What is the Hubble’s Law Why is it significant?
Because the exact value of the Hubble constant, H, is so important in extragalactic astronomy and cosmology – it leads to an estimate of the age of the universe, helps test theories of Dark Matter and Dark Energy, and much more – a great deal of effort has gone into working it out. …
Why is Hubble’s law so important quizlet?
Why are Hubble’s Law and the Hubble constant important? More distant galaxies move away from us faster with a very simple formula (velocity = Ho x distance). … Applies to all distant galaxies for which we can measure redshift, most useful technique for determining distances to galaxies that are very far away.
What are two properties of a Cepheid variable?
A Cepheid variable (/ˈsɛfiːɪd, ˈsiːfiːɪd/) is a type of star that pulsates radially, varying in both diameter and temperature and producing changes in brightness with a well-defined stable period and amplitude.
What is the most accurate way to determine the distance to a nearby galaxy?
Astronomers can use what are called surface brightness fluctuations (SBF, for short), along with the color of a galaxy, to calculate how far away it is from earth. Most galaxies measured in this way are millions of light years away.
What can we learn from Hubble’s law?
Hubble’s law, which says simply that a galaxy’s velocity (or as is sometimes plotted, its redshift) is directly proportional to its distance, also tells us something important about the state of the universe.
What is Hubble’s law formula?
Hubble’s Law – One of the most important formulas of the 20th century. … Formula: v = Ho d where: v = velocity of a galaxy, in km/s. Ho = Hubble Constant, measured in km/s/Mpc.
How is Hubble’s constant calculated?
The Hubble Constant can be stated as a simple mathematical expression, Ho = v/d, where v is the galaxy’s radial outward velocity (in other words, motion along our line-of-sight), d is the galaxy’s distance from earth, and Ho is the current value of the Hubble Constant.
Why do we call dark matter dark quizlet?
Why do we call dark matter “dark”? It emits no radiation that we have been able to detect. … The flat rotation curves of spiral galaxies tell us that they contain a lot of dark matter.
Which types of galaxies have a clearly defined disk component?
Lenticular galaxies are like a cross between spirals and ellipticals and are also disc-shaped. Ellipticals are like big eggs or spheres, and irregular galaxies are unclear blobs.
What is the difference between Type 1 and Type 2 Cepheids?
There are actually two classes of Cepheid: Type I Cepheids (δ Cepheus is a classical Cepheid) are population I stars with high metallicities, and pulsation periods generally less than 10 days. Type II Cepheids (W Virginis stars), are low-metallicity, population II stars with pulsation periods between 10 and 100 days.
Why do Cepheids pulsate?
Pulsating variable stars are intrinsic variables as their variation in brightness is due to a physical change within the star. In the case of pulsating variables this is due to the periodic expansion and contraction of the surface layers of the stars.
Is the sun a Cepheid variable?
Artist’s impression of the eclipsing binary system, including a pulsating star called a Cepheid variable. Our own sun is a variable star; its energy output varies by approximately 0.1 percent, or one-thousandth of its magnitude, over an 11-year solar cycle. …
How are star distances calculated?
Astronomers estimate the distance of nearby objects in space by using a method called stellar parallax, or trigonometric parallax. Simply put, they measure a star’s apparent movement against the background of more distant stars as Earth revolves around the sun.
What is the difference between brightness and luminosity?
When I say apparent brightness, I mean how bright the star appears to a detector here on Earth. The luminosity of a star, on the other hand, is the amount of light it emits from its surface. The difference between luminosity and apparent brightness depends on distance.