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Montano1993 [528]
3 years ago
6

What is the first step in the formation of a protostar?

Physics
1 answer:
Fittoniya [83]3 years ago
4 0

Star formation begins in relatively small molecular clouds called dense cores.[7] Each dense core is initially in balance between self-gravity, which tends to compress the object, and both gas pressure and magnetic pressure, which tend to inflate it. As the dense core accrues mass from its larger, surrounding cloud, self-gravity begins to overwhelm pressure, and collapse begins. Theoretical modeling of an idealized spherical cloud initially supported only by gas pressure indicates that the collapse process spreads from the inside toward the outside.[8] Spectroscopic observations of dense cores that do not yet contain stars indicate that contraction indeed occurs. So far, however, the predicted outward spread of the collapse region has not been observed.[9]

The gas that collapses toward the center of the dense core first builds up a low-mass protostar, and then a protoplanetary disk orbiting the object. As the collapse continues, an increasing amount of gas impacts the disk rather than the star, a consequence of angular momentum conservation. Exactly how material in the disk spirals inward onto the protostar is not yet understood, despite a great deal of theoretical effort. This problem is illustrative of the larger issue of accretion disk theory, which plays a role in much of astrophysics.

Regardless of the details, the outer surface of a protostar consists at least partially of shocked gas that has fallen from the inner edge of the disk. The surface is thus very different from the relatively quiescent photosphere of a pre-main sequence or main-sequence star. Within its deep interior, the protostar has lower temperature than an ordinary star. At its center, hydrogen is not yet undergoing nuclear fusion. Theory predicts, however, that the hydrogen isotope deuterium is undergoing fusion, creating helium-3. The heat from this fusion reaction tends to inflate the protostar, and thereby helps determine the size of the youngest observed pre-main-sequence stars.[11]

The energy generated from ordinary stars comes from the nuclear fusion occurring at their centers. Protostars also generate energy, but it comes from the radiation liberated at the shocks on its surface and on the surface of its surrounding disk. The radiation thus created most traverse the interstellar dust in the surrounding dense core. The dust absorbs all impinging photons and reradiates them at longer wavelengths. Consequently, a protostar is not detectable at optical wavelengths, and cannot be placed in the Hertzsprung-Russell diagram, unlike the more evolved pre-main-sequence stars.

The actual radiation emanating from a protostar is predicted to be in the infrared and millimeter regimes. Point-like sources of such long-wavelength radiation are commonly seen in regions that are obscured by molecular clouds. It is commonly believed that those conventionally labeled as Class 0 or Class I sources are protostars.[12][13] However, there is still no definitive evidence for this identification.

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True or False: Amplitude can increase or decrease wavelength
Marat540 [252]

Answer:

A. False, frequency can increase or decrease wavelength.

For example: a high frequency would mean there are shorter wavelengths that occur in a period. Meanwhile, a low frequency would indicate that the wavelengths are longer and in longer periods.

4 0
3 years ago
the three major scales used to measure earthquakes are Mercalli scale Richard scale and magnitude scale
iVinArrow [24]
 False; the three major scales used to measure earthquakes are the Mercalli Scale, the Richter Scale, and the Magnitude Scale. I hope this helps!
3 0
3 years ago
If a girl is standing still and holding a box, is she doing any work? Why or why not?
sukhopar [10]
I beleive she isnt doing any work due to holding the box motionless, you must be exerting a force in the direction of the box motion. If she is just standing there holding the box their isn't no work becuase no distance has been covered. work = force = distance.


7 0
3 years ago
Read 2 more answers
As a physics instructor hurries to the bus stop, her bus passes her, stops ahead, and begins loading passengers. She runs at 6.0
Alika [10]

velocity of the physics instructor with respect to bus

v = 6 m/s

acceleration of the bus is given as

a = 2 m/s^2

acceleration of instructor with respect to bus is given as

a = -2 m/s^2

now the maximum distance that instructor will move with respect to bus is given as

v_f^2 - v_i^2 = 2 a d

0 - 6^2 = 2(-2)(d)

-36 = - 4 d

d = 9 m

so the position of the instructor with respect to door is exceed by

\delta x = 9 - 6 = 3 m

so it will be moved maximum by 3 m distance

7 0
3 years ago
A human being can be electrocuted if a current as small as 51.0 ma passes near the heart. an electrician working with sweaty han
boyakko [2]

The fatal current is 51 mA = 0.051 Ampere.

The resistance is 2,050Ω .

Voltage = (current) x (resistance)

            =  (0.051 Ampere) x (2,050 Ω)  =  104.6 volts .

==================

This is what the arithmetic says IF the information in the question
is correct.

I don't know how true this is, and I certainly don't plan to test it,
but I have read that a current as small as  15 mA  through the
heart can be fatal, not  51 mA .

If 15 mA can do it, and the sweaty electrician's resistance is
really 2,050 Ω, then the fatal voltage could be as little as  31 volts !

The voltage at the wall-outlets in your house is  120 volts in the USA !
THAT's why you don't want to stick paper clips or a screwdriver into
outlets, and why you want to cover unused outlets with plastic plugs
if there are babies crawling around.
6 0
3 years ago
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