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  • [intro ]

  • Imagine you're an astronomer.

  • Months ago, you requested time

  • on one of the world's most advanced telescopes,

  • and now, it's finally here.

  • Tonight is your night.

  • You set everything up,

  • careful to put in all the right parameters,

  • and spend hours taking shots of the sky.

  • But later, when you review the data, you're devastated.

  • Bright spots and streaks of light ruined tons of your photos.

  • All that work was for nothing.

  • It's an astronomer's nightmare,

  • and a scenario a lot of people are worried will become

  • more and more common.

  • Because over the next few years, t

  • here could be more than 26,000 new satellites orbiting Earth,

  • compared to the 5500 or so up there right now.

  • So the European Southern Observatory, or ESO,

  • decided to figure out what this means for astronomers.

  • In a study released last week,

  • which was accepted for publication

  • in the journal Astronomy and Astrophysics,

  • they looked at the possible impact of these new satellites

  • on different types of observations.

  • Turns out that in most cases,

  • they won't interfere as much as you might expect.

  • But for some research, they could be a big problem.

  • The surge of satellites comes from an idea multiple companies are pursuing:

  • a globally-accessible internet.

  • Satellite-based internet has been around since the '90s.

  • But the satellites used for it are so high above Earth

  • that it takes more than half a second for a signal

  • to get from you to somewhere else and back.

  • That might not seem like long,

  • but think about how annoying a half-second lag is during a video call.

  • It's just not practical.

  • These new satellites are designed for a much lower orbit,

  • though, bringing the delay down to around a 30th or 40th of a second.

  • That's similar to what you might get on a decent regular broadband connection.

  • And for people in remote or underserved areas,

  • that type of internet access could be a game-changer

  • especially if companies keep costs low.

  • So there are advantages to these satellites.

  • But astronomers have been worried about the downsides.

  • See, satellites are shiny.

  • They have to be

  • if they absorbed most of the sunlight that hit them, they'd overheat fast.

  • They also move across the sky much faster than, say, a star.

  • So if you're taking a long-exposure photo,

  • where the shutter stays open for a while,

  • you could end up with a bright streak against the background of stars.

  • Even worse, if the streak is bright enough,

  • the light could overwhelm the sensors and ruin the photo entirely.

  • But the new ESO study shows that in many cases,

  • this might not be a huge concern.

  • The most important factor is timing.

  • Generally, you can only see satellites overhead during astronomical twilight,

  • when the Sun is 12 to 18 degrees below the horizon,

  • and for an hour or so at the start and end of the night.

  • For the rest of the night, most satellites are in Earth's shadow.

  • No reflections, no problem.

  • So the issue is only within a certain timeframe.

  • And even then, for many types of observations,

  • the satellites would only cause problems for a small fraction of data.

  • Based on how the satellites would be distributed and how visible they'd be,

  • the researchers concluded that for short and medium exposures

  • meaning, 100 seconds or less

  • there wouldn't be much interference.

  • At most, about 0.5% of observations could be ruined,

  • and only during twilight.

  • And even for long exposures,

  • if you're only looking at a narrow field of the sky,

  • you're probably fine.

  • For wide-field imaging, though,

  • things could be much worse.

  • The team estimates that around 1 to 5% of exposures

  • would be ruined at the start and end of the night,

  • with higher numbers during twilight.

  • And if you have a really big telescope looking at a very wide section of the sky?

  • You're in trouble.

  • For example, at the Vera C. Rubin Observatory,

  • a powerful wide-field telescope that's under construction in Chile,

  • around a third of the exposures would be ruined

  • during the beginning and end of the night,

  • and about half during twilight.

  • The only time that would be unaffected is the middle of winter.

  • Thankfully, the team did have suggestions

  • for how to mitigate the problem

  • although they won't work for everyone.

  • The easiest move would be to just

  • not collect data during part of the night.

  • Or, if you know where the satellites are,

  • you could schedule your observations

  • for a time when your part of the sky will be satellite-free.

  • But that isn't always practical.

  • So another option would be to keep track of where the satellites are at any given time,

  • and plan accordingly.

  • For example

  • if you know a satellite will cross the telescope's field of view,

  • you can close the shutter while it passes, then reopen it.

  • But for that to work,

  • you would need to have up-to-date information

  • on the locations and trajectories of every satellite,

  • which the companies that launched them would have to provide.

  • The team also pointed out that they only studied

  • how the satellites affect observations that use light

  • in the visible and part of the infrared range.

  • They plan to publish other papers about the impacts on observations

  • in other parts of the electromagnetic spectrum,

  • like radio waves.

  • But whatever those impacts are, these satellites aren't going anywhere.

  • Many have already been launched, and the idea of a global internet won't just disappear.

  • Still, if scientists and the companies launching these satellites work together,

  • having thousands of new lights in the sky may not be as bad as it seems.

  • Thanks for watching this episode of SciShow Space News!

  • We make an episode like this every Friday, where we dive into the latest discoveries,

  • but we couldn't do it without our patrons on Patreon.

  • They keep these episodes free and open to everyone.

  • And also, they're just a great and thoughtful community.

  • If you like SciShow and want to help us make more of it,

  • you can go to patreon.com/scishow.

  • [ outro ]

[intro ]

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How Bad Are Satellite Constellations for Astronomy? | SciShow News

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    林宜悉 posted on 2020/03/30
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