All Questions

Filter by
Sorted by
Tagged with
4
votes
3answers
455 views

Conversion of matter into antimatter

Is it possible that the intense gravity of a black hole converts matter into antimatter? Does this mean that matter or energy that goes inside the black hole is converted to antimatter?
2
votes
1answer
53 views

How many Moon's Topocentric Conjunction occurs per lunar month?

It is clear that only one Moon's Geocentric Conjunction occurs per lunar month, what about the Topocentric Conjunction for a given location? without scale I can imagine many Topocentric Conjunctions ...
3
votes
1answer
2k views

Why is there a difference between the cosmic event horizon and the age of the universe?

According to wiki the cosmic event horizon is 5 Gpc but the age of the universe is about 13,7 billion years. Usually light from far galaxys needed at most 13,7 billion years to reach the earth so the ...
1
vote
1answer
78 views

How to improve efficiency in periodicity detection?

Our data set has $10^4$ data points, but has a long baseline and many gaps. If we bin the data, there would be $10^8$ data points ($[t,\rm {value}]$), but only about 1% are non-zero values. How to ...
1
vote
1answer
56 views

How to convert $K_S$ magnitude to $M_K$

My question is how do I convert a magnitude $K_S$, from a system like 2MASS, to $M_K$, and what are the differences. A use of this $M_K$ can be seen on Delfosse et al. (2000) in the $\log(M/M\odot) - ...
3
votes
1answer
40 views

mm-wavelengths Moon map, scientific case

I would like to test a telescope with a Moon observation. It is a low spectrometer-imager at 110-300 GHz with a resolution of 4 arcmin@150 GHz. Is there any scientific target that concerns the Moon ...
0
votes
1answer
62 views

Could there be a M-type asteroid beyond Jupiter?

Is there any reason to think an M-type asteroid could not have migrated beyond Jupiter and entered an orbit similar to the Centaurs?
3
votes
1answer
93 views

Propagate Earth trajectory for 1 Myr

What is the most accurate way of propagation of Earth trajectory relatively to the Sun? I need to calculate the Earth-Sun distance. Is there any library on Python? I've used before JPL Horizons, ...
1
vote
0answers
60 views

The energy density of DM (to be fluid,state parameter=-2)increases with time. Does it violate the concept of accelerating universe?

We know that dark energy with value of state parameter $\omega<-1$ is called phantom dark energy model. In this model if we assume dark energy to be a fluid with value of state parameter $\omega=-2$...
2
votes
1answer
689 views

Milky Way, view outward or inward?

I have a question about the view of the Milky Way that we can see from earth with the naked eye. I believe this to be light from the stars contained in one of the "arms" of the galaxy. I had always ...
3
votes
3answers
94 views

Get a table of Moon phase angle per day

Where can I get a table with the Moon phase angle for each day ? It's available here for a given day, but I would have to input each day of a year to get a full table. === NEW EDIT : 2019-09-18 ===...
12
votes
2answers
191 views

What will future populations of stars be like?

As stars slowly using up hydrogen and ejecting heavier elements into space, the future stars will form from nebulae that are more metal and helium rich. The question is: how does the increased ratio ...
0
votes
1answer
69 views

Moon changes position

So most nights the Moon usually rises on the right of the sky when I look through the window just like the previous night. But this night the Moon was on the left of the sky rising. Does anyone know ...
3
votes
3answers
4k views

Why can I see the dark side of the moon?

Last weekend (29/30 April) the sky in my area (Central Europe) was pretty clear and the Moon was nicely visible. Funnily, one could not only see the sunlit area of the Moon, but also the dark side* ...
1
vote
0answers
50 views

Does the spin rate of a black hole correspond to a physical feature?

If the mass and orbital period for two neutron stars is known before collapse to a black hole and the rate of spin is known after collapse, 100 revolutions per second for instance, that will correlate ...
3
votes
1answer
81 views

Gravitational lensing

I was reading about gravitational lensing. I was just curious to know if there are any formulae or methods to find the angle at which the light deflects due to strong gravitational lensing? And how ...
4
votes
1answer
35 views

How to model and subtract nebular emission lines from stellar spectrum

I have optical stellar spectra from a star forming region with spatially varying nebular background. I want to subtract the nebular lines from the stellar spectra (which are varying in intensity from ...
5
votes
3answers
147 views

How to Distinguish between Temperature and Doppler effect using Black-body radiation?

