Tag: Beverly Berger

Sciency Words: Kilonova

~ J.S. Pailly ~ 2 Comments

Sciency Words: (proper noun) a special series here on Planet Pailly focusing on the definitions and etymologies of science or science-related terms.  Today’s Sciency Word is:

KILONOVA

In a recent presentation at Princeton University, Dr. Beverly Berger—an astrophysicist from LIGO—used a very interesting term.  Imagine a pair of neutron stars orbiting each other, spiraling closer and closer together, until suddenly “they go splat!” as Dr. Berger enthusiastically described it.

The more official-sounding term for this is kilonova, Dr. Berger then explained.  The term kilonova originates from this 2010 paper, which predicted that the merger of either two neutron stars or a neutron star and a black hole would produce a very bright flash of light.

The authors of that paper calculated that, at peek luminosity, this flash of light would be approximately a thousand times brighter than a nova explosion—hence “kilonova.”  (In case you’re wondering, a kilonova is still not as bright as a supernova—a supernova is “as much as 100 times brighter than a kilonova” according to this article from NASA.)

Of course the LIGO project is designed to detect gravitational waves, not bright flashes of light.  But as you can see in the highly technical diagram below, a kilonova is accompanied by subtle ripples in the fabric of space-time—gravitational waves, in other words.

In August of 2017, the LIGO project detected exactly the kinds of ripples that would indicate two neutron stars had “gone splat.”  As this article from the LIGO website explains, alerts were “sent out to the astronomical community, sparking a follow-up campaign that resulted in many detections of the fading light from the event, located near the galaxy NGC 4993.”

One thing I’m still not clear about: what happens after a kilonova?  It seems the scientists at LIGO are wondering about that too.  According to that same article from the LIGO website, the 2017 kilonova produced either the largest neutron star that we’ve ever observed OR the smallest black hole.  “Both possibilities are tantalizing and fascinating,” the article says, “but our data simply isn’t good enough to tell us one way or the other.”

Fortunately there are a few projects in development that might help us understand kilonovae—and similar cosmic cataclysms—a little bit better.  We’ll take a look at some of those upcoming projects in Monday’s post.

That Time the Galaxy Ripped Itself Apart

~ J.S. Pailly ~ 13 Comments

Do you remember that time back in 1969 when the entire galaxy ripped itself apart?  No?  Me neither.

Last week, I had the opportunity to attend a physics seminar at Princeton University.  The presenter was Dr. Beverly Berger of LIGO.  She was there to tell us all about the discovery of gravitational waves.

Part of Dr. Berger’s presentation was historical.  There were attempts to detect gravitational waves before the LIGO experiment.  The first such attempt was conducted by Joseph Weber of the University of Maryland.  Weber’s idea was that gravitational waves would cause solid objects to expand and contract ever so slightly.  This expansion and contraction would produce friction and thus heat.

In principle, this change in temperature could be measured.  So Weber constructed a giant metal cylinder to serve as a gravitational wave detector (click here to see a picture of it).  And in 1969, Weber detected his first gravitational wave!  Or at least he thought he did. There was a tiny pulse in his data which, as Dr. Berger described it in her presentation, indicated that gravitational waves were emanating from the center of our galaxy!

Except no one was able to confirm Weber’s findings, and the discovery was widely discredited as a result.  But of course we now know, thanks to LIGO, that gravitational waves do exist.  We also know (or at least we strongly suspect) that there is a supermassive black hole in the center of our galaxy, right where Weber’s gravitational waves supposedly came from.

Given all that we now know, I think it’s fair to ask if Joseph Weber might have detected gravitational waves after all.  Someone in the auditorium did, in fact, ask that question.  But no, it’s absolutely impossible.  Weber’s instruments simply weren’t sensitive enough.

According to Dr. Berger, the only way Weber’s gravitational wave detector would have detected gravitational waves is if the entire galaxy had suddenly ripped itself apart.  Obviously that didn’t happen. The galaxy is still here. [citation needed]

P.S.: I’ve had the pleasure of meeting Dr. Beverly Berger several times now.  It’s sort of a friend of a friend situation.  Anyway, Dr. Berger has very kindly introduced me to a new scientific term.  I’ll have that for you in Friday’s episode of Sciency Words!