Stars/X-rays/Quiz - Wikiversity

X-ray stars is a lecture in the X-ray astronomy of stars. It is part of the X-ray astronomy/Course.

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1 Quiz
2 Hypotheses
3 See also
4 External links

Quiz

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1 Which of the following is not a characteristic of the diffuse X-ray background?

	a higher intensity than the CMB
	isotropic X-ray flux
	a wide range of energies
	a general increase in intensity from the Galactic plane to the poles
	a thermal emission at the lowest energies

2 True or False, Whenever "X-ray" is used in a sentence where the context refers to X-radiation, the "X" is always supposed to be capitalized.

	TRUE
	FALSE

3 Which of the following are X-radiation astronomy phenomena associated with stellar surface fusion?

	luminosities below ~3 x 10³⁸ erg/s
	a few SSS with luminosities ≥10³⁹ erg/s
	synchrotron radiation
	a photosphere
	a polar diameter that exceeds ever so slightly the equatorial diameter at solar cycle minimum
	super soft X-rays
	hot active regions with temperatures hot enough to fuse hydrogen
	sunspots at the feet of coronal loops

4 True or False, To emit X-rays a source must have some small amount of plasma near or above 10⁶ K.

	TRUE
	FALSE

5 Intragalactic super soft X-ray sources may be heavily reddened by

6 Yes or No, Only a plasma may be luminous.

	Yes
	No

7 Which of the following are X-radiation astronomy phenomena associated with the Sun?

	a core which emits neutrinos
	a solar wind which emanates out the polar coronal holes
	gravity
	the barycenter for the solar system
	polar coronal holes
	coronal clouds
	its position
	temperatures at or above 1 MK

8 True or False, Any object forming on a dynamical timescale, by gravitational instability, may be a star.

	TRUE
	FALSE

9 Complete the text:

Both

and

powered cataclysmic

have been observed to be X-ray sources.

10 Yes or No, X-rays span approximately three decades in wavelength, frequency, and energy.

	Yes
	No

11 The darker regions in X-rays at the North and South poles of the Sun are coronal holes, where the magnetic field lines are

12 True or False, All gaseous bodies may be a star.

	TRUE
	FALSE

13 Complete the text:

Most

and

originate in magnetically

around visible

groupings.

14 True or False, An O class star is not hot enough on the surface of its photosphere to emit X-rays.

	TRUE
	FALSE

15 The population of coronal loops can be directly linked with the

16 True or False, Super soft X-ray sources are in most cases only detected below 0.5 keV.

	TRUE
	FALSE

17 Which of the following are theoretical X-ray astronomy phenomena associated with astrophysics?

	a thermal plasma mechanism
	idea of a close binary
	synchrotron radiation
	high-density wind extinction
	a polar diameter that exceeds ever so slightly the equatorial diameter at solar cycle minimum
	super soft X-rays
	hot active regions with temperatures hot enough to fuse hydrogen
	sunspots at the feet of coronal loops

18 True or False, Coronal loops project into the coronal cloud, through the transition region and the chromosphere.

	TRUE
	FALSE

19 Active regions are the result of enhanced

20 Complete the text:

X-ray emission dividing lines may be explained by changes in a

field

to that of an

topology, leading to a decrease of magnetically confined

21 Phenomena associated with nanoflares?

	10¹⁷ Joules
	very high X-ray emission from happening every 20 s
	flickerings
	brightenings
	mass eruptions
	active regions

22 True or False, The photosphere of a star may be the result of omnidirectional incoming electrons.

	TRUE
	FALSE

23 About one third of ejecta observed by satellites at Earth is composed of

24 True or False, The Ca XV emission line is a yellow coronal line at 569.4 nm.

	TRUE
	FALSE

25 Which stars of the alpha Centauri system are known to have stellar active regions?

	Proxima Centauri
	Alpha Centauri B
	Barnard's star
	Alpha Centauri A
	Rigel Kent
	Alpha Centauri C
	Alpha Centauri D

26 True or False, "75% of the naked sunspots represented the return of large dominant f spots which had been part of large active regions during previous rotations."