I understand that the radiation of a body can be described using the curve for black-body radiation. In the sense that a hotter body will be blue shifted and a cooler body will be red shifted. The ...
2
votes
2answers
108 views

Estimate prevalence of ʻOumuamua-style interstellar obects inside Jupiter orbit now that C/2019 Q4 (Borisov) is found?

Now we know two of them, so maybe it's not an outlier. We have two points so we can draw a line. How many similar macroscopic objects should be zipping through space at ~30 km/sec so that we would ...
0
votes
0answers
24 views

Dispersion: any software to work out the dispersed waveforms of EMW signals that propagate via interstellar medium for some distance?

Is there any software (toolbox, code, package, paid or opensource are both ok), to work out the dispersed waveforms of EMW signals (time series data are given), that propagate via the interstellar ...
3
votes
1answer
59 views

Fits file re-alignment

I would like to re-align an image using a reference image (taken from GAIA). I am aware of the software Koords developed by the Karma team: https://www.atnf.csiro.au/computing/software/karma/ ...
1
vote
1answer
124 views

How much volume of gases could be added to Mars atmosphere that the planet gravity can retain?

This article Mars atmosphere states that Today Mars atmosphere is very thin, but it was not always like this. Around 3.5 billion years ago, the red planet had a thick enough atmosphere for liquid ...
3
votes
2answers
412 views

Shouldn't we not be able to see some black holes?

Whenever there is a picture of a black hole, (even though they are artist depictions, this is how they are described) most are shown kind of in a flat disk like this. My question is, why do we see ...
1
vote
0answers
31 views

How many parent stars contributed to our solar system? [duplicate]

All of the stuff that isn't hydrogen and helium (which came from the Big Bang), that coalesced to form our solar system (the iron, the sulfur, the water, and so forth) all came from previous ...
13
votes
3answers
6k views

Is it possible that the shadow of The Moon is a single dot during solar eclipse?

During a solar eclipse The Moon covers The Sun on some places on the Earth. Now the focal point is a bit above the Earth so the shadow area is about 160 miles. In history The Moon was a bit closer to ...
2
votes
1answer
396 views

Is there anything like a supermassive white hole? How are they formed? And where are they present?

The idea of a 'super massive white hole' is sometimes discussed regarding GR,SR and the destination of material 'lost' in a black hole. Is there any good theoretical or observational evidence for ...
2
votes
2answers
260 views

What soviet telescope is this?

A friend has a vintage telescope with a broken lens, I asked him to send me its catalog so I can see if I can buy him a new one, he gave me what looks like a Russian catalog, it seems a soviet ...
7
votes
1answer
198 views

Breakthrough Starshot; could we detect similar probes flying by Earth?

If extraterrestrial civilizations were sending probes by Earth similar to our plans for Breakthrough Starshot (where the probes are only a few meters in diameter and will be moving at up to 0.2c when ...
4
votes
1answer
97 views

What is a black hole's “shadow” and the best angle to view it to measure the spin?

This excellent answer mentions several ways to try to observationally measure the spin of a rotating black hole. The third one is intriguing, but I don't understand how this works: The spin of a ...
8
votes
1answer
150 views

Is every star formed in an open star cluster?

As far as I understand, an open cluster is formed from a single molecular cloud, with each star in the cluster having roughly similar age and properties. Our Sun is not part of any star cluster, but ...
2
votes
0answers
59 views

Formation of the First Stars

I've got a few questions about the first stars to form in the universe. First off how might metalicity have impacted the formation of the first stars and also what effect would the absence of metals ...
6
votes
3answers
205 views

Can we see evidence of sunspots on other stars

Searching for exoplanets by measuring the change of a stars brightness when an exoplanet transits the star's disk also has the potential to detect exo-sunspots. Have they ever been detected?
36
votes
5answers
5k views

How do we know that black holes are spinning?

How is it possible to know if a black hole is spinning or not? If a planet is spinning, you can see it clearly but you can't really see a black hole. Next thing would be that matter interacts with ...
7
votes
3answers
198 views

When did people discover that the Earth is not an ideal sphere, but a little flattened?

