved. I’ve done this sort of thing as well, and it’s incredibly tedious.

Now try it for three billion pixels. Yeah.

This Rubin survey is called the Legacy Survey of Space and Time^* , and here’s the first release image from it: 

The first release from the LSST. Credit: NSF–DOE Vera C. Rubin Observatory/NOIRLab/SLAC/AURA

I know, it just looks like a chunk of night sky, right? But that’s because I had to shrink it to a thousand pixels wide to fit this newsletter. The high-resolution image is — and I can hardly believe I’m writing this — 56,428 x 29,949 pixels. That’s 1.7 billion pixels. Holy moly. It’s a 9.4 gigabyte file, so it may take a while to download, too. I did, but it’s so big my ancient version of Photoshop gagged on it. I was able to get The GIMP to read a lower-res version (a mere 6.4 Gb) — barely — so I cropped out a tiny piece to display below. It’s actually over 3,000 pixels wide, but again I had to shrink it to fit here, so the original is actually far higher-resolution than this: 

A teeny tiny piece of the first release image from LSST. Credit: NSF–DOE Vera C. Rubin Observatory/NOIRLab/SLAC/AURA

Yegads. So many stars! And galaxies! That feathery mist you see is what’s called galactic cirrus (it used to be called integrated flux nebula, which is more fun); extremely tenuous dust and gas that is illuminated by background starlight. That stuff is faint, and to see it so clearly here is a testament to the power of this survey.

There’s another aspect to this as well, which is not being covered as much, but was mentioned in the press release. It’s about how deep the images can get. By that astronomers mean how faint an object you can see in the images.

When you take a single image, even a long exposure, there’s a problem with noise. This has many sources, but it means fluctuations in the brightness of an image caused by a combination of random processes and internal issues with the camera. An exposure of a faint source, for example, might only get a few photons per second. That stream is not perfectly consistent, though. It might have 5 photons in the first second, but 3 in the next, then 10. That’s called photon noise, and for the super nerds among you it’s a Poissonian process. The fluctuations have a statistical relation, which goes by the square root of the number seen.

If you see, say, 100 photons total, then you expect a standard deviation of 10 photons, which means that the difference between seeing 90 and 110 photons isn’t statistically significant. But if you see 10,000 photons, the square root of that is 100, so in that case 9,900 and 10,100 photons is the expected random range seen, which is much tighter percentage-wise even though the numbers themselves are larger. So the <tl;dr> of this is, the more photons you get, the smaller the random fluctuations are, and the cleaner your image is. 

The folks at NOIRLab (who are the caretakers of the Rubin data) provided a nice example of this:

A comparison of a single image (left) with 80 (right). Credit: NSF–DOE Vera C. Rubin Observatory/NOIRLab/SLAC/AURA