The most famous of the eruptive variables are the

Info icon This preview shows pages 28–30. Sign up to view the full content.

The most famous of the eruptive variables are the ______________. Explanation: Novae (plural of nova). Nova literally means "new". A nova is an existing star that suddenly emits an outburst of light. In ancient times, these outbursts were believed to be the birth of a new star. Novae remain bright for only a few days or weeks and then gradually fade. A ______________ is a star which flares up to hundreds of millions of times its former brightness. Explanation: Supernova. In contrast to an ordinary nova which increases in luminosity a few thousands or tens of thousands of times, a supernova is much more spectacular. All supernovae rise to maximum light extremely quickly and then usually fade from telescopic visibility within a few months or years after their outburst. Vast clouds of gas and tiny solid particles can be found throughout regions of space and are referred to as "clouds" or interstellar ___________. Explanation: Dust. Tiny solid grains of this dust surrounded by gas are manifested in the following ways: dark nebulae; general obscuration; reddening of starlight; reflection of starlight; and polarization of starlight. The opaque clouds that are conspicuous on any photograph of the Milky Way consist of dense clouds of the solid grains of dust and produce the ________ _____________. Explanation: Dark Nebulae. These areas of gas and dust can extend over vast regions and absorb or scatter a considerable portion of the starlight passing through them. These dark nebulae greatly dim or completely obscure the light of stars behind them. Even where dark clouds are not apparent, some absorption of starlight occurs because of gas and dust causing a general ________________. : Obscuration. This occurs in areas where the distribution of the interstellar dust is spotty and is thinly scattered throughout. This kind of obscurance has interfered with the calculation of the distance of stars. The ______________ of starlight by interstellar dust not only shows that the stars are dimmed, but also provides a means of estimating the amount of obscuration they have suffered. Explanation: Reddening. It is possible to estimate the total amount by which a star is dimmed from the amount that it is reddened. The reddening of the light from a star increases its apparent color index and changes the calculation of the distance of the star. Interstellar dust has a very high ________________ power, much like that of snow. Explanation: Reflecting. Tiny interstellar grains actually absorb some of the starlight they intercept, but most of it is scattered. The scattered or reflected light illuminates the dust itself.
Image of page 28

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

Molecules of gas scatter light and ______________ it at the same time. Explanation: Polarize. Dust particles of interstellar space also polarize light, but not as much. To polarize light means to cause it to vibrate in a particular direction or path. A star ____________ is a congregation of stars that have a stronger gravitational attraction for each other than do stars of the general field.
Image of page 29
Image of page 30
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern