115 votes
Accepted

Why is it easier to escape the solar system than get to Mercury or the Sun?

Because the earth goes very fast around the sun. If you want to get to the sun, you need to slow down almost completely so that your speed relative to the sun becomes almost zero. If you don't slow ...
Speedphoenix's user avatar
  • 5,324
46 votes
Accepted

Do you need 0 km/s velocity to crash into the sun?

Wouldn't i inevitably spiral to sun surface even if i was faster than 0km/s ? No. On reasonable timescales, an orbit will have a fixed distance of closest approach, called "periapsis." (These ...
Erin Anne's user avatar
  • 11.3k
37 votes

Why is it easier to escape the solar system than get to Mercury or the Sun?

Changing orbits requires delta-v. To reach the Sun, you need to subtract delta-v such that your velocity relative to the Sun is near zero, which allows you to "fall straight down" into the ...
Nuclear Hoagie's user avatar
36 votes
Accepted

What would happen if a satellite took a direct hit from a coronal mass ejection (CME)?

We can look at what happened when this actually occurred. The geomagnetic storm of March 1989 was caused by a Coronal Mass Ejection. Here are just a few of the many effects on satellites. One ...
Organic Marble's user avatar
34 votes

Has any object launched from Earth gone into the Sun?

No, not yet. The Parker Solar Probe became the closest ever artificial object to the sun on October 29th, 2018, surpassing Helios 2 which held the record since 1975 [1]. No other human-made object ...
Polygnome's user avatar
  • 6,936
32 votes

Is it really ~648.69 km/s delta-v to "land" on the surface of the Sun?

Addressing is the sun's mass and other quantities known well enough for this to be absolutely accurate? Well, the key to this is the vis-viva equation in your question. It's not actually important ...
hobbs's user avatar
  • 947
31 votes
Accepted

How to check, if there is currently an increased solar activity?

Looks pretty darned quiet to me right now: You can find that here, along with other measures of space weather. By the way, cosmic rays and solar activity are two entirely different things. Cosmic ...
Mark Adler's user avatar
  • 58.2k
31 votes

What would happen if a satellite took a direct hit from a coronal mass ejection (CME)?

I spent a couple of years working in the Astrophysics and Space Physics Section of JPL. Working with the Space Physics folks taught me a lot about the solar wind and other space weather phenomena. ...
Tom Spilker's user avatar
  • 18.3k
28 votes
Accepted

Is this really an image of the sun, or an "artist's conception"?

You can find the image on Flickr. On August 31, 2012 a long filament of solar material that had been hovering in the sun's atmosphere, the corona, erupted out into space at 4:36 p.m. EDT. The ...
Hobbes's user avatar
  • 128k
28 votes
Accepted

Why does the ISS need thermal blankets if the Sun is hot?

As noted in another question, the ISS faces some pretty hot temps. Remember, the Sun heats radiantly. When you're sitting in that much radiant heat, without an atmosphere to dissipate it, you're going ...
Machavity's user avatar
  • 7,905
28 votes

Is it really ~648.69 km/s delta-v to "land" on the surface of the Sun?

The Vis-viva equation is $$ v = \sqrt{ GM \left(\frac{2}{r} - \frac{1}{a} \right) }, $$ The $GM$ product for the Sun is 1.327E+20 m^3/s^2. If 1 AU is 150E+09 meters, then when you are in a ...
uhoh's user avatar
  • 149k
25 votes
Accepted

Did any spacecraft ever use the Sun's gravity for acceleration?

It doesn't really work that way. We can use the Sun to change direction, but we need rocket thrust to increase speed with the msneuver. To begin with, the closest stars (apart from the Sun) are not ...
Oscar Lanzi's user avatar
  • 8,505
25 votes

Why is it easier to escape the solar system than get to Mercury or the Sun?

Escaping the solar system requires adding orbital velocity to the spacecraft. Similarly, getting closer in the solar system requires removing orbital velocity. It turns out Earth is more out of the ...
Phil Frost's user avatar
  • 1,033
23 votes

Is oxygen present in the sun?

The sun is not "burning" in the sense you are used to: there is no chemical reaction going on. Instead, there is a very high pressure in the core of a star (like our sun) due to the high mass that ...
DarkDust's user avatar
  • 12.5k
23 votes

Did any spacecraft ever use the Sun's gravity for acceleration?

