My friends at Astro4Equity do a lot of really solid work helping underserved people get a chance to see the skies. They are about to head to Ukraine, bringing telescopes with them to show kids the sky; as dystopian as it sounds, the frequent blackouts means the skies can be dark, allowing the stars to be clearly seen. The point is to bring some metaphorical light into their very real darkness.

They’re also bringing along a film crew to make a documentary called “Hope out of Darkness”, showing how feet-on-ground astronomy can help raise spirits of people in troubled regions. Their Project Manager Cassondra Holmes has a short video on Instagram with more info.

They’re accepting donations to help fund this trip, so if you can, drop a few into their bucket, please. The sky belongs to all of us, and the good folks at Astro4Equity are really trying to make that a reality.

P.S. They’re also starting a new podcast, “Big Impact Astronomy”, talking to folks who make an impact in helping make astronomy accessible. I was interviewed for that and the episode will go up soon. Stay tuned!

A new JWST image dropped over the weekend, and along with it so did my jaw. I knew it was coming, but I didn’t know what it would look like, and when I saw it I was amazed.

The image is of Vega, one of the closer stars in the sky to the Sun. At a distance of just 25 light years it’s one of the brightest stars in the night sky, and with a mass of twice the Sun’s it’s more luminous and far bluer. Even by eye that cerulean hue can be seen, and through a telescope it’s a sapphire gem, beautiful and brilliant. 

But when viewed with JWST’s keen infrared eye, it looks entirely different.

Cooooool. Doesn’t look much like a blue star, does it? That’s because this image was taken waaaaay out in the infrared, at 25 microns, about 35 times the reddest wavelength your eye can see (the orangeish color has been added as artistic license), and you can’t see the star. It would be in the exact center, but it saturated the detector (like filling a bucket to overflowing) so they just put a black circle there in the image [link to journal paper]. 

The other reason it doesn’t look like a star is because it isn’t one. It’s a disk of debris around Vega, stretching outward for over 200 billion kilometers! 

In the 1980s, the NASA observatory Infrared Astronomical Satellite, or IRAS, took a peek at Vega, and noticed something weird: it was giving off more infrared light than expected. A lot more, like 15 times as much as expected. Stars like Vega give off a very specific amount of light at every wavelength, and Vega is in fact used as a standard for such things. Stars like this emit very little infrared, yet here was Vega, brighter than it should be at that part of the spectrum.

This had never been seen before, but astronomers figured it out pretty quickly: Vega must have a disk of material around it, like our asteroid belt but much farther out. Heated by the star, this material would be around -190°C, or about as warm as something orbiting the Sun out past Pluto (so substitute “frigidly cold” for warm if you like). Mind you, we couldn’t see this disk at all; IRAS didn’t have the resolution needed to see anything this small. But the excess infrared light was a dead giveaway.

Knowing how dust behaves, it’s possible to make some decent guesses about the dust in the IRAS observations. In fact, when I was in grad school I took a class on observational astronomy, and one of our homework assignments was to use simple assumptions about the sizes of the dust grains and the distance from the star, and use physics to model the dust given its brightness and determine how much material was there (this was in like 1987 or 88 so I don’t remember the details, but I do remember getting a number far smaller than the mass of Earth). This was literally the first actual computer program I ever wrote for science.

Over the years there have been more observations (including decent ones with ALMA), but now, with JWST, we’re getting our first really sharp look at the dust disk. By “dust” I mean rocky material similar to the stuff that was around the Sun when our planets were forming 4.6 billion years ago. In the case of Vega we call it a debris disk, generally what you find around stars well into their stage of planetary formation. The dust and ice and other material has clumped together to form planetesimals, objects around a kilometer across. These can collide and shatter, feeding the disk, as well as attract material through gravity, stealing from it. We think these are the seeds from which much larger planets can grow.

Does this mean Vega has planets? Well, that brings me to why I was surprised when I saw this image. It’s smooth. Like really smooth! I was expecting to see gaps, bumps, maybe even spirals or rings, but instead it’s just this disk that’s so smooth I literally thought for a moment it was a computer simulation and not an actual image!

Planets embedded in disks like this carve out gaps, creating dark regions like the gaps in Saturn’s rings. There is such a broad dip in brightness in the ring around 9 billion kilometers out from Vega, with a fuzzy ring around it, and a halo of fainter material outside that. But that’s pretty much it. The astronomers who took this data (including my colleague András Gáspár, who was very excited about Vega and with whom I had a short conversation about these observations over the weekend) conclude that there can’t be any planet more massive than Saturn orbiting Vega farther out than about 1.5 billion km (roughly the distance to Saturn from the Sun), or else its gravity would have sculpted the disk enough to see.

On the other hand, there’s a disk not seen here that is very close to the star, less than 150 million km. Their models indicate the inner edge of the disk we do see in the JWST images is around 600 million km from the star, so there’s likely a gap between the two. If so, that could be due to a Neptune-mass planet in the gap, but that’s far from confirmed. It’s just a possibility.

I’ll note that Vega is young, but not that young, about 700 million years old. That’s more than enough time to form planets, yet none is seen or indicated specifically in these data. That’s a little disappointing (I like planets!) but still very cool. Why doesn’t it have planets? Most stars do! So that’s something to feed planetary scientists for a while yet.

And of course I have to mention the movie Contact. If you haven’t seen it, by all means go do so. It’s terrific. Spoiler: We detect an intelligent signal coming from the star Vega, which includes instructions to build a faster-than-light wormhole. When Jodie Foster gets there, she sees a vast disk of asteroids (Carl Sagan’s book on which the movie is based was written in 1985 after the disk was discovered), so that’s accurate! She also sees a huge radio dish array, which is what beamed the signal to us, but the actual signal comes from much, much farther away… but I won’t spoil it any more. It’s a great movie, and a better book. 

Finally, a note: Vega is the fifth brightest star in the night sky, and easily visible right now after sunset. Go outside when it’s dark, and look to the west. You’ll see a triangle of three bright stars, called the Summer Triangle. Vega is the lowest to the horizon, and you might be able to see its blue hue (binoculars help a lot here). As you gaze at it, consider that astronomers throughout the centuries have looked upon it as well, and it’s only now that we’re really starting to get a good look at it.

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