# Tag Info

### How to test for possible negative mass of dark matter?

The paper you mention, Farnes 2018, provides an unconventional idea to explain both dark matter and dark energy. However, this idea has quickly been refuted, e.g. by Stepanian 2019 or by Socas-Navarro ...
• 4,313
1 vote

### Can Jupiter turn into a star if it radiated off enough heat?

Stellar ignition is a very complex matter since it relies on quantum tunneling. It is not an on/off state - ie you add one gram and then, boom, it explodes into a star. The higher density you get, the ...
• 111

### Why are there three bright spots in the first picture of Sagittarius A*?

Imaging artifacts This image is created by complex image reconstruction algorithms that propose alternative solutions which are averaged. Some of these alternatives do not show a ring structure but ...
Accepted

### What implications to cosmology would it have if Webb Telescope probing the far end of our observable Universe finds out a large number of galaxies?

The current "bottom-up" idea of structure formation suggests that galaxies are built up over cosmic time from the mergers of lots of smaller galaxies. There is now plenty of chemical and ...
• 110k
1 vote
Accepted

### Does the Milky Way have any impact on Earth?

If our sun was a bowling ball in the hands of the player, the earth would be a grape's seed at one of the pins. The next nearest star (another bowling ball) would be 6000 km away. So, except for the ...
• 11.7k

### About the non-intuitive announcement at 12 May 2022 of the EHT team that spin axis of Sgr A* Black Hole facing Earth?

This recent Nature publication seems to contradict the EHT claim in their presentation about the orientation of the Sgr*A BH accretion disc plane relative to the Galactic plane. Seems to me that gas ...
• 2,984

### Can Jupiter turn into a star if it radiated off enough heat?

No. It lacks sufficient mass. Stellar ignition requires a mass of 6-8% of 1 solar mass. Or 70-80 times Jupiter's mass
• 177
Accepted

### Can Jupiter turn into a star if it radiated off enough heat?

The smallest objects (given an elemental abundance mixture appropriate to a giant planet like Jupiter) that can attain hot enough interiors to ignite a sustained thermonuclear reaction are about 13 ...
• 110k

### About the non-intuitive announcement at 12 May 2022 of the EHT team that spin axis of Sgr A* Black Hole facing Earth?

I think what you mean is that the spin axis of the black hole is not aligned with spin axis of the Milky Way? NB: That's about all you can say - the conclusion of the actual science paper (Akiyama et ...
• 110k

### What does $C^{XY}_{\ell}$ mean when we weasure $a_{\ell m}$ in the sky?

It seems to be a mix between the 2 observales but are the 𝑎𝑋ℓ𝑚 and (𝑎𝑌ℓ𝑚)∗ are measured like in the first case in eq(1) with eq(2) ? Yes, for example say $X$ was temperature, then $a_{\ell m}^X$...
• 33.2k