Q&A Hero

Astronomy & Astrophysic

Q: Interstellar gas is composed mainly of A) only hydrogen. B) 90% hydrogen, 9% helium by weight. C) 10% hydrogen, 90% helium by numbers of atoms. D) some hydrogen, but mainly carbon dioxide. E) ammonia, methane, and water vapor.
Q: Compared to an open cluster, a globular cluster will have more hot, blue stars.
Q: A star cluster with a lot of hot, blue stars must be relatively young.
Q: Globular clusters contain mostly blue stars.
Q: Young open clusters contain a lot of hot, young blue-white stars.
Q: Globular clusters are typically much older than open clusters.
Q: In stage 3 of star formation, the cloud has collapsed enough that its inner regions are opaque to their own radiation.
Q: Stars evolve along the main sequence.
Q: For bright stars to form, the protostars must condense in dense, dark nebulae.
Q: 21-cm radio waves are emitted by all molecular hydrogen.
Q: Dark dust clouds are cooler than their surroundings.
Q: The 21-cm line of hydrogen is strongly absorbed by interstellar dust.
Q: 21-cm radiation is a result of an electron in hydrogen flipping its spin direction.
Q: Dark nebulae are opaque to all wavelengths of electromagnetic radiation.
Q: Conditions inside the darkest, densest nebulae are best studied with radio emission from molecules.
Q: While ionized hydrogen glows bright red, neutral hydrogen is transparent visibly and best studied with 21-cm radio waves.
Q: Molecular clouds are much warmer than typical interstellar gas clouds.
Q: Dark dust clouds are optically invisible, but give off radio energy.
Q: We usually find dark molecular clouds beside bright emission nebulae.
Q: Most molecules found in the interstellar medium are based on carbon.
Q: Emission nebulae get their red color from the red supergiants forming in them.
Q: O and B type stars are usually found associated with emission nebulae.
Q: Emission nebulae are created by gas absorbing ultraviolet energy from the hot young stars within them, such as in the Orion Nebula.
Q: The predominant color of emission nebulae is blue.
Q: The dust particles have exactly the same chemical composition as the gases of the interstellar medium.
Q: The gas in the interstellar medium consists of mostly heavy elements.
Q: Interstellar matter is distributed very evenly throughout the galaxy.
Q: There is as much mass in the voids between the stars as in the stars themselves.
Q: Light from distant stars that must pass through dust arrives bluer than when it left its star.
Q: How much brighter will a 4th magnitude star appear than a 6th magnitude star? A) 6.25 times B) 2.0 times C) 2.5 times D) 16 times E) 8 times
Q: On a night when a human eye can see a fourth magnitude star, a 60mm telescope, with 100 the surface area as our pupil, would be able to just barely detect A) seventh magnitude Titan, Saturn's largest moon. B) eighth magnitude Uranus. C) ninth magnitude Barnard's Star. D) eleventh magnitude Tethys, Saturn's second largest moon. E) thirteenth magnitude Pluto.
Q: Rigel has an apparent magnitude of + 0.18 and Betelgeuse an apparent magnitude of +0.45. What can you conclude from this? A) Rigel must be closer to Earth. B) Betelgeuse must be closer to Earth. C) Rigel is brighter than Betelgeuse. D) Betelgeuse is brighter than Rigel. E) Both stars are brighter than the full moon.
Q: A star's absolute magnitude is its apparent brightness as seen from A) Pluto. B) Alpha Centauri. C) 10 light-years distance. D) 10 parsecs distance. E) 100 parsecs distance.
Q: The full Moon's apparent magnitude is A) +4.83. B) +12.7. C) -1.4. D) -26.2. E) -12.5.
Q: The stars α Cygni and β Cygni are in the constellation Cygnus. Which statement is true?A) Cygni appears brighter.B) is hotter.C) must be the eastern most star in the constellation.D) Cygni appears brighter.E) appears redder.
Q: If Vega is apparent magnitude zero, and Deneb first magnitude, then A) Vega is about 100 brighter than Deneb. B) Deneb is one magnitude brighter than Vega. C) Vega is 2.5 brighter than Deneb. D) Deneb must be a main sequence star, and Vega a giant. E) Vega must be 2.5 hotter than Deneb.
Q: A star is 10 parsecs from Earth. Which statement is true? A) The star is about 33 ly away. B) The star is in a different galaxy. C) The star's apparent magnitude is smaller than its absolute magnitude. D) The star's apparent magnitude is larger than its absolute magnitude. E) The star's parallax is 1.0 arc seconds.
