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Hi and welcome back! Consider my mind blown today: scientists think they’ve found an exoplanet in a whole other galaxy. To find it, they had to figure out another way to detect faraway stuff. So today, Lord Snow Presides over the way human understanding just keeps expanding.

(Guillermo Ferla.) Somewhere… out there… beneath that pale blue light… Credit: Guillermo Ferla / Unsplash

The Night I Got Teased.

When I was around 10 or 11 (so, 1980ish), I had a sleepover at my house. About eight classmates showed up for it. Eventually, one of those girls found my astronomy stuff — a bookcase jammed with astronomy magazines and books, plus notebooks and slides and other such detritus as science-loving children accumulate.

Most of my stuff revolved around the Solar System. I don’t remember how it came up, but the subject of exoplanets and extraterrestrials came up. Naturally, I said I believed in both.

If life existed on Earth, I figured, it had to exist elsewhere. If our Sun had oodles of planets and moons whizzing around it, then other stars had to have them as well. And on those planets, who knew what might exist? It seemed far more likely to me that at least some other planets hosted life — and more than that, intelligent life — than that none possibly ever could.

I might have been the host of that party, but that didn’t save me from some teasing. My schoolmates thought I was barking mad.

Exoplanet Roll Call.

Since then, though, we’ve found one exoplanet after another. One of my childhood beliefs has been verified many times over.

In fact, scientists identified the very first exoplanet just a few years after that sleepover, in 1984. That exoplanet later made the news in 2010 because scientists were able to follow its motion as it moved from one side of its star to the other.

According to, we’ve identified 4860 exoplanets. All of them exist within the Milky Way galaxy, of course. And we’re finding more all the time!

To find an exoplanet, scientists usually train their measuring/observing instruments at a star. They look to see if the star’s light dips a bit. If it does, then that might be because a planet is traveling in front of it, thus blocking that little bit of light from reaching us. Our own Moon makes the light from the Sun dip significantly from our point of view on Earth every time it travels in front of the Sun during an eclipse. Well, exoplanets do the same thing to their stars — to a much smaller extent. So the dip isn’t very big, but it does exist.

That’s the transit method of finding exoplanets. Other methods exist, including simple direct imaging, but that’s the major one. When our instruments got sensitive enough to detect that tiny bit of lessened light back in the 1990s, we began finding oodles of exoplanets.

And now, we’ve found a new possible exoplanet in a whole other galaxy.

But to find that exoplanet, we had to figure out a whole new method of detection, because our current methods just aren’t sensitive enough to do the job.

Unthinkable Distances.

According to NASA, the nearest galaxy to us is the Canis Major Dwarf Galaxy. It’s about 25k light years away from our Sun. The next closest to us is the Sagittarius Dwarf Elliptical Galaxy (70k light years away from the Sun), and the next is the Large Magellanic Cloud (179k light years).

Naturally, all of these galaxies have tons of stars. That first one, Canis Major, has about a billion stars, according to this astronomy site Cosmos.

At those distances, as you might guess, individual stars kinda bleed into each other. Details just become very difficult to impossible to discern. It’s proven very difficult to use our usual methods to find an exoplanet outside of our own galaxy.

So some scientists figured out a whole new way to find an exoplanet.

A New Way to Find an Exoplanet.

Back in 2018, scientists Nia Imara and Rosanne Di Stefano proposed a new way to find exoplanets.

This new way was based on detecting X-rays from X-ray binary star systems. These systems consist of a massive living star and either a neutron star (a collapsed once-massive star) or a black hole. In such systems, the dead star steals material from the massive living star, heating it super-hot. The heat makes it emit bright X-rays.

Now, the area emitting those X-rays tends to be small. So if a planet wanders in front of it, then it’ll block all those X-rays. That bright spot will just vanish for a bit. And that’s easier for observers on Earth to detect from far away than tiny, infinitesimal dips in light strength.

Armed with this new method, find one they did — in Galaxy M51, better known as the Whirlpool Galaxy.  And get this: that galaxy is 31 million light years away from us.

Meet Our Possible New Neighbor, Exoplanet M51-ULS-1b.

I found the initial story about this exoplanet here, on Science News. It linked me to the actual paper that’ll soon be published in Nature Astronomy. Rosanne Di Stefano leads the research team, with Nia Imara named as a significant contributor. (I can’t imagine how exciting it must be for them both to use their 2018 research to achieve this discovery!)

The exoplanet the team found lives in the Whirlpool Galaxy, more formally known as NGC 5194/Messier 51a.

I strongly suspect that these scientists focused on such a faraway galaxy simply because it’s very easy to observe. As La Wiki puts it, someone can stand in a field with binoculars and see it (and a nearby galaxy, NGC 5195/Messier 51b). Those closer galaxies I named earlier are exceedingly difficult to observe or measure in any way because there’s tons of dust between us and them. (In fact, the Canis Major Dwarf Galaxy was only discovered in 2003 — precisely because of how obscured it is from us.)

To find their new exoplanet, Di Stefano and her team searched for blinking X-rays in archives from the Chandra X-ray Observatory (a satellite telescope).  The archives they chose cover three galaxies: M51 and two others. M51 showed the kind of signal the team needed. On September 20, 2012, according to the archive, something blocked all the X-rays from the star M51-ULS-1 for “about three hours.”

Because real science involves critical thinking, the team ruled out other sources of that X-ray blockage. They were left with yep, we think this is an exoplanet.

Watch This Spaaaaaaaace.

Now, it’s possible that the team didn’t find an exoplanet at all. That Science News article (relink) contains a quote from a skeptical astrophysicist who doubts the object found is an actual exoplanet.

If this X-ray method turns out to be wrong somehow, then we’ll find out sooner or later. That’s how science works. It self-corrects based on facts. That’s why we find out the truth that way, rather than from religion (which cannot self-correct).

But if this is indeed a valid new way to find an exoplanet, then we’re set to find a whole lot more of them and at distances we couldn’t even imagine before. And either way, we’ll still be devising other new ways to find exoplanets, just because we humans are inventive that way.

When we don’t stop asking questions and fiddling around with stuff, it’s amazing what we can find out about our world and ourselves.

Today, Lord Snow Presides over the spark of curiosity that drives humans to make discoveries without end.

NEXT UP: How true-blue fundagelicals excuse Mike Stone for suing Russell Moore — even though their official holy book specifically forbids Christians from suing other Christians. See you Wednesday!

About Lord Snow Presides (LSP)

Lord Snow Presides is our off-topic weekly chat series. Lord Snow was my very sweet white cat. He actually knew quite a bit. Though he’s passed on, he now presides over a suggested topic for the day. Of course, please feel free to chime in with anything on your mind: there’s no official topic on these days. I’m just starting us off with something, but consider the sky the limit here. We especially welcome pet pictures!

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ROLL TO DISBELIEVE "Captain Cassidy" is Cassidy McGillicuddy, a Gen Xer and ex-Pentecostal. (The title is metaphorical.) She writes about the intersection of psychology, belief, popular culture, science,...