3072: Stargazing 4

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Stargazing 4

Title text: We haven't actually seen a star fall in since we invented telescopes, but I have a list of ones I'm really hoping are next.

Explanation

This explanation is incomplete: Created by a 1-STAR YELP REVIEW. Do NOT delete this tag too soon. If you can fix this issue, edit the page!

This is the fourth comic in the Stargazing series, following 2274: Stargazing 3 which came out five years before. That was the longest stretch between two comics in the series so far.

The host Megan begins the introduction by referencing rude reviews of her stargazing lessons on Yelp, a popular site for rating businesses such as restaurants. The reviewers doubt that she is actually a qualified astronomer due to how simplistic her lessons are; they claim she is just saying the words that come to mind. She passes these people off as people who "hate cool space facts", as opposed to being people who hate virtually useless space facts.

Then she states that there are over 20 stars in the sky and some of them are over the age of 100. Both of these statements are true, but extreme understatements.

• A few thousand stars are visible to the unaided eye under good viewing conditions, though in a city there could be less than 20 stars visible even on a clear night.

For a normal stargazing session the event should be held in a venue with as little light pollution as possible, which could mean the middle of an urban green space, conveniently away from lighting or else specially arranging for the most inconvenient lighting to be off for the duration. However, given the unprofessional nature of Megan's lessons, there is no guarantee that this session does not take place under less-than-ideal circumstances. Or she is perpetually unlucky as daylight or clouds may further reduce visible stars.

Ignoring the need for visibility entirely, it is also estimated that there are about 200 sextillion (2×10²³) stars in the observable universe, of which around half would be somewhere 'in the sky' - that is, above the horizon - at any given moment from any place on Earth.

• Stars are typically billions of years old. While new stars are being created in nebulae all the time, it is extremely unlikely that we are seeing the nebulous start of even the shortest-lived stars within the first century of their life. One of the 'youngest' potential candidates is SN 1987A, which may be a neutron star less than 40 years old. But that is discounting the additional age it has acquired from it being approximately 168,000 light years away from us (making it actually 168,000+ years old). It is further undermined by arguably just being the next stage of life of the far older star that went supernova in order to leave the neutron star behind.

Of stars within 100 light-years of Earth and formed afresh from interstellar material, AU Microscopii is slightly over 30 light-years away and considered to be very new as far as stars go. But it is still 22 million (...and thirty) years old by current understanding.

Megan states that our galaxy is huge and that there are more grains of sand in the Milky Way than grains of sand on all of Earth's beaches. This size comparison is a parody of the common saying that there are more stars in the visible universe than grains of sand on all the beaches of Earth. Since the Earth's sand is a subset of all of the galaxy's sand, and there are more planets with sand other than Earth (such as Mars), there are unquestionably more grains of sand in the Milky Way than on Earth. Tangentially, it is unclear whether the stars outnumber Earth's sands, as shown here: Do Stars Outnumber the Sands of Earth’s Beaches? and here: The ever-lasting question: more sand or stars?. Also, the original quote was all the sand on Earth, not just on the beaches. Megan adds a helpful hint, calling a beach a big wet sandbox.

She then finishes the lesson by correctly saying that there is a black hole in the center of our galaxy (Sagittarius A*), and that stars sometimes fall in and get consumed by the black hole. When stars come too close to black holes, they experience a tidal disruption event (TDE), where a star is pulled apart (spaghettified) by the black hole after exceeding its tidal radius, or Roche limit. This creates streams of material that orbit the black hole and form an accretion disk that will eventually be consumed by the black hole or ejected in jets.

She adds her personal opinion about this fact, saying that such events are "hilarious", and proceeds by saying that it's okay to laugh at the fate of those stars as the gravity of the black hole will prevent any signals from those stars escaping. This is due to black holes' immense gravitational attraction that prevents even light from escaping. In Megan's case the most important consequence of this fact is that anyone on planets around such stars cannot leave Yelp reviews if they hear her laughing. Thus, they cannot add to those that mock her lesson.

However, as the Roche limit of a black hole for the average star it's consuming is usually greater than the size of the black hole's event horizon (Schwarzschild radius), reviews made just after the star begins spaghettification could still escape the black hole. Not only do stars not use any kind of human-made technology,^{[citation needed]} but any information regarding the app Yelp has yet to reach any star near Sagittarius A*, and will reach it only after 27,000 years. It is much more likely that someone living on one of the star's planets would try to leave a comment on Yelp, not the star itself, but in any case the same issues with distances would of course apply. It also seems unlikely that any planet would still be following a star when it first gets that close to a supermassive black hole.

In the title text Megan claims that we haven't actually seen a star fall into the black hole since we invented telescopes. While it is true that we haven't observed any star fall into our closest supermassive black hole, this phenomenon has been been observed for other black holes, and the G2 gas cloud on an accretion course was discovered in 2002. Megan also apparently has a list of stars she would like to see fall into the black hole. But she can just keep hoping, as humans at present have no way of changing the position of any star, and probably couldn't implement it soon upon such distant stars even if were possible. So unless she is hoping for one (or more) of the already closer stars to be observed to fall in next, she is unlikely to experience success for stars on her list.

Transcript

[The background is black, Megan is in front of three others, Cueball and Ponytail to the left, and White Hat to the right. Megan is drawn in white while the background characters are in grey.]

Megan: Welcome back to Stargazing.

Megan: According to some incredibly rude Yelp reviews, I'm "not informative" and "can't possibly be an astronomer" and "just kind of say words as they occur to me."

Megan: I guess some losers just hate cool space facts!

