12
votes
6answers
2k views

Is Pluto still a dwarf planet?

Recent news seem to suggest that astronomers are arguing about whether Pluto should become a planet again. However, I cannot find an official source for this. Is this actually true?
12
votes
3answers
574 views

Questions about spiral galaxy arms

I have 2 questions related to spiral galaxies. Firstly, how did the arms form? Why would the stars accumulate into those specific areas? And secondly, why are they still intact? The inner parts of ...
12
votes
1answer
1k views

Do star remnants actually burn?

As we know, some stars can fuse heavy elements to produce carbon and oxygen after using up hydrogen if they are massive, and the remnant of stars are usually hot, my question is, if a star fuse to ...
12
votes
7answers
12k views

Did atoms in human body indeed come from stars?

I think I am not alone who saw videos about that we (humans) are made of same atoms which someday were in stars. In other words, some atoms in our bodies are from stars which exploded billions of ...
12
votes
3answers
3k views

How was the core temperature of the Sun estimated?

It was estimated that the heat inside the core of the Sun inside around 15 000 000 °C - this value is extremely enormous. How did scientists estimate this value?
12
votes
2answers
301 views

What is the upper and lower limit of temperatures found on stars?

What are the most extreme temperatures (both hot and cold) stars have been detected at? Is there an upper and lower limit for the detected temperature of stars?
12
votes
2answers
259 views

What is radiation pressure and how does it prevent a star from forming?

This is a follow up to: Is there a theoretical maximum size limit for a star? The answer there talks about the radiation pressure preventing a star from forming. What reaction is causing this ...
12
votes
2answers
316 views

Dimensions of a black hole

How big can a black hole become and how small can a black hole become?(minimum and maximum dimensions of a black hole)
12
votes
1answer
402 views

Why Did Mars lose its Magnetic Field?

I had heard that Mars once had a planetary magnetic field, but that it is now gone? What happened to it?
12
votes
1answer
426 views

Has Hawking Radiation Ever Been Observed?

I know Hawking Radiation has firm theoretical footing, but has a signal ever actually been observed? What observational research is being done to attempt to see this effect? Is it simply too tall an ...
12
votes
3answers
344 views

How hot must a star get before it is considered to be a star?

How hot must a star get before it actually becomes a star? Why does it need to get so hot? Please find an official site to quote from, if you can.
12
votes
1answer
515 views

Have we ever observed a large meteor hit the Moon?

Since the moon has no atmosphere, its surface has many more meteorite impacts than Earth's does. Image source Have we ever observed a meteor strike the surface of the Moon?
12
votes
1answer
86 views

Loss of atmosphere on Mars

If the atmosphere on Mars was once much thicker, how was it likely lost? Was it due to interaction with the solar wind, the small size of the planet, both, or something else, and approximately how ...
12
votes
2answers
494 views

Why does a planet rotate and revolve?

Why do planets rotate and revolve in the universe?
12
votes
2answers
323 views

Will an observer falling into a black hole be able to witness any future events in the universe outside the black hole?

I know someone or something sucked into a black hole could not survive, but is the bending of light so immense that an observer falling into a black hole will be able to witness any future events in ...
12
votes
1answer
304 views

What is the object in this photo?

What object is in this photo? View coordinates: $47.25103 \ \ 38.81697$ Time: $2013$-$11$-$23 ~21$:$00 +4 ~UTC$ Sony $A580, \ 50mm f/1.4 15"$
12
votes
1answer
76 views

How can we detect water on Mars-like exoplanets?

According to data from Curiosity, Mars' dust holds about 2% water by weight This wasn't previously detected, so the impression we have had of Mars being incredibly dry may need to be altered. Okay it ...
12
votes
2answers
121 views

Relativistic effects in stellar dynamical systems

I am curious, if anybody knows of any stellar dynamical systems/environments, where relativistic effects could play a dynamical role on the motion of these stellar systems? As a subquestion - are ...
12
votes
1answer
409 views

Do we get any benefit from being in a galaxy?