When did people discover that the Earth is not an ideal sphere, but a little flattened? And if you know, who was the first person to discover it?
2
votes
4answers
147 views

What is the size of the largest asteroid orbiting the Earth, other than the Moon?

It seems odd to me that no other asteroid around the Earth is even close to the size of the Moon. Anyone have any idea about the size and orbit radius of Earth's "second moon" ?
7
votes
4answers
900 views

Is it possible to use Hubble Telescope to observe Earth in the past?

We can observe many astronomical objects and structures beyond our solar system, however our observations are as the objects appeared in the past due to the speed of light. My question: "Is it ...
-2
votes
1answer
42 views

Data in measures paper

What do this data mean please? http://cdsads.u-strasbg.fr/cgi-bin/nph-iarticle_query?1904AnOBN...8a...1N&data_type=PDF_HIGH&whole_paper=YES&type=PRINTER&filetype=.pdf
0
votes
1answer
64 views

Sky from Equator at 8,000 years Before Present?

The Stellarium software allows future views of the sky. I need an online resource (planetarium projector?) that shows pre-historical views, and from the Equator at 8,000 years before the present.
2
votes
2answers
96 views

What makes scientists already so certain that Comet C/2019 Q4 (Borisov) is a comet and not an asteroid?

US Naval Research Laboratory scientist Dr. Karl Battams has recently tweeted Unlike 'Oumuamua, whose asteroid-or-comet nature still gets debated, this one is definitely a comet. If it is ...
3
votes
0answers
57 views

Does the Sun have a numerical designation in any star catalogues?

Given the existence of large star catalogues listing millions of astronomical objects with numerical designations (such as Tabby's Star, KIC 8462852) it occurred to me that one of them might contain ...
2
votes
0answers
35 views

Any night sky image databases

I was wondering if there were any available databases for photos of the night sky. It doesn't have to feature pictures of any particular star, just has to be a large collection of photos from the ...
7
votes
2answers
577 views

Can I see Harvest moon in India?

I just saw articles which say the Harvest moon will be visible in the US. Apart from the US, in which other country can people see it? Can I see it from India?
2
votes
1answer
90 views

Storm on Earth vs. storm on Jupiter?

Why is the storm on Jupiter much stronger than storms on Earth and why don't the storms on Earth get as big as Jupiter's great red spot
21
votes
2answers
24k views

Why did Venus not lose its atmosphere without magnetic field?

It is often stated that the magnetosphere not only shields the planet from cosmic radiation, but also prevents atmospheric loss. Why then did Venus not lose most of its atmosphere if it doesn't have a ...
2
votes
1answer
23 views

Redshift, velocity, distance

How are redshift, (recessional) velocity and distance of a galaxy related? I understand what v=HD states. So I assume that Hubble measured a direct relation between the distance and recessional ...
2
votes
1answer
57 views

Existence of a mass-volume astronomical chart?

I've been wanting to make a mass-volume (or mass-radius) chart for astronomical objects ranging from asteroids to supermassive black holes on a log-log scale. A sort of 'Hertzsprung-Russel' type ...
3
votes
0answers
40 views

Why does the outside edge of a Kerr black hole ergosphere rotate at the same speed as the inner edge?

Reading through the Wikipedia on a Kerr black hole ergosphere, and this nice question on the maximal spin rate of a black hole leads me to ask: why does the outer edge of the ergosphere rotate at the ...
5
votes
1answer
53 views

What is the intensity distribution of visible light over the solar disk?

What is the distribution of the visible spectrum over the solar disk? Images of the Sun using the visible spectrum suggest that the light emmitted from the edge is almost equal to the light emmited ...
4
votes
1answer
101 views

Would two Earth-like planets on opposite sides of a Sol-like star at about 1 AU be a stable configuration?

Would two Earth-like planets on opposite sides of a Sol-like star at about 1 AU be a relatively stable configuration? I understand that there are tadpole-like orbits and the two planets may not stay ...
10
votes
3answers
911 views

antimatter annihilation in stars

Electrons annihilate with positrons produced through fusion processes in stars. Which particle interaction produces new electrons so that the sun isn't deplete of electrons? Or is something else ...

15 30 50 per page