[The sky is white, the floor is black, Megan is pointing at the sky. Hairy, a Megan-like woman (with longer hair), Cueball, and Ponytail are on the left, White Hat and Hairbun are on the right. All of the characters are drawn in black.]

Megan: Anyway, that dot is a "star."

Megan: There are over 20 stars in the sky, and some of them are more than 100 years old.

[The background is black again, the panel zooms in on Megan's face.]

Megan: Our galaxy is huge.

Megan: You know the beach? That big wet sandbox?

Megan: Well, there are more grains of sand in the Milky Way than in all Earth's beaches combined.

Off-panel voice to the left: Wow.

Off-panel voice to the right: ...Wait.

[The background is still in black, Megan is in front of others and has her finger raised, Ponytail is left of Megan, White Hat and Hairbun on the right. Megan is again drawn in white while the background characters are in grey.]

Megan: The galaxy has a black hole at the center.

Megan: Sometimes stars fall in, which is hilarious.

Megan: Don't worry, it's okay to laugh. The gravity prevents signals from escaping, so they can't leave Yelp reviews.

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Discussion

Is it not possible and even likely, due to the simplistic nature of the dialog here, that the falling stars here in fact have nothing to do with black holes and merely refer to "falling stars"? 172.68.150.67 19:11, 5 April 2025 (UTC)

I think they have to do with stars falling in to the black hole. 172.69.17.125 00:53, 6 April 2025 (UTC)

I must say that my first too hasty view of the comic page had me reading "...haven't seen a star falling since...", and thus about "falling stars", i.e. meteorites (which... well, is another astronomically naïve 'fact'), but on a second reading I correctly realised it as "fall in" and therefore could only really be relating to the black hole thing that closes the comic-text.

But so easy for a minor misreading to at least lead to this. If something about Earth's atmosphere had been mentioned, perhaps it could have remained ambiguous, but I don't have any doubts about its intention. Until someone points out another way to interpret the progressive back-referencing of text, I suppose, maybe leaving either me or they adamantly trapped down the wrong garden path/rabbit hole... ;) 162.158.74.14 10:07, 6 April 2025 (UTC)

First comic explanation I've done. This is... somewhat harder than what I expected. MinersHavenM43 (talk) 02:46, 5 April 2025 (UTC)

To be clear, the comic says grains of sand on Earth's *beaches* which presumably excludes deserts and such. I think another joke with that panel might be that Earth has more sand than just the beaches. 108.162.212.31 03:21, 5 April 2025 (UTC)

Randal is rarely wrong. Have we seen TDEs (tidal disruption events) for Sag A* or only for other supermassive black holes? --172.70.242.247 07:44, 5 April 2025 (UTC)

I don't think the voice in the title text should be identified with Randall. Furthermore it is said that we haven't seen a star fall into a black hole, which is different from a TDE. --172.71.102.194 08:23, 5 April 2025 (UTC)

She's back. SHE'S BACK!!!! /ref Caliban (talk) 09:10, 5 April 2025 (UTC)

This feels like Cunk on Space 141.101.99.123 11:06, 5 April 2025 (UTC)

Indeed we never saw a TDE for Sag A* provided context for that --Trimutius (talk) 11:13, 5 April 2025 (UTC)

In the last panel and title text, Megan states it's hilarious when "stars" fall into black holes, that they can't leave Yelp reviews, and that she has a list of stars she hopes are next to fall in. Is it possible she's now conflating Hollywood stars (movie/TV personalities) with the celestial bodies? Like she has a list of entertainment personalities she bears a grudge against and wishes they would leave the country (or universe)? 172.70.126.154 11:54, 5 April 2025 (UTC)Pat

I myself had that very thought, thinking that this statement might be a double-entendre that refers to some people. Ianrbibtitlht (talk) 02:33, 6 April 2025 (UTC)

Why isn't Danish called Danish in the transcript instead of a long-haired Megan?--Darth Vader (talk) 10:43, 6 April 2025 (UTC)

That's not Danish. Danish's hair goes below her shoulders. I don't think it's Megan, either, though. The personality doesn't seem to fit Megan and the hair seems slightly longer. 172.71.150.109 15:19, 6 April 2025 (UTC)

Her hair does go quite low down (second character in second pane). Not sure what you mean about personality (this character doesn't say anything). Personally I still think its Danish. Also the comic is listed under the Danish category still...--Darth Vader (talk) 16:57, 6 April 2025 (UTC)

Still no April fools? Sad :( Aprilfoolsupdate! (talk) 11:05, 6 April 2025 (UTC)

"However, as the Roche limit of a black hole is always greater than its Schwarzschild radius,.." - I don't think so. Especially for heavy black holes the Schwarzschild radius is so far out that the tidal effects may be small. Additionally, the Roche limit depends on the structure of the small body too, while the Schwarzschild radius is just a function of the black holes mass and rotation. What does the community think? 108.162.221.151 (talk) 14:03, 6 April 2025 (please sign your comments with ~~~~)

Wikipedia cites this paper when it comes to this topic, I looked through this paper and it suggests that the event you described could happen. TomtheBuilder (talk) 16:18, 6 April 2025 (UTC)

TDEs do happen, I don't question this aspect. I think most normal stars will be strongly deformed if not torn apart but more compact, "stiffer" object can easily cross the event horizon / Schwarzschild radius of a SMBH without structural damage. I couldn't find any publication right now but I guess neutron stars woud cross the event horizon quite unaffected because they are so small and the gravitational gradient across them would be orders of magnitude smaller that its own gravitation. But the text was changed to "usually" already - can live with that :-) 172.68.50.170 (talk) 17:22, 6 April 2025 (please sign your comments with ~~~~)
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