If our solar system were to somehow be created outside of a galaxy as a single star in the vast nothingness between galaxies, would life on Earth change any? Does being a member of a galaxy actually ...
12
votes
1answer
107 views

How was Io not torn apart by tidal forces during its formation?

Jupiter's moon Io is arguably one of the most volcanically active bodies in the Solar System. The reason, according to NASA's page Scientists to Io: Your Volcanoes Are in the Wrong Place is believed ...
12
votes
1answer
290 views

Magnetic fields of peculiar HgMn A type stars

Do HgMn (peculiar A type) stars really possess global magnetic fields? See, for example, this paper by Hubrig et al. from 2012.
11
votes
7answers
1k views

Do we know the exact spot where big bang took place?

If you rewind the universe back 14,7 billion years, all matter were in one spot, and then started expanding. Do we know where this is in reference to our own solar system? And is there anything there? ...
11
votes
4answers
374 views

What is the most extreme weather found on another planet?

On Venus, there is really inhospitable weather, as well as within the gas giants in our solar system. Are there examples of even more extreme weather on planets found in other solar systems than ours?
11
votes
2answers
2k views

Is Earth unique in its fairly clear atmosphere?

So, we have surface pictures from two alien planets, Venus (captured by the Venera 13), and Mars (captured by the rover). Both of these pictures appear to be very dusty. For Venus we see strong ...
11
votes
4answers
229 views

What is the orbital path of the newly discovered star-less planet PSO J318.5-22?

Recent results from Institute for Astronomy at the University of Hawaii at Manoa claim that there is a Jupiter-sized gas giant planet that is independent of a star about 80 light-years from Earth. ...
11
votes
4answers
321 views

How would I measure that I'm at a pole?

How would a person measure that he is at a planetary pole? My first inclination is to use a sextant to ensure that the Sun remains at a constant inclination. However, due to the orbit around the Sun ...
11
votes
3answers
565 views

Why are orbits elliptical instead of circular?

Why do planets rotate around a star in a specific elliptical orbit with the star at one of it's foci? Why isn't the orbit a circle?
11
votes
4answers
1k views

How does Titan maintain the atmosphere

Titan which is smaller than mars has an atmosphere but mars is not able to maintain atmosphere. Even Luna doesn't have an atmosphere.
11
votes
1answer
213 views

Why Jupiter's Great Red Spot is Reddish?

The Great Red Spot is a persistent anticyclonic storm, 22° south of Jupiter's equator, but why is it reddish? From Wikipedia: It is not known exactly what causes the Great Red Spot's reddish ...
11
votes
1answer
317 views

If we count Avogadro's Number of stars that are closest to Earth, how big that space would be?

I posted this as a question to Scientific Imagination (Area 51 proposal) a while ago. And it was suggested that this question "is perfectly acceptable on Astronomy SE", since "it's about stellar ...
11
votes
2answers
259 views

What is the evidence that galaxies rotate?

Do all galaxies rotate? If so, do they rotate in the same direction? What observations have been made of galaxy rotation?
11
votes
4answers
10k views

What is the difference between our time and space time?

I am trying to understand the phenomenon of space-time. But, everything on internet seems to be too complicated for me since I do not have a background in physics. Can anyone give me simple ...
11
votes
2answers
2k views

Could the 9th planet be virtual?

Astronomers recently claim that there is evidence for a 9th planet. As far as I understood it, this is mainly based on coinciding orbital parameters of a few Kuiper belt objects. Could the 9th planet ...
11
votes
3answers
624 views

How old is our Sun in Galactic years?

A year is measured as the amount of time it takes Earth to orbit the Sun once, a Galactic year is the time it takes our sun to make one full orbit of the center of the Galaxy. In Galactic years, how ...
11
votes
3answers
560 views

Is it possible to measure galactic red shift using consumer telescope equipment?