The "gravitational" (slingshot) maneuvers space probes are performing are actually not so much about gravity. The gravity is method to "tie" temporarily these two bodies, but you could (purely ...
Martin's user avatar
  • 1,831
22 votes
Accepted

Could we possibly see the shadow offset from Parker Solar probe on Earth?

The closer an object to the source of light, the larger the shadow it casts. That's true if we're talking about a point source or at least a compact source of light and "shadow" refers to ...
uhoh's user avatar
  • 149k
19 votes

Do you need 0 km/s velocity to crash into the sun?

You need below 2866 m/s of orbital velocity at 1 AU to crash into the Sun. You technically don't need to slow down exactly to 0 m/s relative to the Sun in order to crash into it. Let's calculate the ...
Star Man's user avatar
  • 5,928
17 votes

Do you need 0 km/s velocity to crash into the sun?

And note that if you want to hit the sun the cheaper (but slow!) way to do it is to head out. 12.32km/sec will take you to infinity, at infinity a burn of 0m/sec will kill your orbital velocity and ...
Loren Pechtel's user avatar
16 votes

For an object in a geostationary orbit to have the same apparent diameter as the sun, how big would it have to be?

If something is twice as far away, it has to be twice as wide to have the same apparent size. If it's 10x farther away, it needs to be 10x bigger. The Sun is 4250 times farther away than GEO, so the ...
SE - stop firing the good guys's user avatar
15 votes
Accepted

Is it possible to reach the Sun without expending any fuel/reaction mass?

If you're already in a solar orbit, then yes. You can use a sail at an angle and send the reflections prograde. The result is to reduce your orbital energy and you spiral in. I recall it was a ...
BowlOfRed's user avatar
  • 6,882
15 votes

Icy Hot Astronauts

Common wisdom says that space is cold. I wouldn't go so far as to call that a misconception, but it's certainly a bit of a misunderstood fact. See, space is not cold in the way your fridge or a block ...
leftaroundabout's user avatar
14 votes

Why is it easier to escape the solar system than get to Mercury or the Sun?

Based on the calculations presented by @uhoh I generated a plot showing the necessary delta-V for a fly-by mission, i.e. entering into a Hohmann transfer with a far point intersecting the orbit of a ...
asdfex's user avatar
  • 15k
14 votes
Accepted

If JWST can look into 13 billion years past then why it cannot check sun formation which happened only 4.603 billion years ago?

The James Webb Space Telescope has the potential to observe things that occurred thirteen billion years ago, because those objects were at sufficient distance at that time that the light they emitted ...
notovny's user avatar
  • 5,439
13 votes

Is this really an image of the sun, or an "artist's conception"?

I'm posting these images as a supplement @Hobbes's accepted answer and @TildalWave's comments (which includes links to these images). I started reading some of those links. The gallery is a good ...
uhoh's user avatar
  • 149k
13 votes

Why does the ISS need thermal blankets if the Sun is hot?

Insulation can function in both ways, keeping heat on whichever side is desired. In space limiting the amount of thermal input from the sun is very valuable since that heat is easily acquired but hard ...
Saiboogu's user avatar
  • 6,427
13 votes

Did any spacecraft ever use the Sun's gravity for acceleration?

I think the question is based on a misconception about how gravity assists work. If you just let yourself get pulled to a distant object then continue out the other side, the same gravity that ...
Asteroids With Wings's user avatar
12 votes
Accepted

How strong is the Sun's gravity at the distance of Jupiter's orbit?

Acceleration due to gravity is given by $$ a = \frac{GM}{r^2} $$ where G is the universal gravitational constant, M is the mass of the central body and r is the distance between the bodies' centers. ...
pericynthion's user avatar
  • 10.1k
12 votes

Most distant photo of the sun?

Voyager 1 took an image of the sun on February 14, 1990 at a distance of 6 billion kilometers. The famous Pale Blue Dot was captured at the same time and is superimposed here as well as a narrow angle ...
called2voyage's user avatar
  • 23.7k
12 votes
Accepted

Which spacecraft will be the first for which the Sun would become the second brightest object in the sky?

As a reference, part of this question I answered at Astronomy.SE. The closest point at which the Sun would not be the brightest object in the sky is if we headed directly towards Sirius A, at a ...
PearsonArtPhoto's user avatar
  • 121k
12 votes

Is it really ~648.69 km/s delta-v to "land" on the surface of the Sun?

It's a "real number", a delta-v chart isn't really concerned with the realism of various missions. It's quite simply a table of velocity changes, how you would go about achieving these velocity ...
SE - stop firing the good guys's user avatar

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