The latest in Ph-word: May 2020

May was a month whose big physics news all came to us from the sky (and also from Chile – just read on).

*

You know how, when something ironic happens in the universe, it always happens at our expense? Well, this time something ironic happened directed at the universe: a black hole can be seen by naked eye, even though it is found in the constellation of Telescopium! :p

At a thousand light years’ distance, said black hole is the nearest one found yet. It is part of a triple star system, where apparently one of the three stars circling each other became a black hole at some point in their history.

This is one of the rare black holes which don’t interact with visible violence with their surroundings. Actually its presence was inferred (by ESO and the La Silla observatory in Chile) from the funny motion of the two stars in the system. So, when you look towards it you can see its two companion stars but the hole itself will be literally black. (And, it is visible only from the southern hemisphere, which means that almost none of this blog’s current readers can see it, bringing back the balance of the cosmic irony.)

*

You probably know already (i.e. you are tired of hearing) that matter as we know it makes only about 5% of the universe, with the rest being the mysterious dark matter and the bizarre dark energy.

But even this 5% hasn’t been accounted for! We know that it should be about that much because of cosmologists calculating it from what they know about the big bang and the times following it. But it hasn’t been observed itself. Actually the weight of the galaxies has been measured to be about half of that 5%.

Well, this might have just changed. A team used the australian ASKAP radio telescope and the chilean Very Large Telescope, and fast radio bursts in faraway galaxies, to account for the missing stuff.

If you are a regular here you’ve read about fast radio bursts, aka FRBs, before. They are weird extremely short lived and powerful flashes in the sky. Since last month it seems that they might have been explained, but for today’s discussion two things interest us: that light from FRBs reaches us and that the galaxies in which they are found can be pinpointed very precisely. And, also, that knowing their galaxies means knowing their distance from us.

Now, as sunlight gets separated into different colours when it hits a prism, so the light from the FRBs ends up with its frequencies traveling at different speeds after it hits atoms as it goes through space. And the more atoms it comes across, the larger the difference in speed between its various frequencies.

Eventually, by measuring this difference in speed and by finding the FRBs’ distances from us, those fine people could calculate how much matter is stray in outer space, away from galaxies.

It won’t be a big surprise, after all the foreshadowing, to hear that what they found matches the other half of the 5%. They calculated the actual quantity to be 1-2 atoms per the volume of a typical room, which sounds small but if it holds throughout intergalactic space then it can amount to much. The universe is a big place after all.

*

The last cute piece of news is that we probably have the first ever photo of a planet being born. The photo shows a shape starting to form inside a photogenic whirlwind of dust, some five hundred light years away.

Usually, impressive astropictures are compiled from several ones, or taken in non-visible light and then artificially turned into something that our eyes can actually see. But not this one. This one was actually shot as we see it, by the SPHERE instrument at, again, ESO’s Very Large Telescope.

SPHERE catches only polarized light, which means that it doesn’t come directly from stars but it must be reflected by dust grains. It does so in order to hunt for exoplanets; but now it outdid itself as it seems that it can even catch their conception.