I was wondering if it would be possible to measure red shift from distant galaxies using consumer grade telescope equipment and spectroscopy filters. (like this one) I imagine it would require a ...
11
votes
3answers
415 views

Calculate Distance To Stars

I was just watching a lecture from Carl Sagan. He talked about figuring out the distance to the stars; it got me interested in learning more about the subject. As far as I know, the Inverse square ...
11
votes
3answers
3k views

Jupiter FM - What are practical and inexpensive ways for the amateur detection of signals from Jupiter, especially of the transit of her moons?

What modifications to a standard AM/FM or shortwave radio are needed in order to be able to detect radio-wave signals emitted from Jupiter? Would it be possible to detect the transit of the major ...
11
votes
2answers
165 views

Conventional matter to dark matter ratio, outside of galaxies (Bounty!)

I'm pleased to offer a bounty to attract more attention to the fantastic Astronomy site. Consider say this outstanding diagram from another question, To begin with galaxies have a typical ...
11
votes
3answers
252 views

Metallicity of Celestial Objects: Why “Metal = Non-metal”?

Metallicity of objects refers to the amount of chemical elements present in it other than Hydrogen and Helium. Note: The other elements may or may not be actual ...
11
votes
2answers
298 views

Hypothetical beyond Neptune far away planets orbiting the Sun

The planet HD 106906 b was found at 650 AU from its home star, which is not a star much different from the Sun. Fomalhaut b is also a young planet that is orbiting very far away from its sun. These ...
11
votes
3answers
130 views

Frequency of gravitational wave detection

You may have heard in the news that the LIGO experiment recently detected a gravitational wave. Though I'm not an astronomer, the paper is a good read and mostly accessible. The detection of the ...
11
votes
2answers
582 views

Is it possible to break apart a neutron star?

I was inspired by this question on Physics, as well as this question right here on Astronomy. Neutron stars are tightly bound together as neutron degenerate matter. They're very massive and have a ...
11
votes
1answer
255 views

How did scientists determine an estimate of the number of planets greater than Sedna's size to exist in the Inner Oort Cloud?

In the article, New Dwarf Planet Found at Solar System's Edge, Hints at Possible Faraway 'Planet X' (Wall, 2014) where they report on research and observations performed by astronomers that discovered ...
11
votes
3answers
898 views

How can the 13.8 billion years old universe have a radius of 46 billion light years?

The universe is about 13.8 billion years old. Assume at the big-bang it starts from a small region and the maximum possible speed according Einstein is the speed of light how can the universe got a ...
11
votes
1answer
275 views

Parking a telescope at a Lagrange point: is this a good idea from a debris point of view?

The James Webb space telescope is supposed to be located at the Earth-Sun L2 Lagrange point. Do we expect the region around that point to have a higher concentration of space debris, asteroids, dust,...
11
votes
3answers
819 views

Is there any point on earth where the moon stays below the horizon for an extended period of time?

When I was teaching a class why the earth has seasons today, I mentioned how the poles of the earth experience months of daylight and darkness. Then one of my students asked whether the moon ...
11
votes
1answer
2k views

Is there any telescope on Earth that can see the lunar rovers on the moon?

If I have the right numbers, it seems to me that even Hubble telescope might barely be able to make out a carcass of a blue whale on the surface of the moon, which puts objects as small as the lunar ...
11
votes
1answer
9k views

How many sun-like stars are there in the universe?

After yesterday's announcement of the Kepler telescope finding a huge amount of newly observed exoplanets, i saw a headline claiming that as much as 22% of sun like stars in the universe have planets ...
11
votes
1answer
427 views

How Does a Refractor Telescope Work?

As I understand it, the difference between a reflector and a refractor is that a reflector uses mirrors on the back to reflect the light to the secondary mirror then the secondary mirror reflects the ...
11
votes
2answers
626 views

What Causes the Large Radiation Fields Around Jupiter?

I had heard that the large radiation belts around Jupiter may be formed by liquid metallic hydrogen in (or around) Jupiter's core (which Wikipedia says haven't been observed in labs yet due to the ...

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