[ThTh1] Stars vary widely in their properties. Some are ancient; other are newly formed. Some are cold and red; others are hot and blue. But while stars are insanely complex, their basic properties can be determined by their mass, their age and their chemical composition. The mass of a star is probably the most important of those because stars for all the nuclear fireworks, stars are ultimately powered by gravity.
The most massive stars are probably as big as Eta Carina — about 150 times the mass of the Sun. Beyond that, the nuclear fires in the core will burn so hot, the star will blow itself apart. The smallest stars are about 8 or 9% of the mass of the Sun. Below that you get what are called brown dwarfs — object too small to ignite fusion in their cores. They will glow faintly in the infrared as they slowly contract and release gravitational energy.
This week, NASA announced the first detection of winds on the surface of a brown dwarf using the recently retired Spitzer Telescope. This gives us our first real look at the atmospheres of these faint difficult-to-detect objects. And the technique could be applied to study the atmospheres of exoplanets.
[ThTh2] I occasionally see tweets and posts noting that severely ill COVID-19 patients are less likely to be smokers than the general population and wondering if this means smoking gives a protective effect. The answer is no. COVID-19 patients tend to be predominantly old — 65 or older. And those patients are less likely to be smokers because smokers tend to die young. So…I guess smoking kinda protects you from COVID if you define “protecting” as “killing you before can catch it”.
[ThTh3] The Hubble Space Telescope turned 30 and to celebrate, they launched a site where you can plug in your birthday and get an image Hubble took on that day (no year necessary). I would do it except that I already won the birthday sweepstakes as a graduate student when Hubble took data for me on my birthday.
No, that’s not a humblebrag. It’s a straight-up brag. Nothing humble about it.
[ThTh4] Yeah … whatever happened with that?
Can we get an update on this https://t.co/shoMTr3k24
— zmargotz (@sissypantz) March 28, 2020
[ThTh5] A long but interesting post on the failure of prediction when it comes to the Coronavirus.
[ThTh6] A couple of throughputs ago, I mentioned Comet Atlas, a new comet that looked to be naked-eye visible. Well … comets are capricious. And this one has broken up. So we won’t get the spectacular show we were hoping for. But another promising candidate is on its way.
[ThTh7] So it wasn’t an alien artifact. But would you believe it came here from another solar system? I would, actually.
[ThTh8] Brightest. Supernova. Ever. Well, “ever” being the tiny slice of cosmic time humans have been looking. But still …
So what is the threshold between a brown dwarf and a gas giant?Report
Good question. It’s a bit hazy. Jupiter gives off energy as it contract as well. The technical definition is that brown dwarfs have deuterium fusion in their atmospheres, which puts the lower limit at 13 jupiter masses. But the definitions remain a bit hazy.Report
If they’re too small to produce fusion in their cores, why do they have fusion in their atmospheres?Report
There was something in the air.Report
Speaking of stars…Report