#ask ethan

Ask Ethan: Is It Really Impossible For A Jupiter-Like Planet To Orbit A White Dwarf?

“I just read we found a Jupiter sized planet orbiting a white dwarf star. [The article] said the planet found a way to survive the supernova explosion. Is it possible the white dwarf simply captured a rogue planet after the supernova?”

Earlier this month, a surprise finding was announced. NASA’s TESS mission had been surveying white dwarfs in our local neighborhood, looking for any transiting planets that might have survived. In principle, there could still be planets at an intermediate distance (farther than Earth is from the Sun) from these stellar remnants. But what they found was a huge surprise: around one of those stars, WD 1856+534, a Jupiter-sized exoplanet has survived, blocking up to 56% of the parent white dwarf’s light. But it completes an orbit in just 1.4 days (34 hours), having somehow survived the evolution of its giant star progenitor.

Charlie and Ethan, what's something you hate about each other?

-milk

Charlie: I hate his midnight snack routine. He is so obnoxious when getting plates out of the cabinet. Then he slams the cabinets shut. One day, I’m going to smack him with a plate.

Ask Ethan: How Do We Know How Old The Universe Is?

“It’s true that there are still many mysteries left to be uncovered about the Universe. We don’t know how fast the Universe is expanding, and we don’t know why different methods of measuring the expansion rate give such wildly different results. We don’t know what dark matter or dark energy are, or whether General Relativity — from which all this is derived — is still valid on the largest of cosmic scales. We don’t even know exactly how much of the Universe is locked up in which form of energy: it could have more dark matter and less dark energy than we think or vice versa; the uncertainties are substantial.

But we do know that the data we have is all consistent with one particular age of the Universe: 13.8 billion years, with an uncertainty of only 1% on that value. It cannot be a billion years older or younger than this figure, not unless a whole host of things that we’ve measured have driven us to wildly incorrect conclusions. Unless the cosmos is lying to us, or we’re unwittingly fooling ourselves, what we know of as the hot Big Bang occurred between 13.67 and 13.95 billion years ago: no less and no more. Don’t believe any claims to the contrary without comparing them to the full suite of data!”

You’ve probably heard the answer before: the Universe is 13.8 billion years old. But how do we know that’s the age of the Universe? What uncertainties are there? And if the Universe is expanding at a faster (or slower) rate than we presently thought, does that change the answer?