Community Digest

Top new questions this week:

How else can a star form, other than gravitational collapse?

I read this paragraph on the Sun's page on Wikipedia: [The Sun] formed approximately 4.6 billion years ago from the gravitational collapse of matter within a region of a large molecular cloud. Most ...

star the-sun nebula  
asked by John 22 votes
answered by Daddy Kropotkin 14 votes

What is the most accurate measurement of the Astronomical Unit?

I am using the Earth-Sun distance to teach kids the usefulness of trigonometry. This site is helpful. But one of the more engaged asked what the most accurate measurement is. After some research, I ...

astronomical-unit education  
asked by aquagremlin 16 votes
answered by David Hammen 41 votes

How do Lagrange points L2 and L3 form?

Five Lagrange points form between any two bodies in the space (say Sun and Earth). According to my understanding, Lagrange points L1, L4 and L5 can form because gravitation pull can cancel out here as ...

asked by barath 13 votes
answered by David Hammen 22 votes

In an isolated binary system, can the expansion of the universe balance out collapsing orbit due to gravitational waves?

We know that binary systems slowly lose energy due to gravitational waves from the objects moving through spacetime and that if the objects are compact and massive enough, the mergers happen in time ...

expansion gravitational-waves binary  
asked by Justin Tackett 8 votes
answered by benrg 8 votes

Could Planet X have a perihelion much closer than 300 AU and still be responsible for the gravitational interaction with 19 TNOs?

In August, Michael Brown and Konstantin Batigyn proposed new data concerning the hypothetical Planet X to explain the orbits of the 19 TNOs. They suggest a perihelion of 300 AU, but might Planet X be ...

orbital-elements trans-neptunian-object hypothetical  
asked by LoveForChrist 8 votes
answered by ProfRob 13 votes

Minimum size of closed universe that satisfies ΩK < 0.005

According to this Wikipedia article: Results of the Planck mission released in 2015 show the cosmological curvature parameter, ΩK, to be 0.000±0....

asked by JeffB 5 votes
answered by benrg 4 votes

Procedures to test an hypothesis

In the context of planet formation and with the intention of testing different migration and in situ formation scenarios, I'm wondering what are the standard procedures to test and rank different ...

asked by holahola 4 votes
answered by AtmosphericPrisonEscape 5 votes

Greatest hits from previous weeks:

Why does it take so long to transmit an image from New Horizons to Earth?

I just got the news that the New Horizons space probe has passed by some remote planet on the edge of the solar system. I was surprised that the guy from NASA says that it might take 24 months from ...

solar-system data-analysis nasa  
asked by S. Kohn 50 votes
answered by astrosnapper 69 votes

Do all planets have a molten core?

As we know, according to Wikipedia on Earth's inner core: The Earth's inner core is the Earth's innermost part and according to seismological studies, it is primarily a solid ball with a radius of ...

planet core  
asked by Austin Phillips 10 votes

What are the differences between matter, dark matter and antimatter?

I thought dark and anti matter were kinda the same, but after saw a video, they mention that dark matter is not antimatter but their explanation is a little fast so I got doubts. What are the ...

dark-matter matter antimatter  
asked by Alex Sifuentes 17 votes
answered by Florin Andrei 13 votes

Does the Milky Way move through space?

Does our galaxy moves through space? Or does it stay in a single location? If it does move, what causes it to move?

galaxy universe milky-way  
asked by Mike 64 votes
answered by John Duffield 79 votes

moonless night and lunar phase

How to define moonless night? There is no moon at all during some night? How to calculate and know whether the moon would appear during one night? If the lunar phase is full moon, is it possible ...

asked by questionhang 6 votes
answered by dotancohen 9 votes

What would happen if an ice cube is left in space?

Recently I boarded a flight and noticed outside air temperature as -53°C at an altitude of 36860ft (11.23km). I don't know what causes such a freezing temperature in that altitude but was wondering ...

space temperature water  
asked by Praveen Kadambari 52 votes
answered by Mark 88 votes

Does the moon have days?

As like Earth, does the moon have a day (24 hours). If it has, how many hours are in a moon day?.

time the-moon  
asked by RANSARA009 18 votes
answered by CipherBot 21 votes

Can you answer these questions?

Has SETI searched the solar system for life?

I know SETI is searching the stars for radio signals emitted by advanced alien civilizations, but has SETI searched inside our solar system - particularly moons, planets, and Lagrange points? I would ...

solar-system radio-astronomy life extra-terrestrial seti  
asked by Jonathan 2 votes

Stromgren photometric data in Vizier

Is there a catalog in Vizier that provides Stromgren photometric data for stars, (the all four uvby, not just the indices b-y, m and c) I would like to try the photometric transform given in my book, ...

photometry resource-request  
asked by Cheng 2 votes

Estimate upper limits on flux values in the case of a non-detection?

I have ALMA data which are non-detections of some spectral lines in a protoplanetary disk. The data is in the form of spectral cubes. I am hoping to estimate an upper limit on the flux of each of the ...

radio-astronomy spectroscopy interferometry proto-planetary-disk  
asked by lucas 2 votes
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