> GJ 486 b takes less than 1.5 Earth days to orbit its star and is probably tidally locked
Are there any discovered planets where a year is confirmed to be a day?
Are there any discovered planets where a year is confirmed to be a day?
“Okay so we have 12 months. About half are 30 days and the other half are 31 days but then ONE of them is 28 days except every fourth year that month with 28 days has a 29th day”
1. They refer to three distinct and largely independent phenomena: the rotation of the Earth about its axis (day, and subdivisions hours, minutes, and seconds), the orbit of the Moon around Earth (month, with caveats), and the orbit of Earth around the Sun (year). The fact that there is a rough days-based approximation of each is coincidental. Consider that on some planets there is no clear definition of a day (e.g., gas giants with no observable solid ground), or fixed rotational period (the duration of Venus's "day" apparently varies considerably under the influence of winds, and even Earth's day changes measurably due to tidal influences and factors).
2. Collective agreement and tradition are a real bear. It took nearly 500 years for the Gregorian Calendar to be universally adopted --- Russia's "October Revolution" occurred in what most of Europe considered to be November, as Russia had not yet adopted the Gregorian Calendar first introduced in October 1582. And it wasn't even the last country to do so! China's adoption of the Gregorian Calendar occurred in the 1940s. Calendrical decimalisation has been attempted, particularly notably during the French Revolution (amongst the same reforms which brought us the Metric System), as well as in the USSR. Switching to a ten-day week was exceedingly difficult given a) the traditions of seven-day cycles, particularly in religious contexts, as well as an external world based on the seven-day week.
A great book exploring the history of the (mostly) universally-adopted Gregorian system is Eviatar Zerubavel's Seven Day Circle: <https://openlibrary.org/works/OL1962761W/The_seven_day_circl...>
That is, measurable changes to Earth's rotation have been observed following major earthquakes. Small, mind, but measurable.
In reference to the above tweet, it might surprise you to know that at times in the past (and per Wikipedia, even in some cultures today[0]) March has been considered the first Month, meaning that the new year would start on March 1, the leap day would be the last day of the year, and September, October, November and December would in fact be the seventh, eighth, ninth and tenth months of the year.
Compare for example the mayan calendar. Or the orthodox, or syrian, or basically any culture's calendar. None make sense.
It's that "low" because its star also radiates way less energy than our sun.
But still, "habitable zone" means liquid water, which you might not find there given the pressures/temperatures involved. Maybe sufficiently cold spots could exist in the areas facing away from its star.
So could you say it's in the habitable zone? Depends on your understanding of the term.
Of course we don't know if other chemistries of life are possible, but that doesn't mean we can't define a habitable zone based on what we do know and expand it later if necessary.
As for looking at moons far from the star, it's barely a reliable means of confirming liquid water even within our own system, good luck detecting liquid water on an exomoon orbiting a far out exoplanet.
Mars is in our habitable zone and has plenty of evidence of having had liquid water flowing on its surface. The evidence of it having had conditions which could sustain some Earth-like life on it has only been increasing, making our current idea of habitable zones pretty promising. The fact that it currently doesn't have any liquid water on the surface has little bearing on that.
We have to narrow it down somehow.