Starship Asterisk*

Tell me, what conclusions can be made about the expansion of the universe from the observation of this predicted suernova? “Hubble has showcased the modern scientific method at its best,” comments Patrick Kelly, lead author of the discovery and re-appearance papers and co-author of the modelling co...

What is causing this effect to be an attractive force? And what is the suspected correlation between this attractive force and the repelling force of dark energy? These are difficult questions and there is no clear answer yet. In particular the relation between the Casimir effect/ vacuum fluctuatio...

This tiny ball provides evidence that the universe will expand forever. [...] Today, evidence indicates that most of the energy density in the universe is in an unknown form dubbed dark energy. The form and genesis of dark energy is almost completely unknown, but postulated as related to vacuum flu...

Many of the planets are coloured dark red, meaning they have an estimated temperature of lava. Does this mean that these planets are giant balls of molten lava? Or are they hot gas giants?

There is this composition of images showing the motion of stars around the central black hole of the Milky Way. A computer animation based on these images can be found here.

If the Milky Way is not the centre of the universe, is there a way to determine where in the scheme of matter we are placed ? And further can we pinpoint the direction of the centre of the cosmos ? On large scales (larger than about 400 Mpc, where even clusters of galaxies are just 'pixels') the un...

But there are no gravitational "signals" coming from inside the event horizon. The deformation of space is neither information nor a signal. This is certainly quite true for classical General Relativity. But it does make it all the harder to get one's head around the concept of gravitons....

I too wish to ask how come the black hole has a mass of a billion suns. When I clicked on the "active galaxy" link I found that, on Jan. 10th 2008, the same black hole had a mass of 10 million suns. This means its mass is now 100 times what it was less than eight years ago! My guess is th...

isoparix wrote:From inside the ISS I assume? Any cameras mounted outside?

There are a few and you can watch the live stream here.

Thanks for the input guys but couldn't we expect the lensing effect be proportional? Proportional to what? Also keep in mind that they are simulating the full Einstein equations in a non-linear regime, so my naive guess is to not expect a linear behaviour. I found this paper about the simulation an...

Dark matter makes up about 20% of the Universe. Space.com (a reasonably reliable source ?) puts dark matter as 80% of the MASS of the universe, and 'hypothetical' http://www.space.com/20930-dark-matter.html Dark energy, also hypothetical, makes up a considerable % of the energy... To clarify the co...

While we are here, take a look at this Universe Today article. http://www.universetoday.com/75705/where-does-gravity-come-from/ Spot the flaws and fallacies ? No, I don't! Please tell me what's wrong and why! And the general trend towards gravity being less than fully explained. From your cited art...

Can we find a precis of these 1200 pages, rather than a lot of hedging about the bush.... E=MC squared was a very nice summary of a heck of a lot of theory, does anything similar exist for gravity yet. Since you asked for it: R -R g /2+Lambda g =8 pi G T /c^4. You can condense it even further to G ...

I suspect that this simulation did not take everything into account. Clearly, the two holes had a net angular momentum, but I don't think the effects of that angular momentum were necessarily preserved in the simulation after the merger. If I remember correctly, angular momentum is not conserved in...

If we go to the science bookstore and ask for a book on the finer details of precisely how gravity operates, what choice of books do we have ? What science papers or journals spell it out in precise detail. ?? You can start with this . Even though it only has 1200+ pages, it covers many of the fine...

I was surprized to see the Einstein ring keeping turning even after the complete absorption of the smaller black hole. I would tend to think that, given that (as madtom pointed out) gravitational information travels at c, once no perturbation is noticeable in the remaining event horizon (i.e the sm...

star surfer wrote:Wouldn't a merger of two (or maybe more?!) black holes generate a lot of x-rays?

The merger itself not. But black holes are usually surrounded by matter that heats up due to collisions as it circles the black hole. This matter is a powerful source of powerful x-ray and gamma radiation.

[...] is searching for 'gravitational radiation' a search for something that doesn't exist ? While gravitational waves have not been detected directly, their is strong indirect evidence for their existence. The orbits of binary pulsars decay exactly as predicted by general relativity. See here for ...

Near a black hole c is approaching 0 to an outside observer so any gravitational radiation caused by the coalescing will be observed at the same time as the event horizon - ie never. The local speed of light is always c. What does change is the wavelength of the emitted light. The closer the emitte...

These neutrinos sound to me an awful lot like dark energy. I am merely hypothesizing but to me but what else would they fall under? Maybe dark matter? Or do neutrinos fall under ordinary matter? I am clearly not a physicist... Neutrinos are part of the established standard model of particle physics...

[T]he right side of the moon shows green halo of unknown origin... Explanation: Slight color shifts are visible around the lunar edge, an artifact of the Moon's motion through the field caused by combining the camera's separate exposures taken in quick succession through different color filters.

zeecatman wrote:First post on this forum after almost a year of viewing the APOD. Newbie question!

Welcome aboard!

zeecatman wrote:Is there a name for this web-like feature near the top left of the moon?

According to this website it's called Jackson [crater].

Jupiter Submarine

• What if you released a submarine into Jupiter's atmosphere? Would it eventually reach a point where it would float? Could it navigate? — KTH

neufer wrote:

Markus Schwarz wrote:Yes, it would fit.

• So it would NOT fit.

Fixed it. Thanks!

Guest wrote:WOULD OUR GALAXY FIT IN THE SOMBRERO GALAXY?

No need to YELL! Yes No, it wouldn't fit. According to Wikipedia the radius of the Sombrero galaxy is only 30% of our Milky Way.