Q: A star has a parallax of 0.01 arc seconds. Its distance is A) 0.01 parsecs. B) 0.1 parsecs. C) 1 parsec. D) 10 parsecs E) 100 parsecs.
Q: If spectroscopic luminosity classification gives us an estimated distance to the faint star SAO 47552 of about 3300 light-years, then its parallax would be onlyA) 3.3.B) 0.1.C) 0.033.D) 0.01.E) 0.001.
Q: Which statement about stellar motion is incorrect? A) Radial velocity is measured by the Doppler shifts of the spectral lines. B) Proper motion is measured in intervals of six months. C) You must also know the parallax to get the transverse velocity. D) The closer stars usually show larger proper motions. E) The space velocity can be found from the radial and transverse velocities.
Q: The Hipparcos data give us A) information on only the 6,000 brightest stars. B) an accurate distance to the Moon. C) parallaxes as small as 0.005." D) distances to about 100 billion stars, practically everything in the Milky Way Galaxy. E) parallaxes to the nearest galaxies.
Q: A star has a parallax of .05." Its distance is A) 5 light-years. B) 20 parsecs. C) 66 parsecs. D) 200 parsecs. E) 660 light-years.
Q: Our best stellar parallax measurements to date come from A) the Hipparcos satellite. B) ground based measurements taken six months apart. C) radio interferometry. D) the Keck telescope. E) observations made by astronauts.
Q: Almost all properties of other stars are described relative to our Sun.
Q: The mass of a newly formed star will determine its position on the main sequence.
Q: Most stars are single stars like our own.
Q: Deneb's estimated distance of 1400 light-years comes from spectroscopic parallax measurements.
Q: The pressure in the photosphere affects the width of spectral lines.
Q: A G2V star would be the same temperature as a G2Ib star, but much smaller and less luminous.
Q: The main sequence is luminosity class V.
Q: Luminosity class V stars are larger than class Ia stars.
Q: Spectroscopic parallax is more accurate than trigonometric parallax for nearby stars.
Q: Almost all stars on the main sequence range from 0.1 to 15 solar radii.
Q: Main sequence stars are fusing hydrogen into helium in their cores.
Q: Our Sun lies about the middle of the main sequence and the H-R diagram.
Q: Main sequence stars lie at the top right corner of the H-R diagram.
Q: The vast majority of stars near us would fall to the bottom right on the H-R diagram.
Q: Most naked-eye stars would fall to the top left on the H-R diagram.
Q: Almost all stars on the main sequence range from 1 to 10 solar luminosities.
Q: White dwarfs lie on the lower left portion of the H-R diagram.
Q: A star of the same diameter, but twice as hot as our Sun, must be 16 times more luminous.
Q: Molecular lines, such as TiO, are only found in very hot stars.
Q: Ionized helium lines are found in both type B and O stars.
Q: Hydrogen lines are weak in M class stars because they have much less of it than do A class stars.
Q: Only A type stars show hydrogen lines in their spectra.
Q: A unique characteristic of type O stars is ionized helium lines in its spectrum.
Q: Hydrogen lines are strongest in class A stars.
Q: A type B star is bluer than a type G star.
Q: A type B9 star is hotter than a type A0 star.
Q: At its brightest, Venus, at magnitude -4, is 100 times brighter than a 1st magnitude star.
Q: A 3rd magnitude star appears 2.5 times brighter than a 4th magnitude star.
Q: A +6.0 magnitude star is brighter than a +3.0 magnitude star.
Q: The Sun, at absolute magnitude +4.8, would be one of the brightest stars in the sky if seen from 32 light-years distance.
Q: Two stars have the same absolute magnitude, but one lies twice as far from Earth as the other. It will appear half as bright.
Q: Of all the stars in the sky, Barnard's star, the next closest beyond Alpha Centauri, appears to move the fastest.
Q: Our nearest stellar neighbor is a little less than 1 parsec away.
Q: To get the space velocity of a star in three dimensions, you need its proper motion, distance, and radial velocity.
Q: The parallactic angle is the total shift observed over a six-month interval.
Q: Combining a star's proper motion and its distance allows us to determine its transverse velocity.
Q: The Hipparcos satellite has extended our accurate parallax distance measurements to over 200 parsecs.
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