Two of my favorites: https://www.esa.int/ESA_Multimedia/Images/2025/The_best_Milk...
https://www.esa.int/ESA_Multimedia/Images/2025/01/The_best_M...
[Image Description: A model image of what our home galaxy, the Milky Way, might look like edge-on, against a pitch-black backdrop. The Milky Way’s disc appears in the centre of the image, as a thin, dark-brown line spanning from left to right, with the hint of a wave in it. The line appears to be etched into a thin glowing layer of silver sand, that makes it look as if it was drawn with a coloured pencil on coarse paper. The bulge of the galaxy sits like a glowing, see-through pearl in the shape of a sphere in the centre of this brown line.]
The "by Gaia" implies the opposite to me. Unless the "artist's impressions" are from someone named Gaia???
I'm sure you know of headlines vs details; when it comes down to it, space science relies on marketing to get some funding and interest in it, and using 100% accurate headlines is not good marketing.
Gaia is good to about 13,000 light years: https://en.wikipedia.org/wiki/File:Galaxymap.com,_map_12000_...
The Milky Way is maybe 100,000 light years in diameter. So we're only getting good distance readings on a small fraction, and nothing behind the central bulge of our galaxy. The first won't improve until we send an astrometry telescope way outside the orbit of the Earth, for better baselines, and the second is going to need a telescope sent 10,000 light years out of the galactic ecliptic.
There are other (more probable) theories about the end of the universe, and if you’re up to it you can read more here: https://en.wikipedia.org/wiki/Ultimate_fate_of_the_universe
I’m in favor of the Big Chill, since I like the concept of entropy as introduced by the second law of thermodynamics: https://en.wikipedia.org/wiki/Heat_death_of_the_universe
The planets may be consumed, when the star runs out of fuel and swells a lot, and such is the Earth's fate. But that scenario is not one that happens to black holes.
The sun is 99.86% of the mass of solar system. So if you orbit the centre of mass of the solar system, you orbit the sun, more or less. Give or take a small correction for Jupiter.
But ... there are a lot more than a hundred thousand stars in the milky way. So if I guess right, the ratio of central mass vs the rest would be very different for the Milky way? It's more of a blob.
Even at "The current best estimate of its mass is 4.2 million solar masses" it does not dominate? https://en.wikipedia.org/wiki/Sagittarius_A*
(I think anyway, I just made it up, I'm not learned in this area, just a HN shitposter)
No. The Sun's orbit is determined by the total mass of stars, gas, and dark matter interior to the orbit. This is mostly due to the stars (we're not far enough out from the center for dark matter to be the dominant component) and is on the order of several tens of billions of solar masses.
(There is a supermassive black hole at the center of our galaxy, but its mass is only about 4 million solar masses, so it's negligibly small compared to the mass of all the stars.)
The Sun in turn orbits the the centre of mass of the Milky Way. But I don't think that the mass of the Milky way's central supermassive black hole dominates in the same way.
Neat.
- "Gaia measures their positions to an accuracy of 24 microarcseconds, comparable to measuring the diameter of a human hair at a distance of 1000 km"
https://www.esa.int/Science_Exploration/Space_Science/Gaia/C...
How has that affected this result?
[1] https://blogs.esa.int/gaia/2014/06/16/preliminary-analysis-o...
Also, every mission comes to an end eventually - better to do it in the right way and have the right amount of propellent saved for either a graveyard orbit or de-orbiting. It met the mission timeline and goals.
In practice these highly precise measurements, at least in the domain I'm familiar with, become sensor fusion problems where you take a lot of sources of position info, weight them based on their accuracy, and integrate them over time. The less stable the platform, the more error is induced by the integrating over time. Nothing in that realm is really all-or-nothing, as we're seeing with Hubble as it racks up more and more failures, but the loss of the rotation will mean more error in combining position references which will mean less accurate final observations. They may no longer be that much more accurate than measurements obtained by other means.
I'm not sure if I explained that very coherently, it's a complex field that I used to write software in but, well, I was the person writing the software, not the person figuring out the theory. The general idea is that space-based instruments tend to have a bunch of different factors that go into their final accuracy and that accuracy normally gets worse over time as you run out of fuel and things degrade and ultimately stop functioning. Fortunately since space-based systems cost so much to build and launch, the teams behind them have usually put a lot of thought into how they'll continue to get the best use out of them as they get older. That often means having future plans for different missions that just don't require as much accuracy, which is the case with Gaia---it's ending this "phase" of the mission plan.
"Gaia’s fuel tank is now approaching empty"
Well, congrats to all involved to such a supremely successful and important mission. When I went to school, it was said that astronomers were happy if they get the order of a measurement right. No such excuses anymore (at least for some 2 billion "nearby" objects)!
That said, if it does exist I'm sure they'll find it eventually.
Gaia is a a satellite for mapping star positions and any possible planets past Neptune would be very faint.
It's also not a telescope in the traditional sense, it's more like a bar scanner in a supermarket but it's spinning around.
Not worth the download, as I thought that it would contain a huge panorama of the sky.
I went to study MSc in Space Science and Technology as a hobby few years ago. In one course (2022) we had an assignment to find Supernovae from recent Gaia data (Python code). Then made sure this is observable by University’s robotic telescope (and compliant with local weather forecast). Next requested the observation from the telescope and if successful, received the pictures next day. Had to analyse the results as well. It surprised me how much data there actually is available in quite open format from ESA missions.
Controlling remote telescope few thousand kilometres away was also a nice experience.
The course was S818.
.png){kind=link}